Grazing cycle length and silage supplementation: effects on the performance of lactating ewes with twin lambs

Masham ewes, stocked at 20 ewes ha⁻¹, reared twins at pasture in 1979 and 1980 and were rotationally grazed around six paddocks. There were three lengths of grazing cycle (18, 30 or 42 d) and the ewes at pasture were either offered silage ad libitum (S) for 8 weeks of lactation or they were not supplemented with silage (N). By feeding silage, S ewes and lambs moved into greater herbage masses (3735 u. 3390 kg organic matter (OM) ha⁻¹), but there was little effect on net herbage accumulation (10.5 v. 10.0 t OM ha⁻¹) and herbage intakes per ewe were similar (2.31 v . 2.27 kg OM d⁻¹) over the 7-month grazing season. During the period of silage supplementation, total intake was 19% higher for S than N ewes, lamb growth rates were slightly higher (280 v . 273 g d⁻¹) and the ewes lost less weight (−78 v −96 g d⁻¹).
For 18-, 30- and 42-d grazing cycles respectively the herbage masses before grazing were 2825, 3620 and 4240 kg OM ha⁻¹; net herbage accumulations were 9.8, 10.4 and 10.6 t OM ha⁻¹; mean daily herbage intakes by each unit (ewe+lambs) were 2.22, 2.35 and 2.30 kg OM and lamb growth rates from birth to weaning at 20 weeks were 205, 204 and 204 g d⁻¹.
Frequent grazing of relatively light herbage masses or infrequent defoliation of heavier herbage masses made little difference to sward or animal performance. It is concluded that, at this stocking rate, different grazing cycles of 18, 30 or 42 d do not affect the performance of lactating ewes.     

The effects of incorporating small quantities of straw in grass/grass silage-based diets for dairy cows

Two studies were conducted to examine the effects of incorporating small quantities of straw in the diets of dairy cows. In Experiment 1, forty Holstein Friesian dairy cows were used in a 2 × 4 factorial design experiment, with factors examined consisting of two parities (primiparous and multiparous animals) and four levels of straw inclusion in the diet (0, 0·08, 0·16 and 0·24 of forage dry matter). The basal forage offered in this study was grass silage, and the primiparous and multiparous animals were supplemented with 9·0 and 11·0 kg concentrate d^–1 respectively. In Experiment 2, forty‐eight Holstein Friesian dairy cows were used in a 2 × 3 factorial design experiment, with factors examined consisting of two basal forage types (grass silage and zero‐grazed grass) and three levels of straw inclusion (0, 1·0 and 2·0 kg d^–1). All animals were offered 7·0 kg d^–1 of a concentrate supplement. Both experiments were partially balanced changeover designs, consisting of two, 4‐week periods. In Experiment 1, the total dry‐matter intake followed a significant quadratic relationship (P < 0·05), increasing with low levels of straw inclusion and decreasing at higher levels of inclusion. With increasing levels of straw inclusion, there was a linear decline in milk yield (P < 0·001) and milk protein concentration (P < 0·05), but milk fat concentration was unaffected (P > 0·05). In Experiment 2, the effect of straw inclusion on total dry‐matter intake was quadratic (P < 0·001), with intakes being maximum at the 1·0‐kg level of straw inclusion. Milk yield exhibited a linear decrease (P < 0·001) with increasing level of straw inclusion. Milk fat concentration was lowest at the 1·0 kg rate of straw inclusion (P < 0·05), but milk protein concentration was unaffected by straw inclusion. There were no significant interactions between basal forage type and level of straw inclusion for any of the variables examined (P > 0·05). Despite small increases in total dry‐matter intake at a low level of straw inclusion, there was no evidence that straw inclusion improved either nutrient utilization or animal performance. The reduction in milk yield observed with straw inclusion reflects, to a large extent, a reduction in metabolizable energy intake.     

The influence of the system of silage harvesting and feeding and the use of protected protein on milk production

