The effect of stage of perennial ryegrass maturity at harvesting, fermentation characteristics and concentrate supplementation, on the quality and intake of grass silage by beef cattle

Abstract Two experiments were carried out in consecutive years to examine the influence of cutting date and restricting fermentation by carboxylic acid treatment on the nutrient intake from grass silage by beef cattle. In year 1, four cutting dates during July and August after a primary growth harvest and, in year 2, five cutting dates of primary growth between mid‐May and early July were examined. Herbage was ensiled either untreated or treated with high levels of acid additive (‘Maxgrass’, mean 8·6 l t^?1). Ninety‐six (year 1) or forty‐eight (year 2) continental cross steers were used in partially balanced changeover design experiments with each silage type either unsupplemented or supplemented with 4·5 (year 1) or 5·5 (year 2) kg concentrates head^?1 d^?1. Silage digestibility declined significantly between initial and final harvest dates (P < 0·001), whereas silage dry‐matter (DM) and digestible energy (DE) intakes were significantly higher in the initial compared with final harvest dates in both years of the study (P < 0·01). Similarly, silage DM and DE intakes, and total DM intakes, of acid‐treated and unsupplemented silages were greater than those of untreated and concentrate supplemented silages, respectively (P < 0·001). The results indicate that earlier cutting dates, and addition of acid to herbage before ensiling, can increase silage DM intake by beef cattle.     

Nitrogen metabolism and milk production in dairy cows fed semi‐restricted amounts of ryegrass–legume silage with birdsfoot trefoil (Lotus corniculatus L.) or white clover (Trifolium repens L.)

In change‐over trials, mid‐lactation dairy cows were fed concentrate‐supplemented, isonitrogenous and isofibrous perennial ryegrass–legume silage diets that satisfied energy requirements but were suboptimal with respect to metabolizable protein supply. Legumes were either birdsfoot trefoil with low levels of condensed tannins (typical for hemiboreal conditions), or white clover. Averaged over two experimental years, birdsfoot trefoil–based silage resulted in lower digestibility (P < 0·001) of dry matter (50 g kg^?1), organic matter (52 g kg^?1), neutral detergent fibre (120 g kg^?1) and nitrogen (24 g kg^?1) and lower rumen total volatile fatty acid concentration (7 mm ; P = 0·009). Milk protein yield was 36 g d^?1 higher with birdsfoot trefoil silage (P = 0·002), while raw milk yield tended to be 0·8 kg d^?1 higher (P = 0·06). Rumen ammonia concentration was similar between diets, but milk urea concentration (P < 0·001), urinary urea excretion (P = 0·002) and faecal‐N proportion (P = 0·001) were higher with birdsfoot trefoil silage. The results suggest that grass–birdsfoot trefoil silage produced in hemiboreal areas exhibits a protein‐sparing effect in dairy rations, despite a low condensed tannin content that is further diluted by companion grasses and ration concentrate proportion.     

Apparent digestibility and nitrogen utilization of diets based on maize silage harvested at three stages of maturity and fed to steers

Advancing maize crop maturity is associated with changes in ear‐to‐stover ratio which may have consequences for the digestibility of the ensiled crop. The apparent digestibility and nitrogen retention of three diets (Early, Mid and Late) containing maize silages made from maize of advancing harvest date [dry matter (DM) contents of the maize silages were 273, 314 and 367 g kg^?1 for the silages in the Early, Mid and Late diets respectively], together with a protein supplement offered in sufficient quantities to make the diets isonitrogenous, were measured in six Holstein–Friesian steers in an incomplete Latin square design with four periods. Dry‐matter intake of maize silage tended to be least for the Early diet and greatest for the Medium diet (P = 0·182). Apparent digestibility of DM and organic matter did not differ between diets. Apparent digestibility of energy was lowest in the Late diet (P = 0·057) and the metabolizable energy concentrations of the three silages were calculated as 11·0, 11·1 and 10·6 MJ kg^?1 DM for the Early, Medium and Late diets respectively (P = 0·068). No differences were detected between diets in starch digestibility but the number of undamaged grains present in the faeces of animals fed the Late diet was significantly higher than with the Early and Mid diets (P = 0·006). The apparent digestibility of neutral‐detergent fibre of the diets reduced significantly as silage DM content increased (P = 0·012) with a similar trend for the apparent digestibility of acid‐detergent fibre (P = 0·078). Apparent digestibility of nitrogen (N) was similar for the Early and Mid diets, both being greater than the Late diet (P = 0·035). Nitrogen retention did not differ between diets. It was concluded that delaying harvest until the DM content is above 300 g kg^?1 can negatively affect the nutritive value of maize silage in the UK.     

