Healthy cows

it all starts with an easy calving

We all know that early metabolic diseases have a large economic impact on dairy farms. Disorders and problems like dystocia, ketosis, metritis, retained placenta, displaced abomasums have a huge impact on the amount of milk a cow will produce in the her current lactation, and the incidence of any one of these diseases can reduce the likelihood of the cow becoming pregnant. Pregnancy status generally has the largest influence on culling in commercial dairy herds. In fact a study of New York animals indicated that non-pregnant cows were 7.5 times more likely to get culled than pregnant cows (Grohn et al. 1998).

When thinking about the probability that a cow will conceive to a particular service, about 95% of that probability is influenced strictly by management and environmental conditions. That leaves about 4% for the genetics of the cow being inseminated, and 1% for the fertility of straw of semen being used. Why such a variation between some sires when looking at the BREDSUM reports, or other fertility reports? The answer is quite easy - it is because all the cows within your herd (within the same lactation and fresh around the same time) are generally exposed to very similar management and environmental conditions. Generally these cows have gone through the same sequence of events around calving, got the same treatment and care, and likely even live in the same pen and eat the same diet. However when looking at ways to improve your pregnancy rates or conception rates on farm, it is easy to focus on the fertility of the straw of semen (which remember only amounts to 1% of the variation), instead of focusing on the big changes that can really affect fertility on a much large scale.

Factors influencing fertility can stretch out over a lifetime, but the most important factors in a given lactation certainly start with an easy calving. If a cow has a difficult calving, she is more likely to tear, or retain her placenta, and is less likely to get up and eat. Certainly it is well documented that cows intake drops off substantially before calving, so if a difficult calving further extends the time a cow has a reduced intake, then she is more likely to get ketosis because of the fat reserves she must mobilize for energy. Ketosis increases the chance of displaced abomasums and any of these diseases early in lactation increase the chance of mastitis later on. The important take home point is that any of these diseases will have a large impact on the likelihood of that cow conceiving in a timely manner, and that non-pregnant cows are 7.5 times more likely to be culled than pregnant cows! So when trying to improve your pregnancy rate focus on the big picture - cows that stay healthy get pregnant, and cows that get pregnant stay in the herd!
Remember it all starts with an easy calving!

Easy calving = LOWER chance of early metabolic
disorders = LOWER chance of mastitis = HIGHER
chance of becoming pregnant = LOWER chance of being culled!

Don't forget to select HealthPlus sires - a line of cattle that excel in creating cows that stay healthy, get pregnant, and last in commercial environments!

Article by Nate Zwald
Advantage Program Manager

Grohn, Y. T., S. W. Eicker, B. Ducrocq, and J. A. Hertl. 1998. Effect of diseases on theculling of Holstein dairy cows in New York State. J. Dairy Sci. 81:966-978.

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Posted Oct 6th

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