Changes in energy expenditure by meat goats with varying levels of feed intake near maintenance and below

Abstract

Eleven yearling meat goat wethers (718 Boer and 1/8 Spanish) were used in a 16-week experiment to determine effects of different levels of nutrient restriction and a maintenance level of intake after a severe restriction on energy expenditure (EE). Dehydrated alfalfa pellets were fed throughout the experiment. During the first 4 weeks for adaptation, wethers were fed near maintenance. In weeks 5 to 10, six wethers were fed at approximately 60% of the maintenance level and in weeks 11 to 16 were again fed near maintenance (L-H). The other five wethers were fed at approximately 80 and 60% of maintenance in weeks 5 to 10 and 11 to 16, respectively (M-L). Body weight and EE were measured on the last day of most weeks, with EE determined from heart rate and the previously determined ratio of EE to heart rate for each wether. Body weight differed among weeks but not between treatments (41.0, 41.5, 39.7, 39.5, 38.0, 37.2, 38.0, 37.5, 37.8, 38.8 and 30.3 kg for L-H (SE=1.29) and 38.6, 38.2, 37.2, 37.2, 36.6, 35.0, 36.6, 36.7, 35.9, 35.7 and 36.9 kg (SE=1.41) for M-L in wk 4, 5, 6, 7, 9,10,11, 12,13,15 and 16, respectively). Energy expenditure, expressed relative to BW at the end of the adaptation period, was 362, 366, 322,280,262,260,259, 331, 331 and 335 kJ/kgBW0 75 (SE=11.4)for L-Hand 342, 378, 306, 301, 282, 276, 288, 263, 253 and 254 kJ/kg BW0 75 (SE=14.8) for M-L in weeks 4, 5, 6, 7, 9, 10,11,12,13 and 15, respectively. Retained or recovered energy was different (P<0.05) from 0 for L-H in weeks 4, 5, 6,11,12,13 and 15(65, -101, -56, -14, 4, 6,192,120,121 and 117kJ/kg week 4 BW075; SE=15.7) and for M-H in weeks4, 5, 9 and 10 (92, -47, 25, 29, 49, 55, -14,11,21 and 20 kJ/kg week 4 BW0 75 in weeks 4, 5, 6, 7, 9,10,11,12,13 and 15, respectively; SE=17.3). In conclusion, meat goats can markedly reduce EE in response to limited feed intake, with nonlinear change as time advances. © GSP, India.