Subsequent milk production and metabolic response of first-calf heifers fed whole raw soybeans during the last trimester of gestation

Abstract

Sixteen pregnant heifers (8 per group) were fed diets containing soybean meal or whole raw soybeans (WSB) to evaluate effects of the supplemental dietary fat provided by WSB during the last trimester of gestation (90 d) on performance in the first 5 wk of the subsequent lactation, during which both groups were fed the same diet. Despite similar DMI by both groups, heifers fed WSB had greater ether extract (EE) intake and tended to weigh more after calving. By 35 DIM, heifers previously fed WSB had greater milk yield with a tendency for greater milk fat yield, although DMI was similar for both groups. Blood obtained by jugular venipuncture four times per day during gestation (-90 d, -69 d, -48 d, and -27 d), on day of calving (0 d), and during lactation (+35 d) was used to evaluate glucose and NEFA response to diet. Glucose concentration in blood plasma at -69 d and 0 d was lower in heifers fed WSB; whereas, plasma NEFA concentration was greater at -69 d, -48 d, and +35 d, but lower at 0d. Basal concentrations of glucose and NEFA in plasma and their response to insulin challenge (.26 IU per kg BW) were similar for both dietary groups at -30 d and +35 d. Plasma NEFA concentrations in response to insulin challenge, however, were greater at -30 d than at +35 d. Basal plasma triacylglycerol concentration was greater at -30 d and lower +35 d, due to feeding WSB during gestation. In addition, plasma 16:0 and 18:1 (%, wt per wt) concentrations were lower and 18:2 higher at -30 d in heifers fed WSB. At 35 DIM, heifers previously fed WSB again had lower 16:0 and higher 18:2 in plasma. Dietary treatment during gestation had no influence on long chain fatty acid concentrations in adipose tissue. Supplemental dietary fat provided by WSB for 90 d prior to parturition apparently altered the supply and metabolism of lipids in a manner that improved milk production during early lactation.