The study compared two systems of silage harvesting, direct-cutting flail harvesting (flail-direct) or pre-cutting, followed by wilting and collection by a meter-chop harvester (precision-wilted). Each silage was self or easy fed to dairy cows. In addition, the response to protected soya bean meal included in the supplementary concentrate was also examined. Approximately 400 t of each of the two silages were produced from the same swards under good weather conditions with formic acid applied as an additive. The resulting silages were well preserved and had mean particle lengths of 43 and 29-mm, and D-values of 0-74 and 0-71 for the flail-direct and precision-wilted silages, respectively. During a 159-d feeding period commencing on 5 November, the silages were offered to 88 British Friesian cows in a 2³ factorial design, continuous feeding experiment. The cows calved during the experiment and had a mean calving date of 18 January. The feeding treatments involved both silage types, two systems of silage feeding (self and easy) and two sources of protein in the supplementary concentrate given after calving (soya bean or 100 g kg^-1 protected soya bean). No concentrates were offered pre-calving and all animals were given 7.6 kg d^-1 concentrates post-calving. There were no significant interactions between the system of silage harvesting and feeding. Animals on the precision-wilted silage consumed 14% more silage dry matter (10.9 vs. 9.6 kg DM d^-1) over the total period and by the end of the experiment were producing 7% less milk per day (25.4 vs. 27.2 kg). However, the responses in the output of total milk constituents (fat and protein) were lower than those obtained in milk yield. Animals offered silage by self feeding had similar dry matter intakes, but produced marginally less milk than those easy-fed. Ration digestibility and nitrogen utilization data, obtained from a concurrent change-over design experiment, suggested that the energy from the precision-wilted silage was less efficiently utilized for milk production. There was no significant response in either milk yield or composition to the inclusion of protected soya bean in the supplement.     

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

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

The effects of intravenous administration of amino acids and glucose on the milk production of dairy cows consuming diets based on grass silage

Two experiments, using intravenous infusion of nutrients, were carried out with the aim of separating milk production responses due to the provision of amino acids as precursors of milk protein synthesis from those due to the provision of amino acids as glucose precursors. Diets were based on grass silage of restricted fermentation and barley‐based supplements because it has been suggested that these diets might provide insufficient glucose precursors to meet the needs of lactose synthesis. The silages used in the experiments were of similar lactic acid contents [62 and 63 g kg^–1 dry matter (DM)] but of different water‐soluble carbohydrate (WSC) contents (206 and 20 g kg^–1 DM in Experiments 1 and 2 respectively). In Experiment 1, four dairy cows were given the following treatments in a 4 × 4 Latin square arrangement with periods of 10 d: (1) basal diet (Basal), (2) Basal plus jugular infusion of 182 g d^–1 of amino acids simulating casein (TAA), (3) Basal plus 101 g d^–1 of essential amino acids (EAA), being the essential amino acid component of the TAA treatment and (4) Basal plus 101 g d^–1 of essential amino acids plus 50 g d^–1 of glucose (EAA + G), being the glucose equivalent of the non‐essential amino acid component of treatment TAA. All infusions increased (P < 0·05) the concentration of milk protein compared with Basal but only for TAA was the increase in the yield of milk protein statistically significant (P < 0·05), amounting to 68 g d^–1. Both TAA and EAA reduced (P < 0·05) the concentration of milk fat. There was no difference between EAA and EAA + G treatments. In Experiment 2, five dairy cows were given the following treatments in a 5 × 5 Latin square design with periods of 7 d: (1) basal diet (Basal), (2) Basal plus 182 g d^–1 of amino acids simulating casein (TAA), (3) Basal plus 182 g d^–1 of non‐essential amino acids as in casein (NEAA), (4) Basal plus 100 g d^–1 of glucose (G100) and (5) basal plus 230 g d^–1 of glucose (G230). G100 supplied the glucose equivalent of NEAA whereas G230 supplied the caloric equivalent of NEAA. Again, only for TAA was the increase in yield of milk protein statistically significant (P < 0·05), amounting to 83 g d^–1. Neither glucose treatment caused any statistically significant (P > 0·05) effect on the yield of milk protein nor the yield of milk lactose. It is concluded that, in both experiments, the primary nutritional limitation on milk protein output was the supply of amino acids as precursors of milk protein, there being no evidence to support a primary limitation due to glucose supply.     

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 effect of frequency of harvesting grass for silage on the intake and performance of beef cattle

