Abstract

The objective is to relate characteristics of ovarian follicles near ovulation and insemination with the rate of survival or death of embryos four to eight weeks later in dairy cows during high and low seasonal temperatures.

Issue

Impaired reproductive performance is one of two major causes of reduced productivity for dairy cattle. Despite recent advances in estrous synchronization, overall fertility in dairy herds has declined during the past ten years, both nationally and internationally. Recent survey data indicates that 12 percent of dairy cows are not pregnant 150 days after calving. Several field studies have raised concerns about large early pregnancy losses in lactating cows. By using ultrasound imaging of embryos between 25 to 32 days after artificial insemination (AI), pregnancy losses ranged from 14-40 percent before subsequent pregnancy diagnosis at 50 to 98 days.

The goal for this project is to improve dairy animal reproductive performance. By enhancing basic knowledge of the underlying biology, new nutritional strategies can be developed for management. Application of non-drug nutritional supplements is economical, user-friendly and preserves food quality and safety. The combination of innovative applied research with basic biology techniques supports outreach programs more effectively in order to achieve the goal more rapidly. Improved reproductive performance increases efficiency of milk production that is necessary to increase or maintain the global competitiveness of the U.S. agricultural dairy production system.

Response

Lactating dairy cows were treated during either July-September (high temperatures) or January-April (low temperatures) to synchronize ovulation and artificial insemination (OvSynch/TAI). The size of the largest ovarian follicle (presumptive ovulatory follicle) was measured on the day of AI by ultrasonographic exam of the ovaries. Pregnancy in lactating cows was associated with larger follicle diameter on the day of AI. Estradiol concentrations on day of AI were neither significantly different between pregnant and non-pregnant cows in either season, nor related to embryo losses. Pregnant cows had higher progesterone concentrations following AI compared to non-pregnant cows suggesting that a more rapid rate of post-ovulatory rise of progesterone improves embryo survival. Initial pregnancy rate in lactating cows was 33 percent and 23 percent of these embryos were lost by day 63. Follicle size at AI was similar in cows pregnant at day 63 compared to those losing the conceptus. Season did not affect follicle size in pregnant or pregnant cows losing the conceptus.

Impact

Follicle size at insemination following ovulation synchronization procedures is relatively uniform, but follicles were larger in cows becoming pregnant compared to non-pregnant cows. Follicle size seems unrelated to subsequent late embryo losses. Plasma estradiol concentrations before ovulation were not predictive of pregnancy status and embryo loss rate, but higher circulating progesterone from day 5 after insemination seems related to improved embryo survival. This new information provides a basis for further nutritional and hormonal studies directed at enhancing progesterone production after ovulation for improved embryo survival.

Funding Sources

• Private (e.g., commodity groups, foundations, companies)
• Federal Formula Funds - Research (e.g., Hatch, McIntire-Stennis, Animal Health)

Collaborators

• Multistate project NE-1007, "Ovarian and environmental influences on embryonic/fetal mortality in ruminants"
• Cornell University Veterinary Medicine

Key Personnel

• Dr. Robert Gilbert, CU Veterinary Medicine
• Ana S. Lopes, Danish Institute of Agricultural Sciences, Foulum, Denmark