STRATEGIES TO BE ADOPTED TO INCREASE CONCEPTION RATE IN DAIRY ANIMALS
Conception rate is the number of services given to a defined group of cows or heifers, over a specific period of time which results in a diagnosed pregnancy not less than 42 days after service. This is expressed as a percentage of the total number of all services and should include culled cows. The simple solution to boosting dairy cattle conception rates (CR) is to improve reproductive management and cow environment, as these two general categories account for 96 percent of CR variation. More specifically, nutrition (e.g., energy and mineral balance and feed molds and mycotoxins), animal health (e.g., metabolic disorders and reproductive system soundness), reproductive practices (e.g., heat detection and insemination practices) and data management influence most of the reproduction puzzle.
What else influences CR? Genetics, with 3 percent attributed to the cow and 1 percent to the service bull.
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Factor affecting the conception rate:
Dry period
Cows with short dry periods (30 to 40 days) experience an earlier first ovulation and improved fertility at first and second insemination. Excessively long dry periods (beyond 100 day) may lead to poorer reproductive performance. As the dry period lengthens, cow fertility decreases in the next reproductive cycle.
Close-up period
During the close-up period, strive to maximize dry matter intake by feeding a balanced ration with nutrients, such as calcium, at the proper dietary cation-anion difference, along with proven feed ingredients that include essential fatty acids. Feed the close-up ration for a minimum of 14 days.
Calving
To enhance transition period and future CR success, provide cows with a clean and dry calving area with minimal stress. Inferior conditions and calving assistance may lead to dystocia, retained placenta, metritis or endometritis. Researchers showed cows with dystocia and clinical endometritis were 67 and 55 percent, respectively, more likely to lose their pregnancies during the first 60 days of gestation compared with healthy cows.
Post-calving
Metabolic disorders influence CR. To help cows experiencing subclinical ketosis, consider giving them oral propylene glycol. A study found this protocol reduced the development of a displaced abomasum. Cows were less likely to be removed from the herd during the first 30 days in milk and more likely to conceive to the first service.
Estrus synchronization
It probably goes without saying but, as a friendly reminder, strict compliance with injection and hormonal management protocol is crucial for carrying out a successful synchronization program. Variations from protocol explain the outcomes of timed-A.I. programs. Poorer-than-expected performance is almost always attributed to compliance issues at the farm level.
Insemination
Just like milking procedures, evaluate individuals’ heat detection, semen handling and breeding techniques on a regular basis. Check for compliance with established procedures. Similarly, follow industry guidelines for proper semen handling, semen thawing and cleaning breeding implements. While speediness is often admired, don’t let speed get in the way of effectively getting cows bred.
Mastitis
While fertility and udder health may seem like vastly different health challenges, research continues to show a strong correlation. Researchers estimated the cost of each incident of clinical mastitis occurring in the first 30 days of lactation at $444. Part of this amount considers the negative effects of mastitis on overall reproductive performance.
The presence of endotoxins produced by the mastitis pathogen induces the release of chemical neurotransmitters and hormones responsible for local responses, such as redness, swelling, pain and function loss. These mediators and hormones can affect reproductive performance and pregnancy loss. Researchers found the time when clinical mastitis occurs can extend days open from 85 days in an uninfected cow to 106 days if the infection occurs before first service and up to 143 days if the infection occurs between first service and pregnancy diagnosis. A significant CR reduction also occurs. A study demonstrated the occurrence of mastitis is associated with a prolonged interval to first postpartum A.I.
States evaluation
Evaluating reproductive performance encompasses several factors, so avoid just looking at a single performance measure or statistic. Monitor several factors, such as CR, pregnancy risk, days in close-up pen, calving difficulty, days dry and heat interval. These measurements provide valuable information that can be used to find opportunities to improve procedures and protocols that influence outcomes.
High-risk cow list
Establish fresh cow protocols, including procedures for cows that didn’t have a textbook lactation or dry period (e.g., extended days in milk, too short/long dry period, calving difficulty). Giving a little extra attention to high-risk cows will help prevent challenges in the next lactation. Daily, use your dairy software to print a high-risk fresh cow list and proactively manage these cows. For example, give propylene glycol, if appropriate, to prevent the effects of subclinical ketosis. Work with your herd veterinarian and nutritionist to develop management protocols.
