Growth Endocrine Axis and Bovine Chromosome 5: Association of SNP Genotypes and Reproductive Phenotypes in an Angus, Brahman and Romosinuano Diallele

The growth endocrine axis influences reproduction. A QTL associated with enhanced ovulation exists on chromosome 5 in cattle and there are 6 genes underlying this region involved in the mechanisms of GH action. Resequencing exons, 5’ and 3’ untranslated regions and conserved non-coding regions of these genes in a multibreed resource population revealed 75 SNP usable for genotype to phenotype association studies. In the current study, phenotypes included age at first calving, calving interval, days to calving, and pregnancy rate. Data were collected from developing heifers (n = 650) of a diallele composed of Angus, Brahman, and Romosinuano breeds. A SNP in the promoter of the signal transducer and activator of transcription (STAT)2 gene, which is a second messenger of GH, had minor allele frequency \u3e 10% across the three breeds. This SNP did not deviate from Hardy- Weinberg equilibrium (X2 = 1.00, P \u3e 0.31), so deemed useful for genotype to phenotype association analyses. Since the remaining SNP appeared to predict breed, they were used to correct for population stratification using STRUCTURE, which revealed three distinctive ancestral clusters. No significant association was detected between the STAT2 genotype and reproductive traits in mixed effects analyses using genotype as a fixed term, sire as a random term, and coefficient of ancestry as a covariate; however, the interaction of SNP genotype and ancestral cluster was associated with the traits days to calving (P \u3c 0.05) and calving interval (P \u3c 0.10). Interaction plots revealed a higher estimated effect of heterozygous genotype in cluster 1 (inferred primarily from Brahman) and lower estimates in clusters 2 and 3 (inferred primarily from Bos taurus). The heterozygous genotype extended these trait levels ~100 d. A SNP in the promoter of the STAT2 gene was associated with fertility trait levels in admixed cows of the breeds Angus, Brahman, and Romosinuano. The effect appeared to be a non-additive genetic relationship as heterozygous genotype extended levels of traits indicative of postpartum rebreeding

39 Concentration of obestatin in different stages of ovarian activity in cattle

The objective of the present study was to measure serum levels of obestatin by ELISA with the purpose of establishing parameters and being able to use it as an endocrine marker for the selection of reproductive characteristics of milk and beef cattle. In test 1, 15 Creole cows with genetic tendencies of Charolais, Angus, Brangus, and Gelbvieh were sampled in diestrus and 15 in proestrus, determining their structures with an Aloka Prosound ultrasound with a 7.5-MHz linear transducer. In test 2, 16 Holstein cows were sampled in 2 different ovarian stages, diestrus and proestrus. The standardized technique was a bovine obestatin 96-well ELISA kit from My Biosource Inc. The data were analysed by measuring central tendency and linear regression, where the average levels of obestatin were related to the corpus luteum size and size and number of follicles in milk and beef cattle. We found average levels of 556.99 and 453.35 pg for beef and dairy cattle, respectively (P&amp;lt;0.05). We also found a significant difference (P&amp;lt;0.05) in obestatin concentrations depending on the size of the follicles (751.74, 615.33, and 357.39 pg for follicles of 15, 10, and 5mm, respectively). We found a significant difference in concentration of obestatin (644.53, 550.69, and 455.88 pg; P&amp;lt;0.05) for corpus luteum sizes of &amp;gt;20mm, 10–20mm, and &amp;lt;10mm, respectively. In dairy cattle, obestatin levels were also evaluated at different stages of the cycle, and we found concentrations of 414.79 pg in diestrus and 530.48 pg in proestrus (P&amp;lt;0.05). We conclude that obestatin concentration is positively associated with a greater number and size of follicles as well as with larger corpus luteum because its effect on cell proliferation interacting positively with high levels of progesterone in the blood. We found higher concentrations in beef cattle than in dairy cattle. </jats:p

