1. In a short-term winter feeding trial using eight Ayrshire cows, a concentrate with a nominal starch equivalent of 68 was fed at 2 lb. and 4 lb./gal. of milk with either 16 lb. hay or 16 lb. dried grass. Silage (40 lb. per day) was also fed.

2. The weight of dry matter from grass products eaten per day was similar on all four treatments. Differences in total daily dry-matter consumption were very largely attributable to differences in the consumption of concentrate dry matter.

3. The daily dry-matter consumption as a percentage of live weight increased from 2·5 on the rations that included hay and 2 lb. concentrates per gal. to 3·2 on the rations that included dried grass and 4 lb. concentrates per gal.

4. Milk yield was significantly increased from an average of 33·5 to 37·3 lb./day when the amount of concentrates fed increased from 2 to 4 lb./gal. and also significantly increased from 33·9 to 36·9 lb./day when dried grass was fed in place of hay.

5. There was an increase of 0·9 lb. milk for each 1 lb. increase of starch equivalent plus 0·2 lb. digestible crude protein intake as a result of either increasing the rate of concentrate feeding, or of feeding dried grass instead of hay.

6. The fat content of the milk was similar on all four rations, whereas the solids-not-fat varied from 8·42% on the ration that included hay +2 lb. concentrates/gal, to 8·59% on the ration that included dried grass +4 1b. concentrates/gal. This change in S.N.F. was almost entirely in the protein fraction of the milk.

7. There was a gradation in live-weight change from -0·74 lb./day on the hay +2 lb. concentrates/gal, to +0·34 lb./day on the dried grass +4 lb. concentrates/gal.

8. After a consideration of profit margins, milk quality and live-weight changes it was concluded that both treatments B (dried grass +2 lb./gal.) and C (hay +4 lb./gal.) gave optimum and almost identical results.

1. Two levels of steaming-up and two levels of concentrates feeding during the first 84 days of lactation have been compared in a 2 x 2 factorial experiment over three winter seasons, using fifty-two Shorthorn and thirty-six Friesian heifers. The levels of steaming up were 2 cwt. and ½ cwt. of concentrates fed over the last 21 and 14 days of pregnancy, respectively. The levels of concentrates during lactation were 5 and 3 lb. per 10 lb. milk per day. Roughages were fed for maintenance. After the 84th day of lactation all animals were given the same treatment for the remainder of the lactation. Milk yield, milk composition and live weight were measured throughout the lactation.

2. The treatments were annotated as HH, HL, LH and LL, the first letter indicating level of steaming-up and the second the level of concentrates feeding in the first 12 weeks of lactation.

3. Mean milk yields were as follows:

4. The LH treatment reqiuird 3 cwt. more concentrates than HL to produce the same amount of milk.

5. The response to additioal concentrates on the LH treatment after calving was l lb. additional milk per l lb. additional starch equivalent.

6. Butterfat percentages were higher (3·69%) in both groups on low-lactation feeding than in the two groups on high-lactation feeding (3·43%). The HL group (i.e. the group that received high steaming-up and low-lactation feeding) combined high milk yield with a higher butterfat percentage, and at current milk and feedingstuff prices and under the conditions of the trials, this group showed a greater cash return than the groups on the other three treatments.

1. An experiment has been carried out under commercial conditions to compare the value of dried skim-milk and white fish meal as protein supplements in a basal meal fed to fattening pigs in conjunction with unrestricted amounts of whey.

2. There were four treatments. All pigs received 3 lb./pig/day of a basal meal, reduced to 2 lb. by the 13th week of life, plus unrestricted amounts of whey. The protein supplement in the four basal meals comprising the four treatments were: (1) 10% white fish meal, (2) 10% dried skim-milk, (3) 15% dried skim-milk and (4) 20% dried skim-milk.

There were five pens of nine group-fed pigs on each treatment, involving a total of 180 pigs. The pigs were on experiment from approximately 10 weeks of age to bacon weight. Comprehensive carcass measurements were made on all the pigs.

3. The results showed that the white fish meal in the basal meal fed with unrestricted amounts of whey could be replaced by dried skim-milk on a weight for weight basis (10%) without adversely affecting the performance of the pigs. Increasing the percentage of dried skim-milk to 15% appeared to have no advantage, but increasing it to 20% resulted in a slightly better performance of the pigs.

4. The results are discussed in relation to the findings in previous experiments and it was concluded that the evidence obtained so far strongly suggests that as a protein supplement, dried skim-milk is superior to white fish meal for the fattening pig, when compared on a protein content basis.

5. The commercial grading results of the pigs on all four treatments were quite good, with no very marked differences between any of the groups.

6. An average daily peak consumption of about 4¾ gal. whey/pig was reached by all groups of pigs during about the 26th–28th weeks of life. The growth curve and pattern of food consumption of the pigs during the experiment were compared with those in two earlier trials carried out under similar conditions, and possible reasons for some of the differences observed were discussed.

Certain histological factors of the mammary gland and the DNA content unit per dry weight were studied at four stages of lactation in guinea-pigs.

