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

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^?1; enzyme, 2671 t^?1). The silages were either offered as the sole diet or supplemented with rapeseed meal at two levels (60 or 120 g fresh weight kg^?1 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^?1) 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) with formic acid-treated silage but not with enzyme-treated silage. Liveweight gains were similar for both unsupplemented silages (0·49 kg d^?1). These increased to 0·55 and 0·65 kg d^?1 for formic + 60 and formic + 120 respectively. Liveweight gains for the corresponding enzyme-treated supplemented diets were 0·81 and 0·91 kg d^?1 respectively. Liveweight gains on supplemented enzyme-treated diets were significantly (P < 0·05) greater than those on formic acid-treated diets.     

The digestion by cattle of grass silages made with no additive or with the application of formic acid or formic acid and formaldehyde

The aim of the experiment was to assess the effect of applying, at commercially recommended rates, formic acid or formic acid/formaldehyde at ensilage upon the subsequent digestion of the silages by cattle. Three wilted grass silages were made from perennial ryegrass ensiled at a DM concentration of 206 g kg⁻¹ after a poor wilting period of 49 h without additive application and with application of 2.5 litres t⁻¹ of formic acid or of 4.5 litres t⁻¹ of a mixture of (gkg⁻¹) 500 formic acid, 200 sulphuric acid and 200 formatin giving an application rate of 15 g formaldehyde kg⁻¹ herbage crude protein (N × 6.25).
The silages were fed to cattle equipped with rumen cannulae and duodenal re-entrant cannulae. Results from analyses of silage composition and from the digestion of organic matter and N showed no major differences between silages. The efficiency of rumen microbial N synthesis, the rumen degradability of silage N (determined in vivo or in sacco ) and in vivo digestion of individual amino acids were also unaffected by additive treatment. These results indicate that poor wilting conditions before ensilage restricted the effectiveness of additive treatment; the ineffectiveness of formaldehyde in reducing the rumen degradability of silage N may also have been related to the low rate of formaldehyde application.     

Cell wall degrading enzymes for silage. 2. Aerobic stability of enzyme-treated laboratory silages

The effects of two commercial cellulase/hemicellulase enzymes derived from Trichoderma reesei on silage fermentation and aerobic stability were investigated in three laboratory-scale experiments. In Experiment 1, perennial ryegrass ( Lolium perenne ) was treated with enzyme A at the rates of 0. 0·125, 0·250, 0·500 and 0·750 cm³ kg^-1. In Experiment 2, Italian ryegrass ( Lolium multiflorum ) was treated with the same enzyme at the rates of 0, 0·250 and 0·500 cm³ kg^-1 and with 85% formic acid (3·5 cm³ kg^-1). In Experiment 3, perennial ryegrass was ensiled untreated, with enzyme A (0·250 and 0·500 cm³ kg^-1) and with 0·200 and 0·400 cm³ kg^-1 enzyme B which also contained glucose oxidase. All silages were well preserved. Aerobic deterioration was related to numbers of lactate assimilating yeasts. In Experiment 1, all silages were stable over a 4-day period. In Experiment 2, enzyme A treatment delayed the temperature rise compared with the untreated control ( P <0·05), whereas the formic acid-treated silage was stable. In Experiment 3, the temperature rise in the silage treated with the higher level of enzyme B occurred one day later than in the other silages ( P <0·05).     

The effects of different protein supplements on the utilization of untreated, formic acid-treated or enzyme-treated silages by growing steers

Three grass silages were made from perennial ryegrass ensiled without additive application (U) or with the application of formic acid (F) or an enzyme mixture of hemicellulases and cellulases (E).
Analysis of silages showed that both untreated and enzyme-treated silages had higher lactic acid concentrations than formic acid-treated silage. Enzyme-treated silage had lower levels of ADF and NDF but higher concentrations of residual WSC than other silages.
The silages were fed to growing steers supplemented with either rapeseed meal (RSM) (60 g kg⁻¹ silage DM) or fishmeal (FM) at a level isonitrogenous with RSM diets, so providing six diets (UR, UF, ER, EF, FR, FF). Organic matter intakes were similar, but ADF intakes were significantly ( P < 0·001) lower with enzyme-treated silage diets (UR, 1163; UF, 1160; ER, 1104; EF, 1035; FR, 1216; FF, 1213), as were intakes of NDF ( P < 0·01) (UR, 1946; UF, 1955; ER, 1877; 1772; FR, 2031; FF, 2041). Apparent whole tract digestibilities of organic matter were significantly ( P < 0·001) higher with enzyme-treated silages (UR, 0·644, UF, 0·644; ER, 0·668; EF, 0·678; FR, 0·633; FF, 0·633). Liveweight gains were generally higher with treated silage diets and RSM supported a greater response than FM (UR, 0·496; UF, 0·498; ER, 0·567; EF, 0·489; FR, 0·543; FF, 0·506) with both enzyme and formic acid-treated silages, although none of these differences were significant.     

