Silage and milk production: studies with diets containing white clover silage

In three separate feeding experiments using a total of twenty-six individually-housed Ayrshire cows, three wilted silages made from Blanca white clover were offered ad libitum with either different supplements or different proportions of grass silage. The clover silages contained 680 g white clover kg⁻¹ on a DM basis, and had a mean DM concentration of 263 g kg⁻¹ with 231 g CP kg⁻¹ DM and 91 g ammonia-N kg⁻¹ N. The pH values averaged 4·16 and the DOMD concentrations 611 g kg⁻¹. In experiment 1 the daily intake of clover silage given alone was 15.2 kg DM per cow, i.e. 30·1 g kg⁻¹ live weight, and decreased by 0·76 kg DM kg⁻¹ barley DM and by 0·66 kg DM kg⁻¹barley plus soybean meal DM when these feeds were offered as supplements. Milk yield and fat concentration were higher on the supplement treatments than on the clover silage-only treatment. In experiments 2 and 3 the intakes of silage and total DM increased as the weight of clover in the diet increased from 0 to 700 g kg⁻¹ with parallel increases in milk yield. The effects on milk composition were small and generally non-significant. Although white clover silages with excellent fermentations were made, it is concluded that the main role of white clover in a silage system will be in mixed swards with grass to reduce the input of fertilizer N and to increase the voluntary intake of silage.     

Silage and milk production: a comparison between concentrates containing different amounts of protected protein as supplements for silage of high digestibility

Grass silage made in late May from S24 perennial ryegrass was offered ad libitum to eight Ayshire cows in a 16-week feeding experiment. The silage had a DM concentration of 244 g kg⁻¹, contained 163 g crude protein (kg DM)⁻¹ with a ruminal degradability of 0.77 and had an in vitro DOMD concentration of 678 g kg⁻¹. In addition, four concentrates each containing 167 g soya-bean meal kg⁻¹ were consumed at a mean daily rate of 6.43 kg DM per cow. The soya-bean meal was either untreated, or 'protected' by formalin and mixed in the following proportions, 100:0; 66:34; 34:66; and 0:100 respectively, in the four concentrates. The daily intakes of silage DM were not significantly different on the four treatments and averaged 90 kg DM per cow, giving a mean total daily DM intake of 32.4 g kg⁻¹ live weight. The milk yields were not significantly different on the four treatments and averaged 23.9 kg ⁻¹ The treatments had small and non-significant effects on milk composition and live weight. It is concluded that with a high-digestibility, well-preserved grass silage of satisfactory protein content the inclusion of 'protected' protein in the supplementary concentrate had no beneficial effects on milk production.     

Silage and milk production: studies with molasses and formic acid as additives for grass silage

In two separate feeding experiments using a total of twenty-four individually housed Ayrshire cows six silages made from perennial ryegrass were offered ad libitum with supplements of concentrates. In Experiment I herbage with a dry matter (DM) concentration of 225 g kg⁻¹ received either formic acid ('Add-F') at the rate of 2·0 litres t⁻¹ or undiluted cane molasses at rates of 10, 20 and 30 litres t^−l; the mean daily silage intakes were 9·54, 908, 9·27 and 9·49 kg DM per cow and the daily milk yields, corrected to 40 g fat kg⁻¹, were 23·2, 22·3, 22·8 and 22·9 kg per cow respectively but none of the differences between the four treatments was significant. In Experiment 2 herbage with a DM concentration of 269 g kg⁻¹ received formic acid at a uniform rate of 2·6 litres t⁻¹ either with or without an additional application of molasses at 20 litres t⁻¹; the mean daily silage DM intakes were 8·70 and 9·28 kg per cow and the daily fat-corrected milk yields were 22·2 and 21·9 kg per cow respectively and were not significantly different. In both experiments the effects of the treatments on milk composition were small and not significant. It is concluded that there were no advantages in applying molasses to herbage treated with formic acid, and that the rate of application of molasses to untreated herbage which equated with the formic acid application was 20·30 litres t^−l when assessed on the basis of silage composition, intake and milk production.     

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.     

