It is known that acidic red lateritic soils are usually deficient in available phosphorus, and whenever any soluble phosphates are added to such soils they become fixed and non-available to plants. It is believed that added phosphates make insoluble compounds of ferric phosphates with iron salts in the ferric state. Since ferrous salts are more soluble than the ferric salts, it suggests itself that if in the soil we can keep the iron in the ferrous state or can effect the conversion of ferric salts into ferrous salts it may be possible to reduce the formation of insoluble iron salts with phosphorus and thus increase the amount of available phosphorus by reducing phosphate fixation. With this object in view red latoritic soils from Dacca Farm area were kept under water-logged condition and the effect upon the conversion of Fe3+ into Fe2+ state and the change of readily soluble phosphorus were studied from time to time.

Records of plant development in some twenty-five multifactorial experiments were collected with the object of analysing the effects of nutrient level, density, spatial arrangement and variety on seed production in linseed. By sampling techniques estimates were made of plant density, the extent of basal branching, the number of capsules per stem, the number of seeds per capsule and the seed weight. The expected plot yields, calculated from these data, were in good agreement with the harvested yields.

In factorial trials, involving additions of nitrogen, phosphorus and potassium, only a change in the nitrogen level increased the yield of seed, and this gain was largely determined by an increase in the production of capsules and not by any alteration in either the number of seeds per capsule or the seed weight.

Over a range of density of thirty to eighty plants per square foot the number of capsules produced per plant was inversely correlated with density. When the distance between drills was maintained at 6–7 in. and the density varied by changing the seed rate then—on an area basis—both capsule production and seed yield were rarely affected since the product of plant number and capsules per plant remained relatively constant. On the other hand, if the rate of seed delivery in the drill was kept the same and the distance between the drills was the variable for density then with a narrow width of drill (4 in.) the increase in plant density more than offset the fall in capsules per plant.

Further experiments comparing drilling and crossdrilling did not wholly confirm the importance of spatial arrangement. There was, however, evidence that at densities over eighty plants per square foot, besides a further reduction in capsules per plant, the number of seeds per capsule was depressed. Varieties were characterized by differences in seed size, the number of seeds per capsule, capsules per plant and the ability to produce more capsules at high levels of nitrogen. The superiority of the yielding capacity of Royal could be ascribed to the high rate of capsule production. Such varietal differences in capsule production have not been reported previously, and since the number of capsules per plant is greatly influenced by varying density, the common practice of basing selection on spaced plants, may not give a true assessment of capsule formation at densities optimal for seed production.

1. Details are given of the construction of one open-circuit and two closed-circuit respiration chambers suitable for the determination of the 24 hr. exchange of energy of calves or of other animals weighing up to 75 kg.

2. Gas analysis apparatus and the general technique employed in experiments with the closedcircuit apparatus are described.

3. From experience gained with both types of apparatus the closed-circuit apparatus is preferred for its simplicity and ease of working.

1. A survey and. statistical analysis of the records of litters born in the N.I.R.D. herd of Large White pigs over a period of 16 years are presented.

2. The mean length of gestation was 114 days for both gilts and sows.

3. The mean numbers of pigs born alive and born dead per litter from gilts, 10·0 and 0·2 respectively, were both significantly smaller than the corresponding figures for sows, 11·8 and O·8. No seasonal differences were found.

4. The mean total losses of pigs from birth to weaning at 8 weeks were 29·5% of pigs born alive. The losses in litters from gilts, 23·0%, were significantly smaller than in litters from sows, 31·0%. The losses during the winter months both for gilts, 32·5%, and for sows, 35·9%, were significantly higher than during the summer months, 19·4% and 26·7% for gilts and sows respectively.

5. Over 50% of the total losses were due to crushing by the dam, 74·1% of the losses from this cause occurring during the first 48 hr. after birth.

6. The mean number of pigs weaned per litter was 8·0. The difference between the number weaned per litter from gilts, 7·7, and per litter from number of pigs was weaned per litter from sows during the summer months, 8·7, than during the winter months, 7·4.

7. There was no significant difference between the number of male and of female pigs weaned.

8. The mean weight at weaning was 29·9 lb., male pigs, 30·3 lb., being significantly heavier than females, 29·51b. Pigs in litters from gilts, 27·81b., were significantly lighter at weaning than those from sows, 30·0 lb., and for both gilts and sows, pigs reared during the summer months, 29·7 and 31·8 lb. respectively, were significantly heavier than those reared during the winter months, 25·9 and 28·2 lb. respectively.

1. Egg-shells from six inbred lines of Brown Leghorn fowls were examined for porosity and thickness in March and in July.

