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High-grain diets have been used with great success in the feedlot systems for lambs production in Brazil. Then it became important to define the ideal dietary fiber content in the diet when the goal is to produce heavy lambs for early slaughter. The objective in this trial was to evaluate the levels of fiber on performance of lambs feed high-grain diet. Fifty-eight Dorper x Santa Inês ram lambs (initial BW 20.7 ± 1.19 kg and 75 ± 10.83 d old) were assigned to a randomized complete block design. The treatments were defined by the fiber (“Coastcross” hay) content in diets (CP: 16,12% ± 0.92): 0F: no forage diet (NDF: 10.4%); 5F: 5% of forage (NDF: 12.1%); 10F: 10% of forage (NDF: 15%); 15F: 15% of forage (NDF: 15.5%); 20F: 20% of forage (NDF: 20.8%) and 25F: 25% of forage (NDF: 23.5%). The experiment lasted 89 days and lambs were weighted after 16 hours fasting on days 0, 31, 57 and 89. DMI, ADG and FE were determined in each period. There was no interaction effect between diets and periods. There was a quadratic effect in DMI (0F: 0.96; 5F: 0.97; 10F: 1.04; 15F: 1.00; 20F: 1.02; 25F: 0.88 kg/d; P = 0.02), ADG (0F: 0.27; 5F: 0.26; 10F: 0.28; 15F: 0.28; 20F: 0.26; 25F: 0.21 kg/d; P = 0.01) and FE (0F: 0.28; 5F: 0.28; 10F: 0.28; 15F: 0.29; 20F: 0.26; 25F: 0.25; P = 0.05). Consequently, the increased levels of forage result in quadratic effect on final BW (0F: 44.5; 5F: 44.7; 10F: 46.1; 15F: 45.5; 20F: 43.9; 25F: 39.7 kg; P < 0.01). In conclusion, the inclusion of 10–15% of forage improves the performance of feedlot lambs feed high-concentrate diets, but it was proved the real possibility of finishing lambs with diet without forage source.

The objectives of this trial were to evaluate the effects of levels of fiber in high-grain diets on carcass characteristics of feedlot lambs. Fifty-eight Dorper x Santa Inês ram lambs (initial BW 20.7 ± 1.19 kg and 75 ± 10.83 d old) were assigned to a randomized complete block design. The treatments were defined by the fiber (“Coastcross” hay) content in the diets (CP: 16,12% ± 0.92): 0F: no forage diet (NDF: 10.4%); 5F: 5% of forage (NDF: 12.1%); 10F: 10% of forage (NDF: 15.0%); 15F: 15% of forage (NDF: 15.5%); 20F: 20% of forage (NDF: 20.8%) and 25F: 25% of forage (NDF: 23.5%). The experiment lasted 89 days, at the end of this time, the animals were slaughtered (169 ± 10.83 d old) to evaluate carcass characteristics. There was a quadratic response for slaughter BW (0F: 46.3; 5F: 48.1; 10F: 49.4; 15F: 50.3; 20F: 48.5; 25F: 43.3 kg; P < 0.01), hot carcass weight (0F: 24.8; 5F: 25.6; 10F: 26.0; 15F: 25.7; 20F: 24.3; 25F: 21.8 kg; P = 0.01), cold carcass weight (0F: 24.3; 5F: 25.1; 10F: 25.4; 15F: 25.1; 20F: 23.8; 25F: 21.2 kg; P = 0.01) and longissimus dorsis area (0F: 16.3; 5F: 16.5; 10F: 17.4; 15F: 16.5; 20F: 16.0; 25F: 15.1 cm2; P = 0.04). There was a linear decrease in the hot carcass yield (0F: 53.0; 5F: 53.3; 10F: 52.5; 15F: 50.9; 20F: 50.1; 25F: 50.2%; P < 0.01), cold carcass yield (0F: 52.0; 5F: 52.2; 10F: 51.4; 15F: 49.8; 20F: 49.0; 25F: 48.9%; P < 0.01) and body wall thickness (0F: 16.2; 5F: 17.0; 10F: 16.3; 15F: 16.3; 20F: 15.1; 25F: 13.6 kg; P = 0.01). There was no effect on subcutaneous fat thickness. In conclusion, the diet with up to 5% of forage allowed higher carcass yield; however, the heavier carcasses were produced by the lambs that received 10F diet.

The objective of this study was to determinate the effects of narasin on carcass characteristics of lambs fed a diet containing different levels. Forty-four lambs were allotted in a randomized complete block design, defined by initial body weight (BW), in a 2x2 factorial arrangement. The first factor was forage (coastcross hay) inclusion (10 or 20%, DM basis) and the second factor was narasin (0 or 13 ppm). The experimental diets were isonitrogenous (17.4%, DM basis). The experiment lasted 112 days. At the end of the experiment, the lambs were slaughtered to evaluate the carcass characteristics and meat composition. Data were analyzed using the MIXED procedure of SAS and the LSMEANS option was used to obtain the means. The effects were considered significant when P < 0.05. There was no interaction between forage levels and narasin inclusion. The experimental diets did not affect the slaughter BW (54.8 ± 1.6 kg), hot carcass weight (29.3 ± 0.96 kg), dressing percentage (53.5 ± 0.67%) and LM area (18.8 ± 0.89 cm2). The inclusion of narasin increased 12th-rib fat (2.10 vs 2.75 mm; P < 0.01) and BW thickness (16.9 vs 20.2 mm; P < 0.01). The inclusion of 20% of hay decreased BW thickness (19.21 vs 17.9 mm; P = 0.03). The experimental diets did not affect the moisture (74.2 ± 0.53%) and ash content in meat (1.27 ± 0.04%). Narasin inclusion increased the fat (2.81 vs 3.62%; P < 0.01) and decreased the CP (21.3 vs 20.7%; P = 0.02) in meat composition. The inclusion of 10% of hay increased the fat in meat (3.5 vs 2.9%; P = 0.03), however, did not affect the CP content. In conclusion, the narasin inclusion and levels of hay improve the carcass characteristics and change the meat composition.

The objective of this trial was to evaluate the effects of increasing levels of narasin in the diet of lactating ewes on dry matter intake (DMI) and average daily gain (ADG) of their lambs. Forty crossbred ewes Dorper x Santa Inês with their lambs were assigned to a randomized complete block design (10 blocks and 4 treatments). The treatments were defined by the inclusion of narasin to a base diet (16.8 ± 0.66 of CP) containing 50% of concentrate and 50% of Brachiaria brizanta hay, as follow: 0N - control diet; 13N - 13 mg of narasin/kg of DM; 20N - 20 mg of narasin/kg of DM; 27N - 27 mg of narasin/kg of DM. The experiment lasted from 14 to 70 days of lactation. From the second to the tenth week of age the lambs received initial concentrate (57.0% corn; 25.0% soybean meal; 1.5% limestone; 1.5% of mineral mix; 5.0% of sugarcane molasses and 10% of milk replacer; composition: DM=89.3%; CP = 21.1%; FDN = 8.9%; FDA=2.7%) (ad libitum) in a private feeder. All data were analyzed using the MIXED procedure of SAS. The lambs were weighed weekly after 5-hours fasting. The orts were quantified weekly to determine the DMI. There was no effect of the supply of narasin to the ewes on the DMI by the lambs (0N = 0.126; 13N = 0.088; 20N = 0.153; 27N = 0.145 kg/d; P > 0.05). However, the supply of narasin decreased the ADG (0N = 269.3; 13N = 259.60; 20N = 264.02; 27 = 228.01 g; P < 0.01) of lambs. In conclusion, the use of narasin for the ewes did not benefit lamb performance.