1. Injections of 32P and 45Ca were used to study the influence of phosphorus depletion and repletion on the rates of endogenous calcium and P excretion in fifteen P-depleted and eighteen control sheep. 2. When given adequate P, there was a marked increase in the rate of excretion of metabolic faecal P in sheep which previously had been depleted. In control sheep a decrease was found in metabolic faecal P excretion with a diet deficient in P. 3. From the values for metabolic faecal P an indirect estimate of total intestinal secretion was made. The estimate was found to be in approximate agreement with values derived from published values for total daily digestive secretions in sheep. 4. The estimated rates of secretion of intestinal P suggest that after the addition of P to the diet the changes in the rate of excretion of metabolic faecal P in P-depleted sheep were the result of a decreased reabsorption of intestinally secreted P rather than of a change in the rate of secretion into the intestine. After a diet low in this element the decrease in metabolic faecal P excretion by control sheep appeared to be the result of a decreased rate of intestinal P secretion. 5. The possible significance of changes in metabolic faecal P excretion in relation to body P homoeostasis in the ruminant animal is discussed.

1. Sheep fitted with rumen cannulas were fed at hourly intervals by an automatic feeder in a controlled environment and the contents of the reticulo-rumen were removed at intervals of 6 h, 30 min after the previous feed. 2. No diurnal variation was found in the total contents or in the quantity of dry matter, organic matter and nitrogen. 3. Nine dried pasture herbages containing 0.79–3.69% N in dry matter were given automatically at a high and a low level of feeding. Feeding at the high level increased the total weight of the reticulo-rumen contents, total dry matter, organic matter and N and also the dry-matter percentage. 4. Apparent retention times were calculated by dividing the quantity of organic matter or N in the rumen by the quantity given each hour. Organic matter was retained for 10.2–24.9 h and N for 12.0–61.4 h. 5. The apparent retention times for both organic matter and N were reduced when the level of feeding was raised.

1. Two sheep were given cubed rations in which the fatty acid content was increased by about 12 g/day at the end of each week, until the daily intake became 74 g. 2. The apparent digestibility of the crude lipid increased with the increased intake, but there was no tendency for the digestibility of the fatty acids to increase or decrease regularly. 3. Comparison of faecal losses during the final periods, when a maximum amount of lipid was given, with the losses during the initial control periods showed that the excretion of dry matter, crude lipid and cellulose increased. The excretion of crude protein was unchanged and that of lipid- and cellulose-free dry matter decreased. There was a reduction in the production of methane of 17 kcal/100 kcal of additional fatty acids in the diet. 4. The concentration of the C18 unsaturated acids in the rumen liquor reached a maximum during the 1st week on the diet containing the maximum amount of added fatty acids. The shape of the curves was consistent with rapid hydrogenation of linolenic acid. The concentration of stearic acid in the rumen liquor reached a maximum when the dietary acids increased to only 50% of their maximum value.

Phytanic acid, 3,7,11,15-tetramethylhexadecanoic acid, which hitherto had been isolated and identified from several natural sources including butterfat, ox perinephric fat and cow plasma, has now been found present in small amounts (2·9%) in the total fatty acids extracted from the rumen bacteria of a fistulated dairy cow fed a diet of clover-grass hay. This C20 multibranched fatty acid was not detected in the dietary clover-grass hay, and it is considered to have been derived from phytol by enzymic activity of the rumen bacteria.

An antibiotic produced by coagulase-negative staphylococci isolated from the bovine udder was examined by deferred antagonism tests and its inhibitory properties compared with those of other staphylococci. While inhibiting the growth of representative phage types of bovine pathogenic staphylococci, its activity against corynebacteria was more restricted than that of Staphylococcus aureus NCTC 6507 and 8004. Only minimal amounts of inhibitory substance were produced in liquid media, larger amounts were produced on solid media and the incorporation of a blood plasma factor further increased production. The inhibitory substance resisted treatment with pepsin and trypsin and withstood boiling for 30 min. Its characters in relation to inhibitory substances produced by other staphylococci are discussed.

Using several milk supplies, a comparison has been made between the amount of deposit formed under standard conditions in a small plate type ultra-hightemperature heater, and the results from the hot-wire laboratory apparatus described previously. It is shown that the laboratory apparatus reproduces the variations in the sensitivity to deposit formation found using the plate heater. The relationship is linear if the criterion derived from the hot-wire results is taken as the square of that proposed previously. A decrease in the sensitivity to deposit formation during the ageing of fresh milk, and a seasonal variation, are indicated.

