A research team at the University of Minnesota has found that dairy cows with ketosis and low milk yield during the first week of lactation had lower pregnancy rates and took longer to become pregnant. In contrast, cows with ketosis and mid- to high milk yield during the first week of milking did not have measurable reproductive problems.
Ketosis, or hyperketonemia, is a disorder in dairy cows that often occurs during the weeks surrounding calving. Measured by increased ketones circulating in the blood, the disorder is thought to result from energy imbalance and fluctuations in hormones and metabolism during pregnancy and lactation. Ketones are chemicals found in the blood stream when the liver converts fat to energy because the body is low on glucose (sugar). Ketones change the chemical balance of the blood by making it more acidic. Negatively affecting health, milk productivity, and reproduction in some, but not all, cows, ketosis can result in decreased profits on farms and leads to the culling of some animals.
To better understand the relationship between ketosis, milk yield, and reproduction in dairy cows, a research team led by Luciano Caixeta, DVM, PhD, examined data previously collected on 2,000 Holsteins from five commercial farms. The researchers analyzed time to insemination and conception in cows with and without ketosis against groups of cows with low- versus moderate to high milk output during the first week of lactation.
It was previously thought that cows with high milk output directed energy stores to milk production, which resulted in poorer reproductive performance. This study found, instead, that cows with moderate to high milk yield had higher reproductive performance than low-milk-yield cows. Even in a state of ketosis, cows with higher milk output had better reproductive measures, the new study found. In contrast, cows with low milk production and ketosis showed impaired reproduction. These results suggest further study is necessary to understand the importance of milk yield during the first week of lactation as a predictor of reproductive success and health outcomes. In managing the health of dairy cows after calving, lower milk yield in combination with ketosis may warrant closer monitoring and intervention.
Source : umn.edu