Utilización de subproductos agroindustriales en raciones completamente mezcladas para vacas lecheras

Abstract

La utilización de subproductos agroindustriales (SA) en la alimentación de vacas lecheras está cobrando cada día más importancia, debido a una creciente industrialización en origen que genera una gran diversidad de alimentos. El objetivo del trabajo fue comparar dos raciones completamente mezcladas (RCM) isoenergéticas, isoproteicas e isofibrosas, una basada en SA (T1) y otra basada en ensilaje de planta entera de maíz (T2). Para cumplir con este objetivo se realizaron tres ensayos, el ensayo I con vacas lecheras, el ensayo II con vacas lecheras fistuladas en el rumen y el ensayo III con fermentadores de doble flujo continuo.

Agro-industrial by-products (AB) utilization in the diet of dairy cows is each day gaining more importance, due to a growing industrialization in origin that generates a great diversity of food. The objective was to compare two total mixed ration (TMR) isoenergetic, isoproteic and isofibrous, one based on AB (T1) and another based on whole plant maize silage (T2). To comply with this objective three trials were carried out: trial I with dairy cows, trial II with dairy cows fistulated in the rumen and trial III with dual continuous flow fermenters. In the first one 26 multiparous cows were used, in a completely randomized design (CRD). The chemical composition of T1 and T2 was: 55.5 and 65.3% DM; 66.1 and 67.3% of dry matter digestibility; 17.1 and 16.5% raw protein; 39.2 and 40.0% of neutral detergent fibre (NDF); 2.40 and 2.43 Mcal/kg DM of metabolizable energy, respectively. Dry matter and metabolizable energy consumption, milk production and composition, cow weight variation, and somatotrophine, somatomedin, insulin, non esterified fatty acids, and glucose concentrations did not show any significant variations (P>0.05). Blood urea nitrogen was greater for AB (P<0.05). In the trial II, 4 cows fistulated in a crossover design received T1 and T2 treatments. Ruminal environment, NDF digestion kinetics and passage rate were evaluated. Ruminal environment (pH, N-NH3 and VFA) did not show any significant variations (P>0.05). To evaluate ruminal digestion kinetics, NDF barley rootlets and whole plant maize silage were incubated in the rumen. The parameters that showed significant variations (P<0.05) were soluble fraction, potential degradation and lag time, the percentages being greater for NDF whole plant maize silage. Degradable fraction did not show any significant variations (P>0.05). Hourly Degradation rate and NDF effective degradation in the hour 36 and 48 showed a tendency (P=0.10) to be greater for barley rootlets. As regards TMR passage rate, 6 cows were fistulated in a CRD, for both treatments a pulse in the rumen of whole plant maize silage fiber marked with chromium was used. The parameters were reckoned with the kinetic digestion in ruminants computer program. Rumen retention time, caecum and colon refilling time, and the average total retention time did not show any significant differences (P>0.05). In trial III, 4 dual continuous flow fermenters were used, which received T1 and T2 treatment in a cross over design. Ruminal in vitro environment and apparent digestibility of RCM chemical components were evaluated. They did not show any significant variations (P>0.05). The use of agro-industrial by-products in TMR allows keeping a TMR productive level that includes whole plant maize silage.