Grazing behaviour,intake and performance of dairy ewes with restricted access time to berseem clover (Trifolium alexandrinum L.) pasture

The effects of restricted access time to pasture (2, 4 or 6 h d^?1; 2H, 4H or 6H) on ingestive behaviour and performance were assessed on four occasions per target grazing day (D1, initial day; D4, intermediate day; and D7, final day) in dairy ewes rotationally grazing berseem clover with a 7‐day grazing period and a 21‐day recovery period. A randomized block design with two replicates per treatment was used. All ewes were supplemented daily with 700 g per head of concentrates and 700 g per head of ryegrass‐based hay. Pasture subplot and animal group data were analysed by a factorial model including access time (AT), grazing day (D) and their interaction as fixed factors. Sward height decreased from D1 (P < 0·001) and green leaf mass from D4 (P < 0·001) onwards during the grazing period. Grazing time as a proportion of AT was higher in 2H than in 4H and 6H ewes on D1 and D4 but not on D7 (P < 0·05 for AT × D). Herbage intake rate was higher in 2H than in 4H and 6H ewes (P < 0·001). Herbage and total intakes were higher in 4H and 6H than in 2H ewes (P < 0·001), with herbage intake varying non‐linearly during the grazing period (P < 0·05). Milk yield was higher in 4H and 6H than in 2H ewes (P < 0·01). To conclude, despite the evidence of compensatory behaviour, restricting access time to 2 h d^?1 constrained intake and performance of dairy ewes rotationally grazing berseem clover.     

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

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

The effect of Calluna vulgaris cover on the performance and intake of ewes grazing hill pastures in northern Spain

The effect of the proportion of Calluna vulgaris cover on diet composition, intake and performance of sheep grazing hill vegetation communities in northern Spain is examined. A total of 591 non‐lactating Gallega ewes grazed for five consecutive grazing seasons (June to September) on replicated plots of hill pastures (1700 m.a.s.l.) composed principally of Festuca, Agrostis, Nardus and Calluna spp. but with different proportions of Calluna vulgaris cover, either 0·3 (C_0·3) or 0·7 (C_0·7) of the total area. In 1 year, twenty‐eight ewes suckling single lambs also grazed the plots. The mean stocking density over the 5 years was 8·7 ewes ha^–1. On treatment C_0·3, daily liveweight gains (33 g d^–1) of non‐lactating ewes were significantly (P < 0·001) greater than on treatment C_0·7 (12 g d^–1). Likewise in lactating ewes the difference in mean daily liveweight change was 40 g d^–1 (–5 vs. –45 g d^–1 for C_0·3 and C_0·7 treatments respectively; P < 0·001). Liveweight gains of lambs were only 80–100 g d^–1 from June to August and lambs only maintained live weight during August and September. The effect of lactational status on liveweight changes was not significant. Liveweight gains of non‐lactating ewes increased significantly (P < 0·001) from the first to the last year of the experiment on both treatments. The composition of the diet was significantly affected by treatment (P < 0·001), with a higher proportion of grass species on the C_0·3 treatment and a higher digestibility of the diet in the first half of the grazing season (P < 0·001). The proportion of C. vulgaris in the diet was significantly (P < 0·001) higher on the C_0·7 treatment and increased significantly (P < 0·001) from July to September on both treatments. There were no significant differences in the composition of the diet selected by lactating and non‐lactating ewes. The results demonstrate that on hill vegetation communities, in which the grass components (Festuca rubra, Agrostis capillaris, and Nardus stricta) cover at least 0·3 of the area and on which the preferred grass component (Festuca and Agrostis spp.) is maintained at a sward height of at least 2·5 cm, non‐lactating ewes can increase their live weight and body condition, but this increase is influenced by the proportion and quantity of species of grass in the diet, which is affected in turn by the species of grass available and their nutritive quality. However, ewes suckling lambs were not able to maintain their live weight and body condition except when Calluna cover was 0·3 and grass height was more than 3·5 cm. It is concluded that these indigenous vegetation communities can be used in sheep production systems to complement the use of improved pastures at other times of year. In particular, they can be utilized during the non‐lactating period (summer) to increase body condition before the beginning of the mating period in autumn.     

