Perennial Ryegrass Pasture Research Articles

Effect of calcium salts of fatty acids and calcium salt of methionine hydroxy analogue on reproductive responses and milk production in Holstein-Friesian cows

AbstractThe effects of a dietary supplement with calcium salts of fatty acids and methionine hydroxy analogue on reproductive performance, blood metabolites, milk production, milk composition, body weight and body condition score was studied in lactating dairy cows. Autumn-calving, Holstein-Friesian cows (no. = 162) were assigned 1 week post calving to one of two diets: (1) unsupplemented maize-silage-based complete diet while housed before turn-out to perennial ryegrass pasture and (2) the same diet with 400 g per cow per day of a supplement with calcium salts of long-chain fatty acids and methionine hydroxy analogue (Megalac Plus, Volac Ltd). Eleven cows were removed from the study following randomization for reasons not related to the experiment leaving 151 cows on dietary treatments. The diets were offered until the end of the 18-week breeding period. Cows receiving supplement had higher milk yield and milk lactose production and lower milk protein and milk fat proportion (P < 0·05). Body weight and body condition scores were not different between treatments in the first 20 weeks of lactation (P > 0·05). Overall reproductive performance was not different between dietary treatments (P > 0·05). However, first lactation animals (no. = 33) receiving the dietary lipid and methionine supplement tended to have increased conception rates to first and second service (P < 0·09) which resulted in a shorter calving-to-conception interval in those animals (P < 0·06). Services per conception (P < 0·08), services per cow served (P < 0·05) and services per conception for pregnant cows (P < 0·05) in first lactation animals was reduced in the supplemented group. Although plasma cholesterol concentrations were increased following lipid and methionine supplementation (P < 0·01), plasma progesterone concentrations on day 5 and day 8 after artificial insemination were not different between dietary treatments (P > 0·05). In conclusion, a dietary supplement of calcium salts of fatty acids and methionine hydroxy analogue increased milk yield, milk lactose production and blood cholesterol concentration but did not improve reproductive performance, except in first lactation cows.

Minimising endophyte contamination from ryegrass seed in cow dung

Perennial ryegrass pastures in New Zealand are usually established from seed naturally infected with the wildtype endophyte. New pastures can now be sown with perennial ryegrass that has no endophyte or has been infected with a new endophyte. Cows can contaminate pastures by consuming ryegrass seed infected with the wild-type endophyte on old pastures, and transferring the seed in their dung onto new pastures. A quarantine period before grazing new pastures may allow cows to eliminate wild-type endophyte-infected perennial ryegrass seed from their digestive tract, preventing contamination from this source. A trial was run at Dexcel, Hamilton, to define an appropriate quarantine period. Cows grazed wild-type (high endophyte) ryegrass pastures containing seedheads for 4 days before grazing Lotus corniculatus (quarantine pasture) for a further 4 days. This procedure was repeated five times from November 2000 to April 2001. Dung samples were collected daily after shifting cows off high endophyte ryegrass. Pastures contained viable ryegrass seed on seedheads from December to April, and ryegrass seedlings germinated in dung samples collected from January to April. Viable endophyte-infected perennial ryegrass seed was present in dung for 2 days after removal from the seed source, with 0.8% of the seed eaten remaining viable. Ryegrass seed endophyte viability was reduced from 100% to 40% after passage through the digestive tract of the cows. It is recommended that cows do not graze endophyte-free pastures or those sown with ryegrass containing a new endophyte for at least 2 days after grazing high endophyte ryegrass pastures containing ryegrass seedheads. Keywords: dairy cows, dung, perennial ryegrass, ryegrass endophyte, seedheads, seed transfer

Effect of synthetic windbreaks on pasture growth in south-western Victoria, Australia

