bluuebunny/crossref_metadata_2025 huggingface dataset:
Ruminal and post-ruminal protein digestion in sheep fed on subterranean clover harvested at four stages of maturity
Authors: Hume ID , Purser DB
Published: November 2004

Digestion of the protein of subterranean clover harvested at four stages of maturity was studied in Merino wethers fitted with re-entrant duodenal cannulae. The relative proportions of dietary and microbial nitrogen flowing into the duodenum were estimated from the incorporation into microbial protein of sulphur-35 from ruminal infusions of Na235SO4. Sheep given immature clover consumed more digestible organic matter (DOM) and retained more nitrogen per 100 g DOM intake than sheep given wilted and mature clovers. More protein of the immature clover was degraded in the rumen (73%) than of the mature clover (43–53%); post-ruminal digestibility of dietary protein escaping ruminal proteolysis was also higher for the immature clover (67–70% versus 51–53%). The quantities of clover protein (per 100 g DOM intake) digested post-ruminally were therefore similar at all stages of maturity. The yield of microbial protein (mean 19.9 g per 100 g OM digested in the rumen) was also similar on all treatments. However, ruminal digestion of the DOM of the immature clover was more complete (84%) than that of the mature clover (60–71%); consequently, microbial protein production per 100 g DOM intake was greater on the immature clover. Greater nitrogen retention by animals consuming immature clover was associated with a greater DOM intake. Whether the causal factor was the greater supply of microbial protein per 100 g DOM, or whether the causal factor was a greater DOM intake controlled by factors associated with ruminal digestion, is unresolved. It is also apparent that the greater faecal nitrogen losses per 100 g DOM intake on the mature clover compared with the immature clover were attributable entirely to differences in the amounts of dietary nitrogen excreted at different stages of maturity of the clover.
Change with length of feeding period in the oestrogenic response to ovariectomized ewes to ingested coumestans
Authors: Kelly RW , Lindsay DR
Published: November 2004

Three experiments were conducted to test the effect of the period of intake of feed containing coumestans, and the amount of coumestans in the feed, on the production of cervical mucus in ovariectomized ewes. After long periods of feeding of medic cubes, ewes produced much less mucus than after shorter periods of feeding when feed containing 525 ppm coumestrol and 935 ppm 4'-methoxycoumestrol was ingested. When feed containing approximately one-third of these amounts of coumestans was ingested, the production of cervical mucus initially increased, being greater after 4 than 1 day's exposure to the feed. After 8–16 days of feeding on these diets, ewes produced the same amount of mucus as those fed on a non-oestrogenic diet. The decline in the cervical mucus response suggested either that a deactivation mechanism for coumestans develops in the ewe, or that the ewe becomes refractory to coumestans.
Effectiveness of selection for growth rate in Zebu × British crossbred cattle. I. Pre-weaning growth
Authors: Seifert GW
Published: November 2004

From random-bred populations of Africander cross (AX) and Brahman cross (BX), bulls and cows were selected within breeds for high and low weight per day of age (W/A) at c. 2 years of age and mated assortatively. There was a similar and significant response to selection in both breeds in birth weight and pre-weaning W/A as well as in pre-weaning gains. Although the BX animals were heavier and gained more than the AX animals, the differences were not as great or as consistent as the effect of selection. Calf gains were inversely related to cow gains from birth to weaning, but positively correlated to cow weight. During the pre-weaning period high W/A line cows gained significantly more than the low W/A line cows, while AX animals gained more than the BX group. The higher gain of the high W/A line cows and the higher weaning weight of their calves showed that these lines were more efficient than the low lines in terms of production of weaning weight. Very early calf gains from birth in November to January, and W/A in January, appeared to be poor indicators of the genetic potential of the calf and of the permanent environmental effects affecting its growth. In contrast, the period from January to March, during which the most rapid gains were experienced, reflected both the genetic potential and permanent environmental effects. The previous lactational status of the dam only affected birth weight and day of birth significantly and affected the AX calves more than the BX calves. This resulted in a significant interaction between breed and previous lactational status for these two traits.
Comparisons of liveweight gain and changes in carcass composition between buffalo (Bubalus bubalis) and Bos taurus steers
Authors: Johnson ER , Charles DD
Published: November 2004

Comparisons of liveweight gain, carcass tissue weight gain and carcass composition were made between buffalo (Bubalus bubalis) steers and Angus, Friesian and Hereford steers, and among the three Bos taurus breeds following similar periods of lot-feeding. After a high-grain concentrate feeding regime for 182–205 days, mean daily liveweight gains were Herefords, 1.08 kg; Friesians, 0.88 kg; Angus, 0.72 kg; and buffaloes, 0.67 kg. At the commencement of lot-feeding, mean carcass composition was similar among Bos breeds whilst the buffaloes had higher proportions of muscle and bone and a lower proportion of fat. After lot-feeding there were slight changes only in the mean carcass composition of the buffaloes, whereas there were large changes in and among Bos breeds. An analysis of carcass weight gain showed that liveweight gain did not reflect differential tissue growth. The buffaloes, with a liveweight gain of 87 kg, gained 31.7 kg muscle and 9.3 kg fat. Corresponding gains in Bos breeds were Herefords, 141 kg liveweight for 31.3 kg muscle and 62.7 kg fat; Friesians, 108 kg liveweight for 3 2 8 kg muscle and 19.3 kg fat; and Angus, 98 kg liveweight for 12.5 kg muscle and 57.8 kg fat. The respective increases in weight of muscle and fat expressed as percentages of liveweight increase were buffaloes, 36.4 and 10.7; Herefords, 22.2 and 44.5; Friesians, 30.4 and 17.9; and Angus, 12.8 and 59.0. Regression equations for percentages of muscle, bone and fat on chilled carcass weight are given for the three Bos taurus breeds and the buffaloes.
Efficiency of lamb production in relation to the weight of the ewe at mating and during pregnancy
Authors: Curll ML , Davidson JL , Freer M
Published: November 2004

