Southern Cape & Karoo
How to monitor reproduction management in a dairy herd
10:37 (GMT+2), Mon , 03 February 2014
Southern Cape & Karoo
The fertility performance of dairy cows is decreasing worldwide. This is being attributed to the continued selection for higher milk yields.

However, research has shown that in well managed dairy herds reproduction performance of cows could be high regardless of high milk yield levels.

Decreased fertility in dairy herds could be the result of increasing herd sizes, more workers not familiar with the reproductive cycle of cows and poorer environmental conditions.

In a large dairy herd, individual high performance cows do not always get the best attention. Additional problems may be caused by poor heat observation and insemination techniques.

In spite of this, many producers have very successful reproduction management programmes. These producers pay particular attention to critical management indicators to prevent a decline in the reproduction management of their dairy herds as a turnaround in reproductive performance takes a considerable time.

Many managers use calving interval (CI) as a reproduction management indicator. However, this figure could be misleading as it refers to only those cows that have calved down again. Cows not calving again are excluded from the estimation. For instance, a CI of 420 days implies that only 87% of the cows in the herd had calved down within a 12-month period.

Reproduction management of a herd should be monitored on an ongoing basis so that declining trends in fertility can be observed early on. This means reproduction performance should be monitored at least every month. Fertility in dairy cows is defined by three indicators, i.e. (1) to show heat soon after calving, and (2) to become pregnant with a minimum number of inseminations and (3) to remain pregnant until the next calving.

Characteristics described by the first indicator of the definition are the interval (number of days) between the calving date and first insemination date as well as whether first insemination was within 80 days. This is presented as a percentage. The second indicator is the number of inseminations per conception. This shows the insemination efficiency of the inseminators. The inseminator efficiency is 50% when two inseminations per conception are required. This figure should be estimated for each inseminator.

Poor performers should be retrained or replaced, while good performers should be rewarded. The third indicator refers to the interval (number of days) between the calving date and conception date (also referred to as "days open").
From this, two additional fertility traits are obtained, i.e. whether cows became pregnant within 100 or 200 days after the last calving date. These two traits are presented as percentages. By estimating these figures on a regular basis, for example following monthly pregnancy checks, graphs could be prepared to monitor the progress for each trait.

These management indicators should be compared against available norms. In the current economic climate, producers should act according to a goal orientated plan. It is no use waiting until the milk yield of the herd is at a very low level due to many cows in the herd being in a late stage of the lactation or when only a few heifers have been born.

Article by dr Carel Muller, Western Cape Department of Agriculture - 021 808 5228, 082 907 1139.

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