1. An analysis has been made of production records and body measurements of dairy cattle from farms and special progeny testing stations in Denmark.

2. Heritability estimates of various measurements of body size and also of gross efficiency of food conversion were all in the neighbourhood of 0·50. Body weight was more closely correlated with girth than with height.

3. Milk yield had a very high correlation, both phenotypic and genetic, with gross efficiency. This was shown on theoretical grounds to be a necessary result of any standard system of feeding.

4. Correlations between production characteristics and body measurements were slight. There was some suggestion that selection for yield would increase skeletal size but decrease fleshing.

5. The best index on which to select for efficiency of food conversion under these conditions would be the yield divided by the height.

1. Data from 133 Dairy Shorthorn cows in three herds have been used in a study of various methods of estimating live weight from body measurements based on logarithmic relationships and indices of body volume.

2. Regression equations are presented relating live weight to several combinations of chest girth, paunch girth, length of body and age.

3. The most satisfactory estimate of weight from a single body measurement was given by the regression of log live weight upon log chest girth.

4. Appreciable increases in the efficiency of estimation were obtained by including log paunch girth or log length of body as second variates in the regression, and a further increase by including them together.

5. Indices of body volume using chest girth and length of body, or chest girth, paunch girth and length of body gave good estimates of live weight, and there was very little difference in efficiency of estimation from that when the three measurements were used in a logarithmic regression.

6. The effects of the addition of age to regressions involving chest girth, paunch girth and length of body were slight but statistically significant.

7. The most satisfactory practical method of estimation using the three body measurements is given by the equation

Live weight (lb.)=0·000935 LB(CG2+PG2+ PG.CG)+57 (all measurements in inches).

8. Comparison of fiducial limits showed that these covered a range 4–5 times as great for live weights estimated from chest girth than for live weights determined directly, and that the inclusion of length of body and paunch girth reduced this range by 25–30%.

Lactation has two phases: the continuous process of secretion and the mechanism of ejection which occurs only during milking. Because ejection is a transitory phase it is to be expected that within certain limits milk yield will be inversely related to the duration of milking, which was, in fact, demonstrated many years ago with hand-milked cows(1). With machine milking the situation is different because the forces which the machine applies to the udders of all cows within a herd are the same, and thus the differences in milking rate that occur are due to differences between the cows. Under these conditions, if milking rate can be shown to affect milk yield it is a demonstration of how the physiological factors controlling milking rate can modify the expression of the inheritance of milk secretion.

1. The effects of thyrotropin on milk yields and heart rates of goats were compared with the effects of growth hormone.

2. As expected, the milk yields from the goats which received growth hormone were markedly increased.

3. Thyrotropin caused increases of heart rate in two goats in one of which a large increase of milk yield was also produced.

A report from the United States Department of Agriculture in 1947(1) claimed that a measurement of the mammary gland development of the calf could give some indication of the animal's future milk production. Although the first report did not contain full experimental results, the few figures that were published, and the very strong recommendation from the authors that the relationship should be tested further, encouraged the launchin g of a field trial at Reading University in 1950.

The effect of oxytocin on the intramammary pressure of the lactating ewe has been described. The pressure curve produced by the ewe is shown to be different from both sow and cow.

An improved pressure recorder is described.

There can now be little doubt that glucose is the principal precursor of lactose in the mammary gland. Evidence for this comes form in vivo and in vitro studies, using both analytical and isotopic techniques (1), though considerable species differences have been noted.

1. Criticism is directed towards the method of assessing cheese-starter activities, whereby pasteurized milk (vat milk) is inoculated with starter and its activity judged by the acidity developed after 6 hr. at 30° C.

2. It has been found that certain starters are slow when subjected to this laboratory test, owing to the fact that they are agglutinated in such milk and consequently carried up into the cream layer, thus producing a lower acidity in the milk.

3. Whilst such starters show higher activity in homogenized or autoclaved milk, it is suggested that starter activity tests should be carried out in the presence of agar in order to prevent cream rising and thus simulate conditions in the cheese vat. Agar is preferred to rennet for this purpose.