The impact of a synthetic windbreak on the growth of subterranean clover and perennial ryegrass pasture in the cool-temperate zone of south-western Victoria was investigated over 2 years. Four square plots (10 m sides) at each of 2 sites were fenced with wire mesh 1.2 m tall in 1996 and 1997. Two plots at each site were sheltered with synthetic mesh of 50% porosity attached to the wire mesh. The open wind speed averaged 3.6 m/s in 1996 and 3.1�m/s in 1997. Winds exceeded 6 m/s for 4–23% and 2–8% of the time in 1996 and 1997, respectively. There were small but significant differences in temperature between the sheltered and open plots. The mean daily temperature was 0–0.4°C warmer with shelter. Temperatures in the shelters were always higher from 0900 to 1800�hours, the differences ranging from 0.1 to 0.9°C. Conversely, lower temperatures (a maximum difference of 0.4°C) usually occurred in the shelters from 1800 to 0600 hours. The mean daily relative humidity was 1.4–3.1% greater in shelter than in the open and the maximum difference was 3.8%. There was a significant (P< 0.01) effect of shelter on pasture growth in both years. In terms of total production over both years, the results indicate a small but consistent increase in pasture growth of about 9% for sheltered v. open plots at both sites. There was a clear seasonal effect of shelter, with greater production in autumn–winter, and a trend towards greater production in open plots during very wet periods. The results indicate that responses of pasture plants to shelter in the cool-temperate zone of Australia may be modest, and difficult to determine in field experiments, but shelter should contribute significantly to animal production because of improved plant growth in times of scarcity and reduced expenditure of energy for maintenance. Artificial shelters may provide the best means of testing the likely response to shelter of other pasture species or crops.

Effect of grain supplementation and the provision of chemical or physical fibre on marginal milk production responses of cows grazing perennial ryegrass pastures

An experiment was undertaken to establish the marginal milk production response from cereal grain supplementation by dairy cows grazing irrigated perennial pastures in spring and whether the addition of a hay supplement would improve that response. Cows were offered perennial ryegrass (Lolium perenne L.)–white clover (Trifolium repensL.) pasture at allowances (measured to ground level) of 20 or 40 kg dry matter (DM)/cow.day. Additional cows offered the low allowance were also offered supplements of pasture hay as a cube or pellet (2.5 kg DM/day), cereal grain as a pellet (5.0 kg DM/day) or cereal grain plus pasture hay (7.5 kg DM/day) as a pellet (1.75:1 DM basis) or cube (1.97:1 DM basis). The 7 treatments were replicated 3 times, and 63 cows were used (3 cows/treatment). The in vitro DM digestibility, crude protein and neutral detergent fibre (NDF) concentration of the barley and perennial pasture hay were 863 and 563 g/kg DM, 131 and 92 g/kg DM, and 182 and 666 g/kg DM, respectively. Cows from all treatments consumed herbage with an in vitro DM digestibility of 833 g/kg DM, crude protein content of 214 g/kg DM and NDF concentration of 457 g/kg DM compared with the pregrazed herbage on offer of 771, 174 and 527 g/kg DM, respectively. The mean pregrazing herbage mass of 4.13 t DM/ha consisted of perennial ryegrass (507 g/kg DM), white clover (188 g/kg DM), weeds (194 g/kg DM) and dead material (111 g/kg DM). Without supplements, cows consumed 11.2 kg DM/day at the low pasture allowance and 15.6 kg DM/day at the high allowance. Herbage intake did not decline to a large degree when barley was included in the diet, where a substitution rate of 0.2 kg reduction in pasture DM/kg DM cereal grain supplement was measured. The NDF concentration of the diet consumed was lowest (P< 0.05) for the grain pellet treatment (370 g NDF/kg DM) and highest (P<0.05) for the fibre pellet (493 g NDF/kg DM) and the fibre cube (507 g NDF/kg DM) treatments. Fat-corrected milk yield increased (P<0.05)) from 20.1 to 24.5 kg/cow.day when cows consumed 4.5 kg DM cereal grain/day with a marginal milk response of 1.0 kg 4% fat-corrected milk/kg DM concentrate supplement. Supplementation with grain or hay had no significant effect (P>0.05) on milk fat, protein or lactose concentrations. The cows offered the high allowance spent more (P<0.05) time grazing than those offered the low allowance, but there were no significant differences in rumination time. Cows spent more time ruminating when consuming the grain + fibre cube compared with the other supplement treatments, which were lower (P<0.05) and similar. Cows offered pasture at the low allowance ruminated the least. The rumen pH was not different between treatments and averaged 5.9. The ratio of acetate plus butyrate: propionate was not different between treatments and averaged 4.3. This study has shown that feeding cereal grain to cows grazing pastures high in perennial ryegrass resulted in acceptable marginal milk responses of 1 kg milk/kg DM of cereal grain in spring because of sufficient NDF in the diet. As there was adequate NDF in the diet, further supplements with pasture hay as cubes or pellets had no effect on marginal milk responses .