Effects of two mixtures of perennial ryegrass cultivars with contrasting heading dates, and differing in spring-grazing frequency and silage harvest date, on characteristics of silage from first-cut swards

This experiment quantified the effects of: (i) heading date of perennial ryegrass, (ii) grazing frequency in spring and (iii) date of silage harvest, on the ensilability of herbages harvested for silage, and on the conservation and estimated nutritive value of the resultant silages. Replicated field plots with two perennial ryegrass mixtures (intermediate‐ and late‐heading cultivars) were subjected to three spring‐grazing regimes (no grazing, grazing in late March and grazing in both late March and late April) and were harvested on four first‐cut harvest dates between 20 May and 21 June. Herbage from each of the four replicates of these 24 treatments was precision‐chopped and ensiled unwilted and with no additive in laboratory silos. Herbage from the sward with the intermediate‐heading cultivar had a higher (P < 0·001) dry‐matter (DM) content and buffering capacity than that from the late‐heading cultivar, whereas water‐soluble carbohydrate concentrations increased (P < 0·001) with more frequent grazing in spring. Later harvesting enhanced herbage ensilability through an increased (P < 0·001) DM content and reduced (P < 0·001) buffering capacity and pH. Fermentation profiles of the silage were not markedly influenced by the cultivar mixture used but grazing in both late March and late April resulted in a more extensive fermentation with the acids produced increasingly dominated by lactic acid. The concentrations of acetic acid, and to a lesser extent, ethanol declined as silage harvest date was delayed. Overall, the relative effects of grass cultivar mixture were smaller than those of spring‐grazing treatment or silage‐harvesting date although on any given harvest date the herbage from the intermediate‐heading cultivar mixture was easier to preserve as silage than herbage from the late‐heading cultivar mixture. Delaying the harvesting of the late‐heading swards by 8 d removed the differences related to growth stage in buffering capacity, pH and DM content.     

The influence of grass and maize silage quality on apparent diet digestibility, metabolizable energy concentration and intake of finishing beef cattle

The effects of offering a range of grass silages and mixtures of grass and maize silages on the intake of beef cattle were studied. Four grass silages (GS1, GS2, GS3 and GS4) were used. Grass silage 1 was ensiled from a second regrowth in mid‐late September and treated with an inoculant additive. Grass silages 2, 3 and 4 were ensiled, without additive, from a primary regrowth harvested in early July, late May and mid‐June respectively. Wilting periods were 8, 30, 36 and 36 h for GS1, GS2, GS3 and GS4 respectively. Grass silages 1, 2 and 3 were precision chopped and ensiled in bunker silos, while GS4 was ensiled in round bales. The DM content (g kg^?1) and starch concentration (g kg^?1 DM) of the three maize silages (MS1, MS2 and MS3) used were 256 and 128, 256 and 184, and 402 and 328 for MS1, MS2 and MS3 respectively. Seventy‐two Charolais and Limousin cross‐bred steers were used in a changeover design with two 4‐week periods. The study consisted of sixteen treatments incorporating the four grass silages fed alone and with the three maize silages arranged as a 4 × 4 factorial design. The grass silage and maize silage mixtures were offered in a ratio of 0·60:0·40 (DM basis) once daily using individual Calan gates. All silages were offered ad libitum with 3 kg per head per day of a concentrate supplement. Dry matter and metabolizable energy (ME) intakes were highest with diets based on grass silage GS4 compared with diets containing the other grass silages. Metabolizable energy intakes of diets containing no maize silage, and those based on MS1 and MS2, were similar (P > 0·05) but lower than that of diets containing MS3. Only limited increases were found in DM and ME intakes with the inclusion of maize silage in grass silage‐based diets while offering high‐quality grass silage (assessed in terms of DM content, and fibre and N concentrations) promoted high voluntary intakes.     

