Showing papers in "Crop & Pasture Science in 1957"

The effect of aggregate disruption on the activity of microorganisms in the soil

Abstract: Laboratory tillage of soils causes an increase in the oxygen uptake of soil microorganisms. The effect is closely related to the extent of aggregate disruption caused by the tillage treatment and is attributed largely to exposure of organic matter that was previously inaccessible. In some soils drying and rewetting after tillage causes a further increase in microbial activity, but this is not accounted for by disaggregation. As drying and rewetting commonly follow tillage in the field the resultant higher microbial activity could contribute to the faster mineralization of organic matter in arable land.

Effect of volatile fatty acids, lactic acid and ammonia on rumen pH in sheep

Abstract: Data are presented on pH, volatile fatty acid, lactic acid, and ammonia nitrogen levels in the rumen of sheep being hand-fed on a wide range of diets. It is concluded that the rumen pH rarely falls outside the range 5.0-7.5 on diets on which lactic acid never accumulates in the rumen after feeding. On such diets rumen pH is closely related to the volatile fatty acid level. Evidence is presented which indicates that the pH-volatile fatty acid relationship on different diets may be considerably modified by variations in salivary secretion and in the accumulation of ammonia nitrogen in the rumen after feeding. The contribution of ammonia nitrogen to the total buffering capacity of the rumen is discussed. Lactic acid only accumulated in the rumen on diets containing high levels of soluble carbohydrate or starch. Lactic acid levels above 20 mM were always associated with pH levels below 3.0, but although levels higher than 80 mM were often recorded, lumen pH levels never fell below 4.33. On these diets rumen pH was closely related to the level of volatile fatty acid or lactic acid or both in the rumen.

Changes in organic matter and pH in a podzolic soil as influenced by subterranean clover and superphosphate

Abstract: A further investigation has been made on soils examined by Donald and Williams (1955) in a survey of the influence of superphosphate and subterranean clover (Trifolium subterraneum L.) on podzolic soils formed on granodiorite in the Crookwell district of New South Wales. The soil organic matter was found to have approximately constant proportions of carbon, nitrogen, sulphur, and phosphorus in the ratio 155 : 10 : 1.4 : 0.68, and it is suggested that the rate of build-up of soil organic matter under the clover pastures may have been limited by the amounts of sulphur supplied in the superphosphate top-dressings. The soil organic matter was found to have a cation-exchange capacity a t pH 7.0 of about 220 m-equiv./100 g, and increases in soil organic matter have led to substantial increases in the cation-exchange capacity of the soil. About 75 per cent. of the total cation-exchange capacity of the unimproved soils was due to organic matter while, in the most improved soils, this figure approached 90 per cent. The increases in cation-exchange capacity included increases in exchangeable hydrogen and were accompanied by decreases in soil pH. There were increases equivalent to 6.5 lb of exchangeable potassium, 25.5 Ib of exchangeable calcium, and 5.2 lb of exchangeable magnesium per acre in the surface 4 in. of soil for each hundredweight of superphosphate applied per acre. Increases in soil organic matter also resulted in increases in the field capacity which may reflect improvements in soil structure. Results indicate that heavier rates of superphosphate application would increase the rate of fertility build-up.

Sperm transport in the fowl

Abstract: (1) The distributions of living and dead sperm in the oviducts of hens a t various time intervals after artificial insemination were determined by using sperm labelled with 32P and assaying the radioactivity of serial sections of the oviduct. Appropriate. tests of the method showed it to be valid and reasonably accurate for short-term experiments. (2) The number of sperm reaching the site of fertilization at the upper end of the oviduct (the infundibulum) was dependent primarily on where in the lower genital tract the sperm were deposited. Following intravaginal insemination with 2 X 108 sperm, from 7 X 103 to 70 X 103 sperm were detected in the infundibula of different hens up to 1 hr after insemination. After intra-uterine insemination with a like number, from 137 X 103 to 2642 X 10103 sperm were detected. (3) The junction of the vagina and uterus (or shell gland) proved to be a barrier to sperm progress, as was shown by the greater efficiency of sperm utilization above the junction than below it. (4) Dead sperm inseminated intravaginally did not pass into the uterus but those inseminated into the uterus reached the infundibulum in as great numbers as a similar sample of living sperm. This suggested that the mechanism of sperm transport differs on either side of the uterovaginal junction. (5) From the speed of transport of sperm and the passage up the oviduct of sperm-free fluid injected into the uterus, it is suggested that the spasmodic contraction of muscle investing the wall of the upper vagina and lower uterus induced as a response to tactile stimuli is mainly responsible for sperm movement from the uterovaginal junction to the infundibulum. (6) Motility of sperm is necessary only to traverse the vagina and perhaps to penetrate the vitelline membrane of the egg during the process of fertilization. At other stages of movement between the vagina and the egg, sperm play a passive role in their own transport.

