Effect of different levels of ration concentrate and length of fattening period on fattening performance and carcass characteristics of Lori lambs

Background and objectives: One of the important and fundamental issues of breeding livestock is proper and economical diet. During the last few years, the limitation of feed resources is considered one of the major problems of the livestock breeding industry in the country. The use of concentrate in the diet of fattening lambs in the country is normal and usual, but what is important is the appropriate level of concentrate and the appropriate length of the fattening period for the economy of lamb fattening. Therefore, Therefore, considering the fattening of 320,000 lambs in Lorestan province and in order to promote the use of the appropriate proportion of concentrate and length of fattening in the fattening of lambs, the above project aims to investigate the effect of diets with different levels of concentrate and the most suitable length of fattening on fattening performance and carcass characteristics, Lori male lambs were performed.
Materials and methods: Based on this, 54 male lambs with an average age of 4 months weighing 30±0.75 kg were selected. The treatments included two levels of length of fattening (90 or 120 days) and three levels of concentration (60, 70 and 80%). Experimental diets with using the standard tables of food requirements of small ruminants and based on the requirements of a 30 kg lamb. The end of the experiment, daily weight gain, final weight, feed conversion ratio and feed consumption were calculated and then three lambs from each treatment were slaughtered and carcass characteristics were calculated. Performance and carcass traits data were analyzed in a factorial exprimental with a completely random design (3x2) with two factors including the length of fattening at three levels and the percentage of concentrate at three levels with three replications (each repetition includes three lambs) by the mixed method of covariance analysis. Comparison of treatment means was done using Tukey's test.
Results: The results showed that the effect of length of fattening and ration concentrate level on weight gain, feed consumption and feed conversion ratio was significant (P<0.05). The highest daily weight gain was related to lambs fed with 70% concentrate (232 gr) and a fattening period of 90 days, and the lowest daily weight gain was in lambs fed with 60% concentrate (178 gr) and a fattening period of 120 days. Lambs fed with 70% concentrate and fattening for 90 days had a better feed conversion ratio(6.41). The highest carcass efficiency, cold carcass weight without tail and percentage of lean meat were related to lambs with length of fattening of 90 days and 70% concentrate (P<0.05). The production cost of each kilogram of carcass and meat was lower in lambs fed with 70% concentrate and fattening for 90 days. The results indicated that the duration of fattening and the level of concentrate in the diet had no significant effect on quality characteristics such as pH and meat color, as well as the chemical composition of the meat, including moisture, protein, and ash content (P>0.05). However, they had a significant effect on the fat percentage of the meat (P<0.05).

Conclusion: This study determined that the lambs fed with 70% concentrate and fattening for 90 days had a better feed conversion ratio due to higher weight gain. Also, lambs fed with 70% concentrate and fattened for 90 days had less total carcass fat and more loin meat.