Browsing Animal & Grassland Research & Innovation Programme by Funder "Alberta Milk"
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The relationship between anogenital distance and fertility, and genome-wide associations for anogenital distance in Irish Holstein-Friesian cowsThe evaluation of anogenital distance (AGD), the distance from the center of the anus to base of the clitoris, as a potential fertility trait for genetic selection in dairy cows has generated recent interest. The objectives of this cross-sectional observational study were to (1) characterize the distribution and variability of AGD, (2) determine factors associated with AGD, (3) estimate heritability for AGD, (4) identify single nucleotide polymorphisms (SNP) associated with phenotypic variation of AGD, and (5) validate the relationship between categories of AGD and fertility in Irish Holstein-Friesian cows. Anogenital distance was measured using digital calipers in 1,180 Holstein cows (mean ± standard deviation: 225 ± 79 d in milk) from 10 dairy herds located in Munster, Ireland. In addition, age (yr), weight (kg), height at hip (cm), and body condition score (BCS) at the time of AGD measurement were determined in a subset of 281 cows. Genotype information available from 908 cows was subsequently imputed to the Illumina Bovine High Density BeadChip (Illumina Inc., San Diego, CA) for genome-wide association analysis of phenotypic variation in AGD. Overall, AGD had a normal distribution and high variability (mean ± standard deviation; 119.2 ± 11.6 mm). Anogenital distance was weakly but positively associated with cow age, hip height, and body weight, and negatively associated with BCS; the phenotypic variation in AGD that was explainable by these variables was small (coefficient of determination; R2 = 0.09, 0.06, 0.10, and 0.02, respectively). The estimated heritability for AGD was 0.37 (standard error of mean ± 0.08). Six SNP of suggestive significance were identified on Bos taurus autosomes 6, 15, 20, and 26; however, none of these SNP was related to previously identified candidate genes for fertility. Cows were categorized into quartiles (Q1; 86 to 111 mm; n = 311, Q2; 112 to 120 mm; n = 330; Q3; 121 to 127 mm; n = 265, and Q4; 128 to 160 mm; n = 274) based on AGD and the association with reproductive outcomes examined (21-d submission rate, pregnancy to first AI, pregnancy rate within 21, 42 and 84-d after the farm mating start date, and number of times bred). None of the reproductive variables differed significantly between AGD categories. In summary, despite identification of high variability and moderate heritability for AGD in Irish Holstein-Friesian cows, reproductive outcomes did not differ between categories of AGD. This latter result differs from our previous finding of an inverse relationship between AGD and pregnancy outcomes in first- and second-parity Canadian Holstein cows, emphasizing the need to test and validate this new phenotype in diverse cow populations.
The relationship between serum anti-Müllerian hormone concentrations and fertility, and genome-wide associations for anti-Müllerian hormone in Holstein cowsThe objectives of this study were to (1) evaluate factors associated with variation in circulating anti-Müllerian hormone (AMH) concentrations, (2) establish an optimum AMH threshold predictive of pregnancy to first artificial insemination (P/AI), (3) examine the relationship between AMH and fertility (P/AI, pregnancy loss between 30 and 60 d after artificial insemination, and pregnancy risk up to 250 d postpartum), and (4) identify quantitative trait loci associated with phenotypic variation of AMH concentrations in dairy cows. Serum AMH concentrations (pg/mL) were determined at 7 ± 2.4 d postpartum in 647 lactating Holstein cows (213 primiparous, 434 multiparous) from 1 research and 6 commercial dairy herds in Alberta, Canada. Of these, 589 cows were genotyped on the 26K Bovine BeadChip (Neogen Inc., Lincoln, NE) and subsequently imputed to the Illumina Bovine High Density BeadChip (Illumina, San Diego, CA) for genome-wide association analysis for variation in serum AMH concentrations. Factors associated with variation in serum AMH concentrations and the