4. It is emphasized that such apparently slow starters are not slow when used in the cheese vat.

5. Evidence is given that keeping-quality tests on pasteurized and homogenized milks involving storage of the milk are also affected by the same factors, which may result in homogenized milk having a poorer keeping quality than pasteurized milk.

1. The vapour/liquid equilibrium coefficient for diacetyl in 35–40% cream has been found to be of the order of 26–28, compared with 39·3 for water. In a 5% aqueous solution of lactose, equivalent to that present in milk and in cream serum, the coefficient was 30. The depression of the equilibrium coefficient by lactose in solution was shown to be independent of the concentration of diacetyl present in the liquid at time of partition, over the range 1–65 p.p.m.

2. The slower rate of removal of diacetyl from cream, per unit weight of steam condensed as compared with its removal from water, was observed to be due mainly to this depressing effect of lactose on the equilibrium coefficient; but there was some evidence that delay in re-establishment of the solubility partition equilibrium as between butterfat and cream serum also contributed to the lowering of the equilibrium coefficient for diacetyl in cream as measured in the laboratory continuous vaporization equilibrium still.

3. Sodium chloride in the solution caused a rise in the equilibrium coefficient for diacetyl from the value of 39·3 for water to about 69 for a 10% salt solution and 82 for a 20% salt solution.

4. Lactose had no effect on the equilibrium coefficient for acetoin, but salt caused a rise from 1·29 for water to approximately 1·75 for a 10% salt solution.

5. The possible effect of lactose on the effectiveness of steam in cream deodorization equipment is referred to.

1. Pasteurized, sterilized, U.H.T. treated, U.H.T. treated-sterilized, evaporated, sweetened condensed, roller- and spray-dried milks were prepared simultaneously from one bulk of raw whole milk.

2. The preparation of any of these products entailed little or no apparent loss of riboflavin, pantothenic acid, nicotinic acid, vitamin B6 or biotin.

3. Thiamine was destroyed in amounts ranging from less than 10% to 40–50%, increasing with the severity of the heat treatment.

4. Prolonged high temperature used in the sterilization of evaporated milk and of in-bottle sterilized milk caused nearly complete loss of vitamin B12.

5. The new process of sterilization by the U.H.T. treatment alone when it was not followed by the, so far necessary, in-bottle sterilization caused little more loss of the vitamins measured than did H.T.S.T. pasteurization.

Milk samples were collected, between 17 April and 30 May 1956, from fifty-six Ayrshire and forty Friesian cows, which had been calved for between 45 and 165 days, when they were running out at grass day and night. The results showed that differences in the fat percentages of their milk were accompanied by corresponding variations in the average diameter of the globules in both breeds and in the numbers of globules per cu.mm. in the Friesian cows. These changes were not significant for either variant because there were some individuals in which changes in fat percentage appeared to be accounted for by either an increase in fat globule diameter or an increase in the number per cu.mm. with correspondingly low figures for the other variant.

1. During the period September 1954—August 1956 monthly samples of milk were obtained from individual cows in herds selected because of known history of low solids-not-fat. Records were kept of general feeding and management. Milk was analysed for total solids, butter fat and s.n.f. (by difference). Crude protein and lactose were also estimated at three-monthly intervals.

2. Mean lactation averages were calculated for s.n.f. These showed a normal distribution around a mean of approximately 8·5%.

3. Throughout the period a high proportion of samples failed to reach 8·5%. The seasonal effect is at its worst in March and April when 70% of the samples were below 8·5%.

4. Effect of advancing lactation (uncorrected for the effect of season) agreed broadly with previously published work but marked differences in the shape of the lactation curve were found between different herds. Variations in s.n.f. are largely a reflexion of variations in crude protein.

5. Age distribution of the cows agreed favourably with published figures for the national herd, and a mean regression of s.n.f. with age gave 0·11% per year.

6. Supervision of the feeding of the herds in the investigation gave no measurable improvement in s.n.f. and no significant response was obtained from short-term trials where extra s.e. was fed.

7. There was no undue incidence of disease of the udder, either clinical or subclinical.

8. Little information could be obtained on breeding, but it is concluded that the major cause of the problem is the genetically poor potentialities of the cows as judged from the average composition of the milk they produce.

