Early morning and midday body temperatures of rams and ewes of three breeds of sheep were measured once weekly for a period of 10 months in Northern Rhodesia and 12 months in Southern Rhodesia.

1. In all breeds seasonal fluctuations in body temperature were due to concurrent fluctuations in ambient air temperature.

2. Mean annual body temperatures were: Merino 102·2° F.; Persian 101·7° F. and Native 101·7° F. Wool and hair breeds differed considerably in their early morning temperatures and in their body temperature increases from 6.30 a.m. to 12.30 p.m. Mean annual values for these measurements were Merino 101·73 and 1·92° F.; Persian 100·81 and 1·83° F.; Native 100·73 and 1–92° F. At all times Merinos showed markedly greater uniformity of body temperature than either hair breed. There was no evidence to show that the thermoregulatory mechanisms of these animals had been stressed unduly.

3. Sex had no consistent effect on body temperature or on rise in body temperature.

In general, lactating ewes showed a significantly higher initial body temperature than either empty or pregnant ewes, but the respective heat tolerances as measured by body temperature increase did not differ appreciably. Body temperature differed little in empty and pregnant ewes.

4. Although the youngest group of ewes in each breed showed the highest early morning temperature, there was no evidence that heat tolerance was less in young than in old animals.

5. Black-coated Native ewes had higher initial body temperatures and a smaller body temperature increase during the summer months in Southern Rhodesia than brown or broken-coloured Native ewes. These effects were due to differences in coat density rather than to differences in coat colour or skin pigmentation.

6. In all breeds the magnitude of the diurnal and annual variation in body temperature was different in Northern and Southern Rhodesia. Differences were largely of climatic origin but low plane of nutrition in Southern Rhodesia possibly reduced critical body temperature and impaired thermoregulatory ability.

Responses in body, skin and coat temperatures, cardio-respiratory frequencies and rate of moisture secretion of ewes of three breeds to the diurnal fluctuation in ambient temperature were recorded in the presence and absence of drinking water during the hottest part of the Rhodesian year.

1. At 7.0 a.m. body temperatures were: Merino 102·8° F.; Persian 102·2° F. and Native 101·5° F. Between 7·0 a.m. and 1·0 p.m. body temperature rose almost equally in Persians and Natives and fell slightly in Merinos. Change in body temperature between 7.0 a.m. and 1.0 p.m. was not affected significantly by availability of water nor age of ewe, but varied with type of thermal burden (i.e. solar insolation only v. solar insolation plus artificial heat) when water was not available. Although air temperature fell towards late afternoon body temperature of Merinos and Natives rose appreciably, that of Persians only slightly.

2. At 7·0 a.m. respiratory rates were (cyc./min.): Merino 59·6; Persian 43·0; Native 29·9. Increase in rate of respiration was the main thermolytic mechanism in all breeds. Merinos had a lower threshold of respiratory response to rising ambient temperature than either hair breed but increase in rate of respiration between 7.0 a.m. and 1.0 p.m. did not differ significantly with breed or age.

3. No breed appeared to use the peripheral blood system in thermoregulation. Cardio-frequency, as a measure of this blood flow, remained almost constant with a slight tendency to fall with rise in ambient temperature.

4. In all breeds skin temperature was related to ambient and body temperatures; consequently the diurnal fluctuation in skin temperature differed in wool and hair breeds. When thermal burden was greatest Merino skin temperature fell, that of hair breeds did not.

Except at 11.0 a.m. there was a gradient between rectal, skin and air temperatures. Direct elimination of heat was thus possible for 23 hr. each day.

5. In hair breeds moisture secretion depended on insensible perspiration; consequently, rate of moisture secretion changed with body and air temperatures. In Merinos moisture for skin surface evaporation was provided by sensible and insensible perspiration. Natives may be able to sweat at temperatures higher than those recorded but it is unlikely Persians have a sweating mechanism.

6. In all breeds coat temperature was related closely to ambient temperature and changes in solar conditions evoked immediate response in coat temperature. Merino fleece apparently stabilized skin temperature whereas Persian and Native hair did not.

