Dominant Swards Research Articles

Nitrogen fertiliser application rate to temperate mid-season grass: Digestion, nitrogen balance and rumen microbiota in beef cattle, and rumen fermentation and methane production in vitro

Nitrogen (N) excretion by cattle, particularly urinary N, can have detrimental environmental impacts on air and water quality, and contributes to greenhouse gas emissions. The effects of increasing the application rate of inorganic N fertiliser from 15 (N15) to 80 (N80) kg/ha per cut to Lolium perenne dominant swards in summer, on intake, rumen fermentation, rumen microbial populations, apparent total-tract digestibility and N-balance in beef cattle, and in vitro fermentation and methane output, were studied. Sixteen suckler-bred Charolais steers, used in a randomised block design experiment, were offered fresh grass mechanically harvested 21-d after N fertiliser application. Similar grass was incubated in an eight-vessel in vitro RUSITEC system. Grass crude protein concentration was 50 g/kg dry matter (DM) higher for N80 compared to N15. There was no difference in grass DM intake between treatments. Rumen fermentation variables did not differ between treatments, except for the molar proportion of propionate, which was greater for N80 than N15. Gross microbial community structure in the rumen was not significantly altered by inorganic N fertiliser application rate. The relative abundance of individual genera Lachnospiraceae_NK3A320_group and Ruminococcaceae_NK4A214_group, and Acetitomaculum were significantly lower at the higher N application rate. Mean plasma urea concentration was greater for N80 compared to N15. In vivo digestibility of DM, organic matter, neutral detergent fibre and acid detergent fibre was unaffected by fertiliser N application rate. Nitrogen intake was 75 g/d greater, and urinary and faecal N excretion were 20 and 5 g/d greater, respectively, for N80 than N15. The quantity of N retained and N use efficiency was greater for N80 compared to N15. In vitro NH3 concentration was greater for N80 than N15, whereas other rumen fermentation variables, and in vitro methane and total gas output, did not differ between treatments. Reducing the inorganic N fertiliser rate applied to mid-season temperate grass reduced N excretion from beef cattle, which is environmentally beneficial, with no effect on in vitro methane production.

Effects of fertiliser nitrogen rate to spring grass on apparent digestibility, nitrogen balance, ruminal fermentation and microbial nitrogen production in beef cattle and in vitro rumen fermentation and methane output

The effects of two fertiliser nitrogen (N) application rates - 15 (LN) or 80 (HN) kg N/ha - to Lolium perenne dominant swards in spring, on grass dry matter (DM) intake, digestion, rumen fermentation, microbial N production and N-balance in beef cattle, and in vitro fermentation and methane production were studied. Sixteen Charolais steers with a mean live weight (s.d.) of 475 (18.4) kg, were used in a completely randomised block design experiment and offered zero-grazed grass harvested 21-d post N application. The same grass was incubated in an eight-vessel RUSITEC in a completely randomised block design experiment. The HN treatment had a 540 kg/ha higher grass DM yield, and a 20 g/kg DM higher crude protein (CP) concentration compared to LN. There was no difference (P > 0.05) in DM intake, or in vivo DM, organic matter (OM) and N digestibility between treatments. Rumen fermentation variables pH, lactic acid, ammonia (NH3) and total volatile fatty acid (VFA) concentration were similar (P > 0.05) for both treatments. Nitrogen intake was 19 g/d higher (P < 0.05) for HN compared to LN. Total and urine N loss was 16 and 14 g/d greater (P < 0.05), respectively, for HN compared to LN, but faecal N loss did not differ (P > 0.05) between treatments. The quantity of N retained and N-use efficiency did not differ (P > 0.05) between LN and HN. Plasma urea concentration was 1 mmol/L greater (P < 0.05) for HN compared to LN. Estimated microbial N production was greater (P < 0.05) for HN compared to LN. In vitro NH3 concentrations were higher (P < 0.05) for HN compared to LN, whereas in vitro rumen pH, lactic acid and VFA concentrations and molar proportions did not differ (P > 0.05) between HN and LN. In vitro methane and total gas output were not different (P > 0.05) between treatments. Reducing fertiliser N application rate to grass in spring reduced total and urinary N excretion, which has environmental benefits, with no effects on in vitro methane output.