Factors influencing the response in intake of silage and animal performance after wilting of grass before ensiling: a review

This review examines the response in intake of silage and animal performance after wilting of grass before ensiling. It uses data from eighty‐five published comparisons. Initial analysis identified those variables having the greatest influence on the increase in dry‐matter (DM) intake of grass silage owing to wilting. Total water loss, drying rate of the wilted material and ammonia‐N concentration of the unwilted material were the variables most closely and positively correlated to the proportional increase in DM intake as a result of wilting, with r² values of 0·344, 0·393 and 0·240 respectively. There was little evidence of curvilinearity in any of the relationships. Stepwise regression analysis was used to identify the best multiple linear regressions for predicting the proportional increase in intake owing to wilting. Factors associated with the extent and rate of water loss in the field (total water loss and drying rate) and the quality of the unwilted material ensiled and its subsequent fermentation pattern (DM digestibility, crude protein, ammonia‐N content of unwilted silage) were the key variables in the relationship. Subsequent analysis related the increase in output of milk energy of dairy cows and liveweight gain of beef cattle to the same independent variables. This indicated that variables shown to describe the response in DM intake in the previous analysis were among those most closely related to the increases in animal performance owing to wilting of grass. To assess whether the increase in animal performance owing to wilting could be explained as a direct response to increased metabolizable energy (ME) intake of wilted compared with unwilted silages, linear relationships were derived between the increase in milk and beef production parameters and the increase in ME intake owing to wilting. From these, it was concluded that there was no clear evidence that wilting reduced the efficiency of utilization of ME in beef or dairy cattle. The present study showed that the increase in milk energy output (measured in MJ) per increase in ME intake (measured in MJ) owing to wilting was linear, with a slope of 0·19. This response from additional ME intake owing to wilting is in line with what would be anticipated when increasing ME intake by other methods.     

The effects of stage of growth and additives with or without cellulase on fermentation and in vitro degradation characteristics of Leymus chinensis silage

This study evaluated the effects of different combinations of added lactic acid bacteria and cellulase applied at two growth stages on chemical composition and in vitro rumen digestibility of Leymus chinensis silage. Fresh grass was harvested at early heading stage (S1) and late heading stage (S2), respectively, and ensiled with five additives: 200 U cellulase (C) kg^?1 fresh matter (FM), 1 × 10⁵ colony‐forming units (cfu) Lactobacillus plantarum (LP) g^?1 FM, 1 × 10⁵ cfu Lb. casei (LC) g^?1 FM, LP+C, LC+C and a control (CK). Four replicates of each treatment were weighed into 5‐L plastic buckets, and the mini silos were stored at ambient temperature (~30°C) for 60 d. Leymus chinensis harvested at S2 showed relatively higher neutral detergent fibre content, coliform bacteria count and lower crude protein content than S1. All additives decreased the pH and ammonia nitrogen (NH₃‐N) content of L. chinensis silage (P < 0·001) except C. LP+C and LC+C decreased fibre content and increased water‐soluble carbohydrate content (P < 0·001). The silages were further anaerobically incubated in vitro at 39°C for 48 h with buffered rumen fluids of lactating cows. Leymus chinensis harvested at S2 showed lower in vitro dry‐matter disappearance, NH₃‐N, total volatile fatty acid (VFA) content and higher average gas production rate (P < 0·05) than S1. In conclusion, Leymus chinensis should not be harvested too late. Compared with other treatments, a combination of Lb. casei (LC) with cellulase resulted in better fermented silage, but further testing is needed to confirm its efficacy.     

A new sterilization and inoculation method in silage research

The study aimed at evaluating an effective sterilization–inoculation technique to facilitate silage research on the effect of forage microflora on fermentation variables. The sterilization effect of heating at 60°C for 3 h + 103°C for 15 h was tested on samples of grass, grass–clover, white clover and maize, pre‐dried at 60°C to a dry‐matter (DM) content >900 g kg^?1. The ensilability of treated samples, reconstituted to original DM concentration (250–390 g kg^?1), was assessed by inoculation with microfloras extracted from the original samples. Microfloral inoculants were obtained by a combination of centrifugation (15 500  g for 40 min) and filtration (0·45 and 0·22 μm pore sizes) of the supernatant. The sterilization treatment effectively sterilized the forage samples but decreased water soluble carbohydrates by 49% and N buffer solubility by 22% and increased the acid detergent insoluble N proportion of total N by 53% (P < 0·05). The reconstituted silages had 18% less lactic acid, 20% less ethanol and 37% less ammonia‐N (P < 0·05), but volatile fatty acids and 2,3‐butanediol did not differ from the untreated silages (P > 0·05). Counts of lactic acid bacteria, enterobacteria, clostridia, yeasts and moulds in the two silage treatments were also similar (P > 0·05). It is concluded that, despite causing chemical and physical alterations, the sterilization–inoculation technique evaluated could be a useful tool for future studies on the effects of microflora on ensiling results.     