The digestion of grass silages produced using inoculants of lactic acid bacteria

The purpose of this study was to evaluate the efficiency of two inoculants of lactic acid bacteria (LAB) on grass silages. The evaluation was made in terms of silage composition, rumen fermentation, digestion and animal production. Over a 2-year period two lots of silage were prepared in two 100-tonne capacity clamps. In each case an untreated silage and an inoculant-treated silage were prepared simultaneously from an identical herbage source using independent sets of silage-making equipment. The inoculant used in the first year was Pioneer Brand 1188 (Pioneer Hi-Bred UK), and in the second year a slightly different inoculant from the same source (Pioneer Hi-Bred) was used. The two inoculants were essentially similar in composition, comprising a mixture of Lactobacillus plantarum and Streptococcus faecalis ; the strains included in the second inoculant were selected for their capacity to tolerate higher temperatures. The fermentation of the inoculant-treated silages appeared to be dominated by homofermentative LAB compared with the untreated silages. The use of either inoculant was associated with a change in the rumen volatile fatty acid (VFA) pattern, with a significantly greater molar proportion of propionate and a corresponding reduction in both acetate and butyrate. There was a trend indicating an enhanced efficiency of microbial protein synthesis within the rumen of the heifers for the inoculant-treated silages, although this was only significant when concentrate was offered with the silage in one experiment. The inoculant-treated silages had significantly greater intake characteristics than did the untreated silages, though this was not reflected in a statistically significant improvement in average daily liveweight gain in either year.     

The effect of urea on the voluntary intake by calves of silages preserved with formaldehyde and formic acid

Perennial ryegrass cv. S23 was preserved by fermentation (C), or with the addition of 8.7 1 formalin (35% w/w formaldehyde) per t fresh herbage (F) or of 9.0 1 equal mixture (by vol.) of formalin and formic acid (85% w/w solution) per t fresh herbage (FF). These three silages comprised the treatments in a three-period, crossover design in which urea (u) was given at the rate of 20 g per kg dietary DM to half the animals. Twelve calves were allocated to the treatment sequences when they were approximately 12 weeks of age from within groups which had previously received diets with or without urea. Calves ate significantly (P< 0.001) less of silages F or FF than of silage C when each was offered alone, but when urea was given, intakes of silages F and FF were significantly (P < 0.001) increased such that the intakes of all three silages with urea were similar (23.6, 19.6, 19.3, 24.2, 24.2, 24.7 ± 0.51 g DM per kg LW for C, F, FF, Cu, Fu and FFu, respectively). Significantly (P<0.01) more of the DM in silage C was digested than in F or FF and the addition of urea significantly (P<0.05) increased the digestibility of DM from silage FF only (73.8, 71.3, 69.8, 74.6, 70.7, 72.5 ± 0.72% for C, F, FF, Cu, Fu and FFu, respectively). When the silages were given alone, calves spent longer eating and ruminating per kg DM ingested with F or FF than with C. The time spent on F and FF was significantly (P<0.01) reduced by the addition of urea (303, 388, 411, 297, 299, 290 ± 18.9 min per kg DM ingested for C, F, FF, Cu and Fu and FFu, respectively). The results presented suggest that urea partially alleviated the reduction in voluntary intake by calves given herbage preserved using formalin, but the mode of action was not clear.     

The effects of cereal supplementation of grass and maize silages

Grass and maize silages were fed alone and with two levels of a barley supplement to Friesian steers of about 300 kg liveweight. The organic matter (OM) intakes of grass and maize silage were similar although the OM digestibilities of the silages were 0·722 and 0·649 respectively. For both silages, barley supplementation increased total OM intake and total digestible OM intake by 0·46·0·08 and 0·37·0·06 g per g OM of supplement respectively. Liveweight gains on grass and maize silage diets were 1·38 and 1·20 kg d^-1 respectively, but the differences were not significant (P> 0·05).     

