Thermography and physiology of stress in dairy calves in outdoor holding pens covered with geosynthetics

Abstract

This study aimed to assess the environmental variables, thermal comfort indices and physiological responses of calves in outdoor holding pens shaded with geosynthetics. Twenty crossbred females (Giroland, Jersey and Holstein) in the suckling phase (from birth to 90 days old) with an average initial live weight of 40.6 kg were used. A completely randomized block design was used, in a 4 × 3 factorial scheme with five replicates. The roofing materials (polyethylene mesh, geocomposite drainage layer, nonwoven geotextile and woven geotextile) were the first factor and time periods (8 to 10 a.m., 12 to 2 p.m. and 4 to 6 p.m.) the second factor. The following environmental variables were measured to calculate thermal comfort indices: temperature-humidity index, black globe-humidity index and enthalpy. The physiological variables analyzed were respiratory rate, rectal temperature and skin temperature. Environmental variables and thermal comfort indices did not differ between the different roof types, however, a significant difference (p ≤ 0.01) was observed between the time periods, with 12 to 2 p.m. being the most critical period. The lowest average respiratory rate (60.3 breaths min-1) and rectal temperature (38.9 °C) were recorded for the animals kept under the geocomposite drainage layer roof. There was a significant difference (p ≤ 0.05) for interaction between treatment and time periods for the cannon area. The geosynthetics studied can be used as roofing material for outdoor holding pens, with the geocomposite drainage layer being the most indicated for tropical regions.

Behavioral changes in dairy calves raised in outdoor holding pens with alternative roofing

“…Climate in the region is classified as Aw (wet tropical, with a rainy summer and dry winter) according to the Köppen classification system. As described by Campos, Passini and Nascimento (8) , average annual temperature and rainfall are 23.1°C and 1,355 mm. The study was carried out in summer, from February 26-28 to March 2-3, 2017.…”

“…The project was approved by the Animal Ethics Committee (CEUA) of Goiás State University on June 12, 2017, under protocol number 002/2017. Twenty crossbred (Girolando, Jersey and Holstein) dairy calves were used, with an average initial weight of 40.6 Kg during weaning, which ended at 90 days old (8) .…”

“…A completely randomized block design was used (animal age difference of 0 ± 5 days), as described by Campos, Passini and Nascimento (8) , in a 4 x 3 factorial scheme, with 5 repetitions. The roofing materials were polyethylene mesh, drainage geocomposite, nonwoven geotextile and woven geotextile, representing the first factor, and times of day (8 to 11 a.m., 11:15 a.m. to 2 p.m. and 2:15 to 6 p.m.) the second factor.…”

“…The 4 North-South facing (8) covered holding pens (1 per treatment) were 19 m long, 2 m wide and 1.55 m high, installed 3 meters apart in a pasture planted with Cynodon dactylon cv. Vaquero.…”

“…Each pen housed five calves whose collars were attached to a wire rope close the ground, allowing them to move freely in a 12 m straight line (8), The animals had access to shade throughout the day as well as a covered trough and buckets of fresh water and milk (Figure 2). Their diet consisted of milk replacer, water and concentrated feed, as described by Campos, Passini and Nascimento (8) . The milk replacer was offered in individual buckets, twice a day, in the morning (8:30 a.m.) and afternoon (3:30 p.m.), totaling 6 liters a day.…”