The effects of allowance of deferred herbage and concentrate supplementation when offered to ewe lambs,and system of allocation when offered to ewes in late gestation,on animal performance

The effects of allowance of extended (deferred) grazed herbage (AEGH) and herbage allocation management (HAM) were studied in ewe lambs (248) and late‐gestation ewes (152), respectively, on commercial farms in south‐east Ireland in 2005–06. In Experiment 1, which consisted of four treatments, the effects of AEGH (0·75, 1·25 and 1·75 kg DM per head daily) and concentrate supplementation (0·5 kg per head daily with the 0·75 kg DM herbage allowance) on lamb performance during the extended grazing (16 December to 3 March) and subsequent grazing (4 March to 11 August) seasons were evaluated. Increasing AEGH increased herbage intake linearly (P < 0·001) and live weight (P < 0·001) at the end of extended grazing and the subsequent grazing season. In Experiment 2, single‐ and twin‐bearing ewes were allocated to either a conventional (single‐ and twin‐bearing ewes grazed separately) or leader–follower system (twin‐ and single‐bearing ewes, as leaders and followers respectively) of HAM from 30 January to 24 March. The same quantities of herbage were offered daily for each system. System of HAM affected ewe condition score at lambing but did not alter (P > 0·05) subsequent lamb birth or weaning weights. It is concluded that increasing AEGH to ewe lambs increased liveweight gain during extended grazing and resulted in heavier animals in mid August of the subsequent grazing season. For ewe lambs each 1 kg concentrate DM had the same feed value as 2·4 kg DM AEGH. Use of a leader–follower system for ewes in late pregnancy did not alter lamb birth weight or subsequent performance.     

The implications of controlling grazed sward height for the operation and productivity of upland sheep systems in the UK. 4. The effect of seasonal pattern of nitrogen fertilizer application and annual stocking rate

Greyface (Border Leicester × Scottish Blackface) ewes, mated in October, were housed in winter and turned out after lambing in late March to one of four treatments replicated three times on perennial ryegrass (Lolium perenne)-dominated pastures. On three of the treatments the stocking rate was 12·5 ewes plus lambs ha^?1 annum^?1 (SR_12·5), whereas on the fourth it was 15·0 ewes plus lambs ha^?1 annum^?1 (SR_15·0). There were two levels of applied fertilizer nitrogen (N), 152 kg N ha^?1 annum^?1 (N₁₅₂) and 205 kg N ha^?1 annum^?1 (N₂₀₅). Three patterns of nitrogen application were used: predominantly in spring (E), predominantly in autumn (L), and mainly in spring and autumn (E + L). Grazed sward surface height was controlled within the range 3·5–5·5 cm during spring and summer, and supplementary feed was offered when sward height was below 3·5 cm. The effects on animal performance, yield of silage and requirement for supplementary feed were measured over 3 years (1986–88). Management of the sward height within the specified limits resulted in similar levels of individual animal performance for all treatments, but treatment SR_15·0N₂₀₅E + L produced a significantly (P < 0·05) greater output of lamb per hectare. There was no evidence to suggest that, by increasing the amount of N fertilizer applied in the autumn, ewe reproductive performance was increased. Neither the treatment with the lower level of N applied in the spring (SR_12·5N₁₅₂L) nor the high stocking rate treatment (SR_15·0N₂₀₅E + L) was self-sufficient in winter feed (silage) production. SR_15·0N₂₀₅E + L also required more supplementary feed in both the lactation (38·1 kg ewe^?1) and the mating (9·1 kg ewe^?1) periods. SR_12·5N₁₅₂L required the second greatest amount of supplementary feed during lactation (36·1 kg ewe^?1), whereas SR_12·5N₂₀₅E + L required the least supplementary feed over both periods (27·8 kg and 4·8 kg ewe^?1). Taking all treatments together, there were significant (P < 0·05) differences between years in lamb weaning weight (kg), lamb output (kg ha^?1), yield of silage (kg ewe^?1) and supplementary feed required (kg ewe^?1), arising mainly from a lower level of herbage production in one year. Treatment SR_12·5N₁₅₂E generated the highest gross margin per hectare.     