The intake of pasture by nine groups of 40 Border Leicester x Merino ewes was controlled to achieve three levels of liveweight at mating and three levels at the end of the 15th week of pregnancy. Over the last 6 weeks of gestation all groups gained about 7 kg per head, and after lambing the intake of pasture was unrestricted. Ewes that weighed 58 kg at mating produced 152 lambs per 100 ewes compared with a lambing percentage of 107 by ewes that weighed 44 kg. However, when the lambs reached 10 weeks of age there was little difference in their numbers. This was partly because of the higher death rate of young lambs when the liveweight of the ewe fell during mid-pregnancy, and partly because of the loss of single lambs following dystocia in ewes maintained at a high weight throughout pregnancy. The percentage of lambs reaching marketable weight (32 kg) before the end of the pasture season was related directly to the liveweight gain of the ewe during mid-pregnancy, and inversely to the proportion of lambs reared as twins. The weight of lamb marketed per unit weight of food eaten by the ewes over the autumn and winter was much greater from the ewes that increased from 51 to 58 kg during mid-pregnancy than from those that followed the reverse pattern. In general, a fall in ewe weight over this period led to inefficient use of food and a reduction in the weight and soundness of the fleece. These results suggest that in areas that are marginal for prime lamb production because of a short pasture season, it may be better to ensure a rising plane of nutrition throughout pregnancy than to aim for a high weight at mating.
Studies in ovine infertility in agricultural regions in Western Australia: the influence of a supplement of lupins (Lupinus angustifolius cv. Uniwhite) at joining on the reproductive performance of ewes
Authors: Knight TW , Oldham CM , Lindsay DR
Published: November 2004

The dietary supplementation of groups of 200 ewes with lupins (0.23 or 0.45 kg per head per day) just prior to and during joining increased the ovulation rate by 8–25 ovulations per 100 ewes and the number of lambs born increased by 5–23 lambs per 100 ewes joined. The increase in the number of lambs born had two components: (i) an increase in number of ewes lambing and (ii) an increase in the number of twin births. Another study suggested that feeding the lupin supplement during joining gave larger increases in the reproductive performance of the ewes, especially in number of ewes lambing, than feeding the supplement of lupins before joining. The increases in reproductive performance following lupin supplementation were not associated with differences or changes in body weight or with differences in the rate of wool growth. The feeding of a barley + urea + mineral supplement that provided 25% more digestible energy than the lupin supplement and similar nitrogen levels, but with 50% of the nitrogen in the form of urea, resulted in no increase in the reproductive performance of the ewes.
Dietary effects on the flow of nutrients from the abomasum of the preruminant calf
Authors: Leibholz J
Published: November 2004

Six Friesian bull calves were fitted with re-entrant duodenal cannulae within the first week of life. Within 2 days of surgery the calves were allotted to one of four experimental treatments which were either whole milk or a commercial milk substitute offered once or twice daily. At weekly intervals the calves were reallotted to another diet at random, so that each calf was fed for 1 week on each diet. The flow of digesta from the abomasum decreased as the time after feeding increased. It was about 1l in the first hour after feeding and decreased to 100–200 ml per hour by 10 hr after feeding. The flow of digesta was greater and more uniform in calves fed twice daily than in those fed once daily. The pH of the digesta increased to about 6 immediately after feeding, and then decreased to the pre-feeding levels of about 2 within 8 or 13 hr in calves fed twice and once daily respectively. The pH of the digesta of the calves given milk substitute was initially higher and subsequently lower than that of the calves given whole milk. The flow of lactose to the duodenum was high immediately after feeding, and only about 3% of the ingested lactose entered the duodenum over the last half of the collection periods. The flow of lipid and of nitrogen was high immediately after feeding and decreased gradually over the collection period. Of the daily intake of lipid, 10% reached the duodenum between 18 and 24 hr after feeding once daily. Initial flow of lipid and of nitrogen, expressed as a percentage of intake, was greater in calves given the milk substitute than in those given whole milk, but smaller over the latter part of the collection periods. The concentration of free fatty acids in the digesta increased with time after feeding, and was greater for the calves fed once daily than for those fed twice daily. A greater percentage of the lipid (tallow) in the milk substitute was hydrolysed than of the lipid of whole milk. Proteolysis of casein proteins was greater for calves given whole milk than for those given the milk substitute.
Variation in susceptibility of cultivars of Trifolium subterraneum to Kabatiella caulivora and in pathogenicity of isolates of the fungus as shown in germination-inoculation tests
Authors: Helms K
Published: November 2004

