RESUMEN
Two trials were conducted to examine the influence of N enrichment of dried citrus pulp (DCP) through ammoniation vs urea supplementation on digestion and feeding value of a DCP-based diet for sheep. Treatments were 1) ammoniation of DCP with urea (CP-U), 2) ammoniation with ammonium hydroxide (CP-A), 3) supplementation with urea, and 4) supplementation with horse bean (HB). Diets were isonitrogenous (1.8% N). In Trial 1, treatment effects on characteristics of digestion were evaluated in a 4 x 4 Latin square experiment using four rams. Source of supplemental nonprotein N (NPN) did not influence (P > .10) ruminal OM digestion. Net microbial N synthesis, N absorption, N retention, and microbial efficiency were greater (P < .05) for the CP-U than for the CP-A or urea diets. Apparent N digestibility of CP-A was 14 to 25% lower (P < .05) than that of the other diets supplemented with NPN. In Trial 2, treatment effects on lamb growth performance were evaluated in a 105-d growing-finishing trial involving 32 Sardi lambs (19 kg). Intake was similar (P > .10) across treatments (1.13 kg of DM/d). Daily gain of the urea-fed lambs (182 g) was higher (P < .05) than that of CP-U- or CP-A-fed lambs (138 g). Feed efficiency and dietary NE values were similar (P > .10) among diets containing NPN. Growth performance seemed to be more directly affected by intake, rather than N economy. Enrichment of DCP through ammoniation with urea was a superior method of NPN supplementation with respect to efficiency of N utilization. However, the ultimate response to the potential benefits of such treatment may be seen only if N is truly limiting performance.
Asunto(s)
Alimentación Animal , Digestión , Nitrógeno/administración & dosificación , Ovinos/fisiología , Amoníaco/análisis , Animales , Citrus , Fibras de la Dieta , Ingestión de Alimentos , Ácidos Grasos Volátiles/análisis , Alimentos Fortificados , Concentración de Iones de Hidrógeno , Masculino , Nitrógeno/metabolismo , Rumen/química , Rumen/fisiología , Ovinos/crecimiento & desarrollo , Urea , Aumento de PesoRESUMEN
Effects of level and method of urea supplementation of N utilization and characteristics of digestion of a N-deficient (.85% N), citrus pulp-based diet were evaluated in a 4 x 4 Latin square design experiment, using four ruminally and intestinally cannulated crossbred (D'man x Sardi) rams. Two levels of urea (15.1 and 8.8 g/d, providing total N intakes of 12.0 and 9.1 g/d, respectively) and two methods of supplementation (urea mixed with the diet or continuously infused in the rumen) were compared in a 2 x 2 factorial arrangement of treatments. Ruminal pH varied between 6.2 and 7.0 across treatments and tended (P > .10) to be lower in animals receiving urea infusion. Ruminal ammonia concentrations were lower (P < .01) and more stable with urea infusion than with urea feeding. Ruminal VFA concentrations and profiles were unaffected (P > .10) by treatments. Site and extent of OM and fiber digestion were not influenced (P > .10) by either level of urea in the diet or method of supplementation. Average ruminal OM and ADF digestion were 53.1 and 64.5%, respectively. Total tract digestion values averaged 75.9 and 73.5%, respectively. With the exception of N efficiency (duodenal nonammonia N/total N intake) that was 31% lower (P < .10) for the high- than for the low-urea treatment, there were no treatment responses or interactions (P > .10) on characteristics of N utilization. Microbial N flow to the small intestine averaged (across treatments) 9.0 g/d and constituted 87% of the nonammonia N leaving the abomasum.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Fibras de la Dieta/metabolismo , Digestión , Ovinos/fisiología , Urea/administración & dosificación , Amoníaco/análisis , Alimentación Animal , Animales , Fibras de la Dieta/administración & dosificación , Ácidos Grasos Volátiles/análisis , Fermentación , Alimentos Fortificados , Concentración de Iones de Hidrógeno , Masculino , Nitrógeno/metabolismo , Rumen/química , Rumen/microbiología , Rumen/fisiología , Urea/metabolismo , Urea/farmacologíaRESUMEN
In rain-fed cereal-producing areas of Morocco, stubble and straw from barley and wheat and forage grazed from fallow lands are important feeds for sheep. Supplementation to maintain BW of ewes pregnant while grazing stubble, methods to improve utilization of straw, annual forage legumes to complement grazing of fallow land, and by-product feeds in diets for weaned lambs have been tested in collaborative research trials. Pregnant ewes grazing cereal stubble for 10 to 12 wk at a modest stocking rate and unsupplemented, or at a heavier stocking rate and supplemented after 5 wk, gained about 3 kg; most of the gain occurred in wk 1 to 4 due to intake of residual scattered grain. Following the stubble-grazing period (coincident with late gestation), straw plus an energy supplement alone resulted in low lamb birth weight and survivability. Urea treatment increased N content of straw and holds potential. After the onset of winter rains, self-reseeding annual legume (Medicago spp.) pastures allowed lactating Timahdit ewes to gain 4 kg during 90 d postpartum. Their suckling lambs gained 260 g/d, thus doubling the weight of lamb weaned per ewe compared with those grazing unimproved fallow. Confined growing lambs fed diets with 40% sugarbeet pulp or 20% carob meal gained more than 200 g/d, reducing the time needed to reach market weight. These results demonstrate that marked improvements in performance and efficiency of sheep in Mediterranean rain-fed cereal/livestock systems are possible using locally available resources.