The porosity index, the number of alveoli per field, the number of cells per field and the DNA content, showed maximal values at parturition and minimal values at the peak of lactation, whereas the opposite trend was shown by the value for modal alveolar diameter and the number of cells per modal alveolus.

The relationships between these results are discussed.

That there are variations in the per capita consumption of milk between families has been amply demonstrated—the reports of the National Food Survey, conducted by the Ministry of Agriculture, Fisheries and Food, record them year by year(1). Some, at least, of the reasons for these variations—such as result from differences in income and in the size and composition of families—are also known. There are, in addition, variations in the per capita consumption of milk between different towns and areas of Britain, and it is the purpose of this paper to consider them.

Lactobacilli occur in large numbers in cheese (1), even when the milk used for cheesemaking has been pasteurized (2) and therefore contains very few or no lactobacilli. The lactobacilli in cheese must enter during cheese-making, and a potential source of these organisms is the air of the creamery. Olson & Hammer (3), although not concerned directly with lactobacilli, showed that the numbers of bacteria in the air of dairy plants fluctuated with weather conditions. Naylor & Sharpe(4) found lactobacilli in the air of the Experimental Dairy at the National Institute for Research in Dairying: some strains were identical with others isolated from cheese, but there was frequently no correlation in type of lactobacilli from the air with those from cheese. Thus, ‘cheese types’ were found in the air some months before or after the cheese was made, which seemed to indicate contamination of the air from sources within the dairy. To obtain further information regarding the lactobacillus flora of the air the following investigation was made.

1. Cultural and biochemical details are given of a homofermentative species of lactic acid-producing bacteria, repeatedly isolated from typical maturing New Zealand Cheddar cheese.

2. The Gram-positive cocci, occurring mainly in pairs and tetrads in acid media, are greatly stimulated in growth by the presence of yeast or tomato extracts. The organism converts glucose into inactive lactic acid and smaller amounts of acetic acid.

3. With the exceptions that the organism does not ferment trehalose and is less tolerant to low pH and high concentrations of Teepol, all its characteristics are similar to those for the genus Pediococcus, in particular to the type species P. cerevisiae Balcke.

Organisms identified as Pediococcus strains were found to constitute about a quarter of the normal lactic-acid flora of ripening New Zealand Cheddar cheese. The development and the frequency distribution of these pediococci, in relation to the starter streptococci and lactobacilli were briefly studied.

For a survey of the numbers of lactobacilli present in milk used for cheese-making in creameries, counts were made on an acetate-agar medium (1) selective for lactobacilli. It was observed that the numbers of lactobacilli in the milk in the cheese vat sometimes greatly increased after the addition of the starter to the milk. When these starters were plated on acetate agar growth of lactobacilli, sometimes in large numbers, suggested contamination of the starters with these organisms. The starters in use at sixteen different creameries were then examined on acetate agar, and seven were found to contain lactobacilli. Representative colonies of these organisms were picked from each starter and these strains identified physiologically using the methods of Briggs(2) and Wheater(3,4), and serologically using the group sera of Sharpe(5) and Sharpe & Wheater(6). Table 1 shows the numbers and species of lactobacilli present in the starters. Each starter was sampled several times, usually at monthly intervals.

The lactobacillus flora of two pairs of duplicate cheeses, each pair being made under the same conditions and from the same milk, was examined during ripening. A different distribution of serological types of lactobacilli was found not only within a pair of cheeses but in the top and bottom of the same cheese. A third pair of cheeses, to one of which a known Lactobacillus had been added, was found to have a more regular distribution of lactobacilli owing to greater numbers being present in the cheese milk.

Lactobacilli occur in large numbers in cheese (1,2,3,4) and may be responsible for or influence the formation of flavour. It is therefore desirable to find the source of the lactobacilli and the route by which they enter the cheese, so that the cheese flora may be controlled

1. The influence of a number of factors on the utilization of carotene by rats has been investigated. A high dose level equivalent to that derived from pasture by cows has been employed and liver storage of vitamin A has been used as a measure of the efficiency of carotene utilization.

2. Utilization was influenced by level of carotene intake, by concentration of carotene in the oil used as vehicle, by the degree of unsaturation of the vehicle and by the presence of non-digestible wax.

3. Carotene was better utilized from the rye grass and ‘low cyanide’ white clover than from ‘high cyanide’ clover, but added cyanide had little or no effect on the uptake of carotene from cyanide-free pasture or from a solution in oil.

4. In so far as the results of the investigation can be applied to cows grazing typical New Zealand dairy pasture, it seems that factors which may throw some light on the poor utilization of carotene at certain times of the year are (a) small day-to-day variation in the carotene content of the pasture, (b) variations in the ‘ether extract’ fraction of the pasture, and (c) variations in the degree of hydrogenation of the fat in the rumen.

5. Insulin and adrenalin appear to have no influence on the levels of vitamin A alcohol in the blood plasma of rats.

The results of this investigation form a section of a thesis submitted by one of us (N.A.W.) in partial fulfilment of the requirements for the degree of Ph.D. of the University of New Zealand. The authors are indebted to the Department of Scientific and Industrial Research for a Grant towards this investigation and to Miss Fay Frecklington for technical assistance; one of us (S. Y. T.) is indebted to the Royal Society, the Nuffield Foundation, and the Board of the Dairy Research Institute (N.Z.) for a travelling fellowship during the tenure of which the work reported here was carried out.

