The 2011 and 2012 droughts that affected a large percentage of the United States have had some negative health and productivity impacts on the cow-calf herd.
click image to zoomIf weak calf syndrome is due to maternal dietary protein deficiency late in gestation, this may affect the ability of calves to absorb antibodies from colostrum. In some areas reproduction has suffered due to excessive heat during breeding season, and in others lack of adequate forage and other feedstuffs for pregnant cattle is influencing dystocia in cows and heifers as well as weaker calves at birth.
“The birth of an unacceptable number of small, weak calves in a cow-calf herd can be due to a variety of causes, and in some situations multiple causes may be involved concurrently,” explains Amelia Woolums, DVM, PhD, MVSc, Dipl. ACVIM, Dipl. ACVM, University of Georgia.
“Evidence exists to support a role for inadequate dietary protein and/or energy fed to cows and heifers late in gestation, BVDV infection in the herd during gestation, selenium deficiency, fetal thyroid abnormalities (possibly due to selenium deficiency or iodine imbalance in the dam’s diet), and prenatal infection of calves with agents such as leptospira and adenovirus,” Woolums says.
Weak calf syndrome
Woolums notes that each of these possible causes of “weak calf syndrome” could theoretically impact the immune response of the young calf (see sidebar). “It is very likely that calves that are abnormally small and weak at birth due to any of these causes have suboptimal immune function.”
However, very little research has been done to specifically evaluate immune function in calves from herds with weak calf syndrome, so it is difficult to accurately characterize the nature and severity of immune dysfunction in affected calves. “It is likely that the specific effects, and the severity of the effects, depend on the specific cause or combination of causes,” Woolums says.
If weak calf syndrome is due to maternal dietary protein deficiency late in gestation, this may affect the ability of calves to absorb antibodies from colostrum. Research has shown that calves born to cows fed a diet low in crude protein (about 1 lb/day) in the last 100 days of gestation had very low serum IgG concentrations after colostrums ingestion, as compared to calves whose dams were fed a higher amount of crude protein (about 2 lbs/day).
This difference appeared to be due to decreased ability of calves from dams fed low protein diets to absorb immunoglobulin from colostrum they were fed, and not, in this case, due to lower concentrations of antibody in the colostrum of the cows (J An Sci 53:1174, 1981), Woolums explains.