1. The estimation of milk yield in a herd of suckled zebu cattle has been described.

2. Milk yield was found to be relatively stable when compared with weight at calving and subsequent live-weight change.

3. Under constant conditions, there was a negative correlation between milk yield and live-weight change in the cows, compared with a positive correlation when both characters were affected by seasonal changes.

4. Variation in milk yield was reflected in the growth rate of the calves, but considerably greater quantities of milk were required to increase growth without the aid of extra grass.

5. It was concluded that, under the present conditions, calf growth rate could be increased more efficiently by the improvement of nutrition than by selection for high milk yield in the dams.

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. The efficiency of food conversion of Brown Leghorn fowls inbred for egg number, or egg size, or egg number and egg size have been compared.

2. Comparison between the lines was made for egg numbers, total egg weight and total egg energy. Egg energy was the best measure of production, total egg weight was the next best and egg number the poorest.

3. When allowance was made for differences in rates of egg production and egg size, there were no differences in the efficiency of conversion of food to eggs between the lines.

4. The standard errors of the means for the analytical data on the twelve replicate mixes of the diet were relatively small, but the range in values was appreciable. The importance of analysing diets in nutrition experiments is stressed, particularly for ‘iso-caloric’ diets.

The present work extends the information on the skin thickness of cattle and shows that generalizations made in previous work were only partly correct, for there are significant differences only between the skin thickness of the Zebu ‘races’ of tropical cattle and Bos taurus.

Again there appeared to be no significant difference between animals of different ages within breeds.

The work confirmed that cattle of eleven tropical breeds comprising four of the major ‘races’ of African indigenous cattle have a significantly thinner papillary layer than temperate breeds, and this was very strongly correlated with their superior heat toleration.

Further support based on wider premises was therefore given to suggestions made by Dowling regarding the importance of the histology of the skin in heat toleration.

An examination of the population density and morphology of the apocrine glands of four ‘races’ including fourteen breeds of African indigenous cattle has been completed.

Two types of gland were found, the club-shaped and the sac-like, and it is suggested that the former is the more primitive form.

Considerable differences in gland density and volume were found. In the thoracic-humped African Zebu both of these were similar to figures given for B. indicus sui generis.

Gland volume was found to be closely correlated to heat toleration, but it is suggested that secretory rate is probably of high importance in view of the fact that despite differences in gland volume, there were only small differences in heat toleration coefficient.

It is suggested that the heat toleration coefficient as presently defined may not be a reliable indication of the animals tolerance of prolonged high temperatures.

A suggestion is made regarding the mechanism of heat control by sweating in cattle.

1. The normal sweat glands of twenty-eight calves, nineteen live adult cattle and eighteen slaughtered cattle from temperate breeds were examined. In every animal the lumen of the sweat glands contained a fluid-like material.

2. It appeared on examination and rough measurement that the size of the sweat glands taken from animals after slaughter was smaller than that of the glands taken from live animals even when the same sampling technique was used for both.

3. The sweat glands of sixteen calves were examined before and at intervals after the animals had been subjected to a hot environment. The glands were always seen full of a fluid-like material.

4. It is concluded that if the calf sweat gland is stimulated by heat stress it must function either (a) by simple diffusion through the sweat gland wall and hence to the skin surface, or (b) by a secretory process not involving degeneration of the glandular epithelium. It is probable that at least part of the contents of the lumen of the sweat glands is derived from the epithelium by a process of active secretion.

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.

1. A study was made of the effects of diet on the growth of the internal organs, and in particular the four stomachs of lambs.

2. A total of twenty-three lambs was reared from birth on various diets ranging from all milk to small amounts of milk and roughage ad lib. The lambs were slaughtered at various ages and the fresh wet weights of the parts of the alimentary tract and the other internal organs were recorded.

3. The growth rates of the four stomachs were influenced by the plane of nutrition, however, the type rather than the plane of nutrition was more important in determining the weights of the stomachs relative to each other and to live weight.

4. Lambs fed solely milk from birth had the development of their fore-stomachs retarded at about the level found in the 3-week-old grazing lamb. The abomasums of these lambs were abnormally heavy.

5. The rumens and reticulums, which were retarded in their growth by milk feeding, reached normal proportions very quickly once roughage was fed.

