Digestibilidade e características ruminais de dietas com diferentes níveis de concentrado para bubalinos e bovinos Digestibility and ruminal metabolism on bubalines and bovines fed diets with different concentrate levels

Avaliaram-se a influência do fornecimento de 23, 43 e 63% de concentrado em dietas com milho moído e resíduo desidratado de mandioca como fonte de amido sobre o consumo, os coeficientes de digestibilidade total e parcial dos nutrientes, a concentração de amônia, o pH ruminal e a eficiência microbiana. Utilizaram-se três bovinos holandeses (Bos taurus) e três búfalos Murrah (Bubalus bubalis) com 473±54 kg e 400±33 kg de peso corporal (PC), respectivamente, canulados no rúmen e duodeno. Os fluxos duodenais e fecais foram estimados utilizando-se óxido crômico. O delineamento experimental utilizado foi com dois quadrados latinos 3 x 3 e arranjo fatorial 3 x 2. A ingestão média de MS foi inferior nos bubalinos (1,40% do PC) em comparação aos bovinos (1,63% do PC). As ingestões máximas de PB (10,09 g/kg PC0,75 nos bovinos e 8,36 g/kg PC0,75 nos bubalinos) foram obtidas com 44,4% de concentrado e as de amido (32,83 g/kg PC0,75 para os bovinos e 28,38 g/kg PC0,75 para os búfalos), com 61,7% de concentrado. Os coeficientes de digestibiliade total e as digestibilidades ruminal (DR) e intestinal (DI) dos nutrientes, à exceção do amido e da PB, não diferiram entre os tratamentos e as espécies utilizadas. O maior coeficiente de digestibilidade total (95,7 vs 85,8%) e ruminal (87,4 vs 81,9%) do amido foram observados nos bovinos. A digestibilidade ruminal do amido aumentou linearmente com os níveis de concentrado. A menor digestibilidade ruminal (13,2 vs 27,5%) e a maior digestibilidade intestinal da PB (86,8 vs 72,5%) foram observadas nos bovinos. O pH ruminal nos bubalinos (6,7) foi superior ao dos bovinos (6,3). Nos búfalos, a concentração de amônia ruminal diferiu com os níveis de concentrado, o que não ocorreu com os bovinos. A eficiência microbiana, no entanto, não diferiu entre as espécies e os níveis de concentrado.<br>The objective of this trial was to evaluate three different concentrate levels (CL) (23, 43 and 63%) on intake, nutrient digestibility, ruminal metabolism, and microbial efficiency in Holstein bovines and Murrah buffaloes (Bubalus bubalis) fed diets containing ground corn and dry cassava by-product as energy sources. Three Holstein bovines and three Murrah buffaloes averaging, respectively, 473±54 kg and 400±33 kg of body weight (BW), fitted with ruminal and duodenal cannulas were blocked by species and randomly assigned to two replicated 3 x 3 Latin squares with a factorial arrangement of treatments. Chromium oxide was used as duodenal and fecal flow marker. Intake of dry matter (DM) was lower on bubalines (1.40% of BW) than on bovines (1.63% of BW). The greatest CP intake was of 10.09 g/kg BW0.75 for bovines and 8.63 g/kg BW0.75 for bubalines with 44.4% of concentrate in the diet while the highest starch intake was of 32.83 g/kg BW0.75 for bovines and 28.38 g/kg BW0.75 for bubalines with 61.69% of concentrate in the diet. There were no effects of CL and species on total tract digestibility, ruminal digestibility, and intestinal digestibility of nutrients with the exception of starch and CP. Apparent total tract digestibility of starch was greatest on bovines (95.7 vs. 85.8%); ruminal starch digestibility was also greatest on bovines (87.4% vs. 81.9%) and that increased linearly when the CL was increased in the diet. It was observed lower ruminal digestibility (13.2 vs. 27.5%) and higher intestinal digestibility (86.8 vs. 72.5%) of CP on bovines compared to bubalines in this trial. Ruminal pH averaged 6.7 on bubalines and was greater that than on bovines (6.3). Ruminal ammonia concentration differed across treatments on bubalines but not on bovines whereas microbial efficiency was not affected either by dietary CL or by species.