1. Thirty-eight first-calf heifers in two equal groups were subjected for complete lactations to a rigid control of the duration of milking to either 4 or 8 min.

2. The treatment had no major effect on the milking rates of either group.

3. Whilst 4 min. was insufficient time to milk out completely the udders of about half the animals on this treatment, the machines on the 8 min. treatment were generally left on for a period after milk flow had stopped.

4. There was no significant difference between the 305-day lactation yields of the two groups or in the persistency. The 4 min. treatment did, however, decrease the yield of milk and fat in early lactation.

5. The 8 min. cows had more clinical and subclinical mastitis, though they did not have a higher proportion of eroded teats nor higher Whiteside test readings.

6. Teat erosion appeared to be correlated with slow milking.

1. The behaviour of dairy cattle under normal commercial conditions of management was studied in two series of observations:

(a) Four cows were observed continuously for 24 hr. on four occasions at approximately two-weekly intervals.

(b) A herd (average fifty-two cows) was observed continuously for 24 hr. on twelve occasions at approximately monthly intervals.

2. Under our conditions and within our definitions, the cows grazed 6–52 hr., lay down 9–22 hr. and loafed 8–26 hr. on an average during 24 hr.

3. The cows ruminated 5–60 hr. per 24 hr.; 4–52 hr. when lying down and 1–08 hr. when loafing.

4. On average the animals defaecated 1T6 times, urinated 9–8 times, and drank 3–8 times in 24 hr.

5. One animal walked an average distance of 1–74 miles per 24 hr., excluding journeys to the cowshed.

6. No aspect of grazing behaviour was found to be strongly related to either current milk yields or air temperature.

7. When on ‘good’ pasture, as compared to ‘poor’, the animals grazed for a shorter time, walked less, and took fewer drinks.

8. From the results of the herd observations a similar periodicity of behaviour during 24 hr. was observed throughout the year but was more apparent when environmental conditions were similar.

9. When the herd was confined to 5 ft. concrete standings during the winter nights, the animals did not rest as comfortably as when out of doors.

10. Major peaks of grazing or eating were recorded after each milking followed by periods of lying down, especially during the night.

11. Time of sunset has been related to the time when grazing ceased and the herd lay down.

12. In view of the data collected, tentative suggestions for improving grazing management are made.

The volume and seasonality of veal production in west Wales has been obtained from an analysis of the records of the collecting centres of the Ministry of Food.

It has been found that about 1000 tons of veal are produced annually from 55% of the calves sold to the Ministry at an average carcass weight of 56 lb. Most of the veal is produced in the season of the maximum number of calvings, i.e. spring in the eastern areas and autumn in the western areas. Higher average carcass weights are produced in summer and a higher proportion of the calves offered, are veals during the summer than during the winter. March might be taken as the month of maximum veal output but of lowest average individual carcass weights. The relation between veal weights, production and the average price of milk has been illustrated, and the conclusion drawn is that when milk is cheap (summer) veal weights are high. The more intensive the dairying (in the central part of the region) the lower the average carcass weight and vice versa for the less intensively dairying areas. Calves sold for rearing are only of minor significance in the calf trade in west Wales, but one consolation is that the incidence of the casualty calf is also slight. The choice of colour in calves purchased for further rearing supports the general opinion that during the period under review (1943–6) the Shorthorn breed was the most important, and its Hereford crosses the most popular choice in the more remote beefproducing areas of Pembrokeshire.

1. A study has been made of the interrelationships between persistency and maximum yield as components of the lactation curve, and of the importance of environment and heredity in determining the shape of the lactation curve of Ayrshire cows.

2. Persistency was defined as the linear constant of the exponential curve expressed as a percentage, maximum yield as the highest 30-day yield as calculated from the records, and total yield as the yield of milk from 15 days to 8½ months after calving.

3. The study was based on milk records computed by the official method of the Scottish Milk Records Association. The data used in much of the work was obtained from five herds of Ayrshire cows and involved 2392 lactations during the period 1920–39.

4. In an exploratory test involving 100 lactations it was found that the exponential curve fitted ninety-five of the lactation curves and that the fit was improved in forty-eight of these ninety-five curves by using the parabolic exponential curve. Five of the lactations were too erratic to be fitted by any simple mathematical curve.

1. A study was made of the milking of the two hind quarters of four cows by teat cup and by teat cannula at three levels of vacuum and by teat cannula at atmospheric pressure.

2. The eight quarters milked at significantly different maximum rates by teat cup but at nearly the same rate through a teat cannula, suggesting that the teat orifice is a very important factor controlling rate of milking.

