This Real Science Exchange podcast episode was recorded during a webinar from Balchem’s Real Science Lecture Series.
The primary goal of a replacement program is to raise the highest quality heifer that can maximize profits when she enters the lactating herd. She carries no limitations that would detract from her ability to produce milk under the farm’s management system. Ideally, one would wish to optimize profits by obtaining the highest quality heifer at the lowest possible cost, usually in the least amount of time. Dr. Van Amburgh presents a snapshot evaluation of benchmarks to assess the potential quality of replacements. (3:47)
When does the process of creating a quality heifer start? Probably before conception. In non-pasture herds, the first lactation cows giving birth to heifers produced about 1000 pounds more milk in the first two lactations. Heifers whose dams were supplemented with choline during the pre-fresh period had higher birth-to-yearling average daily gains and improved immunity. Choline also appears to enhance the quality of colostrum via increased absorption of IgG. This implies that maternal programming extends beyond the uterine environment via ingestion of milk-borne factors, known as the lactocrine hypothesis (14:29)
After the calf is born, the goal is anabolism or growth. The dam communicates with the calf via colostrum to direct calf development after birth. Not only does colostrum provide immunoglobulins, but it also contains a large amount of nutrients and non-nutrient factors that support gut maturation. In particular, IGF-1 and insulin may act on receptors in the gut to stimulate cell proliferation, cell differentiation, and protein synthesis. Dr. Van Amburgh summarizes several studies that showed increased colostrum feeding improved pre- and post-weaning growth and development. While the immunoglobulin content of colostrum is essential for passive immunity, the other components in colostrum are responsible for the increased growth performance. (27:39)
The hormones and growth factors in colostrum enhance protein synthesis, enzyme expression, and gastrointestinal tract development. This implies that the gut is now an even stronger barrier to infection, with more surface area for digestion and absorption, with an increased capacity to digest nutrients due to higher enzyme excretion. (36:33)
To investigate the impact of non-nutrient factors in colostrum, studies were designed where calves were fed either colostrum or milk replacer with the same nutrient content. Glucose uptake was increased for colostrum calves even though both groups received similar nutrient content. Plasma glucagon was higher in colostrum calves, indicating better glucose status and higher reserve capacity. Plasma protein levels were higher in colostrum calves, suggesting more amino acids available for growth and protein synthesis. Plasma urea nitrogen was lower for colostrum calves, indicating fewer amino acids were used for gluconeogenesis leading to more efficient growth. (46:55)
What happens to immune cells in colostrum? Leukocytes and other immune-related cells in colostrum are trafficked into the circulation of the calf. Maternal leukocytes can be detected in the calf by 12 hours, peak at 24 hours, and disappear by 48 hours. Long term, there appears to be greater cellular immunity in calves that received whole colostrum compared to cell-free colostrum. Uptake of cells from colostrum enhances cellular immunity in calves by providing, mature, programmed cells from the dam. (52:24)
The take-home message for colostrum management is to feed colostrum for four days. Give first-milking colostrum within six hours of birth and again at 12 hours. Give second-milking colostrum for day two feeding and third- and fourth-milking colostrum for days three and four. (56:04)
Dr. Van Amburgh answers a few questions from the webinar audience about dry cow management for colostrum quality and quantity, the impacts of pasteurization of colostrum on components, and the efficacy of colostrum replacers. Watch the full webinar at balchem.com/realscience. (58:25)
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