S1023: Enhancing production and reproductive performance of heat-stressed dairy cattle.
Statement of Issues and Justification
Project's Primary Website is at http://rps.uvi.edu/AES/S299/S299_home_page.html (direct link can be found under LINKS)Throughout the Southeast United States and in many subtropical and tropical regions dairy cattle are subject to elevated ambient temperature and/or high relative humidity for extended periods. In the Southeast US, ambient conditions frequently exceed the thermoneutral range and cause heat stress for 4 to 6 months of each year. In lactating dairy cows, heat stress reduces feed intake and elevates body temperatures, which are associated with reduced milk yield and reproductive performance. Moreover, genetic selection for milk yield has reduced the dairy cows' ability to regulate body temperature, which exacerbates the effects of heat stress. Environmental modifications to mitigate the impact of heat stress have been developed, but a recent analysis of Dairy Herd Improvement (DHI) records suggest that further research is needed; dairy herds in the Southeast US have lower milk yields, greater days open and higher somatic cell counts than those further north. To minimize the impact of heat stress on southeastern dairy producers, a thorough understanding of the effects of environmental, dietary and genetic modifications is necessary. In addition, a more complete understanding of the cellular and physiological mechanisms by which cows regulate body temperature will allow the development of new strategies for improving milk production,reproduction and embryonic survival during periods of heat stress.
Dairy cattle in the Southern region are annually exposed to prolonged periods of elevated humidity and heat which reduce feed intake, milk production and reproductive performance. Development and testing of effective management strategies to mitigate the negative effects of heat stress requires a coordinated research effort, which includes fundamental and applied research in nutrition and reproduction. This is best accomplished through a regional research project that includes shared resources and scientific expertise. There are RRF projects in the Southern region focused in whole or in part on enhancing production and reproductive performance of swine (S-288), poultry (S-1020; S-292) and beef cattle (S-284), but no similar regional effort focused on dairy cattle. Two related regional projects in the Western region focus on heat stress: W-112, Reproductive Performance in Domestic Ruminants; and W-173, Stress Factors of Farm Animals and Their Effects on Performance. One potential outcome of W-173 is to develop more cost effective techniques for reducing heat stress. Yet, neither of these projects focus on nutrition and reproduction interactions in heat-stressed dairy cattle. The intent of the current proposal is to complement, not duplicate, objectives of the two existing projects. Methodologies effective in reducing heat stress will be incorporated into the project and expanded to examine the potential of nutritional modification and hormonal therapy on subsequent production and reproduction. This project proposal fits within the region's priorities as described in the Southern Strategic Research Plan. The emphasis is on inter-disciplinary research to enhance efficiency and sustainability of an animal system in our region's unique climate.
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