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Jae-Ho Kim

Document Type

Thesis - University Access Only

Award Date

1998

Degree Name

Doctor of Philosophy (PhD)

Department / School

Animal Science

Abstract

The genotypic effect of four RFLP markers on cattle production traits including cow growth traits, cow production traits, cow feed intake and efficiency, calf growth traits, calf feed intake, and carcass traits were evaluated. The markers adapted for the study were two markers from regions of growth-related genes (bST: bovine somatotropin and IGF-1: insulin-like growth factor 1) and the other markers from milk protein genes (K-C: kappa casein and P-LG: beta lactoglobulin). The entire data set were composed of 416 crossbreed cows and 360 calves born from 1991 to 1997, but the number of animals used for each analysis varied. Calf birth weight was associated with calf P-LG genotype (P=0.06), with the heaviest weight for AA genotype calves. Cow P-LG locus also had slight tendency of association with calf birth weight (P=0.12). Dominance gene action from calf P-LG locus and additive gene action from cow P-LG locus were observed from an allele substitution analysis. The AA genotype of cow IGF-1 locus was related with highest production of 24-hour milk (P=0.04) and calf weaning weight (P=0.01). Milk energy efficiency of cow was affected by IGF-1 locus (P=0.06). Milk fat concentration was associated with bST locus (P=0.09). BB genotype cows produced the highest fat concentration, and a dominance effect of the locus on the trait was detected. Milk protein and non-fat solid concentrations were also affected by bST locus (P-values were 0.05 and 0.09, respectively). The bST B allele produced higher protein and non-fat solid concentrations in milk than A allele. Milk lactose concentration was influenced by the K-CN locus (P=0.06), and highest concentration was seen from BB genotype cows with a dominant gene action. Effect of the IGF-1 locus also approached significance on lactose concentration (P=0.11). Carcass traits were analyzed in two ways based on 1) constant carcass weight, and 2) constant slaughter age. External fat thickness was significantly associated with the bST locus (p=0.06) when adjusted for final age. Animals with BB genotype tended to be leanest, and an additive gene action was evident from allele substitution analysis. Yield grade, KPH, and retail cutability were also influenced by bST locus (P-values were 0.07, 0.04, and 0.05, respectively) in age-constant analyses. The highest yield grade was found from AA genotype, and the lowest KPH percentage and the highest retail cutability were observed from BB genotype of the bST locus. When traits were adjusted for carcass weight, no significant effect of the bST locus on carcass traits were detected except on KPH (p=0.06). Calf P-LG locus was associated with rib-eye area (P=0.03), marbling score (P=0.08), yield grade (P=0.05), KPH (P=0.06), and retail cutability (P=0.06) when the traits were adjusted for carcass weight. The A allele was related with larger rib-eye area and higher retail cutability than the B allele. The B allele was associated with increased marbling (P=0.08), yield grade (P=0.05), and KPH (P=0.06), and additive gene action was indicated. When final age was used as a covariate, only yield grade, KPH, and cutability showed significant association with the P-LG locus, and P-values were 0.04, 0.06, and 0.04, respectively. No effects on external fat and choice grade were detected at the P-LG locus. In conclusion, possibility of detecting QTLs or linked QTLs through evaluated candidate markers was obvious among some traits, and further studies might facilitate application of genetic marker based animal selection in an animal breeding system.

Library of Congress Subject Headings

Cattle -- Molecular genetics
Cattle -- Productivity
Calves -- Growth
Cattle -- Feed utilization efficiency
Cattle -- Carcasses

Format

application/pdf

Number of Pages

215

Publisher

South Dakota State University

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