Hair follicle group and skin follicle population of Australian Merino sheep

Abstract: Skin specimens from 495 Australian Merino ewes were collected from 22 flocks, including 9 parent studs out of the 17 identified in the contemporary population. Flocks from all of the 4 important strains of the Australian Merino are represented. The skin samples were collected by a standard biopsy method devised for the purpose by the authors, and histological sections prepared. The techniques are described and data for the following estimations presented: mean total (np+z) follicle population density; mean primary (np) follicle population density; ns/np ratio; mean primary (dp) fibre diameter; mean secondary ( da ) diameter; mean fibre diameter of the composite population (dp+s); mean ratio of primary and secondary fibre diameters (dp/ds). For each flock the mean and standard error of the estimations are tabulated and the range of individual values observed summarized for each of the four Merino strains. The data are presented as the material on which further more detailed analyses will be made; the need is stressed for extending these studies, which form an important basis for genetic studies of fleece structure in the Merino and other breeds. Attention is also drawn to certain extreme variants in the hair follicle group, one of which (a very small group) may prove to have a simple hereditary origin.

The early vegetative growth of three strains of subterranean clover (Trifolium subterraneum L.) in relation to size of seed

Abstract: Three strains of subterranean clover (Bacchus Marsh, Clare, and Mount Barker) were grown in pot culture at the Waite Agricultural Research Institute; for each strain, seed of four widely separated sizes mere sown. Dry weight a t any one time in the early vegetative stage was linearly related to embryo weight, but was independent of strain. Hence differences in early growth noted under uniform environmental conditions between strains are the result not of differing relative growth rates, but of differences in the size distribution within the seed populations; evidence is presented suggesting that there may well be little difference in the size distribution of seed of Bacchus Marsh and Mt. Barker, but that Clare contains a higher proportion of large seed, and thus as a strain would be expected to give greater early production. Leaf area per plant was also linearly related to embryo weight but independent of strain; but for a common embryo weight, Clare was found to have fewer leaves than the other two strains. Examination of the areas of successive leaves showed that the maintenance of similar total leaf areas depended on a balance of rate of leaf production and size of individual leaves; in relation to Bacchus Marsh and Mt. Barker, Clare has fewer but large1 leaves.

Seed size as a factor in the growth of subterranean clover (Trifolium subterraneum L.) under spaced and sward conditions

Abstract: The significance of seed weight in the growth of subterranean clover (Trifolium subterraneum L) , of the Bacchus Marsh strain, has been assessed under both spaced plant and sward conditions at the Waite Agricultural Research Institute. Under conditions of spacing, plants of three widely separated seed size grades were grown a t a density of 1 per 25 sq. links. The dry weights of the plants were proportional to seed weight from the time of sowing (in May) till the end of October – over almost the entire growing period of the crop. Three sets of swards were grown a t a density of 25 plants per sq. link, each sward being planted with seed of one of the three sizes. Dry weight was proportional to seed weight in the early part of the season but when the swards reached a leaf area index of about 4 (i.e. when there were 4 sq. links of leaf surface on 1 sq. link of ground), a reduction in growth rate occurred. This critical leaf area index was reached first in "large seed" swards, followed later by "medium seed" and finally by "small seed" swards. Thus there was a period in which the swards were growing at different rates, and in which the dry weights came to parity, so that on the final sampling occasion (in December) there was no significant difference between the dry weights of the swards from the three seed sizes. It is concluded that a t a leaf area index of about 4, interception of incident light energy is complete.

