bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of nutrition on the effectiveness of mimosine for defleecing sheep
Authors: Reis PJ , Tunks DA
Published: November 2004

The effectiveness of mimosine as a chemical defleecing agent was assessed in adult sheep that were subjected to a variety of nutritional treatments prior to administration of mimosine, and in lambs receiving relatively high feed intakes. Mimosine was given as a continuous intravenous infusion over a period of 2 days. Sheep receiving 600 g of a roughage-based diet per day were consistently defleeced following an infusion of mimosine at the rate of 80 mg/kg/day (designated the standard infusion). The prior feeding of a reduced intake of this diet (300 g/day) did not alter the amount of mimosine required to defleece sheep. Likewise, the prior abomasal infusion of an imbalanced mixture of amino acids, which depressed the wool growth rate, did not allow defleecing with a reduced amount of mimosine. A 4-day fast, commenced 3 days before the start of mimosine infusion, approximately halved the amount of mimosine required to defleece sheep. The provision of a high intake of energy, together with large amounts of amino acids available for absorption from the small intestines (supplied by casein), for at least 1 week prior to mimosine infusion, completely prevented defleecing with the standard infusion of mimosine. The effects of these nutritional treatments could be obviated by a 4-day fast as described above. Also, increasing the rate of infusion of mimosine to 120 mg/kg/day largely overcame the effects of previous high nutrition. Relatively greater amounts of mimosine were required to defleece lambs than adults. The concentration of mimosine in plasma was related to the rate of infusion of mimosine. However, fasting and a low dietary intake tended to enhance the concentration of mimosine in plasma for a given rate of infusion. Infusion of mimosine at the standard rate resulted in plasma mimosine concentrations of the order of 100 µmoles/l, but this concentration did not ensure that defleecing would be possible.
Responses of a standard Australian and a Mexican wheat to temperature and water stress
Authors: Davidson JL , Birch JW
Published: November 2004

Single plants of Gabo, an Australian spring wheat, and Pitic 62, a Mexican semi-dwarf one, were grown at 20°C in a growth cabinet until anthesis. They were then transferred to glasshouses at 18/13, 21/16 and 24/19°C day/night temperatures and supplied with 20, 60 and 100% of their ad lib. water requirements. In terms of water use, dry matter production and grain yield, patterns of response to temperature and water stress were very similar for the two varieties. Highest yields were obtained at 21/16°C. Efficiencies of water use increased as water supply decreased; they were lower at 18/13°C than at higher temperatures. The amounts of dry matter produced after the treatments were imposed were taken as biological indexes of the nine environments. Over the entire range of those values, the grain yields of Pitic 62 were consistently higher than those of Gabo. Significant features of Pitic 62 that contributed to its higher yields were that: (1) by anthesis it had produced larger ears from a given weight of supporting shoot tissues; (2) after anthesis it mobilized a higher percentage and amount of stem and leaf material that apparently contributed to grain production. Two broad categories of shoots were distinguished. The first four shoots of both varieties were very tolerant of water stress, producing 50% of their potential grain yield on 20% of ad lib. water supplies. These shoots experienced water stress only after anthesis. Younger shoots experienced the stress treatments from an earlier stage of development; they were very sensitive to water stress and their grain yields were related linearly to water supply. Harvest index values varied with the category of shoot selected and with size of shoot or plant. Implications of relationships between grain weight and shoot weight for crop selection are discussed.
Some characteristics of the germination of Queensland blue grass on cracking black earths
Authors: Watt LA
Published: November 2004

An intermediate stationary stage in the germination of Queensland blue grass (Dicanthium sericeum L.) caused by limiting water availability was examined. It was found that partially germinated seed can maintain viability over extended periods of desiccation and that large numbers of these partially germinated seeds are found under simulated and actual field conditions. Results indicate that this phenomenon is an adaptive mechanism which assists establishment on black cracking earths in which rapid drying of surface layers is characteristic.
The influence of shading on seed yield in subterranean clover
Authors: Collins WJ , Rossiter RC , Ramas MA
Published: November 2004

Swards of three strains of subterranean clover (Woogenellup, Clare and Seaton Park) were subjected to three shading treatments (30%, 55% and 100% of daylight) from the beginning of flowering onwards. For the 100% daylight (unshaded) treatment the incoming daily solar radiation averaged between 20 and 30 MJ/m2. In the unshaded treatment, seed yields for the three strains ranged from about 120 to almost 200 g/m2. These yields were invariably decreased by shading. Moreover the evidence indicated a curvilinear relationship between seed yield and light supply such that at 50% of daylight there was a reduction of rather more than 50% in seed yield. Shading mainly affected the number of inflorescences produced per unit area, although other components of seed yield were also affected adversely. Even late shading (towards the end of flowering) led to lower seed yield, partly associated with lower inflorescence numbers and partly with lower seed numbers per burr. The results are considered to have significance for clover regeneration in mixed clover/grass pastures and also in the cloveritree associations of agro-forestry.
Watermelon mosaic virus 1 and 2 in Queensland cucurbit crops
Authors: Greber RS
Published: November 2004

