The hypertrophied Marchigiana is a recently studied genotype that can appear in this population both as homozygous and heterozygous; as a matter of fact it is caused by a single base mutation of the myostatin gene. The mutation is a G to T transversion at nucleotide 874 in exon 3, known as E291X. The homozygous one's show some problems such a low viability, on the contrary heterozygous seem to have a very good performance in meat production. Usually the breeders don't like very much homozygous hypertrophied genotype but they are attracted by the good conformation of the heterozygous. The aim of this study is to compare the performance on meat production of normal (no hypertrophied - N) versus heterozygous (E) calves in order to evaluate if there is some economic convenience in rearing the last one. The genotype identification was performed by a rapid PCR-RFLP test for the myostatin gene (AF320998) using genomic DNA purified from whole blood. The main growth and slaughtering traits were evaluated on 279 animals: 227 normal (186 males and 41 females), 52 heterozygous (47 males and 5 females). The data were processed according to a linear model concerning with the effects of genotype and sex. The net live weights are similar in the males (N: 614.63 vs. E: 614.47 Kg) but different (P<0.01) in the females (N: 447.83 vs. E: 464.40 Kg) because the heterozygous were slaughtered at an older age (N: 15.8 vs. E: 17.0 months). The daily gains are a bit higher in the normal calves, the differences between the two genotypes are more evident (P<0.05) when the live weight are considerated. The dressing percentage on live weight seem to be homogenous (close to 64%) except in the normal males (62.41%); but the more informative dressing percentages on net live weight show better performance (P<0.01) in the heterozygous both in the males (N: 68.85 vs. E: 71.25%) and in the females (N: 68.72 vs. E: 69.14%). All the bones measures (bones, fore and hind shanks, hool, head) are smaller (P<0.05) in the heterozygous showing proportionally a larger quantity of meat in this genotype. Also the entrails and the skin are smaller in the heterozygous; on the contrary in this genotype the tongue is larger confirming the macroglossy already detected in the hypertrophied Marchigiana mainly in the homozygous. The SEUROP evaluation allow to well appreciate the good performance of the heterozygous as a matter of fact these animals have a higher grade of numerically expressed conformation (E: 4.58 vs N: 4.42 in the males and E: 4.00 vs. N: 3.80 in the females) and a lower grade of fatness (E: 2.30 vs. N: 2.63 in the males and E: 2.80 vs. N: 2.98 in the females). The obtained results show that the heterozygous animals have good performances at slaughtering with good carcasses; at the same time doesn't show the negative defects of the homozygous subjects.
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