PROBLEMS OF DECREASING FERTILITY IN DAIRY CATTLE IN INDIA & MITIGATION STRATEGIES

PROBLEMS OF DECREASING FERTILITY IN DAIRY CATTLE IN INDIA & MITIGATION STRATEGIES

Dr.Dinesh Mahto, SMS, KVK,Jahanabad

Despite the considerable expansion of our knowledge about the bovine reproductive cycle and the increasing possibilities to intervene herein, fertility in high yielding CB dairy herds in India has regularly been reported to decline since long.
Milk yields >4,000 kg/year are common in modern dairy production in India , owing to improved nutrition, management and genetic gains through use of progeny-tested bulls. However, reproductive performance has decreased worldwide in many cows with a high genetic potential for milk production, particularly in the Holstein & Jersey breed. Moreover, cow robustness and longevity is also threatened by increasing stress, udder health disturbances and of locomotion disorders. Genetic global misuse of a narrow base of AI sires -including those selected for high milk yield but not consequently for health and reproductive traits- has not only contributed to these undesirable effects on animal health and welfare but, together with sub-optimal management, jeopardized the ethical and economical sustainability of modern dairy farming.
India total cattle population is 192.49 million, out of which female cow population is 145.12 million (20th Livestock Census). It has increased about 0.83 % as compared to the 19th Livestock Census. So, the number of quality, high yielding cows is less and management of dairy cow fertility is now becoming a more critical part of a dairy farm. However, it is a real concern when farmers become so concerned about fertility that they resort to management decisions that affect their profitability. The stress of high milk production, along with increasing herd size and changes in facilities and management, has made fertility one of the main focuses of genetic improvement today. Because there is a positive correlation between milk yield and days open, the task of improving fertility while selecting for high milk production is challenging. Fertility of lactating dairy cattle has declined throughout much of the world in the last fifty years or so although accompanied by large increases in milk yield, the reduction in fertility has not been simply due to higher milk production. Indeed, estimates of the relationship between milk yield and fertility vary from negative to positive Fertility in cattle has many pre-requisites and components, which require males and females to be functionally capable of reaching the last step, the birth of a normal, vital calf, thus defining the general breeding goal: cows should return to normal cyclicity early postpartum, show strong and regular estrus signs, conceive after AI, carry their pregnancy to term, calve easily and give birth to viable and healthy calves. Low calving rates relate to the inability of the cow to resume ovarian activity and thus failure to cycle and to express estrous signs (anovulatory and behavioral anestrus, irregular estrous cyclicity, etc); as well as to reproductive wastage due to fertilization failure, early and late embryonic mortality, foetal mortality (abortions) and stillbirths. Fertilization rates (% of ova being fertilized), are generally high after AI under controlled conditions. However, decreasing rates are now seen in high producing cows. There are probably many causes why 10 – 25% of ova are not fertilized after AI, and they can be of either male or female origin.

Indicators of fertility

In the evaluation of reproduction it is important to differentiate between the concepts of reproductive performance, which is defined as the female’s ability to produce a live calf, and is affected by foetal development, calving and calf survival. Reproductive performance is calculated using various indicators such the number of days open (the interval between calving and successful AI) or the inter-calving periods. These two indicators are influenced by cow fertility as well as by other herd management factors, like heat detection and the length of the voluntary waiting period (interval between calving and time to first AI). For an adequate evaluation of bovine fertility, we need to refer to certain standards . Cow fertility is generally evaluated by the conception rate (CR), defined as the proportion of cows declared pregnant following AI. This indicator is inversely related with the number of AIs per conception. Artificial insemination centres use indicators calculated from available data. In general, they use the Non Return Rate (at day 56 or 60.) This corresponds to the proportion of AI without a second AI within a predetermined period. In the United States, bull fertility is evaluated using the ERCR (Estimated Relative Conception Rate). It may be interpreted as being the NRR at 70 days of the AIs performed using a bull in relation to that of the other bulls used for the same herd. In this case, factors such as the age of the cow, lactation stage and milk production are taken into consideration for the calculation.

Factors influencing fertility of cows:

1) Age of the cows – Analysis of fertility data demonstrates unequivocally that decreased fertility is associated with lactation number in cows. A study undertaken by Bouchard and DuTremblay (2003) between 1993 and 2002 on 60,000 cows/year from 2000 dairy farms shows no change in conception rate at first AI and second AI in heifers. However, an important decrease was observed in multiparous cows, including primiparous cows. The same trend was demonstrated in AI centres in Canada and the United States . Data collected from embryo transfers, even though they are performed under different conditions than regular AIs, show the same influence of age on cow fertility. An analysis of data collected from 2809 embryo harvests performed after insemination with semen from six of the most frequently used bulls shows that:1) the percentage of unfertilized ova in collections performed on primiparous cows is twice that of heifers; and 2) the percentages of unfertilized ova and degenerated embryos of the total embryo/ ova collected increases with the age of the cows.
2) 2) Production and nutrition- All reports have shown an association between an increase in milk production over the years and a decrease in fertility (Lucy, 2001.) The Quebec study of dairy herds shows that in comparison to cows whose production is less than 7500 kg, CR1 decreases by 7.8% in cows who produce 7500-10,000 kg at 305 days and by 15% in cows who produce more than 10,000 kg. Over a period of 10 years in the dairy herds studied, the average milk production increased from 6800 kg in 1990 to 8800 kg in 2001, while CR1 decreased from 44% to 39%. Nutrition influences the reproductive endocrinology of the cow. High proportions of degradable protein in the diet, and lower feed intake (as a proportion of the body weight) are nutrition factors related to lower fertility.
Any deficiencies are difficult to separate from the animal’s production level: high-producing cows are very much susceptible to Negative Energy Balance (NEB) after calving at the very moment they should normally initiate a phase of reproductive cycling. In suckling and low-milk yield cows, this period is followed by a resumption of gonadotrophic and ovarian activity and, most often, normal fertility. High-producing dairy cows, however, have often extended periods of anovulatory anestrus, as a consequence of the inadequate hormonal balance that the catabolic NEB causes (low blood levels of LH, insulin and IGF-I), resulting in impaired follicle development, estrous signs, LH surge and ovulation. Moreover, high-producing cows in NEB experience a delayed onset of postpartum ovarian activity and reduced Progesterone levels, which is caused by a lack of ovarian luteinized tissue or a higher rate of metabolism of the hormone by increased feed intake.

3) Primary, non-infectious, causes for reproductive failure in high-producing dairy cattle -High producing cows with hormonal imbalances have shorter estrous cycles and depict fewer estrus signs than expected (Figure 1), owing to sub-optimal estradiol levels. Hormonal imbalances, as well as genetic factors are related to cystic ovarian disease in high milk yield cows. Oocyte quality, built upon a total maturation time in the ovary of around 3 months, is very sensitive to negative influences such as nutritional deficiencies or over-conditioning. Accumulation of NEFA derived from the adipose tissue during NEB in the follicle fluid constrains the proliferation and health of the granulosa cells and thus jeopardizes oocyte development. Extension of the pre-ovulatory phase, i.e. delayed ovulation, due to suprabasal P4-levels causes ageing processes in the oocyte and compromises fertility, leading to repeat breeding by fertilization failure. After fertilization, an embryo is formed which develops in the oviduct during the first 3 – 4 days before it enters the uterus. The embryonic period lasts up to day 42 after fertilization and involves a series of critical periods, of which one comprises the first three weeks of development (“early embryonic death”), accounting for ~20% of the total losses. From this moment up to day 42, losses are termed “late embryonic death”. While fertilization failure and early embryonic death relate to a low genetic index of the female, up to 25% of late embryonic deaths have been seen in cows with genetic potential for a high milk yield but mainly related to milk yield rather than to their genetic index. Some of the early embryo losses might result from a malfunctional cytoplasm which impairs further development of the fertilized oocyte, a situation seen in over-conditioned repeat breeders. Cytokines can adversely affect uterine function and indirectly cause early embryonic death in relation to mastitis during early lactation.

3) Influence of artificial control of the estrus cycle – The increasingly common use of protocols for the hormonal control of estrus has so far produced varying results, ranging from negative effects (Donovan et al., 2003; Morel et al., 1991), to no effect (Xu et al., 1998) to positive effects on dairy cow fertility (McIntosh et al., 1984). However, researchers have noted that fertility in these cases is not affected when inseminations are made upon observed estrus. Fixed-time insemination without prior estrus detection is an approach that has gained in popularity, but it is generally recognized that it can result in decreased conception rates at first AI (Lucy, 2001). According to one study, the use of prostaglandins (with or without a synchronization protocol) for estrus induction is associated with a decrease of approximately 3% conception rates.
5) Progesterone concentrations – Circulating concentrations of progesterone are higher in nulliparous heifers as compared to lactating cows . In part, this physiological difference reflects increased post-prandial metabolism of progesterone by the liver . The reduction in circulating progesterone concentrations is likely to be one cause of reduced fertility in lactating dairy cows. Cows with higher progesterone concentrations after insemination have been reported to be more fertile .
6) Decrease in fertility due to disease -Studies have shown that disease, whether or not it is associated with the reproductive system, has a greater impact on fertility than milk production . Data analysis has shown that metritis, dystocia, lameness, mastitis, and retained placenta all have a negative effect on conception rate, decreasing it at respective rates of: 8.0%, 6.0%, 4.3%, 2.8% and 2.5% respectively .