Watermelon mosaic virus type 1 (WMV-1) has not previously been reported from Australia and has become prevalent in Queensland only since 1970. Watermelon mosaic virus type 2 (WMV-2) continues to reach a high incidence in marrow (Cucurbita pepo) and pumpkin (Cucurbita maxima and Cucurbita moschata) crops, WMV-2 is rarely isolated from watermelons (Citrullus vulgaris) in which epidemics of WMV-1 now cause serious reductions in yield. The Queensland Blue cultivar of C. maxima, the most important cucurbit crop, produces severely distorted fruit following infection by WMV-1, although it is little affected by WMV-2. Physical properties of these WMV isolates and electron microscopic examination of the virus particles and associated cellular inclusions showed them to be similar to those reported elsewhere, but there were some distinctive host reactions for the WMV-2 isolates. No resistance to either WMV-1 or WMV-2 was found in commercially available C. pepo, C. maxima or C. vulgaris. The resistance of Cucumis metuliferus to Australian WMV-1 isolates was confirmed, and a source of resistance to both WMV-1 and WMV-2 was found in Lagenaria siceravia. Methods of separation of WMV-1 and WMV-2 from mixed isolates and methods for the identification of each on differential hosts and by serology were shown to be effective.
The development of ruminant digestion in the calf. II.* The digestion of barley and urea
Authors: Leibholz J
Published: November 2004

Two Friesian calves were fitted with re-entrant cannulae in the duodenum and four Friesian calves were fitted with re-entrant cannulae in the duodenum and terminal ileum within 1 week of birth. At 35 days of age the calves were weaned from milk and offered a diet containing 72% barley, 3.5% urea and 15 % wheat chaff. Total collections of digesta flowing from the duodenum and ileum were made for 12 hr at weekly intervals for 6 weeks after weaning. Of the dry matter ingested, 26% was apparently digested in the stomach 1 week after weaning, 40% by 2 weeks after weaning and increasing to 51% by 6 weeks after weaning. The flow of nitrogen to the duodenum was greater than the nitrogen intake in the first week after weaning, and it gradually decreased to 83% of the nitrogen intake by 6 weeks after weaning. During this period the contribution of microbial nitrogen to the nitrogen flow increased from 28 to 71%. The apparent absorption of amino acids from the small intestine increased with increasing feed intake, but the uptake of methionine was less than the methionine requirement for growth.

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* Part I, Aust. J. Agric. Res., 26: 1081 (1975).
Performance of Hereford and crossbred Hereford cattle in the subtropics of New South Wales: growth of first-cross calves to weaning
Authors: Barlow R , O'Neill GH
Published: November 2004

Thirty-one Simmental (S), 33 Friesian (F), 27 Brahman (B) and 30 Hereford (H) sires were mated to Hereford (H) females over 3 years at Grafton to evaluate the performance of first-cross calves in the subtropics of New South Wales. An average of four calves was produced by each sire. Gestation lengths of B x H and S x H calves were 8 and 3 days longer and those of F x H calves were 2 days shorter than in H x H calves. There was a significant genotype x sex interaction for birth weight. Among male calves B x H were heaviest at birth, while S x H were heavier than H x H. There were no significant differences between genotypes among female calves. When adjusted to a constant gestation length B x H males were still heavier at birth. Crossbred calves grew faster to weaning than Hereford calves. Advantages in liveweight at weaning were 12.4 kg (B x H), 15.1 kg (S x H) and 16.3 kg (F x H), when a common conception day was assumed. Crossbred calves had greater body dimensions at birth, and generally had greater increases in body dimensions between birth and weaning. Differences in body dimensions were not entirely accounted for by differences in weight. Brahman x H calves had approximately twice as much eyelid pigmentation as calves of other genotypes. Male calves had 1.4 days longer gestation length, 2.2 kg heavier birth weight (genotype x sex interaction significant), and 60 g day-1 faster growth rate to weaning than females.
Genetic control of the pre-anthesis development of spring rape (Brassica napus L.). II.* Identification of individual genes controlling developmental pattern
Authors: Thurling N , Das VLD , Vijendra Das LD
Published: November 2004

Controlled environment studies of variation in the duration of the vegetative phase of spring rape were conducted with the objective of detecting major genes determining vernalization response. These studies involved analyses of variation within early generation segregating populations and between inbred-backcross lines. Distributions of unvernalized F2 plants from crosses between Target, Bronowski, and Isuzu were clearly bimodal when grown under continuous light at 25°C. Duplicate recessive genes were found to determine the vernalization requirement of Bronowski. In Isuzu, however, the vernalization requirement was determined by two independent genes, one having a markedly greater effect than the other on vernalization response. The genes in Bronowski occurred at different loci from those in Isuzu, and Target, which had no vernalization requirement, possessed the dominant alleles of all four genes. Plants having a significantly shorter vegetative phase than Target were also detected in F2 and backcross populations of crosses between Target and the other two cultivars. Analyses of the distribution of inbred-backcross lines showed that this character was determined by genes from Isuzu and Bronowski which were not expressed when associated with the parental genotype.