Silage and milk production: a comparison between three rates of high-protein concentrate supplementation of grass silages of two digestibilities

Grass silages made from first-harvest perennial ryegrass in mid-May and early-June and termed high-D and low-D respectively had mean DOMD values of 694 and 633 g kg⁻¹ and were offered ad libitum to twelve Ayrshire cows in a 16-week feeding experiment using a cyclic changeover design. The silages were supplemented with a concentrate containing 363g CP per kg DM at daily rates of 1.5, 3.0 and 4.5 kg per cow. The average daily intakes of silage DM were 12.6 and 11.1 kg per cow on the high- and low-D silage treatments respectively, and were not significantly different on the three concentrate treatments. The mean daily milk yields were 171, 18.6 and 21.0 kg per cow on the low-D silage treatments, and 19.6, 21.2 and 22.8 kg per cow on the high-D silage treatments at the 1.5, 3.0 and 4.5 kg rates of concentrate feeding respectively. Fat and lactose concentrations in the milk were not affected significantly by treatment, whereas the CP and SNF concentrations increased progressively and significantly as the rate of supplementary feeding increased. It is concluded that a high-protein concentrate supplement allows silage to make the maximum contribution in the diet, and gives a high response in terms of milk yield and composition.     

Comparison of a straw/concentrate mixture with silage as a buffer feed for grazing dairy cows

Over a 24-week period during the 1986 summer, three groups of January- to March-calving dairy cows were either grazed conventionally (G) or grazed between morning and afternoon milkings and housed overnight and offered grass silage (Si) or a straw/concentrate mixture (St) ad libitum. The straw/concentrate mixture contained proportionately, 0-33 long barley straw, 0·28 ground barley, 0·12 soya bean meal, 0·25 molaferm and 0·22 minerals. The metabolizable energy (ME) and crude protein (CP) contents of the silage fed in weeks 1-8 and weeks 9-24 were 9-5 and 10⁻⁶ MJ kg MD⁻¹ and 160 and 191 g kg DM⁻¹ respectively. The straw mix had an ME content of 10⁻¹ MJ kg DM⁻¹ and CP content of 134 g kg DM⁻¹. Partial storage feeding with silage or a straw/concentrate mixture led to a decrease in estimated herbage DM intake. The feeding of the straw/concentrate mixture increased total DM intake, but the estimated total ME intake was similar for treatments G and St. The intakes (kg DM d⁻¹) for treatments G, Si and St were respectively, herbage 11·7,6·8,4·1; total l3·5,13·6,15·0; total ME intake (MJd⁻¹) 163, 155, 163.
Animal performance was, for treatments G, Si and St respectively: milk yield (kg d⁻¹) 19·2, 17·5, 19·1 (s.e.d. 0-87); milk fat content (g kg⁻¹) 36·9, 37·6, 37.1 (s.e.d. 1.22); milk protein content (g kg⁻¹) 35·3, 32·9, 33·4 (s.e.d. 0·76).     

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).     

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.     

Effect of stage of maturity of whole-crop barley on intake and liveweight gain by dairy steers differing in initial live weight

The effect of maturity at harvest of whole-crop barley for ensiling on intake and liveweight gain of dairy steers differing in initial live weight (LW) was evaluated in an experiment over two years. Light (104–120 kg) and heavy (402–419 kg) dairy steers were fed diets containing predominantly whole-crop barley silage harvested at the milk stage [dry matter (DM) content of 284 g kg⁻¹ and neutral-detergent fibre (NDF) concentration of 526 g kg⁻¹ DM] or the dough stage of maturity (DM content of 328 g kg⁻¹ and NDF concentration of 445 g kg⁻¹ DM) and supplemented with up to 1 kg of concentrate. Dry matter intake (g kg⁻¹ LW) was higher for whole-crop barley harvested at the dough stage than at the milk stage of maturity and the difference was greater in heavy than in light steers ( P <  0·001). Liveweight gain was higher and feed conversion ratio was lower for dough-stage compared with milk-stage silage ( P  <   0·05) but there was no interaction with size of steer. Whole-crop barley harvested at the dough stage of maturity promoted higher liveweight gains in dairy steers compared with whole-crop barley harvested at the milk stage due to a higher DM intake.     

