THE EFFECT OF DIET IN LATE PREGNANCY ON COLOSTRUM PRODUCTION AND IMMUNOGLOBULIN ABSORPTION IN SHEEP

One hundred and twenty-six twin-bearing ewes were given either formic acid (FA) treated grass silage or grass/molassed sugar-beet pulp (MSBP ) silage in order to investigate factors affecting colostrum yield and quality and the efficiency of immunoglobulin (IgG) absorption. The ex periment commenced on day 91 of pregnancy and the diets consisted of F A-treated silage (T1), FA-treated silage + soya-bean meal (SB) (T2), M SBP silage (T3), MSBP silage + SE (T4), FA-treated silage + MSBP (T5), FA-treated silage + MSBP + SB (T6) or FA-treated silage + 150 g/kg of a crude protein concentrate (T7). Soya-bean meal was offered only in the last 3 weeks of pregnancy aiming for a total crude protein intake of 220 g per ewe per day. Blood samples were taken from lambs in order to measure serum Ig concentrations. Ewes were milked at 1 h, 10 h and 18 h post lambing. Daily metabolizable energy intakes of 6.8, 11.4, 9 .6, 12.8, 10.5, 13.7 and 14.7 (s.e. 0.58) MJ per ewe were recorded for T1 to T7 respectively over the last 3 weeks of pregnancy. Respective crude protein intakes of 72, 213, 110, 225, 109, 215 and 175 (s.e. 5.6 4) g per ewe per day were recorded for T1 to T7 over the last 3 weeks of pregnancy. The addition of protein increased colostrum yield at 1 h (P < 0.01), 10 h (P < 0.01) and 18 h (P < 0.01) post lambing and tota l yield of colostrum to 18 h (P < 0.001). There was no significant res ponse (P > 0.05) in colostrum production during the first 18 h followi ng protein supplementation when the basic diet was FA-treated silage. There was no difference (P > 0.05) in colostrum production during the first 18 h between ewes offered MSBP treated silage or MSBP supplement ed silage. Ewes offered FA-treated silage production less colostrum du ring the first 18 h compared with ewes offered either MSBP treated or supplemented silage (P < 0.05). The production of colostral IgG during the first 18 h after parturition was related to the amount of colostr um produced; the greater the colostrum production the greater the Ig p roduction. There was a significant quadratic relationship between the total amount of IgG ingested per kg lamb birth weight during the first 18 h and lamb serum IgG at 24 h (R(2) = 0.4005; P < 0.0001). Lamb ser um Ig level increased linearly with increasing colostrum IgG consumpti on up to 15 g/kg lamb birth weight. Proportionately about 0.17 of the IgG ingested was present in the lamb's circulation at 24 h. Ewe protei n supplementation pre-lambing increased the lamb's efficiency to absor b colostral IgG (P < 0.05) during the first 24 h. In conclusion, the d ata shout positive relationships between feeding regimes, colostrum pr oduction and IgG transfer.