3. The maximum rate of milking by both teat cup and teat cannula increased with increasing level of vacuum from 11 to 20 in. Hg. The rate of increase in the teat-cup milking was greater than in the cannula milking, suggesting that the teat orifice was stretched open at the higher levels of vacuum.

4. The average amount of strippings increased at the higher level of vacuum in teat-cup milking, due apparently to teat-cup crawl.

1. A study has been made of the distribution of the so-called sweat glands in the ears of Ayrshire cattle.

2. The number of sweat glands per unit area of skin in the ear was found to vary greatly from one part of the ear to another and did not appear to be related to the milk yield. It is concluded that it is impossible to use the sweat-gland count in the ear as an indication of the milk-producing capacity of Ayrshire cattle.

3. The number of sweat glands per unit area in the ear of the very young calf was found to be greater than in the fully grown cow, the number being roughly inversely proportional to the surface area of the ear.

4. These findings for Ayrshire cattle are contrary to those published by a number of other workers for cattle of the Red German breed, who claim that any portion of the ear can be used to obtain a sweat-gland count which is closely correlated with milk yield.

A study has been made of the effect of udder infections on the proportionate yield and composition of the milk of individual quarters of over 100 cows, and the data from eleven of these cows have been presented.

Typical examples have been given showing that subclinical Streptococcus and haemolytic Staphylococcus infections may persist for months and either cause a gradual reduction in the proportionate yield, and solids-not-fat percentage of a quarter or have no measurable effect, and that both types of reaction may occur simultaneously in the same udder.

Examples also show that following penicillin treatment of clinical cases caused by streptococci and staphylococci there is little recovery in the proportionate yield of the treated quarter until the following lactation, when recovery may be complete.

In a herd averaging forty-five to fifty cows in milk, large numbers of infections occurred during the dry period and over half of these developed during the first 3 weeks after the final milking-out of the udder. About 50% of the infections persisted and a like percentage of these produced clinical symptoms within the first 2 weeks of calving, half of them caused by staphylococci.

Since the publication of the original paper (1) on the occurrence of slow-reducing coliform organisms in raw milk, further investigational work has been undertaken. During the course of the work two different types of coliform organisms appeared to be responsible for the slow reduction of methylene blue: (a) those having a long lag phase of growth, and (b) those destroyed by a bactericidal substance present in raw milk.

1. Examinations have been made of milk pasteurized by the L.T. ‘Holder’ and H.T.S.T. processes using the same original bulk raw milk. In the preparation of samples care was taken to eliminate the possibility of post-pasteurization contamination. It was hoped that any differences found would be due solely to the effects of the pasteurizing processes above.

2. Samples were examined by (a) colony counts and coliform tests when fresh and after ageing at 18°C. for 24 and 48 hr., (b) methylene-blue and resazurin reduction tests when fresh and after ageing at 18°C. for 45½hr., (c) keeping quality at 18°C. to end-point of 68% alcohol and clot-on-boiling tests. All bacteriological and dye reduction tests were carried out at incubation temperatures of 37, 30 and 22°C.

3. In seven trials the experiments were repeated after storage of the original raw milk for 24 hr. at 40–50°F. (4·4–10·0°C.).

4. Some detailed examinations were made of the bacterial floras of the raw and corresponding pasteurized milks, both when fresh and after ageing.

Two pieces of apparatus are described for use in studies on disinfection of milking machine teat cups: (1) an easily constructed attachment for a standard milking machine allowing the collection of the total yield from each individual quarter; and (2) an apparatus designed to reproduce as closely as possible machine milking and to allow an equal quantity of the same sample of infected milk to be ‘milked’ through each of four teat cups which will be infected to the same extent. These infected teat cups can be used to provide comparable results in trials on different disinfection procedures.

The experiments analysed in this series of papers were undertaken as the result of a discussion on methods of measuring the keeping quality of milk, at a Conference of Advisory Bacteriologists of the Ministry of Agriculture and Fisheries.

Owing to the disturbance and difficulty following the outbreak of war and the dislocation of handling and distribution, a serious decline in the keeping quality of raw-milk supplies was threatened.

1. The acid phosphatase content of milk is reasonably constant from quarter to quarter in normal uninfected cows.

2. The acid phosphatase content of milk from infected quarters is enhanced in comparison with the uninfected quarters. The differences found were from 4·1 to over 50 enzyme units per 100 ml. milk.

3. It has been shown that a Streptococcus agalactiae suspension is capable of hydrolysing phenylphosphate at pH 4–1, and it is suggested that this organism is largely responsible for the enhanced enzyme content of the milk from the infected udder.