地下茎イネ科草種優占草地の簡易更新に関する研究(2) : 草地更新時の前植生抑圧のためのグリホサート除草剤の散布時期と散布量

地下茎イネ科草種優占草地の簡易更新に関する研究(2) : 草地更新時の前植生抑圧のためのグリホサート除草剤の散布時期と散布量

地下茎イネ科草種優占草地の簡易更新に関する研究 : 1. 更新前優占地下茎イネ科草種の抑圧法

地下茎イネ科草種優占草地の簡易更新に関する研究 : 1. 更新前優占地下茎イネ科草種の抑圧法

Frequency and intensity of grazing in winter: their effects on herbage accumulation and nutritive value of Lolium perenne L. dominant swards

A study was conducted in southern Chile with the objective of determining the effect of two frequencies and two intensities of grazing, measured as herbage mass, on production and nutritive value of a permanent sward dominated by Lolium perenne L. during winter season. Additionally the residual effect of the treatments applied in winter was evaluated on the same variables in the following spring. Two pre-grazing herbage mass (kg DM ha-1): low frequency (1,800), high frequency (1,500) and two post-grazing herbage mass: low intensity (1,300), high intensity (1,000), were evaluated. Plots of 145.7 m2 were grazed by dairy cows. The same plots were grazed in the subsequent spring to a frequency of 2,400 kg DM ha-1 and intensity of 1,400 kg DM ha-1. There was no significant effect of the frequency of grazing on herbage mass and growth rate during the first winter. However, in the second winter a greater production with low frequency was obtained. In the two winter seasons, a significant effect of the intensity was obtained, with greater production in high intensity. The most frequently grazed treatments showed higher crude protein and lower soluble carbohydrates. Also, there was a residual effect in the spring generated by frequency and intensity of grazing in the first year, and only for the intensity the second year. It can be concluded that frequency and intensity of grazing applied in winter generate changes in herbage mass production and nutritive value of the sward and also a residual effect in the following spring.

Does it matter if herbivory is selective? Responses of an endangered herbaceous legume to experimental grazing

Background: Herbivory and inter-specific competition are major determinants of the relative abundance of plant species in grasslands. Herbivores modify competitive hierarchies among plants through selective foraging and as a result of variation in the relative tolerance of plants to herbivory. Aims: We examined the direct effects of herbivory and the role of herbivore preference on the growth, flowering and abundance of an endangered perennial legume, Cullen parvum (F. Muell.) J.W. Grimes, in a temperate Australian grassland grazed by sheep. Methods: Hand clipping was used to simulate herbivory. In each of two populations, three replicates of the factorial combination of C. parvum defoliation (C. parvum grazed or ungrazed), neighbour defoliation (neighbouring vegetation grazed or ungrazed) and three defoliation frequency treatments were randomly applied to 0.25-m2 quadrats containing C. parvum ramets. Results: The abundance, growth and flowering of C. parvum were similarly reduced by both selective and non-selective herbivory. When neighbouring vegetation but not C. parvum was defoliated, growth and abundance were similar and in some cases less than when both neighbours and C. parvum were ungrazed, suggesting little above-ground competitive effect of the grassland sward. Conclusions: The interactions between herbivory and shoot competition by dominant perennial grassy swards had little influence on the growth and abundance of C. parvum. Rather, direct effects of defoliation dominated and we predict that the species persistence in grazed grasslands will be influenced more by poor tolerance of herbivory than by how herbivores modify the competitive effect of neighbouring vegetation.

