Effects of conservation method and access time on silage intake and milk production in dairy cows

The effects of the time of access to feed (8 h or 24 h) with silage-based rations (unwilted or wilted silage) were studied for two years. In each year the experiment comprised 52 individually fed cows in a 2 × 2 factorial design and covered weeks 1-20 of the lactation. The cows were offered silage ad libitum , 1 kg of hay per day, and concentrate according to the predicted energy-corrected milk (ECM) yield.
Increasing the access time from 8 h to 24 h increased the total intake of dry matter (DM) and metabolizable energy (ME) by 6%. This resulted in increased yield of ECM by 5%. The eating rate of forage was significantly increased by restricted time of access. Wilting had no significant effect on total feed intake or milk yield. The importance of providing a sufficient length of time during which the cows have access to feed was confirmed. It was concluded that 8 h d⁻¹ of access to silage-based rations is not enough in early lactation.     

Silage and milk production: comparisons between hays of different digestibilities as silage supplements

In three separate feeding experiments using a total of thirty individually-housed Ayrshire cows three silages made from perennial ryegrass were given ad libitum together with supplements of four different hays in the long form. The in vitro D-values of the silages ranged from 0·298 to 0·283, and the hays from 0·280 to 0·200. The daily intake of hay DM varied from 0·2 to 4·2 kg per cow and was given either without or with a daily maximum of 2·2 kg concentrate DM containing 379–527 g CP per kg DM. On average, 1 kg hay DM decreased silage intake by 0·24 kg DM with a range of 0·21–1·20 kg. The hay supplements had only small and non-significant effects on total DM intake, milk yield and milk composition, but increased the daily intake of drinking water. In three behavioural studies, the eating and ruminating times expressed as min per kg DM did not differ significantly between the various supplement treatments. It is concluded that hay has only a marginal value as a supplement for grass silage, although the hay could serve as a useful 'buffer' feed if the amount of silage was limited.     

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

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

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

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

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.     

Effect of three forages and two forage allowances offered to pregnant dry dairy cows in winter on periparturient performance and milk yield in early lactation

Sixty multiparous, Holstein–Friesian pregnant dry dairy cows were allocated to three forage treatments ( n  = 20; fodder beet, kale or grass silage) at two feeding allowances ( n  = 30; high and low) for 70 (s.e. of mean, 16) d before parturition. Cows offered the high feeding allowance were offered 9 kg of dry matter (DM) of kale or fodder beet grazed in situ plus 5 kg DM of baled grass silage daily or clamp grass silage ad libitum offered indoors. Cows offered the low feeding allowance were offered 6 kg DM of kale or fodder beet grazed in situ plus 3·5 kg DM baled grass silage daily, or 9·5 kg DM of clamp grass silage daily offered indoors. After calving, all cows received a daily allowance of 14 kg DM perennial ryegrass herbage at pasture plus 4 kg concentrate cow⁻¹ for the first 35 d of lactation. Cows offered grass silage had a greater increase in body condition score pre-partum compared to those offered kale or fodder beet. Cows offered fodder beet pre-partum had a greater milk solid and solids-corrected milk yield in the first 35 d of lactation than those offered kale and grass silage pre-partum. Offering fodder beet and kale pre-partum increased plasma non-esterified fatty acid concentrations pre-partum relative to offering grass silage. Offering kale pre-partum resulted in higher insulin-like growth factor-1 concentration post-partum but lower plasma copper concentration pre-partum and at calving than kale or grass silage. Offering the higher forage allowance pre-partum resulted in a higher plasma calcium concentration at calving and higher plasma non-esterified fatty acid concentration post-partum.     

The effect of adding surface water to herbage on its digestion by ruminants

In two experiments the effects of adding surface water to herbage on its digestion by ruminants were examined. In experiment 1, with sheep, adding water to silage reduced DM intake and the diet DM digestibility. Offering a high DM alternative forage, hay, increased DM digestibility with the wetted silage, but tended to decrease it with the dry silage. More hay was eaten with the wetted than dry silage. In experiment 2, with steers, adding water to fresh herbage reduced DM intake but had no effect on rumen pH or ammonia levels. Adding water to the herbage reduced the rate of DM disappearance from nylon bags placed in the rumen and the proportion of rumen liquor particles of low specific gravity. The proportion of very short and very long particles in the rumen liquor was also reduced by adding water to the herbage.     

