Showing papers in "Australian Journal of Experimental Agriculture in 1996"

A comparison of three techniques to determine the herbage intake of dairy cows grazing kikuyu (Pennisetum clandestinum) pasture

Abstract: Two studies were conducted to compare the precision of estimating kikuyu grass (Pennisetum clandestinum) intake by Friesian cows fed 0, 3 or 6 kg of cereal-based concentrate/cow.day, using a rising plate meter (RPM), standard energy requirements in reverse (RS) and plant wax alkanes as internal markers. Study 1 compared herbage intake estimates obtained using the RPM and RS techniques over a 45-day period. RS estimates were based on the metabolisable energy (ME) of ration components derived from in vitro organic matter digestibility (OMD) values. Pregrazing calibration equations for the RPM determined at 2-weekly intervals differed significantly (P<0.01) from postgrazing calibrations; consequently separate equations were used to determine pasture intake as the difference in pre- and post-grazing pasture mass. Estimates of total intake were lower using the RPM than the RS technique for the groups fed 0 kg (12.5 v. 14.8 kg dry matter (DM)/cow.day) and 3 kg (10.4 v. 12.9 kg DM/cow.day) of concentrate, and higher for those receiving 6 kg (10.5 v. 7.8 kg DM/cow.day). In study 2 (12 days duration), intakes derived using alkanes were compared with intakes estimated using the RS and RPM techniques. The C32/C33 alkane pair gave the closest estimate of herbage intake to that obtained using the RPM and RS techniques. Whole diet in vivo DM digestibility (DMD), determined by the alkane method, was not significantly different between the 3 groups (mean 70%), suggesting that digestibility of the kikuyu declined with increasing concentrate supplementation. The in vivo DMD of kikuyu alone (determined in the non-concentrate-supplemented cows) was considerably higher (69.5%) than the OMD determined in vitro (63.9%). By using in vivo rather than in vitro digestibilities for kikuyu in the RS calculations, the intake estimates were reduced by 17%, and for the 0 kg concentrate group, intake estimates aligned closely to predictions of the RPM and alkanes. Concentrates in the diet resulted in lower intake estimates using the RS technique compared with the RPM and alkane techniques. This was most evident at the 6 kg level of supplementation where RS predicted kikuyu intake to be 6.5 kg DM/cow.day using in vivo-derived DMD and this was substantially lower than either the RPM (12.4 kg DM/cow.day) or alkanes (9.2 kg DM/cow.day). The alkane technique provided a direct and precise method of measuring the intake of individual cows grazing tightly-managed kikuyu pasture. With the use of accurate animal production and feed quality parameters, the RS technique can provide sensible pasture intake estimates over an extended time period. The RPM technique is useful for obtaining herd estimates of pasture intake and for the determination of pasture parameters associated with intake.

Effect of sowing point design and tillage practice on the incidence of Rhizoctonia root rot, take-all and cereal cyst nematode in wheat and barley

Abstract: Effect of tillage treatments on the cereal root diseases, rhizoctonia root rot, take-all and cereal cyst nematode, and on grain yield of cereals were tested in 4 field experiments over 3 years. Conventionally cultivated treatments were compared with a range of direct-drill treatments using either a standard tined seed drill equipped with 10 cm sowing points, a specialised drill designed to give minimal soil disturbance or a standard tined seed drill equipped with a range of commercial or modified narrow points designed to provide soil disturbance from 0 to 5.0 cm below seed depth. Direct-drilled treatments that disturbed the soil below seed depth (DDD) and treatments that included 1 cultivation prior to sowing (CPS) resulted in a reduction of rhizoctonia root rot when compared with direct-drilled treatments that did not disturb the soil below seed depth (DDN). When seasonal conditions encouraged volunteer plant growth before sowing, a chemical fallow treatment applied 3 weeks before sowing significantly reduced rhizoctonia root rot in all direct-drilled plots. This was a significant factor in DDD treatments providing effective control of rhizoctonia root rot. Take-all was present in 3 of the 4 experiments. In 2 experiments, take-all was significantly higher in plots following DDN treatments than DDD or CPS treatments and in 1 experiment there was no effect of tillage. Cereal cyst nematode was present in 1 of the 4 experiments. The level of root damage from cereal cyst nematode was least in plots following DDN treatments, higher following DDD treatments and highest following CPS treatments. The influence of tillage practice on grain yield was closely related to the effect of tillage on cereal root disease when levels of disease were moderate to high. Where the incidence of root disease was low, grain yield differences due to tillage treatments were generally related to agronomic factors such as seed depth and seedbed condition.

Classification of Australian garlic cultivars by DNA fingerprinting

Abstract: Summary. Garlic (Allium sativum L.) reproduces only by vegetative propagation yet displays considerable morphological variation within and between cultivars. The origins of Australian cultivars are uncertain and the descriptive names applied to them may not reflect their derivation. Twenty common Australian garlic cultivars were analysed by the random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) technique using 20 random decamer primers. The amplification products of 5 of these primers resulted in 65 clear polymorphic bands. These bands were transformed into a binary format, and genetic similarities calculated using a simple matching coefficient. The similarities were used to perform a cluster analysis and produce a dendrogram grouping the cultivars. Bolting and intermediatehonbolting types could be differentiated from each other. These could be further subdivided into 4 groups based on length of growing season.