Tactical versus continuous stocking in perennial ryegrass-subterranean clover pastures grazed by sheep in south-western Victoria. 2. Ryegrass persistence and botanical composition

A 4-year field experiment was carried out in south-western Victoria to determine whether tactical stocking might improve perennial ryegrass (Lolium perenne L.) persistence and prime lamb production, compared with the more common practice of continuous stocking. Tactical stocking consisted of variable-length summer, autumn and winter rotations and continuous stocking in spring. The 2 grazing strategies were compared on 2 contrasting pastures: an upgraded pasture, sown with newer cultivars of perennial ryegrass and subterranean clover (Trifolium subterraneum L.) with 26 kg phosphorus/ha.year, and a more typical naturalised perennial ryegrass pasture receiving 6 kg phosphorus/ha.year. Paddocks were grazed by Border Leicester x Merino ewes, which were mated to a terminal sire to lamb in September. The effects of the grazing systems and pasture treatments on ryegrass persistence and pasture botanical composition are presented in this paper. The perennial ryegrass component of the sward decreased from an average mass of 1000 kg dry matter/ha on the upgraded pasture and 400 kg dry matter/ha on the typical pasture in spring 1996 to 100 kg dry matter/ha and <50 kg/ha for the 2 pasture types, respectively, in spring 1998. This occurred irrespective of the grazing system imposed. The decline of ryegrass was attributed to several factors including the very dry 3-year period, summer rainfall events that caused ryegrass buds to break dormancy then die when dry conditions resumed, the gravelly soil type where the experiment was located, and the high grazing pressure used. A number of species became more prevalent in the pastures as the ryegrass disappeared. Silver grass (Vulpia spp.) increased 4–5-fold on all treatments. By the fourth year, barley grass (Hordeum leporinum) and Bromus spp. had increased significantly with tactical stocking compared with continuous stocking. Capeweed (Arctotheca calendula L.) and Erodium spp. increased on both the continuously stocked and upgraded pastures. The subterranean clover component was maintained across all treatments over the 4 years, indicating that tactical stocking did not adversely affect clover persistence. Since ryegrass declined irrespective of treatment, the tactical stocking system used in this study cannot be recommended for improving ryegrass persistence.

Tactical versus continuous stocking in perennial ryegrass-subterranean clover pastures grazed by sheep in south-western Victoria. 1. Stocking rates and herbage production

A 4-year field experiment was carried out in south-western Victoria to determine whether tactical stocking might improve perennial ryegrass (Lolium perenne L.) persistence and prime lamb production, compared with the more common practice of year-around continuous stocking. Tactical stocking consisted of variable length summer, autumn and winter rotations and continuous stocking in spring. The 2 grazing strategies were compared on 2 contrasting pastures: an upgraded pasture, sown with newer cultivars of perennial ryegrass and subterranean clover (Trifolium subterraneum L.) with 26 kg phosphorus/ha.year, and a more typical naturalised perennial ryegrass pasture receiving 6 kg phosphorus/ha.year. Paddocks were grazed by Border Leicester x Merino ewes, which were mated to a terminal sire to lamb in September. The effects of the grazing systems and pasture treatments on herbage production and stocking rate are presented in this paper. Herbage production was similar between the treatments, but tactical stocking significantly increased herbage mass during the growing season (P<0.05) compared with continuous stocking. In spring each year, the herbage mass generally exceeded 3000 kg dry matter/ha in tactically stocked paddocks and averaged 500–900 kg dry matter/ha higher than the mass on continuously stocked paddocks. This enabled the year-round stocking rate to be increased by an average of 9% over the 4 years of the experiment. We considered that the stocking rates could not be further increased, despite the higher herbage mass in spring, as stock reduced the dry herbage to a low residual mass by the opening rains in autumn. In contrast, stocking rates averaged 51% higher on the upgraded pasture compared with the typical pasture over the 4 years of the experiment. This indicates that pasture improvement and soil fertility status have a much greater impact on productivity than changes to grazing method. However, tactical stocking was able to increase the sustainability of prime lamb production on upgraded pastures in a dry summer climate, by maintaining herbage cover on the paddocks over the summer–autumn period.

