Effect of Warm Weather on Grazing Performance of Milking Cows

Abstract

Observation made on 3 Jersey and 3 Holstein milking cows during the summer of 1945 at Baton Rouge, Louisiana, showed a progressive rise in their body temps. throughout the day. This rise was in step with increases from 73[degree] to 86.7[degree] F in atmospheric temps. Body temps. averaged 101.7[degree] F when cows left the milking barn at 5:45 A.M., 102.4[degree] F upon entering shade (av. time 9:20 A.M.) and continued to increase with the highest temp., [center dot] 103.5[degree] F, recorded at 3:00 P.M. Respiration rates showed a similar trend, increasing from 63 to 79 times per min. Continuous observations on grazing showed that during 2 relatively warm days cows grazed < 2 hrs., 1.9 and 1.8 hrs. during daytime (between A.M. and P.M. milking periods) but grazed 3 times as much, 5.7 and 5.5 hrs., at night (between P.M. and A.M. milking). Data on 2 cool days showed daytime grazing 2.4 times as great as for warm days, and 24-hr. grazing totals > 1 hr. longer than for warm days. The number of grazing periods averaged 1.4 for daytime and 2.7 for night. Cows seldom had but one important grazing period during the daytime. Three grazing periods were the most common at night and the time spent grazing averaged 5.5 hrs., while 3.5 hrs. were spent lying down and 0.7 hrs. standing without grazing.