PREPARTUM NUTRITION AND SOLAR-RADIATION IN BEEF-CATTLE .2. RESIDUAL EFFECTS ON POSTPARTUM MILK-YIELD, IMMUNOGLOBULIN, AND CALF GROWTH

Residual effects of nutrition and solar radiation during the last two- thirds of gestation on postpartum milk yield, immunoglobulin (Ig) G an d M in both colostrum and calf serum, and calf growth were determined in beef cattle. Nineteen mature, multiparous crossbred cows (Bos tauru s) at d 90 of pregnancy were assigned to either low (LO, 70% NRC total Energy intake) or high (HI, 110% NRC total energy intake) nutritional level (sudangrass hay) and to either shade (S) or no shade (NS) treat ments in a 2 x 2 factorial experiment. After parturition, all cows wer e moved into a large paddock and managed uniformly. Calf weights and c alf serum were collected within 1 d postpartum, thereafter at 2-wk int ervals for the next 12 wk, and then at 4-wk intervals until weaning. C olostrum Samples were taken from the cow and milk yields were determin ed by the ''weigh-suckle-weigh'' technique. Neither prepartum nutritio n nor environment influenced lactational performance of the dam. Conce ntrations of IgG were elevated in the colostrum of LO cows (15.3 vs 7. 8 g/100 mL, LO vs HI, respectively; P less than or equal to.05) but we re not affected by shading. The patterns of IgG concentration in the c alf serum were not altered by prepartum nutrition or environment; howe ver, the pattern of IgM concentrations was greater (P less than or equ al to.01) in calves from S cows than in those from NS cows. This diffe rence in IgM profile did not seem to be due to any residual effect fro m prepartum treatments. Postnatal growth of calves from birth until we aning were similar across all prepartum treatments. Prepartum nutritio n and solar radiation had no residual effects on the dam's milk produc tion and the calfs immunoglobulin concentration that might affect calf growth.