BROOKINGS, S.D. - Research indicates that the ability of colostrum to provide passive immunity to the calf is often limited by low concentration of colostral immunoglobulins, insufficient methods of feeding colostrum, and limited absorption of immunoglobulins in the calf, says Janna Kincheloe, SDSU Extension Research Associate.
"Good quality colostrum should contain more than 50 grams per liter of IgG, which is the primary immunoglobulin in colostrum," Kincheloe said. "Quality may be inadequate if dams are young, nutritionally stressed, have a poor immune status, or produce large volumes of lower quality milk."
Colostrum-deprived calves are 50 to 75 times more likely to die within the first three weeks of life, most of them in the first week. Kincheloe says producers can confirm the level of IgG found in colostrum by testing it for antibody content. She adds that it is important to know the quality of colostrum being produced by the cow to be able to determine which type of product - supplement or replacer - is recommended for a given situation.
Although commercially available colostrum supplements or replacers can play an important role in calf health, Kincheloe says for best results, producers need to understand the differences in these products based on their formulations and how to use them for optimum results.
"Failure of passive transfer (FPT) can be determined by a test evaluating plasma IgG concentration within 24 to 48 hours after birth," Kincheloe said.
She explains that the critical level used to indicate FPT in calves is less than 10 grams per liter. Products are classified by their ability to raise plasma IgG concentrations. Colostrum supplements do not raise the plasma concentration above the species standard of 10 grams per liter, while replacement products do.
The USDA Center for Veterinary Biologics regulates colostrum products containing IgG. In general, products that contain less than 100 grams IgG/dose are categorized as colostrum supplements, and are designed to be used when feeding low or medium quality colostrum.
Kincheloe says replacer products can be used to completely replace colostrum, as they contain greater than 100 grams IgG/dose and also supply additional nutrients required by the calf (carbohydrates, protein, fat, vitamins and minerals). Research results indicate that calves fed replacer products perform similarly to those fed maternal colostrum in terms of IgG levels, health, and growth rates.
"However, the quantity of IgG provided by each product does not accurately predict how much is actually available to the calf," Kincheloe said.
Kincheloe explains that the amount of IgG that can be measured in the plasma 24 hours after birth is known as the apparent efficiency of absorption (AEA).
Research data suggests that absorption efficiencies typically range from 20 to 35 percent in maternal colostrum and many supplements. Most veterinarians recommend that calves receive 100 grams of IgG within the first 24 hours of birth; however, efficiency of absorption must be considered when determining type and amount of supplement to be provided.Considering average AEA's of most products, the actual amount of IgG consumed should be between 103 and 180 grams in order to reach the critical plasma level of 10 grams per liter.
"Factors that can affect AEA may include source of IgG, method of processing, amount and type of protein, and presence of fat and lactose. Some research has shown that the addition of some colostrum supplements may actually reduce IgG absorption from natural colostrum," Kincheloe said.
In general, Kincheloe says the three sources of IgG in colostrum products are derived by lacteal secretions, like milk, whey, or colostrum; bovine serum extracts or chicken eggs.
Kincheloe points to the results from one study comparing the efficiency of IgG absorption in a bovine serum product (BSP), cow colostrum (MC; control), and two commercial milk-derived supplements; the results indicate that the initial concentration of IgG is an important consideration when choosing a powdered supplement.
"Feeding a greater amount of a product containing low concentrations of IgG can actually result in decreases in absorption efficiency, so it is best just to feed a higher quality product initially," Kincheloe said.
"Be sure to carefully read and follow the manufacturer's instructions since products may vary in how they are mixed and the number of recommended feedings. Plasma IgG tests may be recommended in situations of high morbidity/mortality to determine prevalence of FTP and the efficacy of colostrum management in the herd," Kincheloe said.