Mature and young Merino, Persian and Native rams were compelled to run 1 mile in 10–12 min. The response to the thermal burden induced by this exercise was measured in terms of body and skin temperatures, rate of respiration and length and temperature of the scrotum.

1. Marked increases were recorded in every body response immediately after the exercise. Body, skin and scrotal temperatures returned to normal within 2 hr. but respiratory rate remained elevated for a further 4 hr.

2. There were breed differences in the initial and subsequent measurement of every response. At 7.0 a.m. when there was no thermal stress body temperatures and rates of respiration were: Merino 102·9° F.; 3·-6 cyc./min. Persian 101·4° F.; 23·8 cyc./min. Native 102·1° F.; 28·9 cyc./min. Merino rams had the greatest ability to combat rising ambient temperature, Native rams the least. Persian rams recuperated quickest after exercise, Native rams slowest. The different responses of wool and hair breeds were apparently due to their coats. Merino fleece stabilized body temperature, did not aggravate the effects of exercise unduly and did not greatly hamper elimination of heat from the body after exercise.

3. In all breeds respiratory evaporation was the principal thermolytic process. Rate of respiration was a sensitive indicator of thermal stress but it could not be used as an index of heat tolerance because the associated changes in respiratory volume were not known.

4. Age was seldom of significant importance to determine response to thermal burden. In general young rams were affected less adversely by exercise and more adversely by rising ambient temperature than were mature rams. These differential effects were probably due to leggy conformation, low live weight and physical fitness in young rams on one hand, and incomplete development of the thermoregulatory system on the other.

5. Increase in scrotal pendulance was related inversely to ability to maintain normal body temperature.

6. In view of the influence of age and body conformation on the response to exercise it was questioned whether comparable heat tolerance indices could be obtained by this method.

The influence of fleece on thermoregulation in German Merino ewes was investigated in Rhodesia. Comparative heat tolerances of Persian Blackhead, indigenous Native and shorn and unshorn Merino ewes were obtained during the hottest month of the year in Northern Rhodesia. The main thermolytic responses in unshorn, partially shorn and completely shorn Merino ewes were measured at 7.0 a.m.; 10.0 a.m.; 1.0 p.m. and 4.0 p.m. during April in Southern Rhodesia.

1. Unshorn Merino ewes showed more and shorn Merino ewes less effective body temperature regulation than Persian or Native ewes. High heat tolerance in unshorn Merinos was due primarily to insulation by the fleece and not to more efficient physiological thermolysis than in hair breeds. No ewe showed signs of undue thermal stress and feed intake was not affected by heat.

2. Increases in rectal temperature and respiratory rate between 7.0 a.m. and 1.0 p.m. of Merinos in Southern Rhodesia were related inversely to fleece length. Body temperature did not differ significantly at 1.0 p.m. owing to differential rates of increase in respiratory rate.

3. Magnitude of the diurnal fluctuation in skin temperature was also related inversely to fleece length. Partially shorn ewes, however, began with and maintained highest skin temperature through the heat of the day. In all groups skin temperature fell after 10.0 a.m. although ambient temperature continued to rise. This fall could not be attributed to sweating since moisture secretion declined simultaneously.

Three different stocks of mice were selected for five generations for high body weight at 3, 4½, or 6 weeks of age. Changes in body weight at the three ages and in abdominal fat weight, an index of carcass composition, which occurred in the three lines were compared. It was found that the proportion of fat in the carcasses of the selected animals increased markedly in the lines selected for high 3-week weight, while in the other two lines the proportion remained the same as that in the control line.

The theoretical treatment of the genetic relationship between body weights at different ages and between body weight and abdominal fat was reasonably adequate in accounting for the correlated responses actually observed.

A study has been made of all eggs laid over a year (March-March) by twelve birds.

It was found that:

1. Shell thickness, yolk weight and white weight all increased with time.

2. For each individual bird a linear relationship existed between yolk weight and yolk calcium weight and between yolk weight and yolk phosphorus weight.

3. High calcium diets significantly increased shell thickness at the beginning of the experiment and yolk calcium around the middle of the experiment. Dietary calcium levels had no other effects and dietary phosphorus levels no effects at all.

