Feeding Mineral to Beef Cows
Last winter (2016) several cow-calf herd owners discovered the perils of underfeeding, or not feeding, mineral to their pregnant beef cows. This may seem an odd topic for July - however, plans need to be made now to accommodate management or facility changes needed to improve future mineral feeding to cows.
Health problems associated with underfeeding mineral to beef cows are usually rare in Ontario. It may be that they do occur but are usually mild or very slow in developing and are therefore under-diagnosed. Last winter several situations occurred where herd owners experienced extreme problems that lead them to work with their herd vet or local feed advisor to get a diagnosis on their herd's problems. In one case, samples were collected for testing from cows that died or were euthanized, and in the others, calves were submitted to the Animal Health Laboratory in Guelph for post-mortem and testing. These situations highlight the importance of assessing and improving mineral feeding to beef cows.
In one herd the problem experienced was a high proportion of very poor-doing cows with very rough hair coats and a large number of open cows in the early winter. Cow mortality was also higher than in past years. Testing of liver samples from cows that died showed that copper deficiency was occurring in the cows. Forage testing showed that the hay being fed exclusively was high in molybdenum. In other herds the problems occurred mainly with the calves. One herd had about 25% of calves born in the spring with deformed limbs (dwarfism) due to manganese deficiency. Manganese deficiency is associated with silage feeding without grain or mineral supplementation. Three other herds had calves with selenium deficiency. In two herds, the calves had classical white muscle disease (WMD) where calves were weak and down about two weeks after birth. In one herd respiratory disease affected calves on pasture at about three weeks of life. Calves from this herd sent for post-mortem were found to have bronchopneumonia and lesions of WMD, suggesting the pneumonia may have been more severe because of concurrent selenium deficiency. In one of the herds where calves had WMD several calves also had congenital goitre, likely indicating iodine deficiency in the dams. In all cases, the history on farm management collected by the herd or laboratory veterinarian indicated that mineral was either not fed at all, was being underfed, or was being offered free-choice in a manner that likely prevented a proportion of the herd from receiving an adequate intake.
These are examples of problems in Ontario beef herds that could be prevented by improved nutritional management and provision of adequate supplies of mineral for the cattle. Not all problems are this severe but it seems likely that, currently, mineral feeding problems may not be diagnosed unless a high rate of problems trigger further diagnostics and testing. More subtle losses in productivity and performance are likely present in other herds with similar management but where a severe cattle health problem affecting numerous head has not occurred. In Western Canada, in a mineral feeding study livers from 129 calves (105 herds) that died between 3 days and 3 months of age were tested to identify mineral deficiencies. The results showed that 32.5%, 5.4%, 6.2%, 7.7%, 35.3% and 75.6% of these calves were deficient in selenium, copper, zinc, manganese, Vitamin A and Vitamin E respectively. The actual deficiencies may vary by region, however the results strongly suggest very poor mineral feeding practices to cows overall.
All cattle on pasture and on winter feeding require mineral supplementation to some degree. What they require can vary depending on geographical location (particularly true for molybdenum and copper related problems), forage type, forage quality and season. A key issue is ensuring appropriate and sufficient supply of minerals on a steady basis, if not daily then at least weekly. Most minerals and vitamins are not stored well or for any length of time in an animal's body, therefore an ongoing and steady supply is required.
In all the Ontario cases, post-mortem diagnosis and sample submission to the laboratory was a key step for obtaining a proper diagnosis and determining a specific remedy to the problem. Laboratory records show that this is an underutilized service, perhaps because of the difficulty in getting calves to the lab or because of an under appreciation of the value of post-mortem examination. It may also be that when common conditions like scours or pneumonia are seen, a presumptive diagnosis is made and samples or calves are not submitted to the lab. The potential negative impact of mineral deficiencies on the immune system is missed.
Testing forage is the only way to determine if a particular geographical region produces forages or other feeds with specific mineral deficiencies. Sometimes an area has previously been identified as deficient and nutritional advisors or vets can advise on specific requirements. However forage testing to estimate mineral content remains the best initial step in setting up a mineral supplementation program. Feed advisors, websites or feed testing laboratories can advise on the correct methods for collecting feed samples, how to submit samples to the feed lab and which tests to request. If cattle die, veterinarians can provide post-mortems on the farm or assist in getting liver samples (or whole carcasses where geography allows) submitted to the diagnostic laboratory.
Research from Western Canada has indicated that only about a third of cow-calf producers surveyed in a large study indicated they routinely provided mineral to their cows. Collection of information via a similar survey is underway currently in Ontario. When collated it may help to target mineral feeding as an area of beef cow-calf management that should be addressed to improve cattle health and
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