TAS & NEFA: Benefits for dairy cattle during the transition period
The transition period between late pregnancy and the onset of lactation requires quick metabolic adaption by dairy cattle as foetal growth, calving and the onset of lactation causes increased energy demands on the body. To support the increase in energy requirements, increased nutrients are required; however, limitations to dietary intake can occur as a result of reduced appetite caused by the growing foetus restricting the size of the rumen. In addition, during this period almost all glucose intake is utilised for lactose synthesis. As a result, during the transition period dairy cattle can be prone to negative energy balance.
Negative energy balance occurs when energy demands exceed dietary intake, and in cases where energy requirements are not met by diet, dairy cattle will utilise their own fat reserves as an energy source; this being non-esterified fatty acids (NEFA), a major component of triglycerides (fats) in the body. Excessive metabolism of NEFA, however, can result in accumulation of fat which can result in fatty liver disease (resulting in decreased liver function), and ketosis which can be toxic and damaging to the liver and kidneys (it has been associated with pregnancy complications, decreased milk production and hypoglycaemia).
Additionally, during the transition period, as a result of the increase in metabolic processes, dairy cattle are more susceptible to metabolic stress. This is due to the increase in Reactive Oxygen Species (ROS).
ROS are free radical by-products of normal metabolic processes which can be harmful and destructive to the cells in the body. To defend against them the body utilises antioxidants to inhibit the formation of free radicals, destroy free radicals or repair the damage caused by free radicals; however if there is an imbalance of antioxidants to ROS then the body’s natural defence system is decreased. This can result in free radical damage to surrounding cells, tissue and DNA.
Free radicals have been implicated in many disease states in addition to suppression of the immune response system. As a result, in the first 10 days after calving dairy cows are at maximum risk of infectious and metabolic disorders; in fact, approximately 75% of disease occurs in herds within the first month of lactation (Abuelo et al. 2014). Complications for dairy cattle suffering metabolic stress include not only fatty liver disease and ketosis, but also mastitis, retained foetal membranes, reduced milk production and increased risk of cancer, CVD, lung, liver and renal disease, inflammatory conditions such as arthritis, infectious conditions, and, neurological disorders.
How can the health and well-being of dairy cattle be protected during the transition period?
To ensure animal well-being, and indeed reduce economic impact for dairy farmers, dairy cattle should be monitored for their antioxidant capacity, particularly during pregnancy. As the antioxidant defence system includes many components, the Total Antioxidant Status (TAS) test is used to assess overall antioxidant capacity. This test is beneficial in gaining an overall view of the body’s ability to defend against free radical attack; it can therefore help to determine if nutritional supplements are required to ensure good body condition during the transition period. Further antioxidant testing may be required to ensure nutritional requirements are fully understood before antioxidant supplementation begins.
In addition, the NEFA test indicates negative energy balance, and can therefore be used to monitor whether their nutrient intake is adequate for the high energy demands experienced during the transition period. Additionally, research (Li, H.Q et al. 2016) has found that supplementing dairy cattle with rumen-protected folic acid (RPFA) may benefit negative energy balance by decreasing plasma concentrations of NEFA and increasing glucose plasma. Results show increased milk protein levels and improved nutrient ingestion, milk production and reproductive performance.
Abuelo A., Hernandez J. and Beneditor J.L (2014) The importance of oxidative status of dairy carrel in the periparturient period: revisiting antioxidant supplementation. Journal of Animal Physiology and Animal Nutrition. 99(6):1003-1016
Li, H. Q., et al. (2016) Effects of dietary supplements of rumen-protected folic acid on lactation performance, energy balance, blood parameters and reproductive performance in dairy cows. Animal Feed Science and Technology