Growth and carcass characteristics of cast-for-age Merino ewes fed sorghum-based feedlot diets

Grain feeding low bodyweight, cast-for-age (CFA) sheep from pastoral areas of eastern Australia at the end of the growing season can enable critical carcass weight grades to be achieved and thus yield better economic returns. The aim of this work was to compare growth and carcass characteristics for CFA Merino ewes consuming either simple diets based on whole sorghum grain or commercial feed pellets. The experiment also compared various sources of additional nitrogen (N) for inclusion in sorghum diets and evaluated several introductory regimes. Seventeen ewes were killed initially to provide baseline carcass data and the remaining 301 ewes were gradually introduced to the concentrate diets over 14 days before being fed concentrates and wheaten hay ad libitum for 33 or 68 days. Concentrate treatments were: (i) commercial feed pellets, (ii) sorghum mix (SM; whole sorghum grain, limestone, salt and molasses) + urea and ammonium sulfate (SMU), (iii) SMU + whole cottonseed at 286 g/kg of concentrate dry matter (DM), (iv) SM + cottonseed meal at 139 g/kg of concentrate DM, (v) SMU + virginiamycin (20 mg/kg of concentrate) for the first 21 days of feeding, and (vi) whole cottonseed gradually replaced by SMU over the first 14 days of feeding. The target carcass weight of 18 kg was achieved after only 33 days on feed for the pellets and the SM + cottonseed meal diet. All other whole grain sorghum diets required between 33 and 68 days on feed to achieve the target carcass weight. Concentrates based on whole sorghum grain generally produced significantly (P < 0.05) lower carcass weight and fat score than pellets and this may have been linked to the significantly (P < 0.05) higher faecal starch concentrations for ewes consuming sorghum-based diets (270 v. 72 g/kg DM on day 51 of feeding for sorghum-based diets and pellets, respectively). Source of N in whole grain sorghum rations and special introductory regimes had no significant (P > 0.05) effects on carcass weight or fat score of ewes with the exception of carcass weight for SMU + whole cottonseed being significantly lower than SM + cottonseed meal at day 33. Ewes finished on all diets produced acceptable carcasses although muscle pH was high in all ewe carcasses (average 5.8 and 5.7 at 33 and 68 days, respectively). There were no significant (P > 0.05) differences between diets in concentrate DM intake, rumen fluid pH, meat colour score, fat colour score, eye muscle area, meat pH or meat temperature.

Seasonal changes in pasture quality and diet selection and their relationship with liveweight gain of steers grazing tropical grass and grass-legume pastures in northern Australia.

The variation in liveweight gain in grazing beef cattle as influenced by pasture type, season and year effects has important economic implications for mixed crop-livestock systems and the ability to better predict such variation would benefit beef producers by providing a guide for decision making. To identify key determinants of liveweight change of Brahman-cross steers grazing subtropical pastures, measurements of pasture quality and quantity, and diet quality in parallel with liveweight were made over two consecutive grazing seasons (48 and 46 weeks, respectively), on mixed Clitoria ternatea/grass, Stylosanthes seabrana/grass and grass swards (grass being a mixture of Bothriochloa insculpta cv. Bisset, Dichanthium sericeum and Panicum maximum var. trichoglume cv. Petrie). Steers grazing the legume-based pastures had the highest growth rate and gained between 64 and 142 kg more than those grazing the grass pastures in under 12 months. Using an exponential model, green leaf mass, green leaf %, adjusted green leaf % (adjusted for inedible woody legume stems), faecal near infrared reflectance spectroscopy predictions of diet crude protein and diet dry matter digestibility, accounted for 77, 74, 80, 63 and 60%, respectively, of the variation in daily weight gain when data were pooled across pasture types and grazing seasons. The standard error of the regressions indicated that 95% prediction intervals were large (+/- 0.42-0.64 kg/head.day) suggesting that derived regression relationships have limited practical application for accurately estimating growth rate. In this study, animal factors, especially compensatory growth effects, appeared to have a major influence on growth rate in relation to pasture and diet attributes. It was concluded that predictions of growth rate based only on pasture or diet attributes are unlikely to be accurate or reliable. Nevertheless, key pasture attributes such as green leaf mass and green leaf% provide a robust indication of what proportion of the potential growth rate of the grazing animals can be achieved.