A herb and legume sward mix increased ewe milk production and ewe and lamb live weight gain to weaning compared to a ryegrass dominant sward

This study investigated the potential of a mixed herb sward to improve production of multiple-bearing ewes and their offspring compared to a ryegrass dominant sward. Forty four twin-bearing (twin) and 42 triplet-bearing (triplet) mixed-aged Romney ewes that were a maximum of 140 days pregnant (P140) were randomly allocated to one of two nutritional treatments being: a mix of chicory, plantain, white and red clover (Herb), or a ryegrass dominant sward (Ryegrass) to form the following groups: twin Ryegrass n = 22, triplet Ryegrass n = 20, twin Herb n = 22 and triplet Herb n = 22. Ewes and their lambs remained on these herbage treatments until 66 days after the mid-point of lambing (L66). By L66, ewes grazing the Herb treatment compared to ewes on the Ryegrass treatment were heavier (P<0.05; 70.9 ± 1.17 kg versus 66.1 ± 1.15 kg) and had higher (P<0.05) body condition scores (2.8 ± 0.07 versus 2.4 ± 0.07, respectively). Ewes grazing the Herb treatment produced more milk (P<0.05) at each of the three sampling periods (3137 ± 161.3 versus 2613 ± 148.1 at day 7, 3280 ± 148.8 versus 2483 ± 153.1 at day 14 and 3237 ± 131.8 mL versus 2428 ± 136.2 mL at day 21). Lambs from ewes grazing the Herb treatment were heavier (P<0.05) at L22 (10.36 ± 0.274 kg versus 9.29 ± 0.272 kg) and L66 (20.67 ± 0.490 kg versus 17.55 ± 0.493 kg). The higher live weights (LW) were due to higher (P<0.05) LW gains of Herb lambs between birth and L22 (298 ± 10.8 g/day versus 245 ± 10.7 g/day) and between L39 and L66 (268 ± 16.2 g/day versus 179 ± 15.9 g/day). Herb triplet-bearing ewes produced more (P<0.05) total lamb LW by L66 than Ryegrass triplet-bearing ewes (45.70 ± 3.051 kg versus 28.26 ± 3.203 kg, respectively). Results demonstrate that a herb sward mix can improve multiple ewe and lamb performance compared to a ryegrass dominant sward.

Interaction between water‐soluble carbohydrate reserves and defoliation severity on the regrowth of perennial ryegrass (Lolium perenne L.)‐dominant swards

AbstractA field‐study was undertaken in Hamilton, New Zealand to determine if there was an interaction between water‐soluble carbohydrate (WSC) reserve content and defoliation severity on the regrowth of perennial ryegrass‐dominant swards during winter. Perennial ryegrass plants with either low or high WSC content were obtained by varying the defoliation frequency. At the third defoliation at the one‐leaf stage and at the first defoliation at the three‐leaf stage (harvest H1), swards were mown with a rotary lawnmower to residual stubble heights of 20, 40 or 60 mm. All swards were then allowed to regrow to the three‐leaf stage before again defoliating to their treatment residual stubble heights (H2). Frequently defoliated plants contained proportionately between 0·37 and 0·48 less WSC in the stubble after defoliation, depending on the severity of defoliation. There was no interaction between WSC content and defoliation severity for herbage regrowth between harvests H1 and H2. Herbage regrowth was lower from swards containing low WSC plants compared with high WSC plants (2279 vs. 2007 kg DM ha−1). Furthermore, swards defoliated to 20 or 40 mm had greater herbage regrowth compared with those defoliated to 60 mm (2266, 2249 and 1914 kg DM ha−1 for swards defoliated to residual stubble heights of 20, 40 and 60 mm, respectively). Regrowth of perennial ryegrass was positively correlated with post‐defoliation stubble WSC content within defoliation severity treatment, implying that WSC contributed to the defoliation frequency‐derived difference in herbage yield. However, the effect of defoliation severity on herbage regrowth was not associated with post‐defoliation stubble WSC content.

