1. The metabolic interactions of casein and starch or other carbohydrates are measured by estimating the concentrations of volatile fatty acids, ammonia, lactic acid and amino acids in the rumen after administering the protein and carbohydrate supplements alone or together.

2. The ammonia concentration is reduced (i.e. its utilization is probably increased), by the carbohydrate materials; levan and starch achieve this slightly more effectively than glucose or xylan and the effect of cellulose is very slight.

3. Under conditions when the normal ration fed is not of high quality a small supplement of casein stimulates the rate of fermentation of starch and other carbohydrates.

4. The findings indicate that the best utilization of protein supplements is probably obtained when a carbohydrate is also present that can be fermented at a comparable rate, conditions which stimulate microbial synthesis in the rumen.

An experiment is described in which 64 individually-fed pigs were used to investigate the effects of dietary protein status, administration of aureomycin and hexoestrol implantation on growth, efficiency of feed utilization and carcass conformation. The results of hexoestrol implantation and interactions with the other two variables only are reported here. The pigs were implanted at 120 lb. and again at 150 lb. and killed at 200 lb. live-weight.

The main features of hexoestrol treatment were:

1. Body length taken from the anterior edge of the aitch bone to the junction of first rib and sternum was significantly increased by 9·75 mm.

2. The percentage lean in the carcass was increased by 0·82%, representing approximately 1¼ lb. more lean meat in a 155 lb. carcass. The water content of the lean was increased but not significantly.

3. Body fat was reduced but this was not reflected in a significant change in back fat measurements.

4. No changes could be detected in the thyroid or adrenals, but whereas male castrates showed little effect of treatment on other organs apart from a certain amount of urethritis, the intact female manifested major changes in the genital tract. The uterus in particular was greatly enlarged and ovarian activity obviously reduced. The implications of these effects are being examined.

5. There was no response to treatment in terms of growth rate or efficiency of feed utilization.

A close relationship has been found between the decomposition of feeds in the macro-respirometer and their digestibility. The degree of nitrogen mineralization appears also to conform with certain aspects of protein digestibility. The various relationships are sufficiently close to suggest that the macro-respirometer can be used in a preliminary assessment of the digestibility of feeds.

An investigation has been made on the changes in the haemoglobin index with age in four breeds of indigenous African and two breeds of European cattle.

1. Support is given to previous findings that the haemoglobin index was high and variable at birth and fell to an individual more stable adult level at between 2 and 3 years of age.

2. The haemoglobin levels for mature animals of the four tropical breeds are higher than mean figures quoted for other tropical cattle, but still fall within the ranges quoted.

3. The haemoglobin levels for the Friesian agreed with those quoted from temperate regions, but those for the Jersey were higher, agreeing most nearly with Jamaican figures. A reason for this is advanced.

4. The haemoglobin levels of the tropical breeds were significantly higher than those of the two temperate breeds examined.

5. Confirmation was given to the association of a high haemoglobin index with a high heat toleration coefficient.

1. An experiment with one non-laying and four laying hens was carried out. Food and water consumption was measured hourly from 06.00 to 22.00 hr. and in the same period the exact time of each excretion was noted. Determinations of water and dry matter were made on each separate excretion.

2. Each bird showed a typical pattern of behaviour in relation to the time of day when it ate food and drank water. For any one bird, variations of this pattern from day to day were small.

3. For each bird there was a highly significant relationship between water intake and temperature on the one hand, and water excretion via droppings and eggs on the other. Water intake, however, had a far greater influence than had temperature on water output.

4. Calculations showed that, despite errors caused by not knowing the amount of metabolic water produced, the excretion from the lungs varied greatly from bird to bird on constant intakes of water and also in the same bird at different intakes.

1. The effect upon the carcass characters of indigenous steers of supplementing veld grazing with two levels of salt with and without protein in the dry season has been investigated.

2. The feeding of 1 oz. of salt, found in part I (Walker, 1958) to speed up growth to a significant degree, was shown also to have speeded up maturity in carcass characters.

3. No benefit was obtained from adding a dry season protein supplement to the salt; the feeding of protein without salt produced only slight insignificant effects.

4. The addition of 2 oz. supplementary salt noted in part I as having an inhibitory effect on growth by comparison with the lower salt level has been shown to extend to the carcass characters.

5. Additional evidence has been found in the carcass characters to give further support to the suggestion that the tropical indigenous animal possesses the capacity for stopping growth during adverse nutritional conditions and continuing again afterwards.

1. The frequency of excretion of droppings by hens varied considerably over the day and much of this variation appeared to be related to the disturbance of the birds by attendants.

2. Data relating to dry-matter excretions by five birds for 17 days were used to study the influence of zero hour and length of the time unit on variations in this dry matter.

3. It was found that, in this experiment, 14.00 hr. appeared to be the best zero hour, but it was suggested that, considering the heavy excretion of material around 06.00 hr. when the birds are first disturbed in the morning, 07.00 hr. might be the ideal time. Data from an earlier experiment supported this.

4. There was a decrease in variation up to a unit of time equal to 3 days and times not multiples of days gave greater variations. There were, however, considerable differences between birds.

1. Experiments were carried out in 1956 and 1957 in which milking cows were grazed at the same stocking rate, either on strip grazing or on free grazing. The cows followed balanced Latin Square designs.

2. The pastures were liberally fertilized, either with NPK fertilizer (202 lb. N, 202 lb. P2O5, 252 lb. K2O per acre in 1956 and 80% of these quantities in 1957), or with PK fertilizers (269 lb. P2O5 and 269 lb. K2O in 1956 and 80% of these quantities in 1957), and a subsidiary comparison of the effect of nitrogenous fertilizers was made in 1956.

3. At the end of the main experiment in 1956 a study of the effect of straw offered to the grazing cows was made. No supplement other than straw was offered.

4. The results in both years showed no difference in milk yield per cow due to treatments, nor in 1956 was milk yield or milk composition affected by grazing treatment, fertilizer treatment or the provision of straw.

5. In both years the live-weight gain per cow was less with free grazing. In 1956 the provision of straw increased the rate of live-weight gain. It is suggested that these differences are mainly due to gut fill.