Yield profile of tall fescue (Festuca arundinacea) in comparison with meadow fescue (F. pratensis) in Finland

Yield profile characteristics of tall fescue (Festuca arundinacea Schreb.), cv. Retu, were compared with those of meadow fescue (Festuca pratensis Huds.). The study was conducted in Finland and was based on official variety trial data recorded between 1980 and 1998 at 17 trial sites between latitudes 60° and 66°N. The crops were managed according to silage‐cutting regimes. The pattern of yield formation of the tall fescue cv. Retu differed significantly from that of meadow fescue cultivars, both within a growing season as well as in sward age. Tall fescue cv. Retu established slowly, and the dry‐matter (DM) yield from the first cut, made in the first year of harvest, was significantly lower than that for meadow fescue. In the second and third years, the DM yield from the first cut did not differ between tall fescue and meadow fescue. Tall fescue produced significantly higher DM yield as regrowth (second and third cuts) than meadow fescue. The sward age significantly affected total DM production. In first‐year swards, there were no significant differences in total DM yield between tall fescue and meadow fescue but, in the second‐ and third‐year swards, tall fescue produced significantly higher DM yields than meadow fescue. The difference in yield profile between tall fescue and meadow fescue was similar in all the environments included in the study. DM yield for the first cut (kg DM ha^–1) for tall fescue cv. Retu, in comparison with meadow fescue cultivars, was 2495 vs. 3099 (P < 0·001), 3735 vs. 3741 (NS, P=0·94) and 3553 vs. 3468 (NS, P=0·30) in the first‐, second‐ and third‐year swards respectively. The respective DM regrowth yields (second plus third cut) were: 6059 vs. 5416 (P < 0·001); 5445 vs. 4221 (P < 0·001); and 5580 vs. 4113 (P < 0·001) in first‐, second‐ and third‐year swards. Total DM yields per season for tall fescue vs. meadow fescue were (kg DM ha^–1) 8554 vs. 8515 (NS, P=0·69), 9180 vs. 7962 (P < 0·001) and 9133 vs. 7581 (P < 0·001) in first‐, second‐ and third‐year swards respectively. Over the three‐year sward rotation period, which is common in Finland, tall fescue produced on average 12% higher DM yield than meadow fescue. Both tall fescue and meadow fescue suffered little winter damage in Finnish conditions; the differences between cultivars of the two species were small. The results indicated that tall fescue cv. Retu is a productive and persistent forage species suited to Finnish growing conditions.     

A meta‐analysis comparing standard polyethylene and oxygen barrier film in terms of losses during storage and aerobic stability of silage

A meta‐analysis was undertaken of 51 comparisons of standard polyethylene film with oxygen barrier (OB) film in covering systems for bunker silos, unwalled clamp silos and bales. Mean losses of DM or OM during storage from the top 10 to 60 cm of bunker and clamp silos were 195 g kg^?1 for standard film and 114 g kg^?1 for OB film systems (41 sets of data, P < 0·001), while mean total losses of DM from baled silage were 76·8 g kg^?1 for standard film and 45·6 g kg^?1 for OB film systems (10 sets of data, P < 0·001). Top surface silage judged subjectively to be inedible was 107 and 29·6 g kg^?1 for standard film and OB film systems respectively (5 sets of data, P = 0·02). Aerobic stability was 75 h for silage stored under standard film system and 135 h for silage stored under OB film system (11 sets of data, P = 0·001). It is concluded that the OB film system reduces losses from the outer layers of silos and from bales and increases the aerobic stability of silage in the outer layers of silos.     