2. For both characters studied the variation between-line means was found to be significant.

3. The line means for thickness were with a single exception lower in July.

4. Porosity coefficients increased from March to July.

5. No significant relationship between shell thickness and porosity was found in either season. Line differences in porosity values are therefore attributable to variations in other properties of the shell.

1. The relations of yolk, albumen and egg weight were studied in seven inbred lines of Brown Leghorns and reciprocal crosses of two of these lines.

2. In all the lines the eggs produced by hens had a bigger proportion of yolk than those produced by pullets.

3. Besides changes in both components accompanying differences in egg size the line means for albumen weight still differ significantly after adjustment is made for its covariance with yolk weight. This independent variation leads to differences in the yolk-albumen ratio of the hens.

4. Within the lines there is a significant negative association between egg size and the yolk/albumen ratio.

5. The wide differences in egg size, dividing the pure lines into two groups characterized by large and small eggs respectively, resulted from a marked decrease in the amount of albumen in the eggs of the latter group. Yolk weights, on the other hand, could be ranked in a fairly regular series with adjacent lines differing by 2 g. or less.

6. There is some source of variation in the yolk/ albumen ratio for line means which is not accounted for by differences in egg size.

1. An investigation has been made into the changes that take place in the free amino-acid pattern when kale-water slurries are allowed to ferment under conditions of (a) aeration, (b) anaerobiasis and (c) partial sterilization with sulphur dioxide.

2. It has been found that, with aerated mixtures, the loss of free amino-acids is virtually complete within 2 weeks, while there is only a slight loss with the anaerobic mixtures. With mixtures containing sulphur dioxide no loss of amino-acids occur.

3. The formation of α-amino butyric acid possibly from threonine has been noted.

1. The results of six trials have been examined in which pigs received rations with contrasting levels of crude fibre. The contents of crude fibre ranged from 3½ to 11½% and were related to a variety of basal diets.

2. The main object of the trials was to study the effect of increased levels of dietary crude fibre on carcass conformation, under conditions where there was no disparity in rate of live -weight gain between the pigs receiving the higher and the lower level of fibre. Thus pigs on the high-fibre diets received extra food in order to equalize the intake of digestible nutrients.

3. The results indicate that a rise in the level of dietary crude fibre was accompanied by a fall in the killing-out percentage, and hence by lower carcass weights. This effect was produced even by comparatively small changes, such as a rise from 3½% crude fibre to about 5% crude fibre. The results also show that carcass weight was positively correlated with back-fat thickness to a marked degree.

4. It is evident that raising the level of crude fibre in the food caused a change in the distribution of live-weight gains, so that when at the same slaughter weights, the high-fibre pigs had lighter carcasses and heavier offal than their low-fibre counterparts. Consequently the high-fibre pigs also had thinner back-fats, and they would tend to grade better under carcass grading systems based on backfat measurements and biased towards thin back-fats.

5. It is suggested that these effects are likely to be produced even in pigs considerably advanced in fattening, and that in younger pigs the drawback of retardation in rate of live-weight gain may also be encountered. Thus the use of high-fibre diets in self-feeding systems, as a corrective against over-fatness, may not normally be the best means of attaining this objective under commercial conditions.

Part I

1. Reasons are given for expressing the evaporative loss of the resting fowl in the following way:

where C is a constant, f(tr) is a function of rectal temperature, ps is the vapour pressure of a saturated atmosphere at the temperature of the evaporative surfaces, and pa is the vapour pressure of the ambient air.

2. It was found that for practical physiological purposes the rectal temperature may be taken as that of evaporation, from which ps, is deduced. The real temperature of evaporation is probably a few degrees below this, as would be expected.

3. It is concluded from this, that atmospheric humidity hinders the evaporative cooling of fowls less than that of men. Therefore, a farmer cannot estimate the comfort of his fowls in hot weather from his own subjective impressions. The experiments also explain theoretically, why evaporative coolers for poultry houses are successful in practice.

PART II

1. The evaporative loss over a wide range of rectal temperature is plotted in Fig. 1. By applying formula (ii) it was possible to prepare curves for 28 and 5 mm. Hg atmospheric vapour pressure. These vapour pressures are near the extremes of absolute humidity, which fowls naturally encounter in hot climates. Brown Leghorns were used, and it is pointed out that the results with other breeds might not be quite the same.

2. It was calculated that part of the increase in evaporative cooling in hyperthermia is due to the rise in temperature of evaporation. At high rectal temperatures its importance is comparable with that of increased pulmonary ventilation.