OTHER FACTORS INFLUENCING FERTILITY —
7 Heat detection
8.Moment of insemination, insemination technique and sperm quality

9. Housing

Strategies to ensure good fertility in high producing dairy cattle with pros and cons————

As already mentioned, infertility in dairy cattle is multifaceted problem; therefore it requires a multidisciplinary approach. However, not all solutions intended for amelioration of the problem are longlasting, feasible or acceptable. Some measures can be applied rather immediately while others require further research and long-term strategies. Emphasis is needed on the relation between management and genetic gains, considering that many of the current problems with dairy cow fertility are a logical consequence of the low profit margins of the dairy sector, which impinges for high milk yields. With a global trend of strict cost controls, increased herd sizes, and changing farming systems, there is an unfortunate association with shortages of skilled labour and less time to look for physiological signals in the herd, the basis for good management. Moreover, we should recognize our limited ability to prevent and treat diseases, to appropriately manage, feed and select dairy cows with desirable reproductive traits.

1) Manipulation of the estrous cycle through management of floor and staff———————

From a veterinary medicine perspective, manipulation of the estrous cycle and the control of ovulation appear as a good short-term strategy. Application of methods to control the development of follicle growth, the promotion of ovulation in anoestrus cows, the regression of the corpus luteum in cyclic cows and the synchronization of estrus and ovulation at the end of treatment, before AI (on spontaneous or expected estrus) or mating should be thoroughly studied. However, we should try to detect natural heat in cows in normal cycle and natural mating should be preferred if possible. Well designed cow barns, with good width and slip resistance of the flooring of passageways and holding areas support best animal well-being and allow for efficient health management, including reproduction, by promoting expression of behavioural estrus, and providing the best opportunities for estrus detection by the staff. However, detection of estrus or of health problems (e.g. lameness) is often constrained by the shortage of skilled and experienced personnel to spend enough time with the animals.

2)Transition management (fresh cow care)– ———————

Use of diets designed to improve fertility by counteracting specific points in relation to NEB has always been an attractive way to avoid the impairment of reproduction during early lactation. However, the cow is biologically driven to mobilize body fat when she is fatter than her biological target condition, which makes this strategy difficult. Several ways have been attempted to reduce the effect of NEB, namely
1) Body Condition Scoring (BCS) of cows should be 3.5-3.75 at calving, to avoid the limiting negative feedback effect of body fat on the cow´s DMI, but high-quality diets should be available for “thinner” cows.
2) The feeding of low-protein diets that reduce body-fat mobilization by provoked imbalance in the protein-to-energy ratio.
3) The change of carbohydrate source in the diet to increase dietary energy concentration (increasing starch or fat and decreasing forage content, a risky procedure because of its implications on rumen function, milk composition, nutrient partition and metabolic hormones.
4) The inhibition of milk fat synthesis with exogenous conjugated linoleic acid (CLA), thus limiting energy output in milk. Changes in diet composition can elicit large changes in insulin levels, since plasma insulin concentrations are positively related to dietary starch concentration. Therefore, attempts have been made to use exogenous propylene glycol or hyperinsulinemic diets with the purpose of “fooling” the cow into a virtual anabolic condition, increasing glucose and insulin concentrations in circulating blood. Combinations of these designed diets are obviously more attractive, because they have proven to increase pregnancy rates dramatically (from 27 to 60%), implying that cows producing ~10,000 kg would have a fertility comparable to cows producing ~6,000 kg, by increasing insulin status immediately postpartum, and then reducing insulin status during the mating period.

3)Managing dry period – —————-

Shortening or eliminating the dry period has been postulated as a suitable way to quickly enhance fertility in dairy cows. This management can increase dry matter intake during the transition period, decrease milk energy output, or both. By increasing the energy status of dairy cows, there is an indirect increase in reproductive efficiency. However, such practice does not apply in general as it may have negative effects on udder health and total milk yield, and should be considered on a herd to herd basis. For involution of udder and mammary glands, minimum 60 days dry period must be provided to especially to high producing cows.

4) Extended lactation and differential milking————-
Most veterinary attention in dairy cattle is required from one week before to 10 weeks after calving
(important transition period), confirming that calving is a welfare risk. Moreover, it is important to avoid the impact of NEB on the resumption of reproductive function. For these reasons, voluntarily delaying the 1st postpartum AI, and attempting to have the cow calving at a calving interval of may be 18 months or so, leads to (a) the cow prolonging its lactation (socalled “persistent” lactation), (b) no need to look for estrus during the milk peak at early lactation, and (c) with AI done later during lactation, the cow having a better chance of getting pregnant. Increasing milking frequency by the use voluntary milking (using robotics) promotes extended lactation, but leads to a delay in the appearance of ovulatory estrus. Moreover, using extended calving intervals means fewer calves are born per cow, persistent lactation can lead to udder health problems in cows with high somatic counts and milk production can only be reasonably maintained by compensatory feeding during the declining phase. To be economically acceptable for the farmer, the milk yield has to be maintained over time and thus requires proper management. An alternative strategy is to flatten the peak of the milk curve by employing once daily milking in early lactation (but risking udder problem). Such practice promotes earlier resumption of ovarian cyclicity by increasing nutritional status, avoiding the impact of NEB and, further, the cow can maintain BCS throughout lactation.