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.

1. A small-scale plot experiment which had been conducted from 1947 to 1952 to study the effect of massive dressings of fertilizer nitrogen, with and without phosphate and potash, on the yield and quality of a rye-grass dominant sward was continued from 1953 to 1958 with two changes in the mineral treatments in 1953. A 4 × 4 Graeco-Latin square was used.

The nitrogen treatments applied each year were: (1) no nitrogenous fertilizer, (2) 260 lb. nitrogen, (3) 520 lb. nitrogen and (4) 416 lb. nitrogen per acre per year.

The mineral treatments were: (A) no mineral fertilizer, (B) 336–504 lb. K2O per acre per year depending on nitrogen treatment, (C) 101–202 lb. K2O and 81–101 lb. P2O5 per acre per year depending on nitrogen treatment, and (D) no mineral fertilizer after 1953, although K2O and P2O5 had been applied during the previous 6-year period.

All the fertilizers were applied in four or five equal dressings each year, one for each cut.

Treatments 1 and 4 were cut four times and treatments 2 and 3 five times per year.

2. Applications of phosphate did not affect the yields of herbage dry matter or crude protein, but yields were severely depressed in the absence of potash. With adequate potash the yields under all nitrogen treatments were maintained for the 6-year period and were at the same level as in the previous 6-year period. The mean yields of dry matter for the 6-year period when potash was applied were 5200, 8420, 10,180 and 9700 lb. per acre per year for treatments, 1, 2, 3 and 4. Without potash the corresponding mean yields were 5460, 6410, 6210 and 6880 lb. Average crude protein yields were 760, 1360, 1940 and 1660 lb. per acre per year with potash and 780, 1100, 1220 and 13201b. without potash.

3. The weighted mean contents of crude protein for the 6-year period averaged over all the mineral treatments were 14·4, 16·7, 19·4 and 18·2% for nitrogen treatments 1, 2, 3 and 4. The mean crudeprotein contents of treatments with and without potash were 16·7 and 17·6%, respectively.

4. The average response to nitrogen was 15·0, 10·9 and 12·4 lb. dry matter per 1 lb. of nitrogen applied on treatments 2, 3 and 4, respectively, compared with a no-clover sward, and 7·8, 7·3 and 7·9 lb. compared with a grass + clover sward. The recovery of nitrogen in terms of crude protein was 45, 40 and 40% for treatments 2, 3 and 4, respectively, when compared with a no-clover sward.

5. The botanical composition of the plots continued to be determined by the nitrogen and potash treatments. On plots receiving ‘Nitro-Chalk’ clover was virtually non-existent, whereas on plots which received potash and no nitrogen, clover was present. With a combination of potash and nitrogen vigorous swards of timothy were found but if only nitrogen and no potash was applied, poorer grasses, such as Festuca rubra, were dominant.

6. Soil analyses showed increased pH values and decreased contents of Mg with increasing applications of ‘Nitro-Chalk’. P2O5 values were low except where phosphate was being applied. The most marked change was in the K2O values which varied from 4 units on treatments A and D which received no minerals to 40 units on treatment B which received the heavy dressings of potash.

7. Mineral analyses of the herbage for 1953 and 1958 are given. High K contents were found on treatments where potash was applied and this was associated with decreased Mg and Na contents.

8. Some details are given of a field-scale trial on the Institute farm where high levels of nitrogen and potash have been applied for 11 and 12 years with successful results.

1. Three trials are reported in which the grazing behaviour of separate groups of cows, one receiving supplementary food, either as conserved roughage, concentrate or fodder crop, was observed over 24 hr. periods. A fourth trial, assessing the effect of summer temperatures on unshaded milking cows, is briefly described.

2. In trials 1 and 2 the stall feeding of either conserved roughage or concentrate reduced grazing as compared with unsupplemented cows by approximately 10%.

3. Allowing access to a fresh ‘strip’ of a fodder crop at a set time each day, whilst not altering total grazing time, very markedly altered periodicity of grazing. Cows delayed grazing up to 3 hr. whilst awaiting a fresh ‘strip’.

4. Environmental temperatures up to 87° F. did not alter total grazing time as compared with grazing time when temperature reached a maximum of only 70° F.

