White Clover Pasture Research Articles

Soil dwelling macro-invertebrates in intensively grazed dairy pastures in Pennsylvania, New York and Vermont

This study estimates the relative contributions of environment and farm management strategies in influencing soil faunal assemblages and attempts to identify the species with potential to affect sustainability of intensive grazing management systems in the north-eastern USA. It arises because of the change from confinement feeding of dairy cattle, consequent upon concerns about negative environmental effects, the rising costs for machinery and housing, and reduced profit margins, together with the absence of data from which the consequences of such change on the soil fauna may be predicted. Macro-invertebrates were sampled in soil from seventy-eight grazed pastures on twenty-one dairy farms in Pennsylvania, USA, in the spring of 1994. On five of these farms, macro-invertebrates were sampled (four pastures per farm) in the spring, summer and autumn seasons of 1994, 1995 and 1996. In 1997, macro-invertebrates were sampled in soil during spring, summer and autumn from (four pastures per farm) on three farms in New York, and during spring and summer on three farms in Vermont. Species richness ranged from two to twelve species (mean 6·4) per pasture site in Pennsylvania and five to eighteen species (mean 10·7) in New York and Vermont. The communities were dominated at most sites by earthworms. Earthworms were correlated with soil basal and substrate-induced respiration/carbon ratio, and soil moisture, but were negatively correlated with cows per hectare and herbage biomass in Pennsylvania. Sitona larvae were recorded at nineteen of the twenty-one farms during the spring of 1994 across Pennsylvania and occurred at populations >5 m−2 in 68% of the sampled pastures. Sitona larvae were less abundant in New York and Vermont. Elaterid larvae comprised a complex of seven species of which Aeolus melillus (Say) and Melanotus communis (Gyllenhal) comprised 35% and 39%, respectively, of the elaterids collected in Pennsylvania. Agriotes mancus (Say) and Ctenicera destructor (Brown) comprised 41% and 26%, respectively, of four species collected in New York and Vermont. Scarabaeid larvae, comprising a complex of eight species, were detected at only 27% of the seventy-eight pastures sampled in spring 1994 in Pennsylvania. Five species were collected in ten of the twelve New York pastures and four species in nine of the twelve Vermont pastures. Populations of scarabaeid larvae averaged <25 m−2 in all three states, except in three Pennsylvania pastures in spring 1994. Detrended canonical correspondence analysis (DCCA) showed pasture standing biomass, legume diversity, pre-winter stubble height, white clover pasture content, and soil phosphorus levels influenced numbers of invertebrate species more than climatic factors, such as temperature, rainfall, altitude, latitude and seasonal water table. DCCA also showed most pastures to be close to the average of environmental factors. The extremely low density of herbivorous macro-invertebrates in soil and the absence of pest outbreaks may indicate a stable soil ecosystem.

The effects of forage supplements on the ingestive behaviour and production of dairy cows grazing ryegrass only or mixed ryegrass and white clover pastures

AbstractThe effects on milk yield and feeding behaviour of offering ryegrass silage (r), ryegrass and white clover silage (c), or grass hay (h) supplements were examined for cows grazing a ryegrass pasture (R) or a ryegrass and white clover pasture (C). The chemical composition of the two silages was similar but the hay contained less crude protein. Cows grazing R pasture spent longer feeding on c than r silages, and those consuming the c silage spent less time grazing than those consuming r silage. The cows grazing the C pasture spent longer feeding on r than c silages, and those consuming the r silage spent less time grazing than those consuming c silage. The cows’ intake of hay dry matter (DM) was less than silage DM and it was taken into the mouth at a slower rate, masticated more ana swallowed less frequently than silage. Milk yield and composition were not affected by the type of supplementary forage or pasture type. Thus cows grazing pastures of the two sward types spent longer feeding on forages with dissimilar botanical composition if given the option. However, as this reduced the time that they spend grazing, there was no effect on milk production.

