Micro-minerals: An aid for dairy cows in transition

Dairy cows suffer an immune dysregulation at the time of calving, which has been primarily associated with the onset of lactation and not with event of calving itself. In addition to this, studies conducted during the last decade, indicate that adult dairy cows suffer from oxidative stress (OS) at the time of calving. OS occurs when there is an imbalance in the redox balance, which leads to cell damage and/or dysfunction. This oxidative phenomenon has been proposed as the potential link between metabolic and immune disorders during this phase.

Oxidative stress is characterized by the imbalance between oxidizing and antioxidant molecules, which results in the damage of biomolecules by free radicals. This creates a pro-oxidant state that favors the occurrence of oxidative lesions in macromolecules and cellular structures.

The excess of free radicals in ruminants is responsible for several pathological processes, such as: liver diseases, inflammation, mastitis, anemia, among others.

In addition to this, cows are more sensible to environmental conditions during the transition period, causing greater impacts due to heat stress. This situation aggravates the whole scenario and results in:

Reduced feed intake

Increased degree of oxidative stress

Dysregulation in cows’ immune function.

A high prevalence of disorders has been observed in dairy cows that find themselves within the transition period while subjected to heat stress conditions.

The environmental conditions associated with heat stress, can affect cows’ immune systems through several complex mechanisms. Including changes in body temperature,  behavioral and hormonal adaptations, circulatory adjustments, and oxidative stress.

The use of ventilators, nebulizers, as well as the provision of shade, are some the commonly adopted strategies to improve performance and immune function in postpartum cows  subjected to caloric stress.  Water availability and quality are also essential.

The supplementation of Zn, Mn, Cu and Se, which are components of antioxidant enzymes such as glutathione peroxidase (GPx) and superoxide dismutase (SOD), have been studied as alternative strategies to alleviate the deleterious effects of heat stress on animals’ immune state and performance. Therefore, it is possible that mineral supplementation can contribute to mitigate the adverse effects of heat stress in dairy cows during their transition period.

The inclusion of microminerals (Zn, Cu, Mn and Se) in cow diets during the transition period can:

• Improve the immunity of cows
• Improve udder health
• Reduce the risk of of clinical mastitis
• Reduce the onset of uterine diseases
• Lower the incidence of clinical endometritis
• Reduce the incidence of stillbirths

In addition to the aforementioned benefits, this type of supplementation has been shown to contribute towards a higher neutrophil/lymphocyte ratio.  Increasing the animal’s inflammatory potential during the first days of postpartum; providing a greater capacity to eliminate uterine pathogens.

A total of 923 multiparous cows from 2 commercial dairy farms were randomly allocated to two treatments: control and injectable trace mineral supplementation (ITMS).

ITMS cows tended to have a lower incidence of metritis and stillbirths compared to the control group. In addition, ITMS improved the inflammatory status of dairy cows under the transition period.

On the other hand, researchers observed that the ITMS treatment had no significant influence over: the incidence of other diseases (e.g., mastitis, placental retention), milk production, reproductive performance, cow replacement, and leukocyte count.

Redox balance is essential for various biological processes in dairy cows and calves. However, when there are imbalances between the production of oxidants and the animal’s antioxidant mechanisms, oxidative stress can occur. Resulting in the onset of immune and metabolic disorders.

When oxidative stress occurs in gestating animals, it not only puts the mothers at risk from suffering subsequent diseases during early lactation, but it also has an impact on the offspring.