Restricted dietary protein in pregnant beef cows: II. Effect on the immune response

Cows fed 0.37 Kg crude protein per day for four months before calving showed no decrease in colostral IgG, IgA, or IgM from cows fed a normal ration. Similarly, no difference in serum immunoglobulin concentration was detected in their calves. Cows in the low protein group developed significantly lower (P < 0.01) titers to Salmonella pullorum antigen than did the normal group. The data show significant positive linear regressions of calf agglutination titer to S. pullorum on the dam's colostral titers. Serum levels of IgG measured at 24 hours were significantly lower in calves from second-calf heifers than from these of other age groups. The IgA levels of serums from calves from the six-year-old cows were significantly higher than the serum levels of calves from younger dams (P < 0.01).