Abstract:

In this experiment， tall trees were planted on the west side of a cowshed to shade sunlight from the west in summer. Three hundred and sixty dairy cows with similar health， body condition， and parity ［lactation days （185±25）， parity （2.5±0.5）， milk yield （31.02±1.25 kg）］ were randomly assigned to two groups. The two groups were housed in cowsheds with the same building structure and a south-north orientation. Poplar trees with a height of 15 m （crown length of 6 m， lower crown width of 0.8 m， and upper crown width of 0.3 m） were planted outside the west gable of one shed （shed-shaded）， and the other shed was left unshaded with no trees planted outside （control shed）. This study was carried out through three stages； The early hot season in May， the hot season from July to August， and late-hot season in October. The physiological and behavioral parameters of the cows， their milk yield， and nutrient digestibility of feed consumed were measured at all stages， and whole blood and serum biochemical parameters were measured throughout the experiment. It was found that： 1） Shading positively affected dairy cows in the hot season， but had little effect in the early and late stages of hot season. Shading reduced the ambient temperature in the shed during the hot season. The average daily temperature was 0.99 ℃ lower in the shaded shed than in the control shed， and the temperature was 1.13 ℃ lower in the shaded shed than in the control shed between 09：00 and 20：00 （P<0.05）. 2） During the hot season， the respiratory rate of cows in the shaded shed was 8.21% lower than that of cows in the control shed （P<0.05）， and the proportion of cows lying down in the shaded shed was increased by 7.42%. 3） Shading also improved nutrient digestibility of feed consumed in the hot season， with dry matter intake increased by 9.81% （P<0.05） and milk yield increased by 4.69% （P<0.05） for cows in the shaded shed compared with those in the control shed. The crude protein， neutral detergent fiber， and acid detergent fiber contents were also improved， with increases of 12.80%， 9.87%， and 19.40%， respectively， for cows in the shaded shed compared with those in the control shed. 4） The number of white blood cells， the lymphocyte ratio， the and platelet volume in whole blood were significantly higher in cows in the shaded shed （P<0.05） than in those in the control shed in the hot season， while the hematocrit and number of platelets were significantly lower in cows in the shaded shed （P<0.05）. In both the hot season and late-hot season， shading also increased the serum glucose and total protein contents （P<0.05） and decreased the serum cortisol content （P<0.05）. In summary， planting trees on the west side of cowsheds can effectively reduce the ambient temperature inside the shed， thereby relieving heat stress in cows during the hot season and improving their lactation performance. The results of this study provide a reference for improving productivity by managing greening and shading on farms.

Key words: dairy cow, shade, ambient temperature, lactating performance, blood physicochemical parameter