bluuebunny/crossref_metadata_2025 huggingface dataset:
Relations between crimp and fineness in Australian Merinos
Authors: Roberts NF , Dunlop AA
Published: November 2004

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.
Sweat glands in Zebu (Bos indicus L.) and European (B. taurus L.) cattle. II. Effects of season and exercise on sweat gland volume
Authors: Hayman RH , Nay T
Published: November 2004

Seasonal variation in sweat gland volume is reported in two breeds of Zebu dairy cattle. Changes which occurred in the volume of sweat glands in Jersey and in Zebu x Jersey cattle, as the result of sweating induced by exercise, are described. The crossbred cattle, which had larger sweat glands than the Jerseys, sweated at a greater rate, and had a smaller rise in rectal temperature, which returned more rapidly to normal. It is suggested that there is a relationship between sweat gland volume and activity, and that the seasonal changes in volume observed in the two Zebu breeds are largely due to changes in ambient temperature.
Depletion of gamma isomer from benzene hexachloride cattle-dipping fluids
Authors: Roulston WJ , Schuntner CA
Published: November 2004

A differential loss of the isomers from BHC cattle-dipping fluid was demonstrated, the concentration of the gamma isomer decreasing faster than that of the total of all isomers. Parallel with the reduction in gamma-BHC content, the toxicity of the fluid for cattle ticks also lessened. This depletion of the gamma isomer occurred not only in field dipping vats, but also during laboratory storage of dipping fluid contaminated with animal waste products and soil. A decrease in the gamma isomer concentration was always accompanied by a chloride increase, which was evidence of at least a partial breakdown of the BHC molecule, but in field dipping samples the chloride increase was not a quantitative measure of gamma isomer depletion. Autoclaving failed to prevent depletion in subsequently stored samples, and refluxing BHC in suspensions containing cattle dung produced a rapid destruction of the gamma isomer, and a large chloride increase. Over certain ranges, the rate of depletion was related to both temperature and dung concentration. When suspensions of BHC and dung were adjusted to a number of different pH values and stored, no decrease in gamma isomer concentration occurred in those below pH 5. The addition of certain chemicals also reduced the rate of depletion, and in most cases this was associated with a lowering of the pH. This finding suggests a practical method of preventing depletion of gamma-BHC in cattle-dipping vats.
The incidence of apatite-solubilizing organisms in the rhizosphere and soil
Authors: Sperber JI
Published: November 2004

A number of microorganisms capable of solubilizing apatite mere isolated from soil and from the rhizosphere of plants. Many genera of common soil fungi and bacteria were represented. The organis~ns solubilizing apatite were consistently present in higher proportions in rhizosphere isolates than in those from nearby soil. The zone of solution of apatite surrounding colonies on agar plates was usually characteristic of organisms producing acid in liquid culture; however, the degree of solubilization was not proportional to the fall in pH. On subculturing, many isolates rapidly and irreversibly lost their ability to dissolve apatite. Soil isolates lost their ability to solubilize apatite more readily than isolates from the rhizosphere.
Solution of apatite by soil microorganisms producing organic acids
Authors: Sperber JI
Published: November 2004

The solution of phosphate by soil microorganisms producing organic acids was studied in pure culture. Two fungi, an actinomycete, and two bacteria solubilized apatite by formation of acid end-products from carbohydrates. The principal acids produced were lactic, glycollic, citric, and succinic acids. Chemical solutions of the first three of these hydroxy-acids alone solubilized apatite. In the presence of calcium carbonate less phosphate was brought into solution.
Single crossing between White Leghorn and Australorp
Authors: Morris JA , Skaller F
Published: November 2004

Egg production and related data are presented for 1520 pullets resulting from nine generations of single crossing between White Leghorns and Australorps. Both types of reciprocal crosses were consistently superior to the better of the parental breeds (White Leghorn) in hatchability, chick viability, and egg production. This superiority became still more apparent when pure and crossbred half-sisters were compared. Crossbreeding was not effective in improving the viability of adult birds or the body weight, the latter remaining intermediate between that of the two pure breeds. The number of days required to reach sexual maturity was decreased as a result of crossbreeding. The crossbreds showed less variation in egg production and included in their sample a much smaller percentage of extremely low-producing pullets. A comparison between the two types of crossbreds shoved differences in individual years, but when viewed over the whole period of the experiment the only consistent differences were the superior hatchability and higher fertility, under artificial insemination conditions, when the White Leghorn served as the dam. There were no significant differences in production characters between the two types of crossbreds when housed on deep litter.
Estimation of the trace element status of large areas of soil
Authors: Oertel AC
Published: November 2004

An account of a method for estimating the trace element status of a large area, from analytical results for a small number of samples, is followed by an example of its application to some South Australian soils.
Soil sulphur fractions as chemical indices of available sulphur in some Australian soils
Authors: Williams CH , Steinbergs A
Published: November 2004

