Feasibility of Heat Stress Alleviation for Holstein Lactating Cows by a tunnel-ventilated, water-padded barn in hot and humid summer in Taiwan
Date Issued
2011
Date
2011
Author(s)
Shiao, Tzong-Faa
Abstract
Heat stress from high temperature and humidity is always the bottleneck in enhancing lactation performance of dairy cows in Taiwan. Improving the barn environment is the most effective and direct method to alleviate cow heat stress. The feasibility of heat stress alleviation for Holstein lactating cows by a tunnel-ventilated, water-padded (TP) barn was assessed in this study. In 2005, a crossover designed experiment was conducted for 30 days a period. A total of 42 head of cows with milk yield of 26.2 kg a day were assigned into the TP barn or the conventional barn. The rectangle TP barn has a raising space for 48 head of lactating cows. Eight exhaustive fans and an L shape water-pad were set at the two end walls in the TP barn. Heavy plastic curtains formed both long side walls contributed the tunnel effect. The exhaustive fans would be turned on following the increasing air temperature and provided the highest daytime air speed of 1.66 m per second and air exchange rate of two times per minute. Evaporating water in the pad absorbs heat from the incoming air and cools the air. Four hung fans operated all day long were set in the conventional barn. Additional six 30-min sprinkler cooling cycles a day were arranged along the intake alley. The results indicated that TP barn could effectively cut down 2.4℃ more at the highest daytime temperature, and decreased 2.5 h more for cows suffering the medium heat stress (78 < THI ≤ 84) than conventional barn did. However, the persistently high relative humidity (> 93%) and low air speed inside the TP barn increased the heat load for cows. Cows raised in the TP barn had the higher 4 a.m. respiration rate (62 vs. 50 breaths/min), 4 a.m. rectal temperature (39.58 vs. 39.31℃), and 2 p.m. rectal temperature (39.75 vs. 39.47℃) than those raised in the convention barn. TP barn environment decreased the partial pressure of CO2 in cow blood (41.4 vs. 43.8 mmHg), thus increased the blood pH. Meanwhile, TP barn environment significantly decreased cow intake activity and resulted in the lower dry matter intake and 4% fat corrected milk yield by 7.6% (17.0 kg vs. 18.4 kg) and 10.1% (23.1 kg vs. 25.7 kg), respectively. Percentage of milk protein was also decreased. But rumen digestion pattern was kept the same. Diurnal rumen pH, NH3-N and volatile fatty acid productions were not influenced by barn environments. To improve the TP barn environment, fan numbers were increased and same sprinkling program as that in the conventional barn were applied in 2006. The highest daytime air speed at cow level and air exchange rate reached 2.38 m/s and 3.2 times/min after the modification. Both parameters at night in the TP barn were estimated to be 1.17 m/s and 1.4 times/min, respectively. In 2006, 36 cows allocated in a 3 x 3 Latin square with 21 days a period were raised in three barn cooling treatments: the conventional barn like in 2005 trial, a TP barn and a TP barn with sprinkler cooling (TP+SP). Both TP barns were more efficient in reducing the daytime temperature and the temperature humidity index. The barn temperature was less than 26°C for an extra 4.2 h per day, but the relative humidity was above 96% in both TP barns. Cows in both TP barns had higher 3 a.m. respiration rates and skin temperatures than cows in the conventional barn. Vaginal temperature was persistently high in cows in the TP barn; in the two barns with sprinkler cooling, vaginal temperature could effectively decreased 0.4 to 0.6°C following the sprinkling and milking. The intake activity, rumen digestion, and milking performance of cows raised in the three environments were similar. Cows in both TP barns ingested more dry matter. Cows in the TP+SP barn tended to produce more milk than those in the conventional barn (25.4 vs. 24.7 kg, P = 0.10). Although cows’ heat stress was not completely alleviated in these three barns, the TP+SP treatment resolved the negative impact of a previous TP barn built in 2004 on intake and milk yield by increasing air speed and using sprinkler cooling. Thus, it is expected that TP+SP barns will be beneficial in areas of high humidity. Except for the physiological responses and milking performance, the reproductive efficacy of cows is also influenced by the environmental heat stress. The serum progesterone levels during synchronization treatment were similar from 12 cows raised in the conventional barn and TP barn in 2005. In 2007 summer, a total of 40 cows were assigned into the conventional barn or the TP+SP barn (air exchange rate of 3.2 times/min) for a period of 90 days. A target breeding program with two consecutive prostaglandin injections at 14-d interval was applied. No matter cows were raised in the conventional barn or the TP+SP barn, responses to prostaglandin treatment of cows in hot summer was not ideal. Conception rate per AI of cows in these two barns were 20.7% and 17.4%, and for the whole period pregnancy rate were 30% and 21.1%, respectively. From 2008 to 2010, reproductive field data of lactating cows were collected. Data were categorized and statistically analyzed in a 2 x 2 factorial design including barn cooling treatments, conventional barn or TP+SP barn, and seasons, cool or hot season. Results showed that conception rate of cows were not affected by the barn treatment. In hot season (May to Oct.), conception rate of cows in conventional barn and TP+SP barn were 29.0% and 26.4%, and were 40.2% and 36.3% for the whole year, respectively. Results from all three studies suggested that the high humidity problem in TP barn could be mitigated by the higher air speed. The application of sprinkler cooling in TP barn is beneficial for cows to dissipate their body heat so that to promote the milking performance. However, poor reproductive efficacy in the hot summer is not resolved by the TP+SP barn. Adequate air speed and lower humidity are likely to be key factors for further TP barn study.
Subjects
heat stress
Holstein lactating cow
humidity
a tunnel-ventilated
water-padded barn
Type
thesis
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