Microbial antagonism in the rhizosphere as a factor in the failure of inoculation of subterranean clover

Abstract: In an investigation into the cause of poor nodulation of subterranean clover on a yellow podzolic soil the following results were obtained: (1) Failure of seed inoculation was due to microbiological antagonism which prevented normal colonization of the rhizosphere by the bacteria in the applied inoculum. (2) The antagonism was shown to be confined to the clover rhizosphere. (3) Greater rhizosphere populations were obtained by the use of increased rates of inoculation or with normal rates on the sites of log fires. This latter effect was attributed to the presence of charcoal. (4) The technique used for the determination of numbers of nodule bacteria in the clover rhizosphere was found to give an early and reliable evaluation of the success of inoculation.

Studies on salt tolerance of sheep. I. The tolerance of sheep for sodium chloride in the drinking water

Abstract: Four groups, each of six sheep, were fed in pens for 15 months on an adequate diet of chaffed lucerne and wheaten hays. One group was offered rain-water to drink, whereas the others were offered similar water to which sufficient sodium chloride had been added to give concentrations of 1.0, 1.5, or 2.0 per cent. sodium chloride. The intake of water increased with concentration of sodium chloride, the mean daily intakes for the entire experiment being 2.0, 3.0, 4.4, and 3.0 1. for the groups whose water contained 0, 1.0, 1.5, and 2.0 per cent. sodium chloride, respectively. It also increased in all groups with temperature, being 50-70 per cent. higher in the hottest months than in the coldest months. The intake of sodium chloride by some sheep was very high; four of them consumed over 115 g (0.25 lb) daily for more than half the experiment, and 170-230 g daily for periods of 1-10 weeks. A concentration of 1.0 per cent. sodium chloride in the drinking water had no adverse effects on the sheep, but 1.5 per cent. TI-as detrimental to a small proportion and 2.0 per cent. was detrimental to all of the sheep. There was a decline in food consumption and body weight of the affected ammals, and several receiving 2.0 per cent. sodium chloride became very emaciated and weak and two were killed in extrentis. The only other obvious sign was an occasional diarrhoea which occurred in most of the sheep receiving 2.0 per cent. sodium chloride. Sodium chloride in the drinking water had no effect on the concentration of sodium, potassium, calcium, or magnesium in the blood plasma. It did, however, affect the chloride concentration; this was significantly higher, throughout the experiment, in the group which received water containing 2.0 per cent. sodium chloride.

Effect of diet on individual volatile fatty acids in the rumen of sheep, with particular reference to the effect of low rumen pH and adaptation on high-starch diets

Abstract: Detailed data are presented on changes in the proportions of acetic, propionic, and butyric acids in the rumen after feeding on various diets. Pre-feeding proportions were constant on each diet but varied from a mixture of 72-76 per cent. acetic, 14-16 per cent. propionic, and 10-12 per cent. butyric acid on all-roughage diets to one of 63-65 per cent. acetic, 18-20 per cent. propionic, and 16-18 per cent. butyric acid on a diet containing 70 per cent. wheat grain. On all diets the proportion of propionic acid increased after feeding and reached a peak which coincided with the maximum level of total volatile fatty acids. The response of butyric acid was variable, low levels being recorded on a diet of lucerne chaff and on one containing a high proportion of cracked maize. The proportion of acetic acid always declined after feeding. These responses were modified in experiments on rations containing high proportions of wheaten starch, in which rumen pH fell below 5.0 as a result of lactic acid accumulation. When animals were first fed on such diets, a decline in rumen pH below 5.0-5.5 after feeding was always associated with a pronounced decline in the proportions of propionic and butyric acids, to levels as low as 8 and 5 per cent. respectively. Continued feeding of such diets did not affect the response of butyric acid, but there was evidence of a change in propionic acid production in response to low pH conditions, both in respect to short-term change during experiments in which low rumen pH levels were maintained for considerable periods and to long-term change when such diets were fed intermittently over considerable periods. The implications of these findings are discussed with respect to the effects of pH on individual volatile fatty acid production in the rumen, and on the qualitative nature of the microbial population and on their metabolic patterns.