Proteolysis and amino acid degradation during ensilage of untreated or formic acid-treated lucerne and maize

Lucerne ( Medicago sativa ), field wilted to 330 g dry matter (DM) kg⁻¹, and whole-plant maize ( Zea mays ), 383 g DM kg⁻¹, were treated with formic acid (FA) at the rate of 4-5 1 t⁻¹ fresh forage. The effects of FA treatment on proteolysis and amino acid degradation was investigated at several intervals over a 90-d period of ensilage in laboratory silos. Formic acid treatment produced different patterns of pH decline during ensilage of the two forages, suggesting some degree of crop specificity in response to FA treatment. After 7 d of ensilage of lucerne there were increases of 81% in nonprotein nitrogen (NPN), and 104% in free amino acid nitrogen (FAA-N), but with FA-treated lucerne the increases were 39% and 31%, respectively. FA treatment resulted in a reduction in the concentration of most free amino acids in lucerne silage, with the exception of glutamic acid and serine; the branched chain amino acids as well as glycine, tyrosine and proline were significantly (P<0·05) reduced after 3 d of ensilage. By contrast, FA treatment of maize did not significantly ( p <0·05) affect the NPN content nor was there a consistent pattern in the changes in FAA-N. Formic acid treatment of maize did produce a significant reduction ( P <0·05) in the concentration of most individual free amino acids at 90 d of ensilage. Overall, FA treatment had a more predictable effect on proteolysis and amino acid degradation in ensiled lucerne than in ensiled whole-plant maize.     

Protein and amino acid composition ofFagopyrum (buckwheat)

Seven varieties of buckwheat, two Indian selections (F. esculentum, F. tetaricum) and five from Poland (Czernoplodna, Hruszowska, Jubilejna, Emka and Iskra) were cultivated under North Indian conditions and analysed for their protein and amino acid composition. The present studies revealed that European selections can also be successfully cultivated in India. Buckwheat is a good source of lysine, and some other essential amino acids.     

Effect of formic acid and a bacterial inoculant on the amino acid composition of grass silage and on animal performance

An Italian ryegrass and hybrid ryegrass sward was harvested on 11 May 1994. The mean dry‐matter (DM) content of the herbage was 197 g kg^–1 fresh matter (FM), and mean nitrogen and water‐soluble carbohydrate contents were 20 and 272 g kg^–1 DM respectively. Approximately 72% of total nitrogen (TN) was in the form of protein‐nitrogen. The herbage was treated with either no additive, formic acid (3·3 l t^–1) (Add‐F, BP) or inoculant (2·3 l t^–1) (Live‐system, Genus) and ensiled in 100 t silos. Changes in effluent composition with time showed that silage fermentation and protein breakdown were delayed by treatment with formic acid. Formic acid and inoculant treatments also inhibited amino acid catabolism during ensilage. All silages were well fermented at opening with pH values < 4·0 and ammonia‐N concentrations of ≤ 50 g kg^–1 TN after 120 d ensilage. Treatment had an effect on protein breakdown as measured by free amino acid concentration, with values of 21·5, 18·2 and 13·2 mol kg^–1 N at opening (191 d) for untreated, formic acid‐treated and inoculated silages respectively. Amino acid catabolism occurred to the greatest extent in untreated silages with significant decreases in glutamic acid, lysine and arginine, and increases in gamma amino butyric acid and ornithine. The silages were offered ad libitum without concentrate supplementation to thirty‐six Charolais beef steers for a period of 69 d (mean live weight 401 kg). Silage dry‐matter intakes and liveweight gains were significantly (P < 0·05) higher on the treated silages. Silage dry‐matter intakes were 7·42, 8·41 and 8·23 kg d^–1 (s.e.d. 0·27) with liveweight gains of 0·66, 0·94 and 0·89 kg d^–1 (s.e.d. 0·058) for untreated, formic acid‐treated and inoculated silage‐fed cattle respectively. In conclusion, additives increased the intake of silage and liveweight gain by the beef steers, and it is suggested that this may be caused in part by the amino acid balance in these silages.     

