Protein supplementation of formic acid‐ and enzyme‐treated silages. 1. Digestibilities, organic matter and fibre digestion

Abstract

Two silages were made from perennial ryegrass ensiled without wilting in 2-t capacity silos with the application of either formic acid or an enzyme mixture of cellulases and hemicellulases. Effluent losses were monitored over the ensiling period. Subsequent silage analysis showed that the enzyme-treated silage had higher concentrations of residual water soluble carbohydrate, lactic acid and acetic acid, and lower concentrations of cellulose, ADF and NDF. Effluent production was higher with the enzyme silage (formic acid, 211 1 t"'; enzyme, 267 It"'). The silages were either offered as the sole diet or supplemented with rapeseed meal at two levels (60 or 120 g fresh weight kg" ' silage DM offered) to growing steers equipped with rumen cannulae and T-piece duodenal cannulae. Apparent whole tract digestibilities for DM, OM, N, ADF and NDF were similar for all diets although nitrogen retention (g d"') was increased with supplementation of both silages (formic acid, 21-1; formic acid + 60 g, 23-5; formic acid+ 120 g, 28-5; enzyme, 22-6; enzyme + 60 g, 25-8; enzyme+120 g, 31-6). Rumen pH, ammonia and total volatile fatty acids patterns were similar. Supplementation increased the amount of organic matter apparently digested in the rumen (ADOMR) wilh formic acid-treated silage but not with Correspondence; A, B. McAllan, AFRC Instiiuie of Grassland and Environmenial Research, Hurley, Maidenhead, Bcikshire, SL6 5LR, UK. t Preseni address: Depar[men[ o( Agriculture, PO Box 1231, Bunbury 6230, Wesiern Australia.enzyme-treated silage. Liveweight gains were similar for both unsupplemented silages (0 49 kg d"'). These increased to 0-55 and 0-65 kg d"' for formic+ 60 and formic+120 respectively. Liveweight gains for the corresponding enzyme-treated supplemented diets were 0-81 and 0-91 kg d"' respectively. Liveweight gains on supplemented enzyme-treated diets were significantly (P<0-05) greater than those on formic acid-treated diets. ItitroductionPrevious work has shown that mixtures of cellulase and hemicellulase enzyme additives break down grass structural polysaccharides during ensilage (Henderson and McDonald, 1977; van Viiuren er al., 1989;Jacobs and McAllan, 1991). It was thought that this could give a silage of higher potential degradability in the rumen resulting in improved intake and animal performance. When enzyme-treated silages were fed alone to growing steers there were no indications of increased rumen digestion of fibre compared with untreated or formic acid-treated silages (Jacobs and McAllan, 1991). There were better liveweight gains and nitrogen retentions with enzymetreated silages but the differences were not significant. Enzyme additives have been found to make the carbohydrate fraction more readily available for rumen fermentation (van Vuuren el al., 1989) and it would seem likely that such silages would be better utilized with a protein supplement. McAllan and Smith (1983) and McAllan el al. (1988) observed that protein supplements can increase fibre digestion in the rumen with different responses fr...

Volatile fatty acid proportions and microbial protein synthesis in the rumen of cattle receiving grass silage ensiled with different rates of formic acid

“…In enzyme‐treated or inoculated silages, lactic acid fermentation has been found to be more extensive and, consequently, the proportion of rumen propionate has been observed to be over 200 mmol mol −1 (Jaakkola et al. , 1991; Jacobs and McAllan, 1992). A much higher acetic acid concentration was observed in the untreated silage than in the other silages.…”

“…With the FA 6 silage the proportion of butyrate was, however, lower than with the FA 4 silage, whereas at the same time an increase in the proportion of acetate was observed. Similarly, in some studies, restriction of silage fermentation and high residual WSC content in silage has increased the molar ratio of rumen acetate rather than butyrate (Jacobs and McAllan, 1992;Vanhatalo et al, 1992;Cushnahan et al, 1995).…”

“…As a result of the relatively small concentration of lactic acid in the FA 0 and FA 2 silages, the proportion of propionate in the rumen was only slightly higher than with restrictively fermented silages, FA 4 and FA 6 . In enzyme-treated or inoculated silages, lactic acid fermentation has been found to be more extensive and, consequently, the proportion of rumen propionate has been observed to be over 200 mmol mol )1 (Jaakkola et al, 1991;Jacobs and McAllan, 1992). A much higher acetic acid concentration was observed in the untreated silage than in the other silages.…”

Effects of lactic acid bacteria in inoculants on changes in amino acid composition during ensilage of sterile and non-sterile ryegrass

“…Analysis of dry matter (DM), pH and VFAs were carried out as described by Merry et al (1995). Total nitrogen was estimated by the Kjeldahl method as described by Jacobs and McAllan (1992). Soluble nitrogen was determined by incubating samples (0Á5 g) in simulated ruminant saliva buffer (15 ml) as described by McDougall (1948) (sodium bicarbonate, 81Á6 mmol l À1 ; disodium hydrogen orthophosphate, 47Á3 mmol l À1 ; potassium chloride, 4Á6 mmol l À1 , sodium chloride, 6Á1 mmol l À1 ; magnesium chloride, 0Á4 mmol l À1 ; calcium chloride, 0Á95 mmol l À1 ) for 2 h at 40 C. The nitrogen content of ®ltrates was determined by the Kjeldahl method.…”