Ten-day periods of water restriction followed by 2 h ad lib. water caused radical changes in camel milk. The changes were different from those reported in other mammals. At the end of each dehydration period there were increased water percentages in the milk when compared with milk of hydrated camels. The content of fat, lactose and protein declined. Concentrations of Na, K, phosphate and chloride in milk increased while Ca and Mg concentration declined. The urea concentration of the milk was unchanged. The young suckling calves showed no signs of stress during the dehydration periods. It was concluded that the milk of dehydrated camels is an excellent human food in arid areas, as the water and salt content are high while the nutritive value remains good.

Electronic somatic cell counts (ESCC) and relative cell volume distributions (RCVD) in milk samples were obtained simultaneously on a Coulter Counter Model TA and their potential assessed, either singly or in combination, for identifying mastitic quarters and cows in 2 herds. Using log (ESCC) alone the probability Pm of misclassifying quarters infected with major pathogens was 6–7 % for herd 1 and 18–1% for herd 2. The inclusion of RCVD variables with log (ESCC) did not substantially improve the chance of detecting quarters infected with major pathogens. However, the RCVD variables did improve the chance of identifying quarters infected by major and minor pathogens compared to the use of log (ESCC) alone, the Pm figures being reduced by about one third.

When testing composite quarter samples, where milk from infected quarters was diluted with that from uninfected quarters, the inclusion of RCVD variables decreased the Pm compared to the use of log (ESCC) alone. In herd 1 the improvement was from 26–1 to 3·0 %, while in herd 2 the effect was less marked, the Pm being reduced from 28–6 to 21–6%. However, as the RCVD assessment is provided simultaneously with ESCC, the additional information is obtained at minimal cost.

135 Cows which were expected to produce a second or subsequent calf within 4–11 d received an intramuscular injection of 500 μg lα-hydroxycholecalciferol (lα-OHD3). In those animals in which the interval between injection and calving was at least 7 d there was, at 7 d after injection of lα-OHD3, a significant increase (P < 0.001) in the blood plasma concentrations of Ca and Pi and a significant reduction (P < 0.05) in that of Mg, compared with those in control animals. Within 24 h of calving there was a significant increase (P < 0.001) in the concentration of Pi but no change in Ca or Mg compared with pre-injection levels, whilst the control animals showed a significant fall (P < 0.001) in the concentration of Ca and a rise in those of Pi (P < 0.001) and Mg (P < 0.05). There was a significant reduction (P < 0.001) in the number of animals with hypocalcaemia (defined as a plasma Ca concentration <1.9 mmol/1) in all animals injected with lα-OHD3; this reduction was particularly marked when the interval between injection and calving was between 1 and 8 d. The previously reported reduction in the incidence of clinical milk fever is considered to be a consequence of the effect of lα-OHD3 on the concentration of Ca in plasma.

The localization of glycosylated k-casein in isolated bovine casein micelles was investigated at the ultrastructural level with gold granules labelled with the Ricinus communis lectin specific for galactose. No evidence was obtained for the presence of glycosylated k-casein on the surface of glutaraldehyde-fixed micelles whether or not they had been treated with neuraminidase. Glycosylated k-casein was mainly located in the bridging network interconnecting the micelles and appeared to be loosely associated with the micelles. When thin sections of micelles were marked, no clear-cut evidence was observed for the presence of intramicellar glycosylated k-casein.

The formation of lysinoalanine, N-є-(2-amino-2-carboxyethyl)-L-lysine, by treatment of αs0-, αsl- and β-casein with alkali, has been studied. In all 3 proteins lysinoalanine was formed by reaction of lysyl residues with dehydroalanyl residues produced by alkaline degradation of those phosphoseryl residues which occupy isolated positions in the proteins' structures. The contribution to lysinoalanine production made by phosphoseryl residues which were arranged in clusters, as occurs in the sequence -Ser(P)-Ser(P)-Ser(P)-, was not significant.

The heat stability of a standard reconstituted skim-milk preparation has been investigated as a function of pH, temperature of coagulation, and forewarming treatment. Apparent activation energies have been calculated from the temperature dependence of coagulation time, and a constant value of 144 kJ/mole has been found for milks between pH 6·6 and 6·9. The effect of forewarming resulted in a decrease in stability at the most acid pH values, a slight increase at higher pH but below the pH maximum, and a decrease in the region of the pH minimum. A working hypothesis is proposed for the mechanisms leading to the coagulation of milk at elevated temperatures, based upon Ca induced precipitation of casein, protein polymerization, β-lactoglobulin: κ-casein interaction, and precipitation of insoluble Ca phosphates.

The effect of 15 amides and related compounds on the heat stability of milk was investigated; of these urea, biuret, triuret, methyl urea and ethyl urea had a similar stabilizing effect. These 5 compounds reacted with lysine to form a ninhydrin-positive compound, possibly homocitrulline, and with lactose produced Maillard-type browning, but some of the other compounds studied were also capable of participating in one or both of these reactions. The only effect which the 5 stabilizing amides had in common and which the other compounds did not share was a significant pH-buffering capacity in synthetic systems and in milk. It is suggested that urea exercises its stabilizing influence in milk principally through its ability to buffer the pH of the system during heating.

Lamb and kid rennets were prepared by extraction of dried abomasa with 6% (w/v) NaCl-2% (w/v) H3BO3 and activation of the proenzymes at pH 2·0. Each gave one zone of precipitation on casein-agar gel diffusion, enabling them to be differentiated from calf rennet and pig pepsin. After agarose gel electrophoresis, the proteinase activity of lamb rennet occurred in chymosin and pepsin bands only, whereas kid rennet contained an additional proteinase of intermediate mobility. Relative to their milk-clotting activities, lamb and kid rennets contained less pepsin and were less proteolytic on both haemoglobin at pH 1·8 and casein at pH 5·3 than calf rennet. The milk-clotting activities of lamb and kid rennets increased less with decrease in pH and were more stable to storage at both the pH value of maximum stability and lower pH values than that of calf rennet. Neither cathepsin activity nor lipolytic activity on milk fat was detected in any of the 3 rennets, but lamb rennet caused slight hydrolysis of tributyrin.

Measurements have been made of the coagulation times (CT) of concentrated and diluted milks when treated with chymosin. After dilution, milks showed a large increase in CT: conversely, concentrated milks showed a similar CT to unconcentrated milk. The results are discussed in terms of a mechanism which reduces to a form similar to that proposed by Holter (1932).