When the teats of dry cows were dipped in a culture containing 3–25 × 106 mastitis organisms/ml only 25% of 71 quarters acquired an intramammary infection. Small numbers of organisms applied to teats caused negligible infection. The degree of contamination also determined the survival of the organisms on the exterior of teats, which was much greater at the teat apex than on the body of the teat.

There was no evidence that swabbing the teat apex increased the chance of intramammary infection. Washing the udder of infected cows with a disinfectant increased the chance of recovering the organisms from the teat skin.

Classical methods and methods based on the use of disodium ethylene-diaminetetra-acetate (EDTA) for the semi-micro determination of calcium and magnesium in milk and milk diffusate are described. With both types of method satisfactory accuracy and precision are attainable. The use of the EDTA methods leads to greater speed and convenience but practice in recognizing the correct titration end-points is necessary.

A within-cow comparison was made of methods of control of udder infection in dry cows whose teats were deliberately contaminated with cultures of mastitis organisms. Very nearly complete protection against infection with staphylococci and streptococci was obtained by infusion of antibiotics through the teat canal. Disinfection alone, i.e. dipping the teats in 2% chlorhexidine, gave good protection against staphylococci but no protection against Streptococcus uberis.

Four hays were compared in a 20-week winter feeding trial using eight Ayrshire cows. The hays consisted of either ryegrass (variety S 24) or cocksfoot (S 37), and each grass was cut either on 23–25 May (cut 1) or 3 weeks later on 13–15 June (cut 2). The ryegrass cut 1 hay (R1) had the highest content of digestible dry matter, the cocksfoot cut 2 hay (C2) had the lowest content. The ryegrass cut 2 hay (R2) and cocksfoot cut 1 hay (Cl) had intermediate values. On all the treatments the cows were offered 19 lb of hay daily plus concentrates at the rate of 3½ lb/10 lb of milk.

The consumption of concentrate dry matter was almost identical on the four treatments and averaged 10·1 lb per cow per day but the intake of C2 was slightly, but significantly, below that of the other three hays. On average the hays contributed 62% of the total daily intake of dry matter. The total weight of starch equivalent (S.E.) eaten per day increased from 13·6 lb on the C2 treatment to 15·2 lb on the R1 treatment.

The mean daily milk yields on the four hay treatments were: Rl, 32·1 lb; R2, 29·9 lb; C1, 30·5 lb and C2, 26·9 lb. On average the milk yields from cut 1 hays were significantly higher than the yields from cut 2 hays, and the yields from the ryegrass were significantly higher than the corresponding yields from the cocksfoot. The differences in milk composition between treatments were small. The fat percentage of the milk on C2 was higher than that with the other three hays, and with the higher yielding cows the solids-not-fat (S.N.F.) and crude protein percentages were significantly higher on R1 than on the other hays.

It is concluded that the nutritional value of ryegrass hay is superior to that of cocksfoot hay for milk production.

In earlier papers it was shown that the fall in viscosity of milk and caseinate solutions acted on by rennet, follows a first-order reaction equation. The reaction rate constant has been found to be independent of the source of the caseinate substrate used. This seems to be true not only for caseinate from normal cow's milk but also from colostrum, slow-clotting cow's milk and even the milk of buffaloes, sheep and probably goats.

With solutions of caseinate from sow's milk the reaction kinetics and the proportional viscosity loss were similar to those of cow's caseinate but the rate constants were much lower. Rennet showed no measurable reaction with human, whale, mare or rhinoceros caseinates but produced a constant rate of fall in the viscosity of a camel caseinate for more than an hour from rennetting.

Vegetable and microbiological rennet substitutes also produce a fall in the viscosity of sodium caseinate and the reactions follow first-order kinetics. They differ from cheese rennet in that the proteolysis involved is stronger and is not as limited as that of rennin since they attack at least twice as much of the casein ensemble. This might suggest a mixture of enzymes but since the proportionality between enzyme concentration and k1 was very close this seems unlikely.

Milk and butterfat yields, and the properties of butterfats from the milks, were compared in three successive years for early- and late-calving cows of monozygotic twin pairs grazed on the same pastures, over the period when both cows of the twin pairs were in lactation.

The seasonal fluctuations in the properties of the butterfat were closely similar for the two groups of cows in all three trials. This was taken to indicate that the known regular pattern of seasonal change in the properties of New Zealand butterfat over all North Island districts is not due to change in stage of lactation of the cows but is probably the result of a regular change in the feeding conditions.

The average milk and butterfat yields were lower for the early-calving cows during the comparison period, the iodine values were higher, and the Reichert and saponification values were lower. The early-calving cows were uniformly heavier than the late-calving cows. It is suggested that the consistent differences in the butterfat characteristics over the whole comparison period could be due to differences in the extent to which body fat reserves were drawn upon by the cows for maintenance of lactation.

The average carotene and vitamin A contents of the butterfats were not appreciably different for the two groups of cows, indicating that these values are not directly related to stage of lactation of the cows or to yield of milk or butterfat.

From an analysis of the milking rate data of 200 cows it has been shown that for individual cows the yields of milk obtained in the second minute of milking give a good prediction of their maximum milking rates.

A rapid method for the estimation of carbon dioxide in Cheddar cheese is described which gives good reproducibility and is free from major sources of error.

For the past 10 years, a herd of reindeer (Rangifer tarandus) has been kept in the Scottish Highlands under the auspices of the Reindeer Council of the United Kingdom. It was established in 1952 when the Reindeer Co. Ltd. imported two small consignments of reindeer from Arctic Sweden. By 1962 the herd numbered about thirty, of which twenty-one have been bred in Scotland.