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*Part I, Aust. J. Agric. Res., 30: 251 (1979).
Apex, lamina and shoot removal effects on seed production and growth of Stylosanthes hamata cv. Verano
Authors: Wilaipon B , Gigir SA , Humphreys LR
Published: November 2004

Swards of Stylosanthes hamata cv. Verano were simulated by growing plants in irrigated square pots placed edge to edge and discarding border rows. The effects on the events leading to seed formation of removing (1) all shoot apices, (2) apices plus 60% of laminae and (3) shoots supporting 60% of laminae were studied, when these treatments were applied at (1) a vegetative stage, (2) early floral initiation and (3) advanced floral initiation. Defoliation delayed flowering and reduced growth rates for 10–30 days subsequently, these effects increasing if bud sites were removed in addition to lamina and apices. In this heated glasshouse the final seed yield and most of the seed yield components were similar in all treatments, including undefoliated swards. Seed yield increased from 141 to 171 g m-2 when 60% of laminae only were removed at an early seed-setting stage in well-grown swards (LAI 6.9). In a subsequent experiment, removal of 33% of laminae at a similar advanced developmental stage increased seed yield from 106 to 180 g m-2, and other late defoliation treatments did not significantly influence seed yield. These effects are discussed in terms of altered patterns of apical dominance and leaf differentiation, bud site removal, assimilate supply to the inflorescences, and the consequences of delayed flowering.
Hepatic enzyme specific activities and fasting metabolic rate in pullets fed on controlled amounts of food during growth and lay
Authors: Balnave D , Farrell DJ , Cumming RB , Wolfenden J
Published: November 2004

Variations in growth rate and daily egg output during lay were obtained by feeding controlled amounts of food to egg-type pullets from 6 to 70 weeks of age. Prior to sexual maturity the weight and lipid content of the liver were significantly increased when growth rate was severely restricted. These changes were associated with increases in the specific activities of hepatic lipogenic enzymes. Changes in hepatic enzyme specific activities in response to restricted feeding during growth were small compared with the increases observed at sexual maturity. During lay, restricted feeding had no significant effect on the liver lipid content or hepatic enzyme specific activities, but the specific activities of all the hepatic enzymes examined declined with age after sexual maturity. Restricted feeding had no influence on the fasting metabolic rate at any age. A reduction was observed between 13 and 20 weeks of age, but after a small increase at sexual maturity little further change was noted.
Utilization of lupin stubbles by merino sheep: studies of animal performance, rates and time of stocking, lupinosis, liver copper and zinc, and circulating plasma enzymes
Authors: Croker KP , Allen JG , Petterson DS , Masters HG , Frayne RF
Published: November 2004

Three experiments were conducted in the West Midland region of Western Australia to evaluate the sheep-carrying capacity of dry narrow-leafed sweet lupin (Lupinus angustifolius cv. Uniharvest) stubbles. In addition, the effect of stocking rate on lupinosis, and the effect of lupinosis on circulating plasma enzymes and liver copper and zinc levels were determined. At low stocking rates (25 or less ha-1) sheep were grazed for up to 80 days with increases in liveweight. However, with higher stocking rates (50 or 75 ha-1) the maximum weights obtained were lower, and reached after a shorter period of time. Sheep grazed at the high stocking rates suffered more liver damage than those grazed at low rates, and it is suggested that outbreaks of clinical lupinosis might be precipitated by grazing sheep at high rates. Sheep that grazed the stubbles and suffered liver damage had higher liver copper levels than those that suffered no damage. Also, there was an indication that the degree of liver damage and the liver copper level were directly related. It is suggested that the toxins of Phomopsis leptostromiformis cause the liver to take up and store copper. A significant negative correlation between the degree of liver damage and the liver zinc level was found. However, it was not determined whether this diminishment of liver zinc was a direct effect of the toxins of P. leptostromiformis or due to displacement by copper which was actively being taken up. Plasma levels of ornithine carbamyl transferase, alkaline phosphatase and aspartate amino transferase, measured during or at the end of the experiments, were not related to the degree of terminal liver injury. They are not considered reliable indicators of the incidence or severity of lupinosis in the field.
Glutathione peroxidase and selenium in sheep. I. Effect of intraruminal selenium pellets on tissue glutathione peroxidase activities
Authors: Paynter DI
Published: November 2004

Two groups of sheep, both on a diet deficient in selenium, were either treated with intraruminal selenium pellets (containing 5% elemental selenium, 95% iron) or remained as untreated controls. At 23 weeks after pellet administration, activities of the selenium-containing enzyme glutathione peroxidase were greatly increased in many of the tissues of treated animals compared with the untreated controls. Maximum activity of erythrocyte glutathione peroxidase was reached 20 weeks after pellet administration. The maximum activity was considerably greater than the activity at which selenium-responsive diseases, in particular selenium-responsive unthriftiness, occur. This, together with the greatly increased enzyme activities in other tissues several months after pellet administration, suggests that selenium status can be adequately maintained for long periods by treatment with these pellets. In contrast to monogastric species, it appears that in the ruminant the biological availability of elemental selenium released from pellets, as determined by tissue glutathione peroxidase activities, is similar to that reported previously for selenite.
Dry matter accumulation and water use relationships in wheat crops
Authors: Doyle AD , Fischer RA
Published: November 2004