The use of conserved forage as a supplement for grazing dairy cows

The difficulty in matching the herbage requirements of grazing dairy cows to herbage production, due mainly to the unpredictability of the latter., causes stocking rates to be too low for maximum per hectare production and, thus, cows to be underfed at certain times in the grazing season. Conserved forage may be used as a supplement for grazing dairy cows in order to reduce variation in forage intake by the cow, to allow pasture stocking rates to be increased and to increase the efficiency of land use. The effect of offering conserved forage with herbage on intakes and production is reviewed in comparison to both ad libitum and restricted herbage. Total nutrient intakes and milk fat + protein yields are reduced for cows offered herbage and supplementary forage compared with cows offered ad libitum herbage, but increased compared with cows offered a restricted herbage level. Increasing pasture stocking rates may allow increases in utilized metabolizable energy levels from grassland but further research is needed in this area. Both grass and maize silage supplements offer potential for increasing the efficiency of land use, but in the case of grass silage this is only achieved in the best management practices.     

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

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

Supplementary forage for grazing sheep. 2. Effects on weaned lambs

In two experiments weaned entire ram lambs were offered either pasture alone or pasture plus ad libitum conserved forage for 7–12 weeks during the finishing period. Herbage height was maintained at 3·2 cm on both treatments by manipulation of stocking rate in the twenty-four plots (twelve per treatment) used for the experiment. In experiment 1 silage, which was of lower metabolizable energy (ME) and crude protein (CP) content than the grazed herbage, was consumed at an average of 194 g DM head⁻¹ d⁻¹, providing approximately 40% of total DM intake requirements. In experiment 2 a strawmix, containing (g k g ⁻¹ freshweight) 450 g barley straw, 300 g concentrate and 250 g molasses and again with a lower ME and CP content than the grazed herbage, was consumed at an average of 57 g DM head⁻¹ d⁻¹, providing approximately 11% of total DM intake requirements. In both experiments stocking rate was increased by 20–25% by providing forage, but lamb growth rate was not affected.     

Supplementary feeding of forage to grazing dairy cows, 3. The effect of three daytime stocking rates on the performance of cows offered grass silage overnight

Over a 24-week period, three groups of dairy cows were continuously stocked at 8, 10 or 12 cows ha^-1 between morning and afternoon milkings, and overnight were housed and offered grass silage ad libitum. Due to a prolonged drought, sward heights only averaged 4·1 cm.
The increase in daytime stocking rate led to a decline in herbage intake, and increases in silage intake. At the highest stocking rate (12 cows ha^-1), the silage intake failed to compensate for the reduced herbage intake. Consequently the total dry matter and estimated metabolizable energy intakes were lower than for the 8 and 10 cows ha^-1 treatments. Milk yields and milk composition were not significantly affected by treatment but the 12 cows ha^-1 stocking rate gave the lowest milk and milk solids yields.
The utilized metabolizable energy (UME) on the grazed swards was greatest for the 10 cows ha^-1 treatment. The sward cut to provide the silage had a UME level (GJ ha^-1) 32% greater on average than the grazed swards during the same growth period. The total areas utilized for grazing and silage production for 8, 10 and 12 cows ha^-1 were 0·240, 0·224 and 0·215 ha respectively. Fat and protein yields per unit area were greatest for the 10 cows ha^-1 group.     

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.     

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

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

Supplementary feeding of forage to grazing dairy cows

For three 8-week periods of the grazing season 48 spring-calving cows were continuously stocked at either a high or a low rate (average 4.9 and 4.3 cows ha⁻¹ respectively) which declined through the season. Within each stocking rate group half the cows were allowed access to hay for 45 min after morning milking; the other half received no hay.
Total dry matter (DM) intakes were increased by offering hay, and intakes of hay were greater at the high stocking rate and during prolonged periods of inclement weather. However, there were times when, because of low herbage height and adverse weather, offering hay once daily could not prevent a decline in total DM intake. Grazing time was reduced and ruminating time increased by offering hay, but the rate of biting at pasture was unaffected. Hay DM was eaten at twice the rate of intake of herbage DM.
Offering hay increased milk yield in early season and liveweight gain in late season. The benefits of offering hay were greatest for the higher yielding cows. There were no significant effects on milk composition.
Stocking rate had only small effects on herbage height, but stocking at the higher rate tended to reduce herbage DM intake and reduced live-weight gain in late season. Levels of utilized metabolizable energy from grazed herbage were high (average 106 GJ ha⁻¹) but were reduced by feeding hay and stocking at the lower rate.     

