Evaluation of the phenotypic variation in kikuyu populations

A series of cutting experiments evaluated the phenotypic variation in populations of kikuyu in Australia to assess their capacity to provide sufficient variability to sustain a breeding and selection program. The aim of such a program would be to develop a high quality cultivar without compromising stand vigour. Single plants, generated either from seed of commercial cultivars or accessions, seed treated by mutagenic chemicals or from randomly-chosen runners from stands across Australia, were sown singularly in randomised block experiments under irrigation at two sites in subtropical eastern Australia. There were significant differences between kikuyu cultivars in leaf, stem and runner dry matter yields, plant height and quality (crude protein, neutral detergent and acid detergent fibre content and in vitro digestibility). Variation between individual plants was also substantial, with 7, 3 and 3 % improvement over the population mean for crude protein content, in vitro digestibility, and metabolisable energy respectively, and a reduction of 5 and 8 % in neutral and acid detergent fibre content. It was also associated with a forage yield twice the population mean from these elite plants. Mutagenesis of seed from a commercial cultivar produced greater within-population variation for quality, but less for agronomic, traits compared with the natural population. Gene fingerprinting suggested that the material distributed across Australia came from two main sources, one related to cv. Whittet and the other to a ‘common’ lower yielding type. It was concluded that the currentlyavailable material within Australia, although from limited genetic base, contained sufficient variation to achieve a significant improvement in quality without reducing plant vigour

Evaluation of the phenotypic variation in kikuyu populations

A series of cutting experiments evaluated the phenotypic variation in populations of kikuyu in Australia to assess their capacity to provide sufficient variability to sustain a breeding and selection program. The aim of such a program would be to develop a high quality cultivar without compromising stand vigour. Single plants, generated either from seed of commercial cultivars or accessions, seed treated by mutagenic chemicals or from randomly-chosen runners from stands across Australia, were sown singularly in randomised block experiments under irrigation at two sites in subtropical eastern Australia. There were significant differences between kikuyu cultivars in leaf, stem and runner dry matter yields, plant height and quality (crude protein, neutral detergent and acid detergent fibre content and in vitro digestibility). Variation between individual plants was also substantial, with 7, 3 and 3 % improvement over the population mean for crude protein content, in vitro digestibility, and metabolisable energy respectively, and a reduction of 5 and 8 % in neutral and acid detergent fibre content. It was also associated with a forage yield twice the population mean from these elite plants. Mutagenesis of seed from a commercial cultivar produced greater within-population variation for quality, but less for agronomic, traits compared with the natural population. Gene fingerprinting suggested that the material distributed across Australia came from two main sources, one related to cv. Whittet and the other to a ‘common’ lower yielding type. It was concluded that the currentlyavailable material within Australia, although from limited genetic base, contained sufficient variation to achieve a significant improvement in quality without reducing plant vigour

Plant breeding influences the performance of temperate pasture species in the subtropics

Data from a series of experiments over a 15-year period in the subtropics were interrogated to determine whether plant breeding had influenced the performance of ryegrass and lucerne in the subtropics of Australia. It was found that, within sets of plant breeders' lines available for sowing in any one experiment, yield of the best experimental lines of perennial and annual ryegrasses and lucerne were almost always above that of standard cultivars. The range in rust resistance was not as great in annual ryegrass, with breeders' lines rarely being superior to the standard cultivars. However in perennial ryegrass and lucerne, the range of disease: resistance was greater and did show improvement relative to the standard cultivars. There was also a trend towards improved performance of breeders' lines over time. Those available between 1996 and 1999 showed an overall increase in yield over the general experimental mean, and the performance of the best and worst experimental lines in ryegrass and lucerne at the commencement of the study period (1978 for lucerne and 1992 for ryegrasses). Persistence of lucerne showed the reverse trend with an overall fall in the general experimental mean. Resistance to Phythophthora root rot (PRR) and leaf diseases improved over time but that for Colletotrichum crown rot (CCR) declined. The reasons for these trends are discussed

Forage production from irrigated oats or ryegrass grown with annual legumes or nitrogen in south-eastern Queensland

