1. Data from twenty-four short-term trials on the nutrition of dairy heifers have been used in a study of the effects of management, method of estimation of live-weight gain, length of experimental period, covariance analysis and the use of monozygous twins upon experimental error.

2. The value of rigid adherence to a routine and allowing ample time for the animals to settle down before the trial have been demonstrated.

3. Error standard deviations were associated with length of experimental period, those for 42-day periods being about half those per 21-day periods, but were not appreciably correlated with initial live weight.

4. No advantage could be demonstrated for the use of monozygous twins, or covariance analysis with initial weight or rate of gain, indicating that genetic effects contributed little to the error in experiments lasting 3–6 weeks.

5. There was no significant difference between errors in live-weight gains calculated from the regression of live weight on time, from single initial and final weights, or from two initial and final live weights, indicating that deviations from linear regression are not solely in the nature of random day to day fluctuations in live weight.

The effects of air temperature (30–70° F.) and live weight upon the water consumption of dairy heifers from 350 to 550 lb. live weight have been studied together with the amount drunk in different periods of the day. The water consumption increased by 0·03–0·06 gal./° F. rise in temperature and by 0·0075 gal./lb. increase in live weight. Most of the water consumption occurred during meals.

The effect of selection of dairy bulls on their daughters' 1st lactation yields has been investigated, using contemporary comparison information availreable for some 1273 bulls. It was shown that incomplete repeatability of individual records would introduce a negative bias into the regression of the increase in production of a bull's daughters with age on his contemporary comparison and this bias was calculated. The observed regressions on 1st lactation contemporary comparison were close to zero after correction for bias both for increase from 1st lactation yield to 2nd (— 0·08) and for the increase from 2nd lactation to 3rd (+ 0·09). Selection on 1st lactation yield should not, therefore, change the increase of yield with age, in agreement with results of other workers. The results are related to the problem of the heritability of the separate lactations.

1. In the 1954–5 and 1955–6 breeding seasons, 117 ewes of the Border Leicester, Welsh Mountain and Suffolk breeds were used in order to investigate the effects of PMS treatments on (a) the length of the dioestrous cycle, (b) the number of ovulations per ewe, (c) the proportion of eggs which were cleaved, uncleaved or abnormal when recovered, and (d) the ability of fertilized superovulated eggs to develop normally.

2. In the 1954 and 1955 anoestrous periods, ninety-four 2-tooth and mature ewes of mixed breeds were used in order to investigate (a) the proportion of ewes which could be induced to ovulate and exhibit oestrus as a result of treatment with progesterone and PMS, (b) the proportion of the mated ewes which had cleaved, uncleaved or abnormal eggs, and (c) the ability of fertilized eggs shed during anoestrum to develop normally up to the 21st day of pregnancy.

3. Dioestrous cycles in untreated ewes were significantly shorter for Welsh Mountain than for Border Leicester ewes, and their length was not affected by the year in which they were measured. The first and second cycles of the breeding season tended to be shorter than the third cycle.

4. The length of the dioestrous cycle was shortened by treatment of both Border Leicester and Welsh Mountain ewes with PMS. The average extent of this reduction was 0·6 days, and the effect was significant.

1. A detailed analysis was made of the rumination behaviour of one caged sheep on four combinations of diet, ranging from 100% hay to 100% concentrate meal.

2. When hay was fed there was no relationship between the quantity of it ingested and the amount of rumination, which averaged 8 hr. daily. When concentrates were fed alone rumination time fell to 2½ hr. per day and much of this was ‘pseudorumination’.

3. Evidence is produced to show that the number of chews and not the time chewing is the accurate way of measuring rumination quantitatively. This particular sheep made an average of 39,000 rumination chews per day when hay was fed.

4. The duration of the intervals between boli was constant at 15% of total rumination time, but the rate of chewing varied from 83–99 chews per minute, being slower during the midnight to noon half of the 24 hr., when most rumination occurred.

5. Rumination periods last from under 1 min. up to about 2 hr.

6. Tiring during a rumination period was reflected by an increase in the intervals between boli but the number of chews per bolus remained unchanged.

7. The first bolus of each period of rumination was chewed less than those following. This sheep averaged fifteen periods of rumination per day, a daily total of 500 boli were regurgitated. There were 2500 chews per period and seventy-eight chews per bolus.

A series of seven experiments were carried out between May and September 1954 at the Grassland Research Institute as part of a co-operative study of bloat, which the Agricultural Research Council had helped to organize.

Hereford colour-marked steers were grazed or fed on legume-dominant herbage in an endeavour to produce pasture bloat. Observations were made to determine patterns of animal behaviour and bloat incidence. Heart rates were determined both before and during the experiments and jugular blood samples were taken for determination of cholin-esterase levels. Herbage samples were analysed botanically in order to determine the type of material eaten, and chemically for nitrogen content. Other herbage samples were placed in cold storage.

