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Adaptive management of small ruminants under grazing conditions to climate change

A study is in progress to identify the physiological indicators of stress in grazing small ruminants and to develop consolidated adaptation strategies under grazing conditions. Thirty six Nellore ewes (22.8 ± 2.86 kg) were randomly divided into two comparable groups with eighteen animals in each group and exposed to heat stress during April to June by allowing for grazing for 6 hrs (0800-1200hrs and 1600-1800hrs) and assessed the impact of fortified concentrate supplementation in enhancing fertility in ewes and birth weight and growth rate of lambs (from birth to weaning at 90 days of birth) and reducing mortality rate of lambs born. Data from automated weather station located at HRF was used for development of heat load index (HLI) during March to June.

 

The mean maximum ambient temperature and HLI ranged from 27.0 to 43.8°C and 73.1 to 90.6, respectively during March to June months. HLI was above 80 except for a few days in April, and reached 90 during May indicating heat stress on grazing animals during April to June months. The body temperature and rectal temperature of Nellore ewes gradually increased as HLI increased from morning to noon and decreased in the evening. A similar trend was observed in respiration and pulse rate in all the animals. However, the increase in body and rectal temperature was relatively higher in May and June compared to April month and significantly lower (P<0.05) in animals that received fortified concentrate mixture. A similar trend was observed in respiration and pulse rate of animals. Significantly higher average birth weight was observed in lambs of ewes fed with fortified concentrate. Weight at weaning and average daily gain (ADG) were also higher (P<0.05) in lambs of ewes fed with fortified concentrate. Fertility and fecundity rates were higher and mortality of lambs was lower in ewes fed with fortified concentrate. The results of the study indicate that supplementation of fortified concentrate could mitigate the adverse affects of heat stress in grazing ewes exposed to solar radiation.


Heat Load Index and Maximum Day Temperature (°C)
during March to June,2015

Effect of exposure to heat stress on reproductive
performance of ewes and mortality of offspring

   
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