A possible relationship between the Relative Breeding Value (R.B.V.) and some skin characteristics has been investigated in 89 British Friesian pedigree bulls made available by the Milk Marketing Board of England and Wales.

It was found that there was a statistically significant correlation between the R.B.V. and the follicle diameter. There was also a correlation between the thickness of the papillary layer and the R.B.V. The possible value of the results for selection purposes is discussed.

A study was made of the destructive effects of repeated heat processing of milk on its content of vitamin B6, vitamin B12, thiamine and folic acid. Losses of thiamine and vitamin B6 were cumulative, and increased with frequency and severity of heating.

With folic acid, the first heat treatment potentiated the destructive effect of subsequent treatments; in contrast, the loss of vitamin B12 during in-bottle sterilization was markedly reduced by preliminary HTST pasteurization. These anomalous effects are possibly related to a specific interaction of ascorbic acid with each of these 2 vitamins.

The effects, on the yield and composition of the milk of the cow, of additions to the diet of the calcium salts of acetic, propionic, butyric or lactic acids were determined in 3 change-over experiments. In all cases yield of milk was increased slightly and milk fat content was reduced; solids-not-fat (SNF) percentage was depressed by acetate and butyrate. The effects of these treatments differed markedly from those observed previously when dilute solutions of the corresponding acids were infused into the rumen, but the relative effects of the calcium salts were similar to those of the free acids. It was concluded that the specific effects of the acids were overshadowed by a more marked general effect arising from their addition to the diet as calcium salts. This was confirmed in a subsequent experiment with fistulated cows, in which the effect of an infusion of propionic acid into the rumen was compared with that of an infusion of calcium propionate and of calcium propionate given with the diet. The effect of the addition to the diet of calcium in the form of carbonate differed from that of calcium salts of the fatty acids. It was concluded that the salts were not likely to find practical use.

An analysis of variance was applied to the ‘within herd’ variance of milk total solids in order to find the contribution due to sampling, testing and biological variances on a balanced 8 × 8 two factor (herds and days) experiment with replicate sampling and testing. Testing samples from every consignment from 10 herds over a 12-month period showed that the mean monthy ‘within herd’ variance was 0·039 and the yearly ‘within herd’ variance was 0·085. A formula is given showing how the variance of the mean for compositional quality testing can be obtained and on which the design of testing schemes can be based.

1082 drip samples of fresh milk were taken at a creamery over a period of 3 years and tested for total solids by the current gravimetric method (British Standards Institution, 1963) and the hydrometric method with the fat in the liquid state (British Standards Institution, 1959). On average, the hydrometric method overestimated the total solids by 0·096. It is suggested that the formula which applied before 1 October 1957 is correct and should replace the present formula.

A milking parlour and milking equipment are described which have been found suitable for experimental work on the nutrition and the physiology of lactating ewes.

Clean spores suspensions of 3 strains of Clostridium tyrobutyricum were prepared after culture in dialysis sacs. The survivor curves of the spores heated at 90 °C in 0·033 M phosphate buffer (pH 7·0) or in skim-milk were logarithmic. From the thermal-death-time curves the following values were calculated: D at 121 °C = 0·003−0·012 min and z = 8·4−10 °C when spores were heated in phosphate buffer; D at 121 °C = 0·006−0·008 and z = 9·5−9·9 °C when spores were heated in milk.

When clean spores of 2 strains of Clostridium butyricum were heated at 85 °C in 0·005 M phosphate buffer (pH 7·0) the survivor curves were logarithmic, but ‘tails’ were observed after heating in skim-milk. The value of D at 85 °C was lower than that obtained with spores of C. tyrobutyricum.

