The effect of harvesting system on nutrient losses during silage making. 1. Field losses

An experiment was carried out during 1982 in which the effects of three differing harvesting systems on the field losses occurring during the conservation of grass as silage were examined. The treatments were either (a) harvesting herbage directly by means of a flail harvester (unwilted flail, UF), or (b) pre-cu ing of herbage with a rotary drum mower and lifting using a precision-chop forage harvester with wilting (WP) and without wilting (UP). Herbage was harvested on 26 May, 21 July and 7 September 1982. The mean yields of herbage produced from plots harvested by the three systems were not significantly different, with dry ma er (DM) yields of 12470, 12300 and 12230 kg ha^-1 for the UF, UP and WP treatments respectively. However, field losses with the UP and WP treatments were greater than with the UF treatment (P<0·01). As a result the yields of herbage ensiled with the UP and WP treatments, 11690 and 11320 kg DM ha^-1 respectively, were significantly lower than with the UF treatment, 12710 kg DM ha^-1 (P <0·05). Wilting of first cut herbage for a period of 72 h resulted in a significant reduction (P<0·05) in digestible organic ma er (DOM) concentration (determined in vitro), whereas small increases in DOM concentration were observed following wilting of second and third harvest material.
It is concluded that, even under favourable weather conditions, both pre-cutting and wilting of herbage prior to harvesting can result in considerable losses of nutrients in the field.     

A comparison of unwilted and wilted grass silages offered to beef cattle without and with monensin sodium

A randomized block experiment was conducted to compare unwilted and wilted grass silages and the effects of the feed additive monensin sodium on the silage intake and performance of finishing beef cattle. Two regrowths from a predominantly perennial ryegrass (cv. S24) sward were ensiled either without wilting or after field wilting for 3 d (dry matter (DM) concentrations 161 and 266 g kg⁻¹ respectively). Both silages were treated with formic acid (2·6 and 30 litre t⁻¹ respectively) and were well preserved. The silages were offered ad libitum to forty-eight Charolais-cross cattle (thirty-two steers and sixteen heifers, mean initial live weight 351 kg) for 145 d. All animals received 2·2 kg concentrates per head daily and half of those on each silage treatment received in addition 200 mg monensin sodium per head daily. Silage DM intake was 5.04, 504. 5·48, 5·63 ± 0.134 kg d^−l; fasted liveweight gain was 0·69, 0·77. 0·64 and 0·73 ± 0.033 kg d^−l and carcass gain was 0·47, 0·50, 0·40 and 0·45 ± 0·020 kg d⁻¹ for the unwilted silage without and with monensin and the wilted silage without and with monensin respectively. It is concluded that wilting grass of low DM concentration for 3 d prior to ensiling reduced the performance of finishing beef cattle below that obtained from well-preserved unwilted silage in spite of a higher DM intake being achieved with the wilted silage. The inclusion of monensin sodium in a silage-based diet increased performance without significantly affecting feed intake.     

The effects of incorporating sugar-beet pulp with herbage at ensiling on silage fermentation, effluent output and in-silo losses