The effects of wilting grass before ensiling on silage intake

Herbage, predominantly perennial ryegrass (Lolium perenne) grown in Northern Ireland, was harvested at four dates from June to October 1996 (H1, H2, H3 and H4). At each harvest approximately one-fifth of the grass harvested was artificially dried and pelleted (G). The remainder of the grass was either wilted for 28–52 h (W), depending on the weather conditions, or ensiled directly, i.e. unwilted (UW). Within the W and UW treatments an inoculant or formic acid additive was applied to the herbage before ensiling. After a minimum ensiling period of 10 weeks, sixty steers, mean initial live weight 432 (s.d. 37) kg, were offered the twenty forages in a four-period partially balanced changeover design experiment. Each period was of 2 weeks’ duration. Dry-matter (DM) intakes were recorded daily, with intakes in the second week of each period used in the statistical analysis of the data. The digestibility of each of the forages was also determined in vivo using four castrated male sheep per silage. Wilting increased the DM content of the silage and the pH, the largest increase in DM content occurring at the second harvest. On average, wilting proportionally increased silage DM intake by 0·21 compared with the unwilted silage (P < 0·001), but the intake of the wilted silage was not significantly different from that of the artificially dried and pelleted grass (P > 0·05). The intake of the wilted silage was higher than that of the unwilted silage at each harvest, the proportional increases being 0·22 (P < 0·001), 0·41 (P < 0·001), 0·19 (P < 0·001) and 0·05 (P > 0·05) at harvests H1, H2, H3 and H4 respectively. Treatment of the grass with formic acid before ensiling resulted in a proportional increase in silage intake of 0·08 compared with the inoculant-treated silage (P < 0·05). Compared with the inoculant-treated silage, formic acid increased silage intake by 0·08, 0·02, 0·14 and 0·10 at harvests H1 (P > 0·05), H2 (P > 0·05), H3 (P < 0·01) and H4 (P < 0·05). The results of this study indicate that the effect of wilting on silage intake varies across different harvests and additive treatments. The difference in response to wilting across different harvests is mainly a result of the prevailing weather conditions during wilting.     

The effect of forage type and level of concentrate supplementation on the performance of spring-calving dairy cows in early lactation

Abstract In 1993 and 1994, 40 cows in early lactation in early spring were assigned randomly to four feeding treatments. One group of cows was kept indoors with access to grass silage ad libitum, plus 6 kg of concentrate daily. The other three groups had access to grass pasture (5–6 h per day in 1993 and 11–12 h per day in 1994) plus grass silage similar to that fed to the previous group while indoors plus 6, 4 or 2 kg of concentrate daily. The average daily allocations of herbage (> 3·5 cm) were 8·5 and 14·0 kg DM cow^?1 day^?1 in 1993 and 1994 respectively. The treatments were applied for 8 weeks (26 February to 23 April) in 1993, and 7 weeks (11 March to 29 April) in 1994. Cows with access to pasture had lower (P < 0·001) silage dry‐matter (DM) intakes and higher (P < 0·001) total forage DM intakes in both years than those kept indoors. This resulted in significantly higher yields of milk, fat, protein and lactose. Similarly, milk protein concentration was higher (P < 0·05 in 1993; P < 0·001 in 1994). There was a significant linear increase in total DM intake in both years with increased concentrate supplementation. In 1993, there was a linear increase in milk (P < 0·01), fat (P < 0·01), protein (P < 0·001) and lactose (P < 0·01) yields with increased concentrate supplementation. In 1994, only milk protein yield (P < 0·05) was increased. Concentrate supplementation had no effect on milk composition or liveweight change. Cows with access to grazed grass had higher liveweight gains (P < 0·05) than those kept indoors in both years. In 1993, increasing the energy intake increased the processing qualities of the milk produced. The results showed that access to grass pasture resulted in higher milk production, in reduced silage requirement and in reduced level of concentrate supplementation required for a given level of milk production with spring‐calving cows in early lactation compared with those kept indoors.     