A range of soils from eastern Australia hare been examined for a number of fractions of soil sulphur. These have been compared with plant sulphur uptake and yield of oats grown in pot culture in order to assess their possible values as indices of available sulphur. In all of the soils examined, most of the sulphur was present in organic forms and in most cases at least 50 per cent. could be extracted by 0.1N sodium hydroxide. Similar amounts were released as sulphate by ignition of the soil and similar amounts were also estimated by a reduction method. These three fractions were highly correlated with one another and with the total sulphur, but each was poorly correlated with the sulphur uptake and yield of oats in pot culture experiments. The results indicated that an appreciable proportion of the soil sulphur may consist of organic sulphates. The amounts of free water-soluble sulphate were small and were unsatisfactory as indices of yield. In addition to free sulphate, aqueous extracts also contained some organic sulphur which was easily oxidized to free sulphate by dilute hydrogen peroxide. The amount of water-soluble sulphur could be substantially increased by heating the soil prior to extraction. The fraction of the soil sulphur which was extracted after heating with water on a boiling water-bath, followed by heating for 1 hr in a hot-air oven (heat-soluble sulphur), was found to be highly correlated with both sulphur uptake and yield of oats grown in pot culture. It seems likely that this heat-soluble fraction ma3 provide a satisfactory index of available sulphur.
Studies on the reactions of animals to infestation with ticks. V. Laboratory animals as hosts for the cattle tick, Boophilus microplus (Canestrini)
Authors: Riek RF
Published: November 2004

When an Elizabethan collar was fitted to prevent the animal from biting and scratching, successful development of the cattle tick, Boophilus microplus, was obtained on the white mouse and rabbit, but not on the guinea-pig. Development on mice was little slower than on cattle, but mortality was high, and replete females were less than half the normal weight. There was an inconstant, round-cell reaction to attachment of larvae, but a more acute, polymorphonuclear response to nymphs and adults, and a tendency to wall of I the haustellum of the tick by ingrowing epithelium or inflammatory tissue.
Nitrite production by a thermophilic bacterium
Authors: Sims CM , Collins FM
Published: November 2004

Attempts to isolate thermophilic nitrifiers from two central Australian desert soils and two hot-house soils were unsuccessful. A suspected nitrifier isolated from garden compost was identified as B. stearothermophilus, and was later shown to have no nitrifying ability, but produced nitrite by the reduction of nitrate present in the compost.
Adrenal cortical activity in sheep as measured by urinary 17-ketogenic steroid excretion
Authors: Robinson KW , Morris LR
Published: November 2004

The effects of a number of stimuli on adrenal activity in sheep were assessed from measurements of the output of urinary 17-ketogenic steroids (17-KGS). Evidence for the claim that 17-KGS excretion in sheep reflects adrenal cortical activity was provided by observations that injections of ACTH produced a marked rise in concentration of these steroid metabolites in the urine. A seasonal rhythm in the urinary excretion of 17-KGS was observed. The peak winter output of these steroids was eight times that found in midsummer. This pattern of adrenal activity appears to be temperature- and not light-induced. In the pregnant ewe, the urinary 17-KGS output followed normal seasonal fluctuations over the greater part of gestation. However, a sudden drop in values occurred during the 2 weeks prior to lambing. This was followed by a progressive rise post partum which was dependent on active lactation. The pre-partum fall in steroid excretion was also observed in pregnant ewes undergoing daily ACTH therapy. The significance of these findings is discussed. Pregnancy appears to modify the response of sheep to repeated intramuscular injections of ACTH. The steroid excretion rate was related to the dosage level of ACTH in both pregnant and non-pregnant ewes although gestation markedly reduced the total output. There was no evidence of adrenal atrophy with repeated cortisone injections over 8 weeks, but endogenous ACTH release appeared to be delayed when daily ACTH injections were discontinued. Injections of 300 mg cortisone acetate and 50 i.u. of ACTH, over a period, gave comparable excretion rates of 17-KGS in non-pregnant ewes.
The effects of varying the nitrogen, sulphur, and phosphorus content of organic matter on its decomposition
Authors: Barrow NJ
Published: November 2004

The decomposition of a mixture of organic compounds was studied by measuring the evolution of carbon dioxide, and changes in the concentration of ammonium, sulphate, and phosphate. In one experiment the nitrogen supply was varied by varying the proportion of glycine in the mixture of organic compounds; in another the sulphur supply was varied by varying the proportion of cysteine; and in a third the phosphorus supply was varied by varying the proportion of sodium ß-glycerophosphate. Mineralization of an element depended on the concentration of that element in the organic mixture. Mineralization of nitrogen did not occur until respiration had lowered the carbon/nitrogen ratio to about 5 and mineralization of sulphur did not occur until respiration had lowered the carbon/sulphur ratio to about 50. On the other hand mineralization of phosphorus occurred before the carbon/phosphorus ratio had been reduced to any consistent figure. This may not be a characteristic of phosphorus mineralization but may have been caused by suboptimal supply of nitrogen. Mineralization of an element also depended on the concentration of other elements and, in general, reduced supplies of one element caused increased mineralization of others.
The rates of production of volatile fatty acids in the rumen
Authors: Gray FV , Jones GB , Pilgrim AF
Published: November 2004

