Importance of Immunity in the Cow’s Annual Cycle

3 Critical Periods of Low Immunity

• At Drying Off
• 2–3 weeks Pre-calving
• New calf….first week of life

All steps along the cow’s annual health cycle are interrelated and depend on what was done previously. Failure to deal with one issue successfully will mean the next issue will be exacerbated. This is a type of “multiplier” effect. “What happens today is a direct result of what happened yesterday”.

Proper management of the cow during the dry period will mean fewer metabolic and infectious diseases over the transition period, better quality milk and colostrum, healthier calves and better fertility performance.

Immunity & Dry Period

One underlying concept the dairy farmer must be very aware of during the dry period are the two dips in immune function that every cow will experience. Experts say that in some cows, 75% of immune function is shut down over these dry cow periods. At drying off, the cow’s immune function is lowered as the cow switches from a lactating to a dry animal. This decrease in immunity before drying off is due to a number of issues, including the delay in keratin plug formation at the teat orifice and the decrease in the number and activity of protective white blood cells (leukocytes) around this period.

Immunity pre-calving

A second drop, in immunity, starts about two weeks before calving.  There are large demands on the cow as she nears calving and this can cause a significant decrease in her immune function, during the transition period. A huge amount of the nutritional and metabolic energy is diverted to the developing calf, as well as preparing for full milk production. This depletes the reserves left to the cow herself. Hence, it is not surprising that the cow may succumb to a variety of metabolic problems such as hypocalcaemia or ketosis/fatty liver, abomasal displacement or to post-calving infections such as mastitis, retained foetal membranes or metritis. Attention to body condition score is also critical to avoid metabolic disorders.

Post-calving

The formation of good quality colostrum can be assisted by an adequate supply of trace elements and immune boosters pre-calving. Failure to do this will also be manifested in a number of ways, especially in delays to the resumption of normal cycling and in very significant delays between calving and successful fertilization and conception. Because of the high energy turnover and intense metabolism at calving, toxic oxygen metabolites also occur in the cow at this time. This toxic oxygen radical can suppress the immune system leading to infection. Recent research highlights that using antioxidants such as vitamins A, D3 and E, as well as alpha-tocopherol or Beta Carotene, will reduce the incidence of mastitis post-calving. Close attention to the immune status during the dry period via the supply of effectively targeted and specifically formulated nutritional supplements will prevent higher rates of infections, perhaps hypocalcaemia, negative energy balance (NEB) and consequent episodes of metritis, mastitis, displaced abomasum or retained foetal membranes at calving. In addition, higher levels of NEFA (non-esterified fatty acids) and BHB (beta-hydroxybutyrate) will contribute to clinical or subclinical ketosis. The severity of metabolic disorders will delay the onset of the first heat, lower the conception rate and lead to longer calving intervals.

Failure to attend to the cow’s immune status can cost a lot of money!

Nutribio Nutritionist – Pat O’Byrne.

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