Responses In Nutrient Utilisation Efficiencies Of Cattle And Sheep To The Quality Of Major Forages Cultivated In Hexi Corridor

The shortage of high-quality forage is one of the major limits to the development of ruminant agriculture,which results in animal production system has great dependence on cereal grain.Consequently,the high demand for grain leaded to great pressure on the agricultural production system and local ecological environment.The quality of forage directly affects nutrient utilization efficiencies,which finally affected concentrate input levels and feed cost.Promoting the healthy development of ruminant agriculture is based on improving the supply of good quality forage of cultivated grassland.The accurate determination of metabolisable energy requirement for maintenance?ME_m?has importantly instructive significance in sheep production.Based on this situation,in Hexi Corridor with a long history of introduction and cultivation of forage,the study explores the effects of 2 utility patters for barley,rye and wheat forage on rumen degradation parameters for cattle fed silage based diet,the effects of levels of alfalfa replacing concentrates on nutrient utilisation efficiencies for sheep fed diets based different forage quality,and determines the ME_m for sheep.The studies were carried out as the following:1)Effects of growth stage/regrowth stage on rumen degradation parameters for barley,rye and wheat used as forageEight fistulated Yunling×Yellow cattle with the age of 3 years old and the weight of 450±20 kg was used to a 4?4 group of samples?×2?2 experimental periods?incomplete Latin design for evaluating the effects of utility pattern?hay harvesting and mowing?and 5 growth stage/regrowth stage on rumen degradation parameters for barley,rye and wheat forage.Compared to hay harvesting,ED of DM,OM,DOM,CP,NDF and ADF,FOM and RDP for forage increased by 14.9,16.7,15.1,16.1,22.6,13.5,15.1 and 43.7%,respectively.For mowing treatment,ED for DM,OM and OM,and FOM decreased with an increase in regrowth stage;except in the 1^st regrowth stage affected by N fertilizer input before cutting,the ED for CP also declined;ED of DM,OM,DOM,NDF and ADF for rye was greater than those for barley and wheat,and there were no differences in ED for CP and RDP between 3 varieties.For hay harvesting,with delaying the harvesting date,a,a+b,c and ED of DM,OM,DOM,NDF and ADF linearly declined;ED for barley were significantly higher than those for wheat and rye.The optimal variety used for mowing is rye,and for hay harvesting is barley and wheat;the optimal growth stage is the early heading.After optimal growth stage,ED for DM decreases 8 g/kg DM with harvest date delayed per d.2)Effect of levels of using alfalfa hay as a substitute for concentrates on nutrient utilisation efficiencies and rumen fermentation for dry ewes fed diets based on maize stoverTwelve Hu sheep×thin-tail Han sheep crossbred dry ewes with an average BW of 32.6±0.68 kg and age of 3 years were arranged in a 3×3 Latin square design,with each experimental period of 24 d to evaluate the effects of substituting alfalfa hay in a portion of concentrate on nutrient intake,digestibility,N utilisation efficiency,CH₄emissions and rumen fermentation.The ratios of maize stover to alfalfa to concentrate for 3 diet treatments were 60:0:40,60:15:25 and 60:30:10,respectively.An increase in the levels of alfalfa as a substitute for concentrates significantly increased the roughage,NFC and ADF intake,and FN as a proportion of NI and MN.Furthermore,an increase in alfalfa input levels decreased DEI,MEI and NI;nutrient digestibility;DE/GE,ME/GE,CH₄ emissions per day;CH₄ output expressed as a portion of the DMI,OMI and GEI;UN,UN/MN and ammonia N output;acetate proportion and A/P,especially between extreme treatments.Alfalfa input levels had no effect on the BW,DMI and GEI;EB and EB/GEI;and RN.Alfalfa input increase relative abundance of Proteiniclasticum,but decreased the relative abundance of Ruminococcus₂.This study indicated that increasing alfalfa input as a substitute for concentrate could significantly decrease the digestibility,CH₄ emissions,and UN and NH₄⁺-N outputs;and shift the N excretion from urine to faeces;and could sustain a similar DMI.3)Effect of levels of using alfalfa hay as a substitute for concentrates on nutrient utilisation efficiencies and rumen fermentation for dry ewes fed diets based on fresh or dried rye forageTwelve Hu sheep×thin-tail Han sheep crossbred dry ewes with an average BW of 32.6±0.68 kg and an age of 3 years were arranged in 3 factorial design within 2experiments,to evaluate the effect of substituting alfalfa hay in a portion of concentrate on nutrient intake,digestibility,N utilisation efficiency,methane emissions and rumen fermentation.The ratios of rye forage?fresh or dried?to alfalfa to concentrate for 3 diet treatments were 60:0:40,60:15:25 and 60:30:10,respectively.The digestibility for AH15 was significantly higher than that for AH0 and AH30,and there was no differences between AH0 and AH30.An increase in alfalfa input,acetate proportion and A/P were significantly increased;but had no effect on CH₄ emissions,and utilisation efficiencies of N and energy.Compared to diets based dried rye forage,fresh rye forage diet had greater digestibility,EB,pH and acetate and propionate proportions,lower butyrate proportions and A/P and had the potential to reduce CH₄ emission.The15%alfalfa input diet and fresh rye forage diet had higher relative abundance of Firmicutes and Sporosarcina,respectively,than zero-alfalfa input diet and dried rye diet.The results implied alfalfa replacing 15%concentrates and rye forage fed at fresh could increase digestibility without an increase in CH₄ emission.4)Determination of maintenance energy requirement and effects of levels of alfalfa replacing concentrates on energetic efficiencies for dry ewes using calorimetry chamber dataData used were collected from 3 experiments with 81 dry ewes and fasting heat production?FHP?data with 45 dry ewes.The ME_m derived from the linear regression between EB and MEI,and FHP and MBW was 0.440 and 0.511 MJ/kg BW^0.75,respectively.The FHP was negatively related to EB/MBW,ME/GE,ME/DE,EB/GEI and EB/MEI,while positively related to HP/GEI,HP/MEI and CH₄-E/GEI.The 15%alfalfa hay input could decrease HP,but had no effects on EB or energy utilisation efficiencies,when compared to zero alfalfa input.The results indicated that some nutrient requirement standards currently used across the world may underestimate ME_m for dry ewes and selection of low FHP ewes could be a potential breeding strategy to improve production efficiency of sheep production.In conclusion,appropriate management strategies could increase available nutrient for small cereal forage.For sheep fed diets based maize stover or rye forage,it is feasible to use alfalfa as substitute for concentrate with equivalent amount,and 15%alfalfa input level is recommended with total forage proportion no more than 75%.For sheep fed rye forage-based diet,fresh rye forage diet could increase nutrient digestibility and has the potential to reduce CH₄ emissions.The ME_m obtained in present study was 0.440 or 0.511 MJ/kg BW^0.75,which has important guiding value in sheep production.