Nutrition and feeding of dairy cattle during hot weather
1998
Ronchi, B. (Universita della Tuscia, Viterbo (Italy). Istituto di Zootecnia)
Thermal stress due to the environmental temperatures can impact negatively on health and performance of intensively managed dairy cows. Some management strategies have been suggested to attenuate effects of thermal stress, including physical modification of the environment, genetic development of less heat-sensitive genotype and nutritional adjustments. Focus of this paper is on: 1) effects of heat stress on metabolic and nutritional status of dairy cows; 2) results obtained by applying nutritional and feeding strategies under heat stress; 3) potential practical feeding management during hot weather. Discussion concentrates primarily on energy, because of its critical rule in lactating dairy cows and drastic decline in feed intake occurring in heat stress conditions. Possible ways to increase energy intake and to improve energy balance of dairy cows exposed to hot have been discussed. Concerning protein nutrition, although a negative nitrogen balance occurs under heat stress, adding supplemental protein or varying rumen degradable protein does not always prove to be effective in terms of metabolic and productive benefits. Macromineral status is often altered, as a consequence of chronic exposure to hot climate. The mineral supplementation of basal diet may be useful to support homeostasis of dairy cows. Feed additives like vitamins, fungal cultures, and complex supplementation have been also suggested to limit direct or indirect effects of heat stress on nutritional and metabolic status
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