Effect of Defoliation Severity on Regrowth and Nutritive Value of Perennial Ryegrass Dominant Swards

The height or mass to which swards are defoliated can potentially affect regrowth. A field study was undertaken to determine the response of perennial ryegrass (Lolium perenne L.) dominant swards to defoliation severity over repeated defoliations during a period of low water‐soluble carbohydrate (WSC) accumulation (late spring to mid‐autumn due to active leaf growth and relatively high respiration). Five defoliation severities (defoliation to a residual stubble height [RSH] of 20, 40, 60, 80, or 100 mm) were replicated five times in a Latin square design. During a 6‐mo period, treatment plots were defoliated seven times using a rotary lawnmower. Analysis of data indicated a quadratic relationship between RSH and total herbage production, with total yields of 12,190, 13,440, 13,730, 13,320, and 11,300 kg DM ha−1 for swards defoliated to 20, 40, 60, 80, and 100 mm, respectively. Regression analyses identified 56 mm as the optimal RSH for herbage production, but there was little biological significance between 40 and 80 mm RSH. Total WSC content per tiller was reduced with increasing defoliation severity. The relationship between WSC content per tiller and subsequent herbage yield was quadratic, with peak herbage yield at 9.4 mg tiller−1 (60 mm RSH). The data indicate that between September (spring) and April (autumn), herbage production of temperate perennial ryegrass‐dominant swards is maximized when defoliation severity results in post‐grazing stubble heights of 40 to 80 mm.

Effects of the composition of irrigated perennial pasture on the milk production of dairy cows and their responses to supplementation with cereal grain-based concentrates

The objective of the research described here was to compare the milk production from paspalum (Paspalum dilatatum Poir.)-dominant swards with milk production from perennial ryegrass (Lolium perenne L.)–white clover (Trifolium repens L.)-dominant swards. Eight experiments were conducted over a 2-year period, during which half the cows grazed pastures that had been established for more than 15 years (old pasture) and were dominated by paspalum in summer, while the remaining cows grazed pastures sown within the previous 2–3 years (new pasture), which were dominated by temperate species. Groups of four to five lactating Friesian cows grazed either old or new pasture and were either unsupplemented or were offered ~5 kg DM/cow.day of a high energy supplement (75% barley and 25% wheat). The hypothesis was that milk production would be greater from cows grazing new pastures than old pastures (at common pasture allowances), but that marginal milk responses when cereal grain-based supplements were fed would be greater when cows grazed old pastures; this was only partially supported. Milk yields were generally greater when cows grazed new pastures, but in six out of eight experiments, the advantage was only ~1 kg milk (100 g fat plus protein)/cow or less. In these six experiments, the difference in metabolisable energy density between the pastures was 0.7 MJ/kg DM or less. When concentrates were fed to supplement grazed pasture, there were seasonal variations, but similar marginal responses in milk production were recorded on both pastures throughout the study.

Effect of Defoliation Severity on Regrowth and Nutritive Value of Perennial Ryegrass Dominant Swards

The height or mass to which swards are defoliated can potentially affect regrowth. A field study was undertaken to determine the response of perennial ryegrass (Lolium perenne L.) dominant swards to defoliation severity over repeated defoliations during a period of low water-soluble carbohydrate (WSC) accumulation (late spring to mid-autumn due to active leaf growth and relatively high respiration). Five defoliation severities (defoliation to a residual stubble height [RSH] of 20, 40, 60, 80, or 100 mm) were replicated five times in a Latin square design. During a 6-mo period, treatment plots were defoliated seven times using a rotary lawnmower. Analysis of data indicated a quadratic relationship between RSH and total herbage production, with total yields of 12,190, 13,440, 13,730, 13,320, and 11,300 kg DM ha−1 for swards defoliated to 20, 40, 60, 80, and 100 mm, respectively. Regression analyses identified 56 mm as the optimal RSH for herbage production, but there was little biological significance between 40 and 80 mm RSH. Total WSC content per tiller was reduced with increasing defoliation severity. The relationship between WSC content per tiller and subsequent herbage yield was quadratic, with peak herbage yield at 9.4 mg tiller−1 (60 mm RSH). The data indicate that between September (spring) and April (autumn), herbage production of temperate perennial ryegrass-dominant swards is maximized when defoliation severity results in post-grazing stubble heights of 40 to 80 mm.

