Monday, 28 October 2002: 2:00 PM
Animal production in a changing climate: impacts and mitigation
Climate can affect animal production both directly and indirectly. Indirect effects may include aspects such as the impacts of changes in livestock feedgrain availability and price and the impacts on livestock pastures and forage crops. Generally, markets tend to moderate the impacts of changes in feedgrain crops and the final effect in terms of the increase in prices of meat, milk or other animal products is substantially less than the initial grain price shock. The impact of climate on pastures and rangelands may include deterioration of pasture quality towards poorer quality, subtropical (C4) grasses in temperate pastoral regions as a result of warmer temperatures and less frost. There could also exist potential increases in yield and possible expansion of area if the climate change were favorable as a result of increase in CO2. Direct effects involve heat exchanges between the animal and the surrounding environment that are related to radiation, temperature, humidity and wind speed. Heat stress has a variety of detrimental effects on livestock, with significant effects on production and reproduction of dairy cows, swine, beef cattle and sheep. Thus, warming in the tropics and subtropics, or even in temperate regions during the warmer months would likely impact livestock production and reproduction negatively, producing reduced animal weight gain, dairy production and feed conversion efficiency. In terms of environmental management, however, the impacts could be reduced because of the ability of animals to adapt and by applying appropriate environmental modifications, such as shades and evaporative cooling. In some areas of the world, producers are already used to coping with hot weather. They probably have the means and management skills to at least partly counter the expected extra heat load. Therefore, the impacts of global warming could be more intense in cooler areas where heat controlling management and strategies are fewer. Impacts may be minor for relatively intense livestock production systems, since such systems control exposure to weather and provide opportunity for further controls. One way to look at the possible effects of global warming is analyzing the impacts of occasional hot weather patterns lasting several days, known as heat waves. Heat waves result in decreased feed intake and performance of feedlot cattle and in reduced milk yields of high producing dairy cows. Sometimes they may even cause death of vulnerable animals. Also, it should be considered that global warming during cooler periods in temperate regions could be beneficial, due to reduced feed requirements, increased survival of young and lower energy costs. This presentation will deal primarily with the direct effects of changing climate on animals, and will be mainly focused in the response of animals to temperature and other environmental factors, emphasizing the impact of increased environmental temperature on such a response. Different alternatives of management to cope with increasing heat stress will be presented. Environmental and nutritional management will be discussed.