1. An experiment was carried out from 1 August 1953 to 31 July 1955 to compare strip grazing with rotational grazing on the basis of the total animal production obtained from dairy cattle on irrigated pasture.

2. The same overall stocking rate was used for both treatments. Herbage surplus to grazing requirements at any time was conserved as hay and fed back to the appropriate group of cows at the end of the grazing season.

3. The aim was to manage the area under each technique as efficiently as the technique permitted.

4. The average production from the rotationally grazed group during the main pasture season of 260 days was 8740 lb. milk per acre (including 354 lb. of butterfatand 766 lb. of solids-not-fat) and from the strip-grazed group 8867 lb. milk per acre (including 358 lb. of butterfat and 766 lb. of solidsnotfat).

The average weight of pasture nutrients utilized per annum by the rotationally grazed group was 5887 lb. starch equivalent per acre and by the stripgrazed group 5896 lb. starch equivalent per acre.

None of the treatment differences in animal production was significant.

5. The differences between the results of this experiment and those obtained by other workers are discussed.

In the communication: ‘Studies of the skeleton of the sheep. III. The relationship between phosphorus intake and resorption and repair of the skeleton in pregnancy and lactation’, D. Benzie, A. W. Boyne, A. C. Dalgarno, J. Duckworth & R. Hill, J. Agric. Sci. (1959), 52, 1–12, Plates 3 a and 3 b have been interchanged.

1. The ash content of the skeleton of Cheviot ewes fed a daily ration containing about 4·5 g. of phosphorus fell by 18·8% between mid-gestation and mid-lactation, and 2 months after the end of lactation the loss was fully replaced.

2. In ewes fed a daily ration containing about 1·5 g. of phosphorus the loss of skeletal ash was 39·9% at mid-lactation, and this was not replaced 2 months after the end of lactation. When the phosphorus intake was raised in mid-lactation from 1·5 to 4·5 g. repair was greater but was still not complete.

3. Resorption was greater in bones rich in cancellous tissue, such as the cervical vertebrae, than in those rich in compact tissue, such as the shafts of long bones, but when severe resorption took place significant losses were found in the shafts of long bones as well as in other bones.

4. Whole blood inorganic phosphorus values were very low, particularly during lactation, in ewes fed on the low-phosphorus ration. When extra phosphorus was fed from mid-lactation onwards blood phosphorus values rose to normal in less than four weeks, a much more rapid recovery than that which took place in the skeleton.

5. Resorption of the skeletons of ewes on both moderate and low-phosphorus rations could be detected using radiographs taken of the radius in the living animal at mid-lactation, and severe resorption found in ewes fed on the low-phosphorus ration could be distinguished readily from the milder resorption found in ewes fed on the moderate-phosphorus ration.

1. The effect of treating mineral soils with hydrofluoric acid to decompose clay minerals on the extraction of soil organic matter by alkaline and neutral reagents has been investigated.

2. It was found that treatment of soil with hydrofluoric acid had little effect on the extraction of organic matter by alkaline or neutral reagents, but that it released considerable amounts of ammonium and organic matter. More than 90% of the nitrogen in Rothamsted soils was dissolved by repeated treatments with dilute solutions of hydrofluoric acid and sodium hydroxide.

3. It is shown that treatment of clay minerals with n-HF:n-HCl solution at room temperature for 24 hr. effects quantitative release of fixed ammonium from clay minerals and that similar treatment of soil is not likely to cause significant decomposition of organic nitrogen compounds to ammonium. It is suggested that a method based on this treatment may prove useful for the determination of fixed ammonium in soil. Results obtained by this method indicated that 4–8% of the nitrogen in surface soils and 19–45% of the nitrogen in subsoils examined was in the form of fixed ammonium.

4. It is concluded that some mineral soils contain a significant quantity of ammonium and organic matter intimately associated with clay minerals and that this clay-bound material is not dissolved by neutral and alkaline reagents used for the extraction of soil organic matter, but is released by hydrofluoric acid.

1. The energy exchange of two sheep closely clipped at weekly intervals was determined at three feeding levels and seven environmental temperatures, using a respiration apparatus in which radiant temperature was equal to ambient temperature. All measurements were made under conditions in which the animal was in equilibrium with its environment and heat storage was zero.

2. Body weight and fleece growth were both markedly reduced at the lowest feeding level. Weight losses were most marked at the lowest temperatures.

3. The energy lost in faeces decreased slightly as environmental temperature increased from 8 to 38° C. Urine energy losses also fell. Losses of energy as methane were maximal in the temperature range 23–28° C. As a result of these changes, the metabolizable energy of food increased with environmental temperature by 7 Cal./24 hr./° C.