Seedlings of six cultivars of Trifolium subterraneum were tested during germination for resistance to Kabatiella caulivora, and gave results comparable with those obtained with seedlings inoculated by spraying at 1–4 weeks after sowing. Advantages of the method were that a large number of seedlings could be screened under uniform conditions with the minimum of time and space. Within the more susceptible group of cultivars, Woogenellup and Bacchus Marsh were usually more susceptible than Yarloop and Mt. Barker; these in turn were more susceptible than Clare, and Clare more susceptible than Daliak. For all cultivars except the highly resistant cultivar, Daliak, there was a correlation between the rate of trifoliolate leaf production and susceptibility to the disease, the most susceptible being those with most leaves expanded at the time of inoculation and with most leaves present at the time of harvest. Physiologic specialization in isolates of the pathogen from different parts of Australia was demonstrated. In general, one isolate from South Australia was more pathogenic than a group of isolates from South Australia, Victoria and Western Australia; these in turn were more pathogenic than one isolate from New South Wales, which was somewhat atypical in culture, and one from Victoria which was markedly atypical in culture.
Perennation and control of Pseudomonas tomato in Victoria
Authors: Chambers SC , Merriman PR
Published: November 2004

Seed of tomato fruit affected by bacterial speck was examined for Pseudomonas tomato. The bacterium was isolated from seed taken directly from fruit, but not from seed extracted by the fermentation process. Acid and fermentation extraction processes appeared to eliminate P. tomato. Pulp containing natural and/or added populations of the bacterium was non-infective at 1 hr and 48 hr after commencement of the acid and fermentation processes respectively. Studies on the perennation of P. tomato showed that the bacterium survived in plant debris either on or 2 cm below the soil surface for the test period of 30 weeks; it also survived on Nylon mesh in soil for 25 weeks. The incidence of bacterial speck in seedlings was reduced significantly (P = 0.01) by cupric hydroxide sprays, two sprays per week being more effective (P = 0.05) than one. No heat-tolerant strain of P. tomato was detected, and thermal death points for isolates from green and ripe fruit were 48 and 49°C respectively.
Rumen microbial protein synthesis and proportions of microbial and non-microbial nitrogen flowing to the intestines of sheep
Authors: Walker DJ , Egan AR , Nader CJ , Ulyatt MJ , Storer GB
Published: November 2004

Microbial protein synthesis in the rumen of mature sheep was measured by a technique dependent upon the incorporation of 35S from radioactive sulphate into microbial sulphur amino acids. In two separate experiments, sheep were fed on four dried forages and three fresh forages. Mean values and standard deviations for microbial protein synthesis per mole of volatile fatty acid produced in the rumen were 16.1 ? 3.4 g and 20.4? 2.3 g for dried and fresh forages respectively. Corresponding values for microbial protein synthesized per 100 g of organic matter digested in the rumen were 15.1 ? 3.6 g and 24.6 ? 4.9 g. Turnover constants for microbial protein were 1.06 ? 0.12 day-1 and 1.42 ? 0.10 day-1 when dried and fresh forages respectively were eaten, and it is suggested that efficiency of microbial protein synthesis was dependent on the rate of digesta flow through the rumen. Of the non-ammonia nitrogen (NAN) reaching the duodenum up to 41, 53 and 68% was non-microbial in origin when perennial ryegrass, Tama ryegrass and white clover respectively were eaten fresh-cut. When either subterranean clover hay, lucerne hay, wheaten hay or a mixture of wheaten hay plus wheat straw was eaten, up to 67, 57, 52 and 57% respectively of NAN at the duodenum was non-microbial in origin. In the latter two cases, the total flow of NAN was relatively low but the apparent digestibility of the non-microbial fraction in the intestines was still appreciable.
Digestion and utilization of 35S-labelled bacteria placed in the caecum of the sheep
Authors: Judson GJ , Abdelsamie R , Bird RB
Published: November 2004

Suspensions of ruminal bacteria made radioactive by growth in the presence of 3% were injected into the caecum of sheep. The sheep were each given a daily ration of 540 g roughage and 235 g concentrates in 12 equal portions at 2-hourly intervals. Faeces and urine were collected, and peripheral blood was sampled at frequent intervals for up to 14 days after the caecal injection of radioactive bacteria. More than 99% of the 35S in the bacterial suspensions was in the organic sulphur fraction. The percentages of administered 35S appearing in faeces and in urine (mean ? SEM) were respectively 69 ? 1 .8 and 21 ? 1.1; the corresponding percentages of this excreted 35S as inorganic sulphur were 16 ? 0.7 and 91 ? 2.3. The apparent digestibility of the 35S -labelled bacteria was 31%, and the adjusted digestibility was about 42%. The appearance of organic 35S in plasma immediately after the caecal injection of radioactive bacteria indicates that some organic 35S was absorbed from the hindgut. Of the 10 ? 2.3% of the injected 35S dose retained by sheep at the end of the sampling period, about 3% was present in the fleece.
Congenital goitre in sheep in southern Tasmania
Authors: Statham M , Bray AC
Published: November 2004