Growth, yield and neurotoxin (ODAP) concentration of three Lathyrus species in Mediterranean-type environments of western Australia

Abstract: The growth, phenology, grain yield and neurotoxin (ODAP) content of Lathyrus sativus, L. cicera and L. ochrus were compared with a locally adapted field pea (Pisum sativum L.) to examine their potential as grain legumes in Western Australian farming systems. About 17 lines of each species were obtained from ICARDA, Syria, and grown at 3 agro-climatically different sites. In general, the 3 species were later flowering than field pea, especially L. cicera and L. ochrus; however, L. sativus was the last species to mature. The best Lathyrus lines produced biomass near flowering similar to field pea. At the most favourable site, grain yields were up to 1.6, 2.6 and 1.7 t/ha for L. sativus, L. cicera and L. ochrus respectively, compared with a field pea grain yield of 3.1 t/ha. There was considerable genotype and environmental variation in ODAP concentration in the seed. On average, the ODAP concentration of L. ochrus (6.58 mg/g) was about twice that of L. sativus, and L. cicera had the lowest ODAP concentration (1.31 mg/g). Given that Lathyrus spp. have not had the same breeding effort as field pea and other grain legumes in Australia, these results encourage further selection or breeding. In the shor-tseasoned, mediterranean-type environment of Western Australia, harvest indices and grain yields could be improved with early flowering. Low ODAP concentration should also be sought.

Survey of weeds and diseases in cereal crops in the southern wheat belt of New South Wales.

Abstract: A field survey of weeds in 86 cereal crops in southern New South Wales was conducted in spring 1993 to determine weed and disease distributions, and their levels of infestation. Fifty weed species from 19 families were identified. The most widespread species were Arctotheca calendula (capeweed) in 76% of fields, Avena spp. (wild oats) in 72%, Trifolium subterraneum (subterranean clover) in 69%, Lolium rigidum (annual ryegrass) in 69%, Vulpia spp. (silvergrass) in 63%, Juncus bufonius (toad rush) in 62%, Crassula spp. (stonecrop) in 37%, Polygonum aviculare (wireweed) in 37%, Fumaria spp. (fumitory) in 36%, Chondrilla juncea (skeleton weed) in 36%, Rumex acetosella (sorrel) in 28% and Hordeum spp. (barley grass) in 26%. Some species were associated with region and previous crop. Levels of weed infestation, based on a visual assessment of the relative weed-crop ground cover, plant density and height, were surprisingly high. A questionnaire completed by 181 farmers and 30 agronomists, to determine their perceptions of the most abundant weeds, showed close agreement with the field survey. Current weeds were generally considered difficult to control and expected to be a continuing problem. The exception was Raphanus raphanistrum (wild radish) which had a low incidence, but was expected to become more serious. The root disease, take-all (Gaeumannomyces graminis var. tritici), was recorded in 32% of the 56 wheat crops examined. It was associated with a previous pasture, lupin or cereal crop, but was absent when the previous crop was canola. Another root disease, rhizoctonia bare patch, was found in only one wheat crop. Common foliar diseases were ring spot (Pyrenophora semeniperda) in 57% of wheat crops, septoria tritici blotch (Mycosphaerella graminicola) in 23%, yellow spot (Pyrenophora tritici-repentis) in 2 1 %, stripe rust (Puccinia striiformis) in 3%, and septoria nodorum blotch (Phaeosphaeria nodorum) in 2%. These diseases were generally present on less than 5% of crop leaf area.

Seedling and adult plant evaluation of race variability in Leptosphaeria maculans on Brassica species in Australia.

Abstract: Seedling and adult plant studies were used to identify the race structure of Leptosphaeria maculans (the cause of blackleg) on oilseed Brassica species in Australia. Host-pathogen interactions using a set of 12 differential host lines identified 14 seedling relationship, however, between seedling and adult plant reactions to individual isolates, indicating that seedling and adult plant resistance are under different genetic control. While non-specific adult plant resistance was observed in the B. napus line Jet Neuf, host-pathogen interactions confirmed the existence of race-specific adult plant resistances in other differential lines.

Nutrition during fetal life alters annual wool production and quality in young Merino sheep

Abstract: The effect of maintenance v, submaintenance diets of pregnant ewes in 1991 and 1992 on establishment of the wool follicle population in their progeny, and its effect on the progeny's wool production (quantity, quality and variation across the body of the animal) to 1.4 years of age was examined. The experimental protocol used cloned animals created by bisecting embryos at day 6 of pregnancy. Each clone was placed in a ewe, which was subsequently fed from about day 50 to 140 of pregnancy at maintenance or submaintenance. Ewes on maintenance nutrition maintained liveweight throughout pregnancy, while submaintenance ewes were 12.1 kg lighter (P<0.001) 10 days before lambing. In 1991, a total of 74 lambs were born, including 17 sets of surviving clones. In 1992, 102 lambs were born, including 18 sets of surviving clones. Only data for the 35 sets of genetically identical 'twin' progeny and their dams are reported. Birth weights of lambs born to ewes fed at the submaintenance rate were 0.5 kg lighter (P<0.01) than their 'twins' born to ewes fed at maintenance. Midside secondary:primary (Sf: Pf) ratios for mature wool follicles were less (P<0.01) at birth, lamb and hogget shearing (1.4, 1.5 and 2.1 units respectively) for the progeny born to ewes fed at submaintenance. Progeny from ewes on the submaintenance treatment produced less clean wool, 0.1 kg to 0.4 years of age (P<0.01) and 0.14 kg between 0.4 and 1.4 years of age (P = 0.10), than their maintenance counterparts. Hogget wool was 0.1 pm broader (P<0.05), with a 0.5% units lower coefficient of variation of fibre diameter (P<0.01), and a position of break closer to the staple tip (P<0.001) for progeny of submaintenance ewes than their maintenance counterparts. There were no significant differences in yield, staple length, staple strength and percentage of fibres greater than 30 pm in diameter. Differences in mean fibre diameter arose between 1 and 1.4 years of age, coinciding with the period that the animals were grazing high quality pasture. Effects of maternal undernutrition on mean fibre diameter and Sf: Pf follicle ratios of progeny were most pronounced on the hind leg (P<0.01), and not significant on the front leg. However, variations in other wool quality traits across the body of the hoggets, expressed as a percentage of the midside value, were not significantly affected by maternal undernutrition. Clearly when evaluating management strategies for the pregnant ewe, the effect on lifetime production and quality of wool of their progeny needs to be considered. Merino hoggets that produce an extra 0.14 kg clean wool that is 0.1 pm finer will compensate for some extra management and feeding of their dams during pregnancy to prevent weight loss. If these effects continue throughout the life of the animal, then it will increase the cost effectiveness of feeding to maintain maternal weight over pregnancy.