Three studies were undertaken with the aim of examining in-silo losses associated with ensiling mixtures of beet pulp and herbage. In Experiment 1, first-regrowth perennial ryegrass was ensiled untreated or mixed with either 40 or 120 kg unmolassed beet pulp t^?1 fresh grass prior to ensiling. In each of Experiments 2 and 3, second-regrowth ryegrass was ensiled untreated or mixed with either 40, 80 or 120 kg unmolassed beet pulp t^?1 fresh grass prior to ensiling. Dry-matter concentrations of herbage ensiled in Experiments 1, 2 and 3 were 141, 157 and 139 g kg^?1 respectively. Time-course studies indicated a more rapid fermentation with the untreated silages. Ensiling beet pulp with herbage resulted in significant improvements in silage fermentation, reflected in reductions in silage pH and ammonia nitrogen concentrations, with these effects being pronounced at beet pulp inclusion in excess of 80kg t^?1. Beet pulp inclusion increased the dry-matter concentrations of the resulting silages while reducing crude protein, modified acid detergent fibre and gross energy concentrations. In Experiment 1 beet pulp retained 1·62 and 1·641 effluent kg^?1 at the 40 and 120kg t^?1 application rates respectively. In Experiments 2 and 3, effluent retentions were 1·40, 1·29 and 0·93 1 kg^?1 and 2·87, 2·19 and 1·781 kg^?1 at the 40, 80 and 120kg t^?1 beet pulp inclusion rates respectively. In each of Experiments 1 and 3, in-silo losses were reduced with increasing level of beet pulp inclusion, while in Experiment 2 in-silo losses were relatively unaffected by treatment. Nutrient losses in effluent were reduced by the inclusion of beet pulp in all three experiments, while nutrient losses in surface waste and invisible nutrient losses tended to increase with higher levels of beet pulp inclusion. It is concluded that the inclusion of beet pulp with herbage at ensiling can result in an improved silage fermentation and a reduction in in-silo losses, while at the same time retaining considerable quantities of effluent within the silo. However, with herbage dry-matter concentrations below 160gkg^?1, beet pulp inclusion in excess of 120 kg t^?1 herbage would be required to eliminate effluent production totally.     

Grass silage as a basic feed for store lambs. 1. Effect of wilting, chop length and stage of maturity of grass silage on intake and performance of store lambs

Two experiments were carried out with grass silages cut at a leafy (Experiment 1) and a more mature (Experiment 2) stage of growth to evaluate the effect of wilting and chop length on silage intake and performance of store lambs. In each experiment, the herbage was cut with a rotary mower and was either ensiled within 24 h as unwilled silage (U) or wilted for 1–3 d (W). Each silage type was harvested with either a double-chop harvester (D) or a precision-chop harvester (P). All silages were treated with formic acid at 3 1 t^?1 and were well preserved. The silages were fed ad libitum to Suffolk crossbred store lambs (twenty-four lambs per treatment) without any supplement over a period of 8 or 9 weeks. Wilting of the silages had little effect on silage intake (797 vs. 809g dry matter (DM) d^?1) or on lamb performance in Experiment 1. In Experiment 2, wilting of the D silage increased silage DM intake (589 vs. 534 g DM d^?1; +10%) and reduced the extent of liveweight losses. Wilting of the P silage reduced silage intake (770 vs. 791g DM d^?1; -3%) and reduced liveweight gains. In Experiment 1 intakes of the D silages were 650–667g DM d^?1 and just maintained lamb live weights. Intakes of the P silages were 39–49% higher than the D silages (927–968 g DM d^?1) and increased liveweight gains. In Experiment 2 intakes of the D silages were 534–589 g DM d^?1 and resulted in a loss in lamb live weight. Precision-chopping increased silage intakes by 31–48% (770–791 DM d^?1)in Experiment 2 and improved lamb liveweight gains. Lamb performance was higher on the UP silage than on the WP silage. The rumen retention lime (RRT), estimated from the rumen contents of the lambs at slaughter and their silage intake before slaughter, was much shorter for the lambs fed on the P silages (12.6–20.6 h) than those fed on the D silages (21.4–29.3 h) in each experiment. Silage intake and liveweight gain were positively related to silage in vivo DM digestibility (DMD), whereas RRT was negatively related to DMD. However, there were distinct differences between the P and D silages in the elevation and, to a lesser extent, in the slope of the regression lines, indicating that intake of D silage was limited by factors other than the digestibility of the silage The results of this study show that the chop length of grass silage had a far greater effect on intake and on lamb performance than silage digestibility, whereas wilting had little or no effect.     

