The effects of forage preservation method and proportion of concentrate on nitrogen digestion and rumen fermentation in cattle

A 6 × 6 Latin square experiment with a 2 × 3 factorial arrangement of treatments was used to study forage preservation method and level of concentrate in a diet on organic matter (OM) and N digestion and rumen fermentation. Six bulls, each fitted with ruminal and duodenal cannulae, were given unwilted silage (S) or barndried grass (G) prepared simultaneously from the same timothy sward. The forages were fed together with 250 (L), 500 (M) or 750(H)g concentrate dry matter (DM)kg^-1 total diet DM. The concentrate consisted of barley (875 gkg^-1) and rapeseed meal (125g kg^-1). The feeding level was 80g DMkg^-1 live weight^0·75. The apparent digestibility of OM was similar for S and G diets, and increased linearly (P < 0·001) with increasing level of concentrate. The flow of microbial N at the duodenum and the apparent efficiency of microbial protein synthesis in the rumen were higher (P < 0·05) with S than with G diets. Increasing the concentrate level increased linearly (P < 0·05) the amounts of total N and microbial N at the duodenum, whereas the synthetic efficiency was not significantly affected. The mean rumen pH decreased linearly (P < 0·001) from 6·43 to 6·03 with increasing concentrate level. The molar proportion of acetate (Ac) in the rumen volatile fatty acids (VFA) showed a linear (P < 0·001) and quadratic (P < 0·01) decrease, and that of butyrate (Bu) a linear (P < 0·001) increase when the level of concentrate was increased. The proportion of propionate decreased slightly with both forages when the amount of concentrate was increased from level L to M. A further increase to level H increased propionate from 157 to 170 mmol mol^-1 of total VFA with S and from 157 to 188 mmol mol^-1 with G, the effect of concentrate level being not significant. The number of protozoa increased linearly (P < 0·001) as the level of concentrate increased. The changes in the rumen fermentation patterns during the feeding cycle were greater for S than for G diets.     

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

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

Potency of microbial inocula from bovine faeces and rumen fluid for in vitro digestion of different tropical forage substrates

In vitro ruminal fermentation techniques rely on the availability of fistulated ruminants for rumen fluid (RF), a major constraint for resource‐poor institutions. An alternative would be to use faecal microbes. This study was therefore designed to compare the potency of fresh bovine faeces against RF as sources of microbial inocula for fermenting six contrasting tropical forages using the Tilley and Terry (Journal of British Grassland Society, 18 , 104–111) technique. Faecal inocula were prepared at concentrations of 250 g (Faec250), 300 g (Faec300), 350 g (Faec350), 400 g (Faec400) and 450 g (Faec450) fresh cow faeces per litre bicarbonate buffer. In vitro organic matter digestibility (IVOMD) increased with increasing concentration of faeces at 12‐, 24‐ and 48‐h incubation intervals. All faecal inocula except Faec450 had lower potency when compared with RF at all incubation intervals. Digestibility of forage substrates with Faec450 (533 ± 23 g kg^?1 DM IVOMD) was comparable to RF (566 ± 5 g kg^?1 DM IVOMD) after 48‐h incubation. Faec450 showed greater potency on more fibrous and low‐protein substrates than RF. The coefficient of determination of the regression models for predicting 12‐, 24‐ and 48‐h RF IVOMD from Faec450 were 0·914, 0·75 and 0·756 respectively. It was concluded that inocula prepared from 450 g cow faeces demonstrated great potential as a substitute and predictor for RF in 48‐h IVOMD assays of tropical forages.     

The effects of offering a range of forage and concentrate supplements on milk production and dry matter intake of grazing dairy cows

An experiment was undertaken to examine the effect of supplement type on herbage intake, total dry matter (DM) intake, animal performance and nitrogen utilization with grazing dairy cows. Twenty‐four spring‐calving dairy cows were allocated to one of six treatments in a partially balanced changeover design with five periods of four weeks. The six treatments were no supplement (NONE), or supplementation with either grass silage (GS), whole‐crop wheat silage (WS), maize silage (MS), rapidly degradable concentrate (RC) or slowly degradable concentrate (SC). Cows were rotationally grazed with a mean herbage allowance of 20·5 kg DM per cow per day, measured above 4 cm. Forage supplements were offered for approximately 2 h immediately after each morning milking, with cows on NONE, RC and SC treatments returning to the grazing paddock immediately after milking. Cows on treatment MS had a significantly higher supplement DM intake than the other treatments but a significantly lower grass DM intake than the other treatments, resulting in no significant difference in total DM intake when compared with cows on treatments WS, RC and SC. Concentrate type had no significant effect on herbage intake, milk yield, milk composition or yield of milk components. The yield of milk fat and milk protein was significantly higher on treatments MS, RC and SC compared with treatments NONE, GS and WS. The results indicate that despite a relatively high substitution rate, maize silage can be a useful supplement for the grazing dairy cow.     

