COVID-19 AND TRANSITION COW: WHAT'S COMMON?
COVID-19 disease has been spread all around the world in 2020. Patient diagnosed with COVID-19 suffer from fever, shortness of breath, dry cough … Some complications are largely due to overdrive of the host immune system leading to “cytokine storm”. During transition (3 weeks before calving to 3 weeks after calving), dairy cow faces a similar challenge due to major modification in her physiology because of calving and lactation. In both case, Omega 3 are helping: they are proven anti-inflammatory molecule.
INFLAMMATION AND CYTOKINE STORM
Inflammation is a complex biological response of body tissue to a harmful stimulus like infection or tissue injuries. The function of inflammation is to eliminate the initial cause of cell injury, clear out necrotic cells and tissues damaged from the original injuries or infection. Finally, inflammation initiate tissue repair.
Cytokine are a category of small proteins important in cell signalling and immune system activation. During an inflammation, they are produced in large quantity and are essential in cell communication. Those molecules can be pro-inflammatory or anti-inflammatory according to their type and the situation.
An inflammation has a beginning, a middle and an end. The main objective of the body is to quickly react to the stimulus to avoid losing health and then quickly reduce intensity of the immune reaction. This will help to come back to homeostasis and avoid losing too much energy.
Figure 1: Cytokine storm during infection (Castelli et al. 2020)
THE CASE OF TRANSITION COW
Peripartum cow faces many changes compared to late gestation cow: erratic feeding behaviour, altered blood flow pattern, tissue growth (liver and mammary) and specific catabolism (adipose tissue, muscle and bone). By nature, farrowing is a challenging process for cows bringing inflammation to its highest. Cows that experienced diseases or calving difficulties had significantly greater systemic inflammation. If this inflammation is too long or out of control, it can impair reproductive performances or milk quality (Figure 2). It is critical to monitor and control this inflammation process to avoid the complications described below.
To resolve this inflammation, providing anti-inflammatory precursor is a helpful tool.
Figure 2: Hypothesized responses to resolved and unresolved inflammation in early (Bradford et al., 2015)
BENEFIT AND LIMITATION OF USING POLY UNSATURATED FATTY ACID IN RUMINANT
We usually distinct Omega-6 and Omega-3 as Poly Unsaturated Fatty Acid (PUFA). Omega-6 are pro-inflammatory and omega-3 are anti-inflammatory.
Omega-3 are precursors of specialized molecule named Pro Resolving Lipid Mediator (SPMs). SPMs inhibit the synthesis of pro-inflammatory cytokines through the down regulation of a pro inflammatory pathway named NF-kB pathway.
Silvestre et al. (2011) showed that the Omega-3 profile of lymphocyteswas increased when dairy cows were supplemented withOmega-3. With a lipopolysaccharide challenge on the cow, authors show that of production of Tumor Necrosis Factor α (TNF-α is pro inflammatory interleukin, usually used as biomarker of inflammation) was attenuated compared with those from cows fed palm oil. Furthermore, there is evidence that overload of Omega-6 may inhibit the anti-inflammatory effect of Omega-3 (Hathaway et al. 2020). As Omega 6 and Omega 3 are both useful for a complete immune response, solution will be about the balance between those two PUFA families. Ratio Omega to Omega 3 must be closed to 5 in transition cow diet.
Corn, Soybean, Corn silage, Cottonseed are rich in Omega 6 and represent nowadays a main part of a cow diet.
For a transition cow, Omega-3 can be exclusively provided by dietary intake. Linseed is one of the richest sources of essential Omega-3 fats.
Linseed, as any other polyunsaturated fat source when left unprotected and introduced to the rumen, will be destroyed by biohydrogenation. Biohydrogenation can be responsible for milk fat depression syndrome and reduce milk economic value. Some specific process, like co-dry-extrusion between linseed and peas, can create a specific fat/protein matrix, providing necessary fat protection in the rumen with no biohydrogenation. Fat from linseed become a “bypass” fat and can be directly use by the cow itself.
Providing suitable source of Omega 3 during transition is very promising approach to overcome the general inflammation related to farrowing. It is preventive and long term approach but it will definitely improve longevity and wellbeing of the animal. A better understanding of the impact of this inflammation is still needed to develop the most efficient nutritional strategies.