The effect of system of silage harvesting and feeding on milk production

Two silages were produced by harvesting grass either unwilted, using a direct cutting flail forage harvester (flail-direct), or wilted following precut-ting and being picked up using a meter-chop harvester (precision-wilted). Formic acid was applied at the rates of 2·45 and 2·9 1 t^-1 for the flail-direct and precision-wilted silages, respectively. Weather conditions were difficult, both before and during harvesting with a total of 27 mm rainfall falling on the wilted herbage before ensiling. The in-silo dry matter losses were 199 and 68 g kg^-1 for the flail-direct and precision-wilted silages, respectively. The resulting silages had mean particle lengths of 49 and 24 mm, dry matter contents of 186 and 276 g kg-^-1 and D-values of 068 and 062 for the flail-direct and precision-wilted silages, respectively. During a 141-day feeding period commencing on 19 November, the two silages were offered to 88 British Friesian cows with a mean calving date of 21 January and divided into four groups in a 2×2 factorial design experiment. The silos were divided longitudinally and two groups of cows were self-fed the silages in situ, one for each silage type, while the other two groups were easy-fed the same silages along a feed fence. There were no significant interactions between system of silage harvesting and feeding on any of the measurements of animal performance. Animals on the flail-direct silage consumed 16% less silage dry matter and produced 10% more milk per cow than those on the precision-wilted silage treatment. The overall effect was a 12% greater milk output for each unit of grass dry matter ensiled with the flail-direct than with the precision-wilted harvesting system. System of silage feeding did not significantly influence silage intake or milk output, with the mean milk yields during the final 21 days of the study being 234 and 236 kg d^-1 (±0.30) for the self- and easy-feed systems, respectively. The effects of the treatments on milk composition, liveweight change, body condition score and total ration digestibility are also reported.     

Factors influencing the response in intake of silage and animal performance after wilting of grass before ensiling: a review

This review examines the response in intake of silage and animal performance after wilting of grass before ensiling. It uses data from eighty‐five published comparisons. Initial analysis identified those variables having the greatest influence on the increase in dry‐matter (DM) intake of grass silage owing to wilting. Total water loss, drying rate of the wilted material and ammonia‐N concentration of the unwilted material were the variables most closely and positively correlated to the proportional increase in DM intake as a result of wilting, with r² values of 0·344, 0·393 and 0·240 respectively. There was little evidence of curvilinearity in any of the relationships. Stepwise regression analysis was used to identify the best multiple linear regressions for predicting the proportional increase in intake owing to wilting. Factors associated with the extent and rate of water loss in the field (total water loss and drying rate) and the quality of the unwilted material ensiled and its subsequent fermentation pattern (DM digestibility, crude protein, ammonia‐N content of unwilted silage) were the key variables in the relationship. Subsequent analysis related the increase in output of milk energy of dairy cows and liveweight gain of beef cattle to the same independent variables. This indicated that variables shown to describe the response in DM intake in the previous analysis were among those most closely related to the increases in animal performance owing to wilting of grass. To assess whether the increase in animal performance owing to wilting could be explained as a direct response to increased metabolizable energy (ME) intake of wilted compared with unwilted silages, linear relationships were derived between the increase in milk and beef production parameters and the increase in ME intake owing to wilting. From these, it was concluded that there was no clear evidence that wilting reduced the efficiency of utilization of ME in beef or dairy cattle. The present study showed that the increase in milk energy output (measured in MJ) per increase in ME intake (measured in MJ) owing to wilting was linear, with a slope of 0·19. This response from additional ME intake owing to wilting is in line with what would be anticipated when increasing ME intake by other methods.     

The effect of addition of sugar and inoculation with two commercial inoculants on the fermentation of lucerne silage in laboratory silos

Lucerne (DM 236 g kg^-1, WSC 49 g (kg DM)^-1) was ensiled in test-tube silos with or without either glucose or fructose and with or without one of two commercial inoculants. The WSC content of the forage as ensiled was too low to obtain a well preserved untreated silage. By day 4 the pH values of the silages with added sugar or inoculant were significantly lower (P< 0·001) than the control silage. A satisfactory fermentation was attained only in the silages to which sugar and an inoculant had been added. These silages had a lower pH, more protein-N (P< 0·001), less ammonia-N (P<0·001), a faster increase in counts of lactic acid bacteria, and decrease in counts of coliforms than the other silages. Homo-fermentative lactic acid bacteria dominated the fermentation in the inoculated silages while leuconostocs dominated the early stages of fermentation in the control silages. The results indicate that if there is insufficient sugar in the original crop, then the bacteria in an inoculant will not be able to produce enough lactic acid to lower the pH to an acceptable level. This has important implications for the ensilage of lucerne and other highly buffered low sugar crops.     

