Growth Of Post-Weaned Grazing Dairy Heifers When Evaluating The Effects Of Providing Shade Or Parasite Control

Sahar, Mohammad W. M.S., Purdue University, December 2014. Growth of PostWeaned Grazing Dairy Heifers when Evaluating the Effects of Providing Shade or Parasite Control. Major Professor: Tamilee Nennich. Reduced heat stress and lower gastrointestinal parasite loads can increase growth rate in heifers, potentially reducing the age at first breeding and lowering the costs associated with raising replacement dairy heifers. Providing shade is a recommended practice for reducing heat stress of grazing animals and is considered important for their wellbeing and productivity. However, limited information is available on the growth performance of young grazing dairy heifers when they are provided shade. Likewise, numerous products exist to prevent gastrointestinal parasites in animals. The development of new anthelmintic products, such as LongRange® (eprinomectin), increase the need for research to help understand the effects of these products on growth rates and fecal egg counts (FEC) in post-weaned dairy heifers. Studies were conducted to evaluate management strategies for reducing heat stress and parasite loads in pre-pubertal grazing dairy heifers. The objectives of these studies were: Study 1) to determine the effects of shade on the growth performance of grazing Holstein dairy heifers throughout the summer months, and Study 2) to compare the effect of eprinomectin (LongRange®) and doramectin (Dectomax®) on weight gain, structural growth, and FEC of post-weaned dairy heifers grazed over the summer months.