In the seven experiments (375 cattle feeding or grazing days) only twenty-seven cases of mild bloat and five cases of moderate bloat were recorded. This is surprising, because pains had been taken to provide feed that would by all normal standards be regarded as likely to induce bloat in cattle.

1. Field trials with gibberellic acid on grass, wheat, potatoes, turnips, carrots, peas, runner beans, lettuce, celery, blackcurrants, kale and maize are described. The effects on plant growth and crop yield were determined.

2. The experiments on grassland were carried out between July 1953 and June 1956, and included trials at four different centres. They all gave essentially similar results.

3. 2 oz. per acre of gibberellic acid sprayed at 100 gal. per acre stimulated the growth of all components of the swards. The stimulation was most clearly seen in spring and autumn when the natural growth rate was slow. At these times gibberellic acid was able to produce a grazeable growth of grass more rapidly than nitrogenous fertilizers. The stimulation of growth was accompanied by yellowing of the grass, but recovery to a normal green colour was speeded up by applying a nitrogenous fertilizer at the same time as the gibberellic acid spray.

4. The dry-matter yields at the first cut following a treatment with gibberellic acid were increased by 0·6–10·8 cwt. per acre. The crude protein yields were also increased by the treatment, but to a relatively smaller degree, and the protein content of the grass was reduced by between ½ and 2%. The contents of phosphorus, potassium, sodium, calcium, barium, magnesium, manganese, copper, aluminium and tin were not altered.

1. Ammoniated invert molasses when used as a food for yearling dairy cattle proved toxic in doses of 1 lb. per day.

2. When ammoniated invert molasses had been acidified with phosphoric acid the toxicity was markedly reduced but not entirely eliminated. Ammoniated molasses acidified with acetic acid produced no toxic effects but the live-weight responses of yearling cattle was inferior to a ration markedly deficient in protein. The poor responses may have been partially due to the unpalatability of the ammoniated molasses.

3. The ammoniated molasses used in experiment 1 did not produce toxic symptoms in rats but it did result in reduced food consumption and poor growth.

4. The ammoniated molasses treated with acetic acid, when included at the rate of 10% of the diet of guinea-pigs, depressed appetite and caused toxic effects.

1. An attempt was made to verify a report that mixed samples of bull semen show better motility and survival than their unmixed controls.

2. The claim was not confirmed; in 83 of 104 samples the motility score of the mixed sample was less than the score for the better individual constituent sample.

Leaf-rust infection of severity 3–4 on the modified Cobb scale reduced the dry-matter yield of Dun oat leafage by 30% and N.I.A.B. ryecorn by 23%. The reduction in root growth of ryecorn was similar to that of the aerial parts.

The dry-matter percentage of the green forage was significantly increased in two of the three experiments. Palatability reduction due to leaf rust is suggested from field observations.

With Dun oats leaf-rust infection increased the percentage of crude protein (C.P.) by a fifth, of ash by a tenth and decreased that of crude fibre (C.F.) by an eighth, and of nitrogen-free extract (N.F.E.) by a nineteenth. With ryecorn, rust increased the percentage of c.p. by a fourteenth, of ash by a fifth, and decreased that of N.F.E. by a twentieth.

The decreased forage yield caused by rust is in accord with the results of experiments of other research workers and with field observation. The effect of rust on proximate constituents was interpreted as an improvement to feed value. This agrees with the results of most reported experiments but conflicts with the field evidence.

The hypothesis that leaf rust affects forage composition mainly by reducing the physiological age of cereals is proposed.

Three calves (Australian Illawara Shorthorn, Shorthorn and Zebu × Australian Illawara Shorthorn) were exposed to different combinations of wet- and dry-bulb temperatures in a psychrometric chamber at the Physiology Department of the University of Queensland. These animals were 2–3 months old when first exposed to heat.

Measurements were made on these animals for cutaneous and respiratory water losses, and skin and rectal temperatures.

Cutaneous water losses in all the animals studied increased with increases in air temperature. Comparing these results with those on men with congenital absence of sweat glands exposed to high air temperature below the sweat point, suggests that the cutaneous evaporative losses in cattle are more than those that can be accounted for by diffusionmoisture alone.

Increase in cutaneous evaporation under hot conditions is accompanied by increase in skin and rectal temperatures. In the Zebu cross, however, the skin temperature did not rise with rise in air temperature.

Keeping the humidity constant, rise in dry-bulb temperature caused increase in respiratory water loss. On the other hand, rising humidity at a constant dry-bulb temperature resulted in decrease in respiratory evaporation. Respiratory evaporative loss was, therefore, greater in hot-dry than in hot-wet conditions.