Sodium fertilizer application to pasture. 10. A comparison of the responses of dairy cows with high and low milk yield potential

Current recommendations for the intake of sodium of lactating dairy cows are related to milk yield. A study was conducted to compare the responses of cows of high and low milk production potential to the application of sodium fertilizer to grazed perennial ryegrass pasture. The application of sodium fertilizer increased the intake of herbage dry matter (DM), the time that cows spent grazing and the biting rate. It also increased the concentration of sodium, magnesium and calcium in herbage and decreased the concentration of potassium. Applying sodium fertilizer increased milk yield and milk fat concentration and decreased somatic cell count in the milk of cows of low‐production potential only, whereas it increased persistency of milk production in the cows of high‐production potential. The concentration of lactose in milk increased in both groups after the application of sodium fertilizer. It is concluded that the optimum dietary sodium concentration for grazing cows does not increase with milk yield, and that most immediate advantage will be gained from increasing the sodium concentration in herbage for low‐yielding cows.

The effect of concentrate supplements differing in ruminal protein degradability on milk production and blood metabolite concentrations of dairy cows grazing perennial ryegrass pasture

An experiment was carried out to compare the milk production of Friesian cows grazing perennial ryegrass pastures when fed an energy supplement or supplements with high levels of undegradable protein. Eighty-seven cows were blocked on the basis of calving date and milk yield and allocated to one of three treatments. The treatments consisted of 1.25 kg/day of concentrates based predominantly on beet pulp, fishmeal or formaldehyde-treated soyabean meal (Sopralin). The cows were grazed as a single group for the duration of the 16-week experiment. Ruminal degradability was measured in three separate cows and the results showed that the fishmeal and Sopralin concentrates had similar contents of undegradable protein, and both had substantially more than the beet pulp concentrate. Milk yields were 17.3, 18.0 and 18.6 (S.E.D.=0.46) kg/day, fat yields were 0.67, 0.67 and 0.70 (S.E.D.=0.021) kg/day, and protein yields were 0.58, 0.61 and 0.62 (S.E.D.=0.015) kg/day for the beet pulp, fishmeal and Sopralin treatments, respectively. The differences in milk and protein yields between the Sopralin and beet pulp treatments were significant ( P<0.05). Milk protein concentrations were 33.9, 34.3 and 33.7 (S.E.D.=0.26) g/kg for the beet pulp, fishmeal and Sopralin treatments, respectively. The difference between the Sopralin and fishmeal treatment was significant ( P<0.05). These results show that supplements of undegradable protein at pasture can result in higher milk production than when an energy supplement is fed.

The effect of pasture species on pasture and animal performances in irrigated systems

The effect of two contrasting forage supply options on forage and sheep production was evaluated on irrigated farmlet systems at Winchmore, mid Canterbury, over 3 years. One system was based on perennial ryegrass pastures (Control), and the other on hybrid ryegrass, tall fescue, and chicory pastures (Improved). Pasture growth rates were similar for all pasture types, however, pasture cover was on occasion, higher on the Control than Improved systems ensuring this system was self-sufficient in feed while the Improved system had a deficit averaging 714 kgDM/ha/yr. Swards on both systems contained similar proportions of legume but the Improved system contained less grass and more chicory before lamb grazing. Despite the apparent improvement in feed quality of the Improved system, its lamb performance was greater than that from the Control system for the first year only, when swards were newly established and contained greater proportions of chicory and legume. Although pasture production was similar between years there was considerable variation in lamb growth rates. This was most pronounced in the Improved system where pre-weaning rates averaged 266 and 216 g/d in years 1 and 3 respectively, and post-weaning rates 190 and 108 in years 1 and 2 respectively. The post-weaning variation appeared to coincide with fluctuations in clover and to an even greater extent, the chicory content of swards, the proportion of which declined as seasons progressed and pastures aged. The Improved system gave financial returns from lamb that were $49/ha higher than the Control in year 1 but offered no advantage in subsequent years. Compared to the Control, the Improved system had the added costs of more frequent pasture renewal and was further disadvantaged by a feed deficit necessitating buying-in supplies. Improvements anticipated to accrue from the inclusion of higher quality swards in an irrigated animal production system, were not supported by findings from this study. Keywords: irrigation, lamb production, pasture production, pasture quality, pasture species

The effects of grazing management on perennial ryegrass (Lolium perenne L.) herbage mass and persistence in south-eastern Australia