3. There was no significant sex difference in the relation between evaporative loss and rectal temperature (Fig. 2).

4. The maximum possible evaporative cooling of fowls in equilibrium with their environment was 41 Kg.cal./sq.m./hr. at a humidity of 28 mm. Hg atmospheric vapour pressure and 64 Kg.cal./sq.m./hr. at 5 mm. This is much less than the maximum attained by man and somewhat less than that of the dog. Although evaporation per unit surface area was less than in the cow, it was much the same in relation to metabolic requirements.

5. Next, certain discrepancies are considered in the relation between rectal temperature and evaporative loss (Tables 3–5). At rectal temperatures near the panting threshold evaporation was found to be greater at high air temperatures and during the night. For the night tests fragmentary data only were available. These findings are tentatively attributed to a lower normal body temperature, which lowered the panting threshold.

In the course of two breeding seasons 261 mature Romney ewes have been employed in three slaughter experiments designed to investigate the manner in which the reproductive performance of such animals, after treatment with a single injection of P.M.S., is conditioned by: (a) the amount of P.M.S. administered; (b) the nutritive status of the treated animals; (c) the stage of the oestrous cycle at which the P.M.S. is administered.

In the first experiment, one untreated control group and three experimental groups of ewes, treated with different amounts of P.M.S., on the twelfth and thirteenth days of the cycle, were used to establish a dose level-ovulation response relationship. Mean ovulation rates and ranges of ovulations observed were: control 1.17 (1–2); 250 i.u. P.M.S. 1.50 (1–2); 500 i.u. P.M.S. 2.07 (1–3); 1000 i.u. P.M.S. 4.33 (1–13).

In the second experiment, oestrous cycle lengths, ovulation and conception rates, and loss of ova during the first few weeks of pregnancy were compared in four groups of ewes that had been treated as follows: (a) neither flushed nor treated with P.M.S.; (b) flushed but not treated with P.M.S.; (c) not flushed but treated with 650 i.u. P.M.S. on the twelfth or thirteenth days of the cycle; (d) flushed and treated with 650 i.u. P.M.S. on the twelfth or thirteenth days of the cycle.

Oestrous cycle lengths were of significantly shorter duration in flushed than in unflushed ewes (0.5 day) and in P.M.S.-treated than in untreated animals (0.7 day). Conception rates were of a normal order in all four groups. The mean ovulation rates of those that conceived at first fertile service were respectively 1.33, 1.61, 1.80 and 1.88. The number of ovulations ranged from 1–2 in the unflushed–untreated group and from 1–3 in each of the other three groups.

In the third experiment results obtained from groups of ewes treated with 650 i.u. P.M.S. on the tenth, eleventh, twelfth, thirteenth and fourteenth days respectively, were compared. Mean ovulation rates were approximately similar in all five groups, but (as was also the case in the second experiment) of a lower order than might have been expected from the dose response curve established in the first experiment. Conception rates were satisfactory after injection on the twelfth, thirteenth or fourteenth days, but unsatisfactory after treatment on the eleventh day, and still less satisfactory after treatment on the tenth day.

From the results obtained in these three experiments the following general conclusions were drawn:

(1) Breed or strain differences may be of considerable importance in governing the extent of the ovulation response following P.M.S. treatment.

(2) The magnitude of the ovulation response to P.M.S. treatment depends to some extent on the ‘batch’ of P.M.S. used and/or the strain of ewes employed.

(3) The nutritive status of ewes during the breeding season is not an important factor in determining the ovulation rate following P.M.S. treatment.

(4) When P.M.S. is administered 5 days or less before the onset of the subsequent oestrus, good conception rates are obtained.

(5) Extremely poor conception rates result where animals are treated more than 5 days before oestrus.

(6) Best ovulation and conception rates are obtained when the treatment-to-oestrus interval is 2–3 days.

(7) For optimum results, treatment on the fourteenth day of the cycle is recommended. However, good results are also obtained after treatment on either the twelfth or the thirteenth days. Treatment on the fifteenth day should also be reasonably satisfactory.

(8) When ovulated in similar numbers, and provided conception occurs, ova produced as a result of P.M.S. stimulation are no more prone to fail to undergo normal embryonic development than are naturally ripened eggs.

1. Four trials on methods of bloat-prevention vare described: (a) A comparison of ‘break’ grazing and normal ‘rotational’ grazing without restriction of feed in either case. Break grazing observations covered two and five breaks per day.

(b) A comparison of these two systems where ‘break’ grazing involved restriction of area available to the cows, and ‘breaks’ varied from seven to eleven per day.

(c) Comparison of ‘off and on’ grazing with normal rotational methods in an attempt to force changes in grazing pattern.

(d) Comparison of the same pasture grazed at different lengths under rotational grazing methods.

