Growth modelling of different ram breeds using computer tomography

In this study the growth of rams of 3 different sheep breeds with extremely different growth patterns (Hungarian Merino, HM; American Suffolk, AS; and Dutch Texel, DT) were modelled. Two models (modified Gompertz and logistic) were fitted to experimental data generated from successive computer tomography (CT) measurements. In each breed the data fitted the Gompertz model with better precision (lower RSS values). However, the symmetric logistic function fitted the late maturing fat and long loin of the AS lambs more accurately. These models have consequently been validated to give in vivo predictions of market specific products and the optimal slaughter weight of each breed. Based on the results of the Gompertz model, medium sized sheep breeds with low growth capacity (e.g. HM) should be slaughtered when their live weight is between 21 and 33 kg at an age of 3–5 months. The large-sized, slow maturing breeds (AS) should be slaughtered between 27 and 45 kg, at a similar age to the HM lambs. The early maturing breed (DT) should not be reared older than 2–3.5 months of age, with a live weight varying between 24 and 36 kg.