Caucasian clover/ryegrass produced more legume than white clover/ryegrass pastures in a grazed comparison

The potential of caucasian clover to improve the legume content of lowland New Zealand pastures should result in enhanced animal performance. Liveweight gains from eight flocks of ewe lambs rotationally grazing irrigated ryegrass pasture with caucasian or white clover at two levels of soil fertility (Olsen P values 10 or 22) were compared during years 2 (1998/1999) and 3 (1999/2000) of an ongoing grazing experiment in a lowland environment. Clovers were sown in December 1996 and ryegrass in March 1997 into the pure clover swards. Lamb liveweight gains were similar in year 2 (1130 kg/ha/yr), but in year 3, gains were greater on pastures sown with caucasian than on those sown with white clover (1290 vs. 1110 kg/ ha/yr). Spring liveweight gains per head per day averaged 170 g/hd/d in year 2, and in year 3 were greater from caucasian than white clover pasture (180 vs. 160 g/hd/d). Caucasian clover pastures had more legume on offer than pastures sown with white clover in year 2 (26% vs. 17%) and year 3 (19% vs. 12%). In year 3, 39% of the total legume on offer in caucasian clover pastures was volunteer white clover. Soil fertility had little influence on results. Early years of this grazing experiment showed that caucasian clover can establish as well as white clover if sown alone, and that sowing caucasian clover can result in lowland pastures with an increased total legume content which may improve liveweight gains. Keywords: legume content, Lolium perenne, pasture production, sheep liveweight gain, Trifolium ambiguum, T. repens

The grazing value of tall fescue (Festuca arundinacea) and phalaris (Phalaris aquatica) for sheep production in the northern tablelands of New South Wales

The grazing value of phalaris–white clover and tall fescue–white clover pastures was compared in a temperate summer-rainfall environment in the high rainfall zone of eastern Australia. Data were derived from an experiment which evaluated pasture cultivars when grown in binary mixtures and grazed by sheep. The data were also simulated with the decision support system SheepO (Version 4.0) and validated by visual techniques, deviance measures, and statistical tests. The model generally simulated green biomass, liveweight gain, and clean fleece weight with acceptable accuracy. Pasture based on tall fescue–white clover produced more green pasture biomass in all seasons, in all years, and at both low (10 sheep/ha) and high (15 sheep/ha) stocking rates when compared with phalaris–white clover. Sheep grazing tall fescue–white clover pasture were turned off about 5 kg heavier each year and produced about 0.6 kg/head more clean fleece weight; the wool production per head of sheep grazing tall fescue–white clover at 15 sheep/ha was similar to that for sheep grazing phalaris–white clover pasture at 10 sheep/ha. These differences in wool production were accompanied by consistent effects on wool quality; the fleeces of sheep grazing tall fescue–white clover pasture were markedly sounder in tensile strength but broader in fibre diameter. These data and the SheepO simulations highlight the potential for pasture cultivars with enhanced seasonal growth and nutritive value to alleviate feed-gaps and improve the feed-base for grazing animals.

Caucasian clover was more productive than white clover in grass mixtures under drought conditions

This experiment compared the productivity of caucasian or white clover when established with five perennial grass species over 6 years in a dry lowland environment. Hexaploid 'Endura' caucasian clover or 'Grasslands Demand' white clover were sown in December 1994 with high endophyte 'Yatsyn' perennial ryegrass, 'Grasslands Wana' cocksfoot, 'Grasslands Advance' tall fescue, 'Grasslands Gala' grazing brome, or 'Grasslands Maru' phalaris into a deep, fertile silt loam. Initial establishment of clovers was poor with ryegrass and grazing brome. Some volunteer white clover established in all 10 treatments. After the first 14 months, no irrigation was applied over the following 4 years. Sheep grazed plots about six times each year. The legume cover in 15-month-old pastures was higher when sown with white clover (29%) than caucasian clover (21%) but dry conditions during 1997/1998 (60% of 680 mm mean annual rainfall) and 1998/1999 (66% of mean rainfall) decreased the percentage of legume in white clover pastures. In February 1998 and March 1999, legume contributed 37% and 21% of the dry matter (DM) in caucasian clover pastures, but only 4% and 1% in pastures sown with white clover. Rainfall during the sixth season (1999/2000) was more favourable (111% of mean rainfall). Total DM production from July 1999 to June 2000 was 10.0 t DM/ha from caucasian clover pastures and 8.7 t DM/ha from pastures sown with white clover. The mean proportion of legume in white clover pastures ranged from 9% when sown with ryegrass and phalaris to 1% with cocksfoot. In contrast, mean caucasian clover legume contents were similar across all grass treatments at 20%, but reached 46% with cocksfoot during summer. It was concluded that caucasian clover is more tolerant of summer moisture stress than white clover when in association with perennial grass species. Keywords: botanical composition, Bromus stamineus, Dactylis glomerata, legume content, Lolium perenne, moisture stress, pasture production, Phalaris aquatica, Schedonorus phoenix syn. Festuca arundinacea, Trifolium ambiguum, T. repens

Effect of macropore flow on the transport of surface-applied cow urine through a soil profile

