Too frequently, transition cows show up in the ‘negative’ column due to metabolic disorders, production and reproduction problems. As producers and their advisors meet in the conference room (or kitchen), the conversation should focus on energy balance to help cows make a ‘positive’ transition.
By Ken Sanderson, D.V. M.
Every dairy cow experiences negative energy balance as she transitions from dry cow to lactation. Her lactation can be adversely impacted by the severity of the energy shortage. An energy shortage can affect peak milk, total milk and fertility. How quickly the cow recovers from negative energy balance, how quickly she returns to positive energy balance, is what matters. The faster the return, the better for milk production and reproduction.
1) Why does an energy shortage occur at calving?
The energy shortage occurs because a natural lag exists between the dairy cow’s need to generate large quantities of energy for milk production at calving and her ability to eat enough feed to meet this energy need. On a biological level, we know that how well the cow coordinates energy metabolism and glucose (energy) generation is a key determinate of milk, production and reproductive efficiency.
Ask your nutritionist for his/her opinion on the energy status of your herd.
2) Is all the cow’s energy truly produced in the liver?
Unlike monogastrics – poultry, pigs, etc. – the ruminant dairy cow absorbs very little energy though its gastro-intestinal (GI) wall. Instead, her liver plays a key role in coordinating energy metabolism. By that, I mean the production of glucose from 1) what we call gluconeogenic precursors, basically the various items that can be used to create glucose, and 2) from adipose tissue i.e. fat. Responsibility falls on the liver to coordinate the uptake of the various energy substrates, their metabolism and their export to body tissues. In early lactation, as the cow mobilizes body fat reserves for energy, there is a risk that fat will begin to accumulate in the liver. As fat accumulates, it becomes more challenging for the liver to efficiently coordinate energy production, and the tendency exists for the cow to favor the production of ketone bodies instead of glucose.
Ask your nutritionist to discuss ways of monitoring your herd for signs of problems with ketone body production as a result of fat accumulation in their livers.
3) What are signs of optimal liver function?
One of the obvious signs of optimal liver performance is the absence of metabolic problems. We know the vast majority of metabolic problems occur during the transition period. These would include clinical and subclinical ketosis, metritis, fatty liver, displaced abomasums and/or mastitis. If metabolic problems exist, the first step is to review herd management practices with your advisor(s). In an effort to understand the extent of metabolic challenge in the herd, nutritionists and veterinarians will run tests for non-esterified fatty acids (NEFA) pre-calving and beta hydroxy butyric acid (BHBA) post-calving. These tests provide good indicators as to whether or not the cow’s energy status is compromised by a build-up of fat in the liver.
Review with your nutritionist and veterinarian herd management practices to see if opportunities for improvement might exist.
4) How damaging is fat accumulation in the liver?
Well, even a small build-up of fat can decrease the liver’s metabolic functions and impact overall energy metabolism in early lactation. Liver fat accumulation generally is categorized as normal (<1% liver fat on a wet basis), mild (1-5%), moderate (5-10%) and severe (> 10%). With today’s genetic advancements for milk production, we know that virtually every cow faces energy challenges in early lactation. That means a mild-to-moderate level of fat accumulation is practically unavoidable. From industry surveys, we know approximately 50% of our commercial dairy cows have mild or moderate fatty livers, and many of these cows are struggling to manage to keep ketone body production (BHBA) at a safe level. Even if a cow has a mild level of liver fat build up, her ability to manage energy needs is significantly impaired.
Review with your nutritionist the history of metabolic problems – clinical and subclinical – on your dairy.
5) What can be done to protect the cow’s liver?
The first step is to make sure the basics of good herd management are in place. All cows should be well managed, comfortable and fed a well-formulated ration. Next, be sure an optimum level of rumen-protected choline is in the ration pre- and post-calving to ensure the transport of fat out of the liver, thereby avoiding the metabolic challenges related to poor liver function. Without rumen protection of the choline, little, if any, will reach the small intestine and be absorbed for use by the cow.
Ask your nutritionist about the use of a rumen-protected choline.
• Ken Sanderson, D.V. M. is Global Manager of Technical Service & Business Development for Balchem. Contact him via phone: 845-326-5627; e-mail: KSanderson@Balchem.com.