Influence of rams on ovarian activity and oestrus in Merino ewes in the spring and early summer

Abstract: The occurrence of oestrus and ovulation and the changes in the vaglnal contents were studied in Merino ewes following the introduction of vasectomized rams at various times during the spring and early summer. The ewes were in an anoestrous state when the observations were commenced. Except in occasional ewes oestrus did not appear until early December. It had occurred in all except a few ewes by early January. In most ewes among which rams were introduced on October 26 or November 18, it occurred about a week earlier than in ewes among which rams mere not introduced until December 8, and ewes among which rams had been running continuously. In at least 80 per cent, of animals in which both were studied, oestrus was accompanied by massive desquamation of the vaginal epithelium and it was preceded by one or more periods of massive desquamation. Between December 8 and December 14, masses of desquamated epithelial cells were present in the vaginal contents in few only of the ewes which were held separate from rams, but in almost all ewes among which rams were introduced on December 8 (group 4), and in most of the em7es which were running continuously with rams (group 6). They first appeared in the ewes of group 4 between December 11 and December 14, 3-6 days after the introduction of the rams, whereas they were already present in almost all of the ewes of group 6 by December 11.Corpora lutea compatible with ovulation shortly after December 8 were present in most ewes among which rams were introduced on that day, and in few ewes which were held separate from rams. The significance of these results is discussed.

Ruminal flora studies. VIII. The influence of rate and method of feeding a ration upon its digestibility, upon ruminal function, and upon the ruminal population

Abstract: A single ration made up of commercial sheep cubes (20 per cent. protein) together with oaten and lucerne chaff was fed to five sheep in five different ways. A Latin square design was used. Measurements were made on the ruminal population, the metabolism within the rumen, and the overall nitrogen balance and dry matter digestibility. Each of the different treatments resulted in a distinctive pattern in the ruminal population, pH, ammonia nitrogen, and volatile fatty acid levels. There were significant differences in dry matter digestibility and nitrogen retention. The daily ration given as a single feed gave the lowest dry matter digestibility and nitrogen retention. It also caused the greatest fall in pH values and bacterial counts, and the lowest protozoal counts. The highest ruminal ammonia nitrogen levels were also associated with this treatment. The best performance was obtained by feeding the concentrate in the morning and roughage in the afternoon, or feeding the whole ration in four equal portions at 2-hr intervals. The other two treatments – half ration morning and afternoon, or chaff in the morning and concentrates in the afternoon – gave intermediate results. Some implications of the various data are discussed, and the strong influence of feeding pattern is stressed.

Ecological Observations on the Cattle Tick, Boophilus microplus (Canestrini).

Abstract: Studies were undertaken during 1948-1950 on Boophilus microplus under field conditions in southern Queensland to determine the duration of the non-parasitic stages, and to relate this information to tick incidence on cattle In the area where the observations were made, the population of ticks on cattle is high in summer and autumn and low in minter and spring Each week throughout the investigation engorged female ticks, freshly fallen from cattle, were placed in a pasture plot and their subsequent history recorded Concurrently, observations were made on the changes in tick population on a dairy herd on an adjacent farm Female ticks exposed on the plot between April and July produced virtually no progeny, and it is probable that the ticks in the pasture traversed by the dairy cattle exhibited a similar, though less severe, inhibition of reproduction This failure to reproduce, combined with the dying out of larvae and protracted developmental periods of eggs, reduced to very low levels the larval population available to infest cattle during the months of August–October Ticks exposed from late July to the following autumn produced progeny There was a tendency for the progeny of ticks exposed in the late winter and early spring to hatch a t about the same time in the late spring, and this synchronous hatching was probably responsible for the 'spring rise' in tick population on cattle It appears likely that the engorged female adults dropped in the early autumn represent the most important stage in the overwintering of the species in this area Some of their larvae survive the adverse winter conditions, either in the free-living or the parasitic stage, and give rise to adults, which fall in the late winter and spring, and which in turn produce the larvae of the spring rise

The heat balance of sheep standing in the sun.

Abstract: An extension is made of Lee's (1950) original discussion of the heat balance of sheep exposed to a tropical sun. Methods are given for calculating the two quantities, convective heat loss and long-wave radiation exchange, which automatically compensate to a large extent for the added heat load. There appear to be advantages in distinguishing between the heat balance of the fleece and that of the body of the sheep, and this provides a method of estimating the heat conducted to the body as a consequence of the insolation.