4. The environmental temperature of the sheep at which their heat production was minimal, i.e. the ‘critical’ temperature was 39–40° C. for the lowest feeding level, 33° C. for the medium feeding level and 24–27° C. for the highest feeding level.

1. Pure swards of S. 48 timothy and S. 215 meadow fescue were cut (a) after ear emergence, (b) before ear emergence and in the aftermath to prevent flowering, and (c) every 4 weeks. The number and weight of tillers and leaves were determined.

2. Tiller numbers declined considerably from early spring to the middle of summer. This fall was reduced by a system of frequent defoliation in the wet summer of 1956, especially in timothy.

3. Leaf weight per unit area of sward increased rapidly from early spring until about the time of ear emergence; no further significant gains were recorded after ears had appeared, when the plots were cut for hay.

4. The weight per leaf also increased in the spring and was similar in both species. In the regrowth following a cut meadow fescue produced considerably heavier leaves than timothy.

5. As both grasses approached the flowering stage, their leaf canopy was increasingly raised above ground level. Variable proportions of foliage were thus removed by cutting according to the developmental stage of the plant. Crop growth rates following a cut appeared to be related to the amount of leaf material remaining in the sward.

6. Relative growth rates during uninterrupted growth were greatest around the time of ear emergence.

1. The heat emission of two closely clipped sheep was studied in forty experiments in which three feeding levels were employed and in which environmental temperatures ranged from 8 to 38° C.

2. The sheep shivered at temperatures below 23° C., but the first reaction to cold was a corrugation of the skin referable to contraction of the fascial muscles.

3. As environmental temperature increased voluntary water consumption and urinary volume increased markedly. Only a small degree of cooling resulted from this warming of large quantities of water through a relatively small temperature gradient.

4. The basal loss of heat by vaporization of water was 316 Cal./m.2/24 hr. in one sheep (3) and 307 Cal./ m.2/24 hr. in the other (23). Increased vaporization occurred at environmental temperatures of 31° C. for the experiments at the low-feeding level, 27° C. at the medium level and 26° C. at the high level. The water-vapour loss increased subsequently by 87 Cal./m.2/24 hr./° C. change in environmental temperature in sheep 3 and by 88 Cal./m.2/24 hr./° C. in sheep 23. Respiratory frequencies increased with increasing heat loss by vaporization. Some evidence suggests that when the water-vapour loss was high the excretion of potassium through the skin was increased.

1. A method of determining fixed ammonium in soil based on estimation of the difference in the amounts of ammonium released on treatment with N-HF:N-HC1 and with N-KCI has been investigated and compared with the hydrofluoric acid method of Rodrigues and the alkaline distillation method of Barshad.

2. Results obtained by the N-HF:N-HCl procedure with profile samples of various soils indicated that 3–8% (average, 5·6%) of the nitrogen in the surface soils and 9–44% (average, 21·5%) of the nitrogen in the subsoils examined was in the form of fixed ammonium. Rodrigues's method gave much higher values and Barshad's method gave much lower values.

3. Studies on the forms of nitrogen in soil profiles showed that the proportion of soil nitrogen released by acid hydrolysis as total-N and α-amino-N decreased with depth in the profile, whereas the proportion liberated as ammonium by acid hydrolysis increased with depth. They also showed that a considerable amount of the ammonium released by acid hydrolysis was derived from fixed ammonium in clay minerals.

4. It was found that the proportion of soil nitrogen dissolved by N-HF:N-HCl increased with depth in the profile, whereas the proportion dissolved by neutral and alkaline reagents used to extract soil organic matter decreased with depth. On the average, 23·2% of the nitrogen in the surface soils and 47·4% of the nitrogen in the subsoils was dissolved by a single treatment with N-HF:N-HCl at room temperature for 24 hr.

5. The reliability and significance of the results obtained by the N-HF:N-HCl method are discussed.

During the 12 months from September 1955 to August 1956, the reproductive tracts and ovaries of 4094 adult Merino ewes, recovered from the municipal abattoir at Pietermaritzburg, were examined. The great majority of the ewes had been consigned to the abattoir from one of three regions, between which differences in the nutritional value of the natural vegetation at different times of the year are recognized. From observations of the occurrence in the ovaries of active corpora lutea, it appeared that in some areas, mating Merino ewes during autumn and early winter is likely to result in the greatest percentage of ewes conceiving and in the highest lambing percentages. There was a suggestion, however, that in the more arid karoo areas, the percentage of ewes ovulating, as well as the mean ovulation rate per ewe, may remain relatively constant throughout the year. It seems likely that the low fertility of ewes of this breed may be due partly to the practice of introducing the rams into the flock at a time of year (spring and summer) in which many of the ewes are anoestrous, a practice which is often adopted in South Africa in order to avoid the poor growth rates which are known to occur among young lambs as a result of the high temperatures and the internal parasite infestations that are comcommon in the summer months. A need, in different areas, for extensive experimental evidence of the most suitable season for mating, is indicated.

