Many of the more serious problems that happen at freshening take root during the dry period – and most have a nutritional basis.
When fresh cow problems occur, screening blood samples from the far-off and close-up dry cows, as well as the early-fresh cows, can help you focus on the causes. Several tests, such as measuring non-esterified fatty acids, blood mineral levels, blood urea nitrogen levels and blood albumin levels, can help you truly understand how your dry cows are doing on the ration you provide. Although these tests are not an end in themselves, they are useful to help you analyze a nutrition problem.
With the help of Bob Van Saun, veterinarian at Oregon State University's School of Veterinary Medicine, I've begun to draw some tentative conclusions regarding protein status during the dry period. Unlike lactating animals, where we find high protein levels, dry cows often show low levels of protein.
Here's how it works: Blood urea nitrogen (BUN) indicates the level of protein currently being metabolized by the cow. When we see high BUN numbers – more than 16 milligrams per deciliter – we tend to conclude that the diet contains excess protein or an imbalanced source of protein. When we see low numbers – less than 12 milligrams per deciliter – we conclude that protein in the ration is probably limited and the cows don't receive quite what they need. In fact, some research indicates that the rumen bugs don't fare well when BUNs drop below 10 to 12 milligrams per deciliter.
It's also important to note that normal or high BUN levels may not always indicate adequate ration protein. It can also indicate that the cow is using her own protein reserves to meet the needs of a growing calf.
That's why you should also look at a second number – the cow's blood albumin levels. Albumin is a protein found in the bloodstream. When an animal is not getting enough protein in her ration, she can use these proteins to meet other needs, such as growing a calf. If she takes protein from reserves long enough, blood albumin levels will decline. Additionally, the cow may begin to use her muscle proteins.
Suppose, for example, a far-off dry cow is fed a ration that does not meet her protein needs. Her BUN level will tend to be low, while her albumin level will be normal. As the cow reaches the close-up period, her protein requirement goes up significantly due to the growing calf. It is not uncommon to find low albumin levels, indicating that she has been using her own body stores to meet her protein needs. If this is the case, her albumin levels can drop even lower once she freshens. This can have a profound effect on her ability to perform.
The calf may also be affected. It is not uncommon to find an increase in calf health problems when the fresh cow has problems. Adequate protein is necessary for the formation of high quality colostrum, as well as a healthy immune system for the cow and the calf.
Don't forget about the dry cows! High quality dry cow nutrition and a good environment forms the basis for profitable milk production. Adequate protein during this time is absolutely essential to a healthy cow and calf. Your veterinarian can help sample and interpret results to determine if an opportunity for improvement exists in your herd.
Mark Wustenberg is a veterinarian in Bay City, Ore., and operates Kilchis Dairy Herd Services with his wife, Judy.