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Heat Tolerance Comparisons between Jersey and Holstein Cows

Louisiana Agricultural Experiment Station

Abstract

Producing cows used in this study were handled as two separate dairy units at Louisiana State University. Each unit consisted of two dairy breeds and totaled in 1944 36 Holsteins and 16 Jerseys, and in 1945, 41 Holsteins and 27 Jerseys. Only 13 Holsteins and 8 Jerseys were the same cows for the two years. Observations made totaled 26 and covered a period of 13 weeks in 1944, while in 1945 only 15 observation days were used covering a much shorter period of time. Air temperature during days of observation varied in 1944 from 65 to 93° F. with an average of 85.1° F. In 1945 the range was from 75–91° F. with an average of 85.6° F.

Jersey and Holstein comparisons follow:

1. During 1944 the Holstein's body temperatures averaged 103.3° F. as compared to 102.6° F. for Jerseys. In 1945 the average for Holsteins 104.5 or 0.8° higher than for Jerseys.
   
2. Differences between breeds on the basis of respiration and pulse rates were small and not consistent as between years.
   
3. Minimum, or normal temperatures were about the same for the two breeds, with higher maximum temperatures registered by Holsteins.
   
4. Rate of increase of body temperature as the result of air temperature increase was greater for Holsteins than for Jerseys.
   
5. Data for 1944 only indicate that an increase in humidity tends to slightly increase body temperature and respiration rate of Jerseys with the opposite effect on Holsteins. In all cases changes in air temperature had a much greater influence than did changes in humidity.
   
6. Holstein cows on hot days frequented wet spots in the shade and would lie in mud and water. As a result they came into the milking barn in the evening covered with dirt and mud. Jerseys showed little tendency along this line.
   
7. The grouping of Holstein cows on the basis of percentage white on total body surface and percentage of body surface above belly that was white failed to reveal any relationship between amount of white and heat tolerance. A tendency in this direction was probably over-shadowed by other more important factors.