The rates of production of acetic, propionic, and butyric acids in the normal rumen of a sheep have been measured from the decline in specific activity of these acids in the rumen after introduction of their sodium salts, labelled with 14C. Polyethylene glycol was introduced into the rumen to permit measurement of the rumen volume. The rates of production were: acetic acid 99 m-moles/hr, propionic 44 m-moles/hr, and butyric 21 m-moles/hr.
Serological studies of the self-cure reaction in sheep infected with Haemonchus contortus
Authors: Soulsby EJL , Stewart DF
Published: November 2004

The serological reactions which take place during self-cure of sheep infected with Haemonchus contortus were investigated by complement fixation, haemagglutination, and the Ouchterlony agar diffusion precipitin techniques. In addition, a test to detect incomplete antibodies was applied to certain sera. Absorption tests demonstrated that the antibodies detected by the complement fixation test and the haemagglutination test could be differentiated. Evidence is presented to show that the main antigenic stimulation at self-cure is derived from substances released by larvae during the third ecdysis.
The synthesis of vitamins in the rumen of sheep. II. Levels of thiamine, riboflavin, and nicotinic acid in the rumen of grazing lambs
Authors: Buziassy C , Tribe DE
Published: November 2004

The thiamine, riboflavin, and nicotinic acid levels were measured in ewes' milk and herbage, and in the rumen contents of young lambs being reared on these foods. The vitamin levels in the rumen contents increased sharply during the first 3 weeks of the lamb's life but thereafter showed no change with age up to 9½ weeks of age. The lambs were weaned at 8 weeks of age, and after weaning there was less variability in the rumen levels of all vitamins, and the levels of nicotinic acid were lower than before. The possible significance of these observations in relation to the existence of microbial synthesis of vitamins in the rumens of suckling lambs is discussed.
The effects of a number of management practices on chiller beef production in Victoria
Authors: Robinson TJ , Cameron NG
Published: November 2004

Data are presented from a detailed factorial experiment conducted on a private property in the Western District of Victoria and involving 72 grade Aberdeen Angus cattle and their dams. The relative contribution to daily liveweight increase and economy of production of sex (steer v. spayed heifer), sire (stud v. grade bull), level of supplementary feeding (high v. moderate v. low), season of birth (autumn v. spring), and year of birth (1954 v. 1955 control v. 1955 stilboestrol-implanted) was determined. Season of birth (autumn>>spring, P < 0.001) was easily the greatest single factor affecting daily liveweight gain, carcass beef production per week, and cash value of beef produced per week, followed in order of importance by sex (steers>>heifers, P < 0.001), and level of supplementary feeding (high >moderate = low, P<0 .001). Quality of the sire had no demonstrable effect on any factor studied. Year of birth slightly affected cash value of beef produced per week (P<0.05), but only because of yearly price fluctuations. Interactions between the main variates were relatively unimportant, but the spring-born calf was much more dependent on heavy supplementary feeding than was the autumn-born. Economy of production was dependent on calving at the correct time (autumn) and the reduction of supplementary feeding to a minimum. The value of the factorial experimental design for field studies of this type is briefly discussed.
The influence of environment on seed production capacity in white clover (Trifolium repens L.). I. Controlled environment studies
Authors: Thomas RG
Published: November 2004

Ramets of New Zealand Government Stock white clover (Trifolium repens L.) were grown in all combinations of 18-, 14-, and 10-hr photoperiods at constant temperatures of 10, 20, and 30°C. Inflorescence initiation, inflorescence height, number of florets per inflorescence, floret size, ovule number, and pollen fertility were all strongly influenced by environment. Greatest inflorescence initiation occurred in long days at high temperatures, in which conditions, also, the ratio of peduncle to petiole length was highest. Long days and low temperatures led to maximal floret number per inflorescence, floret size, and ovule number per floret. Pollen sterility, as measured by percentage of aborted grains, was little affected by day length but a high level of sterility was induced by growth at 10°C. The relative importance of these factors and the interactions between them in determining seed production capacity are discussed.
A test of kidney and liver function in wethers
Authors: Setchell BP , Blanch E
Published: November 2004

Para-aminohippurate (PAH) and para-aminobenzoate (PAB) are estimated in plasma and urine from wethers after a subcutaneous injection of PAB. The rate of synthesis of PAH from injected PL4B is taken as a measure of liver function and the rate of urinary excretion of the synthesized PAH as a measure of kidney function. It is shown that extrahepatic synthesis of PAH from PAB is unlikely to interfere with these tests of function. Some values for normal animals are given.
The influence of defoliation on the components of seed yield in swards of subterranean clover (Trifolium subterranean L.)
Authors: Rossiter RC
Published: November 2004