Congenital goitre was first recorded in Tasmanian sheep In 1945. Severe but sporadic outbreaks have since occurred in 1956, 1964 and 1968. The disease seemed to be associated with particular farms and its incidence often differed markedly between ewe flocks on the one farm. A survey indicated that the condition was mainly confined to the Derwent Valley and the northern Midlands. Studies involved a grazing trial near Bothwell, where goitre was endemic, and included supporting animal house tnals and plant growth studies. Soil type was shown to be a major factor in the disease: ewes grazing pasture on a sandy soil produced many more goitrous lambs than ewes grazing pasture on clay soil. Analyses of the two pastures revealed that those on sandy so11 contained less iodine than those on clay soil but neither contained the minimum level necessary to prevent goitre. Observations revealed that outbreaks of the disease followed wet autumns with subsequent lush pasture during pregnancy. This correlation could be explained if pasture grown under moist conditions contained less iodine than pasture grown under moisture stress. However, experiments with the two main pasture species (perennial ryegrass and subterranean clover) showed that plant iodine levels were not affected by the water supply. Two goitrogenic agents, nitrate and thiocyanate, were present in the pastures, but they were not considered to be Important in the aetiology of the disease. Similarly, the drinking water was found to be unimportant, even though the two sources available contained widely different amounts of iodine. Apparently, between-year variation in the incidence of goitre and the effect of soil type can best be explained by a varying iodine intake dependent on soil ingestion which varies with pasture availability. This hypothesis is discussed in the light of the results.
Compensating for site and year effects in estimating the true yield of wheat genotypes
Authors: Pederson DG , Seif E
Published: November 2004

When data are obtained for several cultivars over years and sites, it is possible to calculate three regression coefficients for each cultivar, based on site x cultivar effects, year x cultivar effects, and site x year x cultivar effects respectively. For wheat yield data from western New South Wales there is an approximate equality of these measures of phenotypic stability, and it is inferred that a single environmental factor has a dominant effect both between and within seasons. This result is applied to the estimation of a regression mean for each cultivar, a technique designed to compensate for the biased sampling of environments over one or two seasons. For nine wheat cultivars, it is shown that the regression mean is at least as good an estimator of true yield as the arithmetic mean, and the conditions under which a regression mean is expected to be a better estimator are defined.
Growth of skeleton weed (Chondrilla juncea L.) as affected by growth of subterranean clover (Trifolium subterraneum L.) and infection by Puccinea chondrillina Bubak and Syd
Authors: Groves RH , Williams JD
Published: November 2004

Growth of skeleton weed (Chondrilla juncea, form A) and subterranean clover (Trifolium subterraneum) was studied in a glasshouse experiment in which the species were grown alone or together and the resultant effects of shoot and root competition assessed. The leaf number and weight of plant parts of C. juncea were reduced by competition vith subterranean clover, especially when shoots of the two species were competing. The leaf area of C. juncea was reduced, especially when roots of the two species were growing together. Puccinia chondrillina on C. juncea rosettes reduced leaf number, leaf area, and weight of plant parts. Subterranean clover grown with C. juncea infected with P. chondrillina further reduced the size and weight of the weed. The large reduction in leaf area and root weight of C. juncea (form A) plants in the presence of both subterranean clover and P. chondrillina suggests that growth of this form of C. juncea in Australia will be greatly reduced in pastures containing these species. In the long term, densities of this form may possibly be so lowered that a significant level of control will be reached in a cereal cropping-pasture system.
Chemosterilization of the Queensland fruit fly, Dacus tryoni
Authors: Smart P , Armati P , Pirie C , Gilmour D
Published: November 2004

Of a number of candidate sterilants tested against Dacus tryoni, three mutagens (HMPA, TEPA and TMAC) were effective against both sexes. With HMPA the margin between sterilizing and lethal doses was narrow, but with the others it was wide. Males sterilized by HMPA or TEPA taken by mouth were slightly less effective than untreated males in securing mates. Males sterilized by TMAC applied topically appeared to be hypercompetitive, but this result was probably caused by the sterilant having been spread to the untreated flies with which they were caged. Reserpine produced a slight reduction in both the fecundity and fertility of the females. With repeated application, ketodecenoic acid slightly reduced female fecundity, but two other growth regulators β-ecdysone and the juvenile hormone analogue Altosid, were ineffective.
Plasma urea nitrogen as an indicator of protein quality. I. Factors affecting the concentration of urea in the blood of the preruminant lamb
Authors: Kirk RD , Walker DM
Published: November 2004