In order to better understand crop growth (dry matter accumulation, DM), crop evapotranspiration (Et), and their interrelationships, we studied dryland crops of wheat (Triticum aestivum L. cv. Timgalen) sown at various dates and seeding densities in each of three years at Tamworth, N.S.W. Soil water stress was minimal before anthesis in each year, but in two years substantial stress arose before maturity. DM was increased consistently by increased plant density, and decreased at anthesis and maturity by later sowing. Crop growth rates determined over 2-week intervals around anthesis ranged from 3 to 20 g m-2 d-1, representing a range in efficiency of utilization of intercepted total solar radiation of 0.48 to 2.35%, variation which was adequately explained (R2 = 0.80) by ontogeny (days from anthesis) and Et / Ep ratio (Ep = class A pan evaporation). Et at anthesis, but not at maturity, was increased slightly by higher seedmg density; crop Et was not consistently affected by sowing date. Et / Ep over 2-week periods around anthesis was related to leaf area index, and to a lesser extent to available soil water and Ep (R2 = 0.58). For the period from the first sowing date in June or July until the middle of October, the relationship of total Et to DM production was linear and close each year, but the slope varied from 6.2 g m-2 mm-1 (cold dry year) to 14.0 g m-2 mm-1 (wet year). This variation could be attributed to annual variation in the soil evaporation component of Et, and in the ratio of DM to crop transpiration (= transpiration efficiency, TE). For 2-week periods around anthesis, TE ranged from 2.9 to 5.4 g m-2 mm-1 and was inversely related to Ep (R2 = 0.56). Provided soil evaporation can be allowed for, since it ranged from 18 to 41% of crop Et from sowing to maturity, it is argued that the crop transpirationtranspiration efficiency approach is particularly useful for analysing the growth and water use of dryland wheat.
Drought resistance in spring wheat cultivars. III.* Yield associations with morpho-physiological traits
Authors: Fischer RA , Wood JT
Published: November 2004

This paper describes associations between yield performance under drought and morpho-physiological traits, determined both under drought and non-drought conditions, for a large set of diverse cultivars of bread wheat (Triticum aestivum L.), durum wheat (T. turgidum L.), triticale (X Tritosecale Wittmack) and barley (Hordeum vulgare L). Performance under drought was considered in terms of grain yield and drought susceptibility, the latter being proportional to the decrease in yield relative to yield without drought. Species effects are considered, but greatest attention is paid to associations amongst bread wheat cultivars (n = 34), based on phenotypic and genotypic correlations, multiple linear regression and principal components analysis. Under drought, which reduced yield on average 60%, greater yield was most closely associated with greater total dry weight at maturity. Variation in traits associated with plant water relations had only a minor influence. The best prediction of yield under drought, from traits measured in the absence of drought (non-drought traits), was given by a linear model containing total dry weight, kernel weight and leaf waxiness, all with positive coefficients. Drought susceptibility, as defined, was unrelated to plant water relations under drought, but was related to various non-drought traits. It increased with increased non-drought yield, harvest index, kernels per sq metre, kernels per spike and leaf water potential, and with decreased plant height and waxiness. One part of these associations with drought susceptibility appeared to be related to variation in height, probably arising from the action of the Norin 10 dwarfing genes; part, however, was independent of height. The relationships suggested that direct selection for increased yield in the absence of drought, or selection via most of the non-drought traits, increased drought susceptibility and, depending on drought level, may increase or decrease yield under drought. No trait had clearly desirable effects on yield both in the absence of drought and drought susceptibility; total dry weight appeared to have the least undesirable effect on susceptibility.

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*Part 11, Aust. J. Agric. Res. 30: 801 (1979).
A comparison of 182 sultana clones selected for yield
Authors: Antcliff AJ , Woodham RC , Cellier KM
Published: November 2004

A comparison of 182 Sultana clones selected for yield showed that selection based on 9 or more years' yields on source vines was more effective than that based on 4 years. The main effect of the longer-term selection was the avoidance of leafroll-infected vines, but there may also have been a small genetic component. The leafroll, which appeared to be a mild strain, was associated with a reduction in yield of about 15%, a small increase in weight of berry, fewer bunches per vine with fewer berries per bunch, and a slight decrease in sugar concentration in the berries when adjustment was made for the effect of yield. No clones superior to those already in use were found.
Reaction of Trifolium subterraneum genotypes to different isolates of Kabatiella caulivora
Authors: Beale PE , Thurling N
Published: November 2004