5)Use of high fertility Bulls ————————–
Use of AI with semen from sires with proven high-fertility is probably the most obvious and simple recommendation. However, in order to prolong the term of this strategy from short to medium, the
breeding selection must be appropriate, i.e., including fertility traits with a certain weight in order to warrant that the improvement of reproductive performance is selected while still maintaining enough yearly increase in milk yield, thus warranting the profitability of dairy production in a longer perspective.

6) Crossbreeding —————————
Use of semen from other breeds where the decline in fertility is not a severe problem is also a medium term alternative to decrease fertility deterioration, although it might not be the best long term strategy. This strategy may also be used to combat inbreeding in herds where the problem is large. In particular, the development of multiple lines with similar capacity for milk production is attractive, based on the assumption that crossbreeding could be used to exploit benefits of heterosis. However, we should always bear in mind that cross-breeding is not per se genetic improvement and that genetic selection is still needed within the breeds used.

Factors Affecting Breeding Efficiency

The factors which influence the breeding efficiency of cattle are as follows:

1. Number of ova

The first limitation on the breeding efficiency of fertility of an animal is the number of functional ova released during each cycle of ovulation. Ovulation is the process of shedding of ovum from the Graffian follicle. In the case of cow, usually a single ovum is capable of undergoing fertilization only for a period of 5-10 hours. Therefore, the time of mating insemination in relation to ovulation is important for effective fertilization.

2. Percentage of fertilization

The second limitation is fertilization of ova. Failure to be fertilized may result from several causes. The spermatozoa may be few or low in vitality. The service may be either too early or too late. so that the sperms and eggs do not meet at the right moment, to result in fertilization.

3. Embryonic death

From the time of fertilization till birth, embryonic mortality may occur due to a variety of reasons. Hormone deficiency or imbalance may cause failure of implantation of fertilized ova which die subsequently. Death may occur as a result of lethal genes for which the embryos are homozygous. Other causes may be accidents in development, over-crowding in the uterus, insufficient nutrition or infections in tile uterus.

4. Age of first pregnancy

Breeding efficiency may be lowered seriously by increasing the age of first breeding. Females bred at a lower age are likely to appear stunted during the first lactation, but their mature size is affected little by their having been bred early.

5. Frequency of pregnancy

The breeding efficiency can be greatly enhanced by lowering the interval between successive pregnancies. The wise general policy is to breed for the first time at an early age and to rebreed at almost the earliest opportunity after each pregnancy. In this way the lifetime efficiency is increased. Cows can be rebred in 9-12 weeks after parturition.

6. Longevity

The length of life of the parent is an important part of breeding efficiency, because the return over feed cost is greater in increased length of life. Also, it affects the possibility of improving the breed. The longer the life of the parents, the smaller the percentage of cows needed for replacement every year.

Management Practices to Improve Breeding Efficiency

Some of the management suggestions which will tend to improve breeding efficiency of cattle are listed below.

1. Keep accurate breeding records of dates of heat, service and parturition. Use records in predicting the dates of heat and observe the females carefully for heat.
2. Breed cows during near the end of mid heat or heat period.
3. Have females with abnormal discharges examined and treated by veterinarian.
4. Call a veterinarian to examine females not settled after three services.
5. Get the females checked for pregnancy at 45 days to 60 days after breeding.
6. Buy replacements only from healthy herds and test them before putting them in your herd.
7. Have the females give birth in isolation, preferably in a parturition room and clean up and sterilize the area once parturition is over.
8. Follow a programme of disease prevention, test and vaccination for diseases affecting reproduction and vaccinate the animals against such diseases.
9. Practice a general sanitation programme.
10. Supply adequate nutrition.
11. Employ the correct technique.
12. Provide suitable shelter management.
13. Detect silent or weak heat, by using a teaser bull.

Selection and Culling

Selection and culling are the two sides of the same coin. Selection is the process in which certain individuals in a population are included for becoming the parents of the next generation. Automatically some are excluded for the purpose which are culled. Natural selection has been going on since ages where animals which were stronger, which had better survivability and which were in more unison with the environment around them, found a better chance to reproduce.

Thus certain genes for certain characters got more chance to be selected to form individuals in the subsequent generations. Since domestication of cattle, man has been looking for superior phenotypes in traits useful to him and selecting such animals to form the parental generation. This is man made artificial selection. Now man has progressed one step further in making estimates of genotypes from the study of phenotypes and making use of that information (in artificial) selection.

A. Selection methods

There is only one way to select and that is to “keep the best and cull the poorest. The various selection methods are techniques for identifying or estimating the genetic values of individual candidates for selection. The procedure discussed here apply to selection for quantitative trails.