Preruminant male crossbred lambs, aged between 2 days and 5 weeks, were given milk replacers of low (0.10 of total energy as protein) or medium (0.28) protein content. Plasma urea nitrogen (PUN) values were unaffected by: the time of blood sampling within 9 hr after feeding; the age of the lamb, between 3 and 33 days; the lamb's intake of the medium protein diet (range, 500–1180 kJ gross energy/day per kg0.73 storage of plasma samples at –15°C for 5 months before analysis; fasting of lambs for 4 days; feeding of lambs on a nitrogen-free diet for 7 days. PUN values were significantly increased by: an increase in the dietary protein concentration; a reduction in the lamb's intake of the low protein diet below 840 kJ gross energy/day per kg0.73 (negative nitrogen balance); an increase in the dry matter content of the medium protein diet from 0.10 to 0.25; the addition of urea to the low protein diet (peak values 4–6 hr after feeding). PUN values estimated on successive days reflected a change in the protein content of the diet within 3–4 days, regardless of whether the change in protein concentration was from low to medium, or medium to low. It is concluded that PUN values can be used to evaluate protein quality only when experimental conditions are strictly controlled. Blood samples taken without regard to the above factors may give misleading results.
Comparison of sheep and cattle grazing on a semiarid grassland
Authors: Wilson AD
Published: November 2004

The botanical and chemical composition of the diet and changes in body weights of Hereford steers and Border Leicester x Merino wethers were compared over a 2-year period while grazing a semiarid grassland in adjacent paddocks. The grassland was a Danthonia caespitosa–Stipa variabilis type containing 200-800 kg per ha of green pasture consisting mainly of warm-season grasses, but also components of cool-season grasses, chenopod plants, medics and other forbs. The plots were permanently grazed by either sheep at 1.03 and 1.45 per ha or cattle at 0.13 and 0.18 per ha. Animals fitted with oesophageal fistulas were introduced at intervals to obtain estimates of the composition of the diet. The intakes by the cattle contained less of the short medics and cool-season grasses and more dry herbage than those of the sheep. As a result the diets of the cattle were consistently lower in nitrogen than those of the sheep. However, the in vitro digestibilities of the diets of both the cattle and the sheep were similar. The weight changes (expressed as either kg/ha or kg0.9g/ha) of both species were in the same direction and of similar magnitude, and do not support the belief that the semiarid winter-rainfall areas are more suited to sheep than to cattle.
Performance of male-sterile stocks of cotton as parents and hybrids
Authors: Thomson NJ
Published: November 2004

Two male-sterile lines of G. hirsutum containing G. anomalum or G. arboreum cytoplasm, their respective maintainer lines, and the M8 variety from which the male sterility stocks had been derived, were crossed reciprocally with each of three male fertility-restoring varieties. The F1 hybrids of the four male sterility stocks did not differ significantly in either lint yield or boll numbers. However, significant though small differences occurred in other traits including boll weight, lint percentage, seedling growth and some fibre properties. Pair-wise comparisons between sets of hybrids containing anomalum v. hirsutum, anomalum v. barbadense, arboreum v. hirsutum and arboreum v. barbadense cytoplasms showed that the diploid species cytoplasms did not significantly affect lint yield or the yield components of number of bolls and boll weight, while the other yield component, lint percentage, was only affected in one instance. Significant cytoplasmic differences in other attributes were rare. The recurrent G. hirsutum parent M8 outyielded its sterile derivatives both as a cultivar and as a hybrid parent. The yield decline of the male-sterile stocks was ascribed to nuclear (genomic) changes resulting from strong selection pressure for sterility during their development. It was concluded that, while the production of cotton hybrids from these male-sterile stocks is technically feasible, their practical utility is limited.
Bos indicus and Bos taurus crossbred dairy cattle in Australia. IV.* Progeny testing and expected rate of genetic improvement
Authors: Franklin IR , Hayman RH , Hewetson RO
Published: November 2004

A dairy improvement program designed to develop a breed of cattle adapted to tropical environments is described. Each year young crossbred (Bos indicus x Bos taurus) bulls are screened for heat tolerance and tick resistance, and then progeny-tested in the herds of cooperating dairy farmers. Estimates of phenotypic and genetic means, variances and correlations are presented for production of milk and milk components, and the rate of genetic improvement is discussed. In particular the heritability of milk yield in the crossbred progeny is 0.27, and the theoretical rate of improvement is 2.6% per year.

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*Part III, Aust. J. Agric. Res., 25: 1023 (1974).
Variation of leaf characteristics with level of insertion on a grass tiller. I. Development rate, chemical composition and dry matter digestibility
Authors: Wilson JR
Published: November 2004

The influence of leaf insertion level on the characteristics of blades and sheaths on primary tillers of a grass, Panicum maximum var. trichoglume, was examined for plants grown under controlled light, temperature and nutritional conditions. Leaves from insertion levels 3, 5, 7, 10 and 13 from the base of the tiller were harvested when first fully expanded and at 5, 10 and 20 days thereafter. The flag leaf (leaf 16) was harvested at full expansion only. Leaves of high insertion level developed more slowly, stayed green longer, and senesced more slowly than those of low insertion level. Leaf blades at the same stage of development showed a marked gradient in characteristics from low to high insertion level, the cell wall content increasing from 32.6 to 63.8%, the nitrogen concentration decreasing from 4.7 to 2.5%, and the dry matter digestibility decreasing from 77.3 to 65.0%. Overall, the percentage lignin tended to increase the higher the insertion level. Gradients for the sheath were generally similar to those of blades, but were less pronounced. The effects associated with insertion level reflected inherent ontogenetical changes in the structural characteristics of successive leaves. The changes may be important to potential forage quality, chemical composition, water relations of tissues, and the design of sampling technique. Nutrient status (e.g. critical values) may in some instances be better expressed on the basis of cell contents rather than dry matter.
Commercial application of biological control of mushroom bacterial blotch
Authors: Nair NG , Fahy PC
Published: November 2004

