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Effect of shade access combined with or without sprinkling and ventilation on performance of Holstein cows in two lactation stages.
The negative effect of heat stress on dairy cows, with Temperature and Humidity Index (THI) over 72, has been extensively studied. However, there are few studies on THI values under 72 that compare the effect of heat stress in different lactation stages. The objective of this study was to determine the heat stress effect on two lactation stages with a THI below the threshold 72. Thirty nine multiparous, non-pregnant Holstein cows with more than 30 kg/cow.day of solid-corrected milk were used in a randomized complete block design to evaluate six treatments. The experimental design had a 3 by 2 factorial arrangement with three heat stress mitigation strategies: No shade (CON), access to shade only (SHA), and access to shade combined with sprinkling and ventilation (SSV), and two stages of lactation: early (S1) and late (S2), 12 ±10.3 and 201 ±45.8 days in milk respectively, during 81 days for a duration of 81 consecutive days. All treatments, except CON had access to artificial shade from 09:00 to 05:00 hours next day. From 05:00 to 09:00 hours all cows were managed together in a grazing session.Additionally,SSV cows had two 30 minutes sessions of ventilation and spray (09:00, 15:30 h). The average THI was 70.1 ±4.46 (minimum THI: 60.4; maximum ITH: 81.7) and the average hours above 72 were 7.8 ± 5.98. Animals in S1 presented higher solids-corrected milk reduction (P<0.0001; 5.4 and 1.9 kg/cow.day), and protein yield (<0.0001; 0.13 and 0.54 kg/cow.day) than animals in S2 when shade was not allowed (CON). It was concluded that under these conditions, animal productivity is more negatively affected in early lactation animals. The use of shade with or without spray and ventilation mitigates heat stress effects on both stages of lactation.
AN16571 Accepted 15 September 2017
© CSIRO 2017