The effect of partial replacement of grass silage with fresh grass on rumen fermentation characteristics and rumen outflow rates in cattle

An experiment was designed to examine the effects of partially replacing extensively fermented grass silage with varying proportions of fresh grass (0, 0–33, 0–67 and 100) on rumen fermentation, degradation of dry matter (DM) and rate of outflow of liquid and particulate phases from the rumen with four mature Limousin steers. The fresh grass had a higher pH and water-soluble carbohydrate and lower ammonia-N and lactic acid concentrations than the silage. Partial replacement of silage with fresh grass resulted in a reduction in rumen ammonia concentration, and in the proportion of rumen propionate, i-butyrate and n -valerate and an increase in the proportion of rumen acetate and in both die particulate and liquid outflow rates from the rumen. These changes in rumen fermentation parameters could account for increases in animal performance in situations in which grass silage is partially replaced with fresh grass.     

The effects of ensiling on dry-matter intake and milk production by lactating dairy cattle given forage as the sole feed

An experiment involving forty-five British Friesian cows in mid-late lactation was carried out to evaluate the effects of ensiling on herbage digestibility, dry-matter intake and milk production. The herbage from the primary growth of a predominantly perennial ryegrass sward that had received 123 kg N ha^?1 was zero grazed (ZG) from 27 April to 24 May 1992. Before going onto the experimental diets all animals were offered a common silage as the sole diet and dry-matter intakes and milk yields were recorded. The herbage was mown, picked-up with a precision-chop harvester and offered as the sole diet, twice daily, 10 fifteen cows that were on average 176 days into lactation. On May 20 herbage from the same sward was harvested identically to the ZG herbage and ensiled, alternative loads being untreated (UT) or treated with formic acid (2.4 l^?1) (FA). For silages UT and FA respectively, pH values were 3.94 and 3.92 and ammonia nitrogen concentrations were 95 and 75 [g(kg total N^?1)]. Forty-two days after ensiling, the silages were fed twice daily as the sole diet to thirty cows which were on average 166 days into lactation. The feeding interval was 28 days and the last 7 days was the main recording period for each treatment. For diets ZG, UT and FA, dry-matter intakes (DMI) (kg d^?1), milk yields (kg d^?1), fat plus protein yields (kg d^?1). milk fat concentration (g kg^?1), milk protein concentration (g kg^?1)and fat plus protein yields [kg (kg DMI)^?1] were 12.70, 11.51 and 12.07 (Av s.e.d. = 0.458); 12.79, 10.01 and 10.18 (Av s.e.d. = 0.346); 0.900, 0.649 and 0.682 (Av s.e.d. = 0.026); 39.8, 33.7 and 36.7 (Av s.e.d. = 0.174); 32.9, 29.9 and 30.0 (Av s.e.d. = 0.83); 0.073, 0.055 and 0.055 (Av s.e.d. = 0.003). UT treatment significantly increased dry matter (DM), organic matter (OM). energy and crude fibre digestibilities and the digestible OM concentration. UT and FA compared with ZG altered rumen fermentation patterns, significantly decreasing butyrate and increasing valerate concentrations. FA treatment significantly decreased the non-glucogenic ratio. It is concluded that ensiling using formic acid had no effect on forage DMI relative to the parent fresh herbage. Ensiling either untreated or with formic acid significantly decreased milk yield and milk fat plus protein yield, resulting in a lower efficiency of conversion of DMI to milk fat plus protein.     

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.     