Research note: poplar box (Eucalyptus populnea) growth rates in thinned and intact woodlands in central Queensland

A 19-year data set, which highlights the rapid growth rate in basal area of trees in thinned plots compared with unthinned controls, is presented. These results support the contention that, following tree thinning, basal area of retained trees will increase more rapidly than that of trees on unthinned areas. Indications are that pre-thinning levels in tree basal area will again be reached before the cost of treatment can be recouped by increased pasture and livestock production.

Queensland Coastal Wetland Resources: Cape Tribulation to Bowling Green Bay

This report provides key resource data for the ongoing assessment of the requirement for additional Marine Protected Areas (e.g. FHAs under the Queensland Fisheries Act 1994) in regions of high fish habitat value in northern Queensland from Cape Tribulation to Bowling Green Bay (hereafter referred to as the Study Area). The study also provides baseline information on the coastal wetlands within this Study Area for consideration in the Ramsar site nomination process. The Study Area extends from Cape Tribulation (16o 6’S, 145o 24’E) to Bowling Green Bay (19o 30’S, 147o 24’E) in tropical north Queensland. The project aimed to: 1. document and map the coastal wetland communities of the Study Area; 2. document levels of existing disturbance to and protection of the wetlands; 3. examine existing recreational, indigenous and commercial fisheries resources in the region; 4. evaluate the conservation values of the areas investigated from the viewpoint of fisheries productivity and as habitat for important and/or threatened species for future FHA/MPA declaration. Dataset URL Link: Queensland Coastal Wetlands Resources Mapping data. [Dataset]

Analysis and Modelling of the Effects of Water Stress on Maize Growth and Yield in Dryland Conditions.

It is essential to provide experimental evidence and reliable predictions of the effects of water stress on crop production in the drier, less predictable environments. A field experiment undertaken in southeast Queensland, Australia with three water regimes (fully irrigated, rainfed and irrigated until late canopy expansion followed by rainfed) was used to compare effects of water stress on crop production in two maize (Zea mays L.) cultivars (Pioneer 34N43 and Pioneer 31H50). Water stress affected growth and yield more in Pioneer 34N43 than in Pioneer 31H50. A crop model APSIM-Maize, after having been calibrated for the two cultivars, was used to simulate maize growth and development under water stress. The predictions on leaf area index (LAI) dynamics, biomass growth and grain yield under rain fed and irrigated followed by rain fed treatments was reasonable, indicating that stress indices used by APSIM-Maize produced appropriate adjustments to crop growth and development in response to water stress. This study shows that Pioneer 31H50 is less sensitive to water stress and thus a preferred cultivar in dryland conditions, and that it is feasible to provide sound predictions and risk assessment for crop production in drier, more variable conditions using the APSIM-Maize model.

Prothoracic Gland Semiochemicals of Green Lacewings.

Adult chrysopids have paired prothoracic glands (PG) that are thought to produce defensive secretions (allomones). We analyzed PG extracts of the following green lacewings from North and South America, Australia, and China: Ceraeochrysa cubana (Brazil); Chrysopa (= Co.) oculata, Co. nigricornis, Co. incompleta, Co. quadripunctata (USA), and Co. septempunctata (China); Chrysoperla (= Cl.) rufilabris (USA) and Cl. sp. (Brazil); Plesiochrysa ramburi and Mallada spp. (Australia). PG secretions are characteristic for species within a genus, except for Chrysopa spp. (Z)-4-Tridecene is ubiquitous, but (Z,Z)-4,7-tridecadiene is a major PG constituent in some Chrysopa spp. and in P. ramburi. Earlier reports that Co. oculata and Co. nigricornis produce 1-tridecene were shown to be in error. Chrysopa PG secretions are distinguished by the presence or absence of N-3-methylbutylacetamide, plus skatole (3-methylindole). Skatole is also identified for the first time from the Plesiochrysa and Ceraeochrysa. The PG secretion in Plesiochrysa ramburi is characterized by the presence of (Z)-4-undecene instead of (Z)-4-tridecene, and N-3-methylbutylpropanamide instead of the acetamide, resembling the PG secretions of Chrysopa nigricornis, Co. septempunctata and Co. incompleta. The chemotaxonomic value of PG semiochemicals is discussed, including evidence for subgroups within the genus Chrysopa as it now stands.