relationship between categories of AMH and aforementioned fertility outcomes were evaluated only in a subset of 460 cows that had a complete data set available. The overall mean (±standard error of the mean), median, minimum, and maximum AMH concentrations were 191.1 ± 6.3, 151.7, 13.9, and 1,879.0 pg/mL, respectively. The AMH concentrations were not associated with herd, precalving body condition score, postpartum week, and season of sampling; the lactation number, however, had a quadratic relationship with serum AMH concentrations (116.2, 204.9 204.5, and 157.9 pg/mL for first, second, third, and ≥fourth lactation, respectively). The optimum AMH threshold predictive of P/AI could not be established because the receiver operating characteristic curve analysis model was nonsignificant. Categories of AMH [low (<83.0 pg/mL; n = 92), intermediate (≥83.0 to ≤285.0 pg/mL; n = 276), and high (>285.0 pg/mL; n = 92) based on lowest 20%, intermediate 60%, and highest 20% serum AMH) had no associations with P/AI (34, 43, and 40%), pregnancy loss between 30 and 60 d after artificial insemination (20, 12, and 8%), or pregnancy risk up to 250 d postpartum. One candidate gene associated with AMH production [AMH gene on Bos taurus autosome (BTA) 7] and 4 candidate genes related to embryo development (SCAI and PPP6C genes on BTA11 and FGF18 and EEF2K genes on BTA20 and BTA25, respectively) were in linkage disequilibrium with single nucleotide polymorphisms associated with phenotypic variation in serum AMH in dairy cows.
The relationship between serum insulin-like growth factor-1 (IGF-1) concentration and reproductive performance, and genome-wide associations for serum IGF-1 in Holstein cowsThe objectives of this study were to determine (1) factors associated with serum concentration of insulin-like growth factor-1 (IGF-1); (2) the relationship between serum IGF-1 concentration during the first week postpartum and ovarian cyclicity status by 35 d postpartum (DPP); (3) an optimum serum IGF-1 concentration threshold predictive of pregnancy to first artificial insemination (P/AI), including its diagnostic values; (4) the associations among categories of serum IGF-1 concentration and reproductive outcomes (P/AI and pregnancy risk up to 150 and 250 DPP); and (5) single nucleotide polymorphisms (SNP) associated with phenotypic variation in serum IGF-1 concentration in dairy cows. Serum IGF-1 concentration was determined at 7 (±2.4; ±standard error of the mean) DPP in 647 lactating Holstein cows (213 primiparous, 434 multiparous) from 7 herds in Alberta, Canada. The overall mean, median, minimum, and maximum serum IGF-1 concentrations during the first week postpartum were 37.8 (±1.23), 31.0, 20.0, and 225.0 ng/mL, respectively. Herd, age, parity, precalving body condition score, and season of blood sampling were all identified as factors associated with serum IGF-1 concentrations. Although serum IGF-1 concentration during the first week postpartum had no association with ovarian cyclicity status by 35 DPP in primiparous cows, it was greater in cyclic than in acyclic multiparous cows (32.2 vs. 27.4 ng/mL, respectively). The optimum serum IGF-1 thresholds predictive of P/AI were 85.0 ng/mL (sensitivity = 31.9%; specificity = 89.1%) and 31.0 ng/mL (sensitivity = 45.5%; specificity = 66.9%) for primiparous and multiparous cows, respectively. When cows were grouped into either high or low IGF-1 categories (greater or less than or equal to 85.0 ng/mL for primiparous cows and greater or less than or equal to 31.0 ng/mL for multiparous cows, respectively), primiparous cows with high IGF-1 had 4.43 times greater odds of P/AI and a tendency for higher pregnancy risk up to 150 DPP than those with low IGF-1, but not up to 250 DPP. Likewise, multiparous cows with high IGF-1 had 1.61 times greater odds of P/AI than those with low IGF-1. Pregnancy risk up to 150 and 250 DPP, however, did not differ between IGF-1 categories in multiparous cows. Moreover, 37 SNP across 10 Bos taurus autosomes were associated with variation in serum IGF-1 concentration, and 4 previously identified candidate genes related to fertility that were in linkage disequilibrium with some of these SNP were also identified.