A range of substrates was tested to determine the optimum conditions for commercial preparation of antagonistic bacteria which appear to have potential for controlling bacterial blotch of cultivated mushrooms. The results indicate that gamma-irradiated peat at a moisture content of 50–60% (wet weight) or pF 3.5–2.6 and an incubation period of 4–5 weeks at 25°C favours the growth and survival of the bacterial anlagonists. The commercial life of the peat inoculants can be extended to 4 months if initially stored at 1 or 5°C and subsequently incubated at 25° for 4–5 weeks. Commercial trials with peat inoculants of the bacterial antagonists resulted in successful biological control of the disease, and in somc trials increased yields of 8–16.6% were obtained.
Interaction between sites of magnesium absorption in the digestive tract of the sheep
Authors: Tomas FM , Potter BJ
Published: November 2004

The effect of magnesium chloride infusion to different sites in the gastrointestinal tract of sheep upon the net absorption of magnesium from different regions of the digestive tract has been examined. Four Merino wethers were each prepared with cannulas sited in the rumen, in the duodenum adjacent to the pylorus and in the terminal ileum. The basal diet provided 18.45 mmoles magnesium/ day and an additional 65 mmoles magnesium/day as magnesium chloride was continuously infused into (A) the rumen, (B) the rumen and duodenum in equal portions, (C) the duodenum and (D) the terminal ileuni. A continuous infusion of Cr-EDTA to the ruinen enabled digcsta and magnesium flow rates to be estimated from digesta samples obtained from the intestinal cannulas at 4 hr intervals over 3 days. For treatments A, B, C and D respectively, the mean net absorption of magnesium (mmoles/day) from the rumen was 20.4, 11.4, 1.4 and 3.4; from the small intestine –0.5, 1.7, –5.1 and –9.8; from the large intestine 4.6, 2.2, 12.7 and 12.3; and from the total gastrointestinal tract 24.6, 15.4, 9.1 and 4.9. In each case the effect of treatment was significant. The total net absorption of magnesium caudal to the pylorus was unaffected by treatment. Plasma magnesium levels were reduced during post-ruminal infusion of magnesium, but these changes were not obviously linked to the changed net absorption from the intestinal segments. The urinary and faecal excretion of magnesium, but not the magnesium balance, was strongly related to the total net absorption of magnesium. The results emphasize the major contribution of the stomach to the gastrointestinal net absorption of magnesium and show that although the amount absorbed from this region may influence separately the net absorption from the large and small intestine, it does not appear to influence the overall intestinal net absorption of magnesium.
The phosphorus nutrition of the apple tree. II.* Effects of localized phosphate placement on the growth and phosphorus content of split-root trees
Authors: Taylor BK , Goubran FH
Published: November 2004

Effects of localized placement of superphosphate on the growth and phosphorus content of young apple trees were studied in two successive pot experiments with split-root trees grown in soil. Over a 2-year period both nil and excess superphosphate depressed tree growth, but localized applications of low to moderate rates of superphosphate only slightly depressed total tree growth, compared with uniform application of fertilizer to root parts. This suggests that non-fed root parts are supplied with sufficient phosphorus through redistribution within the tree to maintain active root growth. Tissue analysis clearly showed that the phosphorus content of tree tops in both experiments was dependent upon the proportion of root fertilized as well as the rate of fertilizer applied. However, the uptake of phosphorus by a root part was largely independent of whether superphosphate was applied to the other root parts. Further, a1 low (50–100 g per pot) but not high rates (200 g per pot or higher) of superphosphate, a higher phosphorus uptake per tree resulted from a uniform application of superphosphate than from an equivalent localized application. Although the trees absorbed phosphorus from localized application in proportion to the rate applied, analyses showed that a non-uniform distribution of phosphorus persisted within the trees even after two growing seasons. In particular, the concentration of phosphorus in non-fed roots remained low irrespective of the concentration in the roots in the fertilized zone. Therefore, while apple trees may be able to take up phosphorus from localized placement in proportion to the rate of superphosphate applied, the distribution of that phosphorus in trees following uptake may be non-uniform. The significance of this for tree performance in the field needs assessment in the long term.