Six defoliation treatments were imposed on two strains of subterranean clover (Dwalganup and Yarloop) grown in dense swards. Seed yield (weight per unit area) was increased by 27% over controls by July, or July plus early September, defoliations. With progressively later defoliation, yields fell to the control level, then to 15% below it. The number of seeds per unit area showed an increase of almost 40% with early defoliation, whereas with later defoliation the numbers fell to the control level. The increase was due primarily to larger numbers of inflorescences per unit area and a greater proportion of buried burrs. Supplementary data from grazed swards confirmed the promotive effect of early defoliation on seed production. The promotive and detrimental effects of defoliation are discussed, and brief consideration is given to practical implications.
Water and electrolyte changes in tropical Merino sheep exposed to dehydration during summer
Authors: Macfarlane WV , Morris RJH , Howard B , McDonald J , Budtz-Olsen OE
Published: November 2004

During three summers field studies were made of Merino wethers deprived of water while exposed to sun and to maximum air temperatures ranging from 84°F (29°C) to 10S°F (42°C) at Julia Creek, lat. 21° S. Evaporative cooling determined the rate and extent of water and electrolyte changes and produced a different pattern each year. Control of body temperature failed when 31% of body weight was lost by the end of 10 days without water. In hotter weather 5 days without water caused a 25% loss of body weight and in some sheep irreversible circulatory failure. In the course of dehydration, after an initial increase, the plasma and extracellular volume decreased up to 45% while concentrations of haemoglobin and plasma protein increased by 60%. In the plasma, potassium and sodium concentration increased less than that of haemoglobin. When 25% or more of weight was lost, plasma urea concentration rose to 136 mg/100 ml. Plasma osmolarity in some sheep reached 490 m-osmoles/l after 10 days. Urine volume fell after 2 days without water, and in a hot season less than 100 ml/24 hr was passed on the fourth or subsequent days. Concentrations increased over the first 4 or 5 days, reaching a maximum of 3.8 osmoles/l, then declined. Between half and two-thirds of the osmolarity was accountable to sodium and potassium salts. In rapid dehydration, more sodium was excreted than potassium. There was reduced sodium excretion when water was ingested after dehydration. Renal function studies in ewes indicated that filtration, renal plasma flow, and glucose reabsorption were reduced to half after 5 days without water in the heat. The chance of survival in dehydration appears to be increased by low rates of water loss in the first 3 days, together with high sodium and low potassium excretion. A full rumen, containing water up to 13% of body weight, could provide all the extracellular fluid loss. More than half of the weight loss appears, however, to come from intracellular sources. Extracellular fluid was drawn upon to a greater extent when the rate of dehydration was rapid, than in the cooler periods of slow weight loss. Survival in the sun without water depends upon insulation, water conservation, water reserves in rumen and extracellular fluid, the ability to adjust electrolyte concentrations, and the ability to maintain circulation with lowered plasma volume.
Temperature regulation in the new-born lamb. II. A climatic respiration chamber for the study of thermoregulation, with an appendix on a correction for leaks and imperfect measurement of temperature and pressure in closed circuit respiration chambers
Authors: Alexander G
Published: November 2004

A closed circuit respiration chamber is described, for the estimation of heat production of newly born lambs by indirect calorimetry. Heat production can be measured to an accuracy of 0. 68 kcal (S.D.) under various combinations of temperature (from -10 to +50°C), humidity, wind (up to 550 cm/sec), and wetness of the fleece. The standard deviation of measurement of water evaporated was 0.50–0.75 g. A correction for leaks and imperfect measurement of temperature and pressure, in closed circuit respiration chambers, is described in the Appendix.
Temperature regulation in the new-born lamb. III. Effect of environmental temperature on metabolic rate body temperatures, and respiratory quotient
Authors: Alexander G
Published: November 2004

Studies were made on temperature regulation of lambs in a closed circuit indirect calorimeter. Dry new-born lambs were able to maintain normal body temperature in ambient temperatures as low as -5°C. This was accomplished by increasing heat production to 2–3 times "basal" levels, apparently by increased oxidation of fats, and by reducing heat loss through the extremities by vasoconstriction. The lower limit of the zone of thermal neutrality was about 29°C. In unsuckled lambs within 24 hr of birth, the heat produced in response to cold appeared to be independent of pre-natal nutrition and age. It was considerably lower in lambs with hairy coats than in lambs with fine coats. Milk intake increased heat production, and this increase was abolished after 12 hr of fasting in lambs up to 3 days old, but the increase persisted in older lambs. The increase was accompanied by, and was apparently due to, elevated heat loss from the extremities, which persisted even at low temperatures. The maximal thermal insulation of the tissues, calculated from these results, was about 1 Clo; that of the fleece plus air was only 1 to 2 Clo.
Parasitic gastro-enteritis of cattle: The distribution and survival of infective strongyle on pasture
Authors: Durie PH
Published: November 2004