Characteristics of baled silage made from first and second harvests of wilted and severely wilted forages

First and second harvests of lucerne (Medicago sativa L.), perennial ryegrass (Lolium perenne L.) and a lucerne–perennial ryegrass mixture [80 or 144 g kg^?1 dry matter (DM) of ryegrass] at the first and second harvests were cut and conditioned, wilted to 500 or 700 g DM kg^?1 then baled and stretch‐wrapped for silage on the same dates. Lucerne bales were denser (411 kg m^?3) than bales of perennial ryegrass (331 kg m^?3) (P < 0·05). After an 8‐month storage period, silage made from high DM‐content forage had a higher concentration of neutral‐detergent fibre (NDF) and was less digestible than that made from low DM‐content forage. Daily DM intakes by beef steers, when the silages of the second harvest were fed ad libitum, were 31·2, 31·2 and 22·3 g kg^?1 live weight for lucerne, lucerne–perennial ryegrass mixture and perennial ryegrass silages, respectively (P < 0·01), when the herbage had been wilted to 500 g kg^?1. In vivo digestibility of NDF in the lucerne–perennial ryegrass mixture silage (0·587) was significantly lower than that of perennial ryegrass silage (0·763) but higher than lucerne silage (0·518). Higher intakes of baled lucerne silage tended to offset its lower digestibility values. Lucerne–perennial ryegrass mixture silage had a higher DM and NDF digestibility than lucerne silage, indicating perhaps the presence of associative effects.     

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.     

Effect of wilting,silage additive,PEG treatment and tannin content on the distribution of N between different fractions after ensiling of three different sainfoin (Onobrychis viciifolia) varieties

Sainfoin (Onobrychis viciifolia) is a tanniniferous, leguminous plant that has potentially beneficial effects on protein utilization in ruminants. As ensiling causes protein breakdown and elevated levels of buffer soluble N (BSN), we studied the distribution of N before and after ensiling sainfoin. Three varieties of sainfoin were either direct‐cut and frozen directly or wilted and frozen before later ensiling in mini‐silos with and without acidification with Promyr (PM; an acidifying commercial mixture of propionic and formic acid) and with or without polyethylene glycol (PEG). Extractable tannins (ET) and protein‐bound tannins (PBT) were measured with an HCl/butanol method in an attempt to correlate tannin levels to N fractions. The sainfoin silages showed good ensiling characteristics and had relatively high concentrations of undegraded protein. The effect of wilting on BSN levels (g/kg N) was dependent on sainfoin variety (P < 0·001). PEG increased and PM decreased the level of BSN in the silages (P < 0·001). PM treatment also produced less non‐protein N and ammonia‐N (P < 0·05) as compared with no additive. Addition of PEG to the silage increased the BSN‐proportion 1·8‐ and 2·6‐fold for both DM stages. A strong tannin‐protein binding effect is, therefore, confirmed in sainfoin. However, correlations between tannin levels (ET and PBT) and BSN were poor in the (non‐PEG) silages, indicating either that the HCl/butanol method is unsuitable for measuring tannin in silages or that qualitative attributes of tannins are more relevant than quantitative. The HCl/butanol method seems therefore not to be useful to predict degradation of protein in sainfoin silages.     