Protein and amino acid composition of some wild leguminous seeds

The seeds of five different species ofAcacia, twoAlbizzia, twoErythrina and two species ofMucuna were analysed for their protein and amino acid composition. Some of these seeds are comparable to a popular food legume,Cicer arietinum, in protein and amino acid composition.     

Comparison of the fermentation quality and nutritive value of sulphuric and formic acid-treated silages fed to beef cattle

Five experiments were carried out in the years 1980-1983 and 1986 to study the effect of treating grass at ensiling with sulphuric acid (850 g kg^?1) and formic acid (850 g kg^?1) additives alone, and in mixtures with or without formalin on the preservation of grass, in vivo digestibility in sheep, in-silo loss, intake and performance of finishing cattle. Primary growth grass was ensiled in experiments 1 (3–4 June 1980), 2 (12-15 June 1981) and 3 (31 May-2 June 1982), primary regrowth grass in experiment 4 (1-2 August 1983) and secondary regrowth grass in experiment 5 (7-10 October 1986). During the ensiling period within each experiment, approximately 60 t of unwilted, double-chopped, additive-treated or untreated grass was packed into covered concrete-walled 60-t capacity silos. The dry matter (DM) contents of the ensiled grass in experiments 1, 2 and 5 ranged from 155-180 g kg^?1 and were lower than those recorded in experiments 3 and 4 (214 g kg^?1). With the exception of grass ensiled in experiment 2, where water-soluble carbohydrate (WSC) contents were low, at 104 g kg^?1 DM, grass in all other experiments contained relatively high WSC contents ranging from 140-154 g kg^?1 DM. In experiments 1, 3 and 4 all silages were well-preserved. However, in experiment 2 the 450 g kg^?1 sulphuric acid-treated and formic acid-treated silages displayed significantly lower pH, buffering capacity (Bc) and ammonia nitrogen contents than the untreated silage. In experiment 5, the sulphuric acid-treated and formic acid-treated silages displayed significantly lower pH, Bc, ammonia nitrogen, butyrate and volatile fatty acid (VFA) contents than the untreated silage. Each of the silages was offered daily with various levels of a supplementary concentrate for approximately 70-d periods to twelve animals of mixed breed in experiments 1, 3, 4 and 5 and to fifteen animals in experiment 2. All animals weighed between 380-470 kg at the start of the experiments. In experiments 1, 2 and 3 there were no significant differences between silages for any of the intake or animal performance parameters. In experiment 4, cattle fed the formic acid-treated silage displayed significantly higher silage DM intakes and daily liveweight gains than those fed the sulphuric acid-treated and untreated silages; in experiment 5, cattle fed the formic acid-treated silage displayed significantly higher silage DM intakes than those fed the untreated silage. It was concluded that formic acid was a more effective silage additive than sulphuric acid. Increasing the level of supplementation significantly decreased silage DM intakes in cattle in experiments 3 and 4, and significantly increased daily liveweight gains and daily carcass in cattle in experiments 1, 3 and 4.     

Protein content and amino acid profile of some wild leguminous seeds

Seeds of 28 wild growing legumes of India were analysed for their protein content and amino acid compositions. A wide variation was observed in protein contents (18.3 to 50.9%). The amino acid composition and protein content of some of these seeds were in close proximity to that of soybean; however, some legumes registered a higher level of certain amino acids and protein as compared to the latter.     

The chemical composition and nutritive value of grass silages prepared with no additive or with the application of additives containing either Lactobacillus plantarum or formic acid

A mixture of perennial and hybrid ryegrasses(234 g DM kg^-1) was forage harvested and ensiled after a 24-h wilt in good ensiling conditions in 2-t capacity silos with no additive application (control) or with the application of either Lactobacillus plantarum , 4 × 10⁶ (g fresh weight of grass)^-1, or of 31 formic acid t^-1. Sufficient 2-kg capacity laboratory silos were also filled with grass to monitor the changes in chemical composition of the ensiled grass with time. In laboratory silos, inoculation with L. plantarum resulted in a more rapid fall in silage pH ( p < 0.001) and a more rapid production of lactic acid ( P < 0.001) than in the control silage. At the end of the storage period (laboratory silos, 80 d; 2-t silos, 200-300 d), the inoculated silos had lower pH ( p ammonia-N (g kg N¹) and acetic acid contents ( p < 0.01) and higher water soluble carbohydrate (WSC), lactic acid (P<00.1) and ethanol ( p < 0.05) contents than the control silage. The formic acid-treated silage had significantly lower contents of ammonia-N (g kg N^-1, p < 0.05), acetic and tactic acids (p<0.01) and higher contents of WSC and ethanol ( p < 0.01) than the control silage. When fed to wether sheep, the digestibilities of DM, organic matter and gross energy were not altered by additive treatment. The digestibility of modified acid-detergent fibre was lower for both the inoculated ( P < 0.01) and formic acid-treated silages ( p < 0.05). However, N retention was improved ( p < 0.05) by both additive treatments. Silage intake was improved ( p < 0.01) by additive treatment from 53.4 (control) to 58.0 (inoculated) and 60.4 (formic acid) g DM (kg live weight^0.75)^-1d^-1.     