No evidence of nutritional effects on fertility, either within or between areas, was obtained, but it is suggested that a higher proportion of ewes in certain areas may be capable of lambing in autumn as a result of more effective selection for this trait in these areas. There is also evidence that lack of fertilization of ova and early embryonic death may contribute significantly to the breed's low fertility.

Corpora lutea were observed more frequently in the right ovary than in the left. In gravid uteri, a greater proportion of foetuses were found in the right horn and, in addition, significantly more ova apparently migrated from the left ovary to the right horn than from the right ovary to the left horn. The numbers are given of large (diameter > 4 mm.) and medium (diameter 2–4 mm.) follicles observed in the ovaries both of non-pregnant ewes and of ewes in different stages of pregnancy, these stages having been estimated from measurements of foetal crownrump lengths.

1. Fifteen calorimetric experiments were made with three sheep which had fleeces varying in thickness from 2·5 to 12 cm. All sheep received a constant ration, which corresponded in amount and kind to that given to closely clipped sheep in previous experiments (Graham et al. 1958).

2. The metabolizable energy of the food increased with increasing environmental temperature by 2–3 Cal./24 hr./° C.

3. Heat production remained constant throughout the range of 15–35° C. environmental temperature. Above 35° C. an increase occurred. At 11° C. a slight rise in heat production occurred in the sheep with a 2·5 cm. fleece. These results show that sheep with fleeces, in contrast to closely clipped sheep, have very wide thermoneutral zones.

4. Heat losses by vaporization of water converged to an identical value irrespective of fleece length at 40° C. The rate of increase of vaporization with environmental temperature at lower temperatures decreased as the fleece length increased.

5. Respiratory frequencies for given total watervapour losses were the same whether or not the sheep had a fleece.

The response of S. 123 extra-late-flowering red clover in the year of sowing to three sprayings of gibberellic acid (GA) given at 28-day intervals is described. Plants in both soil and vermiculite cultures were used.

1. The first effects, noticeable in the basal rosette, were an increase in petiole length and a parallel increase in leaf area.

2. Fewer stems were formed on the treated plants but their thickness and the number and length of the internodes were increased.

3. Secondary branching was not significantly increased but the GA-treated plants produced a large number of tertiary branches from axillary buds on the secondary branches. Tertiary branching was not frequent in the control plants.

4. Cauline leaves showed an increased length/breadth ratio at each node with treatment, elongation tending to be most marked at those nodes where leaf formation coincided with GA sprayings. Leaf thickness was also increased by GA treatment.

5. Treated plants produced nearly 80% more heads, and flowering after GA treatment was up to 14 days earlier than the control.

1. Three calves were individually exposed in a climatic room to an environment of 45° C. dry-bulb and 28° C. wet-bulb temperature for 21 successive days up to 5 hr. each day.

2. In the 21-day period, mostly during the first half of it, the following changes in the physiological reactions of the animals were observed: progressive reductions in rectal temperature, in heart rate and in respiratory rate with a change of breathing from a laboured to a less laboured type.

3. It was suggested that a decrease in metabolic heat production might play a part in the observed acclimatization.

1. Three calves were exposed in a climatic room to an environment of 40° C. dry-bulb and 38° C. wet-bulb temperature for up to 110 min. each day for 1-2 weeks.

2. These exposures produced progressive changes in the physiological reactions of the animals to heat:

(a) Rectal temperature and skin temperature (for a given time of exposure) declined. In consequence there was a marked increase in the tolerance time, i.e. in the time for which the animals could withstand the hot environment before reaching a rectal temperature of 42° C.

(b) Respiratory rate rose earlier and assumed higher levels (for given levels of body temperature).

(c) Heart rate decreased markedly.

3. These changes are discussed in relation to heat loss and heat production and have been interpreted as reflecting chiefly a reduction in the metabolic heat production of the animals.

1. Three female calves (Shorthorn, Zebux Australian Illawara Shorthorn, and American Brahman) of about 7–8 months old were exposed to different combinations of wet- and dry-bulb temperatures in the psychrometric chamber at the Physiology Department of the University of Queensland.