Reactions of calves to infestation with the stomach worm, Haemonchus placei (Place, 1893) Ransom, 1911

Abstract: Studies aimed a t determining the factors responsible for haemonchosis in cattle are reported. Observations on natural populations of Haemonchus placei confirmed the conclusions of Roberts, O'Sullivan, and Riek (1932) on the acquisition of resistance to this species and on the relationships of peak egg counts to the age of the animal and season of the year. Most of the 400 calves on which these observations were based developed a strong resistance and suffered no apparent ill effects; others only became resistant after suffering clinical haemonchosis; and about 8 per cent. either failed to develop resistance or lost it and died. Experiments with single doses, spaced doses, and continuous doses of larvae showed that H. placei has a comparatively short patent period. The trend assumed by the egg counts, irrespective of the method of infestation, was very similar, reaching its peak about the 6th to 10th week and thereafter rapidly declining to remain a t low levels. Calves on a 12 : 1 mixture of oaten and lucerne chaff gave much higher egg counts than calves on good quality lucerne alone, but the infestations did not vary in their persistence. A strong resistance was acquired, even from a single dose of larvae. This was shown by the failure of a test dose of larvae, administered after the egg count had been at low levels for some weeks, to cause any increase in the egg count; and by the presence, several weeks later a t autopsy, of relatively few adult worms, most of which were undersized with females containing few or no eggs. There were also numerous fourth stage larvae which had evidently persisted in this stage for many weeks. That so many immature worms occurred in resistant animals may signify that these young stages could be extremely important in the epidemiology of haemonchosis. "Selfcure", as defined by Gordon (1948) for H. contortus in sheep, could not be produced experimentally with H. placei in cattle, but egg count trends suggest that this type of reaction may sometimes occur among natural populations before resistance is finally acquired. Circulating antibodies could not be detected in experimentally infested animals. They were found, however, in animals with natural infestations of mixed species, and it is probable that in the latter case they were associated rather with Trichostrongylus than with Haemonchus. Data on egg counts in relation to the number of adult female worms present in experimentally infested calves strongly suggest that whilst the animal remains susceptible to infestation, egg counts are usually an accurate index of the degree of infestation, but that when resistance occurs the egg count is of little value for this purpose.

The Spelling of Pasture in Cattle Tick Control.

Abstract: When two comparable herds of cattle were kept continuously in adjoining paddocks, frequent acaricidal treatment was necessary to control ticks (Boophilus microplus (Canestrini) ). Thereafter, one of the two herds was grazed alternately in its own and an adjacent paddock, the intervals between each transfer being sufficient to ensure that most of the ticks in the unoccupied paddock had died. Tick infestations on this herd were greatly reduced, and less frequent use of acaricides was necessary. The herd remaining in the continuously stocked pasture continued to need acaricidal treatment for recurring tick infestation. In a field trial with 350–400 cattle moved a t intervals to each of three formerly heavily infested paddocks, tick infestations remained very light, although the herd was dipped only In January, September, and the following January. A control herd on continuously stocked pasture, treated at the owner's discretion, required eight dippings in this period. This procedure of "pasture spelling" seems likely to be widely applicable in central Queensland.

Bunch spear grass dominance in burnt pastures in South-Eastern Queensland

Abstract: The results are reported of a study of the effect of annual burning, in the absence of grazing, on the botanical composition of a native pasture in south-eastern Queensland. The main effect of burning was to give dominance of Heteropogon contortus (L.) Beauv. ex R. & S. This appeared to be due to three main causes: established plants were resistant to fire; fire favoured the germination of seed; and fire reduced the basal ground cover of other species. The effects on other species and on the proportion of bare ground are reported. The significance of the results in relation to the present distribution of H. contortus-dominant pastures is discussed.

Hair follicle group and skin follicle population of some non-Merino breeds of sheep

Abstract: Skin specimens from 494 ewes were collected in flock samples of 11-23 animals, mostly 8-18 months old, from Australian and overseas sources among the following breeds: Corriedale, Polwarth, Lincoln, English Leicester, Border Leicester, Romney Marsh, Southdown, Dorset Horn, Suffolk, Ryeland, Scottish Blackface, Welsh Mountain, Swaledale, Cheviot, Wiltshire, and Swedish Landrace. The specimens were taken by a standard biopsy method and evaluated in the manner described by Carter and Clarke (1956). For each flock sample the mean, standard error, and range of individual values were recorded for the following estimates : total (np+s) follicle population density; primary (np) follicle population density; ns/np, ratio; primary fibre diameter (dp); secondary fibre diameter (2,) ; fibre diameter of the composite population (dp+s) ; of primary and secondary fibre diameters (dp/ds) . The data supplement those recorded for the Australian Merino sheep (Carter and Clarke 1957), and demonstrate the small hair follicle groups apparently characteristic of most British short-, long-, and carpet-wool breeds in well-marked contrast to the large groups in the skin follicle population of the Australian Merino. This difference between the Merino and other breeds may be general except where new breeds have developed from crossing with the Merino or its derivatives, when hair follicle groups of intermediate size may be found as in the Corriedale and Polwarth.