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*Part I, Aust. J. Agric. Res., 26: 843 (1975).
A factor analysis of bread wheat quality tests
Authors: Orth RA , O'Brien LO , Jardine R
Published: November 2004

The statistical technique of factor analysis was applied to data obtained for 12 wheat quality tests performed on 27 wheats grown in one location and for one season. Three relatively independent major factors were identified, which together adequately accounted for the correlation matrix. The factors were: protein quality (α), grain hardness (β) and protein quantity (γ). These factors can most conveniently be measured by the proportion of flour protein insoluble in 0.05M acetic acid solution (residue protein), a particle size index test and the flour protein content respectively. These tests, together with milling yield, provide valuable information for selection purposes in the early stages of wheat-breeding programs.
Development of union abnormalities in grafts between lemon (Citrus limon) and Poncirus trifoliata
Authors: Bevington KB
Published: November 2004

A complete ring of bark was exchanged between seedlings of P. trifoliata and those of seven lemon cultivars, thereby producing P. trifoliata seedlings with a ring of lemon bark and lemon seedlings with a ring of P. trifoliata bark. Self-grafted controls were also propagated. The incompatibility of Eureka lemon–P. trifoliata combinations was clearly manifested at the graft union 7–9 months after grafting. Union abnormalities were detected only in lemon seedlings with a ring of P. trifoliata bark. They were not detected in P. trifoliata seedlings with a ring of lemon bark, nor in self-grafted controls. Anatomical studies revealed that the initial disturbance occurred in the outer phloem and spread along the rays towards the cambium. After the cambial zone was affected, the excessive proliferation of ray parenchyma disrupted vascular continuity. Extensive necrosis and gum deposition were evident in severely affected unions. The investigation showed that an early diagnosis of incompatibility is possible by examining the structure of the union.
Comparative responses of Lolium perenne and Bothriochloa macra to temperature, moisture, fertility and defoliation
Authors: Cook SJ , Lazenby A , Blair GJ
Published: November 2004

Lolium perenne and Bothtriochloa macra were grown alone and In 1/1 mixtures In pot culture under molsture stress and moisture non-limiting conditions at both high and low levels of fertility, they were grown In three controlled environment cabinets operating at either 16/10°, 23/17° or 31/25°C, and defoliated to either 1 cm or 4 cm from the crown at each of two harvests.Temperature was the dormant factor differentiating the growth and competitive ability of both species Lolium grew best In the 16/10° and 23/17°C temperature regimes, production declining at 31/25° In contrast, Bothriochloa made very little growth a1 16/10° and responded linearly to measuring temperature. Both species responded similarly to increasing fertility and favourable moisture conditions, although such treatments had no effect on Bothriocochloa in the 16/10°C temperature regime Bothtriochloa was more tolerant of low fertility and moisture stress than was Loliurn, especially at 31/25° Lolium yielded more, and competed successfully with Bothtriochloa, only under conditions of high fertility and In the absence of moisture stress at temperatures up to 23/17°C Defoliation intensity had little effect on the total dry matter yields of either species, although it did influence the proportion of leaf to head and stem of Bothtriochloa. The likely implications of the results on the competitive relationships of the two species In the field In the Northern Tablelands environment of New South Wales are discussed
Level of activity of nitrate reductase at the seedling stage as a predictor of grain nitrogen yield in wheat (Triticum aestivum L.)
Authors: Dalling MJ , Loyn RH
Published: November 2004

The yield of grain nitrogen of 24 wheat cultivars grown in the field was found to be related to the activity of the enzyme nitrate reductase (EC1.6.6.1) in the first vegetative leaf of 21-day-old plants grown in a controlled environment. It was concluded that a cultivar's potential for yielding grain nitrogen could be predicted from the activity of nitrate reductase at the seedling stage. This could enable the plant breeder to identify, early in the selection program, lines worth keeping for more advanced testing. Harvest index for nitrogen varied considerably between cultivars, but was usually largest in cultivars with large yields of grain nitrogen. Improvement in harvest index for nitrogen should go some way towards breaking the inverse relation between grain yield and grain nitrogen percentage in plants grown on a limited supply of soil nitrogen.
Inheritance of leaf rust and stem rust resistances in wheat cultivars Agent and Agatha
Authors: McIntosh RA , Dyck PL , Green GJ
Published: November 2004

The wheat cultivars Agent and Agatha each possess closely linked genes for resistance to Puccinia graminis tritici and P. recondita derived from Agropyron elongatum. The genes in Agent, located in chromosome 3D, were designated Sr24 and Lr24. The gene in Agatha for resistance to P. graminis tritici was designated Sr25 and is linked with Lr19 in chromosome 7D. Both Agent and Agatha possess additional genes for resistance to certain cultures of P. graminis tritici. Sr24 is considered a valuable source of resistance for wheat-breeding purposes, but Sr25 conferred an inadequate level of resistance to adult plants. A translocation from an A. elongatum chromosome to wheat chromosome 6A, present in Australian cultivars Eagle, Kite and Jabiru, carries a third gene, Sr26, for stem rust resistance.
Black leg (Leptosphaeria maculans (Desm.) Ces. de Not.) of rapeseed in Victoria: sources of infection and relationships between inoculum, environmental factors and disease severity
Authors: McGee DC
Published: November 2004

