Effects of a beta-adrenergic agonist (L-644,969) on performance and carcass traits of growing lambs in a cold environment

Abstract

. 2000. Effects of a beta-adrenergic agonist (L-644,969) on performance and carcass traits of growing lambs in a cold environment. Can. J. Anim. Sci. 80: 459-465. A 2 × 2 factorial experiment was conducted to study the effects of the beta-adrenergic agonist L-644,969 (BAA, supplied at 0.28 vs. 0 mg kg -0.75 d -1 ) on growth performance, carcass traits and nitrogen balance of lambs at two environmental temperatures (0°C vs. 20°C). Sixteen Suffolk-Cross wether lambs (30.2 ± 2.06 kg BW) were randomly divided into four groups and exposed to each of four experimental treatments (20°C with control diet; 20°C with BAA-supplemented diet; 0°C with control diet; and 0°C with BAA-supplemented diet) for 5 wk. The collection period for nitrogen balance was 4 d during the 4th week of treatment. The low temperature decreased efficiency of feed utilization and increased backfat thickness by 20.8% (P < 0.01) and 35.1% (P < 0.05), respectively. L-644,969, on the other hand, increased daily gain, feed efficiency and hot carcass weight by 22.5% (P < 0.05), 17.2% (P < 0.05) and 9.6% (P < 0.05,) respectively. Dressing percentage (P < 0.01), biceps femoris weight (P < 0.01) and rib eye area (P < 0.01) were also increased, but abdominal fat expressed as a percentage of liveweight (P < 0.05) was significantly decreased by BAA treatment. The improved weight gain, muscle weight and ribeye area in response to BAA, and in the absence of an increase in total nitrogen retention, indicate that the responses are due to nutrient repartitioning. Temperature did not impair the nutrient repartitioning effect of BAA, but feed efficiency may be more improved by BAA for the animals in the cold environment. . D'autre part, le β-agoniste augmentait le GMQ, la valorisation des aliments et le poids de carcasse chaude, soit respectivement de 22,5, 17,2 et 9,6 %, tous trois significativement au seuil de P < 0,05. Une augmentation (P < 0,01) était également observée pour le rendement de carcasse, le poids du biceps femoris et la surface de la noix de côte ainsi qu'une diminution (P < 0,05) de la graisse abdominale en pourcentage du poids vif. L'amélioration du gain de poids, du poids musculaire et de la surface de la noix de côte causé par le β-agoniste ainsi que l'absence de tout accroissement de la rétention de N total portent à conclure que ces effets sont dus à une modification de la répartition des nutriments, effet qui ne semble pas avoir été inhibé par la température d'ambiance. Par ailleurs, le gain d'efficacité alimentaire attribuable au BAA serait plus prononcé dans le milieu froid.Mots clés: Performances, caractères de carcasse, β-agoniste, température, agneaux Ruminant animals including cattle and sheep often grow more slowly and have reduced efficiency of feed utilization in winter. The reduced efficiency has been attributed to limited intake, low digestibility, high maintenance requirement and the change of composition of liveweight gain (Christopherson and Kennedy 1983;Delfino and Mathison 1991;Webster et al. 1997

Effects of raising lambs in a cold or a warm environment on animal performance and carcass traits

“…Quebec lamb production is very intensive with high ADG, producing lambs that are generally marketed before 5 mo of age. Therefore, the poor performance of lambs reported by Li et al (2000) and Moibi et al (2000) as well as the older age at slaughter in the latter study may not be relevant to current lamb production in Quebec. Schanbacher et al (1982) found better gains and feed efficiency and similar carcass composition with lambs raised at 5°C compared with lamb production at 18 or 31°C.…”

“…Raising lambs in such buildings may be economical since it has been estimated that in Quebec the cost of insulated and heated buildings is $42.32 m -2 more than uninsulated barns (Groupe Geagri 1998). Previous papers reported lower feed efficiency for 5-mo-old shorn lambs or lambs of unknown age (Li et al 2000) when raised at 0°C compared with 20 to 23°C. These lambs also produced more back fat at low ambient temperatures compared with lamb production at higher temperatures (Li et al 2000).…”

“…Previous papers reported lower feed efficiency for 5-mo-old shorn lambs or lambs of unknown age (Li et al 2000) when raised at 0°C compared with 20 to 23°C. These lambs also produced more back fat at low ambient temperatures compared with lamb production at higher temperatures (Li et al 2000). Quebec lamb production is very intensive with high ADG, producing lambs that are generally marketed before 5 mo of age.…”

“…Past studies evaluated lamb growth performance at fixed ambient air temperature; 0 or 23°C , 0 or 20°C (Li et al 2000);and 5, 18 or 31°C (Schanbacher et al 1982). The environmental conditions (temperature and humidity) for the present study were not kept constant, particularly in the cold environment, which closely represents field growth conditions experienced by lamb producers in Quebec, as well as other provinces of Canada and other countries such as Norway (Boe et al 1991).…”

Efecto del clorhidrato de zilpaterol sobre las características de la canal en cruzas terminales de corderos Kathadin

“…Este aumento en el rendimiento en canal coincide con los resultados de varios estudios en los que se empleó CZ (Vergara, (López et al, 2010;Romero, 2011) y básicamente se explica por la hipertrofia muscular originada por un aumento en la síntesis de proteína y una disminución en su degradación (Mersman, 1998;Beerman, 2002), lo que conduce a la reducción en el almacenamiento de grasa corporal (Yang y McElligott, 1989). No obstante esta explicación, se sabe que cada músculo responde de acuerdo con el tipo y la proporción de fibras que lo constituyen (Beerman, 2002), pues la ganancia es más evidente en las fibras tipo II y en las de tipo mixto oxidativo-glucolítico (Li et al, 2000).…”