Bob raises heifers for a client. He contacted me because my client’s calves were struggling with diarrhea and respiratory disease shortly after moving to his farm. Calves arrived a couple of weeks after weaning and were eating about 5 pounds of calf starter per day. Just about every group of calves he received did well for two or three days, then began to scour, then started to get rough hair coats and then some would develop respiratory signs. Bob would treat them with cocciostats, antibiotics and dewormers, and most of the calves would recover and look good within two or three weeks. But Bob was getting tired of seeing beautiful, slick-haired calves arriving at his farm and then, within a week, looking really bad.   
    This is a common story at some heifer farms and dairies today. Because we have learned how to successfully feed a lot of milk or milk replacer to baby calves, we see rapid growth and big, strong calves at weaning. Often though, calves struggle post weaning. Recognizing this, many producers now do step wise weaning by reducing milk amounts or feeding frequency in the last couple of weeks before weaning. This encourages starter intake. Nutritionists often recommend that calves should be eating somewhere between 3 and 5 pounds a day of starter before calves are weaned. We know that grain intake induces development of rumen papilla and thus should make the transition easier. Often, calves transition poorly because they are not eating enough starter, so they develop negative energy balance after weaning. Negative energy balance may result in a variety of diseases taking hold, such as Salmonella, coccidiosis or bacterial pneumonia. Thus, veterinarians and nutritionists often stress to their clients the importance of maintaining grain intake immediately post weaning.
    This is exactly what I did in this case. I suggested he feed more starter. The calves were in a large group, or around 40, and I was convinced that some were not eating enough. Bob was not impressed with my recommendation. He called me in a few weeks and said the latest group of calves had sailed right through the transition without a hitch. I asked him what he did differently this time.
    “I fed them some hay on top of the starter,” he replied.  
    He also mentioned that the diet was formulated with enough fiber in the pellets that calves were not supposed to need additional forage fiber in the diet, but that clearly, they did based on what he saw. That was a few months ago, and Bob’s latest report is that things are still going well.  
    What happened here? Most likely the calves suffered from subclinical rumen acidosis (SARA). SARA occurs when rumen pH drops below 5.8. SARA is probably very common in dairy calves as explained by Quigley: https://www.calfnotes.com/pdffiles/CN170.pdf. Most dairy calves probably experience SARA, but the degree and length is different for each calf. Calves with SARA may show no observable signs, or they may show loose stools, reduced feed intake and be prone to develop secondary diseases as was the case in Bob’s calves. Why did feeding hay prevent the problem in subsequent groups? Should we be feeding forage to pre-weaned and or post-weaned calves?  
    For at least 20 years, most experts have not recommended feeding forage to calves before weaning. Feeding forage has shown to decrease starter feed and total dry matter intake. Feeding forage may also reduce feed efficiency and has been observed to cause hay bellies in some cases. Feeding forage immediately post weaning has also been linked with reduced DMI of starter, so some nutritionists prefer to wait for a couple of weeks or longer after weaning to introduce forage. However, few studies have been done using today’s larger, higher-intake calves to evaluate positive and negative effects of feeding forage. Also, two recent literature reviews published in the Journal of Dairy Science (Khan, et al., 2016 and Imani, et al., 2017) suggest feeding forage to calves both before and after weaning may be advantageous. From Khan: “We conclude that the provision of high starch and low-fiber starter feeds may negatively affect rumen development and that forage supplementation is beneficial for promoting development of the gut and rumination behavior in young calves. From Imani: “This meta-analysis revealed improvements in starter feed intake, average daily gain, final body weight, ruminal pH … with feeding forage but a depression in feed efficiency.”  
    Both papers reviewed much of the scientific literature available and came to similar conclusions.   
    No doubt there can be negative effects of feeding forage to calves before and after weaning, and any change should be discussed with the farm’s nutritionist and veterinarian. However, rough looking, weaned calves with loose stools are fairly common today and not normal, even though most producers have achieved very good or excellent pre-weaning calf health and rate of gain. We should not accept poor looking calves as normal. Perhaps we should reconsider the role of SARA and possible prevention by feeding forage when post-weaning slump occurs. Bob would agree.
    Bennett is one of four dairy veterinarians at Northern Valley Dairy Production Medicine Center in Plainview, Minn. He also consults on dairy farms in other states. He and his wife, Pam, have four children. Jim can be reached at bennettnvac@gmail.com with comments or questions.