Surface runoff, soil and nutrient losses from farming systems in the Australian semi-arid tropics

Abstract: Most soils suitable for dryland agriculture in north-west Australia occur in the Daly Basin. These are sesquioxidic soils which include red, yellow and grey earths, and soils related to yellow and red earths. The potential, for these arable soils to be degraded by highly erosive rainfalls, common to the region, is high. Farming practices strongly influence the soil surface characteristics (vegetation cover, roughness, soil strength), which in turn control surface runoff, and sediment detachment and transport. In studies conducted during 1984-89 in the Daly Basin, conventionally tilled catchments, produced 1.5-2 times more runoff and lost 1.5-6 times more soil than their no-tillage counterparts (all catchments were within soil conservation banks). In these conventionally tilled catchments, soil loss was <8.1 t/ha.year. Other studies in the region have shown that, without soil conservation banks, soil loss can be around 100/ha.year under conventional tillage. Little work, however, has been undertaken on farms in the Australian semi-arid tropics to study the movement of nutrients and herbicides (in ionic and adsorbed forms) and further research is warranted.

The response of organic and conventionally grown wheat to superphosphate and reactive phosphate rock

Abstract: In 1991 and 1992 wheat was sown on adjacent properties at Ardlethan in southern New South Wales to assess its response to superphosphate (SP) and reactive phosphate rock (RPR) under conventional and organic management systems. Five rates of P (0, 10, 20, 30, 40 kg/ha) were applied as SP and RPR. No response to RPR was recorded in terms of crop growth or grain yield. However, in both years and on both sites, SP significantly increased plant dry weight at tillering and anthesis, the number of tillers and spikes per plant and grain yield. Superphosphate also increased the P content of grain and the amount of P exported. SP (40 kg P/ha) increased the level of cadmium in the grain, although not beyond permitted maximum concentrations. The use of SP reduced the level of colonisation by vesicular-arbuscular mycorrhizal fungi (VAM). The data indicate that the choice of the organic farmer, not to use SP, incurs a large yield penalty.

Sustaining productivity of a Vertisol at Warra, Queensland, with fertilisers, no-tillage or legumes. 2. Long-term fertiliser nitrogen needs to enhance wheat yields and grain protein

Abstract: Cereal production in the summer-dominant rainfall region of Australia, especially the north-east, has relied heavily on natural soil fertility. Continued cereal production has so depleted the fertility of some soils that corrective strategies are required to restore the production of high protein wheat needed for domestic and export markets. Application of nitrogen (N) fertilisers, along with other strategies to improve soil N status, was evaluated between 1987 and 1994 on a Vertisol located in an area of unreliable winter rainfall. Responses of wheat grain yield and protein content to applied N (0-150 kg/ha) under zero tillage (ZT) and conventional tillage (CT) were determined each year, except 1991 when severe drought prevented wheat sowing. The ZT practices increased grain yields, particularly in 1988 and 1992-93 when antecedent soil water supplies were moderate (about 1 m wet soil in 1988 and 1992) or low (about 0.6 m wet soil in 1993), apparently due to increased antecedent soil water. Tillage practice had little effect on available nitrate-N (kg/ha) to 1.5 m, but the greater water supply in ZT soil usually benefited the wheat crop when N was applied. Applying N increased returns from 5 of the 7 crops because of grain yield and/or grain protein responses. Grain yield responses were inconsistent in the year of fertiliser application where no N fertiliser had been applied to preceding crops. Nevertheless, grain protein usually increased with increasing N application at sowing, except in 1994, when drought after sowing prevented secondary root development and fertiliser uptake. Where N was applied with each successive crop, the crops receiving small N applications (0, 12.5 or 25 kg/ha.crop) produced grain of a low protein concentration ( 11.5%, due to the low market value of low protein wheat, or because of lower grain yields. Routine N application to crops over the period 1987-94, which included the longest drought (1990-94) in the lifetime of most producers, caused similarly inconsistent grain yield increases but increased grain protein concentrations (>11.5%) in all except the first crop (1987). Increased frequency of high protein wheat and a high anticipated market value of the higher protein grain should encourage greater producer confidence with routine application of N throughout this region.

