The Study Of The Effect Of Feed Restriction During Late Pregnancy On The Lamb Birth Weight Of Sunit Ewes And The Mechanism Involved

In this study, based on the fact that 70-80% of the growth of the fetuses occurred in the last two month of pregnancy, forty -five sunit pregnant ewes in their second or third parity of average body weight 41.45+3.8kg and moderate body condition on their 90th day of pregnancy were randomly allocated to four dietary treatments during late pregnancy (90-150) (13-0.20, 12-0.33, 9-0.44 and 11-0.86 MJME kg-1 w d-1) with the aim of studying the effect of different restricted feeding energy levels during late pregnancy on the lamb birth weight of sunit ewes . The results were as follows:1 Feed restriction during late pregnancy did have effect on the lamb birth weight of sunit ewes.2 During late pregnancy, sunit ewes with moderate body condition on day 90 of pregnancy had much potential to mobilize body reserve to make good the exogenous nutrients deficiencies and the ewes could adapt to lower nutrition well.3 During late pregnancy(90-150), on condition that the body condition of the ewes on their 90th day of pregnancy was moderate, the lower plane of nutrition of 0.33MJ, 3.2g/kg w/d (about 600-700g pasture hay used in this study) had no detrimental effect on the growth and development of the fetuses and therefore the corresponding lamb birth weight was not reduced.4 During feed restriction, the serum insulin concentration of the ewes in G1, G2 tended to decrease and the serum T3, T4 concentration of the ewes in GK G2, G3 or G4 were decreased within the last 1 month of pregnancy .5 During feed restriction period, the ewes in GK G2, G3 or G4 showed different negative nitrogen balance, apart from the ewes in G3,the ewes in G1, G2, G4 showed different negative calcium balance ,and the ewes in G1, G2, G3 or G4 showed different positive phosphorus balance.6 with the feeding energy level increased from Gl to G2, G3, G4, thedigestibility of ADF or NDF decreased.