Terminação de ovinos em pastos de Brachiaria spp. suplementados com níveis de amireia em substituição ao farelo de soja

Abstract

The aim was to evaluate the effect of replacing soybean meal with extruded urea (Amireia® 200S) at increasing levels (0; 6; 12; 18 and 24 g 100 kg-1 of live weight (LW) in the supplementation of beef lambs) finished on Brachiaria spp. pastures, on the structural and nutritive characteristics of the forage; nutritional value of the supplement; dry matter intake (DMI); ingestive behavior; performance; parasitological aspects and their interactions in the host-pasture-soil components; carcass, non-carcass components and meat quality. Sixty Texel crossbred lambs, with an initial weight of 20.7±0.87 kg and 2.5±0.7 months of age, were evaluated. 6 animals of each treatment were used, and for the slaughter and evaluations of carcass and derivatives, 9 animals were used per treatment. For the variables, forage mass, forage accumulation rate and structural characteristics of the pasture there was no treatment effect o (P>0.05). The forage DMI in percentage of LW and metabolic weight were adjusted to the quadratic equation, in which it was estimated that the minimum DMI in relation to LW (1.5%) and by the metabolic weight (55.6 g MS/kg^0,75) would be found at levels 10 and 8.3 g 100 kg-1 LW of extruded urea, respectively. Animals that received 18 g 100 kg-1 LW had the highest average daily gain. Grazing time showed a decreasing linear effect, supplement consumption increasing linear effect, as well as the biting rate as a function of the levels. Animals from treatments 6 and 18 g 100 kg-1 LW spent more time ruminating. The search for water was higher for animals that received the highest level of replacement, and lower for animals treated with 18 g 100 kg-1 LW. Extruded urea levels of up to 18 g 100 kg-1 LW maintained animal performance even when both groups had egg counts per gram of faeces above 1200, with no apparent impairment of metabolic status or welfare. There was less dispersion of gastrointestinal nematode larvae in the environment (pasture and soil) when increasing the level of replacement of soybean meal by extruded urea; and clayey soil did not prove to be a good reservoir for gastrointestinal nematode larvae. A significant effect (P<0.05) of extruded urea levels was observed in lamb supplementation for slaughter weight; body condition score at slaughter; empty body weight; hot carcass weight; finishing; loin eye area and subcutaneous fat thickness. For non-carcass components in general, no effect of diet was observed (P>0.05). As for the quality of the meat, the variables, pH; exudation loss; cooking loss; L*, a* and b* on muscle and fat 24 hours post-slaughter there was no significant effect (P>0.05) of the supplement. In the chemical composition of the meat, there was an interaction between level x sex for ether extract and crude protein, the meat of the females of the treatment without extruded urea had a higher content of ether extract and the meat of the males of the treatments with 12 g and 24 g 100 kg-1 LW higher crude protein contents. The replacement of soybean meal with extruded urea in the diet of beef sheep can be provided up to the level of 18 g 100 kg-1 LW, without negatively compromising consumption and ingestive behavior, animal performance, most carcass characteristics, components non-carcass, meat quality and chemical composition; assists in the resilience of hosts to gastrointestinal nematodes and without causing ammonia intoxication or any visible disturbance.