A field lysimeter experiment was conducted to determine the effect of macropore flow on the transport of surface-applied cow urine N through soil. The lysimeters (500 mm diameter by 700 mm depth) used for this experiment were collected from Templeton fine sandy loam soil (Udic Ustochrept), which had been under ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) pasture for 9–10 years. The effect of macropore flow on urine-N leaching was determined by leaching experiments under 0.5 kPa and 0 kPa water tensions (suctions) imposed on top of the lysimeter using a disc tension infiltrometer. The 0.5 kPa suction prevented soil pores &gt;600 µm diameter from conducting water and solutes, while the 0 kPa suction allowed conduction under ‘field saturated’ condition. Pores &gt;600 µm diameter transmitted about 98% of the total nitrogen (N) leached below 700 mm depth. The main form of N transmitted under 0 kPa was ammonium (NH4 -N), accounting for 10.5% of the total N applied at 0 kPa suction. This was significantly higher than the amount of NH 4 -N leached at 0.5 kPa suction, which accounted for 0.17% of N applied. The urea-N in the leachate reached 16 mg/L at 0 kPa suction, and accounted for 1.6% of the total N applied. No urea was detected in the leachate at the 0.5 kPa suction. The concentrations and amounts of nitrate (NO3 -N) leached were very low and did not differ between the two suctions. The forms and amounts of N leached were affected by the interactions of macropore flow and N transformations in the soil, and the environmental conditions during the two leaching events. From this work, it is recommended that stock should be removed 1–2 days before irrigation water is applied as this will allow animal urine to diffuse into soil micropores and thus decrease N leaching by macropore flow.

Productivity of Kentucky Bluegrass Pasture Grazed at Three Heights and Two Intensities

Sward height before grazing and amount of forage harvested affect production, composition, and utilization of rotationally stocked pasture. In this 3‐yr field study, yearling steers (Bos taurus L.) grazed 400‐m2 plots of Kentucky bluegrass (Poa pratensis L.)–white clover (Trifolium repens L.) pastures every time sward height reached either 11.8 cm (short), 13.7 cm (medium), or 15.3 cm (tall). Plots were grazed with enough steers to remove either 50 or 60% (grazing intensity) of the herbage mass in 4 h. The experimental design was a 3 × 2 (height treatment × grazing intensity) factorial with four replications. Sward heights before and after grazing periods were measured. Herbage mass, apparent growth rate, herbage removed, rejected area, and percent utilization were calculated. Average herbage mass before grazing ranged from 1855 to 2350 kg dry matter (DM) ha−1. Average herbage mass after grazing varied from 855 to 1060 kg DM ha−1. Apparent herbage growth rate (54 kg DM ha−1 d−1) and herbage removed (7520 kg ha−1) were highest on the short height treatment with low grazing intensity (50% removal). Assuming a sigmoidal growth curve, maximum apparent growth rate occurred at 10.5‐cm sward height. More than twice as much herbage was removed in the wettest year compared with the driest. In the dry year, height and intensity of grazing had little effect on herbage production. Thus, the benefits farmers can expect from more intensive grazing management will be more evident in a year of good growth.

Effects of feeding additional pasture hay in autumn to dairy cows grazing irrigated perennial ryegrass-white clover pasture and supplemented with barley grain