Growth Endocrine Axis and Bovine Chromosome 5: Association of SNP Genotypes and Reproductive Phenotypes in an Angus, Brahman and Romosinuano Diallele

The growth endocrine axis influences reproduction. A QTL associated with enhanced ovulation exists on chromosome 5 in cattle and there are 6 genes underlying this region involved in the mechanisms of GH action. Resequencing exons, 5’ and 3’ untranslated regions and conserved non-coding regions of these genes in a multibreed resource population revealed 75 SNP usable for genotype to phenotype association studies. In the current study, phenotypes included age at first calving, calving interval, days to calving, and pregnancy rate. Data were collected from developing heifers (n = 650) of a diallele composed of Angus, Brahman, and Romosinuano breeds. A SNP in the promoter of the signal transducer and activator of transcription (STAT)2 gene, which is a second messenger of GH, had minor allele frequency \u3e 10% across the three breeds. This SNP did not deviate from Hardy- Weinberg equilibrium (X2 = 1.00, P \u3e 0.31), so deemed useful for genotype to phenotype association analyses. Since the remaining SNP appeared to predict breed, they were used to correct for population stratification using STRUCTURE, which revealed three distinctive ancestral clusters. No significant association was detected between the STAT2 genotype and reproductive traits in mixed effects analyses using genotype as a fixed term, sire as a random term, and coefficient of ancestry as a covariate; however, the interaction of SNP genotype and ancestral cluster was associated with the traits days to calving (P \u3c 0.05) and calving interval (P \u3c 0.10). Interaction plots revealed a higher estimated effect of heterozygous genotype in cluster 1 (inferred primarily from Brahman) and lower estimates in clusters 2 and 3 (inferred primarily from Bos taurus). The heterozygous genotype extended these trait levels ~100 d. A SNP in the promoter of the STAT2 gene was associated with fertility trait levels in admixed cows of the breeds Angus, Brahman, and Romosinuano. The effect appeared to be a non-additive genetic relationship as heterozygous genotype extended levels of traits indicative of postpartum rebreeding

Long-term forage and cow-calf performance and economic considerations of two stocking levels on chihuahuan desert rangeland

Forage and cow-calf productivity on two lightly and two conservatively grazed pastures were evaluated over a 15-year period (1997-2011) in the Chihuahuan Desert of south-central New Mexico. Spring-calving Brangus cows were randomly assigned to pastures in January of each year. Pastures were similar in area (1 098 ± 69 ha, mean ± SE) with similar terrain and distance to water. Utilization of primary forage species averaged 27.1 ± 3.0% in lightly stocked pastures and 39.4 ± 4.0% on conservatively stocked pastures. No differences in perennial grass standing crop (163.5 ± 52.2 kg·ha-1) and calf weaning weights (286.1 ± 2.6 kg) were detected (P &gt; 0.10) between light and conservative treatments. Lightly grazed pastures yielded greater (P &lt; 0.05) kg of calf weaned·ha-1 and calf crop percent than conservatively grazed pastures in 1998 due to complete destocking of conservatively grazed pastures during that slight drought (i.e., rainfall was 75% of normal in 1998). After the initial 5 years of study (1997-2001), all pastures were destocked for 4 years (2002-2005) due to drought as rainfall was only 50% or less of normal. Pastures were then restocked for another 6 years (2006-2011). Postdrought, the percentage change in perennial grass standing forage crop (kg·ha-1) was -4.0 and -14.4 ± 2.5 % (P &lt; 0.09) in the light and conservative grazed pastures across the 6 years, respectively. While conservative stocking rates may provide higher net financial returns than light stocking rates during nondrought years as there were more AU per pasture, potential losses from cattle liquidation during short-term (i.e., 1-year) droughts could nullify this advantage. Results suggest that light grazing use of forage is a practical approach for Chihuahuan Desert cow-calf operations to minimize risk of herd liquidation during short-term drought. © 2015 Society for Range Management. Published by Elsevier Inc. All rights reserved.The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information