Effects of the amount of barley and time of access to grass silage on the voluntary intake, eating behaviour and production of dairy cows

Three separate changeover experiments were conducted to investigate the effect of the amount of rolled barley and time of access to silage on the voluntary intake, eating behaviour and production of dairy cows. In Experiment 1, twenty-four milking cows were used to compare the effect of 4 1 and 6 1 kg d⁻¹ rolled barley on voluntary intake and milk production. In Experiment 2, fourteen cows were used in a comparison of the effect on voluntary intake and milk production of 5- and 22-h access to silage. Experiment 3 measured the effects on intake of silage of 2 and 4 kg d⁻¹ rolled barley and of 5- and 22-h access to silage. In Experiment I, increasing the amount of barley eaten reduced intake of silage by 0–50 kg dry matter (DM) per kg barley DM but in Experiment 3 with 5-h access to silage there was no significant difference between the amounts of silage eaten with 2 and 4 kg d⁻¹ barley. However, in Experiment 3 when allowed 22-h access to silage, the replacement rate was 0–53 kg DM silage per kg DM barley. Increasing access from 5 to 22 h increased silage intake by 37% in Experiment 1 and by 27% in Experiment 3. Milk yield was significantly increased by 4% when extra barley was given in Experiment 1 but there was no significant effect in Experiment 3. Increasing the time of access to silage led to an 11% increase in milk yield in Experiment 2 but there was no significant effect in Experiment 3. There was much variation between cows in the depression of silage intake per kg change in barley DM eaten with coefficients of variation of 131% and 109% in Experiments 1 and 3, respectively. When allowed access to silage for 22 h daily, on average, each cow spent 180 min eating silage in ten meals, although there was appreciable variation between cows in eating behaviour. The amount of barley did not affect the cows' rate of eating silage nor the duration of eating.     

The effect of an acid salt-type additive on the fermentation of grass silages made in bunker silos on commercial dairy farms in Wales

The fermentation characteristics and chemical composition of 57 first-cut and 30 second-cut samples of grass silages, made in bunker silos on commercial dairy farms in Wales in 1990, and treated with a nominal 61 t⁻¹ of an acid salt-type additive at ensilage, is described. Typical chemical composition of grass cut for ensilage was 156 g kg⁻¹ dry matter (DM) and 28 g kg⁻¹ water soluble carbohydrate (WSC), with 181 g (kg DM) ⁻¹ crude protein (CP) and 232 g (kg DM) ⁻¹ modified acid detergent fibre (MADF). The effect of additive use was to produce silages with DM 230 g kg⁻¹ pH 3·93, ammonia N 70 g kg⁻¹ total N, with residual WSC 35 g (kg DM) ⁻¹, lactic acid 83 g (kg DM) ⁻¹, total acids 118 g (kg DM) ⁻¹ and butyric acid 0·7 g (kg DM) ⁻¹. No significant differences were found between first- and second-cut silages. Silage fermentation was restricted (i.e. lactic acid less than 60 g kg DM⁻¹) in only 20% of the samples.
It is suggested that on commercial farms the application rate achieved may be insufficient to produce a restricted fermentation.     

Supplementary forage for grazing sheep. 1. Effects on lactating ewes and lambs

In two experiments, ewes in weeks 1–20 of lactation received either pasture only or pasture plus ad libitum conserved forage. Herbage height was maintained at 3·3–3·4 cm on both treatments by manipulation of stocking rate in the 24 plots (twelve per treatment) used for the experiment with additional ewes and lambs. In experiment 1, silage, which was of lower metabolizable energy (ME) and crude protein (CP) contents than the grazed herbage, was consumed at an average of 375 g dry matter (DM) ewe⁻¹ d⁻¹. In experiment 2 a strawmix, containing (g kg ⁻¹ freshweight) 480 g barley straw, 300 g concentrate and 220 g molasses, again with a lower ME and CP content than the grazed herbage, was consumed at an average of 165 g DM ewe ⁻¹ d ⁻¹. In both experiments ewes not receiving forage lost weight whereas those with forage gained weight and tended to have increased body condition scores. Offering silage or strawmix did not affect lamb liveweight gain or stocking rate.     

Dry-matter yield and herbage quality of a perennial ryegrass/white clover sward in a rotational grazing and cutting system