Narbon bean (Vicia narbonensis L.): a promising grain legume for low rainfall areas of south-western Australia

Abstract: The phenology, growth, seed yield and yield components of a number of introduced narbon bean (Vicia narbonensis L.) accessions and F9 breeding lines were compared with faba bean (Vicia faba L. cv. Fiord) or field pea (Pisum sativum L. cv. Dundale) at 3 sites in 2 seasons. All narbon bean accessions had slow development, for example all accessions reached 50% flowering 9-35 days later than faba bean or field pea depending on the accession, site and season. Dry matter production near flowering ranged from 1.0 to 2.3 tlha and the growth of the best accessions was comparable with faba bean. In general, the accession ATC 60114 collected in the Beka'a Valley, Lebanon, produced the greatest seed yield across the sites and seasons (on average 1.52 t/ha). In 1993, the best narbon bean accession produced seed yields that ranged from 59% of the faba bean seed yield at the wettest site to 121% at the driest site. In the following year, one of the driest in decades, 6 accessions produced seed yields of more than 1.0 t/ha, similar to field pea. Seed yield was negatively correlated with days to flowering, podding and maturity, suggesting that yield could be improved by selecting for more rapid development. Most accessions retained the majority of their leaves at maturity, but showed some degree of pod shattering and a moderate level of lodging at maturity. Genotypic variation in all these characters was evident. Further selection and breeding, together with appropriate agronomic packages will improve the adaptation of narbon bean to mediterranean-type environments of southern Australia. However, the adoption of narbon bean in Australian agriculture will depend on its marketability and acceptance by the stockfeed industry, and its on-farm utility.

Colonisation of wheat in southern New South Wales by vesicular-arbuscular mycorrhizal fungi is significantly reduced by drought

Abstract: Summary. Colonisation of wheat crops by vesiculararbuscular mycorrhizal (VAM) fungi was examined on a pair of adjacent organic and conventionally managed farms in southern New South Wales during 1993-94. Although intended to be part of a larger study on the roles of VAM fungi in organic and conventional farming systems, the severe drought of 1994 allowed an examination of the effects of drought on VAM fungi. In 1993, rainfall was above average, crop growth was good and VAM fungi colonised between 40 and 70% of crop root length. In 1994, low rainfall resulted in poor crop growth, and colonisation by VAM fungi was significantly lower than in 1993, ranging between 5 and 16% in the crops most affected by the drought. Wheat plants adjacent to tree lines exhibited particularly poor growth and low VAM colonisation, presumably due to the trees competing with the crop for water. The lower colonisation of crops by VAM fungi in 1994 resulted in reduced inoculum levels in the soil which could affect growth of a subsequent VAM-dependent crop. In contrast to the results of research carried out under conditions of milder drought stress, the low level of VAM colonisation found in this study suggests that the VAM fungi had no significant role in alleviating the drought stress experienced by the crop.

Simulation of a legume ley farming system in northern Australia using the Agricultural Production Systems Simulator

Abstract: An innovative ley farming system, involving cereal crops grown in rotation with pasture legumes, has been tentatively adopted by farmers in the semi-arid tropics of northern Australia. Yet, after more than a decade of experimental research, the long-term

Long-season wheats extend sowing opportunities in the central wheat belt of Western Australia

Abstract: Wheat cultivars and crossbreds with different maturities were tested at a range of sowing times from 1989 to 1991 at 13 sites in the central wheat belt of Western Australia. The aim was to determine if long-season cultivars would allow sowing before mid May, the earliest period estimated by previous studies. Rainfall in the growing season ranged from 176 to 330 mm. Long season cultivars showed the potential to extend the sowing season from early May into late April without loss of yield. Mid-season cultivars reached their maximum yields from sowings in May and short-season cultivars yielded most from late May and early June sowings. The optimum flowering period for the study area over the 3 years was 2-22 September, a period similar to earlier estimates made using only short- and midseason cultivars. It was concluded that, despite considerable variability from year to year both within and between sites, the optimum flowering period did not vary greatly on average and was not greatly affected by the use of long-season cultivars. Sowing after the optimum time resulted in slightly increased grain protein percentages but losses in the value of grain yield would have more than offset increases in the value of grain protein. At the nitrogen rates used in the experiments (80 kg/ha), grain proteins over 11.5% [the minimum for the Australian Hard (AH) grade] were only achieved on average for the long-season AH cultivar Blade at sowing times later than its optimum for yield. The Australian Standard White cultivars, however, mostly achieved 10% protein, an acceptable minimum for that grade, from sowings made at their optimum time. Hectolitre weights fell below the delivery standard of 74 kg/hL in only 3 grain samples. These were all from short-season cultivars sown before their optimum time. Fifteen grain samples from 4 sites contained small grain sievings (2-mm slotted screen) above the delivery standard. Eleven of these samples came from cultivars sown outside their optimum sowing times.

Farming systems in the Australian semi-arid tropics-a recent history

Abstract: The recent history of dryland farming in the Australian semi-arid tropics is discussed briefly against the background of national and state policies, established following World War II, aimed at increasing the population and development of northern Australia. Some reference is also made to irrigation as a means of overcoming limitations imposed by rainfall and to complement dryland farming systems. The environmental and socio-economic constraints whch have so far limited commercial agriculture in the Australian semi-arid tropics are highlighted. Efforts, particularly in north-west Australia, to develop sustainable farming systems based on legume pasture leys and livestock production in conjunction with annual cropping, as a basis for closer settlement, are reviewed. These attempts, which began in the 1960s and stemmed from earlier post-war agricultural research in the region, initially relied on a pasture legume (Stylosanthes humilis cv. Townsville stylo) and conventional tillage. Farming system development continues today using new legume species (e.g. Stylosanthes hamata cv. Verano and Centrosema pascuorum cv. Cavalcade) and no-tillage cropping technology. This paper documents the history of agricultural and research development, and commercial practice in the Australian semi-arid tropics.