1. Performance testing

Performance test is a measure of the phenotypic value of the individual candidates for selection. Since the phenotypic value is determined by both genetic and environmental influences, the performance test is an estimate, not a measure of the genetic value. The occurrence of this estimate depends upon the heritability of the trait i.e. on the degree to which the genetic value is modified by the environmental influences.
Advantages
 Among simple procedures, the performance test is the most accurate.
 Environmental influences can be minimised by testing candidates for selection in the same pen or in similar environmental conditions.
 The measure is direct, not on a relative basis.
 All candidates for selection can be tested in contrast to progeny testing where only a parent can be tested.
 Generation intervals are usually short.
 Testing can usually be done on the farm under normal management conditions.
Disadvantages
 Accuracy become low when heretability is low.
 Phenotypes are not available for one sexor in sex limited traits such as milk yield.
 Traits which are not expressed until maturity may become expensive or difficult to manage by performance tests since most selection decisions must be made before maturity.

Performance tests should be the backbone of most selection programmes. Although much publicity has been given to other selection methods, it remains a fact that most of the progress in livestock improvement to date has been due to selection on the individual’s own phenotype i.e. performance test.
B. Pedegree selection
A pedegree is a record of an individual’s ancestors including its parents. This information is valuable because each individual possesses a sample half of the genes from each parent. If we can precisely know an individual’s phenotype, little is gained by considering pedegree in selection. Pedegree considerations are useful when we do not have sufficient accurate records of production of the individual. Also, it is useful in the early selection when the traits in question might not have expressed themselves. It is also useful for selection of males when the traits selected for are expressed only by the female such as milk production in dairy cattle.
Advantages
 It provides information when performance tests are not available for the candidates.
 It provides information to supplement performance test information.
 It allows selection to be completed at a young age. Pedegree records may be used to select animals for performance or progeny testing in multi-stage selection scheme.
 It allows selection of bulls can be selected on the milk records of their female relatives.
Disadvantages
 Accuracy, relative to alternative selection procedures is usually low.
 Too much emphasis on relatives, especially remote relatives, greatly reduces genetic progress.
 Progeny of favoured parents are often environmentally favoured.
 Relatives often make records under quite different environments, thus introducing non random bases into the selection system.
C. Progeny testing

In this method we evaluate the breeding value by a study of the expression of the trait in its offsprings. Individuality tells us what an animal seems to be, his pedegree tells us what he ought to be, but the performance of his progeny tells us what he is.

Progency testing is, of course, a two-stage selection system because some preliminary selection determines which animals first produce progeny followed by further culling of these which produce poor progeny.

Advantages of progney testing
a. High accuracy when many progeny are obtained.

Disadvantages progney testing
a. Long generation interval.
b. Requires high reproductive rate.
c. Low selection intensity.

D. Show ring selection

Selection on the basis of show ring performance has had considerable value in the past. Essentially this selection has been directed towards bringing the conformation of the animal to some ideal conformation.

This improvement has been based on two goals:
(i) improvement conformation, and
(ii) correlated response.

Improvement of conformation has economic value because a part of the sale price is determined by the conformation of the individual. The ideal type was chosen so that, in the opinion of the judges, the animal possessing this conformation was most likely to be a profitable producer. In other words, the judges were attempting to stress traits of conformation which are corrected with productive ability.

With the advent of record keeping it was found that direct selection for performance traits resulted in much faster progress than selection through correlated conformation traits. Also, when subjected to intensive study, many of the correlations between performance and show ring were found to be of non-genetic origin.

If the correlations are of genetic origin, direct selection for performance should improve conformation as well as the reverse situation. The show ring has been a good forum for discussion of what constitutes ideal type and good management and has produced dramatic changes in the conformation of some species.

This has resulted primarily from education of the breeders, however, for most animals which are presented in the ring are good and selection differential among these animals is usually so small as to produce little change.

Advantages of show ring selection

1. It enables breeders to exchange ideas and experience.
2. It allows comparisons among superior animals both within and between breeds.
3. It allows new breeders to make contact with established breeders.

Disadvantages of show ring selection

1. Emphasis is usually placed on traits of little economic importance.
2. Clever fitting and showmanship can mask defects of various kinds.
3. Differences between exhibited animals are usually small.
4. Conformation and production traits usually have low genetic correlations.

Choosing Traits for selection

1. Many factors enter into the choice of traits to be selected for. The following ones are the most important.
2. The goal of the selection programme
3. The habitability of the traits
4. The economic value of improvement in each trait.
5. The range in variation of each trait.
6. Correlation among the traits.
7. The cost of the selection programme.

a. Selection goals

Often the goal of the selection programme makes the choice of traits quite obvious. The breeder of the race horses must select for speed if he is to be successful and his choice of traits are limited to alternative ways to measure speed. Similarly, the breeder of dairy cattle generally sets out to breed cows with superior milk production characteristics. Thus, his choice of traits is specified by his selection goals.

b. Heritability

Heritability is defined to be the fraction of the superiority of parents which is, on the average, transmitted to their off-springs. To explain habitability in simpler words: Heritability tells us how much of the observable differences in the animal is caused by genes and how much by environment.