2. A capsule method has been developed for measurement of cutaneous evaporation from limited areas. This method has been described in detail.

3. Cutaneous evaporation from the shoulder area of the Zebu cross was significantly higher than that of the Shorthorn. There was, however, no difference between the two animals in their cutaneous evaporation from the belly area.

4. In the Zebu cross the cutaneous water losses from the shoulder area, on the average, increased linearly with increase in skin temperature. In the Shorthorn, there was no important increase in the cutaneous evaporation from the shoulder area, although the skin temperature increased by about 2–3/ F.

5. The Zebu cross had lower skin temperatures of the shoulder area when compared with that of the Shorthorn. These lower skin temperatures were associated with higher cutaneous evaporation.

6. Increase in rectal temperature was not accompanied by increase in cutaneous evaporation in all the three animals studied.

7. In all the three calves the cutaneous evaporation increased with increase in air temperature.

An American Brahman calf of about 7–8 months age was placed in a hot chamber with a temperature of 108° F. dry bulb and 92° F. wet bulb. Sweat droplets were detected by preparing sweat prints on tannic acid papers applied closely to shaved skin areas smeared with ferric chloride solutions. The distribution of sweat spots on the sweat prints is similar to that of sweat glands.

An experiment is described in which sixty-four individually-fed pigs were used to investigate the effects of dietary protein status and administration of aureomycin on growth, efficiency of feed utilization and carcass conformation.

The main features of the results obtained were:

1. Pigs fed a ‘standard’ protein diet showed superior performance in terms of growth and economy of feed utilization in comparison with a ‘substandard’ ration. Appreciable differences in carcass quality including reduction in backfat and total body fat, concomitant with an increase in the lean meat content also resulted from variation in ration protein content. These results have been discussed in terms of the possible significance of both dietary crude protein status and amino acid content.

2. The administration of aureomycin at a ‘nutritional’ level had no apparent effect on any of the indices of pig productivity subject to analysis.

3. The high killing percentages noted over-all, have been discussed in relation to dietary energy and fibre levels.

Two calves (Zebu × Australian Illawara Shorthorn and Shorthorn) of about 7–8 months of age were exposed to controlled atmospheric conditions. Cutaneous evaporation from the belly area of these calves was measured by the capsule method. Records of the temperature of the skin under test and that of the air passed over the skin was also maintained.

The amount of water passing through the cattle skin was proportional to the difference between the saturated water-vapour pressure at skin temperature and the water-vapour pressure in the air. Tests were made for the water-vapour pressure difference varying from 9 to 25 mm. Hg.

The evidence from these combined variety × plant density experiments, together with the additional data on varieties previously reported (Bunting & Willey, 1958), suggests that, for fodder or ensilage production in Britain, the varieties we have designated as ‘medium’ (i.e. within the range represented by the hybrids Wis. 275 and Wis. 341 A), sown to give a final density of 9–12 plants/sq.yd. would be most suitable. Higher plant populations probably give slightly higher yields, but the differences will rarely be of practical importance and are likely to be offset by the greater incidence of lodging and the consequent increase in harvesting difficulties.

1. The availability of iron in three species of grass has been investigated using the rat as the experimental animal.

2. Two procedures, namely, the increase in blood haemoglobin concentration, and the gain in total gramme of haemoglobin by nutritionally anaemic rats were employed.

3. Inorganic iron, as ferric chloride, was shown to be significantly more available than the iron contained in the three grasses.

4. The iron in the grass timothy was found to be significantly more available than that in ryegrass or cocksfoot.

5. Possible reasons for the differences in iron availability were discussed.

Two calves (Aberdeen Angus and American Brahman) were used exposed to different combinations of wet- and dry-bulb temperatures in a psychromatric chamber at the Physiology Department of the University of Queensland. These animals were 7–8 months old when first exposed to heat.

Effect of various drugs affecting the sympathetic nervous system (adrenaline, noradrenaline, Dibenamine, Priscol, atropine and acetylcholine) on the rate of cutaneous evaporation in calves was tested. Cutaneous evaporation was measured by means of a capsule before and after the administration of these drugs.

Cutaneous evaporation increased with the introduction of adrenaline and was suppressed by the administration of Dibenamine. Noradrenaline and Priscol had no appreciable effect. Acetylcholine failed to stimulate sweating and atropine did not block the sweat glands.

Sweat glands of cattle were, therefore, found to be functional and their innervation adrenergic. Cattle use sweat to prevent body temperature from rising, yet the amount of sweat secreted is not large enough to allow cattle to maintain thermoneutrality at high air temperatures.