Anogenital distance (AGD), defined as the distance from the center of the anus to the base of the clitoris, in lactating dairy cows of first and second parity, has been reported to be inversely related to fertility and moderately heritable. Thus, AGD may be a useful reproductive phenotype for future genetic selection to improve fertility. The objectives of this study were to (1) characterize AGD in nulliparous dairy heifers; and (2) determine if the inverse relationship between AGD and fertility, found in lactating dairy cows, is also evident in nulliparous heifers. We measured AGD in 1,692 Holstein heifers from 16 herds in Western Canada (Alberta and British Columbia) and one herd in the United States (Washington State). Data were analyzed using MEANS, UNIVARIATE, LOGISTIC, ROC, GLIMMIX, and LIFETEST procedures of SAS (SAS Institute Inc.). Mean (±standard deviation) age at AGD measurement was 13.9 ± 1.5 mo, and AGD was normally distributed with a mean of 107.3 ± 10.5 mm, ranging from 69 to 142 mm. With every 1-mm increase in AGD, the predicted probability of pregnancy was reduced by 1.9%. Receiver operating characteristic curve analysis was used to determine the optimum threshold AGD that predicted the probability of pregnancy. Based on the optimum threshold AGD, data from heifers were categorized into short (≤110 mm) and long (>110 mm) AGD groups, and associations between AGD groups and fertility measures were determined. Heifers with short AGD required fewer services per conception (1.5 vs. 1.7) than heifers with long AGD. Consequently, heifers with short AGD conceived earlier (448.4 vs. 454.3 d) and had greater pregnancy to first AI than those with long AGD (58.3 vs. 49.6%). Moreover, heifers with long AGD had reduced hazard (hazard ratio of 0.59) for pregnancy up to 450 d of life compared with those with short AGD. In summary, AGD was normally distributed and highly variable in the population. In addition, an inverse relationship between AGD and fertility measures in nulliparous heifers was evident, confirming an earlier report of a similar relationship in lactating dairy cows. These findings strengthen the potential for AGD to be used as a fertility trait and management tool in future selection programs.
Immunity plays important role in reproduction. There is evidence that maternal immunity changes from a type 1 to a type 2-biased during pregnancy and lack of such a shift may contribute to unsuccessful pregnancy in animals. The objective of the study was to examine the relationship between relative balance between type 1 and type 2 and fertility in suckled beef cows by characterizing relative quantity ratio of IgG 1 and 2 subclasses (IgG1/IgG2). Angus-Hereford cows (n = 394) were synchronized (d0) with a 5-d CIDR protocol. Estrous behavior was monitored using estrus detection aids and visual observation from d5 until AI (d8). On d8 all cows were inseminated at a fixed time and blood samples were collected form to be examined for type1/type/2 ratio and progesterone (P4). A new rapid blood test (D2Dx) was used to assess the type 1/type 2 immunity balance by measuring the relative quantity ratio of IgG1 and IgG2. Pregnancy was determined by ultrasound 48 to 63 days after AI. Overall pregnancy per AI was 51%. Mean relative quantity of IgG1/IgG2 was different (P < 0.05) between non-pregnant and pregnant cows. There was negative relationship between relative IgG/IgG2 ratio and probability of pregnancy to AI (P < 0.05). As IgG1/IgG2 ratio increased, probability of P/AI decreased. Mean relative IgG1/IgG2 ratio was lesser (P < 0.05) in cows detected in estrus vs non-estural cows. There was no correlation between serum P4 concentrations and IgG1/IgG2 ratio. The results indicate that blood IgG1/IgG2 at the time AI has a potential to be used as a marker for pregnancy prediction in beef cows.
Two injections of prostaglandin F2 (PGF) in a 5-d CO-Synch+CIDR timed-AI protocol (5-d CIDR) is necessary to induce luteolysis and reduce serum progesterone (P4) concentrations by the time of AI in beef cattle. The objectives were to examine the effects of a single high-concentration dose of PGF in a 5-d CIDR protocol on P4 concentration and pregnancy per AI (P/AI) beef cows. Angus-Hereford cows (n = 404) were synchronized (d0) with a 5-d CIDR protocol and assigned to receive either one injection of high-concentration PGF on d5 (HC; total dose: 25 mg; n = 203) or two injections of conventional PGF (2PG; each injection: 25 mg; n = 201), at CIDR removal (d5) and 8 h later. All cows received AI at a fixed time 72 h after PGF treatment (d8). Pregnancy was determined by ultrasound 48–63 days after AI. For P4 and cyclicity determination, blood samples were collected on d -7, 0, and 8. Cyclicity status and proportion of cows with a CL at d0 did not differ between treatments. Proportion of cows detected in estrus was greater (P = 0.01) for 2PG (63.1%) than HC (49.3%). Treatment did not affect P/AI (P = 0.87; 51% vs. 52% for HC and 2PG, respectively). Serum P4 at AI also affected (P < 0.01) P/AI; as P4 concentration increased, P/AI decreased. ROC analysis showed a greater P/ AI when P4 was < 0.43 ng/mL. Fewer (P < 0.01) HC cows had P4 < 0.43 ng/mL at AI than 2PG (84.0 and 97.0%, respectively). Nonetheless, mean P4 concentrations at AI were less than 0.4 ng/mL for HC and 2PG. Although two doses of conventional PGF (total dose: 50 mg) more effectively reduced P4 to < 0.43 ng/mL by the time of AI than one dose of high-concentration PGF (total dose: 25 mg), P/AI was not different between treatments.
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