Microminerals: An aid for dairy cows in transition
Dairy cows experience a dysregulation of their immune function during the transition period. This period encompasses the three weeks before calving and the three weeks after. Being recognized as an important driver of metabolic and infectious diseases (e.g., ketosis, displaced abomasum, mastitis, metritis, etc.).
This period is characterized by marked changes in the endocrine state of the animal and a reduction in feed consumption. Meanwhile during this time, the nutrient demands for the developing fetus and for lactogenesis are increasing.
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.
Metabolic stress refers to the hypermetabolic and catabolic response to the disruption of physiological homeostasis. It is characterized by: excessive lipid mobilization, immune and inflammatory dysfunction, and oxidative stress. These three processes are intrinsically linked and result in immune and metabolic disorders, which are associated with an increased risk of metabolic and infectious diseases during this period.
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:
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.
| How can supplementation with micro minerals help during the transition period? |
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 presence of dietary deficiencies (Zn, Cu, Mn and Se) due to antagonisms or unbalanced diets, has resulted in the need to evaluate the supplementation of these minerals in dairy cattle. Recent studies have assessed the supplementation of these trace minerals through an injectable administration. The results exhibited improvements in animal health and higher serum concentration of SOD in dairy cows that were supplemented 30 days before calving and during the second month of lactation.
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 recent study conducted by a group of researchers from Texas Tech University (Silva et al., 2021) evaluated the supplementation of trace minerals(Cu, Se, Zn and Mn)using an injectable form. Assessing its effects on: health, performance, and the oxidative stress of dairy cows in transition subjected to caloric stress.
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.