The effect of a silage additive and level of concentrate supplementation on silage intake, animal performance and carcass characteristics of finishing beef cattle

An experiment was carried out to examine silage fermentation, effluent production and aerobic stability in unwilted grass silage, which was either ensiled without additive or with a commercially available blend of ammonium hexamethanoate, ammonium hexapropionate and octanoic acid (6 l t^?1, Maxgrass, BP Chemicals Ltd., Northwich, UK) and to determine alternative approaches to obtaining the same performance in finishing beef cattle. Seventy‐two Limousin × Friesian and Charolais × Friesian steers (mean initial live weight 424 kg s.d. 28·3) were blocked into groups of nine according to live weight and previous performance and offered silage, either with or without the additive, and supplemented with 0, 1·5, 3·0 or 4·5 kg d^?1 of a concentrate with a crude protein content of 150 g kg^?1 DM or allocated to a pre‐experimental slaughter group to enable calculation of daily carcass gain. Daily silage intakes were recorded for 112 days. At the end of the experiment, all cattle were slaughtered and daily carcass gain, omental, mesenteric, perinephric and retroperitoneal fat depots [kidney‐knob and channel fat (KKCF)], fatness, conformation, subcutaneous fat depth over M. longissimus dorsi muscle and carcass fat, protein and bone contents were assessed. Across all levels of supplementation, cattle offered the silage with the additive showed significantly (P < 0·001) higher daily DM intakes than those offered the silage without additive. Cattle offered the silage with the additive but unsupplemented had significantly (P < 0·001) higher daily carcass gains than those offered the silage without additive and unsupplemented. The response in carcass gain was 76 and 35 g kg^?1 additional concentrate for the silages with and without the additive respectively.     

Effect of ensiling field bean, field pea and common vetch in different proportions with whole-crop wheat using formic acid or an inoculant on fermentation characteristics

Whole‐crop field bean (FB), field pea (FP) and common vetch (CV) [155, 213 and 238 g dry matter (DM) kg^?1] were ensiled in 1·5 L laboratory silos with whole‐crop wheat as mixtures of 0, 0·25, 0·50, 0·75 and 1·00 of fresh weight (FW). Silages were ensiled (i) without additive, and (ii) with formic acid (FA) (4 L t^?1) or (iii) an inoculant (Lactobacillus plantarum, 10⁶ colony‐forming units g^?1 FW) as additives. The concentrations of water‐soluble carbohydrates in herbage of whole‐crop FB, FP, CV and wheat were 93, 157, 67 and 114 g kg^?1 DM and the buffering capacities were 588, 710, 755 and 429 mEq kg^?1 DM respectively. Field bean and FP silages were mainly well preserved with low pH values and moderate fermentation losses, except for FB‐only silage without additive which had a high butyric acid concentration. Common vetch silages had higher pH values and were less well fermented compared to the silages of the other legumes. For all legumes, FA reduced ammonia‐N concentrations more effectively compared to other additive treatments. In conclusion, in FB and FP silages the use of FA or an inoculant, as additives, ensured good preservation up to a proportion of legume in the herbage of 0·75. With all legume silages, and with those containing CV, only FA, as an additive, adequately restricted protein breakdown.     

Voluntary intake,digestibility and nitrogen utilization by sheep fed ensiled forage legumes

An experiment was conducted to compare the nutritive value of a range of ensiled forage legumes. Silages were prepared from late second‐cut lotus (Lotus corniculatus), first‐cut sainfoin (Onobrychis viciifolia) and both early and late second‐cut red clover (Trifolium pratense) and lucerne (Medicago sativa). Each experimental silage was offered to six Suffolk‐cross wether lambs, aged 10 months, housed in metabolism crates. Voluntary intakes of dry matter ranged from 71 to 81 g kg^?1 liveweight^0·75 d^?1. Voluntary intakes were similar on the lotus, sainfoin and late‐cut red clover silages, but the voluntary intake on the lotus silage was significantly higher than that on the lucerne silages and early‐cut red clover silage. Digestibility of organic matter in the dry matter was highest for the lotus silage (0·650), and lowest for the sainfoin silage (0·527). Although most of the N in the sainfoin silage appeared to be in an indigestible form, N digestibility was approximately 0·70 for the other legume silages. The highest loss of N in urine, 0·75 of N intake, was recorded for lambs offered the lucerne silage. Differences in N intake, N loss in faeces and N loss in urine led to statistically significant differences in the amount of N retained, with the highest and lowest N balances recorded for the lotus (16 g N d^?1) and sainfoin (?2 g N d^?1) silages respectively. The results confirm that these high protein forages have high intake potential. While low N digestibility appears to limit the nutritional value of sainfoin, further research could formulate feeding strategies that improve the efficiency with which the protein from red clover, lucerne and lotus is utilized.     

