Effects of Combining Feed Grade Urea and a Slow-release Urea Product on Performance, Dietary Energetics and Carcass Characteristics of Feedlot Lambs Fed Finishing Diets with Different Starch to Acid Detergent Fiber Ratios

Abstract

Recent findings have shown that microbial nitrogen flow and digestible energy of diets are increased when urea is combined with a slow-release urea (SRU) in diets with a starch to acid detergent fibre ratio (S:F) 4:1. This affect is attributable to enhanced synchrony between ruminal N availability for microbial growth and carbohydrate degradation. To verify the magnitude of this effects on lamb performance, an experiment was conducted to evaluate the effects of combining urea and a SRU in diets containing S:F ratios of 3:1, 4:1, or 5:1 on performance, dietary energetics and carcass characteristics of finishing lambs. For that, 40 Pelibuey×Katahdin lambs (36.65±3 kg) were assigned to one of five weight groupings in 20 pens (5 repetition/treatments). The S:F ratio in the diet was manipulated by partially replacing the corn grain and dried distiller’s grain with solubles by forage (wheat straw) and soybean meal to reach S:F ratios of 3:1, 4:1 or 5:1. An additional treatment of 4:1 S:F ratio with 0.8% urea as the sole source of non-protein nitrogen was used as a reference for comparing the effect of urea combination vs. conventional urea at the same S:F ratio. There were no treatment effects on dry matter intake (DMI). Compared the urea combination vs urea at the same S:F ratio, urea combination increased (p<0.01) average daily gain (ADG, 18.3%), gain for feed (G:F, 9.5%), and apparent energy retention per unit DMI (8.2%). Irrespective of the S:F ratio, the urea combination improved the observed-to-expected dietary ratio and apparent retention per unit DMI was maximal (quadratic effect, p≤0.03) at an S:F ratio of 4:1, while the conventional urea treatment did not modify the observed-to-expected net energy ratio nor the apparent retention per unit DMI at 4:1 S:F ratio. Urea combination group tended (3.8%, p = 0.08) to have heavier carcasses with no effects on the rest of carcass characteristics. As S:F ratio increased, ADG, G:F, dietary net energy, carcass weight, dressing percentage and longissimus thoracis (LM) area increased linearly (p≤0.02). Combining urea and a slow-release urea product results in positive effects on growth performance and dietary energetics, but the best responses are apparently observed when there is a certain proportion (S:F ratio = 4:1) of starch to acid detergent fibre in the diet.

Effects of Duration of Calcium Propionate Supplementation in Lambs Finished with Supplemental Zilpaterol Hydrochloride: Productive Performance, Carcass Characteristics, and Meat Quality

“…The consistent response of increased LMA, HCW, CCW, and D% through ZH supplementation has been well established in finishing lambs within the feedlot setting [2,11,27]. The increase in LMA is mainly due to the greater ADG [35] and the growth in shoulder muscle [Partida et al, 2015]. The increase in D% by 3.9% with CaPr, observed by day 28 when combined with ZH, resulted in 2.2 kg more salable meat compared to ZH due to CaPr supplementation.…”

Comparative evaluation of supplemental zilpaterol hydrochloride sources on growth performance, dietary energetics and carcass characteristics of finishing lambs

“…Increased HCW, LM area, and dressing percentage, and reduced backfat thickness with ZH supplementation has been a consistent response in feedlot lambs [18,21]. Increased LM area is partially explained by the greater ADG [22], whereas the increased dressing percentage is expected due to greater carcass protein accretion with no change in digestive tract fill [6,23]. The increased LM area is also consistent with increased shoulder muscle [21].…”

Efecto de la inclusión de zeolita (clinoptilolita) en ovinos en etapa de finalización: Respuesta productiva y energética de la dieta

“…Ganancias diarias (rango de 0,230 a 0,291 kg/d), consumos de MS (rango de 0,230 a 0,291 kg/d) y eficiencias (rango de 0,180 a 0,210) similares a lo observado para el grupo control en este experimento se han informado para machos enteros cruzados de las razas Katahdin × Pelibuey consumiendo dietas de finalización libres de zeolita o de algún otro tipo de aditivo y con un contenido energético de 1,90 a 2,10 Mcal/kg de EN para mantenimiento (López-Carlos et al, 2011;Ríos et al, 2010Ríos et al, , 2014Estrada et al, 2013Estrada et al, , 2016. Por otra parte, la información sobre la respuesta productiva de borregos consumiendo dietas de finalización suplementadas con zeolitas es escasa.…”