A. K. Shinde

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.

Seasonal changes in physiological responses and energy expenditure of sheep maintained on semi-arid pasture

A study on the energy expenditure of sheep was carried out at the Central Sheep and Wool Research Institute, India during August 1995 to July 1996 by conducting two experiments: one on tracheal cannulated rams maintained on stall-feeding in autumn 1995 (Expt 1) followed by year-round grazing on silvipasture (Cenchrus ciliaris pasture interspersed with fodder trees) over three seasons: monsoon, winter and summer, 1995/96 (Expt 2). Physiological responses and energy expenditure measurement of housed and grazing sheep were recorded at 06.00, 14.00 and 22.00 h for 5 consecutive days in each season. Tracheostomized sheep harness with meteorological balloon were used for collection of expired air and measurement of energy expenditure. Rectal temperature (RT) of sheep at 06.00 h was similar in all the seasons except for a significant (P < 0.05) lower value in monsoon. The rise of RT from 06.00 to 14.00 h in grazing animals was 1.6 °C, higher than that in housed sheep (0.9 °C). Skin temperature (ST) was least in winter and highest at 14.00 h in the monsoon and autumn seasons. Respiration rate (RR) showed a marked rise at 14.00 h in all the seasons. The heart rate (HR) of grazing sheep was higher, irrespective of season, at 14.00 h. At 06.00 and 22.00 h, the heart rate was higher in winter and summer than in the monsoon season. Overall energy expenditure (EE) was 4.85 MJ/24 h during winter which increased to 5.85 MJ/24 h in summer and 6.70 MJ/24 h in the monsoon. The mean rise in energy expenditure per °C rectal temperature in all the seasons was 338 kJ/kg W 0.75 . Comparable mean values per 10 °C ambient temperature and 10 °C black globe temperature were 404 and 173. The increase in energy expenditure of grazing compared to housed sheep in monsoon, winter and summer was 78, 15 and 33 % respectively. The mean value was +43%.

Dietary preference and grazing behaviour of sheep on Cenchrus ciliaris pasture in a semi-arid region of India

Dietary preference and grazing behaviour of male hoggets (6–8 months old) grazed on Cenchrus ciliaris pasture were continuously monitored from 08:30–17:30 h at weekly intervals from December to March. Population distribution (%) and preference index of Cenchrus ciliaris and Crotalaria burhia forb and dead litter were 21.11, 2.01; 6.31, 8.41 and 9.32, 1.60 respectively. Daily rhythmic periodicity in grazing pattern of hoggets was observed with two major periods of active grazing at 08:30–12:50 and 14:20–17:30. Increase in environmental temperature from December (20.6 °C) to March (31.2 °C) resulted in a decrease (P < 0.05) in the length of the grazing period from 8.36 to 7.40 h and an increase in the length of the resting period from 24 to 80 minutes. The study revealed that Crotalaria burhia needed to be protected in bush cleaning operations owing to its preference by sheep during summer. Furthermore, grazing periods of animals should be increased during the dry season in order to achieve optimal production.