Concentrate supplementation of grazing dairy cows. 2. Effect of concentrate composition on herbage intake and milk production

The effect of feeding either traditional concentrates containing starch or high quality fibrous concentrates on the performance of grazing dairy cows was examined in a trial in which cows were given concentrates with either 350 g starch and sugars (kg dry matter (DM))^-1 (high-starch) or 100 g starch and sugars (kg DM)^-1 (high-fibre). The swards used consisted predominantly of perennial ryegrass and were usually aftermaths following cutting. Each area was grazed for 3 or 4 d at each grazing and a two-machine sward-cutting technique was used for estimating herbage intake.
The effect of concentrate composition on the herbage intake of grazing cows at a high daily herbage allowance of 28 kg OM above 4 cm cutting height was investigated in 1983 and 1984. With 54 kg OM d^-1 of high-starch concentrates the mean herbage intake was 11·5 kg OM d^-1 per cow while cows fed 5.3 kg d^-1 of high-fibre concentrates consumed on average 12–6 kg OM d^-1. The mean substitution rate of herbage by concentrates was reduced from 0·45 kg herbage OM (kg concentrate OM)^-1 with the high-starch concentrate to 0·21 with the high-fibre concentrates.
The effect of the treatments on milk production was studied in 1984. The cows consumed 5·5 kg OM d^-1 as concentrates and grazed at a lower herbage allowance of 19 kg OM above 4 cm cutting height. With high-fibre concentrates milk production and 4% fat-corrected milk production were 13 and 1·8 kg d^-1, respectively, higher than with the high-starch treatment. The daily live weight gain with the high-starch concentrates was 0·17 kg per cow more than with the high-fibre concentrates.     

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.     

Grass height as an indicator for supplementary feeding of continuously stocked dairy cows

Three groups of cows were continuously stocked on pasture and offered supplementary concentrates according to the herbage height measured weekly with a grass disc. Concentrates were offered when the mean herbage height fell below 9 cm for treatment A, 7 cm for treatment B and 5 cm for treatment C at a rate of 1 kg d^-1 for each 0·2-cm decline below these threshold levels. If the herbage height declined by more than 1·2 cm (8 kg concentrates d^-1) hay was offered in addition ad libitum. The stocking rates for all three treatments were 5·2, 3·2 and 3·2 cows ha^-1 for three successive 8-week periods. For treatments A, B and C the mean concentrate DM intakes were 3·2, 1·2 and 1·2 kg d^-1 (treatment A also received 0·2 kg hay DM d^-1), and the mean daily milk yields were 17·2, 16·2 and 15·2 kg respectively. The increasing level of supplementary feeding from treatment C to A also resulted in an increase in liveweight and body condition score change, and a reduction in milk fat.     

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

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

Utilization of silage nitrogen in sheep and cows: amino acid composition of duodenal digesta and rumen microbes

Two experiments are reported. In the first experiment the amino acid compositions of rumen bacteria and protozoa isolated from sheep given a diet of grass silage were compared with those taken from sheep given a diet of hay and barley; four sheep were assigned to each diet. There were no significant differences (P<0·05) between diets in the amino acid compositions of the microbial fractions and bacterial contents of α-ɛ-diaminopimelic acid were also similar for both diets.
In the second experiment the digestion of a grass silage and barley diet (65:35; 135 g CP (kg DM)^-1) was studied using four non-lactating Ayrshire cows fitted with cannulae in the rumen and in the proximal duodenum. The mean N intake was 154 g d^-1 and the corresponding duodenal flow was 126 ± 10 g d^-1 indicating that 0·21±0·07 of the N intake was absorbed between the mouth and the duodenum. The mean rumen NH₃-N concentration was high, 297 g litre^-1, and the mean rate of microbial protein synthesis in the rumen was low, 17 g microbial N (kg OM apparently digested in the rumen)^-1. There was a low content of bacterial N in the non-ammonia N at the duodenum (mean proportion 0·52±005) and low concentrations of methionine and lysine in the duodenal digesta protein. The results are discussed in relation to previously published data on the digestion of silage diets in sheep and to the utilization of silage diets for milk production in the cow.
It is concluded that with silage diets the supply of methionine and lysine to the duodenum is likely to be low because of the low rates of microbial protein synthesis in the rumen and that in cows those two amino acids may be limiting for milk production.     

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.     