The soil nitrate content has been determined at fortnightly intervals on bare fallow plots and on plots under crops and natural vegetation in the forest and savannah regions of Ghana. Nitrifiable nitrogen, ammonium and soil moisture contents have also been determined. It has been found that the changes in nitrate content are related to changes in the content of nitrifiable nitrogen. During the dry season, a partial sterilization of the soil occurs and consequently the content of nitrifiable nitrogen rises. This nitrifiable nitrogen is slowly converted to nitrate in the dry season and rapidly converted once the rains commence. Nitrate is then lost from the soil by leaching and denitrification. Under bare fallow conditions leaching is the most important cause of nitrate loss, but it is probable that denitrification makes some contribution on cropped soils and those under permanent vegetation. There is no indication of microbial nitrate absorption under a crop. This is presumably due to the rapidity with which nitrate is lost by leaching and denitrification, and to the greater quantity of organic matter required in these free-draining tropical soils than in most temperate ones to produce an equivalent absorption of nitrate. The high levels of nitrate and nitrifiable nitrogen which are found under natural forest probably represent an equilibrium level typical of a cycle in which nitrogen fixation and nitrification as well as nitrate losses proceed very rapidly. Natural savannah grassland suppresses nitrogen mineralization in the field almost entirely, but the nitrifiable nitrogen content is at times high, in spite of the very high carbon/nitrogen ratio of the soil of over 20. This confirms the view that little nitrate absorption takes place in spite of the presence of what might be considered excess carbonaceous material. The suppression of mineralization under grass is considered due to an excretion of the plant roots which is toxic to the nitrification process. The failure of organic matter to build up in these savannah soils, although mineralization is suppressed, is most probably associated with their low general fertility.

1. The effect of different levels of protein on the digestibility of the carbohydrate fraction of two compounded diets which differed widely in their contents of indigestible organic matter has been determined.

2. Digestibility of the available carbohydrate (the sugars, dextrins and starches expressed as starch) apparently increased with increase in the protein content of the diet.

3. Alteration in the cereal portion of the diet involves an adjustment in the amount of protein supplement if the nutritive ratio is to remain unaltered.

1. The efficiency of food utilization for egg production by pullets has been determined for two diets, one high in energy and the other low.

2. Both groups laid at the same rate (245 eggs/bird) throughout the year.

3. Birds fed the low-energy diet ate more food, but the intakes of digestible protein, non-protein digestible energy and metabolizable energy were the same for both groups.

4. The cost of food perton was higher for the high-energy diet; per bird per year it was the same for both groups.

The results of an interim examination of the experiments at Rothamsted and Woburn on the effects of nitrogen, phosphate and potash on a six-course rotation of crops are reported.

It has become apparent that the main aim of the experiments, to relate the effects of the fertilizers to weather conditions, is not being fully realized. This is in part a consequence of the design, which has inherently low accuracy and results in low responses to phosphate and potash. In addition, faulty randomization and, at Woburn, fertility irregularities and pest damage have further reduced the accuracy attained.

The faulty randomization also seriously affects the estimates of experimental error given by deviations from smoothed response curves. Alternative estimates of error are provided to overcome this difficulty.

The mean yields and mean standard responses over the period 1931–55 are presented.

There is very little year-by-year variation in the responses to phosphate, but the responses to nitrogen and, for some crops, the responses to potash show sufficient variation to justify further analysis. As a first step the regressions of the responses to nitrogen on winter rainfall and on rainfall during the growing season and, for the root crops only, the regressions on sowing or planting date are briefly considered.

The coat changes of an experimental group of four undernourished Shorthorn heifers have been compared with those of a control group of four well-fed heifers.

Low nutrition impeded seasonal shedding in three of the four experimental animals, and the hair which was retained into the summer months appeared lifeless and bleached. One animal's hair and shedding were normal, despite low nutrition.

Two animals of the control group also partially retained their hair in the summer, but it was of normal colour, good lustre, and vital appearance.

It is concluded that plane of nutrition influences shedding, though some individuals within a breed are less affected than others. Two distinct varieties of coat retention were observed: one was of nutritional origin, the other inherent. Possible explanations of the differences are suggested.

Coles (1957) has reported the results of a hatchability trial in which four pens of hens each received 10% of a different sample offish meal (A–D) in their diet as the only experimental variable. There was a high level of egg production in each pen, but differences in hatchability as indicated in Table 1. The pen with lowest hatchability received fish meal D, which was darker in colour than the others. It was suggested that this might indicate a scorching of the meal with heat damage, and that in turn this might be responsible for the lower hatchability. The meals have now been analysed to investigate this point.