Resumen

GALINA, M.A. et al. Productive response in steers fed corn silage, or lactic silage enriched with a ruminal fermentation improver. Arch. zootec. [online]. 2009, vol.58, n.223, pp.383-393. ISSN 1885-4494.

A feeding trial was carried out with 120 steers (296 ± 6.9 kg) crosses of Zebu during 120 days divided in three treatments. Treatment 1: 40 animals fed corn silage (EN). Treatment 2: n= 40 fed silage enriched a lactic probiotic enriched with a NPN source (EP). Treatment 3 (EPS): 40 steers fed EP plus a slow intake nitrogen supplement (SNLC). Three steers fixed with rumen cannula were used to study ruminal kinetics and in vivo digestibility. Ruminal NH₃ was significant lower in EN (15 mg/ 100 ml) than EP and EPS (18 and 22 mg/100 ml respectively). The degradability of NDF, measured in situ, was 28% in EN, 38% in EP and 48% in EPS (p<0.05). Dry matter apparent digestibility was significantly lower in EN (57%) compared with 68% in EP and 70 % in EPS. The voluntary intake was lower (p<0.05) in EN (90 g/kg^0.75/d) compared with 120 and 140 g/kg^0.75/d in EP and EPS respectively. An increase was observed in N intake from 72 g/d (EN) to 218 g/d (EP) and 277 g/ d in EPS. N digestibility increased from 73% in EN to 76% in EP and EPS. Lactobacilli counts were 1.6 millions/ml in EN, 10.5 in EP and 12.5 million/ml in EPS. Purines derivatives excretion increased in both diets with probiotic (p<0.05). Daily body weight gain differed (p<0,05) in the three diets (0.874 kg/d in EN, 1.172 in EP and 1.250 in EPS). The offer of silage with probiotic with or without the slow intake nitrogen supplement increased the body weight gain in feedlot steers, improving ruminal fermentation and increasing microbial protein.

Palabras clave : Non-protein N; In vivo digestibility; Rumen physiology.

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