Phospholipid was isolated from milk, butter, and washed-cream serum by solvent extraction followed by simple counter-current distribution and thin-layer chromatography. Iodine values from fresh samples, determined by a micro-Wijs technique, ranged, for the cephalin fraction, from 70 to 86, for the lecithin fraction from 44 to 55, and for the sphingomyelin fraction from 36 to 44. In washed-cream serum, oxidation with copper and ascorbic acid led to reduction in extractable phosphorus, decreased chromatographic mobility of phospholipid and significant falls in the iodine values of the 3 phospholipid fractions. In milk, slight reductions in phospholipid iodine values were observed following copper-catalysed oxidation but they were not consistently significant. Iodine values of butter phospholipids remained unchanged even after gross oxidative quality deterioration.

Heat sterilization of milk destroyed about 50% of its folic acid activity, and subsequent exposure of the milk to sunlight caused a progressive further loss. This loss of folate, as of vitamin B12, was a consequence of the oxidative destruction of the milk's ascorbic acid, and was largely prevented by thorough exclusion of oxygen from the milk during heat processing and subsequent storage. With thiamine, riboflavin, nicotinic acid, vitamin B6 and biotin, stability towards heating and during exposure to sunlight was affected little, if at all, by the oxygen tension in the milk.

The sensitivities of isolates of bovine staphylococci, corynebacteria and streptococci to various antibiotics were determined. The growth of various strains of Staphylococcus aureus was inhibited by the following range of concentrations of antibiotic: cloxacillin, 0·07 to 0·6 μg/ml; penicillin G, 0·018 to > 250 μg/ml; streptomycin, 1·25 to > 250 µg/ml; novobiocin, 0·15 to 25 μg/ml; chlortetracycline, 0·6 to 10 µg/ml. The concentrations of cloxacillin required to inhibit growth were between 0·15 and 1·25 μg/ml for strains of Streptococcus agalactiae; 0·07 to 0·3 μg/ml for strains of Streptococcus dysgalactiae and 0·15 to 0·6 μg/ml for strains of Streptococcus uberis.

The corynebacteria were generally sensitive to the penicillins (ampicillin, penicillin G, phenethicillin and cloxacillin), but showed least sensitivity to cloxacillin which had a similar activity to that of chlortetracycline, neomycin and oleandomycin. Chloramphenicol and streptomycin were less active than the penicillins and novobiocin showed little activity against Corynebacterium ulcerans.

A clear relationship was confirmed between the sensitivity of staphylococci to cloxacillin and penicillin G. Some indication was found of an association between the sensitivity of staphylococci to cloxacillin and the success of cloxacillin intramammary therapy in the non-lactating udder. There was no evidence of a change in the sensitivity of Staph. aureus following exposure to cloxacillin in the non-lactating udder.

Comparisons were made of the flavour, free fatty acids and bacterial flora of commercial cheese made at different factories and experimental cheese made under aseptic conditions: (i) with δ-gluconic acid lactone instead of starter, (ii) with starter only, (iii) with starter and added floras derived from the curd of the commercial cheeses (reference flora cheeses).

Comparison of the bacterial flora of commercial and reference flora cheeses showed that replication of organisms was better with some reference floras than with others. In all the cheeses the lactobacilli increased in numbers during maturation, whilst other groups of organisms died out.

The amount of acetic acid present was influenced by the starter and by the lactobacilli. Single-strain starters produced some acetic acid, most of which was lost in the whey; commercial starters produced considerably more, due to the presence in them of Streptococcus diacetilactis. Later in maturation lactobacilli increased the acetic acid content, a greater increase being observed with homo-than with heterofermentative strains.

The initial levels of butyric and higher fatty acids in the milk varied with source of the milk and with the season, summer milk having higher levels than winter milk. During cheese-making a slight increase of these acids occurred in every cheese made with starter and a further small increase occurred during ripening. However, there was no increase in the content of these acids in the cheese made with δ-gluconic acid lactone, indicating that lactic acid bacteria were weakly hydrolysing the milk fat.

Flavour trials showed that Cheddar flavour was present not only in the reference flora and commercial cheese, but also in the cheese made with starter only. Different starters produced different intensities of flavour; one strain produced an intense fruity off-flavour. Cheeses made with δ-gluconic acid lactone were devoid of cheese flavour.