Observations are reported on the behaviour and longevity of infective cattle strongyle larvae in faecal pats and on pasture in south-eastern Queensland. Environmental conditions within the pat were favourable for the development of infective larvae at all seasons of the year except midsummer and midwinter. Larvae were distributed for the most part either in the pat or on pasture vegetation. Larvae migrated laterally from the pat for distances up to at least 3 ft, but usually not more than 1 ft, and these movements occurred only after suitable rain. At no time was a single mass movement of all larvae in the pat observed. If rainfall was continuous, migration was continuous, and when rainfall was alternated with periods of dryness, migration occurred in waves. Pats exposed in the summer remained a source of larvae for 5 months. This period was extended to 7–8 months with pats exposed in the winter. Larvae survived on pasture for up to 6 and 8 weeks respectively for these seasons of the year. Vertical migration on pasture was also observed.
Comparison of the effects of the physical and chemical components of soil water energy on seed germination
Authors: Collis-George N , Sands JE
Published: November 2004

The components of total soil moisture energy of consequence to a biological system are matric potential and osmotic potential. An experimental procedure, which allows the effects of the potentials to be considered independently, is described and discussed. Germination behaviour does not support the hypothesis that matric and osmotic potentials should have similar biological consequences because their free energy measurements are identical. The results support a diffusion phenomenon hypothesis with movement of solute from the soil solution through the cell membranes, so that any biological consequence is that of an internal "toxicity" rather than an osmotic "drought". For some osmotic systems, 100 cm of matric potential is as effective as 10 000 cm of osmotic potential in retarding seed germination rates.
Effects of pasture maturity on the diet of sheep
Authors: Arnold GW
Published: November 2004

This paper compares the changes from early spring to summer in the digestibility of the diet of sheep grazing on phalaris -subterranean clover pasture, with changes over the same period of a similar pasture cut. and fed to sheep in pens. Data from a continuous digestibility trial in pens between September and December 1958 showed that the voluntary dry matter intake of sheep was restricted when the dry matter content of the pasture was below about 25%. From an early vegetative stage of growth through to early flowering of the phalaris, the organic matter digestibility of the whole pasture declined only from 79 to 76%. The diet selected by grazing sheep did not decline in digestibility, as measured by a faecal nitrogen index method, until 2 or 3 weeks after the decline in the whole pasture. With flowering and senescence of the pasture, the organic matter digestibility declined rapidly to 53%. Factors influencing this marked decline are discussed.
Breeding for creeping root in lucerne (Medicago sativa L.). I. The inital response to selection
Authors: Daday H
Published: November 2004

A lucerne-breeding programme was initiated in Canberra to combine the creeping-rooted habit of the variety Rambler with the summer and winter vigour of the varieties Hunter River, Hairy Peruvian, and African. The incidence of creeping-rooted plants in the "F1" generation was only 5%, which indicated marked non-additive gene effects concerned with the expression of the character. An "F2" generation, formed by interbreeding creeping plants from the "F1", showed only 6% of creeping individuals. Selection and recombination of the available creepers resulted in an average of 41% creeping-rooted plants in the "F3" families, with a range between families from 0 to 81%. In the "F2" generation approximately 50% of the phenotypic variance for creeping root was found to be additive genetic, and the response to selection was high. However, the persistence of non-additive genetic effects was indicated by a statistical analysis of the '"F3" generation. The genotypic correlation coefficients between creeping and summer forage scores, and creeping and winter forage scores, were –0.09 and 0.59 respectively, and that between summer and winter forage scores was 0.48. Thus an association between creeping rootedness and plant vigour is possible. For Rambler, both the incidence and degree of creep were found to be intensified by short days and low temperature, but this effect was not so apparent in the breeding material used in this study.
Synchronization of oestrus in sheep by orally active progesterone derivative
Authors: Southcott WH , Braden AWH , Moule GR
Published: November 2004

In a preliminary experiment with 40 Merino ewes of 45 kg liveweight, oral doses of 0, 6.6, 20, and 60 mg 6-methyl-17-acetoxyprogesterone were administered daily for 14 days. The highest dose level completely prevented oestrus during treatment, and all 10 ewes came into oestrus during the 5-day period beginning 24 hr after the last dose; seven of the 10 ewes conceived and lambed. Daily doses of 6.6 and 20 mg reduced the incidence of oestrus during treatment, but produced little synchronization subsequently. In the main experiment 77 similar ewes were treated over 17 days with either 6-methyl-17-acetoxyprogesterone (50 mg orally per day, 39 ewes), or progesterone (10 mg in oil intramuscularly every second day, 38 ewes). There were 19 untreated ewes. Some ewes from each group were marked by rams during the treatment period. In the 6 days following the final dose of progestagen 75% of ewes were marked by rams, with a peak on the third day. There was no difference between treatments. The proportion of ewes that lambed following mating in the 6 days after cessation of treatment was 15/29 and 11/29 for 6-methyl-17-acetoxyprogesterone and progesterone treatments respectively. In the main experiment half the ewes were injected with pregnant mare serum gonadotrophin 24 hr after the last dose of progestagen, and 24 hr later, with human ohorionic gonadotrophin. This supplementary treatment did not further reduce inter-animal variation in time of onset of oestrus, but tended to reduce the proportion of ewes exhibiting oestrus.
Studies on the carbohydrate metabolism of sheep. XIX. The metabolism of glucose, free fatty acids, and ketones after feeding and during fasting or undernourishment of non-pregnant, pregnant, and lactating ewes
Authors: Reid RL , Hinks NT
Published: November 2004

