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One of the main goals of the feedlot industry is to increase efficiency in the final stages of fattening. Therefore, the use of modulators of growth (hormones and beta-agonist agents) is widespread. The concern about the potential impact of the use of these growth promoters has furthered interest in the search for safe alternatives of modulating agents of growth in recent years. In this regards, the use of chelated minerals has shown interesting advantages in nonruminant species. In this sense, chromium (Cr) supplementation, as Cr propionate or Cr methionine, has shown increases in the percentage of carcass muscle and decreased carcass fat in pigs and poultries (1). In ruminants, Cr requirements have not been clearly established (2) and there is limited information available on the effects of Cr on carcass characteristics in feedlot cattle (3) and in feedlot lambs (4). In a recent study (5), linear decreases (P = 0.02) in kidney-pelvicheart fat and fat thickness were observed in finishing steers supplemented with chelated Cr (as Cr-enriched yeast) at daily levels of 0, 5, 10, or 15 mg/head. According to the above study, the maximum response levels were observed when cattle were fed with levels three-fold what is currently recommended. There is limited information regarding the effects of high levels of Cr supplementation on carcass characteristics and chemical composition of muscle of finished lambs. Therefore, the aim of this trial was to evaluate the effects of feeding different levels of chromium methionine on the carcass characteristics and chemical composition of the longissimus muscle (LM) in hairy lambs fed a high-energy diet. Twenty-four Pelibuey × Dorper (initial weight at start of experiment: 24.9 ± 0.2 kg) were assigned (six lambs/treatment) in indoor facilities in collective pens of 16 m 2 with automatic waterers and 1.2 m fence-line feed bunks. Lambs were fed ad libitum with a finishing diet formulated as follows (dry matter basis): 61.2% ground maize, 14.5% soybean meal, 12.6% Sudan grass hay, 7.7% molasses cane, 2.5% mineral premix, and 1.5% zeolite. The calculated composition of the basal diet dry matter basis (6) was as follows: crude protein, 17 g/kg; metabolizable energy, 12.09 MJ/kg; ether extract, 29 g/kg; calcium, 98 g/kg; and phosphorus, 36 g/kg. Lambs were adapted to the basal diet and facilities 14 day Abstract: Twenty-four male lambs (24.93 ± 0.93 kg) were used in order to evaluate the effects of chromium methionine (Cr) supplementation in high-energy finishing diets on the carcass characteristics and chemical composition of the longissimus muscle (LM). Treatments were 0.00, 0.60, 1.20, and 1.80 mg Cr/lamb daily. The experiment lasted 56 days. There were no effects of treatments on dry matter intake, feed to gain ratio, and final weight, which averaged 35.24 ± 1.01 kg. Supplemental Cr linearly decreased fat thickness enough to improve the estimated yield grade from 1.82 to 1.42 with no effect on the other carcass traits measured. Fat concentration in the LM decreased linearly as the lev...

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Mechanical maceration enhances site and extent of digestion of low-moisture, low-quality forages. Four Holstein steers (172 ± 8 kg) with cannulas in rumen and proximal duodenum were used in 4x4 Latin square design to evaluate the process of mechanical maceration of sudangrass hay on the characteristics of ruminal and total tract digestion. Treatments consisted of a steam-flaked corn-based growing diet supplemented with 21 % forage (DM basis) as: i) wheat straw (Triticum aestivum, STRW), ii) sudangrass hay (Sorghum sudanense, SG), iii) macerated SG at intensity of 4,134 kPa (MAC600) and 4) macerated SG at intensity of 6,200 kPa (MAC900). All forages were ground to pass through a 3.8 cm screen before incorporation into complete mixed diets (21:79 forage to concentrate ratio). Maceration did not affect (p ≥ 0.17) on site and extent of OM, N and ADF, and DE of sudangrass supplemented diets. Characteristics of ruminal digestion of OM, ADF, starch, as well as, microbial efficiency (microbial N, g kg -1 of OM fermentad) and protein efficiency (nonammonia N, g g -1 of N intake) were not different (p ≥ 0.11) for wheat straw versus sudangrass supplemented diets. However, total tract digestion of OM, ADF, N, and DE diet were greater (p ≤ 0.05) for sudangrass than for wheat straw supplemented diets. Using the replacement technique, DE value of SG averaged 9.59 MJ kg , very close to the expected value given its chemical composition. Mechanical maceration did not enhance the feeding value of sudangrass hay. Increase the intensity of maceration from 4,134 to 6,200 kPa did not altered ruminal or total tract digestion of OM, NDF or energy value of processed hay.