Respuesta productiva de vacas lecheras alimentadas en raciones completas isoenergeticas e isonitrogenadas pero de diferente degrabilidad ruminal de su proteina.
1994
Figallo S Roberto Maria
A trial was run to evaluate the response of high producing dairy cows, to diets differing in the rumen degradability of the intake protein. A randomized block design was used, in which 24 cows were allocated into three treatments, starting on day 30 and ending on day 120 postpartum. Treatments consisted in giving isoenergetic and isonitrogenous diets with either 74, 66,6 or 58% of their protein degradable in rumen: high, medium and low degradable protein respectively (NRC, 1989). A number of variables were evaluated, like daily milk production, milk composition (total solids, non fat solids, fat and protein), somatic cells, feed intake, weight change, body condition and a plasma biochemical profile. In addition, the kinetics of rumen degradation of N compounds was studied for the different ingredients used in the diets, through to the "in situ" incubation technique of Meherz and Orskov (1977). The results were analyzed by covariance. Milk production did not differ among treatments (P > 0,05) being 29.69, 30.62 and 30.55 1/day for high, medium and low degradable protein, respectively. Treatments did not affect milk components, exempt for protein, which was higher (P <0,05) for treatments of medium and low degradability. Somatic cell count was higher (P <= 0,01) when a low degradability diet was given. No differences were found for feed intake, weight change, body condition nor plasma biochemical profile (p > 0,05). Kinetics of rumen degradation gave values of 75.8, 72.2 and 61.8% for the diets of high, medium and low degradability respectively. It is concluded that different degradabilities in diets for cows producing about 30 l/day do not induce differences in productivity exempt some modifications in milk protein percentage. It is recommended that, when low degradability protein feeds are utilized, their digestibility in the lower tract be studied in addition to their degradability in rumen.
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