The effect of various grazing management treatments on newly sown and degraded perennial ryegrass pastures was studied at 6 different locations in the temperate high rainfall zone of southern Australia, as part of the Temperate Pasture Sustainability Key Program. The sites were located at Hamilton (2 sites, 1 grazed by cattle, 1 grazed by sheep) and Cavendish, western Victoria, Victor Harbor (Delamere), South Australia, and Ross and Parattah in Tasmania. Grazing management treatments significantly influenced the ryegrass mass and persistence of the pasture, but effects were not always consistent across sites. Autumn closure increased the perennial ryegrass content at Cavendish and Ross, as did the winter and summer closures at Ross. Spring closure increased the perennialryegrass content at Hamilton, Cavendish and Ross, but decreased it at Parattah, as did the summer closures at Parattah and Delamere. Fodder conservation decreased the ryegrass only at Parattah. At the Hamilton sheep site, and at Ross, mob stocking increased the ryegrass content, as did increased superphosphate treatments at Hamilton. Rotational grazing at Cavendish and Delamere increased the ryegrass content, as did the late spring or a late summer closure with a short autumn deferment at Cavendish and Ross, but both these treatments decreased ryegrass at Parattah. The treatments that had a negative effect at Parattah may have had a positive effect on cocksfoot at that site, creating competition for, and decreasing the ryegrass content. At most sites, treatments that included some spelling during spring to foster seed shedding, and spelling again in the following autumn to encourage germination seem to have been of benefit to the perennial ryegrass.

Sodium fertilizer application to pasture. 8. Turnover and defoliation of leaf tissue

The effects of application of sodium fertilizer on the turnover and defoliation of leaf tissue were investigated in a perennial ryegrass (Lolium perenne) pasture grazed by dairy cows. Eight plots were allocated to treatments either with or without sodium fertilizer, with the former receiving 32 kg Na ha–1 applied in five applications of NaNO3 over the grazing season. An equivalent amount of nitrogen was given to the controls as ammonium nitrate, the application of which was reduced in the sodium treatment to equate nitrogen fertilizer applications for the two treatments. In nine periods between April and September, marked tillers were recorded to measure leaf turnover, leaf lamina growth and specific leaf weight and, when combined with tiller density measurements, gave an estimate of herbage flux for the sward. The defoliation and net growth of the marked tillers were monitored at 3‐day intervals and the data were combined with tiller density and specific leaf weight data to determine the intake of the expanding, penultimate and oldest live leaf laminae. Sodium fertilizer application did not affect the rate at which leaves appeared, but it retarded their rate of disappearance. The extension rate and the specific weight of green laminae were both increased by sodium fertilizer application and therefore the net gravimetric growth rate was increased. Tiller density was not affected by sodium fertilizer application and hence the estimated herbage growth and net herbage flux were increased by sodium fertilizer application. Application of sodium fertilizer did not affect lamina length, and in both treatments the penultimate laminae were approximately twice as long as expanding and oldest live laminae. Defoliation frequency decreased from the expanding to the oldest live laminae in the control treatment without sodium. Sodium fertilizer application increased the frequency of defoliation of the oldest live leaf and also increased the length of the expanding leaf that was defoliated. For penultimate leaf laminae sodium fertilizer application reduced the defoliation frequency and length of foliage grazed. The dry‐matter (DM) intake of the oldest live laminae was increased by the application of sodium fertilizer. It is concluded that sodium fertilizer application increases net herbage growth both by increased extension rate of leaf laminae and specific leaf weight and by delayed laminae senescence, and that it increases herbage DM intake by increasing the defoliation frequency of the oldest live leaf laminae.

Growth, persistence, and alkaloid levels of endophyte‐infected and endophyte‐free ryegrass pastures grazed by dairy cows in northern New Zealand

A farm‐scale trial was conducted over three years at the Dairying Research Corporation, Hamilton, New Zealand to compare the growth and persistence of endophyte‐infected and endophyte‐free perennial ryegrass (Lolium perenne) pastures established with or without white clover (Trifolium repens), when rotationally grazed by dairy cows. Endophyte‐free ryegrass areas were also undersown with endophyte‐free seed in March and April of the second and third years, respectively. Average total herbage yields were similar for all treatments in each of the three years, ranging from 12.8 to 13.9 t DM ha−1. Pasture growth rates in all treatments were lowest in the first summer/autumn after drilling, averaging 17 kg DM ha−1 day−1 for 90 days, coinciding with the highest herbage concentrations of lolitrem B (2.37 to 3.04 μg g−1 DM) in the high‐endophyte ryegrass. Ergovaline herbage concentrations rarely exceeded 1 μg g−1 DM and were highest (1.6 μg g−1 DM) in high‐endophyte ryegrass pastures at the start of the third summer (December 1995), probably because of a high seed‐head content (30% of DM). Contamination of endophyte‐free ryegrass areas with volunteer endophyte‐infected ryegrass was rapid, averaging 26, 41, and 50% of plants after the first, second, and third years from sowing, respectively. Further research is required to identify sources of this contamination and management strategies to maintain purity of endophyte‐free ryegrass or ryegrass containing novel endophytes.