The influence of forage quality and concentrate level on dry matter intake and milk production of British Friesian heifers

Thirty-six British Friesian heifers were divided into two groups during weeks 3-26 of lactation and received ad libitum either good (G) or average (A) quality grass silage. The in vitro digestible organic matter in the DM was 680 and 600 g kg^-1 for silages G and A, respectively. In addition, the heifers in each group were offered concentrate at either a low (4.3 kg DM d^-1), medium (64 kg DM d^-1) or high (8.4 kg DM d^-1) level. The concentrate contained 180 g (kg DM)^-1 of crude protein and had a calculated metabolizable energy concentration of 12.9 MJ (kg DM)^-1. Increasing concentrate level significantly increased milk yield (P < 0.01), milk protein concentration (P < 0.05), and yield of both milk protein depressed milk fat concentration (P < 0.001) and silage intake (P < 0.001). Although the overall effect of silage quality on milk yield was not significant, the milk yields for silage G at each concentrate level were higher, significantly so for low level, than the corresponding values for silage A. An improvement in silage quality did not affect milk fat concentration but significantly increased the concentration of milk protein (P < 005) and yields of both milk fat (P < 005) and protein (P < 0001). The response of silage DM intake to improved silage quality was 0 06 kg DM per 10 g rise in vitro DOMD value. Each additional kg concentrate DM depressed intake of silages G and A by 0-63 and 0-27 kg DM, respectively. Substitution rate was also significantly related to stage of lactation. With both silages, the digestibility coefficients determined in vivo for acid detergent fibre (ADF) decreased significantly (P < 0.001) when concentrate level was increased from low to high. Differences for DM, OM and total N digestibility coefficients between treatments were not established as significant at the 5% level. Estimates of mean efficiency of utilization of ME for lactation, made on a weekly basis, were 049 and 052 for the heifers given silages G and A. respectively, and 048, 052 and 052 for those given the low, medium and high levels of concentrate. Energy balances were calculated on a mean weekly basis.     

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.     

The effects of rates of application and sources of nitrogen on nitrate concentration in oat forage

A field experiment was conducted during the winter seasons of 1972–73 and 1973–74 to study the effects of rates of application (0, 100, 200 kg ha^?1) and sources of nitrogen (ammonium sulphate, calcium ammonium nitrate, urea, sulphur-coated urea and sulpha-thiazole-treated urea) on nitrate-N concentration in oat (Avena sativa L.) forage. N application increased the nitrate-N concentration, the effects being more marked when the rate was increased from 100 to 200 kg ha^?1 than when it was raised from 0 to 100 kg ha^?1. The highest nitrate-N concentration in the dry matter (> 0·16%) was obtained when calcium ammonium nitrate was applied at 200 kg ha^?1 N. Sulphur-coated urea gave the lowest nitrate-N concentration. In one year treatment of urea with sulphathiazole reduced nitrate-N concentration in oats forage.     

The effect of herbage surface water and the provision of supplementary forage on the intake and feeding behaviour of cattle

High rainfall and the corresponding low herbage DM content has been shown to adversely affect cattle intakes and production. This could arise from physical restrictions on intake or digestion rate, or other behavioural limitations such as reduced palatability. A knowledge of the reason for the intake reduction would assist in determining the optimum supplement to feed. Eight steers were offered four diets in a changeover design. The diets were: A, cut herbage; B, cut herbage with added surface water; C, as B but with a low dry matter (DM) forage supplement (silage); and D, as B but with a high DM forage supplement (hay). The addition of surface water to herbage reduced DM intake and feeding time but had no effect on biting rate or rate of intake. Neither hay nor silage was eaten in sufficient quantities to restore DM intake, even though the silage was of similar nutrient composition to the herbage.     

Stocking method effects on forage accumulation,canopy attributes,and nutritive value of grazed Mulato II brachiariagrass pastures

Rotational stocking (RS) is generally associated with the intensification of pasture-based animal production systems, although many studies have shown little advantage over continuous stocking (CS). The objective of this research was to describe and explain the effects of two average canopy heights (20 and 30 cm) and three stocking methods (CS; rotational stocking with lenient defoliation, RSL; and rotational stocking with moderate defoliation, RSM) on forage accumulation (FA), vertical distribution of plant-part components, and nutritive value of ‘Mulato II’ hybrid brachiariagrass (Brachiaria spp. syn. Urochloa spp.) during two summer rainy seasons in Piracicaba, São Paulo, Brazil. Pastures were maintained at average canopy height of 20 and 30 cm under CS, and treatments under RSL and RSM were imposed by variations of ±20 and 30% of the average canopy heights, representing defoliation intensities of 33 and 47% of the pre-graze heights, respectively. The FA was not affected by CS, RSL, RSM stocking methods, averaging 8090 kg DM ha⁻¹ year⁻¹. Canopy bulk density and distribution of plant-part components in the canopy profile were better at the average canopy height of 20 cm, accompanied by the greater nutritive value. The leaf bulk density was generally greater in RSM compared to CS. Pastures under CS had greater crude protein and in vitro digestible matter, and lesser neutral detergent fibre concentrations. Mulato II brachiariagrass should be managed at an average height of 20 cm under CS.     