The expected reduction in the use of fertilizer nitrogen (N) on grassland in the Netherlands has led to renewed interest in white clover. Therefore, the performance of a newly sown perennial ryegrass/white clover sward on clay soil was assessed during 4 consecutive years. The experiment consisted of all combinations of two defoliation systems, i.e. one or two silage cuts per year (S1, S2), spring N application rate, i.e. 0 or 50 kg ha⁻¹ year⁻¹ (N₀, N₅₀), and the management system, i.e. rotational grazing and cutting, or cutting only (RGC, CO). The overall mean white clover cover was 30%. All treatments affected white clover cover, which was 8% higher with S2 than with S1, 6% higher with N₀ than with N₅₀ and 12% higher with CO than with RGC. The overall mean annual dry-matter (DM) yield (13·1 t ha⁻¹ year⁻¹) was significantly affected only by the management system: in two relatively wetter years, the annual DM yield was 1·19 t ha⁻¹ higher with RGC than with CO, whereas there was no difference in two relatively drier years. Nitrogen application increased the DM yield in the first cut by 7·0 kg kg⁻¹ N applied, but had no significant effect on the annual DM yield. Herbage quality was not affected by the experimental treatments. The average in vitro organic matter digestibility was 0.801, and the average crude protein content was 193 g kg⁻¹ DM. With the expected reduction in the use of fertilizer N, perennial ryegrass/white clover swards should be seriously considered as an alternative option to perennial ryegrass swards on these clay soils.     

Silage and milk production: a comparison between long, chopped and ground hays as supplements to silage of high digestibility

Grass silage made in May from S24 perennial ryegrass had a DM concentration of 262 g kg^-1 and an in vitro D-value of 0·698, and was given ad libitum to twelve Ayrshire cows in a 16-week feeding experiment. In addition supplements of hay with a mean in vitro D-value of 0·603 were offered in one of three forms—long, chopped (12·1 mm) or ground (0·80 modulus of fineness) and cubed—and of concentrates given at either 2 or 4 kg per 10 kg milk. Hay averaged 18·2% of total forage DM intake with mean daily intakes of 1·28, 1·22 and 2·26 kg DM per cow in the long, short and ground forms respectively. The highest daily intakes of forage, i.e. silage plus hay, occurred on the ground hay treatments, with values of 10·24 and 9·25 kg DM per cow on the 2 and 4 kg concentrate treatments respectively. The mean daily milk yields were 18·2,18·2 and 19·2 kg per cow on the long, short and ground hay treatments respectively but the increase in yield with the ground hay was only significant at the low level of concentrate intake. The hay treatments had small and non-significant effects on milk composition. It is concluded that ground hay was superior to either long or chopped hay as a supplement for silage, but the small advantages depended on the level of concentrate intake.     

Silage and milk production. A comparision between barley and groundnut cake as supplements to silage of high digestibility

Grass silage of hjgh digestibility made in late May from S23 perennial ryegrass was offered to twelve Ayrshire cows in a 16-week winter-feeding experiment. The silage had a DM content of 27.2% and contained 147% crude protein and 70.3% digestible organic matter in the DM. The silage was fed ad libitum and was the sole feed in the control treatment. In the other three treatments the silage was supplemented with barley, groundnut cake or a mixture of barley and groundnut supplying 4.7, 1.5 and 4.7 kg DM per cow per day respectively. The daily intakes of silage DM were 10.8 kg per cow in the control treatment and 8.6, 11.1 and 9.3 kg per cow in the barley, groundnut and barley plus groundnut treatments, respectively. The daily yields of milk were 14.6 kg per cow in the control, and 16.1, 17.6 and 17.9 kg per cow in the three supplement treatments, respectively. The fat content of the milk was highest in the barley treatment, whereas the SNF and CP contents were highest in the barley plus groundnut treatment. It is concluded that with a high digestibility silage, a supplement of groundnut cake was superior to barley for milk production.     

Ensiling of manured crops—effects on fermentation

The quality of silage from crops fertilized with cattle manure and an inorganic fertilizer was compared in experiments from 1985 to 1989. Manure was spread either as farmyard manure (FYM, 25t ha⁻¹) or as slurry (20-50t ha⁻¹). Crops were direct cut (approximately 200 g DM kg⁻¹) or wilted (approximately 300 g DM kg⁻¹), precision chopped and ensiled in experimental silos. Silage was treated with 4 kg 85% fonnic acid t⁻¹ fresh matter (FM), an inoculant or no additives. The use of manure, particularly FYM, resulted in more Bacillus spores on crops at harvest compared with fertilized crops. Clostridium spores increased as a result of manuring in 1989 only on FYM-treated crops. Differences in the chemical composition of crops were usually small between fertilizer treatments. The quality of silage from slurry-dressed crops, compared with that of silage from fertilized crops, varied between years. The FYM resulted in reduced silage quality, i.e. high pH values (> 4·5), high ammonia N (> 150 g kg⁻¹ total N) and butyric acid (> 6·3 g kg⁻¹ water) concentrations, and high numbers of Bacillus (10⁵ g⁻¹ FM) and Clostridium spores (10⁵ g⁻¹ FM). The concentration of lactic acid was low (≤ 12 g kg⁻¹ water). Wilting and additives generally improved silage quality and reduced the differences between treatments. However, the efficiency of the inoculant on farmyard manured crops was limited.     

