Molasses level in lamb high-energy diets on productive performance, blood chemistry, liver minerals and histopathology

Abstract

The objective of this study was to determine the effect of increasing levels of molasses on growth performance, carcass characteristics, blood chemistry, liver minerals and histopathology of lambs. Twenty intact male pelibuey lambs with an average weight of 22.4±2.8kg were randomly assigned to one of the four experimental diets containing 0, 60, 120 and 180gmolasses/kg feed (as fed basis) in a completely random design. Lambs were individually confined to 1.5m2 pens. The experiment had a 15-day adaptation period and a 60-day experimental period. As molasses content in the ration increased from 0 to 180g/kg, S increased from 1.1 to 2.1g/kg DM, whereas Cu concentration ranged from 17.3 to 18.4mg/kgDM. All diets contained high concentrations of Fe (198–252mg/kgDM) and Zn (85–104mg/kgDM), and low Mo contents (1.4–1.5mg/kgDM). Molasses level had no effect (P>0.05) on DM intake, average daily gain, gain:feed, slaughter weight, full or empty gastrointestinal tract weight, digesta-free weight, hot and chilled carcass weights, dressing percent, longissimus muscle area, marbling, back-fat thickness, yield grade or KPH fat. Most of the lamb carcasses of this study were graded with small to slight marbling. The clinical status of the lambs was evaluated through histological and blood chemistry tests, obtaining samples on days 0, 15, 30 and 60. Although most blood parameters were within normal ranges, blood urea nitrogen, creatinine and cholesterol concentrations decreased (linear; P<0.05) as molasses increased in the diet. Concentrations of the enzymes serum glutamic oxaloacetic transaminase, alkaline phosphatase and creatine phosphokinase were also reduced (linear; P<0.05). Concomitant reductions (P<0.01) in liver Zn and Mo concentrations were also noticed. Although no differences (P>0.05) were observed in liver histopathological observations between treatments, Cu-related sub-lethal hepatic damage was evident in all animals, in absence of clinical signs. Special stain showed fine grained Cu deposits within hepatocytes in three cases belonging to different treatments. It appears that lambs consuming the control diet without molasses with a low S content (0.11%) were as susceptible to a pre-hemolytic copper poisoning (Pre-HCP) as those consuming the other diets containing higher Cu concentrations.