Access to shade changes behavioral and physiological attributes of dairy cows during the hot season in the subtropics

Abstract

The effect of shade on behavior and physiological attributes of grazing cows in a high altitude subtropical zone is not well established. This work aimed to investigate how social and ingestive behaviors, as well as physiological and other attributes of dairy cows such as milk production, change in a subtropical environment during the hot season either with or without free access to shade. Fourteen lactating cows were kept on pasture either with no shade or with free access to shade for 5 days and their behavior was recorded with instantaneous scan sampled every 10 min, from sunrise, 0530 h (Greenwich mean time, GMT − 0200 h) to sunset, 2100 h (GMT − 0200 h). Behavior traits included (1) time spent in activities such as grazing, ruminating, resting, lying, standing, walking, seeking shade and staying in the proximity to the water trough and (2) number of events such as water ingestion, aggressive interactions, as well as competition for shade and water. Physiological attributes such as heart and respiratory rates, rectal temperature, number of rumen movements, panting score, as well as milk yield, were evaluated. Time spent in behavioral activities, number of behavioral events and physiological attributes varied between groups (with and without access to shade). Cows with no shade showed increased respiratory and heart rates and panting score at 1300 h, higher values for time of permanence near the water trough, number of competition and aggression events for shade. On the other hand, they showed lower values for time spent resting while lying, ruminating while standing, seeking shade. Access to shade did not change time spent lying, standing, walking with the head up, ruminating while lying, resting while standing, as well as milk yield and number of ruminal movements. Significant interactions between access to shade and days of measurements were detected for time spent walking, ruminating, grazing, resting, number of water ingestion events, competition events near the water trough and for shade, as well as for rectal temperature and panting score measured at 1700 h. In the high altitude subtropical region, access to shade minimizes negative heat stress effects on behavior and physiological aspects of dairy cows.

Variation in available shaded area changes behaviour parameters in grazing dairy cows during the warm season

“…In the present study, the increased proportion of time spent standing up of the SH2 group compared with SH10 is probably linked to the attempt to increase body surface exposed to air and facilitate heat dissipation (Palacio et al, 2015), as SH2 cows spent less time in shade and were exposed to solar radiation during an extended time compared with SH10 cows, confirming previous results of Schütz et al (2010) and of Vizzotto et al (2015), who reported that cows without access to shade increased time spent standing compared with those with access the shaded area. Kendall et al (2006) evaluated the behaviour of dairy cows with 1.8 m² of shade or without shade and also noted the preference of cows to remain standing in the shade.…”

“…Our results agree with those reported by Schütz et al (2010), in which cows with access to 9.6 m 2 of shade per cow spent more than twice as much time in the shade than cows with 2.4 m 2 of shade per cow. Previous studies evidenced that during the warm season, lactating dairy cows seek shade (Schütz et al, 2008(Schütz et al, , 2010(Schütz et al, , 2014Vizzotto et al, 2015).…”

“…Dairy production systems based on grazing can help the health and welfare of animals, as well as improve the public perception of the dairy sector (Ventura et al, 2016). However, during the warm season and especially when shade provision is not adequate, animals may be exposed to heat stress (Kendall et al, 2006), triggering changes in social and feeding behaviours (Fisher et al, 2008;Schütz et al, 2010;Vizzotto et al, 2015) as well as in physiological attributes (Van Laer et al, 2015a), milk yield (Kendall et al, 2006;Van Laer et al, 2015b), and milk composition (Van Laer et al, 2015a).…”

Technical note: Using an electronic drinker to monitor competition in dairy cows

“…Drinkers may also be useful for monitoring social competition. During periods of elevated ambient temperature when cows increase water intake and decrease feed intake (Kadzere et al, 2002), aggressive interactions are high (Coimbra et al, 2012), resulting in more competition at and close to the water source (Vizzotto et al, 2015). Especially during heat stress, water is an important resource for dairy cows, and competition can result in dominant animals preventing subordinate animals from access (Coimbra et al, 2012).…”

“…Two of the observation periods were assigned as the baseline set (mean ± SD ambient temperature = 18.9 ± 3.8°C; range = 12.9-25.4°C) and used to identify the optimal interval; the 2 other periods were assigned as the validation set (mean ± SD ambient temperature = 20.5 ± 4.7°C; range = 13.9-29.3°C) and thus used to validate the interval. As elevated ambient temperatures affect competitive behavior at the drinker (Vizzotto et al, 2015), the 24-h observation periods were assigned to either the baseline set or the validation set based on mean daily temperature. The baseline set comprised the more moderate 2 d (mean ± SD ambient temperature = 18.3 ± 3.9 and 19.5 ± 3.7°C for baseline set periods 1 and 2, respectively), and the validation set comprised the warmest and coolest days (mean ± SD ambient temperature = 24.0 ± 3.6 and 16.9 ± 2.2°C for validation sets 1 and 2, respectively).…”