Visible fungal growth on baled grass silage during the winter feeding season in Ireland and silage characteristics associated with the occurrence of fungi

The extent of visible fungal growth and the identity of fungi causing spoilage of baled grass silage were recorded regularly through a winter feeding period in Ireland. The study was conducted from November 2003 to March 2004 on 50 farms differing in farming systems and geographical locations in the Irish Midlands and two bales were examined in detail on each farm ( n = 100 bales). Visible fungal growth was present on 90 of the 100 bales examined. There were more fungal colonies visible on bales in March (mean, 8) than in November (mean, 4) (P<0.05), but the number of fungal colonies on bales did not differ between the very youngest and oldest bales (P>0.05). Fungal contamination was higher (P<0.001) in bales where the surrounding polythene stretch-film was visibly damaged compared to bales where the film appeared intact. No other bale production or storage characteristic significantly predisposed bales to increased fungal spoilage. The most prevalent fungus on bales throughout the feeding season was Penicillium roqueforti which represented 0.43 of all fungal colonies observed and was present on 0.78 of bales. The proportion of bale surface areas visibly colonised by P. roqueforti increased (P<0.05) monthly from November to March. Other fungi frequently isolated throughout the winter included Schizophyllum commune, mucoraceous moulds and Pichia fermentans. Redundancy analysis showed that the distribution of fungi on bales was best explained by the concentrations of ethanol and lactic acid, dry matter content, bale tying, month of bale feed-out, age of bales, polythene film damage, ryegrass dominance, bale storage location and volatile fatty acid concentrations. Forward selection of these silage characteristics showed that butyric acid concentration and age of bales contributed significantly (P<0.05) to the variance found in the species data and these two variables could explain 0.19 of the explained variance. P. roqueforti occurrence was positively correlated to higher concentrations of propionic and butyric acids, to month of bale feed-out and to bale age. S. commune was more commonly isolated from bales made from ryegrass dominant swards, that had visibly damaged polythene film, that were stored in farmyards and from silage with a lower lactic acid concentration. Overall, a high incidence of visible fungal growth was recorded on bales throughout the winter season and the extent of colonisation and fungal species occurring were not random. To prevent fungal spoilage of baled silage, the focus of best farm practice should be to provide low oxygen conditions in well wrapped and carefully managed bales.

In vitro methane production of different cultivars of perennial ryegrass

Irish livestock production systems are characterised by the high utilization of grazed grass combined with minimal supplementary feeding. As such the options to reduce methane (CH4) production, particularly for beef animals, is limited to the finishing period when diet can be controlled and varied. No data is available regarding the methanogenic potential of differing grass cultivars. This study assessed CH4 output, as measured in vitro, of six ryegrass cultivars, with the aim of quantifying the potential for enteric CH4 emissions to be reduced from ruminants grazing ryegrass dominant swards.

Effect of herbage mass per unit area and conditioning treatment on herbage drying rate