The effects of feeding fodder beet with two levels of concentrate allocation to dairy cattle

Twelve cows were used in a cyclic changeover design experiment to examine the effects of feeding fodder beet (variety Kyros) at three levels (0, 2 and 4 kg dry matter (DM) d^?1) with two levels of concentrate feeding (4 and 8 kg DM^?1). Silage was offered ad libitum. At the start of the experiment the mean number of days after calving was 46 and the mean live weight 516 kg. The experiment consisted of four 3-week periods with intake and performance measurements during the last week of each period. An in vitro analysis of the feeds for the silage, fodder beet and concentrate respectively was: DM (g kg-^?1) 189, 163, 860; crude protein (g kg DM^?1) 143,76,201; metabolizable energy (MJ kg DM^?1) 104, 133, 13–5. Silage DM intake decreased but total DM intake increased when fodder beet was fed. The DM intakes (kg d^?1) for treatments (fodder beet/ concentrate) 0/4, 2/4, 4/4, 0/8, 2/8, 4/8 respectively were: silage DM 91, 79, 78, 83, 70 and 68 (s.e.d. =0.31); and total DM 130, 138, 156, 162, 166, 183 (s.e.d. = 0.36). Feeding fodder beet had no significant effects on milk yield or milk composition, but there was a significant increase in milk protein yield when fodder beet was included in the ration. There were no significant interactions between level of fodder beet feeding and concentrate level. Increasing the level of concentrate feeding led to a highly significant increase in milk yield, milk protein content and yield of milk constituents. The yields for treatments 0/4, 2/4,4/4,0/8, 2/8,4/8 respectively were: milk yield (kg d^?1) 206, 204,21 8, 241,235, 244 (s.e.d. = 0–58); fat yield (g d^?1) 827, 793, 885, 954, 936, 954 (s.e.d. = 394); and protein yield (g d^?1) 622, 628, 679, 774, 777, 814 (s.e.d. = 179). There were no significant differences in milk yield and milk composition when fodder beet was included in the diet which may have been due to the low crude protein content of the diet.     

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

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

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.     

Effect of early turnout to grass in spring on dairy cow performance

This experiment examined the effects of grazing severity and degree of silage restriction during early turnout of dairy cows to pasture in spring on animal performance. Forty late‐winter‐calving Holstein Friesian dairy cows were allocated to one of five treatments between 7 March and 17 April 1997. The treatments involved early turnout of cows to grass for 2 h per day at two residual sward heights and two silage allowances, plus a control treatment, in a randomized block design. Dairy cows on the control treatment remained indoors throughout the experiment and were offered grass silage ad libitum. Dairy cows on all treatments were also offered 6 kg d^–1 of a concentrate on a flat‐rate basis, split equally between the morning and afternoon milkings. Offering cows access to pasture in early spring for 2 h per day resulted in increases in both milk (P < 0·001) and protein yield (P < 0·01). On average, over all grazing treatments, cows produced an additional 2·6 kg milk per day compared with the control treatment (28·5 vs. 25·9 kg d^–1, s.e.m. 0·43). Furthermore, these increases in milk yield were obtained even when silage was restricted indoors (28·4 vs. 25·9 kg d^–1) and cows grazed down to a residual sward height of 40 mm (28·1 vs. 25·9 kg d^–1). Protein yield was higher (P < 0·01) with dairy cows grazing pasture compared with cows indoors (848 vs. 707 g d^–1, s.e.m. 28·9). Silage intake was significantly (P < 0·001) reduced when cows were turned out to pasture. In conclusion, early turnout of dairy cows to pasture in spring for 2 h per day reduced silage intake and increased milk yield and protein yield relative to those fully housed and offered grass silage with a low level of concentrates.     

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

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

Modelling feed intake and milk yield responses to different grass ley harvesting strategies

A meta‐analysis of feeding trials using grass silages was conducted to predict production responses for dairy cows fed grass silage. They were divided into two subsets: 69 diets from 11 studies were used for comparison of silages made from primary growth and regrowth grass (harvesting subset), and another 157 diets from 24 studies were used for comparison of digestibility influenced by the maturity of grass ensiled (D‐value, digestible organic matter in dry matter) (maturity subset). The minimum prerequisite for an experiment to be included in the data set was that milk production, feed intake, silage characteristics and concentrate ingredients were reported. Both subsets were analysed using the mixed model procedures of SAS. The mean response in dry‐matter intake (DMI) and silage DMI to improved silage D‐value was 0.0175 and 0.0161 kg per unit D‐value (g/kg DM) respectively. The average increase in milk and energy‐corrected milk yield was 0.30 and 0.37 kg per 10‐unit increase in silage D‐value respectively. Milk protein concentration increased, and fat concentration tended to increase with enhanced silage D‐value. Each 10‐unit increase in D‐value reduced milk yield by 0.092 kg at a given dietary metabolizable energy intake (MEI), suggesting that the ME concentration of high D‐value silages was overestimated. Cows fed regrowth silage produced 0.55 kg/day more energy‐corrected milk than those fed primary growth silage at a given dietary MEI. The prediction models can be used to improve ration formulation systems or incorporated into economic models for optimizing milk production in various farming systems.