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

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

The effect of offering a brewers grains/treated straw supplement to grazing dairy cows

In a two-year study, set stocked dairy cows were offered a mixture of brewers grains and sodium hydroxide-treated straw (1:1 on a dry matter basis)for 1 h daily. The experiments lasted for 20 and 19 weeks, mean supplementary (buffer) feed dry matter intakes were 3·0 and 3·4 kg d^-1 and mean sward heights (rising plate meter) were 4·9 and 4·7 cm in 1988 and 1989 respectively. The control group received no supplementation. The buffer feed significantly increased milk yield (26·3 vs 24·6 kg d^-1 and 28·6 vs 26·3kg d^-1 in 1988 and 1989 respectively), increased liveweight gain (0·27 vs 0·13 kg d^-1 and 0·27 vs 0·17 kg d^-1) and increased effective stocking rate (5·17 vs 4·69 cows ha^-1and 5·10 vs 4·53 cows ha^-1). There were no significant effects on milk composition. The greatest responses in milk production were found in the late grazing season.     

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).     

Influence of growth stage and season on the energy value of fresh herbage. 2. Relationships between digestibility and metabolizable energy content and various laboratory measurements

This paper gives details of a study which has examined the effect of herbage growth type and season on the relationships of digestible organic matter in the dry matter (DOMD) and metabolizable energy (ME) contents measured in vivo to various laboratory measurements including three in vitro estimates of DOMD based on rumen fluid pepsin (RFP), pepsin cellulase (PC) or neutral detergent cellulase (NCD). Seventy herbages harvested over two years and comprising 32 spring primary growths, 14 summer regrowths and 24 autumn growths were used.
For DOMD in vivo , significantly different regression relationships were required for spring and autumn-harvested herbage. Equations based on PC were:
Spring herbage: DOMD (g kg^-1 DM) = 436 + 0·501 PC (g kg^-1 DM) ²= 76·7%; r.s.d. = 25·4
Autumn herbage: DOMD (g kg^-1 DM) = 594 + 0·195 PC (g kg^-1 DM) ²= 15·5%; r.s.d. = 23·1
For autumn herbages there were no significant relationships with ME. As with DOMD in vivo the PC method was shown to provide the most accurate relationship with ME concentration of spring herbage. The relationship was:
ME (MJ kg^-1 DM) = 6·16 + 0·0094 PC (g kg^-1 DM) ²= 69·8%; r.s.d. = 0·57
For both DOMD and ME the relationships for spring herbage based on PC were the only ones which did not differ significantly from those of an earlier study.
It is concluded that even where significant relationships for summer and autumn herbages were developed, the predictors accounted for substantially less of the variability than in spring herbages. This appeared to be largely due to reduced range in the DOMD and ME content in summer and autumn herbages.     

Effects of formic acid on silage fermentation, digestibility, intake and performance of young cattle

Data from twenty-two comparisons carried out at ADAS Experimental Husbandary Farms are used to compare untreated and formic acid-treated silages. Additive treatment led to an improved fermentation in some crops, particularly those of low DM concentration (<262 g kg^-1). Where this occurred there were associated benefits in silage digestibility (+0·234 units), intake (+16%) and the growth rate of young cattle (+0·28 kg d^-1). Where the fermentation of the untreated silage was good, both digestibility and animal performance associated with treated and untreated silages were similar. It is suggested that the justification for using formic acid in a commercial situation is thus restricted to occasions where the untreated crop would be liable to develop a clostridial fermentation. These may be when crops contain less than 35 g water-soluble carbohydrate kg^-1.     

The chemical composition and nutritive value of grass silages prepared with no additive or with the application of additives containing either Lactobacillus plantarum or formic acid