Cynodon dactylon, Green Couch, Turfgrass, Bermuda Grass 'Hatfield'

Low-growing plant with dark green foliage selected in 1983 from a population of green couch plants found in Gympie, Qld. Breeder: Graham Hatfield, Gympie, Qld. Application No. 2002/304. Australian PBR Certificate Number 2565, Granted 20 August 2004.

Adaptation and management of Australian buffalograss cultivars for shade and water conservation

Soft-leaf buffalo grass is increasing in popularity as an amenity turfgrass in Australia. This project was instigated to assess the adaptation of and establish management guidelines for its use in Australias vast array of growing environments. There is an extensive selection of soft-leaf buffalo grass cultivars throughout Australia and with the countrys changing climates from temperate in the south to tropical in the north not all cultivars are going to be adapted to all regions. The project evaluated 19 buffalo grass cultivars along with other warm-season grasses including green couch, kikuyu and sweet smother grass. The soft-leaf buffalo grasses were evaluated for their growth and adaptation in a number of regions throughout Australia including Western Australia, Victoria, ACT, NSW and Queensland. The growth habit of the individual cultivars was examined along with their level of shade tolerance, water use, herbicide tolerance, resistance to wear, response to nitrogen applications and growth potential in highly alkaline (pH) soils. The growth habit of the various cultivars currently commercially available in Australia differs considerably from the more robust type that spreads quicker and is thicker in appearance (Sir Walter, Kings Pride, Ned Kelly and Jabiru) to the dwarf types that are shorter and thinner in appearance (AusTine and AusDwarf). Soft-leaf buffalo grass types tested do not differ in water use when compared to old-style common buffalo grass. Thus, soft-leaf buffalo grasses, like other warm-season turfgrass species, are efficient in water use. These grasses also recover after periods of low water availability. Individual cultivar differences were not discernible. In high pH soils (i.e. on alkaline-side) some elements essential for plant growth (e.g. iron and manganese) may be deficient causing turfgrass to appear pale green, and visually unacceptable. When 14 soft-leaf buffalo grass genotypes were grown on a highly alkaline soil (pH 7.5-7.9), cultivars differed in leaf iron, but not in leaf manganese, concentrations. Nitrogen is critical to the production of quality turf. The methods for applying this essential element can be manipulated to minimise the maintenance inputs (mowing) during the peak growing period (summer). By applying the greatest proportion of the turfs total nitrogen requirements in early spring, peak summer growth can be reduced resulting in a corresponding reduction in mowing requirements. Soft-leaf buffalo grass cultivars are more shade and wear tolerant than other warm-season turfgrasses being used by homeowners. There are differences between the individual buffalo grass varieties however. The majority of types currently available would be classified as having moderate levels of shade tolerance and wear reasonably well with good recovery rates. The impact of wear in a shaded environment was not tested and there is a need to investigate this as this is a typical growing environment for many homeowners. The use of herbicides is required to maintain quality soft-leaf buffalo grass turf. The development of softer herbicides for other turfgrasses has seen an increase in their popularity. The buffalo grass cultivars currently available have shown varying levels of susceptibility to the chemicals tested. The majority of the cultivars evaluated have demonstrated low levels of phytotoxicity to the herbicides chlorsulfuron (Glean) and fluroxypyr (Starane and Comet). In general, soft leaf buffalo grasses are varied in their makeup and have demonstrated varying levels of tolerance/susceptibility/adaptation to the conditions they are grown under. Consequently, there is a need to choose the cultivar most suited to the environment it is expected to perform in and the management style it will be exposed to. Future work is required to assess how the structure of the different cultivars impacts on their capacity to tolerate wear, varying shade levels, water use and herbicide tolerance. The development of a growth model may provide the solution.