Effects of inbreeding on four families of Peppin Merinos

Abstract: The influence of inbreeding on several fleece and body characters in a strain of Australian Merino sheep is reported. The four families from which data were taken were derived from a single strain of Peppin Merinos. Inbreeding without selection has been carried on since the foundation of the families between 1939 and 1944. Inbreeding is responsible for a reduction in body size, fertility, greasy and clean fleece weight, and wrinkle score, but has relatively little influence on the fleece components (yield, staple length, fibre diameter, and density of fibre population). It follows that the reduction in fleece weight is a direct consequence of a decrease in total fibre number. Since the reduction in fibre number is likely to be a correlated effect of low pre-natal and early post-natal growth rates, it is suggested that the inbreeding has had no genetic effect on the several independent systems involved in adult wool production but has affected only those associated with fitness and vigour. The depression due to inbreeding therefore may not be caused by specific gene fixation but by increased homozygosity per se.

Studies on the reactions of animals to infestation with ticks. I. Tick anaemia

Abstract: Tick anaemia appears to be caused mainly by loss of the blood ingested by the engorging ticks. It is possible that some toxic effects of the salivary secretion may help to account for the slow recovery of heavily infested animals in poor condition, even after the infestation has been removed and an adequate supply of feed provided. Animals in poor condition showed a marked fall in red blood cell concentration and haemoglobin content following heavy infestation with Boophilus microplus (Canestrini), whereas animals in moderate to good condition showed a much smaller and more temporary reduction in these components. When submitted to very heavy infestations, even animals in good condition showed a considerable reduction in these components and in serum protein, all of which, however, soon returned to normal following cessation of the infestation. Many of the heavily infested animals, especially those in poor condition, carried large numbers of translucent adult female ticks, which were filled with a clear fluid similar to bovine plasma, instead of normal ticks, which were dark in colour owing to the ingested blood.

Studies on the reactions of animals to infestation with ticks. II. Tick toxins

Abstract: Toxin has been shown to be present in the eggs of 17 species of ixodid ticks, and is probably present in the eggs of all species of this family. It was associated with the globulin fraction of the egg extract, and was thermolabile. Similar toxin was also present in the larvae of the only four species of ixodid ticks of which larvae were tested. The toxin was not present in the eggs of the five species of argasid ticks used in this study. Clinical syndrome and the pathological changes in the tissues of laboratory animals following injection of egg extracts were indicative of toxaemia. At a dose rate of 0.3 g/kg body weight, there was a rapid initial rise in rectal temperature, followed by subnormal temperature and death. At lower dose rates, there was loss of hair a t the site of injection, and usually the development of an indurated, sterile ulcer. The toxin appeared to be quite distinct from the one that causes tick paralysis, which, in Australia, results from infestation with Ixodes holocyclus Neumann.

Strategic dipping for control of the catle tick, Boophilus microplus (Canestrini), in South Queensland

Abstract: In the spring and early summer of 1953, three cattle herds in south Queensland were dipped in acaricides at intervals such that few or none of the cattle ticks (Boophilus microplus) attacking to the animals between dippings reached maturity. This was continued until the tick larvae hatching in the pastures in spring were greatly depleted in numbers, but was discontinued before they were exterminated, to avert the danger of the cattle losing their immunity to redwater fever. Throughout the rest of the summer and the early autumn these cattle were lightly infested, and required dipping relatively infrequently. On the other hand, on a property where early, intensive dipping had not been carried out, very heavy infestations of ticks were present throughout the summer and autumn in spite of monthly dippings. This procedure of relating times of dipping to the ecology of the tick has been termed "strategic dipping". In the 1954-55 season, results obtained by intensive spring and early summer dipping were not comparable with those of the 1953-54 season. This appeared to be attributable principally to delayed or relatively ineffective dippings at critical times. Effective application of strategic dipping, as during the 1953-54 season, would reduce the need for acaricidal treatment of the cattle in the summer months when dipping is likely to be delayed by rainy periods.