Two experiments were undertaken to investigate responses by dairy cows grazing irrigated perennial pastures in autumn to supplementation with barley grain and pasture hay. Cows in late lactation were offered limited amounts of perennial ryegrass–white clover pasture at 26 kg DM/cow. day. Supplements were offered as nil or 6.0 kg DM/cow.day plus perennial pasture hay at 0, 0.5, 1.2, 2.0 or 3.0 kg DM/cow. day in a replicated experiment with 6 treatments using 36 cows (3 cows/treatment replication). The second experiment, which was conducted concurrently with experiment 1, measured aspects of rumen function and blood parameters in 3 groups of 3 rumen fistulated lactating cows grazing at the same herbage allowance and supplemented with barley (6.0 kg DM/cow. day) and 0, 1.0 or 3.0 kg DM of pasture hay daily. The in vitro DM digestibility and crude protein and neutral detergent fibre content of the barley and perennial pasture hay was 863 and 640 g/kg DM, 134 and 87 g/kg DM and 192 and 615 g/kg DM, respectively. In experiment 1, the cows from all treatments consumed herbage (mean s.d.) with an in vitro DM digestibility of 811 21.8 g/kg DM, crude protein content of 233 26.0 g/kg DM and neutral detergent fibre content of 404 39.4 g/kg DM compared with the pregrazed herbage on offer of 710, 152 and 526 g/kg DM, respectively. The mean pregrazing herbage mass of 3.75 t DM/ha in experiment 1 consisted of perennial ryegrass (580 g/kg DM), white clover (100 g/kg DM), weeds (110 g/kg DM) and dead material (210 g/kg DM). Without supplements, cows consumed 10.0 kg DM/day of this pasture with a neutral detergent fibre intake of 4.43 kg/day. The herbage grazed in experiment 2 was similar. Herbage intake did not decline to a large degree when barley was included in the diet indicating a very low substitution rate under the prevailing conditions where herbage allowance was only 26 kg DM/cow. day. Inclusion of hay progressively decreased (P&lt;0.05) herbage intake, with substitution averaging 1.2 kg DM of herbage/kg DM of hay. Total DM intakes (15.5 kg DM/cow. day) were similar for the barley and the barley plus hay treatments up to 2.0 kg DM hay/cow. day; total DM intake was higher (P&lt;0.05) for the 3.0 kg hay treatment. Milk production increased (P&lt;0.05) with grain and hay supplementation, the marginal response being 0.8–1.0 kg milk/kg DM supplement, however, there was no significant difference between the 5 supplemented treatments. Supplementation with hay had no significant effect (P&gt;0.05) on milk fat or milk protein contents which averaged 44.6 and 35.2 g/kg milk, respectively. The ratio of acetate + butyrate:propionate was 4.1:1 when cows consumed 6.0 kg barley, which was around the critical ratio of 4:1 for milk fat of 40 g/kg. Increasing the amount of hay in the diet did not alter this ratio. Because of the high levels of substitution of hay for pasture, changes in neutral detergent fibre intake were small between supplemented treatments. The rumen pH, ammonia-N concentration and volatile fatty acid concentration were relatively stable during the day because of a relatively slow rate of eating (1.5 kg DM/h) and long rumination time (about 6.8 h/day). Ruminal pH was rarely below 6.0, even when barley was given alone, suggesting that fibre digestion was not compromised. Additional fibre as supplemental hay to cows in late lactation grazing irrigated pasture did not improve milk production when the neutral detergent fibre content of the diet was above an average of 336 g/kg DM. Use of hay as a means of providing additional fibre could reduce herbage utilisation.

Quantifying the sustainability of grazed pastures on the Northern Tablelands of New South Wales

An experiment was conducted to examine the effect of deep-rooted perennial grasses on the water and nitrogen economy of 3 mature pasture communities with different botanical compositions but the same fertiliser history. One pasture was dominated by volunteer naturalised pasture grasses (Eleusine tristachya and Danthonia spp.) (termed ‘degraded’), another was phalaris (Phalaris aquatica) dominant (phalaris), and a third was dominated by phalaris into which white clover (Trifolium repens) had been recently sown (phalaris–white clover). Two replicates of each pasture type were grazed continuously over 4 years with young weaner sheep changed each year. Measurements of hydrology, nutrient cycling, botanical composition and animal production were made in order to quantify the sustainability characteristics of each of the pasture types. Data are summarised as absolute measures at various points in time and also as trends over time. The ranking of standardised treatment measures was then summed to provide an index of sustainability with or without a weighting assumed to be representative of the relative importance of various layers of sustainability viewed from the perspective of a hypothetical ‘typical’ grazier. The results show that the phalaris–white clover treatment was substantially more sustainable, in both ecological and economic terms, than either of the other treatments. The unweighted index for the phalaris–white clover pasture was 3.61 compared to 2.08 and 1.98 for the phalaris and ‘degraded’ pastures, respectively.

The effect of grazing Lotus corniculatus during late summer - autumn on reproductive efficiency and wool production in ewes