The effect of cell wall degrading enzymes or formic acid on fermentation quality and on digestion of grass silage by cattle

A first cut of timothy, treated with water (untreated), formic acid (FA), cellulase + lactic acid bacteria (CB), cellulase + hemicellulase (CH) or cellulase + hemicellulase + a lignin-modifying enzyme (CHL), was ensiled in pilot-scale silos. Silages, except CB, were fed to four male cattle, each equipped with a rumen and duodenal cannula, in a digestibility trial designed as a 4 × 4 Latin square. The animals were fed a diet of 400 g of concentrate and 600 g of silage at a level of 70 g DM kg^?1 live weight (LW^0·75). All enzyme-treated silages were well-preserved with a more extensive fermentation than in FA silage. The quality of untreated silage was poorer as indicated by higher pH and ammonia-N content. The amount of effluent from enzyme-treated silages ranged from 116 to 127 g kg^?1; for FA and untreated silages values were 101 g kg^?1 and 80 g kg^?1, respectively. Total DM losses from enzyme-treated silages were higher than from FA silage (P < 0·05). No significant differences were noticed between silages in the apparent digestibility of organic matter (OM), neutral-detergent fibre (NDF), acid-detergent fibre (ADF) or nitrogen (N). The apparent digestibility of cellulose was higher with enzyme-treated silages than with FA silage (P < 0·05). The values for microbial N flow at the duodenum were 80·0, 91·9, 80·7 and 70·5g N d^?1, and for the efficiency of rumen microbial N synthesis 38·6, 47·6, 36·9 and 32·5 g N kg^?1 OM apparently digested in the rumen for untreated, FA, CH and CHL silages, respectively. In the rumen the molar proportion of propionate was higher (P < 0·01) and that of butyrate lower (P < 0·01) with enzyme-treated silages when compared with FA silage. The proportion of butyrate was also lower with untreated than with other silages (P < 0·01). The rumen residence time of NDF and ADF was longer (P < 0·05) with enzyme-treated silages than with FA silage.     

Effects of feeding clover silages on feed intake, milk production and digestion in dairy cows

Silages were made from pure crops of perennial ryegrass, red clover and white clover over 2 years. In all but one case the silage was stored as bales. A silage additive specially adapted for bales (Kofasil Ultra^TM) was used for all silages and they were all of good hygienic quality. The additive contained sodium nitrite, hexamethylene, tetraamine sodium bensoate and sodium propionate. The silages were offered ad libitum, either pure or mixed [grass/clover 0·50/0·50 on a dry‐matter (DM) basis] with a fixed amount (8 kg) of concentrate. Two experiments, one in each year, were performed with high‐yielding multiparous dairy cows in mid‐lactation, and both rumen‐cannulated and intact cows were used. The experiments were carried out using an incomplete changeover design with fifteen cows and five treatments each year. The cows consumed large quantities of these silages (12·7–16·3 kg DM per cow per day). The highest intakes were obtained when the red clover and the 0·50 red clover:0·50 perennial ryegrass silage diets were offered. However, there was a difference between years. In year 1, 0·50 red clover:0·50 perennial ryegrass and 0·50 white clover:0·50 perennial ryegrass silage diets showed the highest intakes while pure perennial ryegrass and white clover silage diets gave lower intakes. In year 2 the highest intake of silage was obtained when the diet containing silage from red clover from a second cut was offered, while the silage from red clover from a first cut gave the lowest intake. The voluntary intakes of silages from white clover and perennial ryegrass were intermediate. No cases of bloat or other digestive disturbances were observed. Milk yield was significantly lower for the perennial ryegrass silage diet compared with all other diets in year 1. In year 2 milk yield was highest for the white clover silage diets and lowest for the red clover silage diets from both cuts. In year 1 there were relatively small differences in milk composition while in year 2 milk fat content was significantly lower with white clover silage diet and milk protein content was significantly higher with the perennial ryegrass diet. The overall conclusion from these experiments was that cows were able to consume large quantities of pure legume silage without serious disturbance to their metabolism. Differences in measurements of rumen metabolism were found between diets and especially between years. Milk production differences appears to be coupled to both differences in rumen physical characteristics, such as passage rate and particle size as well as differences in volatile fatty acid production in the rumen.     

