Browsing by Subject "Bos taurus"
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Item Evaluation of heterosis and heterosis retention in Bos taurus-Bos indicus crossbred cattle for productivity traits in cows(Texas A&M University, 2005-11-01) Meuchel, Meredith ChristineReproductive and weight traits were analyzed for Angus (A), Brahman (B), Hereford (H), and Nellore (N) straightbred cows; F1 NA cows; 3/8N 5/8A cows and quarter blood composite cows (BANH) of the four straightbreds in Central Texas. Heterosis was estimated for calf crop born (CCB), calf crop weaned (CCW), and calf survival (CS) by linear contrasts within cow breed groups. F1 NA cows expressed heterosis (P < 0.0001) for CCB (0.22) and CCW (0.20). Except for the 3/8N 5/8Ac cows, which resulted from the mating of NA bulls to 3/4A 1/4N cows, all of the crossbred cow breed types expressed significant heterosis (P < 0.05) when compared to the weighted average of the parental purebreds for CCB. BANHc cows that were the result of mating NA bulls to HB cows expressed heterosis for CCB (0.35) (P < 0.001) and CCW (0.29) (P < 0.05). The 3/8N 5/8Aa females produced by mating 3/4N 1/4A bulls to NA cows expressed heterosis (P < 0.0001) for CCW (0.20). Heterosis for calf survival was near zero for all breed types, but only two breed types of 3/8N 5/8A cows were significantly greater than the weighted average of the parental purebreds. Heterosis for birth weight (BWT) and weaning weight (WWT) was also analyzed by linear contrasts within cow breed groups. The BANHb and BANHc cows produced from mating NA bulls to BH and HB F1 cows, respectively, expressed heterosis for BWT (2.89 + 0.79 (P < 0.001) and 3.38 + 1.51 (P < 0.05)). All cow breed types expressed significant heterosis (P < 0.05) for WWT. The BANH2 cows resulting from the mating of NA bulls to F2 HB or BH cows expressed heterosis (P < 0.0001) for WWT (52.01 kg + 9.88).Item Evaluation of heterosis and heterosis retention in Bos taurus-Bos indicus crossbred cattle for reproductive and maternal traits in cows(Texas A&M University, 2007-04-25) Neufeld Arce, Rodney OliverReproductive, maternal and weight traits were analyzed for Angus (A), Brahman (B), Hereford (H), and Nellore (N) straightbred cows; F1 NA; 3/8N 5/8A cows; and four breed composite cows (BANH) at the McGregor Research Station in Central Texas. Heterosis was estimated for calf crop born (CCB) (n = 1,698), calf crop weaned (CCW) (n = 1,698), calf survival (CS) (n = 1,388), birth weight (BW) (n = 1380), weaning weight (WW) (n = 1,198), and cow weight at palpation (PWT) (n = 1,929) by linear contrasts for cow breed and cow breed group. F1 NA and the quarter breed composite BANH dam group expressed significant (P < 0.0001) heterosis for calf crop born and calf crop weaned. The 3/8 N 5/8 Aa produced by matings of 3/4 A 1/4 N bulls to NA dams expressed significantly more heterosis for CCB (P < 0.0001) and CCW (P < 0.01), while the 3/8 N 5/8 Ac dams expressed less heterosis than predicted from the dominance model for both traits. For CS the 3/8 N 5/8 Aa expressed the same amount of heterosis as predicted from the dominance model of 0.05, while the 3/8 N 5/8 Ab and 3/8 N 5/8 Ac dams expressed less heterosis than predictions based on the dominance model. Heterosis estimates were only significantly higher (P < 0.10) for BANHb dams than expectations from the dominance model. For BW all the BANH cows expressed significant heterosis except for the BANH2 cows which expressed significant (P < 0.05) negative heterosis of -0.96 kg. Calves out of F1 NA cows were heaviest at weaning with 239 kg. All BANH cows expressed significant (P < 0.0001) heterosis for weaning weight except for the BANHc cows. These heterosis estimates were higher than those expected from the dominance model for BANHb and BANH2 cows, while the heterosis estimate was slightly lower in BANHa cows and similar for BANHc cows. All 3/8 N 5/8 A cows expressed less heterosis for WW than prediction from the dominance model. Nellore cows were the heaviest at four years of age with 542 kg. Only the BANHb and BANHc cows expressed significant (P < 0.05) heterosis for PWT. None of the 3/8 N 5/8 A cows expressed heterosis for cow weight at palpation. Results from this study showed that heterosis levels expressed by the different crossbred cow types were generally equal or higher to those predicted by the dominance model.Item Identification of Signatures of Selection in Bos Taurus Beef and Dairy Cattle Using Genome-wide SNP Genotypes(2010-10-12) Choi, Jung WooThe objectives of this study were to identify signatures of selection in Bos taurus beef and dairy cattle populations and to annotate regions of selection with gene, function and QTL information. Differences in minor allele frequencies, population-average FST, population-specific FST, and integrated extended haplotype homozygosity scores were applied to a subset of the bovine HapMap data to characterize signatures of selection in 7 Bos taurus beef and 5 Bos taurus dairy cattle populations. Numerous single nucleotide polymorphisms (SNP) exhibited evidence of selection across the genome and regions of BTA2 and BTA14 that are considered to be under positive selection in beef and dairy cattle, respectively, were highlighted. The current density of SNP limited our ability to annotate regions putatively under selection because most SNP in the assay were intergenic. This is likely because of the betweenbreed SNP discovery method that was used, which typically identifies SNP with higher allele frequencies.