A grazing experiment was conducted at Massey University (Palmerston North, New Zealand) over 80 days in the late summer–autumn of 1998 (9 February–29 April). Reproductive performance and wool growth of ewes grazing on Lotus corniculatus (birdsfoot trefoil) were compared with those of ewes grazing perennial ryegrass–white clover pasture. A rotational grazing system with 210 mixed-age dry ewes (59.80.9 kg/ewe) was used, with 80 ewes grazing pasture [1 g of condensed tannin (CT) per kg dry matter (DM)] and 130 ewes grazing L. corniculatus (24 g CT/kg DM). Half of the ewes grazing L. corniculatus were supplemented orally, twice daily, with polyethylene glycol (PEG; MW, 3500) to inactivate the CTs. The effect of forage species and PEG supplementation on voluntary feed intake (VFI), reproductive performance (as measured by ovulation rate), and wool production was measured during 4 synchronised oestrous cycles. The ewes were restricted to maintenance feeding during the first 10 days of each oestrous cycle and then increased to ad libitum for the 6 days leading up to and including ovulation. In vitro organic matter digestibility in the selected diet was higher for lotus than for pasture (0.80 v. 0.76), with L. corniculatus containing less nitrogen than pasture (36.5 v. 40.8 g/kg organic matter). Ewes grazing on L. corniculatus produced 11% more wool and had an ovulation rate up to 14% higher than ewes grazing pasture, with neither parameter being affected by PEG supplementation. Higher mean ovulation rates of ewes grazing L. corniculatus were due to increases in fecundity (multiple ovulations/ovulating ewe; P &lt; 0.05), with no effect on ewes cycling/ewes mated. Three cycles of grazing on L. corniculatus were required to achieve the maximum response in multiple ovulation, but most of this was achieved after 2 cycles. As the VFI of ewes grazing on L. corniculatus was not greater than that of ewes grazing pasture, the greater wool production and higher ovulation rate of ewes grazing this forage was due to improved efficiency of feed utilisation. It was concluded that feeding ewes L. corniculatus increased the efficiency of both reproduction and wool production without increasing VFI.

The specificity of arbuscular mycorrhizal fungi in perennial ryegrass–white clover pasture

For nitrogen to be transferred from a legume to grass through hyphae of arbuscular mycorrhizal fungi (AMF), as reported for a number of grass/legume combinations, the two species should be linked by a common hyphal network, which gives rise to the question of host–fungus preference. To examine the relative preference of perennial ryegrass and white clover for co-existing AMF, two experiments, adopting a ‘spreader–receiver’ system, were carried out in a glasshouse. Both experiments demonstrated quantitative host preference by perennial ryegrass and white clover for AMF associated with their own rhizospheres. However, the effect seemed to be temporal, as, by Week 17, in Experiment 2, AMF not associated with the roots of the spreader may have had an opportunity to infect the receiver. Differences in the population of AMF spores around the roots of the two plant species also suggest differences in preference by the two hosts. The study confirms that white clover is more highly mycotrophic than grass. It is concluded that quantitative differences in preference by perennial ryegrass and white clover for specific AMF may reduce the ecological and agricultural significance of N transferred from clover in the field compared with laboratory estimates.

White clover growth patterns during the grazing season in a rotationally grazed dairy pasture in New York

White clover (Trifolium repens L.) is an important stoloniferous pasture legume in the Great Lakes region of the United States, but it often has limited persistence. Researchers in New Zealand and Wales have found that in spring, compared with other seasons, white clover plants have reduced branching complexity and have the fewest buds that produce leaves. They therefore suggested that in spring the plants are most vulnerable to grazing and climatic stress.Because of severe winter and cool, wet spring weather in New York State, it was hypothesized that white clover plants would also be of low branching complexity, smaller and have low axillary bud activity in spring compared with later in the grazing season. To test this, growth of white clover was monitored in an orchard grass (Dactylis glomerata L.)/white clover pasture in New York that was rotationally grazed with dairy cows during the 1993 and 1994 grazing seasons.Three sets of plants were sampled. The first set consisted of forty random plants sampled before each grazing event. Stolon branching order, number of each stolon branching type and area the plant occupied were determined. Approximately each month before one grazing event, a separate set of 32 random plants was measured in the field to determine the area they occupied; these plants were then removed to the laboratory for the measurement of stolon order, number of each stolon type, stolon lengths, total number of growing points, number of taproots and adventitious roots, root position and above‐ground dry matter. Once a month, 12 additional plants were removed to measure axillary bud activity at each node.Leaf development from nodes tended to increase from spring to summer. However, the stolon branching order of white clover plants was not simpler in spring compared with summer or autumn. In 1994 during and after a dry and hot period, white clover plants were smaller, of lower stolon branching order and had fewer roots. Climate and associated soil organism activity appear to explain the different white clover growth patterns observed in New York and New Zealand. Severe winters in New York limit earthworm activity and stolon burial, which is important in contributing to stolon/plant breakdown in New Zealand. During the years of this study in New York, a hot and dry period had the most negative effect on the growth pattern of white clover.

