There are always going to be stories of a calf that does well without colostrum. Not getting colostrum does not mean the calf is going to get sick & die - & getting a good colostrum source does not guarantee it won't get sick & die. But - it sure puts the odds in favor of the calf doing well.
Here's part of an article:
In cattle, the survival of the calf is dependent on its receiving high-quality colostrum within the first 24 hours of life, because the structure of the placenta prevents the fetus from receiving immunoglobulins (IgG) in utero. This is very different from most species, such as humans, which receive IgG across the placenta, and are born with the ability to mount an immune response to pathogens. As a result, newborn calves can't fight a bacterial or viral challenge until they have acquired passive immunity through the IgG in colostrum. The IgG are a specialized form of antibodies, gamma globulin proteins, that fight bacterial and viral infections by binding to pathogens and neutralizing them. With cattle, the newborn calf's small intestine can only absorb IgG during the first 24 hours of life. Furthermore, within the first 24 hours of life, the timing of the calf receiving colostrum is critical as the ability to absorb IgG from the small intestine starts to decline after the first 6 hours, and is essentially stopped after 24 hours (Rogers and Capucille, 2000). Therefore, for optimum immunity, the calf needs to nurse well within the first 6 hours. With first-calf heifers, this timing is an important management issue, as heifers that don't let their newborn calves nurse immediately are in a much greater danger of losing them, or having them get sick.
The effects of poor immunity in newborn calves have real economic impacts. Calves with inadequate serum immunoglobulin at 24 hours of age were found to be up to nine times more likely to become sick, and five times more likely to die before weaning, compared with calves that received adequate immunity, and calves that became sick within the first 28 days, after calving, were 35 pounds lighter at weaning than calves that were healthy (Wittum and Perino, 1995). As this research showed, colostrum quality and quantity can have a major impact on profitability. In a recent study, 6% of calves between 2 and 8 days of age had inadequate immunity, 10% of calves had a marginal immunity, and one-third of the calves were below the adequate immunity level based on a blood serum IgG level of 24g/L (Waldner and Rosengren, 2009). For producers who need to know how much colostrum a calf needs, research has found that an adequately nourished beef cow should be able to provide an adequate supply of IgG in about 3 liters of colostrum, which means that a calf should consume one pint of colostrum for every 20 pounds of calf weight (Rogers and Capucille, 2000).