Single spore isolates of Kabatiella caulivora were derived from infected plant material collected at a number of locations over a wide area in the south-western coastal region of Western Australia. An experiment was conducted to compare the reactions of three resistant Trifolium subterraneum genotypes to infection at the cotyledon stage by 18 isolates. Significant differences in severity of damage to the unifoliate leaf were observed between host genotypes and isolates. The host x isolate interactions were, however, not significant. In a second experiment the reactions of two resistant and two susceptible genotypes to five isolates were compared. Significant host-genotype differences were observed in both cotyledon and unifoliate leaf damage. Isolate differences were only significant in the case of cotyledon damage. Again, no significant host x isolate interaction. was detected. Procedural problems associated with the preparation of conidial suspensions of single spore isolates of Kabatiella caulivora are discussed with particular reference to accurate measurement of disease reaction.
The effect of compensatory growth on lipogenesis in ovine carcass adipose tissue
Authors: Hood RL , Thornton RF
Published: November 2004

Rates of lipogenesis, as measured by the incorporation in vitvo of [14C]acetate into fatty acids, were measured in wethers which were either fed continuously or subjected to an interval of starvation. Refeeding ad libitum of starved sheep resulted in a faster growth rate; immature sheep after 110 days and mature sheep after 56 days had reached a fat content similar to that in the continuously grown sheep. In continuously grown sheep the rate of lipogenesis in subcutaneous adipose tissue increased with increasing liveweight. Lipogenesis was almost totally eliminated after a period of weight loss. In nutritionally rehabilitated immature and mature sheep, lipogenesis was restored and reached a rate higher than that measured for sheep which were continuously grown on the same diet. In immature sheep lipogenesis responded rapidly to refeeding. However, lipogenesis in mature sheep was slower to respond to increased dietary intake, which indicated that in mature sheep the biochemical pathways of lipid metabolism take several days to respond and reach their full lipogenic potential in response to changes in the physiological state.
Effect of vitamin B12b injections on the growth of young Merino sheep
Authors: Hannam RJ , Judson GJ , Reuter DJ , McLaren LD , McFarlane JD
Published: November 2004

In two experiments near Robe in the south-east of South Australia, on soil highly prone to the occurrence of cobalt deficiency in sheep, the effect of injections of vitamin B12b (hydroxocobalamin) on grossly cobalt-deficient weaner sheep and suckling lambs was compared with the effect of oral doses of cobalt as liquid drenches or ruminal pellets. All the supplements used were effective in treating cobalt-deficient weaned sheep or preventing the onset of cobalt deficiency in lambs. A single injection of vitamin B12b (1 mg), under the conditions of these experiments, satisfied the requirements of lambs for 14 weeks and cobalt-deficient weaner sheep for up to 40 weeks. The use of vitamin B12b in preventing or correcting cobalt deficiency in sheep in the field is discussed. Serum vitamin B12b concentration was not a reliable indicator of the vitamin B12b status of young sheep which had been given single injections of vitamin B12b. Vitamin B12b, deficiency in sheep was associated withdecreased concentrations of blood haemoglobin and of glucose, total proteins, urea and cholesterol in blood serum. The activities of serum aspartate transminase and alkaline phosphatase did not appear to be affected by the vitamin B12b status of the sheep.
Seasonal variations of nitrogen and digestible energy intake of cattle on tropical pasture
Authors: Romero A , Siebert BD
Published: November 2004

Organic matter intake of cattle grazing tropical pastures was measured during periods of, firstly, new grass growth in the wet season, secondly, regrowth of grass pasture following rain, and thirdly, mature growth consisting of chiefly either grass or legume. The measurements were made by reference to digesta markers on fistulated cattle carrying portable equipment. The intake values of digestible energy were considered in relation to digestibility values obtained from diet samples from oesophageally fistulated cattle grazing grass and legume pastures over a 5-month period, and also to changes in liveweight of a group of unfistulated cattle grazing the same pastures. The measured values of digestible energy intake during new pasture growth, regrowth and during the dry season were in accord with the weight changes. The relationship between digestibility and liveweight change suggested that the primary limitation to the growth of cattle on tropical pastures is one of digestibility. Although supplementary nitrogen is known to increase feed intake in deficient situations, it would seem that substantial improvement of dry season nutrition can only be achieved by using forage that is more digestible than the native vegetation. Some legume introductions appear to do this.
Scrotal thermoregulation of the bull (Bos sp.)
Authors: Robertshaw D , Vercoe JE
Published: November 2004

A comparison was made of evaporative heat loss from the skin of the scrotum and the thorax of the bull. The sweat glands of the scrotum were not controlled independently of those on the general body surface. Scrotal sweat glands were found to be under adrenergic neural control like those of the general body surface. The large sweat glands of the scrotum produced approximately five times as much sweat per gland as those on the general body surface. Localized heating of the scrotum for 20 min stimulated both panting and sweating without any change in deep body temperature. Insensible moisture loss from the scrotum was greater than that from the skin of the general body surface. It is concluded that there are no fundamental differences in the properties of the sweat glands of the scrotum and those of the general body surface, and that the high insensible moisture loss of the scrotum assists with cooling of the skin of the scrotum. It is suggested that a function of the tunica dartos muscle is to reduce insensible moisture loss.
The distribution and importance of annual ryegrass toxicity in Western Australia and its occurrence in relation to cropping rotations and cultural practices
Authors: Stynes BA , Wise JL
Published: November 2004

