Modelling trimmed fat from commercial primal cuts

Abstract

A number of studies over the last five years have been conducted to determine total body fat (kg) in cattle and subsequently retail beef yield. Abattoirs are not consistent in the quantity of fat they trim off commercial bone-out primal cuts (e.g., striploin, cube roll etc.). The trimming of fat on a single primal by different abattoirs can range from 3 to 7 mm. If a relationship between mm of fat trimmed and kg of fat removed from primal cuts was developed then total body fat (kg) from commercial slaughters could then be estimated. The estimate of total body fat would assist in establishing a method for determining denuded yield which would then be used as a national standard for describing retail beef yield independent of abattoir. The estimate of retail beef yield would then be implemented into the BeefSpecs calculator.The objective of this study was to develop a relationship between trim (mm) and kg of fat removed. Images from X-ray computed tomography (CT) scans of 8 primal cuts from 10 Angus steers were manipulated to generate CT scan images for trims ranging from 0 to 15 mm. These images were analysed to determine the weights of fat and muscle in each primal, which were subsequently converted to ratios. Eleven non-linear growth functions were fitted to the generated data and compared to assess their ability to accurately predict the trimmed muscle ratio. The Schnute growth function was identified as the best fit model with the lowest AICc (corrected Akaike's Information Criterion) (AICc = -480.879, adjusted R 2 = 0.945, RMSE = 0.023). The proposed model (and parameter estimates) can be used to estimate the kg of fat removed and therefore aid in the estimation of retail beef yield.