The production of irrigated Saia oats (Avena strigosa) and Wimmera ryegrass (Lolium rigidum) grown with annual temperate legumes or nitrogen fertilizer was studied over two years on a black earth at Gatton, south-eastern Queensland. Jemalong medic (Medicago truncatula) grown with oats or ryegrass, was more productive than alternative legume/grass forage combinations. Total dry matter and nitrogen yields of both Jemalong and snail (M. scutellata) medic mixtures were similar to those of oats or ryegrass fertilized with 205 kg ha-lN in 1974. In 1975, Jemalong mixtures gave higher dry, matter and equivalent nitrogen yields to the respective forages fertilized with 336 kg ha-1 N. Snail medic gave the best early production, reaching maximum growth in late winter, about a month earlier than Jemalong. The other legumes did not contribute to production until spring. In 1974, total production of oats and ryegrass was similar, but in 1975 ryegrass production was the greater

Nitrogen-fertilised grass in a subtropical dairy system 3. Effect of stocking rate on the response to nitrogen fertiliser

Two stocking rates, one as practised on farms (2 cows/ha) and the other 50% higher, were assessed for effect on pasture and milk yield response to applied nitrogen (N) fertiliser (0-600 kg N/ha. year) for Holstein-~Friesian cows grazing Rhodes grass (Chloris gayana) cv. Callide pastures. Pastures were grazed in combination with grazing oats for winter, with overall farm stocking rates of 1.17 and 1.37 cows/ha for ' the 2 treatments. Cows were maintained on these areas for 3 years. Cracked grain was given at 0.8 t/cow. year, and hay or silage supplements were given when green grass yield was <0.5 t dry matter (DM)/ha. The incremental response (P<0.05) in milk yield to each kg increase in level of applied N was 4.93 kg/ha at 1.17 cows/ha and 1.64 kg/ha at 1.37 cows/ha. The amount of conserved forage fed at the high stocking rate increased (530 and 970 kg/ha. year at 1.17 and 1.37 cows/ha), and financial margins over costs were reduced at the high stocking rate. The low milk response at the high stocking rate was associated with a low response in pasture growth. At <2 t pasture DM/ha on offer, incremental response to applied N declined, and there may have been an excessive loss of N through volatilisation in heavily grazed pastures. Milk yield per cow was closely related to total pasture yield on offer (P<0.01), and to leaf and stem yields (P<0.05). Relationships were stronger in summer and autumn than in spring. Over the full year, milk yield increased by 1.24 kg/kg leaf DM or 0.24 kg/kg total pasture DM on offer. At the higher stocking rate, surface soil (0-10 cm) concentrations of phosphorus and nitrate were higher than at the lower stocking rate. We conclude that in areas of moderate rainfall (<1000 mm/year) in the subtropics, high stocking rates resulting in low pasture yields and exposed ground surface will be associated with low efficiency of use of applied N

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

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

Seasonal variation in the herbage yield and nutritive value of perennial ryegrass (Lolium perenne L.) cultivars with high or normal herbage water-soluble carbohydrate concentrations grown in three contrasting Australian dairy environments

Two lines of perennial ryegrass (Lolium perenne L.), cv. Aurora and breeding line Ba 11351, from the United Kingdom with elevated concentrations of water-soluble carbohydrates in the shoot were compared with the standard cultivars, Ellett, Vedette and Kangaroo Valley, in pure grass swards under irrigation at Kyabram, Victoria, and Gatton, Queensland, and under natural rainfall at Condah, Victoria, during 1995–97. Near infrared reflectance spectroscopy was used to predict the water-soluble carbohydrate, crude protein, in vitro dry matter digestibility, neutral and acid detergent fibre, and Klason lignin concentrations of the perennial ryegrass herbage. Herbage yield and water-soluble carbohydrate differed between cultivars at each site at most harvests, with the high water-soluble carbohydrate lines usually yielding less and having higher water-soluble carbohydrate concentrations than the 3 standard cultivars. However, the high water-soluble carbohydrate lines also had higher water-soluble carbohydrate concentrations at harvests where their yield was equal to the standard cultivars. The other nutritive value traits differed significantly at more than half of the 32 harvests: the high water-soluble carbohydrate lines had higher crude protein and dry matter digestibility, and lower neutral detergent fibre, the neutral detergent fibre containing less acid detergent fibre and lignin than did the standard cultivars. The high water-soluble carbohydrate lines were more susceptible to crown rust during spring and summer than the standard cultivars at Kyabram and Gatton: heavy infections reduced yield, water-soluble carbohydrate, dry matter digestibility and crude protein. Higher water-soluble carbohydrate may depend on only a few genes, as does rust resistance and it seems likely that high yielding, high water-soluble carbohydrate cultivars can be developed by recombination and selection