The roll-tube method for estimating bacterial counts was devised by Esmarch(1), but was soon afterwards superseded by the introduction of Petri plates which have several advantages for cultural and counting purposes. The roll-tube method, however, has been revived by several workers (2,3,4), and where a simple, rapid and economical method is required it is very useful, especially if low counts are being dealt with. For this reason it is particularly suitable for yeast and mould counts in butter and has been so used in this laboratory for many years. In addition to its regular use for this purpose, several series of comparisons have shown that the roll-tube method is capable of giving results which compare very well with Petri plate counts upon milk, using the usual dilution technique in both cases.

1. The determination of ascorbic acid in butter by the usual macrotitration method was found to be impossible because this substance rapidly became oxidized while the butter was being melted, so that only about half could be recovered.

2. A simple micro-titration procedure enabled more reliable results to be obtained, but the loss of ascorbic acid from smaller samples could not be reduced below about 10% under the most favourable conditions.

3. Kinetic experiments have been carried out on butter serum and buttermilk to which ascorbic acid had been added, and from the results it has been deduced that the oxidation of ascorbic acid takes place by three distinct concomitant reactions: one catalysed by the original copper, one catalysed by added copper, and one catalysed by added ferric iron.

4. It has been calculated that in an unsalted butter of normal metallic content half the ascorbic acid would be oxidized in about 12 hr. at cold storage temperature ( – 13° C). At this temperature, 0·1 p.p.m. of added copper is about twenty times as effective a catalyst as 1·0 p.p.m. of added iron. At room temperature the corresponding half-oxidation time would be about 2 hr., and here 0·1 p.p.m. of added copper is about four times as active as 1·0 p.p.m. of added iron. In salted butter the inhibitory effect of the chloride ion would increase these times somewhat.

5. The chemical state in which copper and iron exist in milk and related products has been discussed, especially in relation to the kinetic results obtained.

1. Mammary tissue of the cow and the rat contains acid phosphatase. The respective pH optima are 5·5–5·8 and 6·0.

2. The enzyme in cow mammary tissue is probably one of type AII in the Folley & Kay (10) classification.

3. The acid phosphatase of cow mammary tissue is inhibited by a factor in raw cows' milk. This factor is destroyed by heat.

4. On the basis of rate of hydrolysis of phenylphosphate at the optimum pH there is about 5 times more alkaline phosphatase in the mammary tissue of the cow than acid phosphatase.

5. The effect of adrenalectomy and replacement therapy through the administration of cortical steroids has no marked effect on the acid phosphatase of rat mammary tissue.

1. A method has been developed for measuring the intensity of colour produced in the Aschaffenburg & Mullen phosphatase test in which use is made of permanent colour standards.

2. Using this method, the relationship between this phosphatase technique and the official Kay-Graham test has been investigated.

3. The limiting standards corresponding to 2.3 Lovibond Blue Units in the KayGraham test have been established for the 30 min. and 2 hr. procedures of Aschaffenburg & Mullen.

4. The advantages of the improved technique of the Aschaffenburg & Mullen test are discussed.

1. Using Hammer's litmus milk enrichment technique, a total of ninety-one cultures of Ps. putrefaciens were isolated from 1563 samples of normal salted butter graded for export.

2. A correlation was demonstrated between poor hygienic conditions in butter factories and the incidence of Ps. putrefaciens contamination of the butter.

1. The limitations have been explored of a simplified form of Grimes's litmus milk method, as used for a presumptive test for coliform organisms in butter.

2. To improve on this test, the merits and demerits of renneted litmus milk and litmus milk agar have been investigated, and the latter found preferable.

3. Of 719 samples of export salted butter tested for coliform contamination, only 19·1% gave confirmed positive results using MacConkey broth as the presumptive medium, 21·9% were positive using a litmus milk agar medium, and 30·2% (on 434 samples only) were positive using renneted milk.

4. The coliform organisms isolated were classified into the usual types and a seasonal variation in the coli to aerogenes ratio noted.

5. An observation is made on what appears to be the inhibitory effect of bile salt on the gas production of several strains of the aerogenes-cloacae group isolated in this investigation.

1. A new type of oxalate titration permitting determination of the nature of the colloidal phosphate of milk has been developed.

2. About 88% of the colloidal phosphate appears to be tricalcic, the remainder is thought to be dicalcic.

3. Estimates of tricalcium phosphate by the Ling titration are distinctly higher than the foregoing. This would seem to be due mainly to the divergent pH values to which milk and whey are titrated in this method. There is no evidence of any conversion of colloidal dicalcium to tricalcium phosphate during the Ling titration, as had been suggested.