Two randomized-block experiments were conducted to examine the effects of frequency of harvesting grass for silage on the intake and performance of beef cattle. In both experiments swards of S24 perennial ryegrass were harvested at 63-, 49- and 38-d intervals throughout the growing season. Grass harvested before and after 10 July was ensiled separately and termed spring and autumn silage respectively. In Experiment 1 the silages were offered ad libitum either unsupplemented or supplemented with 2 kg barley per head daily to eighty-four Hereford-cross weaned, single-suckled steer calves of mean initial live weight 284 kg, in a 3 × 2 × 2 factorial design. Silage dry matter (DM) intakes and liveweight gains for the silages harvested at 63-, 49- and 38-d intervals were 4.80, 0.72; 4.49,0.76; and 4.62,0.78 kg d⁻¹ for the spring silages and 4.69, 0.67; 4.59, 0.85; and 4.55,0.86 kg d⁻¹ for the autumn silages respectively. There was no significant interaction between frequency of harvesting and concentrate supplementation. In Experiment 2 the silages were offered ad libitum and unsupplemented to forty-two Hereford-cross weaned, single-suckled steer calves of mean initial live weight 240 kg, and forty-two Hereford-cross store cattle of mean initial live weight 356 kg, in a 3 × 2 × 2 factorial design. Silage DM intakes and liveweight gains for the silages harvested at 63-, 49- and 38-d intervals were 4.94,0.49; 5.69,0.80; and 619,0.93 kg d⁻¹ for the spring silages and 5.50, 0.61; 5.57, 0.72; and 505, 0.65 kg d⁻¹ for the autumn silages respectively. There were no significant interactions between frequency of harvesting and type of animal. It is concluded that a cutting interval of 49 d commencing on 21 May is likely to be optimum for this type of sward except under exceptional weather conditions.     

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.     

Grass silage as a basic feed for store lambs. 2. Effect of harvesting system and chop length of grass silage on silage intake and performance of store lambs

A perennial ryegrass sward was cut at a leafy stage of growth and harvested with different harvesters to produce silages differing in chop length to evaluate the effect of silage chop length on silage intake and on the performance of store Iambs when silage was fed as the sole diet. The silage was harvested in late May either as long silage (L), single-chopped (S). double-chopped (D). long precision-chopped (LP) or medium precision-chopped (MP) silage with (he appropriate machinery. The silages were treated with formic acid at 2.5 1 t^?1. were well preserved (pH 3.7–3.8) and were of high dry-matter digestibility [749–810 g DMD kg^?1 dry-matter (DM)]. The silages were fed ad libitum as the sole diet to Suffolk crossbred store lambs over a period of 11 weeks. Silage intake and lamb performance progressively increased as silage chop length declined from 32.4 cm (L) to 6.8 cm (MP). Silage intakes were 572, 661, 750, 893 and 1129 (± 21) g DM d^?1 for silages L, S, D, LP and MP respectively. The corresponding daily liveweight gains were -3, 40, 53, 85 and 151 (± 7.6) g d^?l. Similar increases in empty body weight gain and carcass weight gain were obtained as silage chop length declined. Rumen retention time (RRT), estimated from the rumen contents of the lambs at slaughter and their silage intake in the week before slaughter, was much shorter for silages LP and MP compared with silages L or S. Silage intake was negatively related to RRT(b= -24.5 ± 6.1 gDM h^?l RRT). The results of this study showed that high intakes of grass silage and liveweight gains were achieved when grass was cut at a leafy stage of growth and harvested with a precision-chop harvester set to produce a moderate chop length (7 cm). The feeding of long or flail-chopped silages resulted in lower intakes and lower liveweight gains.     

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.     

Comparison of lucerne silage and ventilated hay in maize silage-based rations for dairy cows for the production of milk destined for Grana cheese

Three experiments were carried out to study the effects of feeding lucerne silage (wilted to give different dry-matter (DM) contents) and ventilated hay to dairy cows on milk production, milk quality, milk-renneting properties, clostridial spore content and the quality of cheese prepared from the milk. The lucerne, cut at vegetative or early-bud stages of maturity, was harvested from alternate windrows and conserved as silage or artificially dried hay. The lucerne was wilted until it reached different DM contents of 550, 360 and 432 g kg^–1 in the three experiments, harvested, chopped with a self-loading forage wagon and ensiled in low and narrow clamps made up of transferable prefabricated walls. The organic acid content, pH, yeast and mould counts of the lucerne silage suggested that there was no aerobic deterioration. In each experiment, fifty Italian Friesian lactating cows were divided into two groups and fed two maize silage-based rations for 6 weeks, which only differed in the lucerne forage [silage (S) vs. ventilated hay (H)], in a cross-over experimental design. The lucerne in the rations represented 35%, 23% and 24% of the DM of the rations for the three experiments. The microbiological profiles of the ration were influenced more by the maize silage than by the lucerne silage. Individual daily DM intakes were similar for the two treatments in Experiments 1 and 3 (on average 18·7 kg in Experiment 1 and 20·3 kg in Experiment 3) and slightly lower for S cows in comparison to H cows in Experiment 2 (18·0 vs. 19·0 kg). Milk yields of S and H cows were 21·0 and 20·8, 20·0 and 20·6 (P < 0·01), and 28·4 and 27·9 kg d^–1 in Experiments 1, 2 and 3 respectively. Milk composition was similar for all the experiments for the two treatments, except that the protein content was lower and the fat content was higher in the silage treatment than in the hay. The renneting properties and microbiology of the milk were not influenced by the introduction of lucerne silage into the rations, although the season in which it was consumed had a greater effect on the microbiological content, in terms of standard bacterial counts, proteolytic, coli and lactic acid bacteria, and clostridia spores. The clostridial spore counts were always very low (< 400 per litre), thus fulfilling the requirements for top-quality milk for Grana cheese production. In the third experiment, the quality of Grana Padano cheese produced was examined, and no differences between treatments were observed after 12 months of maturation. These results show that lucerne silage can be included in the ration of dairy cows instead of ventilated lucerne hay, which is considered to be the top-quality hay available for the production of milk destined for Grana cheese, without any negative effects on milk and cheese quality.     

