SummaryThe vapour/liquid equilibrium coefficient for benzyl mercaptan, which is the substance causing ‘landcress’ taint in butter from the milk of cows grazing pastures infested with the cruciferous weed Coronopus didymus, was found by use of a continuous vaporization equilibrium still to be 105 from solution in water and 1·30 from solution in cream of 30% fat content. It was concluded that complete removal of heatdeveloped landcress taint from cream would not be commercially practicable.

Summary A single injection of 100 i.u. ACTH given to milking cows had no statistically significant effect on the yield or composition of the milk. A long-acting preparation of ACTH, when given to cows in single doses of 200 and 400 i.u., depressed milk yield and raised the butterfat content of the milk. There was no significant change in the SNF content of the milk but the SNF content of the milk serum was increased. Three injections of 300 i.u. of long-acting ACTH given at 24-h intervals reduced yields of milk, fat and SNF and increased the fat and SNF contents of the milk. Small but generally consistent changes occurred in the butterfat characteristics of the milk of all groups treated with ACTH. There was a decrease in the iodine number and refractive index and a rise in the softening point of the fat in all the experiments. The Reichert value of the butterfat was lowered by single or multiple injections of the long-acting preparation. The carotene content of the butterfat was lowered by injections of the long-acting ACTH preparation but the vitamin A content was unaffected.

SummaryThe vapour/liquid equilibrium coefficients for the steam distillation of indole and skatole from water solution over the range of concentrations 0·1 to 20–30 ppm. were found to be 2·4 and 4·7, respectively. The coefficient for indole in a cream containing 30% fat was found to be 0·31, and for skatole, in a cream containing 40% fat, 0·14. It is concluded that complete removal of indole and skatole contaminations from cream by use of steam distillation equipment is not commercially practicable.

SummaryThe effects of depriving cows of pasture, for part or all of a single interval between the morning and evening milkings, on milk yield and composition have been investigated. The yields of milk and solids-not-fat, but not of fat, were reduced. The characteristics of the butterfat obtained at the first 2 milkings following grazing restriction differed markedly from those of cows allowed to graze normally.The changes observed suggested that the grazing restriction led to a temporary reduction in the supply of volatile fatty acids from the rumen and an increased utilization of fatty acids from body fat by the mammary gland.

SummaryIn two outdoor feeding trials with monozygotic twin cows during the spring and early summer months the effects of mature and immature H1 short rotation ryegrass on the composition of the butterfat produced and on the carotene and vitamin A contents of the butterfat and the blood were compared. In both trials the characteristics investigated were markedly affected by the stage of maturity of the grass. The butterfat from cows receiving immature ryegrass was more unsaturated and had higher carotene and vitamin A contents than that from cows receiving mature ryegrass. The blood of cows fed immature ryegrass also contained more carotene than the blood of cows fed mature ryegrass.It is suggested that variation in the stage of maturity of New Zealand dairy pastures throughout the year is an important factor contributing to the seasonal variations in the characteristics and the carotene and vitamin A contents of commercial butterfat. The influence of stage of maturity is probably associated with the quantity and nature of the pasture lipids.

Summary In an indoor feeding trial with three sets of monozygotic twin cows during late spring the effects of H1 short rotation ryegrass and white clover as feeds for the cows on the characteristics and the carotene and vitamin A contents of the butterfat were compared. The butterfat from the cows fed ryegrass had a lower iodine value and refractive index, higher Reichert and saponification values, and lower carotene and vitamin A contents than the butterfat from the cows fed clover. The carotene and vitamin A contents of the blood of the cows fed ryegrass were also lower than those of the cows fed clover In a subsequent outdoor feeding trial with four sets of monozygotic twins the feeding of pure H1 short rotation ryegrass or of perennial ryegrass was compared with the feeding of mixed pastures containing a high but varying proportion of clover. The results for the spring and early summer months were similar in direction but smaller in magnitude than those from the indoor feeding trial. In the result for the autumn months there was a reversal of the relationship for the characteristics and the carotene and vitamin A contents of the butterfat and for the carotenoid contents of the blood. It is suggested that the lack of consistency between the spring and autumn results could have been due to differences in the stage of growth of the ryegrass fed and that butterfat characteristics may be influenced more by the stage of maturity than by the botanical composition of the pasture.

