Cow productivity in beef cattle is measured as kilogram calf weaned per mature livestock unit (MLU) mated. The traits influencing cow productivity are weaning weight of the calf and the feed requirements of the cow-calf combination.
For this purpose, MLU, linked to daily feed intake and the frequency at which a calf is produced expressed as the intercalving period (ICP), is used.
South African scientists studied the changes in Afrikaner cow productivity from 1980 to 2013. Weaning weight increased by 20,4kg, cow weight decreased by 8,3kg and ICP decreased by 19,7 days since 1980, increasing cow productivity by 18,3%.
In South Africa, the enteric methane emissions factor (MEFenteric), or carbon footprint, of one MLU is approximately 94kg/ year for beef cattle. In the case of the Afrikaner, the MEFenteric was 1kg/ kg calf weaned per MLU in 1980. This had decreased to 0,88kg MEFenteric in 2013, a reduction of 12%.
This improvement in cow productivity in the Afrikaner reduced the carbon footprint, and thus the environmental impact of beef production in this breed.
The livestock industry has a responsibility to limit the release of greenhouse gases (the carbon footprint) and water use (the water footprint) to ensure future sustainability. This can be done through improved production efficiency, which will reduce greenhouse gas (GHG) production in the long term, as higher productivity will probably improve gross efficiency.
Increased productivity generates less greenhouse gases per unit of livestock produced. A study by Capper, published in 2011, compared the environmental impact of modern (2007) beef production in the US with that of production practices of the beef production system in 1977.
It concluded that modern beef production required considerably less resources than the equivalent system in 1977. Improving productivity is thus the key to reducing the environmental impact of beef production.
Improving cow productivity
One way of improving cow efficiency is by increasing the weaning weight of calves in relation to cow MLU in an extensive beef cow-calf production system. MLU reflects the feed input required to sustain the cow and enable her to provide for the calf.
Using this measure of cow efficiency and linking it to the frequency at which a calf is produced (expressed as the ICP) enables cow productivity to be estimated and defined as kilogram of calf weaned per MLU cow mated.
The Afrikaner is among the oldest indigenous breeds in Southern Africa, dating back to the late 14th century and being closely associated with the history of the region and its people. It is classified as a Sanga breed – that is, indigenous to Southern Africa.
The Afrikaner (southern African Sanga) can be described as a taurine tropical adapted breed, which makes the breed fairly unique. Its breeder’s society, founded in 1912, was one of the first in the region.
Over the last two decades, Afrikaner breeders have focused on economically important traits in the modern beef production environment. Performance recording is compulsory, although not enforced.
The Afrikaner cow’s small to medium frame makes it the ideal dam line for producing heavy weaners in crossbreeding systems.
The definition of MLU used in this study is a 450kg steer gaining 0,5kg/day on forage with a mean digestible energy of 55% (75mJ metabolisable energy/ day). This study used breed frame-size-specific equations to estimate MLU units, since animals of the same body weight but with different frame sizes have different MLU units.
This is based on the principle that there are differences in the voluntary feed intake between such animals, although they have the same body weight.
Three traits that influence cow productivity were used in this study:
- 205-day corrected weaning weight of the calf;
- Feed requirement of the cow to produce the calf (expressed in MLU for this purpose as this is linked to daily feed intake);
- The frequency (ICP) at which calves are produced to estimate calving percentage.
Cow productivity (CP) is expressed in the equation:
CP = [205-day corrected weaning weight of calf / cow MLU equivalent] x calving percentage.
In South Africa, the enteric methane emissions factor (MEFenteric/MLU) is about 94kg/ year for beef cattle. This value was used to estimate the MEFenteric/kg calf weaned.
Table 1 depicts the phenotypical changes in the three basic traits and their effect on cow productivity over the 33 years. Weaning weight increased by 20,4kg, cow weight decreased by 8,3 kg, and ICP decreased by 19,7 days to increase cow productivity by 18,3%.
Using the MEFenteric value of 94kg/year/MLU in beef cattle, it was estimated that, in 1980, the MEFenteric in the Afrikaner was 1kg/kg calf weaned. This had decreased to 0,88kg MEFenteric/kg calf weaned in 2013, a reduction of 12%.
The result indicates that cow productivity can be improved by increasing the weaning weight of the calf relative to the weight of the cow and reducing the intercalving period. In the case of the Afrikaner, increasing the cow productivity by 18,3% had significant environmental impact as it reduced the MEFenteric by 12%.
Capper (2011) reported that productivity improvements due to improved genetics, nutrition and management between 1977 and 2007 had reduced GHG emission/kg beef produced in the US by 16% over this period.
Reduced carbon footprint
The result demonstrated that improving cow productivity in the Afrikaner reduced the carbon footprint and thus the environmental impact of beef production.
The relatively large positive environmental impact of increasing fertility (reflected by a reduced ICP) illustrates how important it is to improve the relatively low current calving rate (65%) in the SA national beef herd.
If the environmental impact of beef production is important, the issue of fertility and identifying the reasons for the low calving rate of beef cattle in South Africa deserves more attention.
A similar study on the major beef breeds representing the Sanga, Sanga-derived, Zebu, Zebu-derived, British and European breed types should be conducted in South Africa.
Email Prof Michiel Scholtz [email protected]