2. Grazing behaviour and degree of bloat were noted.

3. In general, the results showed that, irrespective of number of breaks, break grazing with or without restriction gave no effective control of bloat.

4. There were definite indications that a strictly enforced system of ‘off and on’ grazing could afford considerable practical control.

5. Long feed proved definitely safer than feed of the same botanical composition grazed at shorter stages of growth.

6. It was found that cows on potentially dangerous grass had short grazing times with few periods of intense activity. Thus, the oft-stated opinion that bloat is caused by cows eating greedily of dangerous pastures was not substantiated. On the contrary, cows on such pasture showed marked reluctance in their grazing activity.

7. Bloat-producing swards were also associated with reduced rumination time, even in respect to cows showing no symptoms. Bloated cows showed generally very low rumination times.

8. Many of these observations were made on identical twins. From the similarity in their behaviour, it can be concluded that inheritance is an important factor affecting the occurrence of bloat amongst cows grazing the same herbage.

9. In the early stages of bloat, ruminal movement and belching increased in frequency and intensity. This is contrary to the theory that bloat is due to rumen atony. Atony was observed only in the advanced stages of the trouble.

1. A series of observations on the grazing behaviour of identical twin cattle on two contrasting systems of pasture management—rotationally and continuously grazed—is described.

2. The rotationally grazed cows averaged only 11 min. (day/cow) shorter feeding time and 18 min. shorter ruminating time than their continuously grazed co-twins. The total time they spent in work was thus 29 min. shorter.

3. While the average differences in total work over the whole trial was not great, the continuously grazed cows worked for appreciably longer daily periods at the time of seasonal feed shortage during which time the rotationally grazed cows were buffered by their pasture diet being supplemented with silage.

4. The differences in grazing behaviour between the cows of the two treatments, together with the magnitude of the seasonal variations which occurred in both groups, indicated that dairy cows attempt to maintain a stable production in the face of adverse pasture conditions by increasing their feeding time.

5. Previous conclusions based on observations of uniformly treated twins regarding the importance of heredity in the determination of grazing behaviour were fully confirmed.

1. The necessity for further information on the digestibility of heather, with particular reference to the effect of age, has been discussed.

2. The digestibility of well-defined samples of heather of 4 and 10 years of age has been determined.

3. Four-year-old Blackface wethers in crates were fed diets containing 50% of heather and 50% of medium-quality meadow hay.

4. The younger sample of heather was found to have appreciably higher digestibility coefficients for all nutritive constituents other than crude fibre.

5. Agreement between duplicate sheep in respect of their capacity to digest crude protein was found to be good, and faecal metabolic nitrogen outputs were similar.

6. Faecal metabolic nitrogen output was inversely related to the percentage of heather contained in the diet. No relationship between faecal metabolic nitrogen and bulk, as measured on a basis of volume per unit weight, could be established.

7. It has been concluded that heather, though inferior as a source of protein, provides rather more energy than a poor-quality meadow hay, and is thus of value as a winter feed.

1. 101 Rhode Island Red × Light Sussex chickens have been made to conform to four major changes in the shape of their growth curves from hatching to twenty-four weeks, by control of their plane of nutrition. The four treatments (HH), (LH), (HL) and (LL), allowed comparisons to be made between birds of the same age, but different weights. As the main concern has been to find the essential nature rather than the precise extent of the effects produced by different planes of nutrition, the treatment differences were made as extreme as possible without allowing the rations to become unbalanced.

2. Certain individual organs and tissues, the gonads, thyroid and thymus, and the combs and wattles have reacted differentially to the contrasted treatments when compared on a basis of equal body weight. All the organs, with the exception of the very early maturing eyes and heart, have reached significantly different weights on the basis of equal age. Those organs which have yielded treatment differences judged on both the basis of equal weight or equal age have all been late maturing. The results therefore indicate that the effect of treatment has been to restrict the development of the later maturing parts in the case of the low-plane birds, and to accelerate the development of these organs when the birds are reared on the high plane. The results are insensitive to any differential effects which may have been brought about in the early maturing organs, since the design of the experiment did not allow of the slaughtering of birds at equal weight but only at equal age. The means of Comparison of differences at equal weights was the less precise method of ascertaining whether the high- and low-plane regression lines of weight of part to total weight of bird differed significantly the one from the other.

1. Wheats from manurial trials, whose nitrogen contents differed by reason of the fertilizer treatment applied, have been used as the sole source of protein in rat-feeding experiments.

2. Pairs of rats given such diets have shown increased growth when fed wheat of higher nitrogen content.

3. Measurement of the ratio of growth rate to nitrogen ingested, suggests that the difference obtained is due, not to increase in the acceptability of the diet, but to the greater nutritive value of the grain from the manurial plots.