Comportamento ingestivo, desempenho, características de carcaça e componentes não-carcaça de cordeiros Morada Nova alimentados com diferentes níveis de energia metabólizavel

Abstract

The objective of this study was to evaluate the ingestive behavior, average daily weight gain (ADG), feed conversion (FC), feed efficiency (FE), carcass characteristics, commercial cuts weights and yield, weight of gastrointestinal content and compartments, weight and yield of internal organs of Morada Nova growing lambs fed different levels of metabolizable energy (ME). 32 lambs, non-castrated, with average initial body weight of 12.12 ± 1.69 kg and approximately 60 days of age were used. Animals were distributed into four experimental treatments determined by different levels of metabolizable energy (1.28, 1.72, 2.18 and 2.62 Mcal/kg DM), in a randomized block design with eight replicates per treatment. Tifton 85 hay was used as roughage. Lambs were slaughtered sequentially as the group of animals of each treatment reached an average of 25 kg of body weight. Increasing linear effect was observed of metabolizable energy levels (P<0.05) over dry matter (DM) intake and decreasing linear effect for neutral detergent fiber (NDF) intake, both expressed in g/day, %BW e g/kg0,75. Eating, ruminating and total chewing times, expressed in h/day, decreased linearly (P<0.05) with increasing levels of energy in the rations. Idle time, in turn, increased linearly (P<0.05). Eating and rumination efficiencies were influenced by the energy levels (P<0.05) expressed in g DM/h. The number of ruminal boluses, number of chews and chews per ruminal bolus were not affected by the levels of ME. However, time spent chewing per ruminal bolus was influenced (P<0.05). Increased linear effect (P<0.05) was observed for ADG, without affecting, however FC and FE. Carcass traits such as: empty body weight, hot carcass weight and yield, cold carcass weight and yield, loss by cooling and biological yield were not affected (P>0.05) by the increasing levels of dietary energy. Increased linear effect (P<0.05) was also observed for ribeye area and decreased linear effect (P<0.05) for loss by fasting with the increasing of ME levels. The levels of energy also decreased (P<0.05) the weight of the cuts shoulder and leg (%), and increased linearly the neck (kg), rib, breast and flank expressed in kg and%. There was no effect of energy levels (P>0.05) on weight of gastrointestinal content. Increased linear effect (P<0.05) was observed for the weights of heart, the group of organs lungs, trachea, esophagus and tongue (PTEL), liver and spleen, expressed in kg. Regarding the compartments of the gastrointestinal tract, it was observed increased linear effect (P<0.05) only for rumen-reticulum, in %, and small intestine, in kg. The perirenal, omental and mesenteric fats were also influenced by the energy levels (P<0.05) with linear increase when expressed in kg and %. It was concluded that the increase of ME levels of diets influences the ingestive behavior, promote increases in ADG and ribeye area, and reduction in loss by fasting. Regarding the weights of cuts, levels of ME reduce shoulder and leg and increase neck, rib, chest and flank. Levels of ME also influence positively weight and yield of internal organs, viscera and fats of Morada Nova lambs during the growing period.