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

Timothy–meadow fescue herbage was ensiled with formic acid (FA) (expressed as 100% solution) at the rates of 0, 2, 4 or 6 L t^?1. The silages were fed along with concentrates to bulls fitted with cannulae in the rumen and duodenum. The ration comprised grass silage (700 g kg^?1), barley (240 g kg^?1) and rapeseed meal (60 g kg^?1). The application rate of FA had no effect on the site or extent of the digestion of dietary organic matter (OM) and neutral‐detergent fibre. The flow of total N at the duodenum increased linearly (P < 0·05) with application rate of FA, reflecting mainly an increased (P < 0·01) flow of microbial N. The apparent efficiency of net microbial protein synthesis in the rumen increased (P < 0·05), the proportion of propionate in the volatile fatty acids (VFA) in the rumen was not affected (P > 0·05) but that of butyrate increased (linear and quadratic effects, P < 0·01) with increasing rate of FA. It is concluded that an increase in the rate of FA at ensiling leads to a higher utilization of energy and/or protein‐yielding substrates for rumen microbes and to a modified rumen VFA pattern with an increased proportion of butyrate.     

In vitro rumen methane output of grasses and grass silages differing in fermentation characteristics using the gas‐production technique (GPT)

The chemical composition of silage consumed by cattle can influence the subsequent rumen microbial fermentation patterns and methane (CH₄) emissions. The objectives of this study were to (i) evaluate the effect of ensilage on the in vitro rumen methane output of perennial ryegrass and (ii) relate the silage fermentation characteristics of grass silages with in vitro rumen methanogenesis. Three pre‐harvest herbage‐conditioning treatments and seven silage‐additive treatments were used in a laboratory‐scale silo experiment to produce a diversity of silage fermentation characteristics. Ensilage reduced (P < 0·01) the in vitro rumen CH₄ output (mL CH₄ g^?1 dry matter (DM) disappeared). This reflected differences in the direction of rumen fermentation (lower acetic (P < 0·05) and higher propionic (P < 0·001) acid proportions in volatile fatty acids) rather than major changes in the extent of in vitro rumen fermentation (i.e. mmol VFA g^?1 DM). The magnitude of the decrease in CH₄ output (mL g^?1 DM incubated) owing to ensilage increased as the extent of silage fermentation, and in particular the lactic acid concentration, increased. In contrast, among silages with relatively similar extents of silage fermentation (i.e. total fermentation products), an increase in the proportion of lactic acid in silage fermentation products led to a more extensive in vitro rumen fermentation and thus to a greater CH₄ output (mL g^?1 DM).     

