| Summary: | Twenty-eight beef-type animals were divided into four groups and fed four rations consisting of equal amounts of basal ration, to which increments of alder sawdust (Alnus rubra) were added (0, 13%, 21%, and 35%) (Experiment I). The addition of the sawdust had no significant effect on total gain although the three groups of animals receiving sawdust in their diet had a higher rate of gain than the group receiving no sawdust. The effects of the ration on the carcass grade and the acceptability (tenderness and juiciness) of the meat as studied by a trained taste panel, were non-significant.
When the rations used in the above trial were subjected
to a digestion trial using mature wethers, the results coincided with the growth data collected from the steers used above. If the digestion of the basal rations were taken as constant, the wood material had a digestion coefficient ranging from 46.5% to 13.5%, depending on the level of sawdust
in the diet. It was felt that a figure of 13% digestion for sawdust was close to being correct, and that the variation in measurement of the digestion of sawdust was due to the increased utilization of the basal ration when the sawdust was present.
Analysis of the rumen fluid of the steers in the growth trial for total and individual volatile fatty acids (VFA) showed a decrease (p<.05) in the molar percent of propionic acid as the level of wood in the diet increased, while the total concentration of VFA and the molar percent acetic acid remained relatively constant.
Thirty-six yearling Hereford steers, assigned to six treatments consisting of a basal ration and three roughage sources (hay (H), alder sawdust (W), and extruded alder sawdust
(E)), fed at two levels (15% and 20%), were used in a study to determine the effect of heat and pressure treatment of wood on the utilization. The growth of the animals on the H rations was significantly (p< .01) greater than those on the other treatments. The effect of treating the sawdust by extruding it was non-significant although the animals on the extruded wood diet had a slight increase in gain over those on the W ration. The effect of level of roughage was nonsignificant.
The effects of level of protein in the diet and the interaction with roughage source were studied. Protein levels of 13% and 15% were studied, along with two roughage sources (hay (H), and alder sawdust (W)), fed at two levels (15% and 20%). The H rations again had a significantly (p<.01) greater gain. The effect of increasing the protein level in the diet was found to be non-significant.
When the above rations were subjected to analysis using the in vitro technique, results showed that the H rations had a significantly (p < .01) higher digestion than either the W or E rations. It was also found that the E rations had a higher digestion coefficient than the W rations (p <«05). Increasing the roughage level from 15% to 20% caused a significant (p<.01) decrease in digestion.
When the same rations were subjected to an in vivo digestion study using growing wethers, the results were similar to the in vitro study with the H rations having a greater digestion (p <.01) than the W or E rations. However the difference between the W and E rations was non-significant.
An equation for predicting the in vivo dry matter digestion is given: In vivo dry matter digestion = 60.1252 + 0.0221 (in vitro dry matter digestion) + 0.4799 (acid detergent fibre) - 3.5855 (lignin) - 0.8395 (cellulose). === Land and Food Systems, Faculty of === Graduate
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