Silage and milk production: comparisons between unwilted and wilted grass silages made with different additives

Four grass silages, all made in mid-July from second-harvest perennial ryegrass swards, were compared in a 16-week feeding experiment with twelve Ayrshire cows. Two silages were unwilted and two wilted. All the silages received formic acid ('Add-F') at the rate of 3 litres t^-1 either with formalin at the rate of 1 litre t^-1 or without formalin. The unwilted and wilted silages had mean dry matter (DM) concentrations of 200 and 243 g kg^-1, and in vitro D-values of 0·293 and 0·272 respectively. The silages were offered ad libitum plus 6 kg concentrates per cow per day. The daily intakes of unwilted and wilted silage DM were 10·2 and 9·2 kg per cow respectively on the formic acid treatment, and 10·2 and 9·2 kg on the formic acid + formalin treatment. The mean daily milk yield on the unwilted silage treatments was 19·2 kg per cow which was significantly higher than the yield of 17·2 kg per cow on the wilted silage treatments. The formalin had no significant effect on milk yield. The four silage treatments had small and non-significant effects on milk composition. It is concluded that the unwilted silages, which had excellent fermentation characteristics, were superior to the wilted silages as a feed for dairy cows.     

THE RELATIONSHIP BETWEEN THE DM CONTENT OF HERBAGE FOR SILAGE MAKING AND EFFLUENT PRODUCTION

A study of 16 silages made at the Hannah Research Institute and 22 silages made at the Grassland Research Institute showed highly significant positive relationships hetween the DM percentages of the material ensiled and the resultant silage. Using regression equations derived from this data, and from a record of the presence or absence of effluent, it was calculated that the average minimum DM content of herbage for ensiling which would produce no effluent was 22.9%. To ensure a margin of safety against production of effluent, a minimum DM content of 24.7% in the herbage was calculated from the confidence limits. To obtain this DM content, herhage will normally require wilting; effluent production should then be negligible.     

Influence of bacterial inoculant and substrate addition to lucerne ensiled at different dry matter contents

Field-wilted lucerne was chopped with a forage harvester at 33 ± 1·5, 43 ± 2·0 and 54 ± 1·8% dry matter, treated and ensiled in laboratory silos during four cuttings in each of two years. Treatments were control (C), sugar addition at 2% of fresh weight (S), inoculum applied at 3 × 10⁵ bacteria g⁻¹ herbage (I), and sugar and inoculum combined (IS). Duplicate silos were opened and analysed after 1, 2, 3, (4 or 5), 7, 14 and 60 d of fermentation. The initial rate of proteolysis of lucerne protein decreased with increasing dry matter (DM) content of the lucerne, and was not influenced by the year, cutting or silage treatment. Inoculation increased ( P <0·05) the rate of pH decline for all silage dry matters, and shortened the lag time prior to pH decline with 33 and 43% dry matter silages. Sugar addition had no effect on rate of pH decline or lag time. Inoculation and sugar addition both lowered final pH, acetic acid, ammonia (NH₃), free amino acids (FAA) and soluble non-protein N (NPN) in silages ( P <0·01) and increased lactic acid content with 33 and 43% dry matter silages. Only inoculation was beneficial at 54% DM with no difference between I and IS. The influence of forage characteristics (epiphytic lactic acid bacteria, buffer capacity and sugar:buffer capacity ratio) on treatment effectiveness varied with dry matter content.     

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.     