In vitro amino acid digestibility of food proteins as measured by the digestion cell technique

The digestibility of proteins and individual amino acids of nineteen selected foods was determined by anin vitro assay. Samples were hydrolysed with pepsin for 30 minutes in an acidic medium; the pH was then raised to 7.5 and the mixture poured into the dialysis bag (molecular weight cut-off 1000) of a digestion cell with pancreatin. Digestion products, mixtures of free amino acids and low molecular weight peptides which pass through the dialysis membrane, were collected for 6 hours by sodium phosphate buffer circulation. All proteins from animal sources displayed a digestibility similar to casein, except for breakfast sausage. Vegetable proteins showed intermediate digestibility, except for cereals (lower) or peanut butter (higher). Target amino acids of enzymes were generally more readily hydrolysed. However, compared to other animal proteins, glycine in milk products, valine, isoleucine, methionine and lysine in breakfast sausage and hot dog, and histidine in tuna were more easily released. Overheating of non-fat dried milk not only reduced the lysine digestibility, but also that of methionine, phenylalanine, histidine and cystine. Among vegetable proteins, wheat products were characterized by a relatively greater release of threonine, isoleucine and histidine, and peas by a lower digestibility of methionine and lysine. Proline of soy isolate and isoleucine of pinto bean were resistant to hydrolysis while arginine of pinto beans and of rice-wheat-gluten was easily released.     

Effect of amino acid supplementation on protein quality of soy-based infant formulas fed to rats

The powder forms of soy-based infant formulas obtained from four manufacturers were fed to weanling rats for two weeks, as the sole source of protein in diets containing 8% protein, 20% fat, and adequate amounts of minerals and vitamins. The relative protein efficiency ratio (RPER) and the relative net protein ratio (RNPR) values (casein + methionine=100) of diets containing unsupplemented formulas were 71–81 and 78–85, respectively. Supplementation of the formula diets with lysine (0.2%), methionine (0.2%), threonine (0.1%) or tryptophan (0.05%) increased the level of the supplemental amino acid in rat serum but generally failed to improve the RPER or RNPR values. Addition of all four essential amino acids to the formula diets, however, caused a marked improvement in their protein quality (RPER or RNPR values=100). The data suggested that proteins in soy-based formulas could be marginally co-limiting in several indispensable amino acids.Presented in part at the 202nd annual meeting of the American Chemical Society, New York City, 25–30 August 1991.     

The rate of addition of formic acid to grass at ensilage and the subsequent digestion of the silage in the rumen and intestines of sheep

The main object of the experiment was to assess the effect of the relative proportion of non-protein nitrogen (NPN) to total nitrogen in silage on digestion in the sheep. Four unwilted perennial ryegrass silages were made with the addition of formic acid at 0, 2·2, 4·2 and 5·2 litres t^-1 to provide foods with NPN proportions reducing from 0·26 to 0·20 of the total N. The digestion of the silages was studied in a 4 × 4 Latin Square experiment with sheep cannulated in the rumen, proximal duodenum and terminal ileum.
Results for organic matter (OM), cellulose and N showed no major difference between silages in their digestion in the rumen, small intestine and caecum and colon, though small differences ( P <0·25) in rumen fermentation pattern and in the proportion of digestible OM disappearing in the small intestine were observed. Concentrations of ammonia N in the rumen and rates of rumen bacterial protein synthesis did not differ significantly between silages and there were no treatment effects on the passage of individual amino acids to the small intestine. The results indicate that the proportions of NPN to total N in the silages examined had little influence on the efficiency of silage N utilization in the rumen or on the passage of undegraded dietary protein to the small intestine.