The effect of pasture species on lamb performance in dryland systems

The effects of two contrasting forage supply options on forage and sheep production were evaluated on unirrigated farmlet systems at Winchmore, Mid-Canterbury. One option was based on perennial ryegrass pastures (Control), and the other (Improved) on hybrid ryegrass, tall fescue, and chicory pastures. All pasture types grew at similar low rates during winter but chicory grew more rapidly than the grasses during the summer droughts. The Control conserved more but required less conserved feed than the Improved system. Both had a feed deficit which averaged 23 and 42 kg DM/ewe respectively over the 2 years. The lambs on the Improved pastures grew more rapidly than the Controls throughout, exceeding the rate of the Controls by 142 and 165 g/head/day post-weaning in years 1 and 2 respectively. This resulted in considerably more lambs reaching target drafting weights on the Improved system, 92 vs. 53 and 97 vs. 58%, in years 1 and 2 respectively. This increased the income from lambs by $104 and $94/ ha in these years. Ewe liveweights were similar during pregnancy but differed during lactation and post-weaning at the end of which, ewes on Improved pastures were 6 and 4 kg heavier than the Controls in years 1 and 2 respectively. They consequently produced fleeces that were 10 and 12% heavier. The superior animal performance associated with the Improved system reflects higher pasture quality due to less endophyte and dead matter, and an increase in the proportion of the more nutritious components, legumes and chicory. Keywords: dryland, lamb production, pasture production, pasture quality, pasture species

Ewe reproductive performance and growth rate of suckling-lambs on endophyte-infected perennial ryegrass pasture

Two groups (n=39) of Romney breeding ewes were maintained under the same grazing management on either endophyte-infected (E+) or endophytefree (E-) perennial ryegrass pasture for two years (1997-1998) following a one-year equilibration period. The ewes were naturally mated in March each year and ovulation rate at 1st mating was measured, and conception and the number of lambs born and weaned were recorded. All ewes were weighed monthly and lamb growth rates were determined between birth and weaning. Mean mating date was delayed by 1.8 days (P

Performance of temperate perennial pastures in the Australian subtropics 2. Milk production

Summary. Milk production from irrigated, pure stands of perennial ryegrass (Lolium perenne cv. Yatsyn), prairie grass (Bromus willdenodii cv. Matua) and tall fescue (Festuca arundinacea cv. AU Triumph) were compared with that achieved from Italian ryegrass (L. multiflorum cv. Concord) over 3 lactations of multiparous Holstein–Friesian cows at Mutdapilly in south-east Queensland. Pastures were fertilised with 50 kg nitrogen/ha . month as urea and annual dressings of 20 kg phosphorus/ha and 50 kg potassium/ha (as superphosphate and muriate of potash respectively). There were 4 pasture treatments grazed at 3 cows/ha in a 1-week-on, 3-weeks-off rotation with 2 replicates and 3 cows/treatment block. Cows grazed the pastures day and night from May to November. Over summer, cows grazed the pastures during the night and were fed supplements (silage in the first lactation, and lucerne hay in the second and third lactations) during the day because there was no shade available in the irrigation areas. In autumn, the animals were removed from the ryegrass and prairie grass pastures for 8 weeks to allow seedling re-establishment, either by oversowing (ryegrasses) or natural reseeding (prairie grass). Cows continued to graze the fescue pastures at night during autumn. All cows received a ration of 4 kg/cow of a grain–minerals mixture in the first lactation and 5 kg/cow in the second and third lactations. Milk production from perennial ryegrass was higher than from fescue in the first lactation and Italian ryegrass in the second and third lactations. Prairie grass gave similar milk production to perennial ryegrass in all 3 years. In the third year, perennial ryegrass, prairie grass and fescue gave similar milk production. Milk quality from the 4 grasses was similar except in the third lactation when the lactose content of milk from perennial ryegrass pastures was lowest. There were also small and inconsistent differences in milk component yields between the 4 grasses. Liveweight changes were small except in the second lactation when the cows grazing fescue lost weight relative to the other treatments. Mean liveweight at calving increased over the 3 lactations. It was concluded that all 3 temperate perennial grasses demonstrated useful traits for use in subtropical dairy pastures. Perennial ryegrass produced the most milk from the lowest amount of dry matter on offer. Prairie grass produced similar milk yields to perennial ryegrass, was well eaten by cattle and was self regenerating. Although fescue was slower to establish and needed more intensive management to control maturity, it was the most persistent and was the only grass to provide autumn grazing. In the second year this attribute resulted in a lower requirement for supplementary feeding. Fescue produced the highest gross margin in the second lactation and was only marginally less than prairie grass in the third. The performance of Italian ryegrass was as good as that of perennial ryegrass in the first lactation but fell substantially in the second and third lactations as the level of summer grass invasion increased.