Average plasma free fatty acid (FFA) values in non-pregnant sheep in widely differing body condition, but fed at levels of maintenance or above, varied from 0.24 to 0.39 m-equiv.11. Values declined after feeding, while blood ketone levels increased. Plasma FFA value is a sensitive indicator of undernourishment in sheep; a pronounced and immediate increase followed a 40% reduction in ration. FFA and ketone levels increased during 7 days of fasting, the former markedly and to a degree depending on blood glucose level; there was a close inverse correlation between plasma FFA and blood glucose levels. Similar correlations were recorded in undernourished pregnant and lactating ewes, although FFA values were consistently higher in lactation at all blood glucose levels. Ketone levels were linearly related to FFA levels when blood glucose values exceeded 25–30 mg %. Below this level of glucose there was no further increase in FFA, but ketones increased markedly. Caloric homeostasis is relatively easily maintained in undernourished nonpregnant and lactating sheep. The undernourished pregnant ewe is susceptible to hypoglycaemia, and it is suggested that there is a critical blood glucose level of 25–30 mg % below which caloric homeostasis becomes more difficult to maintain, because of endocrine changes which markedly affect the normal pattern of fat metabolism.
The effects of urea supplements on the utilization of straw plus molasses diets by sheep
Authors: Coombe JB , Tribe DE
Published: November 2004

Three experiments with sheep were carried out to investigate the effect of urea, added to a diet of straw plus molasses, on roughage intake and digestion, and on the nitrogen status of the animal. Urea, added to straw and molasses at the level of 3% of the amount of straw, increased the ad libitum food intake, rate of cellulose (cotton thread) digestion in the rumen, and rate of passage of food through the gut. When different amounts of urea were fed, the highest levels of intake, rate of cellulose digestion, and rate of passage occurred with 8–16 g urea per sheep per day. Increasing the amount of urea fed to 32 g per day caused significant decreases in rate of passage and intake, within diets containing urea. These were not accompanied by significant changes in rate of cellulose digestion in the rumen. With diets of straw and molasses, with and without urea, crude fibre digestibility was positively correlated with the rate of cellulose digestion in the rumen. Voluntary intake of these diets was positively correlated with rate of passage. When the effect of rate of passage was eliminated, voluntary intake was not significantly correlated with the rate of cellulose digestion in the rumen. Under the feeding conditions used in these experiments, once sufficient urea had been added to the diet to bring the animal into a small, positive nitrogen balance, additional dietary nitrogen supplied as urea was practically all excreted in the urine. It is concluded that, under these feeding conditions, the primary function of a urea supplement is to enable an animal to maintain nitrogen equilibrium rather than store significant amounts of nitrogen in the body.
The influence of carbon dioxide on the growth and sporulation of Dermatophilus dermatonomus
Authors: Roberts DS
Published: November 2004

In cultures of Dermatophilus dermatonomus the provision of carbon dioxide (CO2) stimulated the germination and budding of zoospores and subsequent hyphal growth, but inhibited hyphal division and the production of zoospores. Similar effects, associated with the restriction of aeration in closed cultures, were found to be due to the accumulation of endogenous CO2 and not to oxygen limitation. Sporulating cultures produced about 0.5 ml CO2/ml broth medium during agitation for 18 hr at 27°C. Rapid removal of the endogenous CO2 promoted early abundant sporulation, especially when the oxygen content of the gaseous environment was reduced to about 10%. Observations on mycelial growth in cultures suggested that hyphae would not penetrate through the medium or grow into an atmosphere unless CO2 was present. CO2 in the sheep's skin thus seems likely not only to stimulate the germination of D. dermatonomus zoospores on the skin surface but to favour the subsequent hyphal invasion of the skin. Sporulation of the hyphae is probably influenced by changes in the CO2 production of infected tissue cells, and by differences in the rate of CO2 diffusion from different depths in the lesion.
The effect of saline water on kidney tubular function and electrolyte excretion in sheep
Authors: Potter BJ
Published: November 2004