1. Microbiological methods were used to measure biotin, nicotinic acid, pantothenic acid, riboflavin, ‘vitamin B6’ and vitamin B12 in milk from Guernsey, Friesian and Shorthorn cows.

2. A study was made of day-to-day variations and breed differences in the B-vitamin content of such milk. Fluctuations in each vitamin were observed from one day to the next in milk from individual cows, these variations being especially marked with biotin and vitamin B12. In addition, the variations in the mean vitamin levels of milk from cows of the same breed were generally greater than any breed difference.

3. Samples of milk from ten Friesian and ten Shorthorn cows were taken at intervals throughout one complete lactation and analysed for each of the vitamins mentioned above. The results of this study of lactational trends are presented in detail.

1. Preliminary experiments show that homogenization, separation and pasteurization all tended to delay the onset of rigidity in renneted milk, though it must be borne in mind that the first two of these treatments were accompanied by some heating of the milk.

2. Once setting had started, homogenized and separated samples set more quickly, and pasteurized (especially over-heated) milk more slowly, than did raw milk.

3. Homogenization would seem to increase, and separation perhaps to decrease the proportion of elastic recovery of the gel which is immediate. The torsiometer, which gives an over-all measure of general consistency, agrees well with the -tube gelometer but when the latter shows an unusual ratio of immediate to slow recovery, the torsiometer follows the former modulus.

4. Increasing quantities of CaCl2 added to reconstituted dried fat-free milk progressively reduce the time needed for rigidity to make its appearance but do not greatly alter the final setting rates. All setting curves approximate to the law that, once rigidity is well established, rate of setting is proportional to the percentage of casein still unset. When the amount of added lactic acid is adjusted so as to prevent the addition of various quantities of CaCl2 from altering the pH appreciably, no great difference is found in the setting curves.

5. The relaxation times, retardation times and their ratio, called ‘the springiness number’, are not greatly affected by the treatments to which the milk samples, either whole or dried, were subjected.

6. Appreciably syneresis usually occurs in the -tube gelometer only when the curd has been strained, though very small strains are sufficient to produce it. The site of its occurrence depends on the hydrodynamic distribution of the larger fat globules. In fat-free or homogenized milk, such syneretic phenomena are either absent or very slight.

1. The sensitivity to calcium of the caseinate-phosphate complex of milk heated at 120°C., increases to an early maximum and thereafter steadily declines, apparently in consequence of parallel changes in the sensitivity of its caseinate constituent.

2. A simultaneously developed capacity of the heated complex to bind additional colloidal phosphate appears to be unrelated to these changes in casein sensitivity.

3. Colloidal phosphate content is confirmed as a factor in the heat coagulation of milk.

4. Heat-developed acidity contributes to the heat coagulation of milk primarily by increasing hydrogen-ion concentration and only slightly, if at all, through release of calcium ions from insoluble combinations.

5. Neither serum proteins nor protein-lactose combinations play any significant part in the heat coagulation of milk.

6. The bearing of these results on the heat coagulation of milk in general and on the operation of certain high-temperature stabilization treatments is discussed.

Average values for the total phosphorus content of sera from unsalted butter samples and for the phosphorus contents of the various fractions of the sera after partition with trichloroacetic acid were: total P, 83·6 mg./100g.; acid-soluble P, 32·4 mg./100 g.; inorganic P, 28·8 mg/100 g.; acid-insoluble P, 51·2 mg./100 g.; and phospholipid p, 33·6 mg./100 g.

There was no evidence that decomposition of the phospholipids or other organic phosphorus compounds occurred in salted or unsalted sweet-cream butters during storage at –10° C. for 8 months.

1. Four batches of soft (Karish) cheese were made from raw and from heat-treated milk containing 1·5% fat and 7% added salt. The cheeses were sealed in tins in contact with their own whey and examined after storage for 1 month and 2 months at room temperature and at 4—6°C.

2. Cheese stored at room temperature lost weight throughout the 2 months, but cheese stored at the low temperature gained weight after 1 month and lost weight after 2 months. Parallel changes occurred in the moisture content and salt content of the cheese.

3. The fat-in-dry-matter content of the cheese increased with room temperature storage, but at 4—6°C. it decreased after 1 month and increased after 2 months.

4. Pasteurization of the milk increased the yield of cheese and the flavour, body and texture were better than that of raw milk cheese stored at the same temperature. The effect of low-temperature storage was, however, greater than that of pasteurization.

5. The total nitrogen content of the cheese decreased throughout storage, particularly at room temperature. The decrease was smaller with pasteurized milk cheese which ripened more slowly. The total nitrogen content of the whey increased throughout storage at room temperature, but at 4—6°C. it increased after one month and decreased slightly after 2 months. The increases were greatest at room temperature and in wheys from raw milk cheese.

6. The initial acidities and also the subsequent rates of increase were higher in wheys from raw milk cheese.

7. The results are discussed in detail.