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

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

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.     

The effects of the inclusion of either maize silage, fermented whole crop wheat or ure-treated whole crop wheat in a diet based on a high-quality grass silage on the performance of dairy cows

Sixteen multiparous Holstein/Friesian cows were used to examine the effect on food intake and milk production of replacing 40% of the dry matter (DM) of first cut perennial ryegrass silage (G) with either maize silage (M), fermented (F) or urea-treated (U) wheat whole crop silage. In addition to the forage mixtures, the animals received 5.25 kg DM d ^?1 of a standard concentrate and 1.75 kg DM d ^?1 of soya bean meal. The experiment consisted of four periods, each of 4 weeks duration, in a Latin square design. The grass silage used was of high quality with an estimated metabolizable energy (ME) content of 11.4 MJ kg ^?1 DM and in vitro digestibility of 748 g kg ^?1 DM. DM intake was significantly increased (s.e.d. = 0.364, P < 0.01) with the inclusion of M, F and U. The resulting total DM intakes were 17.6, 18.4, 19.2 and 20.1 kg d ^?1 for treatments G, M, F and U respectively. None of the animal production variables was significantly affected by the treatments. Milk yield was 27.4, 26.4, 27.1 and 26.9 kg d ^?1 for treatments G, M, F and U respectively. Milk fat content was 48.9, 46.9, 49.0 and 48.1 g kg ^?1, and milk protein content was 34.1, 33.6, 34.0 and 34.3 g kg ^?1 for treatments G, M, F and U respectively. The results show that partly (40%) replacing a high-quality grass silage with forage maize, fermented whole crop wheat or urea-treated whole crop wheat will increase DM intake in dairy cows but is not accompanied by an increase in animal performance and therefore will result in decreased efficiency of forage DM utilization.     

Effect of offering silage during housing at night on the performance of grazing dairy cows and on labour requirements

In the UK, dairy cows are increasingly housed at night throughout the grazing season. However, there is limited information on cow performance and the impact on labour requirements when a forage supplement is offered during housing at night throughout the entire grazing season. The effects of housing at night were studied in two experiments, in which two treatments were compared. On treatment part‐grazing (PG), dairy cows were given access to grazing by day and were offered grass silage while housed at night, and, on treatment continuous grazing (CG), dairy cows were given access to grazing both by day and by night. Experiments 1 (138‐d duration) and 2 (127‐d duration) involved sixty (primiparous) and seventy‐six (primiparous and multiparous) Holstein‐Friesian dairy cows respectively. Concentrates were offered during milking at 4·0 and 3·0 kg per cow per day in Experiments 1 and 2 respectively. In Experiment 1, total milk output was significantly higher with treatment PG than treatment CG (P < 0·01) while the reverse occurred in Experiment 2 (P < 0·001). Milk protein concentration was significantly higher with treatment CG in Experiments 1 and 2 (P < 0·001). Cows on treatment CG in Experiment 2 had significantly higher body condition scores and live weights at the end of experiment than those on treatment PG (P < 0·05). Weekly labour requirements were calculated to be proportionally 0·04 lower on treatment PG than on treatment CG. When offered silage during housing at night, the response of grazing dairy cows was largely determined by the grazing conditions encountered and the quality of the forage offered.     