The effects of phosphorus and form of nitrogen supply on leaf cell size and nutrient content in Trifolium repens and Lotus uliginosus

White clover (Grasslands Huia) and lotus (Grasslands Maku) were grown in pots of soil at a range of phosphorus supply, and reliant on symbiotic nitrogen fixation (SN plants) or entirely on mineral nitrogen (MN plants). Shoots increased in weight with phosphorus supply. White clover MN shoots were bigger than those of SN plants except at the lowest level of phosphorus supply; lotus MN shoots were only bigger than SN shoots at the highest level of phosphorus supply. Leaf growth rate and size increased with phosphorus supply but were not significantly affected by the nitrogen treatments.
Estimates of cell size were made by determining DNA concentration, by digestion of tissue followed by counting and by taking vinyl impressions of epidermal cell surfaces. Lotus cells are bigger than those of white clover. 'Digested' cell sizes were not significantly affected by changes in phosphorus supply. Epidermal cell size increased with phosphorus supply, but the relationship was weaker in SN than in MN plants. Methods which give values for 'average' cell size are capable of detecting large-scale differences, but methods able to resolve cell heterogeneity are necessary for an accurate picture of the relationship between leaf growth and cellular nutrition.
Average concentrations of total and inorganic phosphorus on a DNA basis did not differ between the species, contrary to concentrations on a dry weight basis, indicating that differences in phosphorus efficiency can be partly explained on the basis of average differences in cell size. Differences in inorganic phosphorous on a DNA basis at higher levels of supply suggested an additional intrinsic difference in cellular accumulation of inorganic phosphorus between the two species.     

Performance and environmental effects of forage production on sandy soils. III. Energy efficiency in forage production from grassland and maize for silage

Based on experimental data gathered in a research project on nitrogen fluxes in intensive dairy farming in Northern Germany, an analysis of fossil energy input and energy efficiency in forage production from permanent grassland and maize for silage was conducted. Field experiments comprised different defoliation systems and different rates of mineral N fertilizer and slurry application. Each change from grazing to cutting in grassland systems reduced the energy efficiency. Energy efficiency consistently decreased with increasing rates of mineral N application. In the production of maize for silage, maximum energy efficiency was obtained with an application of 50 kg N ha^?1 from slurry only. Net energy yields of maize for silage were much higher than that of grassland when compared at the same level of fossil energy and nitrogen fertilizer input. Considering both nitrate‐leaching losses and a necessary minimum quantity of grass herbage in a well‐balanced ration, it is suggested that a high proportion of maize for silage in combination with N‐unfertilized grass/clover swards used in a mixed cutting/grazing system represents a good trade‐off between the leaching of nitrates and energy efficiency.     

Urea supplementation effects on the utilization of low-quality forage and lamb production in patagonian rangelands

The effect of feeding a urea-based supplement for the last 8 weeks of pregnancy was examined on ewes grazing the grass-shrub steppes of NW Patagonia, Argentina. The productivity of ewes and lambs and the utilization rate of the major, less preferred, grass species (Stipa speciosa, 27% cover) was analysed. In a paddock-scale experiment, ewes grazed two areas of 450–500 ha from 15 August to 15 February at a stocking rate of 0·5 ewes ha^?1. From 15 August to 10 October, one group of ewes was given access to a urea-based supplement containing 300 g kg^?1 urea, 320 g kg^?1 salt, 30 g kg^?1 molasses and 300 g kg^?1 bone meal. Average supplement consumption was 3·5 g ewe^?1 d^?1. The performance of 100 ewes in each of the two areas was evaluated. Supplemented ewes gained 4·2 kg more live weight than the control ewes between 15 August and 10 October (prepartum) (liveweight gain was 10·3 vs. 6·1 kg ewe^?1, P < 0·05). The number of live lambs at 8 weeks of age, as a proportion of ewes mated, was 15% higher in the supplemented than in the control group (0·634 vs. 0·553, P < 0·05). A similar increase in the live weight of lambs at 8 weeks of age in the supplemented group compared with the controls was also observed (12·1 vs. 10·6 kg, P < 0·05). In the paddock with the supplemented ewes, there was a significant increase in the proportion of Stipa speciosa plants defoliated (0·62 vs. 0·38, P < 0·05) and in the intensity of defoliation of these plants. It was concluded that urea-based supplements increased productivity of ewes and that this was likely to be associated with an increase in the intake, and possibly digestibility, of the less preferred species such as Stipa speciosa.     