The performance of Brahman-Shorthorn and Sahiwal-Shorthorn beef cattle in the dry tropics of northern Queensland. 5. Scrotal circumference, temperament, ectoparasite resistance, and the genetics of growth and other traits in bulls.

Abstract: The genetics of growth to 24 months, scrotal circumference (SC) at 24 months and temperaments at 6, 12 and 18 months in 7 year groups of F2 et seq., 1/2 Brahman, 1/2 Sahiwal, 3/4 Brahman and 3/4 Sahiwal bulls were investigated in the dry tropics of northern Queensland. Cattle tick (Boophilus microplus) and buffalo fly (Haematobia irritans exigua) resistance were also assessed at 24 months. Scrotal circumference at 24 months was highest in 1/2 Sahiwal crosses (28 cm v. 26-27 cm; P 0.9); however, the rG of weaning weight with postweaning seasonal growth rates to 24 months were consistently negative (-0.09 to -0.71; P>0.05). The rG of SC with post-weaning growth rates were negative (-0.4 to -0.8). The rG of SC with weights up to 18 months were not significantly different to zero, but tended to be negative with weight at 24 months.

Field evaluation of micropropagated and conventionally propagated ginger in subtropical Queensland

Abstract: The growth and performance of micropropagated ginger (Zingiber officinale Roscoe) was compared with 'seed'-derived plants in field trials conducted in south-eastern Queensland. In the first generation ex vitro, micropropagated plants had significantly (P<0.01) reduced rhizome yield with smaller knobs and more roots. Micropropagated plants had a greater (P<0.01) shoot: root (rhizome) ratio compared with seed-derived plants. Shoots from micropropagated plants were also significantly (P<0.01) smaller with a greater number of shoots per plant. The unusual shoot morphology of the micropropagated plants did not appear to be related to the presence of benzylaminopurine, a plant growth hormone added to the multiplication medium, as plants subcultured for 3 cycles on a hormone-free medium also exhibited similar characteristics. Seed collected from the micropropagated plants and seed-derived plants was harvested and, despite the micropropagated seed being significantly (P<0.01) smaller, by the second generation ex vitro there were no significant differences between the treatments. Factors that can improve rhizome size, while reducing production costs, need to be identified before micropropagated plants can be recommended for routine use in the ginger industry as a source of disease and pest-free planting material.

Supplementation of high fecundity Border Leicester x Merino ewes with a high protein feed : its effect on lamb survival

Abstract: Two hundred and fifty Border Leicester x Merino ewes (40% heterozygous for the Booroola Fec B gene) were used in an experiment, replicated over 2 years, to examine the effects of cottonseed meal-based supplementation on lamb survival, birth, marking and weaning weight, as well as, liveweight and fleece characteristics of ewes. From 50 to 100 days of pregnancy, half of the ewes were supplemented with 80 g/head.day. The supplemented group was then split according to litter size and, until 30 days after lambing, were offered pellets at 80, 160 and 220 g/head .day, respectively, for ewes bearing single, twin and triplet (or more) lambs. Over the 2 years, ewes averaged 2.11 lambs per parturition and supplementation significantly increased lamb survival to weaning (73 v. 58%) with no interaction with litter size. Although supplementation had a positive effect on birth weight of all but twins, the effects of supplementation on survival were independent of birth weight effects. Significant effects of year, sire breed and litter size on lamb survival and birth weight were also noted. No effects of supplementation were apparent on lamb growth while ewe age, sire breed, sex and rearing rank all significantly influenced growth rates. Ewe weights, fleece weights and staple strength were significantly influenced by year, ewe age and litter size but not by supplementation. These findings indicate the benefits to lamb survival of providing a 'bypass' protein supplement to high fecundity flocks even when ewes are grazing good quality pastures.

Gibberellic acid detection of dwarf offtypes in micropropagated Cavendish bananas

Abstract: Detection of dwarf offtypes produced by micropropagation of Cavendish bananas (Musa spp.) cultivars New Guinea Cavendish and Williams was achieved by spraying gibberellic acid (GA3) solution (289 pmol/L) onto deflasked plants and measuring various plantlet responses. The most useful identification criterion was elongation of the sheath of the first leaf to form after GA3 application. Elongation of this structure was about 2-fold greater in normal plants than observed in dwarfs. Similar measurements taken earlier during in vitro culture or later during plant establishment in soil were not as useful in discriminating between normals and dwarfs as the measurements made at deflasking. The similar GA3-induced elongation response of the dwarf offtype and that of the naturally occurring dwarf cultivar Dwarf Parfitt suggests that the mechanism for dwarfism could be the same in the 2 cases.

