Calving and the onset of lactation challenges calcium and energy equilibrium in dairy cows, predisposing them to post-calving disorders that affect health, production and reproductive performance says Carlos Risco, veterinarian at the University of Florida.
Dairy cattle experience a negative carbohydrate balance, from three weeks prior to calving to three weeks after calving and are at risk to develop ketosis, Risco explained at the recent 2010 Western Veterinary Conference.
Milk production, in particular, drives the high requirements for glucose because other fuels cannot substitute for lactose in milk. To counteract this, the cow mobilizes body fat and protein stores in the form of non-esterified fatty acids (NEFA) and amino acids. This promotes gluconeogenesis and occurs under the influence of low serum concentrations of insulin.
Volatile fatty acids (acetate, propionate, butyrate [BHBA]) produced in the rumen are also presented to the liver as fuels. Acetate and butyrate are ketogenic, and propionate is glycogenic.
The key to prevention of ketosis is to maximize dry matter intake before and after calving to prevent excessive NEFA mobilization.
Preventing ketosis in the first place is key to avoid some post-partum issues. Risco outlined some preventive strategies, including:
- The transition ration. To prevent ketosis the transition ration should maximize dry matter intake, provide adequate energy density, and minimize ketogenic precursors. For instance, silage with a high butyric acid content should not be fed. Introduce ration changes gradually.
- Manage transition cows to maximize DMI. For example, provide adequate bunk space.
- Avoid over-conditioning of cows in late lactation and the early dry period.
- Niacin (nicotinic acid) fed in transition rations at 6 to 12 grams per day may help reduce blood ketone levels.
- Propylene glycol may be administered as a preventive measure to high-risk animals. More effective when given as a bolus rather than mixed in feed.
- Monitoring programs for subclinical ketosis. These help evaluate the effectiveness of prophylactic measures and the transition ration. They identify animals for treatment prior to development of clinical disease. Cows should be assessed daily during the first two weeks of lactation as part of the fresh-cow monitoring program. Identification of cows with ketosis is accomplished either by analyzing urine or milk ketone levels using cows-ide tests. Electronic hand-held blood glucose and ketone measuring systems are commercially available to veterinarians that surpass the predictive value of cowside milk and urine ketone body concentration. Animals with a positive test should be examined for concurrent disease.