Effluent production from grass silages treated with additives and made in large-scale bunker silos

Data from twenty experiments, conducted at ADAS Research Centres in England and Wales during 1986–92, were used to determine effluent production from additive-treated grass silages made in large-scale bunker silos. The additives compared were formic acid at 4·0 l t^–1, rolled barley at 44·0 kg t^–1, dried molassed sugar beet feed at 40·0 kg t^–1 and liquid inoculants at 2·2 l t^–1 together with a non-additive-treated control. The silages were made from herbage with an average dry-matter (DM) content of 177 (s.e. 3·8) g kg^–1 and water-soluble carbohydrate content of 140 g kg^–1 DM. Average silage toluene DM content was 213 (s.e. 3·8) g kg^–1. The formic acid and sugar beet feed silages were both well fermented, whereas the other silages were less well fermented. Effluent produced was determined as either effluent production (l t^–1 grass ensiled) during the 52-d period in which it was measured or peak flow (l h^–1) during the first 2 d of ensilage. Compared with non-additive-treated silage, dried molassed sugar beet feed significantly reduced both effluent production (27%) and peak flow (36%). Formic acid significantly increased peak flow (51%), but had little effect upon effluent production, and significantly reduced effluent N and lactic acid content. Barley and inoculant treatment had no significant effect upon effluent production. In general, poor relationships were found between DM content and effluent production. Nevertheless for silages, except those treated with absorbents or formic acid, a significant (P < 0·001) negative relationship between silage effluent production (l t^–1 grass ensiled) and the DM (g kg^–1) content of the ensiled grass was found.     

The effects of degree of chopping grass for silage and method of concentrate allocation on the performance of dairy cows

Three silages were produced from the same swards by harvesting grass using either a double-chop harvester (DC) or a precision-chop harvester adjusted to produce a long staple length (PL) or a short staple length (PS). The mean particle lengths were 47, 52 and 14 mm respectively.
Of each material 250 t was ensiled unwilted and with formic acid additive at the mean rate of 2-4 litres t^-1 of grass. All three silages were well preserved and degree of chopping had no effect on fermentation as indicated by either pH, ammonia N or organic acid concentration.
The silages were offered ad libitum to seventy-two British Friesian cows with a mean calving date of 28 January which were in their second or later lactation, in a randomized-block experiment from day 8 of lactation until 12 April. In addition twelve animals on each silage received a uniform daily concentrate allowance of 7·2 kg while twelve were offered concentrates according to their individual milk yields but with a mean concentrate allowance over the twelve cows of 7·2 kg d^-1. Degree of chopping had no significant effect on either silage dry matter intake or milk yield with mean intakes during the final 21 d of the experimental period of 9·2, 9·2 and 9·2 kg d^-1 and mean milk yields of 25·2, 25·2 and 25·2 kg d^-1 for the DC, PL and PS silages respectively. Method of concentrate allocation did not affect either the total yield of milk during the experimental period, 1717 and 1697 kg, or the total lactation yield, 5635 and 5711 kg, for the uniform and yield-related allocation methods respectively. The butterfat and protein concentrations of the milk were not significantly affected by either the degree of silage chopping or the method of concentrate allocation.     

A study of the efficacy of a bacterial inoculant and formic acid as additives for grass silage in terms of milk production

In a two-year experiment, three silages were prepared from herbage treated either with an inoculant at 1·25 × 10⁵ organisms (g fresh material (FM))⁻¹. formic acid (850 g kg⁻¹) at 4 1 (t FM)⁻¹, or no additive (untreated). In Experiment 1, unwilted and in Experiment 2, wilted silages were investigated and had mean dry matter (DM) and water soluble carbohydrate (WSC) concentrations at ensiling of 171 g kg⁻¹ and 17·6 g (kg FM)⁻¹ and 263 g kg⁻¹ and 25·1 g (kg FM)⁻¹, respectively. In Experiment 1, 45 and in Experiment 2, 54 individually fed cows were used to evaluate the silages in three-treatment, randomized-block design experiments. During weeks 4-12 of lactation the cows were offered silages ad libitum and during weeks 15-26 a constant amount of silage was fed. There were few major differences in chemical composition of the resulting silages. Formic acid had no effect on silage digestibility. Inoculant treatment increased digestibility when the grass had been wilted. The use of formic acid resulted in increased silage DM intake of 9% during weeks 4-12 of lactation in Experiment 1 but not in Experiment 2. The inoculant gave no increase in silage DM intake over the control in Experiment 1 but increased silage DM intake by 7% in Experiment 2. There was no significant response in milk yield to formic acid. In Experiment 2 the response in milk yield to inoculant treatment was significant both in weeks 4-12 of lactation (4%) and in weeks 15-26 of lactation (5%). It is concluded that the response in milk yield to the use of a specific inoculant appears to be mediated through increased intake of metabolizable energy (ME).     