In established rapeseed-growing districts, ascospores discharged from crop residues were shown to be the major source of infection for black leg disease. Infection from seed was of relatively minor importance. The potential amount of ascospore inoculum on crop residues was related to severity of the disease in the original field. Rainfall of more than 1.0 mm was required for large ascospore discharges, but smaller ones occurred in light rain or dew. Discharge from the same crop residues increased greatly between April and May, remained at a high level until August, and then gradually declined until by January very few spores were discharged. In April, discharge resumed and the same cycle was repeated. The amount of crop residue surviving in fields from the previous year declined by 90% during the growing season. No relationship was apparent between the amount of rainfall during the period when infection occurred and the disease severity in crops sown at different times. Stem canker development was less severe in plants grown at 8° than in those grown at 12° and 15°C.
Studies on the epidemiology of peach rosette and decline disease in Victoria
Authors: Smith PR , Stubbs LL , Challen DI
Published: November 2004

The spread of peach rosette and decline dlsease (PRD) was studied in two clingstone peach orchards, located 24 km apart in the Goulburn Valley of Victoria. Over 11 years the incidence of diseased trees in an orchard of cv. Golden Queen increased from 0.9 to 91.5%, while in an orchard of cv. Pullar's Cling the proportion of diseased trees rose from 1.5 to 29.6% over 5 years. The apparent infection rates were identical in both orchards over the first 5 years of the two epidemics.In both orchards, a significantly higher proportion of healthy trees growing adjacent to previously diseased trees became infected in subsequent seasons. This pattern of spread of the disease is discussed in relation to pollen transmission of the viruses and the foraging habits of bees. The spread of PRD was reduced by 29.4% over 2 years by the grubbing of all visibly diseased trees before flowering in a planting of cv. Golden Queen. Removing the flowers from diseased trees at the 'pink bud' stage also reduced the rate of spread of the disease by 13.8% in 1 year. Removing newly diseased limbs at the crotch of the tree within 4 weeks of flowering, however, did not prevent the spread of the disease into the rest of the tree.
The intake and production of lactating Merino ewes and their lambs grazed at different stocking rates
Authors: Langlands JP
Published: November 2004

Grass and milk consumption and liveweight changes of lambs grazed at stocking rates ranging from 9 to 35 sheep/ha were measured during a 105 day lactation. Grass consumption and wool production of their mothers and of similar ewes without lambs were also determined. The forage and total organic matter intakes of the lamb increased with time while milk consumption declined; all three variables were negatively correlated with stocking rate. The intake of the ewe and its liveweight gain were not sensitive to increasing stocking rate, but wool production declined at higher stocking rates. The maintenance requirement of the ewes was estimated to be 218 kJ metabolizable energy/kg liveweight, and the efficiency with which metabolizable energy was utilized for milk production was 66%. Lactation increased the intake of the ewe but reduced its wool production.
The comparative nutritive value for weaner sheep of stubble and grain of pea, vetch and lupin crops
Authors: Arnold GW , Wallace SR
Published: November 2004

Weaner Merino wethers were used in three experiments to compare the nutritive value of lupin, pea and vetch grains and stubbles. In the first experiment, grain was offered either as the sole ration at 250 g day-1 or as a supplement of 0, 250 or 750 g day-1 to wheat chaff which was offered ad libitum. The grains were pea, vetch, lupin, barley and a 311 mixture of barley and lupin. The mixed grain was not offered as the sole ration, nor was barley offered as a supplement at more than 250 g day-1. There were only small differences in the nutritive value of the grains. The sheep ate less chaff when offered lupin or barley plus lupin grain than when offered pea or vetch grain. However, because the digestibility of the diets was higher with lupins, digestible organic matter intakes were similar within a level of feeding for the three legume grains. Substitution of barley for 75% of the lupins resulted in a lower intake of digestible organic matter than occurred with 100% lupins. In the second and third experiments the three legume grains were offered at 160 and 500 g day-1 respectively, in combinations with chaff of lupin, pea or vetch stubble offered ad libitum. Some differences in the value of the chaffs were found, but the grains had similar nutritive values when offered with any particular chaff. There were significant linear regressions between digestible organic matter intakes and liveweight gain, which were similar for the three experiments, with no differences between type of grain or type of chaff.
Mechanisms of frequency-dependent advantage in wheat
Authors: Phung TK , Rathjen AJ
Published: November 2004

The relationship between frequency-dependent advantage (f.d.a.) and competitive ability in wheat was investigated by growing F1 hybrids and their parents in paired combinations at two frequencies, 6.25% and 25%. The results indicated that a strong competitor had an increased yield at a low frequency when grown in a stand of a weak competitor (thus exhibiting f.d.a.); however, the weak competitor was not significantly reduced when it was grown at low frequency. One hybrid (Warimek*Tirngalen) did not show f.d.a, when grown in either parent, which indicated that heterozygosity did not necessarily lead to f.d.a. The strong competitor, Timgalen, also showed f.d.a, in a mixture of other varieties, which suggested that the mechanism which resulted in f.d.a. in this genotype was specific to this genotype. The physical basis of f.d.a, was studied in an experiment designed to permit assessment of relative competition for aerial and soil factors. The results indicated that f,d.a. was mainly associated with soil factors. Furthermore, there was a positive correlation between grain yield per plant and distance between the test plants, which suggested that f.d.a. was probably due to the interaction between roots of the same genotype in the exploitation of the environment in a slightly different way from that by other genotypes. The significance of f.d.a, in the maintenance of genetic polymorphisms is discussed.