Study On Energy Requirements Of Multifarious Suffolk Sheep During Growing Period (20～35 Kg)

The problem of poor growth performance or waste of feed resources caused by nutritional supply failing to meet the needs of meat sheep in China’s meat production is very prominent,and this situation is not in line with the goals of profit maximisation,cost minimisation and ecological optimisation in modern animal husbandry.The nutritional requirements of meat sheep are the theoretical basis and guidelines for the design of meat sheep feed formulations,which are of great significance for the rational use of feeds to fully improve the performance of meat sheep,reduce feeding costs and improve agricultural economic benefits.Objective:The aim of this study was to develop a series of analytical models for the energy requirements of multiparous Suffolk sheep from 20～35 kg,to systematically derive parameters for the net and metabolic energy requirements of multiparous Suffolk sheep from 20～35 kg,and to provide basic data for the development of nutritional standards for multiparous Suffolk meat sheep.Methods:Multiparous Suffolk rams and ewes at 3 months of age were used as test animals on a diet based on the nutritional requirements of the NY/T816-2004 Standard for the Feeding of Meat Sheep with a daily weight gain of 300 g·d^-1for growth studies,digestion and metabolism studies and comparative slaughter studies.The diets were formulated by combining.The study was carried out on growth performance,slaughter performance,digestive system,tissue and organ development of multiparous Suffolk sheep using a combination of growth tests,digestive metabolism tests and comparative slaughter tests.A series of analytical models of energy requirements were developed by dissecting the relationships between energy intake,excretion and deposition in the test sheep.Results:1.With increasing feeding levels,daily weight gain,dry matter intake,fasting weight and carcass weight of 20～35 kg multiparous Suffolk sheep increased significantly;in the ad libitum state,rams and ewes with ME of 11.62 kJ·kg^-1and 10.36 kJ·kg^-1,respectively,and CP of 16.80%and 16.45%,respectively,could achieve daily weight gain of 277 g·d^-1and 238 g·d^-1for rams and ewes,respectively.With higher feeding levels,the development of the first three gastric compartments,especially the rumen,was significantly enhanced in 20～35 kg multiparous Suffolk sheep.Restricted feeding reduced the weight of some internal organs.2.Apparent digestibility of major nutrients was higher in restricted rams than in restricted ewes,but energy stores were lower in restricted rams and ewes.low feeding levels had a significant effect on total energy expenditure in multiparous Suffolk sheep weighing 20～35 kg,with the metabolic energy of rams in the restricted group being 1.13 MJ·kg^-1higher than in restricted ewes.3.At the same weight stage,the total fat energy value of ewes in the restricted feeding group was higher than that of rams by 28.99 MJ;the proportion of energy content of different tissues to total body energy was influenced by the feeding level,with the highest proportion of energy in bones to total body energy in the maintenance needs group,27.60%and 21.18%for rams and ewes respectively.Conclusion:The net maintenance energy and metabolic energy requirements of 20～35 kg multiparous Suffolk rams and ewes were 274.599 kJ·kg^-1SBW^0.75,239.166 kJ·kg^-1SBW^0.75and 398.199kJ·kg^-1SBW^0.75,378.076 kJ·kg^-1SBW^0.75,respectively,and the metabolic energy maintenance efficiency was 0.68 and 0.63,respectively.The metabolic energy maintenance efficiency was 0.68 and 0.63,and the net energy requirement for growth was 4.32 MJ·d^-1and 4.43 MJ·d^-1for 30 kg daily gain 300 g multiparous Suffolk rams and ewes,respectively,with metabolic energy growth utilization efficiencies of 0.458 and0.488,respectively.Factorial model of net energy and metabolizable energy requirements of rams:NER=274.599 kJ·kg^-1SBW^0.75+NEg;MER=398.199 kJ·kg^-1SBW^0.75+NEg/0.458;Ewe net energy and metabolizable energy requirement factorial model:NER=239.166 kJ·kg^-1SBW^0.75+NEg;MER=378.076 kJ·kg^-1SBW^0.75+NEg/0.488.