The rates of drying of herbage, cut from perennial ryegrass (Lolium perenne L.) – dominant swards and subjected to different treatments, were investigated under field conditions by changes in weight of herbage in wire mesh trays in 1995 and 1996. A series of replicated factorial experiments studied the effects, in different combinations, of intensity of conditioning achieved by passing the cut herbage through a laboratory‐scale macerator zero (0C), once (1C), three (3C) or six (6C) times; weight of herbage per unit area equivalent to 450, 675 and 900 g dry matter (DM) m−2. In one experiment, pressing the herbage to form a mat was incorporated into the experimental design. A further experiment investigated the effect of varying the proportion of conditioned herbage in the herbage mass from 0·00, 0·25, 0·50, 0·75 and 1·00 on drying rate. On each occasion the trays plus herbage were weighed at hourly intervals over an ≈6‐h period and the DM content of the herbage estimated from the change in weight. On all occasions, conditioning and weight of herbage per unit area significantly (P &lt; 0·001) influenced herbage drying rate. Lowering the weight per unit area of both unconditioned and conditioned herbage increased the rate of moisture loss. Unconditioned herbage at the equivalent of a herbage mass of 450 g DM m−2 had a total moisture loss that was on average 1·5–1·8 times greater than unconditioned herbage at the equivalent of a herbage mass of 900 g DM m−2. Similarly, conditioned herbage at the equivalent of a herbage mass of 450 g DM m−2 had a total moisture loss that was 1·8–2·3 times greater than unconditioned herbage at the equivalent of a herbage mass of 900 g DM m−2. Increasing the level of conditioning produced a non‐linear response in rate of moisture loss, consequently 3 passes through the macerator produced &gt;0·95 of the total moisture loss that was produced by 6 passes through the macerator. Increasing the proportion of conditioned herbage in the herbage mass increased rate of moisture loss and consequently final DM content (P &lt; 0·001) although there was little effect from increasing the proportion of conditioned herbage above 0·75. The effects of conditioning and weight of herbage per unit area treatments on total nitrogen , water‐soluble carbohydrate and acid‐detergent fibre concentration of the herbage were small.

A comparative study of herbage intake, ingestive behaviour and diet selection, and effects of condensed tannins upon body and wool growth in lambs grazing Yorkshire fog (Holcus lanatus) and annual ryegrass (Lolium multiflorum) dominant swards

An experiment was carried out from August to early November 1994 to examine differences in diet selection, herbage intake, grazing behaviour and animal performance between weaned lambs rotationally grazing swards of annual ryegrass (Lolium multiflorum)/white clover (Trifolium repens) and Yorkshire fog (Holcus lanatus)/T. repens with or without Lotus corniculatus. There were four replicate groups of six lambs per treatment. The effects of condensed tannins (CT) on lamb production were assessed by twice-daily oral administration of 10g polyethylene glycol (PEG; molecular weight 4000) to half the lambs on each sward. The Lotus content of all swards was very low, and results are presented here for main sward comparisons meaned over lotus treatments. Overall mean estimates of pre-grazing herbage mass and sward surface height for the annual ryegrass and Yorkshire fog swards respectively, were 5820 v. 4360±190 kgDM/ha (P&lt;0·001) and 29 v. 21±0·6cm (P&lt;0·001). The coefficient of organic matter digestibility (OMD) of the diet selected and herbage intake were higher on Yorkshire fog than on annual ryegrass (0·78 v. 0·74 ± 0·080g/kg; P&lt;0·05, and 1070 v. 860±57g OM per lamb per day, P&lt;0·05 respectively), reflecting the higher content in the diet of grass green leaf (980 v. 930g/kg±14g/kg, P&lt;0·05) and the lower content of dead material (80 v. 110±15g/kg, P&lt;0·08). Lambs grazing on Yorkshire fog swards had higher clean wool growth rate (1470 v. 1280±30mg/cm per day, P&lt;0·01) and greater fibre diameter (31 v. 29±0·2μ, P&lt;0·001), greater liveweight gain (152 v. 108±5·5g/day, P&lt;0·001), final weight (42 v. 38±0·5kg, P&lt;0·001), carcass weight gain (89 v. 69±2·5g/day, P&lt;0·001), carcass weight (19 v. 17±0·3kg, P&lt;0·001) and soft tissue thickness (GR value 11 v. 8±0·5mm, P&lt;0·01), and lower faecal egg counts (FEC; square root transferred values 9·2 v. 11·0±0·4 eggs/g fresh faeces, P&lt;0·01) than lambs grazing annual ryegrass swards. Similar dietary concentrations of condensed tannins (CT) between Yorkshire fog and annual ryegrass swards (4·2 v. 3·7 DM±0·2g/kg, P&lt;0·08) increased clean wool growth (1440 v. 1310±32 mg/cm per day, P&lt;0·05), fibre diameter (30·7 v. 29·5±0·21μ, P&lt;0·01) and liveweight gain (141 v. 120±4·3g per lamb per day, P&lt;0·01), although differences in carcass weight (17·9 v. 18·2±0·3kg) and FEC transformed values (9·6 v. 11·0±0·6 eggs/g fresh faeces) were not significant. The effects of CT on animal performance were greater in Yorkshire fog swards. CT had no significant effects on diet selection, herbage intake and grazing behaviour patterns.

