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The effect of different sources of energy (lipids and carbohydrates) was studied on 36 Apennine male lambs divided by age, weight and paternity into three homogeneous groups receiving three different diets: lambs on diet 1 received ad libitum lucerne hay + concentrate supplemented with barley flakes (9%) (BC); lambs on diet 2 received ad libitum lucerne hay + concentrate supplemented with maize oil (5%) (MC) while lambs on diet 3 received only the concentrate given in diet 2 (MC). The two concentrates were isoenergetic and isonitrogenous. Lambs were slaughtered at 105 days of age. The conversion indices were similar (4.52, 4.77 and 4.61 Meat FU/kg gain) for the three treatments, but the diet 3 led to heavier carcasses (17.57 kg), although with greater adipose covering, and better dressing percentages than the other two diets. The histological dissection of the proximal pelvic limb indicated a good tissue composition (total lean 56.16%) but confirmed the higher fat percentage (total fat 16.24%), particularly subcutaneous (11.44%), of the group receiving only MC. Animals on diet 3 gave carcasses with an adequate commercial weight at the age of 90–95 days and therefore it seems possible to anticipate slaughtering these animals earlier and perhaps obviate the excessive adiposity of the carcass. In general, this study further confirmed the good meat quality of Apennine carcasses slaughtered at 105 days.

Two groups of ten Massese lambs were given free access to a complete diet with or without monensin. Monensin sodium was given at 10 p.p.m. (wet basis) from 7 days of age up to 1 week after weaning (49 days of age), and 20 p.p.m. (wet basis) from this age to slaughter (105 days of age). Growth rate, feed conversion rate, fifth quarter components, linear measurements of full and half carcasses and commercial meat cuts were studied in the two groups. Histopathological examination of the liver, and chemical analysis of the semitendinous muscle were also made and residual traces of monensin were tested in the semitendinous muscle, liver and kidney. Treated-group liveweight was higher than that of controls throughout the trial period (2 weeks old; P < 0.05). Overall feed conversion (expressed as kg DM ingested kg−1 weight gain) in the first 42 days was lower in the monensin group (1.58 vs. 1.67), while the control group produced lower values both overall (days 1–105, 3.79 vs. 3.92) and in the second half of the trial (days 43–105, 5.00 vs. 5.31). A significant reduction in growth was seen in the treated animals in two periods: 2 weeks after solid feed was available (weight check at 21 days of age), and again 1 week after the switch from the weaning ration to a fattening diet (weight check at 56 days of age). Lambs in the experimental group had each ingested a quantity of monensin sodium equal to 0.011 mg from 7 to 42 days of age, and 0.796 mg from 43 to 105 days of age. Monensin sodium had only modest effects on quantitative and qualitative properties of lamb meat. Significant differences were found between the two groups with respect to the head (P < 0.05) and coratella (P < 0.01), which accounted for a greater percentage of BW in controls than treated animals. Upon carcass sectioning, the neck and abdomen of control animals showed a higher degree of development (P < 0.05), and peri-renal adipose tissue was more abundant in controls (P < 0.01). Feed conversion related to warm carcass (kg total ingested DM kg−1 warm carcass) was lower in controls. Linear measurements resulted in differences in trunk length (P < 0.05). The liver of the treated lambs was the only organ found to contain monensin residues, which ranged from 0.022 to 0.067 p.p.m. Owing to the paucity of data in the literature, it is not possible to define the maximum critical level. In conclusion, monensin sodium does not seem to be a good growth promoter in lambs, slaughtered at 105 days of age.