Surveys in Western Australia showed annual ryegrass toxicity to occur on 152 farms in an area around Gnowangerup measuring c. 100 km by 150 km and on 18 farms in four other isolated areas. The disease has spread rapidly during the last 10 years, and has been favoured by practices aimed at pasture improvement in alternating crop-pasture rotations. In the last four seasons, between 76 and 95 % of all stock mortalities due to ryegrass toxicity occurred on fields grazed in the season following a cropping year. Under these conditions, ryegrass is dominant in the pasture, and infection levels are highest. Burning these fields in autumn reduces the level of infection and makes the pasture relatively safe to graze in this season.
The influence of the lucerne bud mite (Eriophyes medicaginis Keifer) on the growth of annual and perennial Trifolium species
Authors: Ridland PM , Halloran GM
Published: November 2004

Eriophyes medicaginis Keifer was found to cause significant reduction in the growth of seedlings of the annual Trifolium species T. incavnatum and T. subterraneum, but had no influence on the growth of the perennial species T. fragiferum, T. pratense and T. repens. The mite did not reproduce on either annual or perennial Trifolium species. Leaf symptoms on the annual species were similar to those caused by bean yellow mosaic virus on annual clovers. The symptoms on T. incavnatum did not become evident until 10-12 days after infestation, which was the time taken for undifferentiated leaves to fully develop. This indicates that the presumed salivary toxin of the mite is of short-lived activity in the plant or is not readily translocated beyond the leaf upon which feeding takes place, or both.
Transport and distribution of manganese in two cultivars of soybean (Glycine max (L.) Merr.)
Authors: Heenan DP , Campbell LC
Published: November 2004

Transport and distribution patterns of manganese were studied in soybeans (cultivars Lee and Bragg) grown over a wide range of manganese supply levels in solution culture. Increasing the manganese supply from 1.8 �M to 450 .�M produced symptoms of manganese toxicity and reduced growth in both cultivars. Symptoms and dry matter yield reductions were more severe in Bragg. Manganese taken up by the plant was preferentially transported to young expanding tissue, while the amount moving to older tissue, including cotyledons, increased with availability. At high manganese supply the leaves accumulated higher concentrations with age, resulting in a decreasing concentration gradient between old and young leaves. There was no difference between Lee and Bragg in the distribution of manganese to plant parts or in the concentration of manganese in actively growing tissue. Manganese deficiency symptoms developed on both cultivars grown under limiting supply conditions. Partial mobility of the element was indicated: small amounts were translocated from the old leaves when young expanding leaves were manganese deficient. Nevertheless, considerable amounts remained in the cotyledons, and manganese appeared to have a low mobility when the plant's supply was limited.
Effects of birth weight and energy gain preweaning on survival of lambs weaned at 21 days
Authors: Walker DM , Hunt SG
Published: November 2004

Lambs were fed on cows' milk from birth to 21 days and then weaned abruptly on to a pelleted food that had been available to them from 10 days of age. In experiment 1 six lambs were given only sufficient milk to maintain weight for 21 days (0.48 MJ gross energy/day per kg0 73). No lambs survived beyond a few days after weaning at 21 days. In experiment 2 20 lambs were offered milk to provide 1.44 MJ gross energy/day per kg0.73 for 21 days. After weaning, only five lambs survived for more than 4 weeks. Liveweight at weaning was the most important single factor determining the chances of survival after weaning. All lambs that weighed less than 5.2 kg at 21 days died. The energy gain between birth and 21 days was the main factor determining the length of time that lambs survived without food after weaning. It was estimated that all lambs which weighed more than 1.4 kg at birth and gained > 23 MJ in 21 days could survive for 15 days after weaning without eating.
Measurement in sheep of the quantity and composition of rumen digesta and of the fractional outflow rates of digesta constituents
Authors: Faichney GJ
Published: November 2004

Knowledge of the fractional outflow rates of rumen digesta constituents is required for the quantitative prediction of rumen function. However, there are few data available for these parameters because of the problems associated with specific labelling of digesta constituents and with the need to ensure that samples are truly representative of rumen digesta. Methods are described here by which two markers can be used together to overcome the problem of representative sampling of the rumen, so eliminating the need for specific labelling, with 'ideal' markers, of digesta constituents. Thus, from the measurement of the amount and composition of true digesta in the rumen and the amount and composition of true digesta flowing from the abomasum, values for the fractional outflow rates (and its reciprocal, mean retention time) of rumen digesta constituents can be calculated. Appropriate application of these methods will allow the derivation of functions to predict fractional outflow rates. The results presented show that the fractional outflow rate of an adsorbable marker, 103Ru-P, was about half that of water but was about twice that of particulate matter; it was also greater than the net value for microbes. On the assumption that microbial material leaving the rumen is drawn from a free-floating microbial population and a population associated with particulate matter, it was calculated that 0.29 � SE 0.07 (range 0.09-0.49) of the rumen microbial population could have been free-floating.
A comparison of breeds and their crosses for beef production. I. Birth and weaning traits
Authors: Morgan JHL , Saul GR
Published: November 2004