Effects of variations in herbage mass, allowance, and level of supplement on nutrient intake and milk production of dairy cows in spring and summer

Two experiments examining the effects of herbage mass and herbage allowance on the consumption of nutrients by lactating dairy cows were conducted on irrigated perennial pasture swards in northern Victoria. Experiment 1 was conducted in early lactation (spring) with a perennial ryegrass (Lolium perenne L.)–white clover (Trifolium repens L.) sward at herbage masses of 3.1 (low) or 4.9 (medium) t dry matter (DM)/ha and herbage allowances of about 20, 35, 50 and 70 kg DM/cow.day. Within each herbage mass treatment, there were no significant differences between herbage allowance treatments in nutritive characteristics of pregrazing herbage. Daily DM intake increased linearly from 7.1 to 16.2 (low mass) or 9.9 to 19.3 (medium mass) kg DM/cow, as herbage allowance increased which was equivalent to 2.29 kg DM/t DM increase in herbage mass and 0.18 kg DM/kg DM increase in herbage allowance. This was associated with a decrease in utilisation of herbage from 35 to 23% and from 52 to 29%. Also, milk production increased linearly from 21.8 to 27.1 (low mass) or 24.7 to 32.0 (medium mass) kg/cow.day as herbage allowance increased. Experiment 2 was conducted in mid lactation (summer) with a paspalum (Paspalum dilatatum L.)-dominant sward at herbage masses of 3.0 (low) or 4.7 (medium) t DM/ha and herbage allowances of about 25 and 45 kg DM/cow.day and either 0 or 5 kg DM concentrate/cow.day. Within each herbage mass treatment, there were no significant differences between herbage allowance treatments in nutritive characteristics of pregrazed herbage. Daily DM intake increased by 0.13 kg DM for every 1 kg DM increase in herbage allowance. Over the 2 herbage masses, 2 herbage allowance treatments and 2 concentrate treatments, cows consistently selected a diet about 1.03 higher in in vitro DM digestibility and 1.24 higher in crude protein than that in the herbage on offer. Substitution rate increased from 0.20 to 0.42 (low mass) and from 0.34 to 0.44 (medium mass) kg DM reduction in herbage intake/kg DM of concentrates consumed, with increasing herbage allowance. Along with these changes, marginal returns to supplements decreased from 1.38 to 0.95 (low mass) and 1.07 to 0.97 (medium mass) kg milk/kg DM of concentrates with increasing herbage allowance. Dairy farmers should consider the effects of herbage allowance and herbage mass on intake, nutrient selection and milk production when allocating pasture to dairy cows. Herbage mass and allowance had a greater effect on intake in spring than in summer, principally due to the decline in nutritive characteristics that occurs in summer. Cows selected nutrients to varying degrees depending on the composition of the pasture sward and this selection may result in seasonal nutrient imbalances. Finally, it appears that the best use of supplements will occur when pastures are short in height because this will minimise substitution of supplement for pasture and maximise marginal returns in milk production.