The function of the kidney tubules of sheep which, for periods of 6 months or more, have been confined solely to saline water (1.3% sodium chloride) for drinking, has been compared with that of sheep on identical fodder but receiving drinking water with a low salt content (rain-water). As no consistent difference was observed between the maximal rates of excretion and reabsorption in the kidneys of the two groups, it is probable that prolonged ingestion of sodium chloride by the sheep does not induce an increase in the number of active tubules in its kidneys. The sodium content of the plasma remained unchanged, but slight increases in potassium and chloride were observed in the plasma of those sheep confined to saline water. Urinary excretion of sodium and chloride was greatly increased, and potassium to a lesser extent. Reabsorption of each of these electrolytes, after filtration at the glomerulus, was found to be reduced during transit through the renal tubules. In the sheep which drank saline water, urinary pH was increased and osmolarity reduced. Clearance of total free water, however, was negative, and the osmotic concentration of body fluids was maintained by the production and excretion of urine which was hyperosmotic with blood plasma. The findings illuminate the manner in which renal adjustments assist the sheep to tolerate water relatively high in salt.
Studies on resistance in calves to experimental infection with the nodular worm, Oesophagostomum radiatum (Rudolphi 1803). II. The role of the respective stages of the parasitic life cycle in the stimulation of resistance
Authors: Roberts FHS , Riek RF , Keith RK
Published: November 2004

Investigations are reported which attempted to define the role of the respective stages of the parasitic life cycle ofOesophagostomum radiatum in the stimulation of resistance in calves to reinfection with this parasite. In one series of experiments with calves reared worm-free, infection was restricted to known stages by treatment with an anthelmintic, and in another series by surgical implants of worms. Subsequent reinfection showed that the early development stages of the parasite up to the early fourth stage larva in the gut lumen, and the exsheathing fluid released at the third and fourth ecdyses, were not essential for the stimulation of resistance. The results also suggest that ability to stimulate resistance increases as the worms mature.
The effect of diet on the secretion of parotid saliva by sheep. III. Observations of the secretion of saliva by grazing sheep
Authors: Wilson AD
Published: November 2004

The parotid saliva secreted by three grazing sheep was recorded by exteriorizing and cannulating one parotid duct of each sheep, and collecting the saliva into carts that were harnessed to the sheep. The sheep were grazed on an annual pasture in a Mediterranean climate and collections were made during spring, summer, autumn, and winter. In each season, recordings were also made of the pasture intake, pasture availability, and the behaviour of the grazing sheep. The mean daily secretion of saliva from one gland was 3.42 l. in autumn, 4.05 l. in winter, 6.69 l. in spring, and 4.07 l. in summer. In spring, the mean secretion from one sheep was 7.92 l./day. The changes in secretion did not appear to be related to the pasture intake, or to the grazing behaviour of the sheep.
The effect of phosphate supply on the growth and botanical composition of annual type pasture
Authors: Rossiter RC
Published: November 2004

The results of two long-term field experiments and two 1-year experiments are reported. In three of these, severe phosphate deficiency was present initially. At high phosphate supply, the annual total yield was not significantly related to age of pasture over periods of 10–13 years. At intermediate and low supply, yields relative to high phosphate supply increased significantly with time; these increases are believed to demonstrate residual effects of phosphate. Indirect evidence for nitrogen accretion from clover under severely phosphate-deficient conditions is presented. Sward components—in the long term—responded differentially to phosphate supply. With very low phosphate, erodium (Erodium botrys (Cav.) Bertol.) and flatweed (Hypochoeris glabra L.) were dominant; whereas with high phosphate, cape-weed (Cryptostemma calendula (L.) Druce) and ripgut brome grass (Bromus rigidus Roth)—or else barley grass (Hordeum leporinum Link)—were dominant. Subterranean clover (Trifolium subterraneum L.), though present under these extremes, was relatively more plentiful at intermediate levels of supply. However, at "steady state" conditions, the range in clover content was fairly narrow (from c. 20 to 40%). The significance of these findings to a sheep infertility problem ("clover disease") of subterranean clover-dominant pastures is discussed.
Energy exchanges of pregnant and lactating ewes
Authors: McCGraham N
Published: November 2004

At intervals throughout gestation, the energy, carbon, and nitrogen exchanges of four Merino ewes were determined with the aid of closed-circuit indirect calorimetry. Six similar but non-pregnant animals were studied at the same time. The food consisted of equal parts of lucerne and wheaten hay; half the sheep in each group were given a constant 600 g/day and half 900 g/day, and the non-pregnant ewes were fasted on one occasion. Free fatty acids, glucose, and ketones in the blood were also determined during the final stages of pregnancy. Balance measurements were continued during lactation, the ewes being given 1200 g food/day for the first month and 900 g for the second. The digestibility of the food was not affected by pregnancy or lactation, but urinary nitrogen loss decreased as pregnancy advanced and was least during lactation. Although a constant amount of food was eaten, the heat production of each pregnant animal increased throughout gestation. The heat increment of pregnancy at term was 90 kca1/24 hr/kg foetal tissue. The most direct measurements of oxygen uptake by the foetus in utero indicate much lower levels of heat production per kilogram of tissue; it is concluded that these are underestimates. The metabolic rate was unusually high immediately before parturition, and in two cases decreased to near non-pregnant levels 24 hr after lambing. The total energy retention of the ewes became smaller as pregnancy advanced, and in two cases was negative at term. Metabolizable energy was used for reproduction with a gross efficiency of 15–22% and a net efficiency of 13%. The metabolizable energy used per kilogram of foetus was approximately 10% of the maintenance requirement of the ewe herself. Daily energy utilization by the conceptus at term probably accounted for 70% of the glucogenic substances available from the food. There was no evidence of increased gluconeogenesis from protein by the pregnant ewe. The nutrition of the ewe during gestation affected lactation mainly in the first week or two. The data indicate that nitrogen intake rather than energy intake limited milk production. Irrespective of the amount of energy in the milk, the heat increment due to feeding was 20% smaller for lactating than for dry fatteningewes. It is suggested that efficient use of acetate by the mammary gland permits more efficient lipogenesis by other tissues.
The renal response of sheep to feeding
Authors: Stacy BD , Brook AH
Published: November 2004