Effect of restriction of silage intake and the provision of an alternative forage on the performance of dairy cows

In three experiments the effects of restricting the silage ration of dairy cows and of offering alternative forages as buffer feeds were investigated.
In the first experiment of changeover design with 3-week periods, restricting the intake of low-quality silage to 0.62 of ad libitum had no significant effect on milk yield in spite of the large energy deficit. Offering high-quality hay as a buffer feed increased total DM intake and milk production of cows receiving either restricted or ad libitum silage.
In the second experiment of similar design, restricting the DM intake of high-quality silage to 0·58 of ad libitum significantly reduced milk yield and was associated with a large negative energy balance. Offering straw or ammonia-treated straw with the restricted silage diet did not restore milk production to the level achieved with ad libitum silage but these supplements slightly reduced the energy deficit of the cows. In the third experiment of continuous design lasting 7 weeks, restricting the silage ration to 0.85 of ad libitum had no significant effect on milk production. Offering a strawmix based on straw, barley, molasses and soya with the restricted silage ration restored total DM intake to the ad libitum silage level.
In all three experiments milk protein content was reduced by restricting the silage ration and partially restored by offering alternative forages. There were no significant effects on milk fat content and milk lactose content was only reduced by the severest restriction in Experiment 2. It is concluded that short-term minor restrictions of silage intake can be partly sustained by body fat mobilization but more severe restrictions will result in loss of milk yield. Good-quality hay and a strawmix were of benefit in restoring DM and metabolizable energy intakes, whereas straw and ammonia-treated straw were of little value.     

The digestibility of diets containing processed dried lucerne by sheep and cows

A series of trials was conducted to compare the digestibility of organic matter in castrated male sheep and non-lactating and lactating cows given diets containing lucerne cobs. Similar digestibility coefficients were determined when sheep and non-lactating cows were given hay and lucerne cobs, but lactating cows digested diets of hay, lucerne cobs and concentrates less well than sheep. It is concluded that if sheep are used in digestibility trials with diets containing processed lucerne and concentrates intended for milking cows, appreciable errors of prediction of digestibility of organic matter may arise.     

Mixing whole-crop pea–oat silage and grass–clover silage: positive effects on intake and milk production of dairy cows

Forty‐eight high‐yielding dairy cows of the Swedish Red breed were used to examine the effects of providing pea–oat silage (P), grass–clover silage (G) and a 0·50:0·50 mixture of the silages (M) ad libitum in diets with two concentrate levels (7 or 10 kg d^?1). A 9‐week experiment, including a 2‐week pre‐experimental period in which the cows were all fed the same diet, and an in vivo apparent digestibility study were conducted comparing the six dietary treatments (M7, M10, P7, P10, G7, G10). Intake and digestibility of the diets and milk production and live weight of the cows were measured. The G silage [11·3 MJ ME kg^?1 dry matter (DM)] was first‐cut grass herbage wilted for 24 h prior to addition of an additive, containing formic acid, propionic acid and ammonia, at 4 L t^?1 fresh matter (FM). The P forage was cut when the peas were at pod fill and ensiled directly with 6 L t^?1 FM of the same additive. The main hypothesis tested, that cows fed the M silage would produce more milk than the cows fed either the P or the G silages, was confirmed. The cows fed the M7 dietary treatment had similar milk yield and milk composition to cows offered the M10, G10 and P10 dietary treatments, and cows offered the G7 and P7 dietary treatments had lower milk and milk protein yields. This suggested that a mixed ration of pea–oat bi‐crop and grass–clover silage has a concentrate‐sparing effect, and that the use of pea–oat bi‐crop and grass–clover silage as a mixed ration for high‐yielding dairy cows can be recommended.     

Effects of grass silage feed value on feed intake and performance of pregnant and lactating ewes and their lambs

Effects of grass silage feed value on intake, dietary sorting, body condition (BC) and body weight (BW) of pregnant and lactating ewes and on liveweight gain (LWG) of their suckling lambs were evaluated. Twin‐bearing ewes were fed ad libitum grass silage of (i) high feed value (HFV), (ii) medium feed value (MFV) and (iii) low feed value (LFV), plus 0·8 kg concentrate in late pregnancy and lactation. The HFV, MFV and LFV silages contained 11·7, 10·8 and 9·3 MJ metabolizable energy (ME) kg^?1 DM respectively. The HFV resulted in 8·2 and 15·2 MJ greater ME intake in pregnancy and 14·7 and 21·0 MJ greater ME intake from silage in lactation than MFV and LFV respectively (P < 0·01). Ewes fed the MFV and LFV silages sorted for more digestible particles during eating (P < 0·10). The HFV gave no loss in BC, whereas ewes fed MFV and LFV lost 0·7 and 0·8 units of BC, respectively, during lactation (P < 0·10). There were similar trends in BW. The nursing HFV lambs had 73 g higher daily LWG than the LFV lambs (P < 0·01). In conclusion, the HFV increased the ME intake of pregnant and lactating ewes, resulting in improved BC and BW of lactating ewes and LWG of suckling lambs compared to MFV and LFV.