The effects of high environmental temperatures and night feeding on performance of dairy cows.

Abstract

The objectives included in his title were studied in two trials. In Trial 1, Dry Matter Intake (DMI) was determined in two groups of cows (3 animals in each group) in which one had free aces to water and food (pasture) during 24 h of day. The second group was kept indoors between the afternoon and morning milkings without food and water. DMI of cows at pasture was determined by the use of Cr2O3 as a marker following the technique proposed by Le Du and Penning (1982). Cows with free access to food during 24 hours of the trial had a DMI of 12.8 kg/day. In Trial 2 the animals were treated the same way as trial 1 (with or without food at night). In this trial cows were not only on pasture. All animals received 4 kg of concentrate per day. Milk yield of the two groups of cows (8 per group) was recorded. Cows with free access to food during the 24 hours of the day produced 20.9 kg of milk per day. The ones without food at night produced 17.6 kg of milk per day. Differences were significantly different (p<0.01). During the period in which these trials took place the average maximum and minimum temperature were 31.5 and 14 ºC respectively.