Grazing a saltbush (Atriplex-Maireana) stand by Merino wethers to fill the 'autumn feed-gap' experienced in the Western Australian wheat belt

Abstract: Three-year-old Merino wethers were grazed at 4 stocking densities (15, 20, 25 and 30 sheep/ha) in 3 consecutive autumns on saltbush forage. About 50% of edible material was leaf [70% digestible dry matter (DDM), 8.9% crude protein (CP)] and 50% was small stems <5 mm diameter (40% DDM and 4.5% CP). In 1992, 9-month-old wethers also grazed the saltbush stand at 30 sheep/ha. Liveweight initially increased by 1-3 kg during the first 14 days of grazing, then declined at 60-100 g/day until the diminishing forage reserves became critical, by which time the stand had provided for about 450 grazing-days/ha. The performance of the 9-month-old wethers was comparable with the 3-year-old sheep at equivalent grazing pressure. In 1992, the tensile strength of wool staples from the 3-year-old sheep grazed at the higher density of 30 sheep/ha, 17.2 N/ktex, was weaker (P<0.05) than staples from sheep grazed at 15 and 20 sheep/ha, 27.1 N/ktex, and 25 sheep/ha, 24.9 N/ktex. Saltbush plantations can be used to provide a feed source which could partly fill the 'autumn feed-gap' for <9-month-old dry sheep. Grazing at <20 sheep/ha, removal of sheep from the saltbush before the mean liveweight declines below that at the start of grazing, and provision of a reliable supply of water will avoid low staple strength wool. More productive stands of saltbush, grown together with winter-active plant species, are needed to improve the economic viability of this grazing resource.

Effect of perches and solid sides on production, plumage and foot condition of laying hens housed in conventional cages in a naturally ventilated shed

Abstract: The effect of modified cages on production, shell quality, feather cover and foot condition was measured in 2 Australian commercial laying strains housed in a naturally ventilated laying shed from 18 to82 weeks of age. Two cage modifications were investigated. Firstly , the inclusion of a perch within the cage, and secondly, the installation of solid sides. Compared with normal cages, installation of a perch in a cage reduced food intake (5.3%) and liveweight (4.5% at 82 weeks) and improved feather cover around the vent (feather score of 2.15 to 2.66). This was offset by a decrease in egg production (2.4%), shell weight (1.5%) and thickness (11%), an increase in cracked (53.8%) and dirty eggs (28.9%), and an increase in claw length (9.2%). Relative to control cages, the provision of solid sides in cages improved overall feather cover of hens (feather score of 2.46 to 2.67), but there was a 54.5% increase in hen mortality during a period of hot weather. Additional modifications to the cage are required to optimise the benefit of perches. Similarly, improvement in ventilation and cooling in naturally ventilated sheds are required to maximise the benefits of solid-sided cages for hens and avoid heat stress.

Sowing time and tillage practice affect chickpea yield and nitrogen fixation. 1. Dry matter accumulation and grain yield

Abstract: Summary. Mean protein concentrations in wheat (Triticum aestivum) on the Darling Downs of southern Queensland have fallen below 10% in recent years, preventing farmers from obtaining 'Prime Hard' status (13.0%) for their wheat crop. Two management options, for improving this situation are applications of nitrogenous fertiliser in a wheat monoculture or inclusion of a legume in rotation with wheat. Long-term trials at Warra, on the western Darling Downs, resulted in the selection of chickpea (Cicer arietinum) as a useful grain legume cash crop with potential for improvement of its nitrogen (N) fixing ability through management. This 2-year study examined the effect of sowing time and tillage practice on dry matter yield, grain yield, N accumulation and N2 fixation in chickpea and the subsequent soil N balance. There were 3 sowing times during autumn and winter of each year using conventional tillage (CT). Zero tillage (ZT) was introduced after the first crop for all sowing times. Greater total dry matter yield and grain yield (4.18-5.95 and 1.63-2.25 t/ha, respectively) resulted from sowing in autumn or early winter than from sowing in late winter (3.39-3.86 and 0.97-1.22 kgha, respectively). The effects of tillage practice were variable, depending on growth stage. At harvest, ZT plots produced greater total dry matter yield (4.20 tha) and grain yield (1.94 tlha) than CT plots (3.01 and 1.29 tha, respectvely), whereas at the time of maximum dry matter, yield was higher under CT for autumn sowings, and under ZT for winter sowings.

Genetic diversity of Kensington Mango in Australia

Abstract: The genetic diversity of Kensington mangoes (Mangifera indica L.) was investigated using random amplified polymorphic DNA (RAPD) analysis. DNA was extracted from leaves of 27 'Kensington Pride', 2 'R2E2' and 1 seedling. RAPD analysis with 10 oligonucleotide primers allowed the scoring of 107 markers. The R2E2 trees (20% dissimilarity) and the seedling (10% dissimilarity) were distinct from the Kensington Pride. However, there was very little evidence of significant genetic variation within Kensington Pride selections. Fifteen of the selections were identical in all 107 markers. Only 2 selections, WEAN2 and ML2N1, differed by more than 5%. These plants provide the best options for use in genetic improvement of the Kensington Pride mango. Many of the differences found in Kensington mango orchards may be due to environmental factors not genetic variations.

Creep feeding and prepartum supplementation effects on growth and fertility of Brahman-cross cattle in the dry tropics.

Abstract: Post-partum anoestrus is a primary contributor to low branding rates in Bos indicus cattle herds in the dry tropics of northern Australia [Entwistle, K. W. (1983). Australian Meat Research Committee Review No. 43]. To increase branding rates, it was hypothesised that creep feeding for a short period in mid-late lactation during the latter half of the growing season may trigger an earlier onset of post-partum oestrus cycling, just as short-term, high-level, prepartum supplementation can achieve. Two experiments were conducted using F(n) Brahman-cross cows (1/2, 5/8 and 3/4 crosses with Beef Shorthorn) which calved from late October to late January. Cows were mated from mid-late January to mid-April. Calves in one treatment in both experiments had ad libitum access to creep feed (calf pellets: 16% crude protein, 10 MJ ME/kg) for 40-42 days from late February to early April. In experiment 2, the effects on cow growth and fertility due to supplementation with either cottonseed meal (1.5 kg/day) or molasses with 7.4% (w/w) urea for 49 days late in the dry season before calving ('spike' feeding) were also evaluated. Control cattle were unsupplemented. Creep feed was only consumed at 0.1 and 0.4 kg/day in experiments 1 and 2, respectively. Short-term creep feeding had no consistent effects on cow liveweights, condition, or fertility, or on calf growth and temperaments under extensive grazing conditions during the tropical wet season. Spike feeding reduced weight loss by 0.2-0.4 kg/day (P<0.01). The effects on liveweights did not persist into the wet season. There were no effects on cow fertility in this year of extreme weather conditions, when 4 months of nutritional and climatic stress followed supplementation.

