Yanchu Fang

Publication Date


Advisor(s) - Committee Chair

Jodie Pennington, Elmer Gray, Gordon Jones


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Degree Program

Department of Agriculture

Degree Type

Master of Science


Of the fifty-nine Holstein cows (29 primiparous, 30 multiparous) involved in the Monsanto rBST project at Western Kentucky University dairy farm, twenty-eight cows were used to study the subtle effects of rBST on milk yield, body weight and condition, health and reproduction during the early lactation following rBST treatment.

The results demonstrated that even though bi-weekly administration of rBST to lactating cows tended to reduce cows' milk production during the next early lactation, no significant difference was found (P>.10) across treatments. As expected, days to first, second, third and fourth ovulations postpartum, days to each of the detected estrus, days to breeding, efficiencies of each of the four estrus detections, conception rate, days to pregnancy and calving scores did not differ (P>.10) among the animals used in the rBST research. There was no trend that reproduction right be impaired due to rBST treatment. Body weights among treatments also did not differ (P>.10). However, the interaction of treatment by lactation was significant (P<.10). Administration of rBST did not affect body weight for the cows with 2 lactations, but decreased average body weight by 10.8% for the cows with 3 or more lactations in weeks 2, 4 and 5 (P<.10) of the lactation following rBST treatment. There were significant differences among treatments for body condition scores in week 4 (P<.05) and week 5 (P<.10) postpartum. Treatment with 780 mg rBST at 14 day intervals lessened total body condition scores by 9%. The plots of body weight and condition scores changes suggested a trend of decreased body weight and condition scores during the next early lactation following rBST treatment. Somatic cell count, clinical mastitis, metritis, pyometra and cystic ovaries were unaffected in the current lactation when treatment with rBST occurred during the previous lactation.


Agriculture | Animal Sciences | Dairy Science | Life Sciences