Hereford and Friesian cows aged 12-15 months in 1970, were inseminated with semen from Hereford, Friesian, Charolais and Brahman bulls each year from 1970 to 1973 to produce a total of 736 calves. All cows and calves were grazed together, and the total of 650 surviving calves weaned at c. 8 months of age. Cow age and year of calving were confounded. Hereford cows had longer gestations, smaller calves, more calving difficulty and greater calf mortality than Friesian cows. Hereford cows provided their calves with less than half as much milk as did Friesian cows; the weaning weight advantage of calves from Friesian cows varied from 48 % in 2-year-old cows to 22-24 % in 3-, 4- and 5-year-old cows. Relative to Hereford sires, the use of Charolais and Brahman sires on Hereford and Friesian cows resulted in increases in gestation length, birth weight, calf mortality and calving difficulty; the use of Friesian sires tended to increase calving difficulty, but did not increase gestation length, birth weight or calf mortality. In Hereford cows, the use of Charolais and Friesian sires, as compared with Hereford sires, increased weaning weight by 8 % on average over the 4 years (the increase was zero in 2- and 3-year-old cows and 11-18 % in 4- and 5-year-old cows); the use of Brahman sires did not increase weaning weight. In Friesian cows, the use of Charolais sires, as compared with Hereford sires, increased weaning weight by 5-10% in all years; the use of Friesian sires did not influence weaning weight whilst the use of Brahman sires reduced it by 5%. Heterosis from crossing the Hereford and Friesian breeds increased the weaning weight of the first-cross calves by 3.4%.
Choosing trial sites to maximize selection response for grain yield in spring wheat
Authors: Pederson DG , Rathjen AJ
Published: November 2004

Nine sites used in a wheat breeding programme in South Australia were investigated. Of the six major sites, four occupy farmers' fields and two are located on experiment stations. The data analysed comprised grain yields of 31 genotypes grown in 31 trials over a 5-year period. Relative to that grown at non-station sites, wheat grown at the experiment-station sites generally had higher mean yields, higher coefficients of variation, and lower heritabilities. Data from a set of independently conducted trials were used to estimate the true yields of the 31 genotypes. A heritability of the correlated response to selection was then calculated for each breeding trial, and was generally found to be low for the experiment-station sites. Further investigation showed that the non-station sites are suitable for the selection of genotypes intended for low-yielding environments, and the station sites are better suited for the selection of genotypes intended for high-yielding environments. The optimum selection scheme was found to consist of several unreplicated trials per year, and at least four trials per year are necessary to avoid the possibility of a negative heritability of the correlated response to selection.
The use of urea to improve milk yields and lamb survival of Merinos in a dry tropical environment
Authors: Stephenson RGA , Edwards JC , Hopkins PS
Published: November 2004

Urea supplementation of lambing Merino ewes increased milk yield and lamb growth and survival rates in both pen and paddock studies. These productivity gains occurred in a semi-arid environment characterized by poor reproductive efficiency in Merinos. In pens, urea supplenlents fed to lactating ewes at the rate of c. 12 g/day stimulated intake of poor quality pasture hay (0.9 %nitrogen) by c. 30% and increased total nitrogen intake by c. 100%. Milk yield was improved by c. 50% and lamb growth rate by c. 140%. Sorghum grain supplements stimulated milk yield and lamb growth to a lesser extent than urea. The correlations found in pen studies between nitrogen intake and milk yield of ewes (r � 0.85; P < 0.05), and between ewe milk yield and lamb growth (r % 0.80; P < 0.01), prompted further investigations under paddock conditions. Ewes grazing dry pastures and supplemented with urea (8-10 glday) via drinking water yielded more milk (11-32%) than unsupplemented counterparts. Similarly, there were improvements in lamb growth (80-100%) and survival (c. 10%) in the supplemented groups.
A comparison of carcass chemical fat content and muscle distribution in Merino and crossbred rams and wethers from birth to 50 kg liveweight
Authors: Wynn PC , Thwaites CJ
Published: November 2004

The chemical fat content of and distribution of 24 individual muscles in the carcasses of 120 ram and wether lambs of Merino and of Dorset Horn x (Border Leicester x Merino) breeding were studied between birth and 50 kg liveweight. Rams contained significantly less chemical fat than wethers (P < 0.01), this difference becoming more marked as slaughter weight increased. Crossbreds yielded significantly higher chemical fat than Merinos (P < 0.05) only at 50 kg liveweight. Nine of the 24 muscles studied showed significant differences in relative growth between genotypes and sexes, and in each case the muscles concerned were located in the pelvic and thoracic limbs. Changes in muscle-growth coefficients with increasing slaughter weight occurred mainly below 30 kg, and four of the 24 muscles studied significantly changed their growth pattern more than once and are classified as 'multiphasic'. We conclude that the genotypes and sexes studied do not differ in muscle distribution in an economically important way, but that they do show major variations in fat content and maturity type which fit them for different patterns of production.
The metabolism of phosphorus and calcium in sheep during intravenous infusion of phosphorus
Authors: Schneider KM , Boston RC , Leaver DD
Published: November 2004