Heritability for the same characteristics may vary from one population to another and also may vary from one characteristic to another even ink the same population. The ability to recognise the breeding values or transmitting abilities of animals is closely associated with heritability. If the heritability is high for a trait, we can proceed straight way to adopt a system of mass selection of superior animals, with little attention to pedegree information, collateral relatives, progeny test or inbreeding and genetic improvement in that trait is low, genetic progress may be disappointing with mass selection and greater attention should be paid to pedegree records, family information and use of progeny tests.

c. Variability of the trait

Selection operates on the variability in expression of the trait uniform for a trait. there will be little selection response because any selected groups of parents will not be much better than those not selected. Some traits are much more valuable than others. thus the innate variation of the traits should be carefully considered in choosing traits for selection.

Variation can be increased by improving exotic types and sometimes this can result in new combination of genes which are superior to either parent type.

d. Correlated traits

Sometimes traits tend to be inherited together. These correlations may arise in several ways.
The traits may be of different measures of some underlying trait. For example. weight and height are both measures of body size. thus taller animals are usually heavier and these two traits are said to be correlated.
If the same genes produce response in several traits. those traits will be correlated. This condition is referred to as pleiotrophy.

Correlated responses are common. Selection for increased milk yield produces a correlated decrease in the per cent of fat in the milk of dairy cows. Thus. both direct and correlated responses result from selection and some correlated responses are positive while others negative.

Correlated response may be advantageously used in selection programme. For example feed efficiency is expensive to measure because it requires both weight gain and feed intake on each individual, whereas weight gain requires neither feed weight nor individual feeding.
In summary. definite goals are essential for a successful selection programme. The success in achieving these goals depends on the existence of genetic differences. the degree to which phenotype differences are heritable and the correlated responses in other traits. In comparing the selection programme, the breeder must evaluate the value of the expected response and the cost of the programme relative to the costs and responses of alternative selection programmes.

---

Systems of Breeding
The ultimate aim of the breeder is to evolve outstanding and improved type of animals which can render better service to man. Selection and system of breeding constitute the only tools available to the breeder for improvement of animals. Since new genes can not be created though they can be recombined into more desirable groupings.

Systems of breeding has been broadly divided as under

1. In breeding -breeding of the related animals.
2. Out breeding -breeding of the unrelated animals.
   A. lnbreeding
   Inbreeding is a mating system in which individuals mated are more closely related than the average of the population from which they come. It means the mating of males and females which are related. Animals deemed to be related only when they have one or more ancestors in common on the first 4-6 generations of their pedegree. The intensity of inbreeding depends upon the degree of relationship. Close inbreeding denotes mating of closely related individuals like dam to son (mother x son) or sire to daughter (father x daughter) or full brothers to full sisters.

In breeding makes more pairs of genes in the population homozygous. Wherever there is inbreeding, there will be one or more common ancestors from which, part of the gene samples (gametes) have arisen.

Inbreeding can again be divided into following groups:

Estrus Period
•
• ro estrus: 2 or 3 days
• Estrus: 12 to 18 hours
• Ovulation: 12 to 16 hours after the end of estrus
• Estrous cycle length: 21± 3 days

Puberty
•
• Puberty is the stage at which animal becomes sexually mature and secondary sex characteristics become conspicuous.
• The term sexual maturity means that the animal is capable of reproduction.
• Puberty is the age at which the first estrus occurs in the heifer and the bull starts giving semen with viable sperms.
• The reproductive organs undergo marked increase in size at the time of puberty.
• Under good feeding a calf attains puberty approximately at 66 per cent of adult body size.

Signs of estrus
•
• Cow in estrus will be the first cow to rise in the morning.
• The cow become restless does not eat and frequently bellows and seldom ruminates.
• Sudden drop in milk production.
• Searching for male.
• Traits of homosexuality is shown in which the cow will attempt to mount other cows while other females not in estrus tend to mount the estrus cow which she permits.
• The cow is receptive to the act of mating and will stand when the bull mounts her.
• The behaviour of standing quietly while being mounted by the bull or other cow is referred to as the ‘standing heat’ which is the surest sign of estrus.
• This extends for 14-16 hours and shows other symptom like bellowing, nervousness, anorexia, reduction in milk yield.
• Mucous discharge may be found sticking to the tail.
• In early heat the discharge is watery and copious in mid heat (standing heat) it becomes thick and sticky and in late heat it will be scanty and discoloured.

Bulling
• The best indicator of oestrus is when any cow or heifer repeatedly stands and accepts mounting by one of her herd mates. Unfortunately, they do not do this on demand. Those responsible for oestrus detection must watch for this behaviour and combining what they see with their own previous knowledge/experience, to decide whether to inseminate or not.