A mixture of perennial and hybrid ryegrasses(234 g DM kg^-1) was forage harvested and ensiled after a 24-h wilt in good ensiling conditions in 2-t capacity silos with no additive application (control) or with the application of either Lactobacillus plantarum , 4 × 10⁶ (g fresh weight of grass)^-1, or of 31 formic acid t^-1. Sufficient 2-kg capacity laboratory silos were also filled with grass to monitor the changes in chemical composition of the ensiled grass with time. In laboratory silos, inoculation with L. plantarum resulted in a more rapid fall in silage pH ( p < 0.001) and a more rapid production of lactic acid ( P < 0.001) than in the control silage. At the end of the storage period (laboratory silos, 80 d; 2-t silos, 200-300 d), the inoculated silos had lower pH ( p ammonia-N (g kg N¹) and acetic acid contents ( p < 0.01) and higher water soluble carbohydrate (WSC), lactic acid (P<00.1) and ethanol ( p < 0.05) contents than the control silage. The formic acid-treated silage had significantly lower contents of ammonia-N (g kg N^-1, p < 0.05), acetic and tactic acids (p<0.01) and higher contents of WSC and ethanol ( p < 0.01) than the control silage. When fed to wether sheep, the digestibilities of DM, organic matter and gross energy were not altered by additive treatment. The digestibility of modified acid-detergent fibre was lower for both the inoculated ( P < 0.01) and formic acid-treated silages ( p < 0.05). However, N retention was improved ( p < 0.05) by both additive treatments. Silage intake was improved ( p < 0.01) by additive treatment from 53.4 (control) to 58.0 (inoculated) and 60.4 (formic acid) g DM (kg live weight^0.75)^-1d^-1.     

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.     

Use of bovine somatotropin for milk production: the effect of time of treatment initiation on milk production of Holstein/Friesian dairy cows placed on a high-forage, low-concentrate feeding system

Sixty multiparous Holstein/Friesian cows were used in a 2 × 2 factorial design trial to determine the effect of the administration of bovine somatotropin (BST), at either 60 or 120 ± 3 d post partum, on milk production. All cows were offered ad libitum a forage mixture containing, on a dry-mailer (DM) basis, grass and maize silage in a 1:1 ratio and 4 kg d⁻¹ fresh weight of concentrate, which contained 115 and 495 g kg⁻¹ DM of neutral detergent fibre (NDF) and crude protein (CP), respectively, and 13–5 MJ kg⁻¹ DM metabolizable energy (ME). BST-treated cows received subcutaneous injections of a prolonged-release formulation of BST (sometribove). Injections were administered into the ischiorectal fossa at 14-d intervals for the remainder of the lactation. This schedule resulted in sixteen and twelve injections cow⁻¹ when treatment w as in it rate d at 60 and 120 + 3 d post partum respectively. This corresponded to treatment periods of 32 and 24 weeks, in which the production responses were measured. When compared with control cows, the administration of BST from 60 and 120 ± 3 d post partum increased mean milk yield by 1–2 and 3.3 kg day⁻¹ respectively, although only the latter milk-yield response was significant ( P <0.001). The administration of BST produced a small nonsignificant increase in DM intake, no effect on milk composition and a small but significant reduction in body condition In conclusion a significant milk-yield response can be obtained from the use of BST in high-forage, low-concentrate feeding systems if forage quality is high and treatment initiation is delayed until mid-lactation. This is illustrated by the fact that the lactation yield increased from 6054 to 6842 kg. and was obtained when using only 1.2 t of concentrate.     

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 potential of an all-grass diet for the late-winter calving dairy cow

In a trial lasting 3 years at Jealott's Hill and 2 years at Ravenscroft Hall, a total of 73 January- March-calving Friesian x Holstein cows and heifers were given a diet consisting almost exclusively of ensiled and grazed ryegrass for an entire lactation to establish the level of milk production which grass alone can support. From calving to turnout in April/May (average duration 87 days), the animals were given high digestibility (DOMD = 678g kg-¹ DM) ryegrass silage ad libitum. After turnout, they grazed ryegrass swards until housing in autumn. Thereafter, the cattle were given ryegrass silage of lower digestibility (DOMD = 600–620 g kg-¹ DM) for the remainder of the lactation and during the dry period.
Mean silage dry matter intakes from calving to turnout were 13–2 kg day-¹ at Jealott's Hill and 11·5 kg day-¹ at Ravenscroft Hall. Average milk yields were 21-1 kg day-¹ for cows and 16-1 kg day-¹ for heifers with 39-2g fat kg-¹, 29-6g protein kg-¹ and 47–9 g lactose kg-¹. Over the complete lactation, average milk yields were 4680 kg and 4006 kg for the cows and heifers, respectively, with 39-4 g fat kg-¹, 31·4 g protein kg-¹ and 46·9 g lactose kg-¹. Animal health and fertility were satisfactory. The results demonstrated the value of high quality grazed and ensiled ryegrass and provided a measure of milk production from grass only.     