Taking advantage of farm information can be an excellent strategy to proactively work with specific cows, if all information is accurate and gathered correctly. Regular CR evaluation by heat interval and cows with high somatic cell count offers an excellent opportunity to reduce the negative effects of these health challenges on CR. To improve CR, reduce culling rates and lower the incidence of metabolic disorders, develop a proactive fresh cow protocol for cows in the high-risk group.
Strategies to improve the Conception rate in bovine
- Improvement of conception rate at and after Al
The challenge to improve the reproductive performance of lactating dairy cattle requires an understanding of the biochemical and physiological principles controlling reproduction and lactation. This needs to be integrated into nutritional, production and reproduction management systems to optimise the fertility of the herd. Pharmacological attempts to improve fertility in inseminated cattle have concentrated on three areas so far:
– Timely induction of ovulation, prevention of early embryonic loss through increasing progesterone concentrations in the general circulation or prevention of precocious luteolysis
– Minimising the reproductive effects of heat stress
- 2. Prevention of delayed ovulation– Used to ensure timely ovulation in relation to service
One of the methods of obtaining satisfactory conception rates is to ensure that ovulation occurs within 7-18 hours of Al. One possible method is by the administration of GnRH around the time of service. Depending on the size and maturity of the dominant follicle, preovulatory LH surge and ovulation usually occur within 24 hours of GnRH injection, which is similar to the time between the onset of oestrus and ovulation. It is postulated that the administration of GnRH analogues at the time of insemination may modify the function or characteristics of pre-ovulatory ovarian follicles and the secretory capacity of the developing corpus luteum. GnRH may have served to enhance or alter theca-lutein or granulosa-lutein differentiation in the pre-or post-ovulatory follicle, or developing corpus luteum, and may have acted on the developing corpus luteum to promote the conversion of small to large luteal cells, thereby increasing the progesterone secretion.
- Support of luteal function and prevention of precocious luteolysis
Several attempts have been made in high-yielding cows to prevent early embryonic loss, especially in those exposed to heat stress, and embryo transfer recipients. Several methods have been tried to increase conception rates by increasing plasma progesterone concentrations during the luteal phase. This can be achieved by inducing the formation of accessory corpora lutea, which can be obtained by hCG treatment for an of 4-6 days after insemination. Apart from the initiation of additional corpora lutea, this treatment is believed to provide further LH support to the corpus luteum verum, which results from the ovulation of the dominant follicle.
3.1 Prevention of precocious luteolysis
A number of recent studies have been devoted to the analysis of the effect of GnRH treatment in mid-cycle (usually 11-14 days post insemination) on embryo survival and the resulting pregnancy rate. GnRH treatment aims at enhancing embryo survival by suppressing the luteolytic mechanism that ensues if there is no maternal recognition of pregnancy. Depending on the stage of follicular development, treatment with GnRH analogues during the luteal phase causes luteinization or ovulation of the existing responsive luteal phase follicles, which continue to grow after the ovulation of the dominant follicle of the previous cycle.
- Strategies to decrease the negative impact of heat stress on reproduction in dairy cattle
Measures aimed at reducing the negative impact of heat stress on reproduction in dairy herds should always include reducing the exposure of cows to heat as well as any biotechnical or pharmaceutical approaches aimed directly at fertility improvement
The possible options include:
- Changes in production system
- Selection of heat resistant breeds (bos indicus and crosses)
- Embryo transfer
- Hormone therapy
- Administration of GnRH at the time of artificial insemination
The administration of GnRH during the early stages of oestrus is believed to induce an enhanced LH surge and to improve the synchronization of the intervals between oestrus, LH surge, ovulation and insemination. Moreover, induction of ovulation, with the administration of GnRH at oestrus, allows for a reduction in the incidence of delayed ovulation and prolonged follicular dominance associated with the effects of heat stress.
- Estrus detection accuracy
As accuracy of estrus detection increases the conception rate also increases.
- High stocking densities
High stocking densities in the breeding pen were also associated with reduced conception rates. So reducing stocking density will increase the conception rate.
- Voluntary waiting period
There has been found a positive relationship between length of the VWP and the first-service conception rate. Cows serviced before 50 days postpartum had a lower conception rate than those serviced after a longer postpartum period. So optimum voluntary waiting period will definitely increase the conception rate.
Anuj Kumar1, Sanjay Kumar Mishra2, Vikas Sachan1 and J.K. Agrawal4
1Assistant Professor, Department of Gynaecology & Obstetrics, DUVASU, Mathura, U.P.
2Veterinary Officer, Animal Husbandry Department, Uttar Pradesh