The metabolism of calcium and phosphorus in mature sheep, given firstly a chaff diet and then chaff with an intravenous supplement of 1.5-2.0 g/day of phosphorus, was studied by using tracer techniques and compartmental analysis. Absorption was also studied by deconvolution analysis and a technique relating the excretion of tracer in faeces to that of an insoluble marker. Under the conditions of the experiment most of the additional phosphorus infused intravenously was excreted in the faeces, and this was due to a concurrent increase in the endogenous secretion and a decrease in the efficiency of absorption of phosphorus. In sheep given 2.0 g of phosphorus per day, the phosphorus concentration in plasma increased 2.5-4 times, but the excretion of phosphorus in the urine remained small (less than 0.3 g/day) compared with the excretion of 2.5 g/day of phosphorus in the faeces. One feature of the experiment was the difference in the behaviour of bone and soft tissue reservoirs between the sheep given 1.5 g/day of phosphorus and those given 2.0 g/day. In the former group accretion and resorption of calcium and phosphorus in bone and soft tissue increased when compared with the control period, whereas in the latter group bone and soft tissue accretion of phosphorus was unchanged and resorption increased slightly. These results are discussed in terms of the hormonal changes that occur following changes in plasma calcium and phosphorus.
Development of yield in two grain-sorghum hybrids. I. Dry weight and carbon-14 studies
Authors: Chamberlin RJ , Wilson GL
Published: November 2004

Growth and development of two grain-sorghum hybrids (De Kalb E57 and Texas 610) were examined under glasshouse conditions by sequential harvesting and the use of I4C. The grain yield per plant of Texas 610 was higher than that of E57, with higher total biological yield and similar harvest indices. The contribution to grain weight at maturity, of carbon assimilated prior to anthesis, was about 10% for each hybrid. The leaves were the main source of this material. After anthesis, dry weight data indicated that temporary storage of assimilates before retranslocation to the grain was of greater importance in Texas 610 than E57. This storage was largely in the leaves (including sheaths), upper internodes, and roots. A high grain-growth rate was maintained for longer by Texas 610 than by E57. Total dry weight production after anthesis in both hybrids was, at all stages examined, more than sufficient to maintain grain growth.
Effects of pre-storage in low oxygen or high carbon dioxide concentrations on delaying the ripening of bananas
Authors: Wills RBH , Pitakserikul S , Scott KJ
Published: November 2004

Exposure of preclimacteric bananas to low oxygen for several days followed by storage in air extended the time required for the fruit to ripen, as measured by the time to peak carbon dioxide and ethylene production, softening, loss of green skin colour, changes in soluble solids, titratable acid and pH. Optimal conditions were < 1 % oxygen for approximately 3 days. The addition of carbon dioxide did not improve the effect of low oxygen. Treatment of the fruit with ethylene (at 10 �l/l) before, during or after exposure to low oxygen reduced the time required for the fruit to ripen.
Preservation of dormancy in freshly harvested wheat grain
Authors: Mares DJ
Published: November 2004

Freshly harvested grain from 14 varieties of wheat was stored in a deep-freezer at 15�C, or alternatively, in an air-conditioned seed room at 12�C for periods of up to 9 months. Freeze-storage preserved the germination rate of hand-threshed grain at the level observed at harvest, provided that the moisture content of the grain had reached 12%. When frozen grain was transferred to 12�C storage, its germination rate improved with time in parallel with changes observed in freshly harvested seed stored at 12�C from the time of harvest, i.e. after-ripening was not adversely affected by the freezing treatment. This technique should enable greater quantities of material to be screened for low germinability at harvest ripeness and for tolerance to pre-harvest sprouting damage. It also allows the provision of a continuous supply of uniform material for investigations of dormancy and grain after-ripening.
The utilization of rice straw fed to Zebu cattle and swamp buffalo as influenced by alkali treatment and Leucaena supplementation
Authors: Moran JB , Satoto KB , Dawson JE
Published: November 2004

Rice straw was fed ad libitum to Indonesian Zebu (Ongole) and swamp buffalo bulls. The straw was fed either untreated or treated with 4% NaOH for 24 h, and with or without a Leucaena (L. leucocephala) supplement. Elephant grass (Pennisetum puvpuveum) was fed as a control diet. Alkali treatment improved digestibility of dietary nutrients and the metabolizability of dietary energy, and was associated with an increase in the movement of water and digesta through the gut. However, it also depressed appetite by 25-30%, and this may have been related to the high pH of both the diet and the rumen following feeding. Intake of the alkali-treated rice straw, when fed with Leucaena, was increased by up to 30%, whereas that of untreated rice straw was depressed by 10-20%. In the Leucaena-supplemented animals, increases were observed in rate of passage of digesta, balances of dietary nutrients (nitrogen, phosphorus and calcium) and levels of rumen metabolites. The animals offered elephant grass had similar intakes to those of animals receiving untreated, unsupplemented rice straw. The Ongoles and buffaloes responded in a similar manner to the various dietary treatments and, apart from differences in water metabolism, urinary urea-nitrogen excretion and rate of passage of digesta, the nutritional physiology of the two animal species was very similar.