Acute changes in renal excretion occurred when pen-fed sheep were given their daily feed. There was a reduction in the rate of urine flow and the concentration of the urine increased. During the oliguric phase, sodium and potassium excretion decreased whereas hydrogen ion excretion increased and caused acidification (pH 5–6) of the normally alkaline urine (pH 7–8). Renal clearances of inulin and PAH did not indicate that the urinary changes were due to altered renal haemodynamics. It is suggested that the observed renal response was a reflection of the sudden shift of extracellular fluid into the gut at the onset of feeding.
The influence of subterranean clover pastures on soil fertility. II. The effects of certain management systems
Authors: Watson ER , Lapins P
Published: November 2004

Three systems of pasture management were examined to assess the role of clover herbage in the build-up of soil fertility. In one system herbage was returned to the soil via the grazing animal as dung and urine; in another it was returned as dried plant material; and in the third it was discarded. The rate of accumulation of soil nitrogen (72 lb/acre/annum) was not significantly affected by treatment. Moreover, four consecutive cereal crops which followed the clover ley showed no significant differential effects of the management systems on total yield, grain yield, or nitrogen uptake. Nitrogen loss from the excreta and from returned herbage, and reduced nitrogen fixation due to the return of nitrogen in the excreta and herbage, were considered to be the factors mainly responsible for the absence of differential treatment effects. The indispensability of the grazing animal for the maintenance or build-up of soil fertility is questioned.
Utilization by fattening sheep of the energy and nitrogen in fresh herbage and in hay made from it
Authors: McCGraham N
Published: November 2004

Balances of energy, carbon, and nitrogen were measured with fresh herbage cut at 28 days' regrowth, and with hay made from it. Measurements were made on four wether sheep at fasting and at four levels of feeding. The herbage contained paspalum grass and white clover in proportions ranging from 0.6 : 1 to 1.2 : 1, with dry matter between 11 and 17%. It contained (dry matter basis) : 10% ash, 3% soluble sugars, 25% cellulose, 23% crude protein, and 9% lignin; crude fibre was 22% and nitrogen-free extractives 42%. The hay had the same composition. Digestibility of organic matter was 75% for the fresh material and 73% for the hay; digestible energy values were 73 and 70% respectively. The difference between fresh herbage and hay was due entirely to a decrease in the digestibility of protein, from 82% to 73%, in drying. Efficiency of utilization of digested protein was not affected. Digestibility of both materials decreased by 2 to 4 units between the lowest and highest feeding levels. One other difference was found, viz. the ratio methane production/kcal digestible energy was 1–2% greater with the hay. Metabolizable energy was 82–84% of digestible energy for both materials. Heat production bore a linear relation to metabolizable energy above maintenance. Net availability of metabolizable energy was 75% between fasting and maintenance, and 52% above maintenance, for both the fresh and dry food. These quantities were predictable to within 8% from metabolizable energy or fibre digestibility; the normally used starch equivalent factors underestimated the correct values by some 25%.
Sweating rates of cattle in the field and their reaction to diurnal and seasonal changes
Authors: Schleger AV , Turner HG
Published: November 2004

Twenty-six replicate observations of sweating rate were made on six Hereford x Shorthorn and six Brahman x Shorthorn steers in the field at different times of day and different seasons. Sweating rates were lower in Brahman cross than in Hereford x Shorthorn steers under mild conditions, but higher under stressful conditions. Brahman cross steers increased sweating rate at lower skin and rectal temperatures. Maximum sweating rates were significantly lower in winter than in summer. This is ascribed to an association between sweating function and other aspects of skin function which undergo seasonal changes. Under cool conditions, either there was no consistent difference between animals in sweating rate as in the Brahman cross steers, or the less heat-tolerant animals with higher body temperatures and thicker coat type showed the higher sweating rates. Under challenging conditions of heat, between-animal differences in sweating capacity were revealed and, in the British steers, animals with higher sweating rates then had lower body temperatures. Furthermore, animals with sleek coats showed a higher sweating capacity despite lower thermal stimulus to the skin. The environmental conditions under which sweating capacity is challenged, when differences between animals become important as a component of heat tolerance, depend upon genotype, season, and duration of heat stress.