Effect Of Different Diet Energy And Protein Level On Milk Performance And Composition In Xinong Saanen Dairy Goats

In order to sift the best energy and protein level of lactation Xinong Saanen Dairy Goatdiet,36dairy goats with similar body weight(50.56±0.76kg), parity（2-3）, delivery date, milkyield（2.12±0.10kg/d） and body condition were randomly divided into6groups accordingto3×2random block experimental design.These goats were fed low energy low proteindiet(Group LL), low energy high protein(Group LH), medium energy low protein(Group ML),medium energy high protein(Group MH), high energy low protein(Group HL), high energyhigh protein(Group HH) respectively.6goats were fed in each group in similar condition. Thewhole experiment phase was98days containing14days pre-feeding period.The samplesfrom each group were collected according to the design to analyse the effect of differentenergy and protein level diets on DMI, milk yield,milk composition,blood indexs and rumenpH. The results showed that:1. There was no significant effect on DMI by different energy level, while the dairygoats showed a decrease trend with the increase of diet protein level(P>0.05). In conclusion,Group LH and Group HL took higher DMI indexs, and the DMI showed a increasing and thendecreasing trend in every group.2. There was no significant effect on milk yield by different energy and protein leveldiets(P>0.05), althrough there was a increase trend with the increase of nutrition level. Whilethe milk yield showed first decreased and then increased trend under low protein level diet,the high protein level diet got a constant increase trend. High protein diets showed highermilk yield(P>0.05). In conclusion, Group HH got the highest milk yield, and Group MLobtained the least.3. There was no significant effect on milk fat by feeding with different energy andprotein level diets, and there was no obvious difference between every group, Group HHobtained the least milk yield. Diet energy level had no significant effect on milk proteinalthrough high protein goats got lower milk protein level. Take both protein and energy intoconsidered, the milk protein change obviously among different periods with no regularity.Group ML and HH got the highest and lowest milk protein. There were also no significanteffect on milk lactose, dry matter, somatic number et.al by different diets except for adecrease trend on SNF.4. Different energy and protein level diets had no significant effect on TC, TP, ALB, BUN and TG in goat blood. All the blood indexs were in normal levels. Under a same proteinlevel diet, TP concentration was increased gradually with the increase of energy level(P>0.05).Medium energy diet got a higher ALB concentation, high energy diet got higher TC and TG,low energy diet got higher BUN concentration. Under a same energy level diet, higher proteindiet got higher TP and ALB, low protein diet got higher TC, TG and BUN.5. Under a same protein level, pH of rumen decreased significantly with the increase ofenergy level(P<0.05) in period3. Under a same energy level, pH had no significant changeamong different groups(P>0.05). Group ML and HH got the highest and lowset pHrespectively. The result of pH of5times showed that there were no significant change amongdifferent energy levels but a decrease trend with the increase of protein level. pH decreasedgradually untill4h in which point the Group MH goats got the lowest pH. All the pH indexswere in normal field (5.5-7.5). In conclusion, pH droped down sharply to2h after feeding bywhich followed a lightly increase to a little lower level at8h comparion with the originalstatus.