Document Type : Research Paper
Authors
1
Agricultural Research Education and Extension Organization (AREEO), Tehran, Iran, Animal Science Research Institute of Iran
2
Animal Science Research Institute of Iran, Agricultural Research Education and Extension Organization (AREEO), Karaj, Iran.
3
animal science research institute
Abstract
This study was aimed to optimize the suitable slaughter weight of Afshari fattening male lambs by using the feed conversion ratio curve and carcass tissue composition. Thirty-two Afshari male lambs, averaging 105±15.0 (SD) days of age and initial body weight of 30.2±3.6 (SD) kg, from the commercial herd in the Animal Science Research Institute of Iran were used. Metabolizable energy (ME) contents were, 2.79, 2.78, 2.72 and 2.69 Mcal/kg dry matter (DM) and crude protein (CP) contents were 146, 128, 109, and 103 g/kg for the 1, 2, 3, and 4 diets, respectively. The results showed, DMI and feed conversion ratio (FCR) had an increasing trend, with the increasing length of fattening period. The daily weight gains, had an upward trend from the beginning of the experiment to the 56th day, and then it decreased with a relatively small slope. Dressing percentage increased, with increasing length of the trail, so that it was significantly higher in the last stage of slaughter (55.3%) than the previous (52%). Weight percent of digestive tract (stomach and intestine), liver and, lung decreased but weight percent of internal fat increased, with a significantly difference, when experimental period increased. The highest percent of fat-tail weight, was observed in the last stage of slaughter (19.8) and the lowest was observed in the first stage of slaughter (14.2). Back fat thickness increased with increasing length of the experiment, so that a significant difference observed between the last stage of slaughter and the previous stages.
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