4. The ‘curves’ relating shell thickness and time for each individual bird are discussed in relation to the relative merits of different birds as producers of thick shells.

1. The general seasonal trends of top-soil nitrate and ammonia-N, and growth of the coffee tree are described for conditions of both soil and climate which are representative of a large proportion of the coffee-producing area in Kenya.

2. When rainfall is heavy and persistent at the beginning of a rains period soil nitrate-N levels decrease rapidly, partly because of leaching losses and partly through uptake by the crop. Under conditions of rainfall and cropping similar to those described for the first half of 1954, the flush of nitrate-N in the early part of the rains will not be detected under field conditions. When the onset of the rainfall season is more gentle and substantial water movement through the upper part of the soil profile does not take place, for example, Short Rains, 1954, nitrate-N values do not decrease rapidly and there is indirect evidence of the stimulatory effect of this type of rainfall on nitrate-N formation in a remoistened field soil.

3. Rapid and substantial build-up of nitrate-N is shown to take place during intervening dry weather between the rainfall periods. This is particularly marked in the top 6 in. of the soil profile and is attributed to nitrate-N formation in the absence of leaching losses; to a decreased rate of uptake by the coffee tree in the absence of vigorous growth and to the physical movement of nitrate-N upwards into the top-soil.

It may be inferred from the results that alternate periods of rain and sunshine, rather than continuous heavy rain, will favour high soil nitrate-N levels and a more satisfactory nitrogen nutrition of the coffee tree.

4. During periods of very low soil moisture ammonia-N builds up in the dry top-soil.

5. The sharp peak and rapid decline in the rate of coffee growth during the Long Rains period coincides with very low soil nitrate-N values although climatologically conditions for continued growth are still excellent. This suggests that low available soil nitrate -N may be at least partially responsible for this early and rapid decline in the growth rate.

6. In the light of observed trends in nitrate-N and coffee growth the timing of fertilizer nitrogen application to mature coffee has been altered. During the Long Rains split applications are recommended with the particular object of maintaining a supply of readily available nitrate-N in the soil. An additional and supplementary fertilizer nitrogen application is also suggested in the Short Rains period.

1. The effects of the stage of growth and frequency of cutting on the yield and chemical composition of Panicum maximum Jacq., under the tropical humid conditions prevailing in Ibadan area were studied in the season 1953 to 1954. The cutting frequencies adopted were seventeen, eight, six and four times harvesting a year which corresponded respectively to a growing period of 3, 6, 8 and 12 weeks before the plants were cut.

2. It was shown that Guinea grass gave the highest growth rate and cumulative green fodder yield (approximately 28 tons per acre) per year when allowed a 12-weekly growth cycle. Cutting the grass every 3 weeks gave a total minimum yield of 20 tons per acre. 6-weekly samplings resulted in higher green fodder yield than cutting it every 8 weeks. Such yield differences which exist among the various cutting treatments, however, are not statistically significant. When yields of edible (leafy) green fodder were considered, the order of superiority was 3-weekly > 6-weekly > 12-weekly > 8-weekly.

It was shown that the increased yield of green and dry fodder obtained from the 12-weekly cut grass was made up of both fresh regrowth as well as of grasses which had been growing for 12 weeks.

3. P. maximum contains a fairly high percentage of dry matter and this increased directly with the length of cutting intervals. Dry-matter yields, like those of green fodder, were highest for the 12-weekly harvested material, followed in order by the 6-weekly cut, the 8-weekly cut and the 3-weekly cut samples. However, the production of leaves and the accumulation of dry matter in them, are inversely related to the length of growing interval up to and including grasses allowed 8-weekly growing periods.

4. The stems of P. maximum tend to mature more rapidly than the leaves, particularly at a growing stage of between 3 and 6 weeks of age. At between the 8 and 12 week growth stages, the development of the stem of P. maximum in relation to that of its leaves was not as rapid as observed in the case of either P. purpureum or of Andropogon tectorum.