Heat detection in buffaloes
•
• Cows do mount over other cows when they are likely to come in heat and stand for mounting when they are in good heat. This is not seen in buffaloes. Buffaloes neither mount on other buffaloes nor other buffaloes mount on buffaloes in heat.In buffaloes copious ropy hanging discharge is not seen on the contrary it gets suddenly dropped and is not noticed by the owner and the discharge is scanty.Some buffaloes do not bellow and show silent heat, especially high yielding buffaloes.
• The main heat symptoms of buffaloes are as follows.The vulva becomes edematous, swollen. The lower portion of vulva looks oily. The gap is seen between vulvar lips and slight opening is seen. The wrinkles which are present in anoestrus buffalo become shallow or vanish.
• The mucous membrane of vulva becomes reddish, moist and glossy.
• Mucus discharge which is not seen normally can be seen before or after oestrus spontaneously.
• The colour, consistency and fern pattern of mucus help in determination of correct oestrus.
• Engorgement of teats in lactating buffaloes which is due to holding of milk following increased estrogen level in blood is seen when they are in heat.
• Frequent urination. The urine coming in spurting action wetting the part of skin below vulva and above udder (perineum). The drying of the urine leaves white mark on skin.
• Buffaloes in heat remain restless, off feed, raising head in a typical fashion.
• Local non descript buffaloes bellow, become restless and remain off feed. Milk yield is reduced. The bellow is sharp and for longer duration.
• The buffaloes expose their teeth while bellowing which is very characteristic.
• The mucus discharge, in buffaloes is seen in about 49% cases. It is thin on the day of heat, become thick as the time passes and changes the colour from clear to white.
• 60-70 % of the buffalo come in heat from 6 pm to 6 am (after sunset and before sunrise) and this should be borne in mind and attendant should watch the buffaloes in the evening and early morning for expression of heat symptom.
• Teaser bull (Vasectomised bull), can be used for parading in buffalo barn for detection of heat

Other methods to detect estrus
•
• Crystallization pattern of cervical mucous will show long crystals in a typical fern-like pattern
• There are many estrus-detecting devices available. They are usually attached to the tail or rump of the cow.
• Mounting causes these devices to discharge a coloured fluid which can be observed afterwards even from the distance.
• ‘Chin ball mating device’ can be used for heat detection. It works on the same principles of a ball point pen and is fixed by means of a halter below the chain of the teaser bull. When the checking animal mount the cow in heat, the dye exuded round a spring-loaded ball of the device marking the back of the cow.
• Russian workers have developed an instrument basically consisting of an ohm meter and electrodes. When applied to the mucous membrane of the vagina, the resistance indicated on the ohm meter shows whether the cow is in heat.
• Pedometer is an instrument used to monitor the movement of animal. The principle is the activity and movement of the cow increases on the day of heat and this can be detected by means of a pedometer tide to the leg of the cow.
• The vaginal temperature can be recorded, which gives an indication about the heat. Generally during estrus, the vaginal temperature increased by about 1°Con the day of heat. Both methods are not very practicable.
• The methods described above had little applicability in developing countries due to technological and economical and managemental reasons. close observation of signs of heat, standing heat remains the most practicable method of heat detection.
• In large farm this can be supplemented with a bull-parade using a teaser bull. A teaser may be a vasectomised bull or bull in which penis has been amputated and the urethra exteriorized.
• An intact bull can also be used by hanging a thick cloth or gunny bag curtain in front of the penis preventing entry of penis and mating.
• Special care should be taken to prevent spread of disease by teasers. Vasectomised bull is more harmful in this regard.

Time of insemination
•
• Ovulation takes place about 12 hours after the end of estrus. It takes another six hours for it to travel half-way down the oviduct.
• The sperm, even though reach the oviduct within minutes after insemination, must be exposed to the female reproductive tract for about 6 hours to attain the capacity to fertilize.
• This process of preparing the sperm for fertilization is known as capacitation.
• Sperm are viable for 24 hours in the female reproductive tract whereas the ovum remains fertile for only about 10 hours after ovulation.
• This implies that mating or insemination between mid-estrus (middle of standing heat followed by another insemination in about 6 hours after that.
• As a routine practice, if a cow is seen showing signs of early heat in the morning, it may be inseminated in the evening.
• If such signs are first manifested in the evening, the cow may be bred next day morning.
• A cow is expected to show estrus in 30-40 days after calving. Cows that fail to show heat even after 50 days have generally some problem and need examination.
• It may be due to infection or malnutrition and remedial measures may be taken accordingly.
• Insemination should be done only when buffalo is in standing heat. In buffalo to understand standing heat one should know the symptoms of heat.
• Buffaloes normally are not seen standing for mounting by herd mates but standing heat can be known from the changing colour of mucus discharge which is early estrus is clear and watery but in standing heat or mid heat the colour is changed to little buffy with thick consistency.
• In mid heat the oedema of vulva is intense there is little gap in vulvar lips and lower lip looks oily.
• The vulvar mucus membrane is glossy reddish or pink and wet.

Signs of approaching parturition
•
• Cow will leave the herd and seek isolation.
• Loss of appetite and distress.
• Distention of teat and udder, considerable milk appears in the udder and there may be dripping of milk.
• Relaxation of pelvic ligament one day before calving, the ligament on the sides of the tail head is loosened so that hollows appear on either side of the backbone and the tail head is raised and the quarters are dropped.
• The vulva become enlarged and flabby
• Animal will be restless and will pace about often trying to kick or scratch the flank region.
• The parturition process has three stages a. preparatory stage (uterine contraction and dilatation of cervix) b. active expulsive stage c. expulsion of foetal membrane.
• Cow will deliver the calf within 12 hours after commencement of first stage and lapse in this vaginal examination of assistance by a veterinarian is required.
• Care must be taken to observe expulsion of placenta (after birth). It should be removed immediately so as to avoid cow eating it.

