Energy efficiency of beef cow herds with different calving season in the south-east of Buenos Aires province, Argentina

RICCI, P.; AELLO, M.S.; ARROQUY, J.I.; REARTE, D.

Montpellier

Conferencia; 3rd Climate Smart Agriculture Global Science Conference; 2015

INRA

The aim of the study was to evaluate the energy efficiency of two beef cow herds with either autumn (AC, n=40) or winter calving season (WC, n=32), as gross energy intake (GEI) and methane (CH4) loss per kg of weaned calf. Energy requirements were estimated (NRC, 2000) from Aberdeen Angus cross Hereford cows (55 ± 14 months old) that continuously grazed Tynopirum ponticum and Festuca Arundinacea dominated pasture during 1 year in the in the south-east of Buenos Aires province, Argentina. Calves were weaned at 7 (AC) and 6 (WC) months old. Cow-calf body weight (BW) were registered over the year. Results were analyzed with MIXED procedure of SAS with calving season as factor. Annual GEI of AC was greater than WC cows (72 ± 4 vs. 58 ± 5 GJ.yr-1; P < 0.001). However, AC calves were heavier than WC at weaning (200 ± 23 vs. 141 ± 22 kg; P < 0.001). The energy cost per kg of weaned calf was 14% greater in WC than AC cows. Methane per kg of weaned calf of AC was lower than WC cows (426 ± 41 vs. 486 ± 68 g CH4.kg calf-1.yr-1; P < 0.001). The greater CH4 emitted by AC cows is counteracted by a higher performance of their calves, thus the energy efficiency was higher for AC than WC herds. The AC cows can have a longer lactation ending in spring, hence obtaining heavier calves at weaning. The AC could be suggested as a management alternative to reduce CH4 emission intensities and contribute to improving the efficiency of finishing period by obtaining a heavier calf at weaning. More studies are needed at a bigger scale to analyze interactions of this calving season alternative with other components of the system.