Graduate Thesis Or Dissertation

 

Serum T₄ and liver NAD and NADP as performance indicators in beef cattle Public Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/gh93h365w

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  • The relationships of serum T₄ (thyroxine) levels and liver nicotinamide nucleotide coenzyme (NAD and NADP) levels with production of traits of beef cattle were investigated at both weaning (182 kg) and following performance testing (363 kg). In addition, the value of these parameters as selection criteria for improved performance was determined. Blood and liver samples were collected from 83 bulls and 41 heifers of the Hereford and Angus breeds in the years 1972 and 1973. The levels of T₄ present in the serum were determined by the Tetrasorb- 125 method (Abbott Laboratories, North Chicago, Illinois), T₄ levels at weaning were found to be positively associated with weaning age, while T₄ levels determined following performance testing were negatively associated with final age. This was due to the opposite influence of T₄ upon growth at the two different weights. Although T₄ level at 182 kg was found to be a significant predictor of subsequent rate and efficiency of gains, the relationship of T₄ to rate of gain was of small magnitude and its biological importance was negligible. In the case of feed per unit gain, an increase of one unit in T₄ level at 182 kg was found to result in a decrease of 0.098 kg of feed required per kg of gain. Fluorometric determination of the liver concentrations (μg /g of frozen liver tissue) of nicotinamide nucleotide coenzymes showed that NAD and NADPH were present in excess over NADH and NADP⁺ respectively. No significant differences in coenzyme concentrations due to age were detected within the sampling weight groups. Coenzyme levels were significantly higher at 363 kg than at 182 kg. The oxidized forms (NAD⁺ and NADP⁺) were found to positively influence rate and efficiency of gains, while these traits were influenced negatively by the reduced forms (NADH and NADPH). No biologically important predictive relationships between coenzyme levels at 182 kg and production traits were found that would have value in selecting for improved performance in beef cattle.
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