Repeat-Breeder Females in Beef Cattle: Influences and Causes1

Abstract

Straightbred and crossbred heifers (165) and cows (241) that were nonpregnant after exposure to fertile bulls for two consecutive breeding periods of 45 to 60 d (repeat breeders) and contemporary cows (102) that had produced a calf in the previous calving season (controls) were placed with bulls and were observed for mating. Repeat-breeder and control females were slaughtered at 2 to 51 d postmating. Data were accumulated over 4 yr. From previous calving records, repeat breeders had more (P<.05) calving difficulty than controls. Percentages of females with anatomical aberrations or anovulation were 10.9 and 3.6, and 0 and 2.9, respectively, for repeatbreeder and control females. Repeat breeders had fewer (P<.01) normal embryos and higher (P<.01) nonreeovery rates of an embryo or oocyte than controls. Precentages of normal, degenerate, unfertilized, or nonrecoveries were 42.3, 8.9, 8.0 and 40.8, and 76.8, 9.1, 6.0 and 8.1 for repeat breeders and controls, respectively. Repeat breeders had fewer (P<.01) 1-to 3-ram follicles than controls (25.4 and 36.5, respectively). On d 6 postmating, controls had higher (P<.O1) serum progesterone concentrations than repeat-breeders (2.7 vs 1.8 ng/ml, respectively). Chromosome aberrations were found in lymphocytes of 19 of 133 (14.3%) repeat-breeders. Increased anatomical aberrations of the reproductive tract, increased anovulations, lower recovery rate of an oocyte or embryo, lower progesterone concentrations at d 6, fewer 1-to 3~mm follicles and increased chromosomal abnormatilities are possible causes for lower fertility in repeat-breeder females.

Identification of an ionotropic glutamate receptor AMPA1/GRIA1 polymorphism in crossbred beef cows differing in fertility12

“…This is in agreement with a report that low-fertility cows that had failed to produce a calf in either 1 or 2 previous seasons did not demonstrate a failure in ovulation (Warnick and Hansen, 2010). Because conception rates are relatively high in beef cows (Maurer and Chenault, 1983), this would suggest a greater rate of embryonic loss in repeat breeder cows, as has been reported previously (Maurer and Echternkamp, 1985;Warnick and Hansen, 2010). Thus, oocyte quality may be the connection between decreased follicle numbers and subfertility in heifers and cows.…”

“…In summary, the results from the present study confirm previous reports that the numbers of small antral follicles are decreased in the ovaries of repeat breeder cows (Maurer and Echternkamp, 1985). However, we were unable to identify an association of a polymorphism in the GRIA1 gene with follicle numbers in cows, in contrast to a previous report (Sugimoto et al, 2010).…”

“…In cows, reproductive aging is associated with decreased numbers of follicles in the ovary (Erickson, 1966;Malhi et al, 2005;) and decreased luteal function (Malhi et al, 2005;Echternkamp et al, 2009). Similar observations were reported for repeat breeder beef cows that failed to produce a calf in 2 consecutive years (Echternkamp and Maurer, 1983;Maurer and Echternkamp, 1985). These cows had fewer small antral follicles (1 to 3 mm) and decreased serum progesterone concentrations compared with contemporary herd mates at a similar age, suggesting an advanced state of reproductive aging.…”

“…However, repeat breeder cows had lower numbers of surface follicles (current study and Maurer and Echternkamp, 1985), ovaries that were smaller, and endometrial diameters that were decreased when compared with contemporary herd mates that always produced a calf. The lower number of antral follicles in repeat breeder cows continues to support the decreased fertility observed in low antral follicle count heifers and cows both in vivo (Cushman et al, 2 Height of the ovary contralateral to the corpus luteum.…”

Clinical Approach to the Repeat Breeder Cow Syndrome

“…The bull-cow interaction usually ranges from 45 to 90 days, although sometimes it lasts 6 months or it may also be permanent. Few reports on RBC exist in beef cattle (Maurer & Echternkamp, 1985;Ferreira et al, 2008).…”