5. The percentage dry matter, nitrogen-free extract, ether extract and calcium are directly related, while those of crude protein, silica-free ash, phosphorus and magnesium, are inversely related to the length of cutting intervals. It was also shown that the mean percentage crude protein of Guinea grass of about 12 at 3 weeks of growth, declined by 45% to 6·4 when the grass was cut every 12 weeks. The grass contains a high amount of magnesium, a reasonably high amount of calcium, but a somewhat low content of phosphorus, a fact which accounts for the wide calcium to phosphorus ratio. This ratio widened with the length of cutting intervals.

6. When Panicum maximum was cut at 3 -weekly intervals, it produced 69·3% more protein, 58·5% more silica-free ash, 32·3% more calcium, 49·6% more phosphoric acid, 71% more magnesium and higher amounts of carbohydrate and total nutrient material than when it was allowed to grow for 8 weeks. Similarly when the grass was allowed a 12-weekly growth cycle, it produced 35% more of total nutrient, 36·5% more of carbohydrate material and 62·2% more of calcium than when it was sampled every 8 weeks. It appears totally unprofitable from the point of view of yield of chemical constituents to subject P. maximum to a growth cycle of 8 weeks.

7. Yields of green and dry matter and the percentage crude protein, silica-free ash, and nitrogen-free extract are directly related to the degree of precipitation. In general periods of high rainfall were accompanied by higher yields and percentage content of these constituents, while periods of low rainfall gave rise to smaller yields. The percentage content of crude fibre, on the other hand, was inversely related to rainfall.

Sixteen osteodystrophic dwarf cattle and ten controls of comparable age were slaughtered. The components of the body and eviscerated carcass were weighed and measured. At birth the dwarfs were thick and blocky. At the time of slaughter a bulging forehead was common but not always extreme and not always present. The symptoms of dwarfism became increasingly pronounced with age, due to retarded growth. The dwarfs had shorter thoracic cavity, abdominal cavity, body, loin, hind leg, arm bone and forearm bone than the controls. No explanation can be given for the difference. However, the dwarfs were hydrocephalic and had significantly lighter adrenal and pituitary glands than the control animals. The dwarf animals had more blood, heavier feet, less abdominal fat, smaller loin ‘eye muscle’ area at the 12th rib and a less deep loin ‘eye muscle’. The dwarf females had a lighter rumen (with and without contents) and large intestines (without content) as a percentage of live weight than the controls and dwarf males. There was no difference in palatability of the meat or percentage of wholesale cuts from the dwarf and control animals except for percentage of plate. The following three ratios were disproportionate in the dwarfs as compared with the controls:

1. A relatively inexpensive closed-circuit respiration chamber for cattle is described.

2. Experiments with two steers are reported in which heat production and energy retention data were measured at different levels of food intake and at different environmental temperatures.

3. The energy lost in faeces increased with improving plane of nutrition but was not significantly affected by the environmental temperature. Urine energy losses fell with increasing environmental temperature at low planes of nutrition. Methane losses increased with improving nutritional plane but were reduced by high environmental temperatures at high levels of food intake.

4. The heat production of fasting animals, or animals on low planes of nutrition was not influenced by the environmental temperature in the range 20–40° C. On higher planes of nutrition an increasing environmental temperature increased the animals' heat production.

5. The major factor determining energy retention in different environments is the heat production of the animal. Net energy values consequently vary with temperature.

An insignificant short-term increase in the natural dose of ionizing radiation during the embryogenesis period is beneficial not only for the embryonic development of the chicks, but also for their postembryonic growth and development as well as the egg production of the pullets.

Irradiation of incubated eggs with microdoses of radioactive radiations is another possibility for the utilization of atomic energy bringing about an improvement in the economically useful properties of poultry.

1. In seventeen digestibility trials carried out between May and November, 1957, groups of three steers were fed on fresh herbage, cut mainly from mixed swards. Herbage digestibility and the concentrations in faeces of the index substances nitrogen and chromogen were measured over periods of 5 days. Organic matter digestibility ranged from 61·2 to 78·9%.

2. The relationship between herbage digestibility and faecal nitrogen concentration could not be described satisfactorily by a single regression equation for all trials, and separate equations were calculated for (a) first-growth herbage and (b) aftermath (second and third growths). For a given faecal nitrogen concentration herbage digestibility was about five units higher for first-growth than for aftermath herbage.