Effect of sward surface height on herbage intake and performance of finishing beef cattle

This study examined the effects of contrasting sward surface height (SSH) on the herbage intake, ingestive behaviour, and performance of steers grazing perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) pastures in New Zealand during summer, and the influence of this initial treatment contrast on subsequent cattle performance under common grazing conditions during early autumn. Twenty‐four Angus‐cross steers, 26 months old and with an initial liveweight of 522 ± 7.6 kg, were continuously stocked on swards maintained at SSH of 5 and 10 cm (L versus H) from 18 November 1996. Six steers from each treatment were slaughtered on 4 March and the remaining animals were grazed for another 5 weeks on common pastures until the final slaughter on 8 April 1997. Herbage intake (estimated by the n‐alkane technique) and liveweight gain over the SSH contrast period, and carcass weight at first slaughter, were higher for steers grazed at 10 cm than for those grazed at 5 cm (7.5 ± 0.21 versus 5.0 ± 0.18 and 7.8 ± 0.38 versus 5.0 ± 0.33 kg DM d−1 from two intake estimates, P < 0.05 for each comparison; 1.10 ± 0.23 versus 0.32 ± 0.21 kg d−1, P < 0.01; and 332 ± 10.6 versus 287 ± 7.5 kg, P < 0.05, respectively). SSH did not affect carcass or meat quality characteristics. Liveweight and carcass weight gain per hectare were 71 % and 43% greater (318 versus 186 kg and 166 versus 116 kg over 105 days) for steers grazing at 10 cm despite the lower stocking rate (2.86 versus 5.80 steers ha−1) maintained by the tall swards. Significant differences in carcass weight were still evident at the end of the compensatory period between the steer groups originally on treatments H and L (335 ± 9.4 versus 297 ± 9.4 kg, P < 0.05). These results suggest that maintaining a sward height of 10 cm offers advantages in terms of individual animal output and output per hectare compared with grazing at 5 cm, and that compensatory growth does not seem to be an important phenomenon in heavy (over 500 kg liveweight) finishing steers.

Effect of milking frequency and pasture intake on milk yield and composition of late lactation cows.

Twenty-four monozygous twinsets in late lactation (> 210 d in milk) were used to examine the effects of feed restriction and milking frequency prior to drying off on milk yield and composition in a pastoral dairying system. Cows were assigned to one of four treatment groups for 26 d and were milked either twice or once daily and given either unrestricted or restricted access to feed. Dry matter intakes averaged 16 or 8 kg per cow per day, and diets comprised ryegrass and white clover pasture supplemented with 15% pasture silage. Feed restriction and once daily milking reduced milk yield and increased concentrations of milk fat and protein. Somatic cell count was increased by feed restriction only. Production losses caused by feed restriction were nearly threefold higher than were those for once daily milking. Yields of components that were mammary synthesized and serum derived were reduced by feed restriction, in accordance with milk volume reduction. Plasma lactose concentration increased with once daily milking only and indicated enhanced permeability of mammary tight junctions. Both feed restriction and once daily milking compromised milk quality, but increased leakage of serum components into milk via mammary tight junctions was deemed to occur only for once daily milking.

The effects of methionine supplementation upon milk composition and production of forage-fed dairy cows

Two experiments (mid- and late lactation) were conducted to test whether methionine (Met) limited milk production in Friesian cows fed sole diets of fresh perennial ryegrass–white clover pasture. In mid-lactation (exp. 1), 26 cows were assigned to one of three treatments: ruminally protected oral DL-Met (15 g d−1), continuous intrajugular infusion of L-Met (15 g d–1) and control. Twelve animals from exp. 1 were used during late lactation (exp. 2) and distributed in two experimental groups: ruminally protected oral DL-Met (15 g d−1) and control. Dry matter, metabolizable energy, crude protein and Met intakes, milk yield and composition and blood Met, cysteine and urea were measured. Oral and intravenous Met supplementation increased blood Met concentration by 50–90% compared with controls. Met supplementation did not alter the concentration of milk fat, protein or lactose in either experiment. Met supplementation had no significant effects on yields of fat, lactose, casein, whey proteins or non-protein nitrogen during mid-lactation. In late lactation, Met supplementation did not affect milk protein composition or yield of milk components, with exception of a decrease (P &lt; 0.05) in the yield of β -casein. Intravenous Met supplementation increased (P &lt; 0.05) the efficiency of conversion of pasture N to milk protein in mid-lactation. Key words: Dairy cows, methionine, ruminally protected methionine, milk protein, casein, fresh pasture diets

Growth and carcass production of young farmed deer grazing sulla (Hedysarum coronarium), chicory (Cichorium intybus), or perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) pasture in New Zealand