Cynodon dactylon Green Couch Grass, Bermuda Grass 'JT1'

Spontaneous mutation or chance seedling: discovered in the mid-1990s as a superior plant growing in a commercial field of “Common” Cynodon dactylon on Jimboomba Turf Company’s farm at Jimboomba in south-east Queensland. Selection criteria: vigorous lateral spread, high shoot density and turf quality, low inflorescence numbers, and darker green colour. In 1999 after observing the superior turf performance of this mutant plant as a small patch within a much larger paddock of “Common”, vegetative material was taken and propagated in clean ground elsewhere on the farm for multiplication and further trials in a variety of turf situations in south-east Queensland. Propagation: vegetative. Breeder: Lynn Davidson, Jimboomba, QLD. PBR Certificate Number 2640, Application Number 2002/282, granted 24 February 2005.

Cynodon transvaalensis x Cynodon dactylon Hybrid Green Couch Grass, Hybrid Bermuda Grass 'MS-Supreme'

Ploidy: triploid interspecific hybrid (3n = 27 chromosomes). Plant: habit prostrate, creeping, type mat-forming, height very short, longevity perennial, spreading laterally by stolons and rhizomes. Stolon: compound nodes with up to 3 leaves, internode length very short, internode thickness very thin, colour grey-brown (RHS N199A) when exposed to sunlight. Culms: length very short. Leaf blade: shape linear-triangular, length short, width narrow, colour dark green (RHS 137B). Ligule: dense row of short white hairs. Inflorescence: digitate with 3(-4) very short spicate racemes, peduncle very short. (All RHS colour chart numbers refer to 2001 edition.) PBR Certificate Number 2641, Application Number 2002/305, granted 24 February 2005.

Cynodon dactylon, Green Couch Grass 'TL1'

Chance seedling: observed in about 1989 as a distinctly coarser textured, densely matting, darker green mutant bermuda grass plant growing among the hybrid ‘Tifgreen’ on the eighth green at the Townsville Golf Course. Although ‘TL1’ was selected from a sward of the hybrid Bermuda grass ‘Tifgreen’, its inflorescence structure (4, not 3, racemes per inflorescence), agronomic attributes (e.g. its tolerance to certain herbicides), and its DNA profile are consistent with a chance seedling of Cynodon dactylon rather than a mutant plant of hybrid (C. dactylon x transvaalensis) origin. Selection criteria: exceptionally short stolon internodes resulting in an extremely tight knit stolon mat under close (c. 5-6 mm) but not very close (c. 3-4 mm) mowing; very deep, strong rhizome system; very dark green colour; tolerates shade better than other Australian bermuda grass varieties of common knowledge (except for ‘Plateau’A); and remains low growing under heavy tropical cloud cover even after 6-8 months. Designated ‘TL1’ by Tropical Lawns Pty Ltd and trialed successfully during the late 1990s and early 2000s in high wear situations (e.g. golf tees) in north Queensland. Propagation: vegetative. Breeder: Barry McDonagh, Townsville, QLD. PBR Certificate Number 2638, Application Number 2002/267, granted 24 February 2005.

Cynodon dactylon, Green Couch Grass 'Oz-E-Green'

Spontaneous mutation or chance seedling: discovered in 2001 as a superior plant growing among “Common” green couch on the breeder’s turf farm at Berries Road, Childers. A selected piece of sod was removed and broken into vegetative sprigs to propagate a larger area of this variety elsewhere on the breeder’s property. The original plant has now been multiplied vegetatively three times without showing any discernible off types. Selection criteria: dense prostrate habit and limited inflorescence production (giving a low mowing requirement), high turf quality, dark green colour. Propagation: vegetative. Breeder: Robert William Morrow, Childers, QLD. PBR Certificate Number 2844, Application Number 2004/035, granted 22 August 2005.