The effect of concentrate feed level on the response of lactating dairy cows to a constant proportion of fodder beet inclusion in a grass silage-based diet

Abstract The effects of level of concentrate supplementation on the response of dairy cows to grass silage‐based diets containing a constant proportion of fodder beet were examined. Forty Holstein‐Friesian dairy cows of mixed parity were used in a 2 × 5 factorial design experiment. Two basal diet types [grass silage alone or grass silage mixed with fodder beet in a 70:30 dry matter (DM) ratio] were offered ad libitum, and the effects of five levels of concentrate supplementation (mean = 3·0, 5·3, 7·5, 9·8 and 12·0 kg DM per cow d^?1) were examined. Concentrate supplements were offered via an out‐of‐parlour feeding system. These treatments were examined in a three‐period (period length = 4 weeks) partially balanced changeover design experiment. Fodder beet inclusion had no significant effect on the estimated metabolizable energy (ME) concentration of the ration (P > 0·001). Total DM intake, estimated ME intake, milk yield, milk protein content and milk energy output all showed significant linear increases with increasing level of concentrate inclusion (P < 0·001) while, in addition, milk yield and milk energy output exhibited a significant quadratic increase (P < 0·01). The inclusion of fodder beet in the diet reduced silage DM intake (P < 0·01) but resulted in an increase in total DM intake and estimated ME intake (P < 0·001). However, inclusion of fodder beet had no significant effect on milk yield (P > 0·05), while increasing milk protein content and milk energy output (P ≤ 0·05). Milk energy output, as a proportion of estimated ME intake, was significantly (P < 0·001) reduced by fodder beet inclusion (0·44 vs. 0·38). Despite large increases in estimated ME intake with the inclusion of fodder beet at all levels of concentrate supplementation, milk energy output responses were small, resulting in an overall reduction in the efficiency of conversion of ME intake into milk energy output. An increased partitioning of dietary ME intake to tissue gain is suggested as the most likely explanation for the observations made.     

The effects of concentrate energy source and protein content on milk production in cows given grass silage ad libitum

Sixteen Friesian cows were given four dietary treatments in a 4 × 4 Latin square experiment with a 2 × 2 factorial arrangement of treatments. The diets consisted of grass silage ad libitum plus 2 kg of hay per day and two types of concentrates of either barley or a mixture of barley, oats and fibrous by-products [200,200 and 600 g per kg dry matter (DM) respectively], with two protein contents. For the low-protein diets, barley- (B) and fibre-based (F) concentrates were given without protein supplements, while for high-protein diets 1 kg of both concentrates was replaced with fish-meal (FM). The concentrates were given at the rate of 9kgd^-1 for the cows (n= 12) and 8kg d^-1 for the heifers (n= 4). The cows given the F diets tended (P < 0·10) to have a greater silage dry matter intake and produced 1·5kg d^-1 more (P < 0·05) milk with a lower (P < 0·05) protein content than those given the B diets. Increasing dietary crude protein concentration with FM had no effect on feed intake but resulted in significant increases in milk yield (P < 0·01), milk protein content (P < 0·05) and yields of milk constituents. The response in milk yield to FM tended to be greater with barley than with fibrous supplement (+2·5 vs+ 1·5kgd^-1). Compared with B diets, the greatest relative increase occurred in lactose yield (0·07) when the corresponding F diets were fed, while FM produced the greatest response in protein yield (0·12). The calculation of the utilization of metabolizable energy (ME) for milk production showed that both the feeding of a concentrate consisting of different carbohydrate sources and inclusion of fish meal improved the utilization of ME, the effects being partially additive. It is concluded that the nutrient supply to the cow's tissues can be modified by the source of carbohydrate and protein supplementation as indicated by different responses in the yield of milk constituents. The production response to protein supplementation may depend on the source of carbohydrate in the concentrate.     

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.     

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

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