Better breeding improves financial results

Better breeding improves financial results

All dairy farmers are breeders although breeding aims may differ among herds. Some farmers breed show cows while others produce sires for the artificial insemination (AI) industry. However, total milk output should always be the main breeding and management emphasis of dairy farmers. Most dairy herds show an increase in total milk yield over time. This is mostly because of an increase in the number of cows in the herd. Environmental improvements such as a better feeding programme, housing and management and rearing of replacement heifers often also result in a higher milk output. Of more importance, however, is a higher milk yield per cow because of genetic improvement for milk yield. This is the result of bull selection for AI and the cows that are selected to stay in the herd.

Some dairy herds show little or no improvement in milk yield. Worse even is a reduction in milk or component yields over time. As the milk produced by the herd contributes more than 90% of the total income of a dairy farm, this of course affects the financial situation of the operation. Financial sustainability of a dairy farm depends on cows producing the most milk at the lowest cost. The feeding and management cost on any dairy farm is a relative constant, therefore the genetic input in a herd should have a substantial effect on the financial situation in a dairy herd.

Selecting bulls

Even without any change in the management level of a dairy herd, most herds using semen from a specific semen company should show an improvement in milk yield when selecting and using AI bulls in the top 10% in terms of milk yield. The reason for this is that bulls becoming available for insemination improve over time. There are always young bulls that come out of the progeny testing programme that are better than old bulls in terms of milk yield. Recently the genetic merit of bulls is known even earlier through genomic testing. Problems occur when dairy farmers select bulls to improve some conformation traits in cows while disregarding the bulls’ milk production potential. If this is kept up for a long enough, milk production in the herd may decrease resulting in a negative effect on the financial situation in the herd. For instance, a specific bull is selected to improve the udder conformation of cows in the herd. When such a bull has a negative breeding value for milk yield this results in cows producing less milk. Milk production in a herd is always more important than most body conformation traits.

Herd profiles

Dairy farmers taking part in the official milk recording scheme have an easy way to monitor the herd’s change in milk yield and milk components over time. This is provided by the herd profiles that these dairy farmers receive once a year. One doesn’t have to be a geneticist either to see in which direction your herd’s genetic profile for milk yield or milk components is moving. If the trend lines go up at the same trend as the national herd, progress is sufficient, and the breeding programme is working. If, however the profiles go in any other direction or up and down from one year to the next, it only means that you have selected the wrong bulls some time earlier. Then the breeding programme requires a major change as it is not going anywhere really.

Keep in mind that the present dairy herd is the result of the selection of cows and bulls some 4-10 years earlier. Dairy cows have long generation intervals, and one only starts seeing the results of bulls selected today in four years’ time. This time interval is made up of the 9-12 months from today before the first heifer calf is born. After that another interval of 24-30 months is required for heifers to grow up to first calving after which another 10 months will lapse before the first lactation is completed. This, of course, is then only the first progeny of a specific bull and one needs at least 20 daughters of a bull to really evaluate a specific bull’s genetic and milk production potential. This means that dairy farmers cannot really evaluate bulls in their herds as they don’t have time to do it. The breeding values of bulls that AI companies provide already tell what a specific bull is worth and dairy farmers don’t have to do it again. Breeding values of bulls also include reliability values and bulls should be used according to these figures. High reliabilities mean that you can use a bull with certainty and low values indicate that you should such a bull with circumspect.

Because dairy farmers try and keep their cows if possible in their herds it means that a wrong bull in terms of milk yield potential selected at any time will have a negative effect on the herd for a long time. The repeatability of the milk yield of dairy cows is also relatively high meaning that daughters of a bull with poor milk production potential will have lower productions in their first lactation and all other lactations while they are in the herd.

Genetic progress

The effect of sire and cow selection affects the genetic progress of a dairy herd. Early breeding in a specific herd showed that little attention was put on high milk yields. Line breeding to improve body conformation traits or type was the main emphasis. A breeding policy to improve milk yield was then adopted. This entailed that top AI bulls from the South African progeny testing scheme were selected based on their breeding value for 4% fat corrected milk (FCM) yield. Calving ease bulls were selected similarly to be used on heifers. At the same time selection threshold values based on the FCM yield of first lactation cows that had completed a first lactation in the herd were estimated. The correlation between the first 60d and 300d were estimated (see the following figure) to determine the possibility of identifying poor performing cows early. A significant correlation (R2>0.57) means that the milk yield of cows over the first 60d is a good indication of 300d (lactation) milk yield. However, the correlation between the milk yield of cows over the first 90d and 300d milk yield was higher at R2=0.67. This provides a better indicator of milk yield potential. At subsequent milk recording events the 90d FCM yield of first lactation cows were estimated. Cows producing less than the selection threshold values were identified for culling. Cows that were borderline cases for FCM yield were kept in the herd and evaluated again at the end of first lactation.The full article is for subscribed members only. To view the full article please subscribe. It’s FREE!Log In Register

Author

  • Research Associate, Faculty of Animal Sciences, University of Stellenbosch

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