No description available.

Digitized by Kansas Correctional Industries

Typescript. / Digitized by Kansas Correctional Industries

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2007. / Title from title screen (site viewed Dec. 4, 2007). PDF text: vii, 141 p. ; 6 Mb. UMI publication number: AAT 3271905. Includes bibliographical references. Also available in microfilm and microfiche formats.

Thesis (M. Sc.)(Animal Science)--University of Pretoria, 2005. / Includes bibliographical references. Available on the Internet via the World Wide Web.

Thesis (M.S.)--Virginia Polytechnic Institute, 1946. / Includes bibliographical references (leaves 152-158). Also available via the Internet.

The objectives of this study were accomplished with two experiments in growing Bonsmara bulls (N = 68) (experiment 1), and Simmental crossbred calves (N = 132) (experiment 2). Specific objectives for experiment 1 were to characterize residual feed intake (RFI) in growing bulls, and examine relationships between RFI and performance, fertility, temperament and body composition traits. In experiment 2, the objectives were to examine stocker-phase supplementation effects on feedlot feed conversion ratio (FCR) and RFI and to characterize relationships between these feed efficiency traits, and performance and carcass traits in finishing calves. In both experiments, individual feed intakes and BW were measured. Ultrasound technology was used to measure body composition in experiment 1, while actual carcass measurements taken at harvest were used for experiment 2. Experiment 1 demonstrated that temperament affected ADG and DMI, but not FCR or RFI. Residual feed intake was not phenotypically correlated to scrotal circumference or bull fertility traits. Experiments 1 and 2 demonstrated that RFI was independent of ADG and BW, but that there was a tendency (P < 0.10) for RFI to be phenotypically correlated with 12th rib fat thickness (r = 0.20 and 0.22). However, RFI was not correlated with longissimus muscle area in either experiment. Both experiments demonstrated that low RFI (< 0.5 SD below mean RFI) calves consumed significantly (20 and 22%) less feed and had improved (21%) FCR compared to calves with high RFI (> 0.5 SD above mean RFI). Results from experiment 2 suggest that RFI measured while calves are consuming high-grain diets may be less influenced by previous level of stocker supplementation compared to FCR or residual gain efficiency traits. In summary, RFI was found to be phenotypically independent of growth rate and BW, had no effect on bull fertility or temperament traits, and was less impacted by previous plane of nutrition compared to FCR.

Neurotensin (NTS) is a tridecapeptide which is widely distributed in the central nervous system and digestive tract. It is highly expressed in neurons of the hypothalamus, a region of the brain known to control feeding behavior. Several studies have shown that intracerebroventricular injection of NTS decreased food intake in rats. NTS was therefore characterized and analyzed for associations with growth and carcass traits in beef cattle.<p>NTS mRNA was successfully isolated from brain, spinal cord, abomasum, rumen wall, small intestine and skin samples. The complete bovine mRNA sequence was obtained from skin, along with partial genomic sequence. Three single nucleotide polymorphisms (SNPs) in the 3 untranslated region (3UTR) and six intronic SNPs were identified. The three SNPs in the 3UTR were not in linkage disequilibrium. Of the three SNPs in the 3UTR, two had minor allele frequencies of 2% and therefore were not analyzed further. The minor allele frequencies for the third SNP (*419G>A) ranged between 0% and 23% for four major beef breeds. The *419G>A SNP was also used to map NTS to bovine chromosome five between markers BM6026 (13 cM, LOD=4.03) and RM103 (4 cM, LOD=3.63).<p>No significant associations between the *419G>A SNP and growth traits were identified. Statistical analysis revealed significant genotype associations for rib eye area (REA), grade fat and moisture in the Canadian Beef Reference Herd (CBRH). These associations were not verified in a second group of purebred yearling bulls. However, significant associations with end of trial fat, %fat and fat deviation were associations for marbling and quality grade. In all cases the AA genotype was associated with increased fat.<p>Although significant associations between carcass measurements and genotype at the *419G>A SNP were present in some populations, none of these associations were found in more than one population. It was therefore concluded that the *419G>A SNP on the bovine NTS gene does not prove to have an economic advantage to the beef cattle industry.

Neurotensin (NTS) is a tridecapeptide which is widely distributed in the central nervous system and digestive tract. It is highly expressed in neurons of the hypothalamus, a region of the brain known to control feeding behavior. Several studies have shown that intracerebroventricular injection of NTS decreased food intake in rats. NTS was therefore characterized and analyzed for associations with growth and carcass traits in beef cattle.<p>NTS mRNA was successfully isolated from brain, spinal cord, abomasum, rumen wall, small intestine and skin samples. The complete bovine mRNA sequence was obtained from skin, along with partial genomic sequence. Three single nucleotide polymorphisms (SNPs) in the 3 untranslated region (3UTR) and six intronic SNPs were identified. The three SNPs in the 3UTR were not in linkage disequilibrium. Of the three SNPs in the 3UTR, two had minor allele frequencies of 2% and therefore were not analyzed further. The minor allele frequencies for the third SNP (*419G>A) ranged between 0% and 23% for four major beef breeds. The *419G>A SNP was also used to map NTS to bovine chromosome five between markers BM6026 (13 cM, LOD=4.03) and RM103 (4 cM, LOD=3.63).<p>No significant associations between the *419G>A SNP and growth traits were identified. Statistical analysis revealed significant genotype associations for rib eye area (REA), grade fat and moisture in the Canadian Beef Reference Herd (CBRH). These associations were not verified in a second group of purebred yearling bulls. However, significant associations with end of trial fat, %fat and fat deviation were associations for marbling and quality grade. In all cases the AA genotype was associated with increased fat.<p>Although significant associations between carcass measurements and genotype at the *419G>A SNP were present in some populations, none of these associations were found in more than one population. It was therefore concluded that the *419G>A SNP on the bovine NTS gene does not prove to have an economic advantage to the beef cattle industry.

The objectives of this study were accomplished with two experiments in growing Bonsmara bulls (N = 68) (experiment 1), and Simmental crossbred calves (N = 132) (experiment 2). Specific objectives for experiment 1 were to characterize residual feed intake (RFI) in growing bulls, and examine relationships between RFI and performance, fertility, temperament and body composition traits. In experiment 2, the objectives were to examine stocker-phase supplementation effects on feedlot feed conversion ratio (FCR) and RFI and to characterize relationships between these feed efficiency traits, and performance and carcass traits in finishing calves. In both experiments, individual feed intakes and BW were measured. Ultrasound technology was used to measure body composition in experiment 1, while actual carcass measurements taken at harvest were used for experiment 2. Experiment 1 demonstrated that temperament affected ADG and DMI, but not FCR or RFI. Residual feed intake was not phenotypically correlated to scrotal circumference or bull fertility traits. Experiments 1 and 2 demonstrated that RFI was independent of ADG and BW, but that there was a tendency (P < 0.10) for RFI to be phenotypically correlated with 12th rib fat thickness (r = 0.20 and 0.22). However, RFI was not correlated with longissimus muscle area in either experiment. Both experiments demonstrated that low RFI (< 0.5 SD below mean RFI) calves consumed significantly (20 and 22%) less feed and had improved (21%) FCR compared to calves with high RFI (> 0.5 SD above mean RFI). Results from experiment 2 suggest that RFI measured while calves are consuming high-grain diets may be less influenced by previous level of stocker supplementation compared to FCR or residual gain efficiency traits. In summary, RFI was found to be phenotypically independent of growth rate and BW, had no effect on bull fertility or temperament traits, and was less impacted by previous plane of nutrition compared to FCR.