Package of practice to improve reproductive efficiency
•
• Accurate record kept is very important in ensuring reproductive efficiency I the herd.
• There production detail like date of estrus, date of service and calving should be maintained properly.
• This data should be used to predict the probable date of heat, such animal should be watched carefully in the morning and evening for signs of heat.
• In larger dairy farm teaser bulls can be put in use.
• Complete breeding history, past performance and difficulties of a individual cow should be maintained.
• Irregular estrus and abnormal discharge should be attended immediately.
• The cows with retained placenta should be treated promptly and when such cows are put in breeding next time, the reproductive tract should be examined thoroughly for involution and possibility of infection.
• A manager should examine a cow 24 to 36 hours after service for metestrus bleeding. If it occurs under 24 hours after service, the cows were bred too late.
• If it occurs over 36 hours after service, they were bred too early during estrus. This will help in pinpointing of failure of conception.
• Cow should be examined for pregnancy 45 to 60 days after service so that if they are non-pregnant, steps can be taken to re-breed them at the earliest opportunity.
• If the conception rate under A.I is lower than natural service, time of insemination, insemination technique and quality of semen must be checked.
• Short irregular cycles indicate cystic ovaries, short and long irregular interval point to missed head.
• Silent or quiescent heat : the behavioural manifestation of heat may be very weak or imperceptible in such case. It is very common in buffaloes. But there is a normal ovulation and if inseminated at proper time the animal can conceive.
• Cows go through the normal ovarian changes of the estrus cycle except the behavioral heat and sexual receptivity.
• It is more in summer season than other seasons and more in heifer than adult animals.
• Use of balanced feed, proper summer management, use of teaser bulls can be of use tool in detecting silent heat.
• Anestrus or absence of sexual cycle may be due to under developed genitalia or due to persistent CL. In the former case follicle fail to develop and a heifer will not come to heat at all.
• One of the major causes of under developed genitalia is malnutrition. Besides there can be genetic causes.
• The second probability is the anestrous also may be due to persistent CL, due to certain hormonal disturbances, the C L persist beyond the life expectancy in a normal cycle, thereby preventing further cycling. A common cause for persistent CL is endometritis of the uterus.
• Sometime anestrus is often observed in the early post partum period when the lactation is strong, probably due to the influence of lactation(due to secretion of prolactin) ‘e’lactational anoustnum

Care and management of young stock
•
• Normally newborn animals will be taken care by its mother and required little assistance.
• In case of cattle, sheep and goat immediately after birth the mucus around the nostrils should be whipped out using dry cloth or a hand full of straw can be used for this purpose.
• Calm environment should be provided to the mother and young animals for development of bond.
• The mother should be allowed to lick the newborn; if the dam fails to lick it can be stimulated by sprinkling small quantity of salt or bran over the young one.
• Immediately after birth the naval cord should be ligated with clean sterile cotton thread 1 inch from the body and tincture iodine should be applied to the naval cord.
• With in 1 hour after birth the newborn will able to stand and it should be allowed to drink adequate quantity of colostrum (first milk) which will give immunity to the newborn.
• Young animals should be housed comfortably. Adequate care should be taken to avoid housing young stock with adult stocks.
• In winter condition adequate warmth condition should be provided.
• Adequate bedding materials like straw or hay should be provided to newborn animals.
• For giving extra heat artificial light source can be utilized.
• Proper light, ventilation and hygiene should be maintained to avoid spread of disease.

Care and management of dry animals
• A dry animal means animal, which completes their lactation and drying is essential to give adequate rest to the udder of the animal.
• Dry animals should be separated from other milch animals.
• In case of cow, dry cow can be treated for mastitis to prevent mastitis in next lactation.

Care and management of pregnant animals
• Pregnant animals should be provided with extra ration to meet the requirement of fast growing foetus as well as store energy for future lactation.
• Pregnant animals should be separated in advanced stage from other non pregnant animals.
• They should be housed separately in place called calving pen.
• Adequate bedding materials should be provided in the pregnant animals shed.
• Floor of the pregnant animal shed should be non-slippery.
• Adequate clean fresh drinking water should also be provided in the calving pen.
• In advance stage of pregnancy laxative diet should be provided.

The nutrition and general management of dairy cows have both changed considerably in the past years. Changes have generally been made by trying to adapt the cow to nutrition and management without considering the long term consequences on the basic reproductive physiology of the animal. Since reproductive parameters have low heritability, the application of new reproductive techniques requires an adapted reproductive health program that deserves further exploration to prevent the Udecreasing fertility in cows

Reference-On request.