FACTORS AFFECTING THE CONCEPTION RATE IN DAIRY CATTLE IN INDIA
Dr Ajeet Kumar Singh,
Veterinary Surgeon,
Founder and director of Global Veterinary Clinic and Surgery Centre, Gorakhpur,UP
Introduction
Alongside parameters of milk performance, reproductive parameters are very important in terms of management and production profitability . Number of services per conception (SPC) is frequently used as an indicator of fertility and the optimum value is considered to range between 1.6 and1.8. Today, first service conception rate ranges from 40 to 44% , which makes SPC higher than optimal. The number of services per conception around 2 is still acceptable, but values exceeding 3 are indicative of considerable organizational and/or health problems with reproduction.
Improving fertility is a common goal for many dairy herds or livestock owners. Getting cows pregnant in a timely manner is important in maintaining a profitable dairy business. Reproductive performance in dairy cows has declined over the last 25 years in dairy cows, with an increased number of days open and decreased conception rates .Conception rates are influenced by a variety of factors. Management and environmental factors account for 96% of the variation in conception rates. Herd differences in nutrition, metabolic disorders, reproductive health, heat detection, insemination practices and climate can result in significant differences in conception rates.. The remaining 4% of variation in conception rates is due to genetic factors with 3% for the cow and 1% for the service bull . These small values indicate that improvement in conception rates due to genetic selection will occur at a relatively slow rate. Nonetheless, given the significant economic importance of getting cows pregnant, some selection for improved fertility may be justified in a herd’s genetic program. There are many factors that may affect the effectiveness of AI in field condition. Out of them semen characteristics are the major factors that influence conception rate in cattle. For increasing the conception rate, we have to take proper initiatives such as proper heat detection, supply of high quality semen, accurate record keeping, good husbandry practices, supply of proper nutrition, trained and skilled AI technicians in field level.
Despite the wide application and success of AI throughout the developed world, the success rate in India and other developing countries is still low owing to a number of technical, system related, financial and managerial problems.
1 Age-—
Studies shows ,Conception rates are 19.4% higher in 1st delivered cows than that of the older cows attained the 4th or more parities. Conception rate is generally lower in older cows. In a Virginia study, conception rate remained constant (50%) during the first 3 lactations .
2 Level of milk production—–
Conception rate decreased with the increase of milk production
3 Estrous/Heat detection—-
One factor that can result in poorly timed insemination and low conception rates is inaccurate estrous detection.
4 Timing of service——–
For maximum conception rate, cows should be bred at a time that will ensure that healthy, live sperm are present at the site of fertilization when the unfertilized egg arrives.
5 Thawing period——–
Frozen semen is essential to thaw before practicing AI. Semen should thaw at a temperature ranged between 37 to 40ºC at warm water
6 Heating of insemination devices—–
Sperms are more sensitive to temperature shock. Before pushing semen to heated animal it is necessary to maintain same temperature of semen as like the temperature in female reproductive organs
7 Temperament of animal at AI—-
Temperament of animal during AI period is essential that directly related to conception rate of cows. Some animal remain docile and some are aggressive during AI period
8 Semen placement——-
Faulty insemination technique is a major factor causing low conception rate in many herds. Correct semen placement is critical.
9 Health disorder-—
Failure to provide a clean environment and (or) failure to practice good hygiene when examining and assisting cows at calving contributes to retained placentas and reproductive tract infections. These disorders slow the reproductive tract repair processes and can lower conception rates, especially if they do not receive timely and effective treatment. Calving and post-calving reproductive disorders seriously affect conception rates
10.Nutrition—
Before and after calving, has an effect on pregnancy rates. Inadequate nutrition prior to calving, results in cows being thin at calving which delays the onset of estrual activity post-calving. This delay in onset of cycling activity will influence the percent of cows available to be bred during the breeding season, thus reducing overall conception rates. The level of energy fed after calving will influence conception rates during the breeding season. The amount of energy fed will influence the percent of cows cycling, but even more dramatically influence first service and overall conception rates during the breeding season. The level of energy required by dairy females after calving is influenced by age, weight, and level of milk production. Cows on an inadequate plane of nutrition after calving can easily have first service and overall conception rates reduced by 5-10 percent and even more dramatic effects, such as a 20-40 percent reduction in conception rates have been noted in research trials.