1. The trends of starter bacteria population during the manufacture and maturing of Cheddar cheese have been investigated. Fourteen strains consisting of Str. lactis, Str. diacetilactis and Str. cremoris have been studied.

2. Physiological and morphological characteristics of the fourteen strains were examined.

3. Population studies during manufacture showed that the three species of starter organism attain quite different maximum populations and at different stages of the cheesemaking process. Str. lactis (4500 millions/g.) and Str. diacetilactis (2900 millions/g.) reached their maximum half way through Cheddaring, whereas Str. cremoris (960 millions/g.) reached its maximum at milling.

4. Str. lactis was shown to maintain its maximum population until the cheese left the press, whereas Str. diacetilactis and Str. cremoris steadily declined after reaching their maximum.

5. Counts of the different starter cultures used showed considerable variation between and within strains, particularly in the case of Str. cremoris.

6. No relationship was shown to exist between acidity development and starter populations developed.

7. The study of cell distribution in the cheese curd has shown that whereas Str. lactis and Str. diacetilactis gave an even scattering of diplococci, Str. cremoris showed colony formation.

8. Str. lactis strains maintained a high but declining population during maturing of the cheese, the starter beginning to die out gradually after 8 weeks. Str. diacetilactis showed similar trends but at lower populations levels. Str. cremoris, on the other hand, gave much lower populations, the starter dying out rapidly after 2 weeks, and virtually disappearing at 8 weeks.

9. Persistence of starter bacteria in the cheese appears to be correlated with salt tolerance and chain length.

10. Starter bacteria isolated from the cheese made with Str. lactis have shown a low proportion of slow acid-producing types in contrast to a high proportion found with Str. cremoris.

11. The non-starter bacteria in the cheese were found to consist on the average of 30% micrococci and 70% lactobacilli. Negligible numbers of other genera were isolated.

1. A study has been made of the development of titratable acidity, lactic acid and volatile fatty acids in five locally made type cheeses. The study of the changes involved has been made over the period of ripening up to the stage at which each type would normally be marketed. All the cheeses were made from the same batch of milk at the same time.

2. Slight modifications to the micro-column devised by James & Martin (13), and its use, have been suggested which have resulted in improved recovery of volatile fatty acids.

3. The volatile fatty acids have been determined in toto and also as separate constituents. Formic acid has been noticed as a common constituent of the acid mixture in all the cheeses, while, over the ripening period involved and apart from unidentified acids higher than caproic, the only other volatile acids encountered have been acetic and butyric, and on one occasion iso-butyric.

4. Over the short ripening period studied, the lactic acid content of the soft cheeses rose, but after the initial rise in Pont l'Évêque and in Dutch cheese the results showed a downward trend. Fluctuations in the lactic acid content of the Smallholder cheese have been noted which compare with the corresponding findings of other workers.

5. All the results presented have been calculated on the basis of fresh cheese because this is the customary practice and comparisons with other work would be difficult if this had not been adhered to.

Some of the factors influencing the concentration of carbon dioxide found in New Zealand Cheddar cheese have been investigated.

1. Cheeses made with the use of commercial starters (containing betacocci) are characterized by a rapid increase in their carbon dioxide content during the 2 weeks following manufacture.

2. Cheeses made with the use of single strain starters do not change in carbon dioxide content in the first 2 weeks following manufacture, but may ultimately contain as much carbon dioxide as commercial starter cheeses.

3. High concentrations of carbon dioxide within a cheese result in an open texture, especially when the carbon dioxide is formed shortly after manufacture.

4. The loss of carbon dioxide to the atmosphere is demonstrated by the existence of a carbon dioxide concentration gradient within the cheese.

5. Storage of cheese at a lower temperature than is usual results in retarded carbon dioxide formation.

A method for the study of the diffuse reflexion spectra of dairy products in the near infrared region has been described. It has been shown that in this region of the spectrum, the reflexion method gives better results than the transmission method for butter and dried milk products. The effects of homogenization on milk spectra have been studied, and also the effects of temperature and mechanical working on the spectrum of butter have been considered. Assignments have been made for the bands observed in the dried milk spectra and the effects of moisture and other factors on the spectra of dried materials have been briefly studied.