The physical factors involved in the drying of sultana grapes

Abstract: The various physical factors involved in the drying of sultana grapes have been determined from measurements of drying rate under definite conditions of temperature, humidity, and air flow, in a specially constructed oven. Ninety-five per cent. of weight lost is water, 2 per cent. is carbon dioxide produced at an almost constant rate during drying, and 3 per cent. unassigned loss. Drying occurs in three distinct stages: (1) the grape retains its regular ellipsoidal shape by an elastic contraction of the skin; (2) the skin commences to wrinkle in the range of 20-50 per cent, loss in original weight; (3) the drying rate decreases markedly, beginning when approximately 95 per cent. of total loss of weight has occurred and when probably all the free water has been removed from the system. For each of these stages there is a linear relation between time and log [c / (c – w) 1, where c is the total loss in weight on complete drying (approximately initial water content), and w is the loss in weight at time t. A drying constant has been calculated from this logarithmic function for the initial stage of drying, and has been used for determining the mechanism of drying. Water movements through the parenchymal cells are fast compared with those through the skin. Since various dipping treatments give different drying rates there is no rate-controlling diffusion through the stationary air layer a t the grape surface. The drying rate is controlled by the diffusion of water through the waxy cuticle, and is inversely proportional to the amount of cuticle present as determined by extraction with chloroform. The elastic contraction of the skin causes an increase in the thickness of the cuticle which reduces the permeability. The heat required for the evaporation of water and for heating the grape to the equilibrium drying temperature is transferred from the surroundings to the grape. The rate of drying increases rapidly with rise in temperature owing to the vapour pressure of water and the permeability of the cuticle increasing with the temperature.

Decomposition of oxalic acid in vitro by rumen contents

Abstract: The rumen contents of sheep habituated to the intake of small quantities of oxalic acid are able to decompose considerably increased amounts of this substance. The presence of excess calcium decreases the amount decomposed.

Photoperiodicity in cattle. II. The equatorial light environment and its effect on the coat of European cattle

Abstract: Thirteen European cattle have been maintained for periods of up to 21 months in a light environment artificially adjusted to provide 12 hr 50 min of light daily, so simulating the equatorial photoperiod. The initial coat reaction of several groups of these animals differed according to the season in which they entered the experiment. Thus transfers in the spring and autumn were followed by complete shedding; those in winter by a rapid partial shed; and those in the summer by rapid growth of hair. On adaptation to the new environment, however, all the groups eventually grew, and thereafter permanently maintained, a similar coat, characterized by intermediate length and furry appearance. The experiments show that the equatorial photoperiod eliminates the natural coat cycle of European cattle, and that it tends to maintain them in a heat-retaining type of coat.

The breed structure and genetic analysis of the pedigree cattle breeds in Australia

Abstract: (i) The breed structure and genetic history of the pedigree Jersey breed in Australia are analysed by pedigree sampling methods. (ii) The breed structure may be divided into four levels, with imported animals at the top determining the genetic make-up of the breed. Animals imported since 1900 have made a genetic contribution to the breed in 1950 of 61.8 per cent. At least two substructures exist within the breed, based respectively on the major herds in Queensland and those in the rest of Australia. (iii) The genetic contribution to the breed of the most important of the herds is only 7.0 per cent. (iv) Determination of the percentage direct relationship of important animals in five sample years shows that no one animal has made a major contribution to the genotype of the breed. (v) The degree of inbreeding (base year 1900) is calculated. The total inbreeding in 1950 (4.19 per cent.) comprises 1.31 per cent. current inbreeding, 0.51 per cent. long-term inbreeding, and 2.37 per cent. strain inbreeding. The index of subdivision calculated from the non-current and long-term inbreeding is 5.65, indicating that the breed is subdivided into strains. (vi) The effective generation length for each of the pedigree breeds – Jersey, Australian Illawarra Shorthorn, Friesian, Ayrshire, and Guernsey – in Australia is 5 years. Most bulls are used when they are 1-3 years old, and are then lost to the pedigree industry. It is shown that the bull requirements of the above breeds could be met by the progeny of performance-recorded animals. Whether this would increase the rate of genetic improvement is discussed briefly. (vii) Genetic improvement in the Jersey breed could best be achieved by: ( a ) stopping further importation; ( b ) closing the breed in each environment and concentrating selection within these regions to develop strains adapted to each particular environment; ( c ) selecting on production records rather than using genetically unknown sires and dams, particularly in the major breeders' herds.

