Study On The Energy Nutrition Requirement And Metabolism Rules In Yak During Pregnancy And Lactation

In this paper the experiment methods of feeding experiment,digestion and metabolism,gas carbon metabolism and nitrogen balance used to to study the digestive metabolism and nutrient requirements of yak during pregnancy and lactation.In this way,that probably provided scientific basis data for supplement the yak nutritional requirement of basic parameters,improve the yak breed standard database and guidance the moderate feeding technology of yak dams during breeding.Paper main research results are as follows:Experiment 1 Study on the energy nutrition requirement and metabolism rules in yak during pregnancyPregnancy yaks with 15 similar parity,estrus treatment and mating were randomly divided into 3 groups,namely,ad libitum（AL）,80%ad libitum（IR80）and60%ad libitum.（IR60）,5 in per group,1 in per repetition.During the test period of218 days,three yak were selected from the three groups of 180d and 210d for digestive metabolism test and gas metabolism test.The feces and urine were collected,and the nutrient digestibility（dry matter,organic matter,neutral detergent fiber and acid detergent fiber）,energy metabolism indexes（total energy,fecal energy,urine energy,methane energy）and nitrogen deposition（Intake nitrogen,fecal nitrogen,urine nitrogen）and carbon metabolism indicators（feeding carbon,fecal carbon,urinary carbon,methane carbon,carbon dioxide carbon）were measured,to explore the energy digestion and metabolism of yak under different feeding levels,obtain the metabolic energy intake and energy deposition of yak during pregnancy,and establish the regression equation to determine the energy maintenance requirement.The results are as follows:1)The apparent digestibility of indicators such as dry matter,organic matter,neutral detergent fiber and acid detergent fiber increased with the decrease of feeding level,but the difference was not significant.2)With the feeding level decreased,the indexes of nitrogen,fecal nitrogen and nitrogen deposition decreased,and urinary nitrogen increased with the decrease of feeding level.3)The total energy digestibility rate and total energy metabolism rate ranged from 55.00%to 59.72%,44.83%to 55.37%,and 81.53%to 96.96%,respectively.The rate of digestive energy decreased with the increase of feeding level,but there was no significant change.4)The respiratory entropy（RQ）was between 0.69 and 0.73,and C was apparently digested.The rate was between 47.33%and 61.26%,and the apparent digestibility of RQ,CH4-C,and C decreased with the decrease of feeding level.5)The metabolic energy maintenance required for pregnancy 180d and 210d was 438.81k J/kg W^0.75?d^-1 and 541.64 k J/kg W^0.75?d^-1,the metabolic capacity of yak is gradually increased as the gestation period is extended.Experiment 2 Study on the energy nutrition requirement and metabolism rules in yak during Lactation15 yaks were randomly divided into 3 groups 30 days after delivery,namely,free-feeding group（AL）,80%free-feeding group（IR80）and 60%free-feeding group（IR60）,5 in per group,1 in per repetition.The test period was 158 days.Three yak were selected from each group at 65 and 120 days of lactation for digestive metabolism test and gas metabolism test.The feces and urine were collected,and the nutrient digestibility（dry matter,organic matter,neutral detergent fiber and acid detergent fiber）,energy metabolism indexes（Total energy,fecal energy,urine energy,milk energy,methane energy）and nitrogen deposition（intake nitrogen,fecal nitrogen,urine nitrogen,milk nitrogen）and carbon metabolism indicators（feeding carbon,fecal carbon）,urine carbon,milk carbon,methane carbon,carbon dioxide carbon)were measured,to explore the energy digestion and metabolism of yak under different feeding levels,obtain the metabolic energy intake and energy deposition of yak during pregnancy,and establish the regression equation to determine the energy maintenance requirement.The results are as follows:1)The apparent digestibility of DM,OM,NDF,ADF and other indicators of yak lactation was not significantly correlated with feeding level.2)With the reduction of feeding level,the indexes of nitrogen,fecal nitrogen,milk nitrogen and sediment nitrogen in the yak lactation decreased,and the urinary nitrogen increased with the decrease of feeding level.3)The total digestibility,total energy metabolism rate and digestible energy metabolic rate of yak during lactation ranged from 64.36%～77.01%,38.14%～53.34%,and44.15%～74.20%,respectively.4)The yak RQ is between 0.70～0.74 in lactation,and the apparent digestibility of C is between 65.60%～70.72%,and RQ decreases with the decrease of feeding level.5)The metabolic energy requirement of yak lactation at 65d and 120d is 512.88 k J/kg W^0.75?d^-1 and 491.64 k J/kg W^0.75?d^-1,with the prolonged lactation period,the metabolic capacity of yak is gradually reduced.