Liveweight gain, voluntary feed intake, and carcass production were compared for pure red and hybrid (0.75 red: 0.25 elk) deer calves grazing sulla (Hedysarum coronarium cv. Necton), chicory (Cichorium intybus cv. Grasslands Puna), or perennial ryegrass (Lolium perenne cv. Nui)/white clover (Trifolium repens cv. Huia) pasture from weaning in March to slaughter in December of the same year, at approx one year of age. Organic matter digestibility (OMD) of diet selected was similar for all forages during autumn, but OMD of chicory (88.4%) was greater than both sulla (78.3%) and pasture (83.8%) during spring (P < 0.05). Sulla diet selected contained 5.1% condensed tannin (CT) in autumn and 8.4% CT in spring (P < 0.05); pasture and chicory contained 0.14–0.26% CT. VFI of deer grazing sulla was greater than for deer grazing chicory in autumn (2027 versus 1014 g OM d−1; P = 0.07), but not spring (2029 versus 2251 g OM d−1). In autumn, deer gained 293 g d−1 on sulla, 218 g d−1 on pasture (P < 0.01), and 183 g d−1 on chicory (P < 0.001). In winter, deer gained 150 g d−1 on sulla and 133 g d−1 on pasture. Final liveweight of deer grazing sulla was 106 kg, which was significantly higher than 97 kg for deer on pasture or 95 kg for deer on chicory (P < 0.01). Deer grazing sulla had greater carcass weights (59.9 kg) than deer grazing pasture (52.3 kg) or chicory (52.1 kg) (P < 0.01 hinds; P< 0.05 stags). Hybrid stags had significantly greater carcass weights than red stags (64.1 kg versus 56.3 kg; P < 0.01) and hybrid hinds (52.8 kg; P < 0.001). It was concluded that the increased growth and carcass weight of young deer grazing sulla was caused by a higher feeding value of sulla, with a component of this being increased utilisation of digested nutrients.

A lysimeter study of the impact of cow urine, dairy shed euent, and nitrogen fertiliser on nitrate leaching

The effect of cow urine, dairy shed effluent (DE), and urea fertiliser on nitrate leaching was determined using undisturbed soil lysimeters (500 mm diameter by 700 mm deep) with ryegrass (Lolium perenne)–white clover (Trifolium repens) pasture. Cow urine was applied to the lysimeters, at rates of 0 and 1000 kg N/ha in May 1996. Urea and DE were applied to urine-applied and non-urine-applied lysimeters at rates of 0, 200, and 400 kg N/ha in 4 split equal applications in May, August, and November 1996 and February 1997. Natural rainfall was supplemented with simulated rainfall in winter and spring (May–October) to achieve the 75th percentile of winter–spring rainfall records in the region. Flood irrigation was applied 6 times during summer–autumn (November–April) at 100 mm per application, which is a typical practice used by dairy farmers in the region. Drainage water was collected and analysed for nitrate, nitrite, bromide (added tracer), and ammonium. Over the first year of the experiment (May 1996–April 1997), 12% of the urine-N applied was lost through leaching, mainly in nitrate form. When urine (1000 kg N/ha) was applied in combination with DE (200 kg N/ha) and urea (200 kg N/ha), the mineral N leaching loss increased to 14% of the total N applied. The annual average nitrate concentrations in the drainage from the lysimeters that received urine alone, or urine+DE and/or urea, were 33–57 mg N/L, with a mean peak concentration of 110 mg N/L. These nitrate concentrations were significantly higher than in those treatments that did not receive urine (1–5 mg N/L). Because, on average, about 25% of the area of a grazed dairy paddock receives urine per year, the field-scale leaching losses were calculated by taking into account the dilution effect of drainage water from non-urine patch areas of the paddock. The calculated annual paddock losses were 33–60 kg N/ha, and on average the annual paddock nitrate concentrations were 10–17 mg N/L. This demonstrates the importance of accounting for the dilution of nitrate in the leachate from non-urine patch areas of the paddock. The annual average concentration from the treatment DE at 400 kg N/ha was significantly lower than that from the urea treatment at the same rate. This was probably because of the different chemical forms of N in each material, and needs to be taken into account when developing regional rules for land application of urea and effluents.

