Rumen dry matter and crude protein degradability of extracted or untreated oilseeds and Leucaena leucocephala leaves

Abstract

A study was undertaken to determine the rumen DM and CP degradability characteristics of soyabean, canola seed, peanut, palm kernel and Leucaena leucocephala leaves. The oilseeds were either treated with n‐hexane to extract the fat or left untreated. Nylon bags were incubated in each of four rumen cannulated sheep for 0, 2,4, 6,12, 24 and 48 h. Animals were fed on a diet consisting of meadow hay (ad libitum) and 150 g of concentrate twice daily. Fat extraction caused a decrease (P ≤ 0.05) in DM disappearance of soyabean at 0, 2,4, 6 and 12 h and of peanuts at all incubation times. CP disappearance from peanuts was reduced (P ≤ 0.05) as a result of fat extraction at 0, 2, 4, 6 and 12 h. Fat extraction of canola seed increased CP disappearance at 0, 2, 4, 6 and 24 h (P ≤ 0.05). However, in the case of defatted canola seed, an increase in DM disappearance (P ≤ 0.05) was observed in the first 4 incubation times and a decrease (P ≤ 0.05) in the later times. Fat extraction increased (P ≤ 0.05) DM disappearance of palm kernel at 0 and 48 h, but reduced it at 4, 6 and 24 h. CP disappearance of palm kernel was improved by treatment (P ≤ 0.05) at 0, 4, 24 and 48 h and decreased at 12 h. In the case of palm kernel the largest differences in DM and CP disappearance occurred between the 24 and 48 h incubation times. Degradability characteristics for DM and CP of full‐fat soyabean, canola seed and peanut were comparable to those of the full fat samples. Effective DM degradability of soyabean, canola seed and peanuts was 72.2 and 71.9; 74.1 and 66.8; and 85.9 and 70.8 for full fat and extracted feeds, respectively. Effective CP degradability was similar in all oilseeds with the exception of the extracted canola seed. Therefore, the incorporation of full‐fat soyabean, canola seed and peanut into ruminant rations can be considered as a means of increasing the energy balance. Both palm kernel DM and CP degradabilities were characterized by slow rates of degradation by negative values "b”;. This suggests the predominance of microbial colonization over disappearance during incubation. DM and CP disappearance of Leucaena leucocephala leaves originating from Cuba were lower than those from Nigeria. Degradability characteristics for CP and DM of Cuban leucaena leaves showed that the linear model resulted in a better fit than the exponential one.