Interaction of cattle health/immunity and nutrition

The usual means of assessing the health of newly received beef cattle susce ptible to bovine respiratory disease (BRD) are subjective, typically involv ing visual evaluation aided by minimal clinical measurements. Recent eviden ce based on the occurrence of pneumonic lung lesions at slaughter indicates a need for more accurate methods of diagnosing BRD. Inadequate passive imm une transfer at birth may be an important risk factor in susceptibility to BRD, suggesting the need for management to improve passive transfer success rates. Preweaning management and vaccination practices offer opportunities for beef cattle producers to improve the immune status of newly weaned cal ves and decrease postweaning BRD. Feeding diets with higher levels of conce ntrate typically improves performance by newly weaned or received cattle, a s does feeding diets supplemented with protein; however, limited data sugge st that increasing concentrate and protein in receiving diets increases the rate and severity of subjectively determined BRD morbidity. Research with receiving diet concentrate/protein level relative to humoral and cell-media ted immune function coupled with indicators of health and performance is ne eded. Supplemental B vitamins are sometimes useful in receiving diets, but the effects have been variable, presumably reflecting differences in stress and associated feed intake responses; Vitamin E added to receiving diets t o supply greater than or equal to 400 IU/animal daily seems beneficial for increasing gain and decreasing BRD morbidity; however, further dose titrati on experiments are needed. Supplemental Zn, Cu, Se, and Cr can alter immune function of newly received calves, and some field trials have shown decrea ses in BRD morbidity rate with supplementation; however, several experiment s have shown no performance or health/immune benefits from supplementation of these trace minerals. Formulation of receiving diets should take into ac count; decreased feed intake by highly stressed, newly received beef cattle and known nutrient deficiencies, but fortification of such diets with trac e minerals beyond the levels needed to compensate for these effects is diff icult to justify from present data.