South African Journal of Animal Science
versão On-line ISSN 2221-4062
The efficiency of energy utilization is one of the key indicators for developing more sustainable agricultural practices. Factors influencing the energy demand in dairy farming are the cumulative energy demand for feed-supply, milk yield as well as the replacement rate of cows. The energy demand of dairy farming is assessed on the basis of direct and indirect energy inputs. The comparison of different replacement rates and milk yields shows clearly that both have a considerable influence on the energy intensity of dairy farming. The feed energy requirement/kg milk produced is decreased with an increase in individual performance of the animals. Nevertheless, this effect diminishes gradually with milk yields higher than 8 000 kg/cow/year. Additionally, energy demand increases with higher replacement rates of cows. Milk yields higher than 8 000 kg/cow/year can clearly not compensate for the increase in the cumulative energy demand. Therefore milk yields considerably higher than 8 000 kg/cow/year are not advisable from the view-point of the cumulative energy demand for feed-supply. A decreasing service life of the dairy cows (increasing replacement rate) causes a higher energy demand per kg milk, but its influence is only marginal.
Palavras-chave : Energy balance; milk production; milk yield; replacement rate; sustainability.