Injections of l-thyroxine into normal dairy cows at the beginning of lactation resulted in animals fed on a high protein diet becoming ketotic. Some of the symptoms observed in the induced ketotic cows showed many similarities when compared with those associated with the spontaneous condition.

In most cases the levels of the constituents estimated in the blood of the induced ketotic cows were similar to those measured in blood from spontaneous cases. A histological examination of the liver from an induced ketotic cow showed a considerable increase in the fat content, particularly in the centrilobular regions. The fat content of this tissue amounted to 26% with a concomitant depression of liver glycogen to only 10% of the normal level.

Diet was found to play an important role in the susceptibility of cattle to the induced ketosis, since animals fed on rations containing a lower level of protein were more resistant. Attempts to induce ketosis in cows 6—8 months after calving were completely unsuccessful.

The part played by the thyroxine and the diet in the induction of ketosis is discussed.

The viscosity of cream increased with increasing fat content, and higher values were obtained if the cream was separated at 38–43 °C rather than above 55 °C, and if the cream was cooled to below 15 °C before storage at 20 °C. The ‘type’ of viscosity varied with cooling and storage conditions; for example, cream cooled below 20 °C and stored at 20 °C gave increased viscosity readings with increased rates of shear due to churning of the cream, while the behaviour of cream cooled only to 20 °C was Newtonian.

Cream stability as measured by free fat content decreased with increasing fat content above about 42%, with low temperature separation (38–45 °C), with cooling to below 15 °C before storage at 20 °C, and with increased pressure at temperatures below 15 °C.

Dilatometric study of the amount of fat crystallization indicated that larger amounts of crystallization resulted in higher final viscosity and free fat content.

The fatty acid composition of colostral and milk fat samples representative of the total secretion of the nursing mammae of each of 3 sows was determined by gas-liquid chromatography. In both colostral and milk fats, acids of chain length C16 and C18 accounted for more than 90% of the total fatty acids present; colostral fat contained a higher proportion of oleic acid and linoleic acid and less palmitic acid and palmitoleic acid than normal milk fat. Structural studies on milk triglycerides showed that, as in pig depot fat, palmitic acid is preferentially esterified to the secondary alcoholic group (2-position) of the glycerol molecules with the C18 acids (stearic, oleic and linoleic acids) being present for the most part in the 1- and 3- positions.

Fifty-nine strains of pediococci were isolated as representing the predominant non-starter flora in a series of Cheddar cheeses made over a period of 5 months. All strains had the same physiological characteristics and were identified as Pediococcus cerevisiae. A common antigen was found in 54 of the strains, whereas in the other 5 the antigenic component appeared to be related but not the same. Both antigens were located in the cell wall.

All the strains required folinic acid for growth and it was shown with one strain that the small amount of growth which occurred in sterile milk was greatly increased by the presence of the folinic acid producing starter Streptococcus cremoris 924.

Coagulase-negative staphyloccoci were isolated regularly over a period of 39 weeks from quarter milk samples of 18 cows belonging to one herd. They did not produce a leucocytosis in the milk or high anti-haemolysin titres in the blood of these cows, but such responses occurred in 2 cows infected with pathogenic staphylococci. The coagulase-negative variety was found to colonize the teat duct and surface of the teat in preference to the milk and possessed greater resistance than pathogenic staphylococci to certain long-chain fatty acids. Infection with coagulase-negative staphylococci was thought to antagonize the colonization of the udder by a pathogenic variety present in the herd; 23% of the coagulase-negative strains were found to elaborate an antibiotic substance inhibitory to the growth of a coagulase-positive staphylococcus. Coagulase-negative strains were characterized by the production of ɛ-toxin and could be divided into 3 main groups according to their effect on gelatin, mannitol and phenolphthalein diphosphate as substrates.

Strains of Lactobacillus bulgaricus and Streptococcus thermophilus isolated from yoghurt culture were used to study the cause of the synergistic effect on acid production by mixtures of the 2 cultures. The beneficial effect was essentially limited to the gradual accumulation of factors in the L. bulgaricus cultures that promoted more rapid acid production by Str. thermophilus. The active factors were identified as glycine and histidine.