A comparison of high nitrogen and clover based swards grazed by summer calving cows

The herbage intake of June/July calving cows in early lactation is limited by a number of factors including the quality of the sward. A typical management strategy is to graze dry cows at a high stocking rate at turnout to maximise the silage area and graze the freshly calved cows on silage aftermaths. A further refinement could be the use of clover rich swards. Winter feeding experiments have demonstrated that animals can eat more and perform better when offered a clover rich silage rather than a conventional silage. The following experiment was carried out to establish whether similar benefits would result from the grazing or clover rich swards.In a continuous design experiment lasting 12 weeks, sixteen summer calving British Friesian cows (mean calving date 7 June) were allocated to either a perennial ryegrass dominant sward (PRG) or a white clover rich sward (WC) silage aftermath. The target sward height was 7-10 cm measured by swardstick. Additional cows were available on a put and take basis to maintain parity between the sward heights in the two treatments.

Supplements improve the production of dairy cows grazing either white clover or paspalum-dominant pastures in late lactation

Summary. Thirty-six Friesian cows in late lactation, with an initial average daily milk yield of 15.4 kg/day, grazed pure white clover (Trifolium repens cv. Haifa) or paspalum (Paspalum dilatatum)-dominant swards for up to 6 weeks in autumn and were supplemented with maize (Zea mays) silage with or without barley grain, urea or cottonseed meal. Five groups of 4 cows were offered about 21 kg dry matter (DM)/cow. day of paspalum-dominant pasture. One group was unsupplemented while the other groups were offered one of the following supplementary feeding treatments: (i) 5 kg DM/cow of maize silage; (ii) 5 kg DM/cow of maize silage and 75 g of urea; (iii) 3 kg DM/cow of maize silage plus 2 kg DM of rolled barley; or (iv) 3 kg DM/cow of maize silage plus 2 kg DM of cottonseed meal each day. A further 4 groups of 4 cows were offered 21 kg dry matter/cow. day of white clover pasture, and the same supplement treatments, with the exception of maize silage–cottonseed meal. All cows were individually fed their supplement but they grazed the pastures as groups according to treatment. Cows offered white clover and no supplements ate 12.9 kg DM/cow.day of herbage and maintained milk production. All supplements increased total DM intake and improved milk production, to about 18 kg/cow. day, with a mean marginal response of 0.8 kg of milk per 1.0 kg of extra total DM eaten. There were no differences in production due to the type of supplement. Cows grazing paspalum ate less pasture, and levels of substitution of pasture by supplement were higher than when white clover was fed. Milk yields of the unsupplemented cows dropped rapidly and consistently with the cows virtually ceasing production. All supplements successfully arrested the decline in milk production, and to about the same degree; the marginal response to extra feeding was 1.4 kg of milk for each kilogram of additional total DM eaten.

The effect of grazing by cattle on animal performance and floristic composition in Nardus-dominant swards

The effect of grazing by cattle on animal performance and floristic composition in <i>Nardus</i>-dominant swards

Effects of fishmeal supplementation of baled grass and clover silages fed ad libitum to lambs

Sustainable clover dominant swards have been developed for upland UK sheep grazing conditions by sowing a mixture of tetraploid perennial ryegrass cv Condesa and small leaved clover cv Aberystwyth S184. These pastures have produced equal output to Condesa only swards given 150-160 kg N/ha/year. Lamb liveweight gain from April to August was increased by 50 g/day on the grass/clover vs grass swards. A comparison of the suitability of these grass/clover and N-fertilised grass only swards for silage was undertaken in order to assess silage yield potential and silage feeding value. The enhanced animal performance of lambs on clover has been partly attributed to the higher levels of dietary amino acid clover has been observed to provide. In order to quantify this effect sufficient supplementary fishmeal (60 g/day) to fully meet tissue N needs was fed to lambs on the grass/clover and grass silages and responses in lamb performance compared.