Effect of rate and time of nitrogen application from autumn to midwinter on perennial ryegrass - white clover dairy pastures in western Victoria. 1. Growth and composition

Field experiments were carried out at 2 sites to study the effects of time and rate of nitrogen (N) application from autumn to midwinter on perennial ryegrass–white clover pasture dry matter (DM) yield and species composition. Nitrogen (0, 15, 25, 30, 45, and 60 kg/ha) was applied in mid-April, early May, mid-May, early June, and mid-June 1996 onto a grazed pasture. Dry matter yield was estimated when perennial ryegrass in the 45 kg N/ha treatment reached the 3-leaf stage of development. Species composition estimates were made on all plots in autumn, late winter, and late spring (November). Asecond DM yield estimate was taken one regrowth cycle after the primary DM yield estimate to determine residual N impact on pasture growth, and then the pastures were returned to the grazing routine of the farm. Increasing levels of N fertiliser resulted in a linear (Site 1) and curvilinear (Site 2) primary DM yield response. Residual DM yield responses were linear at both sites. The highest primary DM yield response at Site 1 was 9.1 kg DM/kg N (mid-April application), whereas the highest residual N response was 9.4 kg DM/kg N (mid-May application). The time taken for the 45 kg N/ha treatment to reach the 3-leaf stage of development ranged from 38 (early June application) to 47 (mid-April application) days for the primary harvest, and from 46 (early May application) to 72 (early June application) days for the residual harvest. At Site 2, the highest primary DM yield response to N was 15.8 kg DM/kg N at 45 kg N/ha (mid-April application), whereas the highest residual N response was 8.3 kg DM/kg N (mid-June application). The time taken for the 45 kg N/ha treatment to reach the 3-leaf stage of development ranged from 24 (early June application) to 36 (mid-April and early May applications) days for the primary harvest, and from 30 (mid-April) to 57 (early June application) days for the residual harvest. Based on the current cost of urea, the study concluded that N fertiliser use during autumn to midwinter is economically viable for dairy farmers. Botanical composition was unaffected by N application. There were no treatment effects on botanical composition of the sward at either site the following spring (November). It is concluded that a ‘once-off’ strategic N application up to 60 kg N/ha during autumn to midwinter is not likely to influence dairy pasture composition in western Victoria.

Influence of single applications of nitrogen on white clover nitrogen fixation in autumn and winter dairy pastures in south‐west Victoria, Australia

Effects of nitrogen (N) (0, 15, 30, 45 and 60 kg N ha−1) applied at five different times during autumn and early winter on the N fixation of Trifolium repens L. (white clover) in Lolium perenne L. (perennial ryegrass) / white clover pastures were examined (Experiment 1). Effects of applying different N fertilisers (e.g. urea and ammonium nitrate) at 45 kg N ha−1 in autumn, with and without phosphorus (P), potassium (K) and sulphur (S) on N fixation were also tested (Experiment 2). In Experiment 1, percentage N derived from the atmosphere (percent Ndfa) by white clover varied between 87% and 91% in the period after (24 to 36 days) N application. Increasing rates of N and time of application did not influence percent Ndfa. The amount of N fixed by white clover ranged from 0.8 to 3.7 kg N ha−1 in the period after N application. Increasing rates of applied N produced a significant (P<0.05) linear increase in the amount of N fixed. In Experiment 2, percent Ndfa and amount of N fixed (1.9 to 4.1 kg N ha−1) were unaffected by different N fertilisers, with and without P, K and S, in the period after (37 days) fertiliser application. For both experiments, fertiliser N increased dry matter yield while having no effect on white clover composition. It is concluded that single applications of N during the autumn and early winter benefit pasture growth without adversely affecting white clover N fixation or clover composition. This finding, however, will require further investigation.

Seasonal and lactational influences on bovine milk composition in New Zealand.

This study was designed to evaluate the respective influences of stage of lactation (SOL) and time of year on the seasonal variation in milk composition for pasture-fed dairy cows in New Zealand. Four herds of approximately 20 Friesian cows were used, one herd calving in a 6 week period beginning in each of January, April, July and October. Cows grazed rye-grass-white clover pasture only, except during June when all cows received supplementary pasture silage. Milk samples were collected from each cow in milk on four occasions during the year (September, December, March and June), to give a total of three samples per cow (early, mid and late lactation; about 30, 120 and 210 d respectively after calving). Samples were analysed for a detailed range of components. Concentrations of many milk components (e.g. total protein, fat, casein and whey protein) increased as lactation progressed; the extent of these increases depended on the time of year. These results indicated that spreading calving throughout the year would lessen seasonal variations in the gross composition of mill supplied to factories, leading to a more even distribution of product yield across the year. Despite this, variations in some important manufacturing properties were affected by time of year but not by SOL. Ratios of protein: fat and casein: whey protein were not significantly affected by SOL, but were affected by time of year. The solid fat content of milk was also affected by time of year. Seasonal variations in the manufacturing properties of milk may be reduced but not eliminated by changing the time of calving.