Silage and milk production: comparisons between unwilted and wilted grass silages made with different additives

Four grass silages, all made in mid-July from second-harvest perennial ryegrass swards, were compared in a 16-week feeding experiment with twelve Ayrshire cows. Two silages were unwilted and two wilted. All the silages received formic acid ('Add-F') at the rate of 3 litres t^-1 either with formalin at the rate of 1 litre t^-1 or without formalin. The unwilted and wilted silages had mean dry matter (DM) concentrations of 200 and 243 g kg^-1, and in vitro D-values of 0·293 and 0·272 respectively. The silages were offered ad libitum plus 6 kg concentrates per cow per day. The daily intakes of unwilted and wilted silage DM were 10·2 and 9·2 kg per cow respectively on the formic acid treatment, and 10·2 and 9·2 kg on the formic acid + formalin treatment. The mean daily milk yield on the unwilted silage treatments was 19·2 kg per cow which was significantly higher than the yield of 17·2 kg per cow on the wilted silage treatments. The formalin had no significant effect on milk yield. The four silage treatments had small and non-significant effects on milk composition. It is concluded that the unwilted silages, which had excellent fermentation characteristics, were superior to the wilted silages as a feed for dairy cows.     

The influence of sowing date, harvest date and seed rate on the yield of forage peas

A series of preliminary trials is described to assess the potential and some of the cultural requirements of new cultivars of forage peas grown as pure stands in the west of Scotland. Optimum sowing date was late March for harvesting 15 weeks later to leave sufficient of the growing season for a catch crop or the establishment of a grass sward. Yield of dry matter (DM) at harvest was approximately 6 t ha^-1 but DM concentration varied greatly with season. The digestibility of the organic matter was of the order of 0·700 and the crude protein concentration in the DM 170 g kg^-1. DM yield increased with increasing seed rate up to 200 kg ha^-1 the maximum rate tested.     

Effect of supplementation on production by spring-calving dairy cows grazing swards of differing clover content

An experiment was carried out to examine the effect of supplementation on the performance of spring-calving dairy cows grazing swards of differing perennial ryegrass and white clover content. Seventeen heifers and sixty-four Friesian cows in their third to ninth week of lactation were turned out onto one of three pastures with different proportions of perennial ryegrass and white clover. Nine animals on each pasture received either 0, 2 or 4 kg d⁻¹ of a concentrate with a crude protein concentration of 180 g kg⁻¹ dry matter (DM). Prior to grazing, swards contained proportionately 0·01 (L), 0·15 (M) and 0·20 (H) of total DM as clover. During the experiment, grazing pressures were adjusted by movement of buffer fences to maintain compressed sward heights at 6 cm. Samples taken 26 and 68 d after the start of grazing showed little change in the proportion of clover in sward L (< 0·01 and 0·02 respectively), but convergence in the proportion of clover in swards M and L (0·08-0·16 and 0·10-0·15 respectively). Mean daily yields of milk, fat, protein and lactose increased significantly with increased clover content and, even without supplementation, daily yields were 25·4, 0·98, 0·73 and 1·09 kg respectively on sward H. Of the milk components, only protein was significantly increased by increasing sward clover content. The response in milk yield to supplementation was greater on sward L than on swards M and H.     

The herbage intake and performance of set-stocked suckler cows and calves

Groups of eight Hereford × Friesian cows and their South Devon cross calves were set stocked over a 24-week grazing season at 3·23 (low), 3·21 (medium) or 4·24 (high) cows ha^-1 together with their calves. For the first 8 weeks only two-thirds of the total area was grazed. Increasing the stocking rate from low to medium reduced daily milk yield and cow and calf liveweight gains by 1·2, 0·24 and 0·29 kg d^-1 respectively, and from medium to high by 1·2, 0·24 and 0·23 kg d^-1. The main sward factor influencing faecal output and herbage intake was the quantity of organic matter on the pastures but the digestibility of the herbage selected also exerted a significant effect on the intake of cows. Major depressions in the herbage intake of cows occurred once the average sward height fell below 7 cm. Output of calf live weight was 628, 658 and 743 kg ha^-1 for the 3 stocking rates from low to high, and for cows 246, 179 and 30 kg ha^-1. It was concluded that decisions on pasture management should be taken in relation to the cow rather than the calf on set-stocked swards.