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ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Nutrition and Environmental Management Research » Research » Publications at this Location » Publication #323697

Research Project: STRATEGIES TO IMPROVE HEIFER SELECTION AND HEIFER DEVELOPMENT

Location: Nutrition and Environmental Management Research

Title: Use of an electronic activity detection system to characterize estrus activity in crossbred beef heifers differing in follicle number

Author
item Cushman, Robert - Bob
item Tenley, Sarah - University Of Nebraska
item Soares, Emerson - Universidade Federal De Santa Maria
item Mcneel, Anthony
item Gomes, Renata - University Of Nebraska
item Tait Jr, Richard
item Cupp, Andrea - University Of Nebraska
item Kuehn, Larry
item Snelling, Warren
item Thallman, Richard - Mark
item Perry, George - South Dakota State University
item Chase, Chadwick - Chad

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 12/22/2015
Publication Date: 3/7/2016
Citation: Cushman, R.A., Tenley, S.C., Soares, E.M., McNeel, A.K., Gomes, R.S., Tait Jr, R.G., Cupp, A.S., Kuehn, L.A., Snelling, W.M., Thallman, R.M., Perry, G.A., Chase, C.C. 2016. Use of an electronic activity detection system to characterize estrus activity in crossbred beef heifers differing in follicle number [abstract]. Journal of Animal Science. 94(Supplement 2):152.

Interpretive Summary:

Technical Abstract: Increased numbers of antral follicles have been associated with decreased calving day, increased fertility, increased serum estradiol concentrations, increased serum progesterone concentrations, and increased estrus behavior in cattle. In addition, cows with increased fertility have been shown to have greater activity during behavioral estrus when using electronic activity detection systems. Therefore, the objective of the current study was to evaluate an electronic estrus detection system to determine if differences in estrous cycle characteristics could be detected among beef heifers differing in antral follicle number. The hypothesis was that the percent of heifers demonstrating behavioral estrus and peak activity would be decreased in heifers with low numbers of antral follicles. Estrus activity collars were placed on crossbred beef heifers (n = 359) at 12.0 ± 0.1 mo of age to monitor estrus activity, and heifers were submitted for ultrasonographic evaluation of antral follicle number at 13.5 ± 0.1 mo of age, immediately before the start of the breeding season. During a 21-d period, heifers were artificially inseminated 12 h after estrus was diagnosed by the electronic system. Following the period of artificial insemination, heifers were placed with bulls for an additional 42 d, and submitted for ultrasonographic pregnancy diagnosis 45 d after removal of the bulls. Heifers were classified as low (<16 follicles), medium (16-25 follicles) or high (>25 follicles). The percent of heifers demonstrating behavioral estrus was analyzed using the GLIMMIX procedure of SAS with antral follicle group as the fixed effect with a binomial distribution and a logit and link. Length of the estrous cycle before insemination and peak activity at insemination were analyzed using the MIXED procedure of SAS with antral follicle group as a fixed effect. The percent of heifers demonstrating behavioral estrus was lower in heifers with low numbers of antral follicles compared to heifers with medium or high numbers of follicles (P = 0.02; 46.2 ± 4.2 vs. 57.5 ± 2.4%). Peak activity and estrous cycle length; however, did not differ among antral follicle groups (P > 0.1). Combined with our histological and hormonal data, these results indicate that greater numbers of antral follicles contribute to increased behavioral estrus due to increased serum estradiol concentrations; however, this does not result in a difference in peak activity calculated by the electronic system during behavioral estrus.