The entry into milk from blood of N-acetyl-4-aminoantipyrine (NAAP) and urea, compounds known to be distributed evenly throughout the whole of body water, and thiocyanate and thiosulphate, the distribution of which is confined largely to extracellular fluid, has been investigated. The concentrations of NAAP and urea in blood and in milk were similar, but the concentrations of thiocyanate and thiosulphate in milk were much lower than the concentrations in blood plasma. A progressive increase in the ratio of the thiocyanate concentration in milk to that in blood occurred with advancing lactation and marked variations in the thiocyanate ratio of the milk of the separate quarters were observed in some cows, and these variations in the ratio were closely related to variations in the chloride content of the milk; similar inter-quarter variations in the ratio for NAAP were not observed. With NAAP, there was a continuous equilibrium between blood plasma and milk within the udder, whereas with thiocyanate the content in milk after its secretion into the ducts and cisterns of the udder appeared to be largely independent of later changes in the concentration of thiocyanate in blood plasma. These results are discussed in relation to the secretion of chloride in milk.

Casein derived from the micelles of milk by removing the calcium has been subjected to partition and counter current distribution between phases containing polyethylene glycol and dextran. The results show that at least 2 kinds of casein complex exist which differ in structure, in size or in both. There are also differences in composition with respect to minor components, though both types contain predominantly α- and β-casein.

1. Susceptibility to dietary induction of hypercholesterolaemia and aortic atherosis was compared in two groups of male New Zealand White rabbits. 2. Twelve rabbits were purchased from one breeding establishment (group I) and twelve from another (group 2). On arrival at the laboratory six animals from each group were killed and the aortas were removed. Blood samples were taken from the remaining twelve animals and then they were given ad lib. for a period of 40 weeks an atherogenic diet containing 20% butterfat. During this period food intake and body-weight were recorded. At the end of the period blood samples were taken from the animals and immediately afterwards they were killed and the aortas were removed. 3. No atheromatous lesions were found in the aortas of the rabbits in either group killed at the beginning of the experiment. There were no differences between the two groups of animals with respect to body-weight or concentration of cholesterol in the plasma at the beginning of the experiment, food intake during the experiment or body-weight at the end of the experiment. At the end of the experiment, the degree of aortic atherosis in the rabbits of group I was considerably greater than that in the rabbits of group 2. 4. At the end of the experiment the concentrations of total lipids, free cholesterol, esterified cholesterol and phospholipids in the plasma of the rabbits in group 1 were significantly higher than the corresponding concentrations of these lipid components in the plasma of the rabbits in group 2. The concentrations of palmitic, stearic and linoleic acids in the cholesterol esters and the concentration of palmitic acid in the unesterified fatty acids in the plasma of the rabbits in group 2 were significantly higher than the corresponding concentrations of these fatty acids in the plasma cholesterol esters and unesterified fatty acids in the rabbits of group 1. 5. It is concluded that these differences in response to the atherogenic diet were reflections of the differences in the susceptibilities to the dietary induction of hypercholesterolaemia and atherosis of the two differents strain of rabbit that had been established by the two commercial breeders. Such differences in susceptibility could readily explain certain discrepancies in the results of various research workers engaged in this field of investigation.

1. The relationship of vitamin A and carotenoids with encephalomalacia was examined in chick-raising farms and under laboratory conditions. 2. In encephalomalacic chicks on the farms a significant decrease in liver carotenoid content was demonstrated. In the diseased chicks the carotenoid contentwas below 0.30 mg/100 g liver, as against the normal values of 0.40–1.0 mg/ 100 g. 3. Under experimental conditions incidence of encephalomalacia could be decreased by oral treatment with the synthetic carotenoid ethyl β-apo-8'-carotenoate. This implies that deficiency in carotenoid is not merely a concomitant sign of encephalomalacia, but has also a causative role, as sufficient carotenoid reserves confer a certain protection against the disease. 4. The pathogenetic role of carotenoid metabolism in encephalomalacia was supported by certain observations. Factors inhibiting the accumulation of ethyl β-apo-8'-carotenoate in the liver predispose chicks to the disease. In chicks 4–5 weeks old in addition to those with vitamin A reserves higher than 800 i.u./g liver, the accumulation of carotenoids in the liver was about 10% of that measured in chicks more than 7 weeks old, or in those with vitamin A reserves not higher than from 100 to 200 i.u./g. In fact, encephalomalacia occurs mainly among chicks 3–5 weeks old. Also, reserves of vitamin A exceeding 800 i.u./g liver were found to predispose chickens to encephalomalacia.