Relations between crimp and fineness in Australian Merinos

Abstract: The relation of diameter to crimp is analysed for five of the main strains of the Australian Merino, run in three locations in a number of seasons. It is shown that the change in diameter indicated by a given change in crimp within one flock varies considerably from strain to strain; but on the average it is only about half the change which would be predicted from the same difference in crimp between wools from different flocks, either from different strains or from different environments. The regession coefficient of diameter on crimp within a flock is not appreciably affected by age or environment. Age has little effect on the average crimp but in some strains it may change the diameter considerably. Similarly, environment usually only changes crimp to a small extent, but has very marked effects on the diameter. As a result, the average diameter associated with a given crimp may vary considerably with age or environment. This differential effect may be so great that a fine-woolled strain in a good season may produce wool of the same diameter as a medium-woolled strain in a poor season, although the three strains still retain their characteristic crimpings.

The inheritance of flowering time in Trifolium subterraneum L

Abstract: The inheritance of flowering time in subterranean clover, using a number of strains and hybrids among them, was investigated on autumn-sown material at Canberra. Heterosis and dominance were not found, and genetic variation was polygenic. An F1 diallel analysis and F2 two-way analysis showed that approximately 90 per cent. of the total variance was attributable to additive genetic effects. An estimate of the repeatability of strain performance over two seasons showed that small but significant strain-year interactions were occurring. Strain repeatability, as measured by intraclass correlation, was 86 per cent. A breeding test involving F2 selections and their progeny gave a mean parent-offspring regression of 0.86 over the six crosses studied, which is well in accord with expectations of breeding behaviour based on the above analyses. The results are discussed in relation to other studies on flowering time, especially with reference to the problem of interpreting results based on the threshold expression of a character dependent on the value of a continuously variable factor.

Sodium chloride supplementation of high-grain diets for fattening Merino sheep

Abstract: In an experiment lasting 60 days the effect of adding sodium chloride to five types of diet was studied in young Merino wethers. The diets used were 100 per cent. oat grain, and 50 : 50 as well as 75 : 25 mixtures of oat grain with lucerne chaff on the one hand, and with wheaten chaff on the other. The addition of 0.25 per cent. sodium chloride to these diets resulted in increased food consumption and improved efficiency of food utilization, with significant increases of 19-58 per cent. in body-weight gains. The unsupplemented diets contained 0.009-0.062 per cent. sodium and 0.05-0.42 per cent. chlorine. There were indications that the lack of sodium was the limiting factor in these diets, and that the sodium requirement of these sheep was greater than 0.06 per cent. of the diet, or 0.88 g per day. Dietary sodium intake did not affect serum-sodium levels, except those of sheep fed on the 50 : 50 mixture of oats and lucerne chaff in which they were significantly higher. Serum-potassium levels were slightly, but significantly, higher in sheep fed on the low-sodium diets. In a second experiment the two groups which had received the 75 : 25 mixture of oat grain and wheaten chaff were fed on the mixture for a further 29 days, but the group which had not received sodium chloride was given 0.37 per cent. sodium bicarbonate. The response was similar to that of the group which received sodium chloride.

The movement of cobalt and zinc in soils as indicated by radioactive isotopes

Abstract: A method has been developed whereby labelled cobalt and zinc were applied to the surface of columns of soil in order to study the movement of these cations under the influence of rainfall and various fertilizer treatments. The results of the investigation demonstrate that in soils of moderate exchange capacity, whether this is provided by clay or by organic matter, the cobalt and zinc remain close to the surface of the soil even after the application of water equivalent to several years' rainfall and dressings of copper sulphate, superphosphate, aqueous extract of lucerne, and water saturated with carbon dioxide. With very light soils of low exchange capacity a year's rainfall alone did not leach the cobalt or zinc downwards, but rainfall which followed treatments with the same dressings induced a considerable downward movement of both cobalt and zinc.