Dry matter intake, nutrient selection and milk production of dairy cows grazing rainfed perennial pastures at different herbage allowances in spring

Summary. The effect of herbage allowance (20, 30, 40, 50, 60 and 70 kg DM/cow. day) on the consumption of nutrients from herbage and milk production by cows in early lactation, was examined. The experiment was conducted on rainfed perennial ryegrass pastures in September and October 1997 in south-eastern Victoria, Australia. The herbage on offer comprised 64% perennial ryegrass, 21% other grasses, 1% white clover, 5% weeds and 9% dead material on a dry matter (DM) basis. The average pregrazing herbage height was 13 cm, at an estimated pregrazing herbage mass of 3.6 t DM/ha. The herbage on offer was of high quality containing 11.6 MJ metabolisable energy/kg DM, 202 g crude protein/kg DM and 525 g neutral detergent fibre/kg DM. Concentrations of calcium, magnesium, sodium, potassium, phosphorus, sulfur and chloride were 4.4, 2.2, 4.4, 31.2, 3.5, 2.7 and 11.4 g/kg DM, respectively. As daily herbage allowance per cow increased, dry matter intake increased curvilinearly (P&lt;0.01) from 11.2 to 18.7 kg DM/cow. day. This was associated with a decrease in utilisation of herbage from 54 to 26% and an increase in milk production from 25.9 to 29.1 kg/cow. day. The cows on all treatments grazed for less than 8.7 h/day. The increase in intake was achieved by an increase in the rate of herbage intake from 1.5 to 2.2 kg DM/h for herbage allowances of 20 and 70 kg/cow.day, respectively. Irrespective of herbage allowance, cows selected a diet that was approximately 10% higher in in vitro dry matter digestibility and 30% higher in crude protein than that in the herbage on offer. The neutral detergent fibre content of the herbage selected was lower (P&lt;0.05) than that on offer. The herbage consumed contained more (P&lt;0.05) magnesium, potassium and sulfur, the same amount of calcium and phosphorus and less (P&lt;0.05) sodium and chloride than the herbage on offer. For rainfed perennial pastures in spring, herbage allowance is an important factor in determining voluntary feed intake and production of dairy cows. To achieve 30 L from herbage, without supplementation, high herbage allowances are required. The increase in herbage intake, with increasing herbage allowance, resulted from an increase in rate of dry matter intake and not an increase in grazing time. No relationship was evident between herbage allowance and the selection differentials for in vitro dry matter digestibility, crude protein and neutral detergent fibre. Selection differentials for rainfed perennial pastures in spring are similar to those reported for irrigated perennial pastures in northern Victoria in spring and autumn. When determining nutrient requirements it is important to consider the interaction between herbage intake and nutrient concentration in the herbage.

The effect of introducing timothy, cocksfoot and red fescue into a perennial ryegrass sward and the application of sodium fertilizer on the behaviour of male and female cattle

