Publication Date


Advisor(s) - Committee Chair

John Shirley, Elmer Gray

Degree Program

Department of Agriculture

Degree Type

Master of Science


A study of the reproductive performance of 179 dairy cows during the period from December 1978 through March 1984 was conducted at the Western Kentucky University Farm, Bowling Green, Kentucky. The climatic data showed seasonal variation in temperature as follows: winter 3.10C, spring 15.7°C, summer 23.8°C, and fall 12.0°C. The seasonal humidity was similar for winter (81.2%), spring (83.4%), and fall (85.3%); but for summer it was considerably higher (89.4%).

The conception rate varied through all the months but was lowest during the summer months. Seasonal data for conception rate were obtained and the results were as follows: winter 54.1%, spring 46.4%, summer 15.6% and fall 39.0%. Low fertility during summer months was associated with high air temperatures and high relative humidities. The coefficient of correlation for temperature vs. conception was low (-0.15) because there was low fertility in some winter months and in some summer months. The coefficient of correlation for humidity vs. conception was high (-0.65), and the coefficient of determination was 42%. A completely randomized design and analysis were used, resulting in significant differences among seasonal fertility rates but no significant differences among months within seasons. Significant differences were found for the following comparisons: winter vs. spring, summer, and fall; spring vs. winter, summer, and fall; and summer vs. spring, fall, and winter. The total services involved were 546, and the total conceptions obtained were 155--resulting in a service per conception ratio of 3.52. The average number of days open was 177 (79 cows). The average number of days in the calving interval was 457 (63 cows).


Agriculture | Animal Sciences | Dairy Science | Life Sciences