Influence of maceration at cutting on lactic acid bacteria populations, silage fermentation and voluntary intake and digestibility of precision-chopped lucerne silage

Laboratory experiments with lucerne (Medicago sativa) have shown that maceration at cutting improves silage fermentation. Samples taken during wilting and after various ensiling periods were analysed for lactic acid bacteria (LAB) numbers and indices of silage fermentation. In Experiment 1, in which maceration was tested in unwilted and wilted lucerne, there was an additive effect of maceration and wilting on LAB numbers at ensiling, thus LAB numbers were approximately 108 colony-forming units (cfu) g^?1 fresh crop for wilted, macerated forage compared with 103 cfu g^?1 fresh crop for unwilted, unmacerated forage at ensiling. Initially, maceration reduced pH (P < 0·001) and increased lactic acid (unwilted comparison only; P < 0·001) and insoluble N (wilted comparison only; P < 0·001) concentrations. After 70 d ensiling, beneficial effects of maceration were associated only with the wilted silage. In Experiment 2, macerated lucerne was compared with unmacerated material, which was either ensiled after a wilting period of similar length or after wilting had proceeded to the same DM concentration as in the macerated forage. During wilting, LAB numbers were significantly higher in macerated than unmacerated forage (P < 0·05). This was also the case during the first 16 h of ensiling (P < 0·01). A decline in pH was observed earlier in macerated silage. Two days after ensiling, lactic acid concentration was higher in macerated silage (P < 0·05), but insoluble N concentration was not different. In a third experiment, unconditioned forage was compared with forages ensiled after regular conditioning or maceration. Although drying rate over 30 h was not influenced by degree of conditioning, LAB numbers during wilting increased with the degree of conditioning. In silages made from these treatments after 6 h wilting, there were no major effects on fermentation characteristics. In a fourth experiment, digestibility and voluntary intake of precision-chopped silage were measured in sheep and found not to be increased by maceration. It was concluded that maceration per se resulted in marginal improvements in fermentation; however, when maceration also increased DM concentration, fermentation was markedly improved. In these precision-chopped silages, maceration had no effect on intake or digestibility.     

Silage and milk production: a comparison between unwilted and wilted grass silages

Three grass silages made in sunny weather in early July from second-harvest perennial ryegrass were compared in a 16-week feeding experiment with twelve Ayrshire cows. The silages were either unwilted or wilted with and without conditioning, and had mean dry matter (DM) concentrations of 201, 261 and 272 g kg⁻¹, and in vitro DOMD concentrations of 650, 669 and 672 g kg⁻¹ DM respectively. All the silages had formic acid ('Add-F') applied at a rate of 2.6 litres t⁻¹ and were offered ad libitum plus 6 kg concentrates per cow per d. The daily intakes of silage DM were 905 kg per cow on the unwilted treatment and 9.86 and 9.65 kg on the wilted treatments with and without conditioning respectively. Daily milk yields were 171, 17.6 and 17.4 kg per cow on the unwilted, and wilted with and without conditioning treatments respectively and were not significantly different. Fat concentrations in the milk were not affected significantly by treatment, whereas the crude protein and solids-not-fat concentrations were significantly higher on the wilted than on the unwilted treatment. The efficiency of utilization of metabolizable energy for lactation was 6–7% lower with the wilted than with the unwilted silages and it is concluded that the unwilted silage was superior to the wilted silages as a feed for dairy cows.     