3. For the faecalchromogen-digestibilityrelationship the difference between growths was even greater and, again, two equations were required. In most trials the quantity of chromogen excreted was apparently greater than the quantity consumed.

4. The ‘seasonal’ differences in faecal index relationships were caused by the fact that later growths of herbage contained considerably greater concentrations of nitrogen and chromogen than did firstgrowth herbage of the same digestibility. There was also some evidence that the relationships may be affected by the application of nitrogenous fertilizers to the sward.

5. In order to avoid biases in the indirect estimation of herbage digestibility it appears important to use different regressions for different growths. Although such regressions would be restricted in their application they are likely to be more precise than general equations. In these trials both nitrogen and chromogen regressions had low residual standard deviations of ± 1·5 units of digestibility.

1. A mixed sward was divided into two areas receiving high (H) or low (L) levels of fertilizer nitrogen, and on two occasions, in spring and summer, herbage cut from each area was given to three steers in a continuous digestibility trial lasting 45 days. Digestibility and faecal nitrogen concentration were measured for each animal for each 24 hr. period, and equations relating these variables were calculated for each trial from the unit 24 hr. observations and from averages over three animals and over successive 2-, 3-, 5- and 9-day periods.

2. In the two spring trials herbage digestibility remained constant for the first 12 days and then declined by about 0·4 units per day. In the summer trials digestibility declined throughout by 0—25 units per day. The nitrogen content of the herbage was consistently 25% higher for treatment H, and declined steadily throughout each trial.

3. Both season of cutting and fertilizer treatment had a significant effect on the faecal index regressions obtained. Equations calculated from average values for three animals and 3 days predicted digestibility coefficients from 3% faecal nitrogen as follows: equation (1) spring H, 76·5; (2) spring L, 77·5; (3)summer H, 71·8; (4) summer L, 72·8.

4. The joint residual standard deviation for equations (1) to (4) had the low value of ± 0·90 units of digestibility, indicating that ‘single-sward’ regressions are considerably more accurate than those embracing a great variety of herbages. Even greater accuracy was obtained when digestibility and faecal nitrogen concentrations were measured for periods longer than 3 days; in general, residual variance varied inversely with period length. Using values for individual animals in the regressions increased the residual variance slightly, but because differences between animals in the digestibility-faecal nitrogen relationship were small and generally nonsignificant, the increase was by a factor of the order of 1·6, not 3.

5. Standard errors of prediction were calculated, although there is evidence to suggest that these underestimate the error of digestibility coefficients predicted for free-grazing animals. It is concluded that faecal index regressions are accurate enough for measuring digestibility per se in grazing experiments. In the measurement of herbage consumption, however, the experimental error is likely to be high, partly because indigestibility is the factor required to be predicted, but mainly because of large differences in appetite among similarly treated animals.

1. The change in concentration of 131I with time in plasma, urine, milk and the thyroid gland has been followed in four cows after administration of either a single oral dose or of 131I from a decaying source every 6 hr. for 14 days.

2. The observed changes in concentration following multiple doses have been compared with those predicted from the single-dose experiments.

3. Small discrepancies were observed between the observed and predicted course of events in urine, milk and the thyroid gland: their significance is considered to be doubtful.

The digestibility of the non-protein constituents (almost entirely carbohydrate) of ruminant fodders is shown to be a function of the level of the crudefibre and crude-protein components.

The effect of increasing crude fibre in the diet is to depress the digestibility of carbohydrate, irrespective of the level of crude protein associated with it.

The effect of crude protein on the digestibility of carbohydrate is only well marked when its concentration in the dry feed lies below some 5%, that is when the feed is below approximate maintenance levels. Increasing the crude-protein content of the diet from some 2 to about 5% leads to increased digestibility of carbohydrate, but thereafter in the range of some 6–30% crude protein the protein effect is very slightly depressing to carbohydrate digestibility and is apparently quite negligible at average crude-fibre concentrations to be expected at any given level of crude protein.

