Upper Critical Temperatures and Forced Ventilation Effects for High-Yielding Dairy Cows in a Subtropical Climate

Abstract

Upper limit of thermal stability and subsequent rise of thermoregulatory functions as affected by forced ventilation were examined. Rectal temperature, respiratory frequency, ear skin temperature, body weight, and milk yield were recorded biweekly July to March over 2 yr for 170 Israeli-Holstein cows (305-day milk yield 9000 kg/cow) at air temperatures 10 to 36 degrees C. Cows were in an open shelter. One side was force ventilated over 2.5 m along the stanchions (air velocity 1.5 to 3 m/s) from 0500 to 2200 h. Control side mean air velocity was .5 m/s. Within the 10 to 24 degrees C range, rectal temperature was not affected by air temperature or forced ventilation but increased by .02 degrees C/kg fat-corrected milk in animals producing above 24 kg/day. Between 26 and 36 degrees C rectal temperature increased with air temperature in both groups; rate of rise was halved by forced ventilation. In this range of air temperature, rectal temperature increased with rising milk yield, as in the lower air temperature range, in both high-producing and lower-producing cows in forced ventilation. Body weight or parity did not have significant effects. Mean ear skin temperature was higher for control animals, but its rate of increase with air temperature was similar in both groups. Forced ventilation reduced mean respiratory rate. An upper critical temperature is 25 to 26 degrees C and is independent of milk yield or acclimatizational state of cows exposed to the natural sequence of climate.

Physiological and behavioural response of two dairy cows’ genotypes during summertime in the central region of Chile

“…The differences in RR herein presented as well as those reported by Bouraoui et al (2002), and by Muller et al (1994) suggest that cows were primarily subject to heat stress during those hours of the day when AT and SR reach maximum values, resulting in significant increases of RR. Thus, SR and AT are two important drivers and triggers of RR (Berman et al 1985, Harris et al 1960. The RR can be used as a valuable tool to assess the level of heat stress on cows.…”

Review: Milking robot utilization, a successful precision livestock farming evolution

“…Temperature can have a dramatic effect on cow activity, dry matter intake and milk production (West, 2003) and therefore on the voluntary traffic of cows. The suggested threshold at which Holstein-Friesian cows begin to suffer from heat stress is~25°C ambient air temperature and above this point, measures should be put in place to reduce cow body temperature (Berman et al, 1985). One of the first attempts to combine AMS with grazing located the robot in a temporary structure, with the cows observed returning to the structure for shade and water .…”

Alterações celulares induzidas pelo estresse térmico em embriões bovinos

“…A seleção genética de vacas Holandesas de alta produção de leite está associada ao aumento na quantidade de calor metabólico (BERMAN et al, 1985;MAR-TELLO et al, 2004). West (2003) verificou que vacas em lactação produzem uma grande quantidade de calor metabólico e que, adicionalmente, acumulam calor de energia radiante.…”