5. The value of supplementary feeding of dairy cattle at pasture, at least where the intake of pasture is sufficient for maintenance and a low level of production, appears to be open to question.

Two early weaning experiments are reported. When grazing young, high protein pastures, lambs weaned at 7, 10, 13 and 18 weeks of age grew equally well and there were no significant differences between their carcass weights, grades, and dressing percentages.

However, when grazing pastures in the preflowering and flowering stages of growth, lambs weaned at 8 weeks of age did not grow as well as unweaned controls. Their carcass weights, grades, and dressing percentages were also inferior. It is suggested that these differences were primarily due to an inadequate protein intake.

No difference in wool production was found either between the ewes of early weaned and control lambs, or between the lambs themselves.

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.

Groups of Rhode Island Red chicks were fed a mash made up from East African feedingstuffs or that diet supplemented with a high level rate of aureomycin—97 g. aureomycin hydrochloride per ton of feedingstuff. The chicks were kept on wire for 8 weeks. The initial improved growth rate of the chicks fed the aureomycin supplemented feedingstuff was not maintained, nor was there any statistical indication that the addition of aureomycin improved the feed conversion rate.

Although the mortality rate appeared to be very much lower in the chicks fed the aureomycin supplement, the evidence was too limited to allow this to be attributed solely to the effects of the aureomycin.

The experiment illustrates the need for careful design in order that the effect of the factors to be tested may be separated from the effects of other factors contained in the experiment and not confounded with them. Moreover, advanced statistical analysis should be used as an invaluable aid to, but not a substitute for, visual or graphical examination of results, for such examination often yields valuable indications of possible lines of analysis and may avoid the drawing of unjustified conclusions.

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.

1. Three completed series of laying trials involving the incorporation of calcium lactate in the diet are reported.

2. The addition of 1 or 2% calcium lactate to a layers mash results in a significant increase in egg production and/or the efficiency of the ration in terms of numbers of eggs per unit weight of food consumed. This effect has been obtained in birds at the onset of lay and also in birds that have been in lay for some 5 months.

3. The incorporation of 0·5% calcium lactate appears to be inadequate.

4. There is no evidence to date that the effect is attributable to dietary calcium, but the mechanism of action is unexplained.

5. Egg-weight, but not egg-quality, as judged by routine candling, is slightly lowered by feeding calcium lactate.

1. Field experiments are described in which the absorption of radioactive strontium by rye-grass and lucerne has been investigated during 1958 on five soil types which represent a range in exchangeable soil calcium content. 89Sr was applied as a spray to both arable land and to established pasture.

2. Absorption was reduced by a factor of up to 4 in rye-grass (shallow rooted) following ploughing to 11 in. compared with leaving the contamination on the soil surface. These results are compared with those obtained in an earlier series of experiments in 1957.

3. The ratio of 89Sr to calcium was highest in crops grown on soil low in calcium (2 m-equiv. Ca per 100 g. extracted with N-ammonium acetate).

4. The addition of lime reduced absorption of 89Sr from the soil only when the exchangeable soil calcium content was relatively low. Some effect was observed in soils containing 7–8 m-equiv. Ca/100 g., a considerably larger one in a soil containing 2 m-equiv.

5. Only small differences occurred in the ratio of 89Sr to calcium between lucerne and rye-grass. This comparison was not made beyond the first 6 months of growth.

6. Experiments carried out with established pastures on four soil types indicate that 89Sr is more readily absorbed from the ‘plant-base’ than after incorporation with soil. Ploughing and reseeding may reduce the ratio of 89Sr to calcium in herbage by a factor of up to 4. This effect may be greater on mature swards.

7. The liming of contaminated swards reduces the ratio of 89Sr to calcium in herbage by a factor of 2 to 3 regardless of the calcium content of the soil, and liming followed by ploughing and reseeding by a factor of 3 to 7.

1. The digestibilities of the protein, oil and carbohydrate by chick in mash and pellets made from this mash have been determined at weekly intervals from 0 to 9 weeks.

2. There was no difference in the chemical composition of the food due to pelleting, not were there any differences in the digestibilities due either to pelleting or the age of the chick.