Access to shade during the dry period improves the performance of multiparous Holstein cows

Context Heat stress (HS) has a negative effect on milk production and on the final period of gestation. There is almost no information of HS effect on dairy cows with temperature–humidity index (THI) less than 72 and more than 68. Aim Determine the effect of voluntary access to shade during the dry period on physiological parameters and subsequent postpartum performance of Holstein cows. Methods Twenty-six multiparous cows were used in a randomised complete-block design to evaluate two treatments: without access to shade (CON) and with voluntary access to shade (SHA) for 62 ± 5.3 days before calving. During the dry period, cows were housed in two yards. After calving, cows were managed all together. The THI was used to characterise environmental conditions. During the dry period, rectal temperature (7:00 am and 5:00 pm), respiration rate (7:00 am, 1:00 pm and 5:00 pm) and animal behaviour (feed intake, rumination and standing) were measured. Dry matter (DMI) and water intake, bodyweight, body condition score, and serum insulin and non-esterified fatty acid concentrations were measured during dry and lactation periods. At calving, calf weight, composition of colostrum, placenta weight, cotyledon number and weight were recorded. During the lactation period, production and composition of milk and resumption of ovarian activity were measured. Key results Average THI during dry and lactation periods were 70.7 ± 4.88 and 57.2 ± 6.53 respectively. During the dry period, SHA cows had a lower respiration rate at 1:00 p.m. (56 ± 0.8 vs 67 ± 0.8 breath per minute (b.p.m), P < 0.0001) and at 5:00 p.m. (48 ± 0.8 vs 55 ± 0.8 b.p.m, P = 0.04), and higher DMI (12.0 ± 0.07 vs 11.4 ± 0.07 kgDM/cow.day, P < 0.0001) than did CON cows. Shaded cows produced more solid-corrected milk (30.4 ± 0.31 vs 29.5 ± 0.31 kg/cow.day, P = 0.04), fat (1.48 ± 0.040 vs 1.33 ± 0.040 kg/cow.day, P = 0.01) and protein (1.12 vs 1.03 ± 0.015 kg/cow.day, P = 0.01). Conclusion There was no effect of access to shade on calf weight, colostrum composition, placenta characteristics, serum non-esterified fatty acid and insulin concentrations, body condition score evolution, lactation DMI and days to first ovulation postpartum. Implications HS during the last 60 days of gestation negatively affected solid-corrected milk, daily fat and protein production.