Can You Afford to Skip a Heat?

Dairy cow fertility is the driver behind successful dairy farms. A fertile dairy cow who conceives as early as possible to maintain her calving date year to year is the goal animal for our farms. There exist many influences on the successful conception of a dairy cow, some influences include management, nutrition and genetics.

A skipped heat during the breeding period represents a failure of breeding. Any failure of breeding has a financial implication and can delay the calving date. This then requires unplanned changes in the farm fodder flow program. Every additional day that the cow is empty represents a cost to the farm for the additional feed and semen straws required. Skipping a heat can be attributed to one or more of the following four factors:

One major influence on the potential fertility of the herd is the transition period, generally regarded as the period of 60 days prior to calving and the 30 days following calving. This period is categorized by intense nutritional and hormonal changes in the body. These major physiological changes need to be considered when evaluating the possible conception following calving.

The energy requirements of a cow doubles soon after calving, resulting in a negative energy balance in the body. With increasing time for the cow in a negative energy balance comes an increased risk for skipped heats and reproduction inefficiencies. Meeting the macro nutritional requirements (protein, fat, energy) following calving is the first hurdle in ensuring the cow is able to reconceive. Overcoming the negative energy balance requires an allowance for the animal to maximize its intake of a high-quality feed as soon as possible after calving, which is part of ensuring reproductive efficiency.

Reproductive efficiency can be improved through energy and protein supply from the diet, but the full potential is only unlocked through vitamin and mineral feeding. Following calving, the requirements for many minerals increase to support lactation or to repair damage to the reproductive organs.

An improvement on the conception rate can be attributed to various trace minerals such as copper, zinc, manganese and selenium etc., enacting different functions in the body. Trace mineral supply and balance greatly influences fertility i.e., the ovarian activity in ruminants, as well as the synthesis of hormones (steroidal and thyroid hormones) essential for reproduction. The main factor behind low production and suboptimal reproductive efficiency of livestock is due to inadequate nutrition, particularly due to mineral deficiencies. Any mineral imbalance is detrimental for reproductive efficiency due to minerals’ role in follicular dynamics, ovarian activity and fertility. Reproductive failure may be induced by deficiencies of a single or combination of minerals or by their imbalances. The following minerals have major roles in reproductive performance but are in no way the only minerals involved in this crucial process:

is involved in all contractions of muscles throughout the body. Calcium is involved in maintaining the tone of the uterus and uterine involution. Low blood calcium levels can lead to slower uterine involution and increased risk for retained membranes.

shortages in dairy cows can lead to delayed or suppressed oestrous, impaired ovarian function and infertility. The adequate serum copper level of dairy cow has positive effect on reproductive health leading to less days to first service, fewer services per conception and fewer days open.

along with vitamin E acts as protective and anti-oxidant in the body by removing the free radicals from the body. In pregnant animals a marginal deficiency of selenium leads to abortion or birth of weak calves that are unable to stand. Selenium supplementation reduces the incidence of retained placentas, cystic ovaries, mastitis and metritis.

plays an essential role in the maintenance and repair of uterine lining after calving, helping with early involution. Deficient levels of zinc can be linked with decreased conception rate, abnormal oestrous and abortion. Furthermore, zinc is involved in enzyme systems which work to support pregnancy. Zinc supplementation improves the Beta Carotene levels in the blood which is required for the maintenance of pregnancy.

While protein, fat and energy nutrition are important for the overall reproductive performance of dairy cattle we can see the role vitamins and minerals play in reproductive efficiency on a farm. The targeted inclusion of minerals through the transition period is a vital tool to ensure that more of the cows are ready for breeding at the goal date for the farm. The dairy industry cannot afford poor reproduction on the farms and needs to evaluate the true cost of skipping heats.

Rhys Sims
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