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.     

Growth performance, appetite and plasma ammonia concentrations in heifers fed inoculated lucerne prior to ensilage, then supplemented with sodium bicarbonate

A study was conducted to explore the possibility of a synergistic effect of an inoculum of lactic acid bacteria and sodium bicarbonate in improving the nutritive value of lucerne silage. Twenty Holstein heifers (live weight 183 ± 9·4 kg) were assigned to four dietary treatments consisting of: lucerne uninoculated or inoculated prior to ensilage and then either unsupplemented or supplemented with NaHCO₃ (40 g kg⁻¹ dry matter (DM)). The lucerne silage contained 320 g kg⁻¹ DM and constituted 600 kg⁻¹ diet DM. The animals were fed once daily for 90 d and samples of jugular blood were analysed for plasma ammonia and indices of blood acid-base status. Inoculation of Lucerne reduced ( P <0·01) silage pH but had no other effect on silage composition. In the absence of NaHCO₃, liveweight gain and organic matter intake were improved by inoculating lucerne prior to ensilage; however, in the presence of NaHCO₃, inoculation reduced growth rate but had no major effect on intake. Dietary treatment did not (P>0·05) affect the concentration of plasma ammonia or measures bf blood acid-base status. The results suggest that NaHCO₃ may have nullifled any potential benefit of inoculating lucerne silage to improve its nutritive value for heifers.     

A comparison of formic acid and an acid-salt type additive on the performance of dairy cows in early lactation

Perennial ryegrass, harvested as second-cut material on 10 and 11 July 1990, was treated with either formic acid at 31 t^-1 or an acid-salt type additive at 61 t^-1 and ensiled in roofed 150 t bunker silos. Subsequently both silages underwent a predominantly lactic fermentation. Nevertheless the acid-salt-treated silage had a significantly higher quantity of formic acid (19 vs 12 g kg DM^-1) and significantly lower levels of lactic (98 vs 118 g kg DM^-1) and acetic acid (11 vs 17 g kg DM^-1) compared with formic acid-treated silage. In-silo losses and effluent production were similar.
Each silage was individually fed to 10 October-calving Friesian dairy cows (average weight 565 kg) from weeks 2 to 15 of lactation, together with 3 kg d^-1 of a compound feed containing 190 g kg DM^-1 crude protein and with an estimated metabolizable energy content of 12·6 MJ kg DM^-1. The acid-salt additive had no significant effect on silage DM intake, daily milk yield, milk protein or cow liveweight change, but significantly increased milk butterfat content compared with formic acid-treated silage.
It is concluded that the acid-salt type additive produced little difference in terms of either silage fermentation or animal performance compared with formic add treatment.     

Seasonal changes in the crude protein concentration of mixed swards of white clover/perennial ryegrass grown without fertilizer N in an organic farming system in the United Kingdom

Changes in the crude protein (CP) concentration of white clover and perennial ryegrass herbage from a mixed sward were determined on six sampling dates from May to October in each of 2 years. The swards were grown without fertilizer N in an organic farming system and continuously grazed by dairy cows during the grazing season. The annual mean contents of white clover in the dry matter (DM) of the sward were 272·3 and 307·0 g kg⁻¹ in Years 1 and 2. The mean CP concentrations of the white clover and perennial ryegrass herbage were 251·6 and 151·9 g kg⁻¹ DM in Year 1 and 271·9 and 174·0 g kg⁻¹ DM in Year 2 respectively. The CP concentration of the white clover increased significantly during the grazing season from 220·0 to 284·1 g kg⁻¹ DM in Year 1 and from 269·0 to 315·5 g kg⁻¹ DM in Year 2. In the perennial ryegrass herbage the CP concentration increased from 112·2 to 172·6 g kg⁻¹ DM in Year 1 and from 142·7 to 239·5 g kg⁻¹ DM in Year 2. The rate of increase during the season in the CP concentration of the perennial ryegrass herbage was similar to the rate of increase recorded in the white clover herbage.