201 Precision of gain estimates for beef cattle with an automated weighing system

摘要

Current standard protocols for feed efficiency trial in beef cattle require a trial period of at least 70 days. This was determined to be the minimum trial duration to obtain adequate estimates of average daily gain with infrequent collection of animal weights. Modern automated weighing systems (e.g., GrowsafeBeef, Intergado) enable collection of multiple body weights each day without the need to handle cattle. Due to the high volume of data generated, it is likely that adequate estimates of rate of gain may be obtained with a shorter trial duration. Data were obtained during two consecutive feed efficiency trials (21 and 22) with yearling Nelore bulls at Rancho da Matinha, Uberaba, Brazil. Individual ADG were estimated by regression of BW vs. time. During Trial 21, body weights were taken by manual weighing every 14 days, for 70 days. Trial 22 involved automated weighing (Intergado) for 49 days. For Trial 21, the mean ADG was 1.113 (se 0.1079) kg/d, and 95% of the animals had se below 0.2 kg/d. In Trial 21 with automated weighing, the mean ADG were 1.248 (se 0.542), 1.164 (se 0.430, 1.097 (se 0.351, 1.114 (se 0.254) and 1.080 (se 0.234) after 14, 21, 28, 35, 42 and 49 d, respectively, and 85% had se below 0.3 kg/d. These findings suggest that precision of estimates of ADG is a valid criterion to determine optimal trial duration. Further study will be required to determine optimal trial durations for different types of cattle, diets and facilities.