Graduation date: 1980Testes size as an indicator of future growth was examined\ud in a total of 45 bull calves from spring calves born in 1978\ud and 1979. Scrotal circumference measurements were used as the\ud physical indicator of testicle size in the live animal.\ud Growth traits studied were preweaning average daily gain,\ud weaning weight, feedlot gain, market weight and weight per\ud day of age. Scrotal circumference measurements, and body\ud weights were taken at birth, midpoint of the nursing period,\ud and immediately before castration. Regression coefficients\ud were calculated using preweaning growth traits as dependent\ud on scrotal circumference.\ud Birth scrotal circumference was significantly related\ud only to mid-nursing weight (P<.05). Mid-nursing scrotal\ud circumference significantly predicted (P<.01) mid-nursing\ud to weaning growth rate, and weaning weight. Correlation\ud coefficients calculated for mid-nursing circumference and\ud growth traits were high and positive. Adjusting mid-nursing\ud scrotal circumference for body weight decreased the correlation coefficients. Correlation coefficients calculated\ud for the relationship of body weight and growth were high\ud and positive as expected, and similar to values between\ud scrotal circumference and growth.\ud Twenty-three of the castrated animals were utilized\ud in a postweaning feeding trial in order to examine the\ud relationship of preweaning scrotal circumference to\ud postweaning growth. Relationships between preweaning\ud testes size and feedlot gains were nonsignificant.\ud Measurements of scrotal circumference taken at mid-nursing\ud and castration were both significantly correlated (P<.01)\ud with market weight and weight per day of age, and so could\ud be used as indicators of final weight.\ud Birth testes size was a poor predictor of market traits\ud as correlations were low. As expected, midpoint weight\ud and weaning weight were highly correlated (P<.01) with end\ud of feedlot trial weight.\ud Early measurements such as at birth are not as valuable\ud in making growth predictions as are later measurements.\ud Findings indicate that measurements are best used to obtain\ud a ranking of the animals on a within year basis. Finally,\ud results suggest that scrotal circumference or body weight\ud are of equal value in predicting future performance in male\ud beef cattle and can be used as a management tool or practice
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