The effect of wilting and silage additives on the fermentation of autumn made grass silage ensiled in bunkers on commercial farms in South Wales 1983-85

Silage making practices in respect of 130 samples of autumn made grass silages ensiled in bunkers on commercial farms in South Wales during 1983-1985 were analysed to discern the effect of wilting and/or silage additives on fermentation. Silages were primarily made during late September and early October in fine weather from perennial ryegrass pasture which had not been grazed for 6 weeks. On average 13.9 ha of pasture was cut for silage. Analysis of 120 samples of grass showed it contained 176 g kg^?1 dry matter (DM) with (g kg^?1 DM) 215 protein, 240 modified acid detergent fibre (MADF), 78 water-soluble carbohydrate (WSC) and 95 ash. Most farmers attempted to pre-wilt grass for 1 day prior to ensilage and one quarter of them made unwilted silage. Silage making was usually completed within 6 days of starting to cut and was generally made with a precision-chop machine. Silage additives applied were (kg t^?1) formic acid (4·7), formic acid 4-formalin (5·5), sulphuric acid-+ formalin (5·0) sugars (14) and inoculants (0·65). Formic acid significantly reduced pH, and formic acid with or without formalin significantly reduced ammonia nitrogen (N) content of silages compared with other treatments. Protein contents of acid/formalin treated silages were significantly higher and MADF of acid with or without formalin treated silages were significantly lower than other treatments. Pre-wilting grass prior to ensilage did not significantly increase subsequent silage DM content and significantly increased the pH of non-additive treated silages. Unwilted silages treated with formic acid with or without formalin had a significantly lower ammonia-N content and higher residual WSC than other treatments. It is suggested that only formic acid application either alone or in conjunction with formalin to unwilted silage was successful in producing well preserved silages and that a grass WSC content of 17 g kg^?1 would be necessary to achieve this.     

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.     

An evaluation of three bacterial inoculants and formic acid as additives for first harvest grass

An experiment was carried out during 1984 to study the effect of treating grass at ensiling with three commercially available inoculant-type additives (H/M Inoculant, Grass Sile and Siron), formic acid (850 g kg⁻¹; Add-F) or no additive on grass preservation, in-silo loss, intake and animal performance. Primary growth grass ensiled from 28–29 May into concrete-walled covered silos was of high dry matter (DM, 234 g kg⁻¹), water-soluble carbohydrate content (WSC. 212 g kg DM⁻¹) and digestibility (MADF, 250 g kg DM⁻¹).
The untreated silage displayed good preservation and with the exception of the Sirontreated silage which showed significantly lower buffering capacity (Be) and volatile fatty acid (VFA) contents than the untreated silage, the application of inoculant-type additives did not improve silage preservation or decrease in-silo DM losses. The formic acid-treated silage displayed significantly lower Be, water-soluble carbohydrate, ash, ammonia nitrogen (g kg total N⁻¹) and lactate contents than the untreated silage.
After a 133 d storage period, silages were offered to finishing beef cattle for an 84-d period. Cattle offered the silages displayed similar and non-significant daily DM intakes, daily liveweight gains, dressing proportions and daily carcass gains. From this experiment it appears unlikely that any of the additives evaluated will improve animal performance relative to a well-preserved untreated silage.     

SILAGE AND MILK PRODUCTION, A COMPARISON BETWEEN WILTED AND UNWILTED GRASS SILAGES MADE WITH AND WITHOUT FORMIC ACID

Three grass silages, all made in mid-Jnne from the same herbage, were compared in a 12-week winter-feeding experiment with 12 Ayrshire cows. The silages were fed ad lib. with a supplement of moist barley and gronndnut cake. Silage A was made from unwilted berbage with no additive, silage B from identical berbage treated with 1/2 gal of formic acidJton (2.24 L/tonne) of berbage, and silage C from the herbage after wilting for 28 b. the DM contents of silages A, B and C were 20.5, 21.1 and 31.8%, respectively, and the contents of digestible organic matter in the DM were 58.9, 68.8 and 67.8%. Silage and total DM intake were bigbest on the treatment containing silage B. the mean dafly milk yields on the treatments with sflages A, B and C were 35.1, 38.0 and 34.3 Ib (15.9, 17.2 and 15.6 kg), respectively and the solids-not-fat (S.N.F.) contents of the milk averaged 8.53, 8.54 and 8.50%. It is concluded tbat silage B, the unwilted silage with formic-acid additive, was superior to botb the untreated and the wilted silage as a feed for dairy cows.