The implications of the various aspects of this paper are that the variability in digestibility of the non-nitrogenous component of ruminant feeds depends mainly on the respective levels of crude protein and crude fibre in the diet and to a very much lesser extent, if at all, on the species of ruminant or class of feed, be it silage, roughage or even mixture.

1. Fifty-two experiments were made with two Cheviot and two Blackface wether sheep in which heat production and heat emission were determined at environmental temperatures of 8, 20 and 32° C. Initially the sheep were closely clipped to within 1–2 mm. of the skin and the fleece was then allowed to grow throughout the experiments.

2. At 32° C. fleece length had no effect on heat production. At 20° C. metabolism was elevated until fleece length exceeded 18 mm. At 8° C. metabolism was elevated until the fleece length exceeded 35–40 mm. No differences were found between the two breeds in their heat production at a particular temperature provided fleece length was identical.

3. The sensible loss of heat divided by the temperature gradient from the rectum to the environment (conductance) was linearly related to the logarithm of fleece length, both at environmental temperatures above and below the critical temperature.

4. No differences between the two breeds or between them and Down Cross sheep were found with respect to their conductances when devoid of fleece. The insulation provided by unit length of fleece was the same in all three breeds and crosses. The fleece of the Blackfaces grew at twice the rate of that of the Cheviots so that at a given time after shearing, the Blackfaces were more resistant to concold.

5. Studies of the losses of heat by the vaporization of water and of skin and fleece surface temperatures also showed no differences between breeds.

6. Analysis of the relation between heat concold, ductance and fleece length suggests that vasoconstriction and vasodilation border on all-or-none effects.

It is shown that reasonable estimates of the average amounts of total digestible nutrients and gross digestible energy of ruminant feeds can be derived from knowledge of only the crude-protein and crude-fibre contents of such material as fed. These estimates do not appear to be markedly affected, if at all, by differences in class of feed or species of ruminant whether cattle, sheep or goat.

A table of the average estimates of digestible crude protein and total digestible nutrients, to be expected at different levels of crude protein and crude fibre, is presented for use in the estimation of the average nutritive value of feeds whose digestibility has not been studied in detail by means of numerous animal trials.

Inherent in the relationship between either total digestible nutrients or gross digestible energy and the proximate partial composition of the feed is a suggestion that if a low plane of protein nutrition is prolonged, that is when the crude protein of the dry diet lies persistently below some 5% in the dry feed, there is likely to be a sharp fall in the total digestibility of the feed.

For 8 weeks after farrowing, sows were fed their standard ration (depending on the number of piglets being suckled) in either thirteen or fourteen feeds per week. The omission of one feed per week did not affect the performance of the 3-week-old litters whether reared indoors or outdoors. The response of the 8-week-old litters to sow-feeding system, however, appeared, from the limited data available, to be inconsistent over rearing environments, those reared outdoors being more affected by feeding system than those reared indoors. The outdoor reared litters consumed significantly more creep feed and were significantly heavier at 8 weeks of age than litters reared indoors, confirming previous observations. During the suckling period the sows lost on average 74·4 lb. in weight; weight loss was not influenced by environment or feeding system.

A simple method has been described for measuring photosynthesis of detached leaves.

The reduced rate of photosynthesis of the tea leaf, immediately after excision, is due to stomatal closure. In mature detached leaves, kept well supplied with water in diffuse light or darkness and in a humid atmosphere, normal stomatal opening and maximum photosynthetic rates were obtained between 12 and 30 hr. from excision. Stomata on sunflower leaves do not close on excision.

Variation in the initial concentration of CO2 between 1·0 and 4·0% vol. with a final concentration not below 0·5% did not affect the rate of photosynthesis of sunflower leaves at 25° C. and under 32 klux light intensity. Under the same conditions of light and temperature, there was no change in the photosynthetic rates of tea leaves in 1 and 2% initial and 0·2% final CO2 concentrations. There were indications that CO2 concentrations below 1·0% might be rate-limiting for certain tea leaves, assimilating under low light (4 klux).

The development of photosynthetic capacity in the young leaves of tea and sunflower is a gradual process. In sunflower, the photosynthetic capacity develops fully before, and in tea after the leaf reaches half its final size.