Study On Energy And Protein Requirements For Lactation Of Poll Dorset And Thin-tailed Han Crossbred Ewes

Fifteen lactating ewes were assigned into three groups according to body weight utilizing randomized block design, in which ewes were fed under conditions of ad libitum,80% and 60% dietary restriction, with five ewes in each group. Digestion and metabolism, gas metabolism experiment were performed at 15, 45 and 75 days of lactation, respectively, to determine the energy and protein metabolic level and requirements, finally, which got the requirements factorial models of Dorset and Thin-Tailed Han crossbred ewes during lactation. The results showed that:1.The dry matter intake, fecal output, nitrogen intake, fecal nitrogen, carbon intake, fecal carbon, digestible carbon, energy intake, fecal and urine energy, digestible energy, metabolic energy, metabolic weight and dry matter intake/metabolic weight of ewes increased with decreasing levels of feed intake, and the ad libitum group was significantly higher than the 60% dietary restriction group(P<0.05). The apparent digestibilities of nitrogen, carbon, energy and oxygen consumption/metabolic weight and CO2 output/ metabolic weight decreased with decreasing levels of feed intake. With the lactation progressed, nitrogen and carbon in milk decreased, and which in early lactation was significantly higher than late lactation(P<0.05).2.The NEm at early, middle and late lactation for Poll Dorset and Thin-Tailed Han crossbred ewes was 226.14, 318.15 and 303.77 k J/kg W0.75·d, respectively. The MEm was 327.06、318.15 and 303.77 k J/kg W0.75·d at early, middle and late lactation respectively. The net protein requirements for maintenance of ewes was 2.25, 2.01 and 1.76 g/kg W0.75·d at early, middle and late lactation respectively.3.The NER, MER and NPR of lactation for Poll Dorset and Thin-Tailed Han crossbred ewes can be estimated by the factorial models as follows:The NER factorial models as follows:Early lactation: NER=226.14 k J/kg W0.75·d +NEg;log10ER=3.1206+0.4658log10BWMiddle lactation:NER=223.83 k J/kg W0.75·d +NEg;log10ER=3.0815+0.4602log10BWLate lactation: NER=221.72 k J/kg W0.75·d +NEg;log10ER=2.8349+0.5594log10BWThe MER factorial models as follows:Early lactation: MER=327.06 k J/kg W0.75·d +NEg/0.7327;log10ER=3.1206+ 0.4658log10BWMiddle lactation: MER=318.15 k J/kg W0.75·d +NEg/0.7591;log10ER=3.0815+ 0.4602log10BWLate lactation: MER=303.77 k J/kg W0.75·d +NEg/0.8317;log10ER=2.8349+ 0.5594log10BWThe NPR factorial models as follows:Early lactation:NPR=2.25g/kg W0.75·d+Npg; log10NR=-2.7775+2.2807log10BW; NR=-9.6915+ 0.0925NPgMiddle lactation:NPR=2.01 g/ kg W0.75·d + Npg; log10NR=-2.0667+1.851log10BW; NR=-9.8755+ 0.094NPgLate lactation:NPR=1.76 g/ kg W0.75·d + Npg; log10NR=-1.4648+1.4933log10BW; NR=-11.775+ 0.0961NPg4. Energy and protein requirements for lactation of ewes were presented.