Resumen de The effect of initial fattening weight on sustainability of beef cattle production in feedlots
The aim of this study was to conduct cultural energy (CE) analyses of beef cattle animals with different initial weights. Data were obtained by a questionnaire administered to 100 beef farms selected by stratified random sampling.
The beef farms were divided into three groups based on initial animal weights and were analyzed. Initial weights were assigned as light (< 226 kg, 37 farms), medium (226-276 kg, 31 farms) and high (> 276 kg, 32 farms). Cultural energy used for feed for the treatments was derived from their lot feed consumption and values from the literature.
Transportation energy was included in the analysis. As the objective of the study was to evaluate CE analysis of the feeding systems, energy that the calves had deposited in muscle and fat tissue, when they were purchased was deducted from carcass energy. Total expended CE was highest for the lighter animals (P < 0.05). Feed energy was more than half of total CE and again was highest for the lighter animals (P < 0.05). Energy expended kg¿1 live weight did not differ among the three initial weight groups (P > 0.05). Cultural energy Mcal¿1 of protein energy decreased as initial body weight increased (P < 0.05). Efficiency, defined as Mcal input Mcal¿1 output, was best in heavier cattle and was worst for lighter animals (P < 0.05) The medium weight animals did not differ from the other groups (P > 0.05). The results showed that efficiency became better as initial body weight increased and that to be more sustainable the initial animal weight should be taken into account.