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

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

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

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

Effects of treating low dry-matter grass with a bacterial inoculant on the intake and performance of beef cattle and studies on its mode of action

A randomized block design experiment involving thirty beef cattle (mean initial live weight 462 kg) was carried out to evaluate a bacterial inoculant based on a single strain of Lactobacillus plantarum as a silage additive and to provide further information in relation to its mode of action. Three herbages were harvested on 10 August 1989 using three double-chop forage harvesters from the first regrowth of a perennial ryegrass sward which had received 170 kg N, 25 kg P₂O₅, and 42 kg K₂O ha^?1. They received either no additive (silage C), formic acid at 2·91 (t grass)^?1(silage F) or the inoculant at 3·21 (t grass)^?1 (silage I). Mean dry-matter (DM), water-soluble carbohydrate and crude protein concentrations in the untreated herbages were 158g kg^?1, 88 g (kg DM)^? and 183g (kg DM)^?1 respectively. For silages C, F and I respectively, pH values were 4·01, 3·57 and 3·62; ammonia N concentrations 117, 55 and 77 g (kg total N)^?1; and butyrate concentrations 2·18, 0·50 and l·24g (kg DM)^?1. The silages were offered ad libitum and supplemented with 2·5 kg concentrates per head daily for 77 days. For treatments C, F and I, silage DM intakes were 6·59, 7·25 and 6·80 (s.e. 0·074)kg d^?1; metabolizable energy (ME) intakes 86,99 and 94 (s.e. 0·8) MJ d^?1; liveweight gains 0·90, 0·97 and 1·02(s.e.0·066) kg d^?1; carcass gains 541,656 and 680 (s.e. 34·0) g d^?1. Inoculant treatment increased DM (P < 0·01), organic matter (P < 0·01), crude fibre (P < 0·05), neutral detergent fibre (NDF) (P < 0·05) and energy (P < 0·05) digestibilities, the digestible organic matter concentration (P < 0·01) and the ME concentration (P < 0·05) of the total diets. Additive treatment altered rumen fermentation patterns but had little effect on the rumen degradability of silage DM, modified acid detergent (MAD) fibre, NDF or hemicellulose. It is concluded that treatment with the inoculant improved silage fermentation and increased digestibility, had little effect on silage DM intake but significantly increased carcass gain to a level similar to that sustained by a well-preserved formic acid-treated silage     

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

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

Effect of feed space allowance and period of access to food on dairy cow performance

Two experiments were conducted to examine the ‘long‐term’ effect of feed space allowance and period of access to feed on dairy cow performance. In Experiment 1, three horizontal feed space allowances (20, 40 and 60 cm cow^?1) were examined over a 127‐d period (14 cows per treatment). In Experiment 2, 48 dairy cows were used in a continuous design (10‐week duration) 2 × 2 factorial design experiment comprising two horizontal feed space allowances (15 and 40 cm cow^?1), and two periods of access to feed (unrestricted and restricted). With the former, uneaten feed was removed at 08·00 h, while feeding took place at 09·00 h. With the latter, uneaten feed was removed at 06·00 h, while feeding was delayed until 12·00 h. Mean total dry‐matter (DM) intakes were 19·0, 18·7 and 19·3 kg cow^?1 d^?1 with the 20, 40 and 60 cm cow^?1 treatments in Experiment 1, and 18·1 and 18·2 kg cow^?1 d^?1 with the ‘restricted feeding time’ treatments, and 17·8 and 18·1 kg d^?1 with the ‘unrestricted feeding time’ treatments (15 and 40 cm respectively) in Experiment 2. None of milk yield, milk composition, or end‐of‐study live weight or condition score were significantly affected by treatment in either experiment (P > 0·05), while fat + protein yield was reduced with the 15‐cm treatment in Experiment 2 (P < 0·05). When access to feed was restricted by space or time constraints, cows modified their time budgets and increased their rates of intake.     

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

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

Effect of defoliation management, based on leaf stage, on perennial ryegrass (Lolium perenne L.), prairie grass (Bromus willdenowii Kunth.) and cocksfoot (Dactylis glomerata L.) under dryland conditions. 2. Nutritive value