Nitrogen-fertilised grass in a subtropical dairy system 2. Effect of level of nitrogen fertiliser on animal production

The response in yield of milk and milk components to level of nitrogen (N) fertiliser applied to a tropical grass pasture was measured over 6 years. Pasture (Chloris gayana cv. Callide) was stocked at 2 Holstein-Friesian cows/ha and received annual basal dressings of phosphorus (250 kg superphosphate/ha) and potassium (63 kg KCl/ha), and treatments of urea at 0, 150, 300, 450, and 600 kg N/ha. year. Fertiliser was applied in 3 equal applications in September, December, and February. Cows were maintained on the pasture throughout the year, and 0.4 ha grazing oats/cow (100 kg N/ha. year) and 0.8 t cracked grain/cow were given as supplements. Hay or silage supplements were given when green grass yield was <0.5 t dry matter (DM)/ha. The amount of hay and silage given annually averaged 755, 437, and 529 kg DM/cow at 0, 300, and 600 kg N/ha. Mean milk response over the 6 years was high (8 kg milk/kg N) for 0-150 kg applied N/ha. year. The difference between fertilised and unfertilised pastures increased with time, and this was associated with degradation of pasture, excessive liveweight loss during lactation, and premature drying off of cows at nil applied N. At 150-600 kg N/ha. year, response was consistent across years (4.5 kg milk/kg N. year). Yields of milkfat and lactose reflected changes in milk yield, although milk protein percentage decreased significantly (P<0.05) with increased level of applied N. Conception rate increased with rate of applied N, from 58 to 92% at 0 and 600 kg N/ha. year (P<0.01). The results suggest a maximum margin over feed costs at 334 kg applied N/ha over the total grazed area. We conclude that there will be a large milk response to applying about 150 kg N/ha.year; beyond that, the milk response would be consistently about 4.5 kg/kg N to at least 600 kg N/ha.year

Nitrogen-fertilised grass in a subtropical dairy system. 1. Effect of level of nitrogen fertiliser on pasture yield and soil chemical characteristics

The effects of five levels of nitrogen (N) fertiliser on pasture yield and composition and soil chemical characteristics of Rhodes grass (Cholris gayana) cv. Pasture under grazing and cutting in a subtropical environment of 800 mm annual rainfall were studied over 6 years. Pasture received annual basal dressings of superphosphate (250 kg/ha) and potassium chloride (125 kg/ha for plots, 125 kg/ha . alternate year for grazed paddocks). Urea was applied in 3 equal dressings in September, December, and February, at rates equal to 0, 150, 300, 450, and 600 kg N/ha. year. Stocking rate was 2 Holstein-Friesian milking cows/ha throughout the year, and separate areas of grazing oats (0.4 ha/cow), cracked grain (0.8 t/cow.year), and hay or silage were used to supplement pasture. Under both cutting and grazing, pasture dry matter (DM) yield increased linearly with applied N to about 300 kg N/ha. year, with little further increase at higher levels. Under grazing there was evidence of a decrease in yield at 600 kg N/ha.year, due to total death of the pasture following frosting in winter and the need for regeneration from seedlings in spring; this regeneration was slowed by the large amount of surface litter. Grass N contents decreased and phosphorus and potassium contents decreased with increasing levels of applied N. All 3 nutrients increased from year 1 to 6. Leaf content of grazed pasture was highest during spring (>30% DM) and declined through to autumn (50%) but was not altered by level of applied N. Soil nitrate-N levels increased (P<0.05) with level of applied N, from 4 to 42 mg/L at 0 and 600 kg N/ha. year, respectively. After 6 years of fertilisation at 300 and 450 N/ha.year, nitrate-N levels were similar to those for 600 kg N/ha.year. Soil pH decreased (P<0.05) with applied N, by 0.15 and 0.28 units annually for 150 and 600 kg N/ha.year, respectively. We conclude that in this environment large responses in pasture growth occur under both cutting and grazing to levels of applied N to about 300 kg N/ha.year, with little response beyond this level

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results