A crucial period to build immunity
Pre-weaned calves are the most at-risk population of cattle on the farm for gastrointestinal epithileum (GE) malfunction, with digestive disorders and diseases, primarily from scours. A recent survey in Canada and the United States showed that 23% of dairy calves are treated for diarrhea with antibiotics during the pre-weaning phase. This is particularly important since health affects longevity. It is known that calves treated with antibiotics during the pre-weaning period produce less milk over their lifetime (Soberon et al., 2012). This means that it’s important to establish a stable microbialpopulation. This allows the gastrointestinal epithelium to develop, to improve prevention of gastrointestinal infections and overall gut barrier function. The end result will be improvements in efficiency, food safety, and animal welfare.
Importance of colostrum, why it's needed quickly after calving
During pre-weaning, the closure of the intestinal permeability to the immunoglobulins of colostrumis one of the most important changes in terms of gut function. This is why it is so important to feed colostrum quickly after calving. Although it is known that this occurs, the precise mechanisms that control this closure are not know.
Dr. Steele indicates that colostrum and milk have often been described as the complete prebiotic, as they contain one of the largest collections of bioactive proteins, carbohydrates and fatty acids. In particular, colostrum has a large number of growth factors,all of which directly affect gut growth signaling pathways. Another example of the importance of colostrum to gut development comes from research focusing on the effect of the duration of colostrum feeding which has promoted growth responses in different structures of the small intestine. It is thought that the bioactive components in colostrum play a key role in establishing a balanced microbial population and gut growth in the first days or weeks of life, but Dr. Steele says that they are not yet clearly described.
Managing change from liquid to solid feed
Weaning brings with it two major changes: feed digestion moves from liquid feed, occurring primarily in the abomasum and small intestine, to solid feed,primarily fermented in the rumen. Thus, weaning results in changing the sites of digestion and absorption, and the type of nutrients being absorbed and metabolised. Rumen capacity also increases, going from 30% to 70% of the entire GIT. These are big challenges, especially for dairy calves, if we consider that natural weaning occurs gradually over many weeks, continuing up to 10 months of age.
Importance of the "gastrointestinal barrier"
Although much research related to weaning has focused around the rumen and maximizing solid feed intake, Dr. Steele believes that more research is needed to understand how these changes influence the lower gut, particularly the function of the gastrointestinal barrier. This barrier has multiple functions and is very important because it prevents the passage of unwanted substances to the blood. This can trigger an inflammatory response and cause reduced growth and performance. In some studies, an increase in inflammatory markers during weaning suggested that calves may also suffer from temporary hindgut acidosis, as indicated by elevated levels of starch in the manure during weaning.
Dr. Steele indicates that finding optimal weaning strategies that stimulateGE development becomes extremely important, especially with the current recommendations of feeding higher levels of milk. Dry feed intake before weaning is critical to avoid loss of growth and disease after weaning. He says the industry needs to develop practical strategies that allow for a balance between accelerated weight gain but also an accelerated development of all the digestive organs and membranes. He concludes by saying “greater investigation of the lower gut microbiological, structural,and functional changes and how these changes contribute to weaning stress is a logical next step in research.”
Top 5 steps to promote solid feed intake
1.Provide clean, fresh water at all times.
2.Provide fresh calf starter.
3.Use a step-down approach in terms of the amount of milk being offered.
4.Ensure ample and easy access to the feed bunk.
5.Maintain high levels of comfort. Thesemay help reduce the risk of disease and growth setbacks on this naturally stressful phase of a calf’s life