Growth and seed yield of vetches (Vicia spp.) in south-western Australia

Abstract: The growth and seed yield of 5 vetch (Vicia) cultivars representing Vicia sativa, V. benghalensis and V. villosa were compared at 8 sites over 2 years in south-western Australia. The vetches showed considerable potential as grain and forage legume crops in the low to medium rainfall areas of the Western Australian cereal belt. Cultivars of V. sativa showed the most potential in terms of dry matter and seed yield, and on average across sites and seasons both Languedoc and Blanchefleur produced over 2.5 t/ha of dry matter at flowering: Machine-harvested seed yields were over 1.6 t/ha. Cultivars of V. benghalensis and V. villosa produced considerably less dry matter at flowering and had lower harvest index (0.14-0.42) and seed yield < 4 t/ha) when compared with the V. sativa cultivars, possibly due to their poor growth rates and delayed phenology. Early Purple, an early flowering and maturing selection from the V. benghalensis cultivar Popany, showed improved adaptation and seed yield at many low rainfall sites. Nevertheless, Languedoc, Blanchefleur and Early Popany are all considered late flowering (up to 126 days) compared with grain legumes adapted to this environment, and further improvement in vetch species could be achieved by selecting for more rapid development. Both soft-seededness and non-shattering pods should also be high priorities for vetch selection and/or breeding programs. It is concluded that vetch species may have a role in farming systems in Western Australia for the production of fodder, hay, grain or green manure while providing the other rotational benefits of legumes on fine-textured neutral to alkaline and shallow duplex soils where narrow-leafed lupin is poorly adapted.

Evaluation of Australian commercial honey bees for hygienic behaviour, a critical character for tolerance to chalkbrood

Abstract: Chalkbrood of honey bees (Apis mellifera) is caused by Ascosphaera apis, and is new to Australia. As yet, no treatment or prophylaxis is available for this disease. The best prospects for control are likely to come from the use of 'hygienic' bees, those with a strong genetic tendency to uncap and remove dead pupae, together with good beekeeping practice. Ten strains of Australian commercial honey bee were evaluated for hygienic behaviour. Dead pupae were inserted into the colonies and checked after 3, 5 and 7 days for the number of pupae removed. Most colonies (80%) were non-hygienic and hence likely to be susceptible to chalkbrood. However, 2 strains provided good overall performance in the test and comprised 1 or 2 colonies that were highly hygienic. Colonies were evaluated 3 times, and the good performance of these colonies was repeatable across trials. These data suggest that hygienic behavioural morphs exist in Australia's commercial bee strains, and it is unnecessary to obtain breeding stock from overseas for this reason alone. Selective breeding, with relatively simple techniques which can be used by beekeepers and queen breeders, should produce suitable genotypes.

Production responses of dairy cows grazing well-managed kikuyu (Pennisetum clandestinum) pastures to energy and protein supplementation

Abstract: Three studies were conducted to examine the production response of Friesian cows grazing well-managed lukuyu (Pennisetum clandestinum) pasture to supplementation with a cereal grain concentrate, with and without the inclusion of formaldehyde-treated protein meal. Mean (¦ s.e.) levels of nutrients in the pasture (g/kg DM) on offer were: 205 ¦ 3 crude protein; 683 ¦ 7 in vitro organic matter digestibility; 239 ¦ 2 acid detergent fibre; 615 ¦ 8 neutral detergent fibre and 4.47 ¦ 0.16, 2.51 ¦ 0.06, 31.96 ¦ 0.98, 0.39 ¦ 0.03 and 3.18 ¦ 0.09 of calcium, phosphorus, potassium, sodium and magnesium, respectively. Study 1 was a 3-farmlet study conducted over 45 days (March-April 1993) involving cows 5-6 months into lactation, which compared 3 levels of concentrate feeding at 0 (R0), 3 (R3) or 6 (R6) kg crushed barley/cow.day. Study 2 was an 18-day extension of study 1 with animals in the seventh month of lactation. The concentrate fed was 72% barley and 24% formaldehyde-treated sunflower meal. Pasture intake of individual cows was determined using an alkane technique. Mean milk yields (L/cow. day) in study 1 were 14.2, 18.3 and 18.0, and in study 2 were 12.5, 18.5 and 17.4 for treatments R0, R3 and R6, respectively. Milk fat (3.77 v. 3.26%), but not milk protein, content of the Ro cows was significantly higher than R6 cows in study 1 only. In study 2, the apparent whole-diet digestibility remained constant as concentrate level rose, indicating a negative effect of concentrate fed on forage digestibility in the absence of buffers. Study 3 was a 3 x 4 factorial design plus a 'control' group (0.5 kg barley/cow.day used as a carrier for minerals) to examine the milk production response to 3 levels of concentrate feeding (3, 6 and 9 kg/cow.day) with 4 levels of formaldehyde-treated canola meal (FTCM; 0, 20, 40 and 60% of concentrate). Rations were iso-energetic within levels of concentrates fed. The control group had significantly lower milk production (17.2 L/cow.day), as well as milk protein (2.90%), plasma urea (PU) (5.90 mmol/L) and P-hydroxybutyrate (G-OHB) (0.525 mmo1L) than other treatment groups. The mean milk production response of 0.6 L milk/kg concentrate fed in study 3 at the 3 kg/day level of feeding was lower than observed in studies 1 and 2 (1.4 and 2.0 L/kg concentrate, respectively). The level of metabolisable energy in the concentrate in study 3 had a significant influence on milk production, milk fat and milk protein levels. Plasma glucose and G-OHB levels significantly increased with the incorporation of FTCM into the concentrate. Nonesterified fatty acid levels dropped significantly below levels of other treatments at the lowest level of inclusion of FTCM. PU levels generally increased in response to increasing metabolisable energy and inclusion of FTCM in the concentrate, with an interaction between them. Milk urea (MU) levels (mmol/L) showed a significant linear (P<0.001; r2 = 0.44) relationship to PU levels (mmol/L) as follows: MU = 0.167 + 0.272PU.