11.Post-partum Interval to First Estrus —
It generally takes from 30-100 days for cows to cycle following calving. With the level of nutrition and age of the animal having a major influence on the return to estrus. As previously indicated, nutrition prior to calving or even nutrition after calving will influence the post-partum interval. First calf heifers will often require an additional 20-30 days to reach first estrus following calving. Long post-partum intervals can affect conception rates two ways: 1) lack of estrual activity prevents any chance of conception occurring, 2) cows will be bred on their first post-partum estrus which often slightly reduces conception rate.
12.Time of Calving —
One of the factors that influences the percent of cows cycling at the start of the breeding season or conception rates early in the breeding season, is when the cow calved relative to the start of the breeding season. If a long calving season is practiced, it is conceivable that some of the cows may not even have calved by the start of the breeding season.
13.Age of the Female
The age of the female can influence first service and overall conception rates. It has been documented in research studies that first service and overall conception rates may tend to be higher in yearling heifers than in cows, provided the heifers have reached puberty and are cycling. Heifers do not have the added stress or production trauma of nursing a calf.
14.Calving Difficulty
With increased emphasis on growth rate, unfortunately, the selection of sires that can transmit genetic growth through their progeny also causes a fairly dramatic increase in the birth weight of their calves and, subsequently, an increase in calving difficulty
15.Sire Influence
Utilizing sires that have been properly evaluated prior to the breeding season is important to ensure that a high conception rate occurs during the breeding season. In a study conducted in Oklahoma, it was shown that the variation in first service conception rate of herd sires ranged from 0-75 percent with overall conception rates during the breeding season ranging from 0-100 percent
16.Season of Year and Environmental
Affects Extensive records on dairy cattle have shown that season of the year influences conception rates. This environmental influence on conception rate is probably exerted through both the female and male. For example, during extremely hot weather in the southern states, it has been documented that there can be an 8-10 percent drop in first service conception rate and overall conception rate during extremely hot periods. In contrast, it has also been documented that extremely cold weather can influence conception rate and particularly the fertility of dairy sires
17.Level of Milk Production and Breed
A major effect of increased milk production is an increase in the nutritional requirement of those cows. If this added nutritional requirement is not met, the cows will lose weight, thus reducing the percent of cows cycling early in the breeding season and conceiving early. It is often implied that increased level of milk production is associated with poorer conception rates. Actually, the effect of milk production is probably mainly due to the suckling stimulus affecting post-partum intervals by reducing early conception. Claims are often made that some breeds of cattle are considerably more fertile than others. The greatest variation will occur within a breed rather than between breeds. Certain breeds of cattle will definitely adapt better to certain types of environmental conditions and topograpy and, as such, have a higher conception rate under those type of conditions. This improved conception rate will generally relate back to the condition of the animal and the ability to survive more efficiently under the nutritional regime being provided them. Probably the greatest influence of breed on conception rates is the fact that crossbred females will tend to have a higher conception rate and overall fertility by as much as 5-8 percent than straightbred females.
18.Genetic and Anatomical Abnormalities
Clinical evaluation of virgin yearling heifers has indicated that from 5-10 percent of the heifers may have infantile reproductive tracts preventing normal conception rates. Other genetic or anatomical abnormalities can occur in females thus reducing the potential for normal conception. Among certain sire female lines, there is a definite linkage between reproductive tract abnormalities and the genetic influence of the sire. Thus, if a fairly high incidence of abnormalities occur, an attempt to trace them back to the sire will be advantageous.
19.Health
Often one of the key factors reducing conception rates in a cow herd are health problems. A number of reproductive diseases can have a major impact on the overall reproductive performance of a cow herd. Two fairly common diseases, vibriosis and trichomoniasis, will cause lower conception rates. Cows will breed, but then return to heat fairly soon afterwards. Two other diseases that can impact conception rates are red-nose (IBR) and bovine viral diarrhea (BVD). A number of diseases will cause abortion to occur and leave the animals infertile. This would include diseases such as leptospirosis, hemopholaus somnus and brucellosis.
20.Forage or Plant Toxin
The most commonly noticed effect of plant toxins on cattle health is illness or, on occasion, death. It has been documented that certain plants, notably clovers, will contain high levels of estrogens which can influence the conception rate and fertility in cattle and sheep. In these studies the cattle and sheep will show abnormal estrous patterns and subsequent reduction in fertility.
PROBLEMS OF DECREASING FERTILITY IN DAIRY CATTLE IN INDIA & MITIGATION STRATEGIES
Reference- On request.