A field experiment was undertaken between April 2003 and May 2004 in southern Tasmania, Australia, to quantify and compare changes in the nutritive value of perennial ryegrass (Lolium perenne L.), prairie grass (Bromus willdenowii Kunth.) and cocksfoot (Dactylis glomerata L.) under a defoliation regime based on stage of leaf regrowth. Defoliation interval was based on the time taken for two, three or four leaves per tiller to fully expand. At every defoliation event, samples were collected and analysed for acid‐detergent fibre (ADF), neutral‐detergent fibre (NDF) and total nitrogen (N) concentrations and to estimate metabolizable energy (ME) and digestible dry matter (DDM) concentrations. Amounts of crude protein (CP) and metabolizable energy (MJ) per hectare values were subsequently calculated. There was a significantly lower (P < 0·001) NDF concentration for perennial ryegrass compared with prairie grass and cocksfoot, and a significantly lower (P < 0·001) ADF concentration for cocksfoot compared with prairie grass and perennial ryegrass, regardless of defoliation interval. The CP concentration of cocksfoot was significantly greater (P < 0·001) compared with the CP concentrations of prairie grass and perennial ryegrass. The estimated ME concentrations in cocksfoot were high enough to satisfy the requirements of a lactating dairy cow, with defoliation at or before the four‐leaf stage maintaining ME concentrations between 10·7 and 10·9 MJ kg^?1 DM, and minimizing reproductive plant development. The ME concentrations of prairie grass (10·2–10·4 MJ kg^?1 DM) were significantly lower (P < 0·001) than for cocksfoot (as above) and perennial ryegrass (11·4–11·6 MJ kg^?1 DM) but a higher DM production per hectare resulted in prairie grass providing the greatest amounts of ME ha^?1.     

Lactic acid bacteria strains for enhancing the fermentation quality and aerobic stability of Leymus chinensis silage

Leymus chinensis is an important grass in China and Russia. Six lactic acid bacteria (LAB) strains (LB, LPL1, LPL2, LPL3, LCL and WH) from L. chinensis silage were screened and identified and their effects on fermentation quality were investigated. All six strains were grown at 6·5% NaCl and pH 4·00. Strains LPL1, LPL2 and LPL3 were identified as Lactobacillus plantarum, and LB, WH and LCL were classified as Lactobacillus brevis, Weissella hellenica and Lactobacillus casei respectively. The six isolated strains and a commercial inoculant (Lactobacillus buchneri) were added to L. chinensis for ensiling at densities of 500 and 600 kg m^?3. The control was sprayed with the same volume of distilled water. The effects of the strains on fermentation quality after 45 d ensiling and aerobic stability during 8 d of exposure to air were evaluated. The 600 kg m^?3 silage had lower pH, butyric acid, ammonia nitrogen content and coliform bacteria counts than the 500 kg m^?3 density silage (P < 0·05). The six isolated strains decreased pH, butyric acid content and increased lactic acid content, and all inoculants increased L. chinensis silage aerobic stability except LCL (P < 0·05). The fermentation quality of L. chinensis silage increased with higher ensiling density. The LAB strains improved the fermentation quality, and high‐quality silage could be obtained at low ensiling density with the addition of the LAB strains. The strains improved the aerobic stability; Lb. buchneri and Lb. brevis showed the best performance.     

Mixtures of clovers with plantain and chicory improve lamb production performance compared to a ryegrass–white clover sward in the late spring and early summer period

A research programme was undertaken over two consecutive years with the purpose of studying the effect of herb–clover swards on lamb production performance year‐round. The focus of this study was on two consecutive late spring and early summer periods (2011, 2012). In each year, three sward treatments were compared on grazed paddocks with 40 lambs ha^?1: (i) grass–clover mixture (perennial ryegrass [Lolium perenne L.] and white clover [Trifolium repens]); (ii) plantain–clover mixture (plantain [Plantago lanceolata], white clover and red clover [Trifolium pratense]); and (iii) chicory–plantain–clover mixture (plantain, chicory [Cichorium intybus L.] and white and red clovers). Lambs were weighed at 2‐week intervals, and carcass weights and GR tissue depth measurements were obtained at slaughter. In both years, lambs on treatments (ii) and (iii) had greater (P < 0·05) final live weight, liveweight gain, carcass weight, dressing‐out percentage and GR tissue depth measurements, and lower feed conversion ratio compared to lambs on treatment (i). Lamb production was similar in treatments (ii) and (iii) (P > 0·05) in each year. Therefore, during the late spring and early summer period, herb–clover mixture swards were found to be a superior option to perennial ryegrass–white clover for finishing lambs.     

