Distribution of tissues in carcasses at the same proportion of total fat in Portuguese cattle breeds

Abstract

A comparison was made of the distribution of bone, muscle, subcutaneous fat and intermuscular fat (g of tissue in the joint per kg of the respective tissue in the carcass) at the same pro- portion of total carcass fat for a total of 165 animals from three large (Alentejana (n = 24); Mirandesa (n = 24); Marinhoa (n = 24)), and four small, (Arouquesa (n = 24); Barrosa (n = 23); Maronesa (n = 24) and Mertolenga (n = 22)) Portuguese breeds, serially slaughtered at three different weights. The distribution of muscle was significantly different across breeds in a larger number of joints than either the distribution of bone, subcutaneous fat or intermuscular fat. However, the range of differ- ences in each joint was narrower for muscle. So, amongst the first class joints (leg, sirloin, ribs and fore ribs), only the sirloin and the fore ribs, both with a range across breeds of only 7 g·kg -1 ,w ere sig- nificantly different between breeds. On the contrary to subcutaneous fat, the proportions of intermuscular fat tend to decrease, particularly in the leg. As expected, the joints with homogeneous parameters were the most accurate for predicting the proportion of muscle (g·kg -1 ) in the carcass from the proportion of muscle (g·kg -1 ) in the joint. For the large breeds, the most accurate joints were the leg and the coast, with a residual s.d. of 13.91 g·kg -1 and 18.45 g·kg -1 , respectively; and for the small breeds the most accurate joints were the fore ribs and the leg, with a residual s.d. of 15.35 g·kg -1 and 17.11 g·kg -1 , respectively. The difference between the actual breed means and the means predicted using the overall equation for each of the most accurate joints were lower than ± 4 g·kg -1 for all breeds with the exception of the Barrosa with a value of -8 g·kg -1 .