D. L. Verma

Effect of season on thermoregulatory responses and energy expenditure of goats on semi-arid range in India

A study of the physiological responses and energy expenditure of goats was carried out from June 1999 to May 2000 by conducting two experiments: one on bucks maintained on stall feeding in autumn 1999 (Expt 1) followed by year-round grazing on native ranges over three seasons: monsoon, winter and summer (Expt 2). Physiological responses and energy expenditure (EE) measurements of housed and grazing goats were recorded at 06.00 h and 14.00 h for 5 consecutive days in each season. Goats were fixed with a face mask and meteorological balloon for collection of expired air and measurement of EE. Respiration rate (RR) at 06.00 h was similar in all seasons (14 respiration/min) except in the monsoon, where a significantly (P < 0.05) higher value (26 respiration/min) was recorded. At 14.00 h, RR was higher in monsoon and summer (81 and 91 respiration/min) than in winter (52 respiration/min). Irrespective of the season, heart rate (HR) was higher at 14.00 h (86 beat/min) than at 06.00 h (64 beat/min). The rise of rectal temperature (RT) from morning (06.00 h) to peak daily temperature (14.00 h) was 0.9 °C in housed goats in autumn and 1.0, 2.1 and 2.0 °C in grazing goats during monsoon, winter and summer, respectively. The mean value was 1.7 °C. Skin temperature (ST) was lowest in winter (30.1 °C) and highest at 14.00 h in summer (40.3 °C). Energy expenditure of goats at 06.00 h was 32.7 W in winter and significantly (P < 0.05) increased to 52.0 W in summer and 107.8 W in monsoon. At 14.00 h, EE was 140.2 W in winter and increased to 389.0 W and 391.3 W respectively in monsoon and summer. It is concluded that monsoon and summer are both stressful seasons in semi-arid regions. Animals should be protected from direct solar radiation during the hottest hours of the day to ameliorate the effect of heat stress.

Seasonal changes in nutrient intake and its utilization by range goats in a semi-arid region of India

This study was carried out from September 1998 to August 1999, by conducting three experiments, one each in the monsoon, winter and summer seasons. The forage availability and botanical composition of native range were obtained. Five 3–4-year-old Kutchi males, weighing 50–55 kg, were used to determine total faecal output, and were observed to allow the diet selected to be sampled by the hand plucking method. Dry matter (DM) yield of range was highest during winter and lowest during monsoon, annual mean being 1611 kg DM/ha. Contribution of shrub foliage to total forage yield in monsoon, winter and summer was 3·81, 1·64 and 9·98%, respectively. Crude protein (CP) content (g/kg DM) of ground vegetation declined from 99 in monsoon to 72 in winter and 66 in summer, while that of top foliage remained similar in all the seasons (mean CP 142 g/kg). Goats consumed a diet of almost the same CP content (mean CP 137 g/kg) in all the seasons. Goats consumed 64·0, 54·0 and 55·9 g DM/kg W 0·75 /day, in monsoon, winter and summer (annual mean 58·0 g DM/kg W 0·75 /day). DM and CP digestibility coefficients were higher in monsoon and summer (mean DM 0·595; CP 0·533) and decreased ( P < 0·05) in winter (DM 0·485, CP 0·424). Neutral detergent fibre (NDF) and acid detergent fibre (ADF) digestibility coefficients were highest in monsoon (NDF 0·542; ADF 0·446), and declined ( P < 0·05) to 0·340 and 0·266 in winter and 0·415 and 0·326 in summer. Digestible crude protein (DCP) intake was almost similar in monsoon and summer (mean 4·6 g/kg W 0·75 /day) and declined ( P 0·75 /day), while metabolizable energy (ME) intake was higher in monsoon (0·90 MJ/kg W 0·75 /day) and declined ( P 0·75 /day, in winter and summer, respectively. Average body weight of goats in monsoon, winter and summer was 54·0, 54·6 and 56·5 kg, respectively (annual mean 55·0 kg). It is concluded that goats grazing on a semi-arid rangeland meet their DCP and ME requirement throughout the year.