The effects on cattle grazing behaviour of introducing the three novel species into a perennial ryegrass pasture were examined in a Latin Square design. Castrated male and entire female cattle of similar age were grazed on plots of perennial ryegrass only (treatment 1), perennial ryegrass and timothy (treatment 2), perennial ryegrass, timothy and cocksfoot (treatment 3) and perennial ryegrass, timothy, cocksfoot and red fescue (treatment 4). Perennial ryegrass had the greatest nutritional value, with a high crude protein and low MADF content, whereas cocksfoot and red fescue had high MADF contents. The introduction of timothy had no effects on grazing behaviour. When cocksfoot was additionally included, the cattle grazed for longest on the cocksfoot plots and total grazing time and the time spent ruminating both increased. When red fescue was additionally included with the other three species it was mostly avoided. When they did graze the red fescue, the cattle had slow biting and walking rates and reduced lateral head movement, suggesting greater selectivity. Mean treatment herbage height was increased in treatments three and four because cocksfoot and red fescue were taller than the other two species. Sodium fertilizer increased the sodium concentration of all species but particularly perennial ryegrass and cocksfoot. The grazing time was only increased by sodium for these two species, and the rates of biting and walking during grazing were also increased, suggesting that sodium reduced selectivity. Male cattle had faster biting and walking rates than female cattle and extended lateral head movement during grazing. It is concluded that perennial ryegrass, timothy and cocksfoot were more acceptable to cattle than red fescue. There was an increase in acceptability of the natrophilic species, perennial ryegrass and cocksfoot, when sodium fertilizer was applied, suggesting that sodium content partly determines herbage acceptability.

A 6-year comparison of nitrate leaching from grass/clover and N-fertilized grass pastures grazed by sheep

Nitrate leaching was measured over a 3-year period from rotationally grazed perennial ryegrass (Lolium perenne L.) pasture receiving 200 kg fertilizer-N/ha and from similarly grazed ryegrass/white clover (Trifolium repens L.) pasture that received no N fertilizer. The results are discussed together with those from the same plots in the preceding 3 years when they were stocked continuously. Under both managements, the numbers of grazing sheep were adjusted on the basis of the quantity of herbage available on the plots. During the whole 6 years, mean nitrate concentrations in soil water collected by porous cup samplers remained below the European Union limit of 11·3 mg N/l except for the fertilized grass plots in year 5 of the study. Quantities of nitrate leached ranged from 6 to 34 kg/ha per year from the grass/clover plots and 2·46 kg/ha from the fertilized plots. Leaching losses from both types of pasture were positively correlated with the numbers of lamb grazing days in the later part of the grazing season. This relationship and the high spatial variability associated with the measurements indicated that N derived from excreta was the main source of leached nitrate. It was concluded that, where pastures of equal productivity are compared, similar quantities of N are likely to be leached from grass/clover swards as from grass swards receiving N fertilizer.

Effects on maternal and foetal traits of feeding supplement to grazing pregnant ewes

AbstractThirty single-bearing Merino ewes were used to examine the effect of feeding supplement, from 91 to 140 days of gestation, on changes in chemical composition of the ewes, on the relationships with live weight and body condition score and on the foetus. Ewes grazed a perennial ryegrass pasture and were offered either no supplement or 500 g per head per day of a concentrate supplement from days 30 to 90 and (or) from days 91 to 140 of pregnancy. Maternal carcass and non-carcass components, uterine wall, foetus and placenta plus cotyledons were chemically analysed. Live weight (LW) and body condition score (BCS) on day 140 were both affected by supplementation during late pregnancy, mobilization of protein and fat being lower in animals receiving supplement. BCS accounted for more variation than LW in the carcass fat depot. Because this depot was the most important source of energy from days 91 to 140 of gestation, this suggests that BCS is a useful estimator of mobilization of maternal fat reserves during this stage of pregnancy. The ability to mobilize reserves and protect foetal growth by Merino ewes in southern Europe, where large fluctuations in grass growth rate exposes them to considerable undernutrition as pregnancy proceeds, was confirmed in this experiment. However, when the nutritional regime is extreme, supplementary feeding to the ewes is recommended, in order to make the whole system economically profitable.

Matching grass supply to grazing patterns for dairy cows under strip-grazing management

Grazed herbage is the cheapest feed available for dairy cows but total intake of nutrients from grazed pasture alone is generally insufficient to allow high yielding dairy cows to reach their production potential. Cows have their main daily meal following afternoon milking in the period up to sunset (e.g. Rook et al., 1994 ). In addition, both the DM content and water soluble carbohydrate (WSC) concentration of grass increase over the day (e.g. Orr et al., 1997) due to the loss of moisture and the accumulation of the products of photosynthesis. Based on this evidence, this study tested the hypothesis that dairy cows receiving strip-grazing allocations following the afternoon rather than the morning milking would show higher intake rates and consequently higher milk yields.Twenty Holstein-Friesian cows (median calving date 10 February 1997) were each supplemented with 4 kg concentrates day-1 and strip-grazed a perennial ryegrass pasture in four groups of 5 cows.