Cynodon dactylon, Green Couch Grass, Bermuda Grass 'Grand Prix'

‘Grand Prix’ is a selection from a cross between ‘Wintergreen’ and ‘Couch 5’ (also designated C5). ‘Couch 5’ was a selection from an earlier series of crosses by the breeder between ‘Wintergreen’ and a number of Cynodon dactylon accessions, which were collected by the breeder from the Mornington Peninsula area of Victoria between 1986 and 1990. C5 was an experimental breeding line, and was not subsequently reserved as vegetative germplasm. Living material of C5 is no longer in existence. Following the crossing of ‘Couch 5’ and ‘Wintergreen’ in 1998, the resultant seed was germinated on moist blotting paper. Individual seedlings, a total of 150 in number, were planted into 150mm pots and these plants observed during 1998 and 1999. During the summer of 1999-2000, the majority of the seedling plants were culled on the basis of their shoot density, leaf texture, internode length, and colour. In the spring of 2000, the remaining 20 potted seedlings were planted individually into 4m2 plots at the Evergreen Turf farm at Pakenham (Victoria), and allowed to expand fully across these plots. The final selection of Seedling 12 (later designated DN12) in late 2002 was based on shoot density, leaf colour, turf quality, and reduced thatch accumulation as expressed in these plots. Propagation: the original plant has been multiplied through four (4) vegetative expansions prior to PBR application without showing any discernible off types. Breeder: David Nickson, Frankston, VIC. PBR Certificate Number 3133, Application Number 2005/291, granted 12 September 2006.

Cynodon dactylon, Green Couch Grass, Bermuda Grass 'Winter Gem'

‘Winter Gem’ is a selection from a cross between ‘Wintergreen’ and Couch 5 (also designated C5). Couch 5 was a selection from an earlier series of crosses by the breeder between ‘Wintergreen’ and a number of Cynodon dactylon accessions, which were collected by the breeder from the Mornington Peninsula area of Victoria between 1986 and 1990. C5 was an experimental breeding line, and was not subsequently reserved as vegetative germplasm. Living material of C5 is no longer in existence. Following the crossing of Couch 5 and ‘Wintergreen’ in 1998, the resultant seed was germinated on moist blotting paper. Individual seedlings, a total of 150 in number, were planted into 150mm pots and these plants observed during 1998 and 1999. During the summer of 1999-2000, the majority of the seedling plants were culled on the basis of their shoot density, leaf texture, internode length, and colour. In the spring of 2000, the remaining 20 potted seedlings were planted individually into 4m2 plots at the Evergreen Turf farm at Pakenham (Victoria), and allowed to expand fully across these plots. The final selection of Seedling 9 (later designated DN9) in late 2002 was based on shoot density, leaf texture, and retention of winter colour as expressed in these plots. Propagation: The original plant had been multiplied through four (4) vegetative expansions prior to PBR application without showing any discernible off types. Breeder: David Nickson, Frankston, VIC. PBR Certificate Number 3132, Application Number 2005/290, granted 11 September 2006.

Cynodon transvaalensis x Cynodon dactylon, Hybrid Green Couch Grass, Hybrid Bermuda Grass 'AGRD'

‘AGRD’ was selected by the breeder, Dr Warren Hunt, from a variant area of winter active turf (probably ‘Tifway’ or ‘Tifgreen’) on a Hong Kong Golf Course in Apr 1996. A selection of this material was imported through vegetative quarantine to New Zealand for evaluation. Following a favourable assessment of its potential as a warm-season turfgrass variety under New Zealand conditions made based on its superior comparative performance relative to other Cynodon accessions in glasshouse and field trials, the New Zealand registered variety ‘Grasslands AgRiDark’ was released in 1999. PBR Certificate Number 3716, Application Number 2004/299, granted 20 January 2009.