Effects of feeding fodder beet and concentrates with different protein contents on dairy cows offered silage ad libitum

In two changeover design experiments, fifteen early- and sixteen late-lactation cows were used to investigate the effects of offering food beet with ad libitum grass silage and concentrates with different CP content on milk yield and quality. In Experiment 1 (early lactation) cows were offered no fodder beet (0) or 4 kg DM d^?1 (4) in conjunction with one of three concentrates containing 159, 191 or 244g CP kg^?1 DM (L.M.H.). Treatments were therefore 1L/0, 1L/4, 1M/0, 1M/4, 1H/0 and 1H/4. In Experiment 2 (late lactation) cows were offered the same level of fodder beet in conjunction with two concentrates containing 129 and 229 (L,H) g CP kg^?1 DM. Treatments were therefore 2L/0, 2L/4, 2H/0 and 2H/4. In both experiments feeding fodder beet reduced silage DM intakes (P < 0·001) and increased total DM intake (P < 0·05 to P < 0·001). The substitution rate (r) ranged from 0·46 to 0·59kg of silage DM (kg^?1 fodder beet DM). In Experiment 1, fodder beet tended to increase milk yield, composition and yield of constituents, but the effect was statistically significant for milk protein content only (P < 0·01). In Experiment 2, milk yields for 2L/0, 2L/4, 2H/0 and 2H/4 were 11·3, 12·1, 11·7 and 12·5 kg d^?1 respectively (s.e.d. 0·43, non-significant), fat contents were 44·4, 47·3, 44·3 and 46·8g fat kg^?1 respectively (s.e.d. 0·73, P < 0·001), protein contents were 34·3, 35·6, 35·3 and 36·2 g protein kg^?1 respectively (s.e.d. 0·28, P < 0·001), fat yields were 494, 574, 512 and 579 g fat d^?1 respectively (s.e.d. 20, P < 0·001) and protein yields were 385, 426, 407 and 442 g protein d^?1 (s.e.d. 13, P < 0·01) respectively. Increasing CP in the concentrate significantly increased milk yield in Experiment 1 (23·9, 22·5, 23·5, 23·8, 26·2, 26·5kg d^?1 for 1L/0, 1L/4, 1M/0, 1M/4, 1H/0 and 1H/4 respectively, P < 0·05). Higher CP in concentrate also resulted in significantly increased milk protein yield in early-lactation (P < 0·001) and milk protein content in late-lactation (P < 0·01) cows. There was a significant interaction between fodder beet and concentrate CP content for milk protein yield (P < 0·001) in Experiment 1.     

Nutritive value of barley/kale bi-crop silage for lactating dairy cows

Six mid‐lactation multiparous Holstein–Friesian dairy cows were used to examine the potential of a fermented whole‐crop barley (Hordeum vulgare)/kale (Brassica oleracea) bi‐crop as a feed compared with a first‐cut perennial ryegrass silage. The barley/kale bi‐crop was grown as a strip intercrop, and was harvested and ensiled as an intimate mixture [0·80 barley and 0·20 kale on a dry‐matter (DM) basis]. Animals were offered ad libitum access to one of three experimental diets in a duplicated Latin Square design experiment: (i) Bi‐crop (the barley/kale bi‐crop); (ii) Grass (the grass silage); and (iii) Mix (a 1:1 fresh mixture of Bi‐crop and Grass). All animals also received a standard dairy concentrate at a rate of 4 kg d^?1 in equal portions at each of two milkings. The Bi‐crop and Grass silages contained 346 and 293 g DM kg^?1, 108 and 168 g crude protein kg^?1 DM, 268 and 36 g starch kg^?1 DM, and had pH values of 3·87 and 3·80 respectively. Animals offered the two bi‐crop silage‐containing diets consumed more forage DM than those offered grass silage (14·6, 14·9 and 12·6 kg DM d^?1 for Bi‐crop, Mix and Grass respectively; s.e.d. 0·45, P < 0·01) and yielded more milk (24·0, 23·9, 22·6 kg d^?1 for Bi‐crop, Mix and Grass respectively; s.e.d. 0·26, P < 0·01). However, differences in the partitioning of dietary nitrogen towards milk protein and away from excretion in urine suggest a more efficient (rumen) utilization of feed protein by animals offered diets containing the bi‐crop silage. It is concluded that, despite having a low crude protein concentration, barley/kale bi‐crop silage offers excellent potential as a feed for lactating dairy cows.     

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.