Production of organic beef from dairy bull calves in Denmark - Effect of different production strategies on productivity, carbon footprint and biodiversity estimated by modelling

Abstract

In Denmark, organic male calves from the dairy system are typically raised as steers leading to a high carbon footprint per kg meat produced, compared to other types of rearing. Therefore, there is a need to find mitigation options and develop future production systems with a lower climate impact. The aim of this study was to develop strategies for the rearing of organic bull calves considering the following factors: season of birth, feeding strategy, age at slaughter, and breed-type, where all strategies focus on achieving the lowest possible carbon footprint per kg carcass. A total of 10 strategies were compared for each of three breed types: Holstein, Charolais x Holstein, and Angus x Holstein. The carbon footprint was estimated using Life Cycle Assessment including all emissions until the animals leave the farm for slaughter and expressed per kg carcass taking into account different dressing percentages due to breed and age at slaughter.The carbon footprint per kg carcass including contribution from soil carbon changes was 18–32% lower for raising organic young bulls compared with that of organic steers. The strategy with a high feeding intensity and a slaughter age of 13 months had the lowest carbon footprint per kg carcass due to the lowest feed consumption per kg live weight gain (4.9 kg DM compared to 7.4 kg DM for the steer) and use of a high proportion of concentrated feed in the ration. In the strategy with slaughter age of 17 months, but the same high feeding intensity, carbon footprint per kg carcass increased around 6%. This was due to an increase in feed consumption and reduction in feed conversion due to the increasing age at slaughter. The strategy with a low feeding intensity and a high slaughter age (17 months) gave the highest carbon footprint per kg carcass amongst the rearing strategies compared for organically produced bulls, as a greater proportion of roughage in the ration increases enteric methane production from the digestion of the feed. The crossbred bulls compared to purebred dairy bulls had a lower carbon footprint (4–7%) due to higher dressing percentage, higher carcass weight (both types of crosses), and higher growth rates (Charolais crosses).