Effects of feeding different ensiled forages on the productivity and nutrient-use efficiency of finishing lambs

The effects of offering ensiled red clover (Trifolium pratense), lucerne (Medicago sativa), pea (Pisum sativum), kale (Brassica oleracea) and hybrid ryegrass (Lolium hybridicum) on the productivity and nutrient‐use efficiency of lambs were investigated. Forages were cut, wilted for 24 h and ensiled as round bales. A hundred Suffolk‐cross lambs, aged 8 months, were offered grass silage during a 5‐week standardization period and then group‐housed for 14 d and offered ad libitum access to a treatment silage. For the measurement period, lambs were split into four replicate groups of five lambs per treatment. Dry matter intake and live weight were recorded every 7 d over 56 d. The chemical composition of the silages differed for all the variables measured. Lambs offered pea silage had a very low liveweight gain and this treatment was discontinued after 21 d. Lambs offered the other forages had a higher liveweight gain than lambs offered ryegrass silage (P < 0·001). Food conversion and nitrogen‐use efficiency were higher in lambs offered the red clover, lucerne and kale silages compared with those offered ensiled ryegrass (P < 0·001). These findings demonstrate the potential for using ensiled alternative forages rather than ryegrass to increase the productivity and nutrient use efficiency of livestock systems.     

Effects of addition of lactic acid and post-ruminal supplementation with casein on the nutritional value of grass silage for milk production in dairy cows

Two levels of lactic acid were added to a well-preserved silage to give silages with three concentrations of lactic acid: 53 (control), 96 (LA-50) and 134 (LA-100)g (kg DM)^-1. These silages were given ad libitum with 5 kg d^-1 of a mixture of barley and soya-bean meal (75:25) to six lactating dairy cows in a 6 × 6 Latin square design experiment to examine the effects on silage intake and milk production of the addition of lactic acid, both with and without a post-ruminal supplement of 230 gd^-1 sodium caseinate. The six treatments were (1) control silage without casein, (2) control silage plus casein, (3) LA-50 silage without casein, (4) LA-50 silage plus casein, (5) LA-100 silage without casein and (6) LA-100 silage plus casein. Sodium caseinate was administered as a continuous infusion into the abomasum. Periods were 14d long. Both levels of addition of lactic acid reduced (P < 0·001) the intake of silage, values being 102, 94 and 86 kg DM d^-1 for the control, LA-50 and LA-100 treatments respectively, but the casein supplement did not affect the intake of silage. Milk yield was reduced (P < 0·01) only for treatment LA-100 and, for this treatment, was restored (P < 0·01) by casein given post-ruminally. With all three silage treatments, casein infusion increased (P<0·001) the yield of protein in milk by 30–35 gd^-1. The concentration of protein in milk increased linearly (P < 0·001) with the addition of lactic acid to the silage. The addition of lactic acid produced a linear reduction (P < 0·001) in the molar proportion of acetate in rumen contents and compensatory linear increases (P < 0·001) in the molar proportions of propionate and butyrate. Changes during the day in the concentration of insulin in blood plasma followed a similar pattern to changes in the molar proportions of propionate. The mean daily concentration of insulin in plasma tended (0·10 < P > 0·05) to be higher for the LA-100 treatment, and in the immediate period after feeding this difference was significant (P < 0·05). The results confirm the effect of lactic acid in depressing the intake of silage, but they offer no support for the hypothesis that the depression of intake can be offset by an increase in the supply of protein post-ruminally.     

THE EFFECT OF FEEDING RED CLOVER CONSERVED BY DRYING OR ENSILING ON REPRODUCTION IN THE EWE

Forage diets were prepared from ryegrass (non oestrogenic control) and from red clover as pellets or as unwilted silage. Each diet was fed to separate groups of 20 Border Leicester × Cheviot ewes for three weeks prior to the introduction of the ram, and for two cycles after mating. Subsequently, all three groups of ewes were fed in a similar manner until lambing and the reproductive performance of the ewes was measured. The control diet was prepared by barn drying a primary growth crop of perennial ryegrass, Lolium perenne cv S23. Tetraploid red clover, Trifolium pratense cv. Hungarpoly, was harvested as a first regrowth crop and the pelleted diet prepared by high temperature drying, grinding (2 mm screen) and pelleting. The silage was prepared without wilting. The level of formononetin in the red-clover silage was three times that in the dried red-clover pellets. Compared with the control grass diet, the feeding of red clover in either form significantly reduced (P<0·001) the number of lambs born. The incidence of barrenness was higher (P<0·001) for ewes fed red-clover silage compared with red-clover pellets and the control diet. The rate of twinning was significantly (P<0·001) higher for the ewes fed the control grass diet than for either of the red-clover diets. The resultant lambing percentages were 190,165, and 100% for the control grass, red-clover pellet and red-clover silage treatments. In flock management, both the grazing of red clover and the feeding of red-clover pellets or silage, prior to and during mating, should be avoided.