Predicting resistance and managing susceptibility to cyromazine in the Australian sheep blowfly Lucilia cuprina

Abstract: Four cyromazine-resistant variants of Lucilia cuprina were selected after ethyl methanesulfonate mutagenesis and screening above the concentration of cyromazine lethal to susceptibles. Resistance is controlled by a single gene in each variant. Two resistance loci have been identified, one (Cyr 4) closely linked to the marker 'reduced eyes' on chromosome IV, the other (Cyr 5) closely linked to the 'stubby bristles' marker on chromosome V. Concentration-mortality line analysis shows resistance ratios are low (1.5-3x). One variant [Cyr 4(2)] is viable as a homozygote, the others are lethal [Cyr 4(1)] or, at best subvital [Cyr 5(1) and Cyr 5(2)]. Competition experiments between resistant heterozygotes and susceptibles show that resistance to cyromazine is selected for over a limited range of concentrations. The capacity of laboratory studies to predict likely resistance mechanisms before they evolve in the field is discussed. The use of genetic, toxicological and relative fitness data arising from these studies to devise the most effective strategies of insecticide usage while minimising the evolution of resistance is emphasised.

Sowing time and tillage practice affect chickpea yield and nitrogen fixation .2. Nitrogen accumulation, nitrogen fixation and soil nitrogen balance

Abstract: Following long-term studies at Warra, on the western Darling Downs, chckpea (Cicer anetinum) was selected as a useful grain legume cash crop with potential for improvement of its nitrogen (N) fixing ability through management. This 2-year study examined the effect of sowing time and tillage practice on dry matter yield, grain yield (Horn et al. 1996), N accumulation, N2 fixation, and the subsequent soil N balance. Generally, greater N accumulation resulted from sowing in late autumn-early winter (89-117 kg N/ha) than sowing in late winter (76-90 kg N/ha). The amount of N2 fixed was low in both years (15-32 kg N/ha), and was not significantly affected by sowing time or tillage. The potential for N2 fixation was reduced in both years due to high initial soil nitrate levels and low total biomass of chickpea because of low rainfall. Nitrogen accumulation by grain was higher under zero tillage (ZT) than conventional tillage (CT) for all sowing times, and this affected the level of grain N export. The consequence of low N2 fixation and high N export in chickpea grain was a net loss of total soil N, (2-48 kg N/ha under CT and 22-59 kg N/ha under ZT). Management practices to ensure larger biomass production and lower soil nitrate-N levels may result in increased N2 fixation by chickpea and thus a positive soil N balance.

Diet selection by cattle grazing Stylosanthes-grass pastures in the seasonally dry tropics: effect of year, season, stylo species and botanical composition

Abstract: The dietary preference of cattle grazing Stylosanthes-based pastures in the seasonally dry tropics of North Queensland was studied using faecal carbon ratios (S13C) to determine grass-legume proportions. Estimates were made at monthly intervals for several years in 1 experiment to determine the effect of year, season and botanical composition on dietary stylo proportions. In another experiment, the effect of stylo cultivars (Verano and Seca) on dietary preference was monitored for 17 months. Where pastures provided ample opportunity for selection, cattle showed a strong preference for grass in the early wet season and in the late dry season. The proportion of stylo in the diet increased during the wet season and reached peak proportions (as high as 80%) in the late wet season or early dry season. Dietary stylo proportions decreased as pastures dried off and as the stylo shed leaf or became more stemmy. The length of the wet season and the amount and distribution of rainfall had a major influence on the seasonal pattern of diet selection. Stylo rarely fell below 20% in the diet. On an annual basis, stylo accounted for about 45% of the diet which was appreciably higher than the proportion of stylo in the pasture. Dietary stylo proportions were higher on Seca-based pasture than on Verano-based pasture. The avoidance of stylo in the early wet season was less pronounced with Seca compared with Verano. Later in the season Seca was the dominant dietary component for a much longer period than Verano. The effect of botanical composition on dietary grass-legume proportions varied between and within years. Correlations between grass-legume proportions in the pasture and in the diet were highest in the late dry season and early wet season when preference for grass was strongest. At the end of the wet season when cattle preferred stylo, dietary stylo was not related to pasture stylo content except in a drought year. Averaged over the full year, dietary stylo content was significantly correlated with pasture stylo content in all years and the correlation was highest in a drought year when there was a high level of utilisation and less opportunity for selection. A simple model relating dietary stylo to pasture stylo was developed and is discussed.