SummaryMilk 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.

(I). Discarded deep-frying, fat, in the form of an emulsion, was given to milking cows at four times the dose-rate used for tallow in bloat prevention and control. Although the fat was highly oxidised, there was no effect on the flavour of the milk, cream, and butter, and no increase in the oxidisability of the butterfat. (II). Drenching of cows with “Pluronic” detergent L62 did not affect milk, cream, or butter quality, and did not cause any change in the characteristics of the butterfat. The detergent therefore can safely be used for the treatment of bloated animals.

MARKED and regularly recurring seasonal fluctuations in the characteristics of New Zealand butterfat have been reported by Cox and McDowall1. The iodine value, for example, rises to a maximum of about 41 in mid-winter, falls gradually until the beginning of October and then rapidly during October and November to a mid-summer minimum of about 34, and rises again during the autumn and early winter to the mid-winter maximum. The carotene and vitamin A contents of the butterfat also have been shown by McDowell and McDowall2 to change according to a regular seasonal pattern, with maximum values in the early spring and minimum values in mid-summer. These latter changes have been found by McGillivray3 to be a reflexion of changes in the carotene and vitamin A contents of the blood plasma.

SummaryBatches of cream inoculated with 1% of a culture of Streptococcus diacetilactis or of one or other of two mixed starters were held at different temperatures over the range 37–57°F before churning. Diacetyl and acetoin were estimated in the creams at churning and in the butters fresh and after storage.The diacetyl production of all three starters in the cream increased with increase in temperature, although at the lower temperatures there was no indication of any rise in titratable acidity. At 52 and 57°F there was some rise in acidity during the holding period.The butters were of good keeping quality. There was a small but definite reduction in the diacetyl content of the butters during storage, but the extent of the change was not related to the holding temperature of the creams.It was concluded that if sweet cream starter butter is to be made with uniform intensity of flavour the proportion of starter added must be adjusted to counterbalance changes in the cream-holding temperature.

Summary The use of starter cultures prepared 3 days, 2 days and 1 day before inoculation at the 1% level into cold cream in the making of sweet cream starter butter was investigated. With Streptococcus diacetilactis starter there was little effect of age of starter on diacetyl production in the cream and on the quality of the fresh butter, but when 3-day-old culture was used in the cream there was a slight reduction in the butter quality after 4 and 8 months' storage. With the mixed commercial cultures Camb and F.D. increase in age of the culture led to reductions in diacetyl production in the cream. The difference was attributed to the effect of holding for the longer time under acid conditions on the equilibrium between streptococci and leuconostocs in the mixed culture. The age of the Camb culture had no effect on the grade of the butter, but holding the F.D. culture for 3 and 2 days instead of for 1 day caused a fall in grade of the butter after storage for 4 and 8 months at 14 °F.

Summary Production of diacetyl and acetoin by starters in cold skim-milk and cream was shown to increase with increase in the proportion of starter culture added, with some limitations at the higher rates of starter addition. With Streptococcus diacetilactis starter in skim-milk at 50°F the relation between proportion of starter added and production of diacetyl was linear up to addition at the 4% level, whereas at 43°F it was approximately linear up to the 10% level. At both 50 and 43°F the relation between the proportion of starter added and the production of acetoin was linear up to the 10% level. With Camb starter in skim-milk at both 50 and 43°F there were regular increases in production of diacetyl up to the 4% level of addition, but only minor changes thereafter with increase in the proportion of starter added up to 10%. At both temperatures the maximum production of acetoin was reached with the 7% rate of addition. Production of diacetyl and acetoin in skim-milk was greater at 50°F than at 43°F with both starters for all proportions up to 10%, and it was greater for Str. diacetilactis than for the mixed cultures. Except at the higher rates of addition of starter and at the higher temperature there were no concomitant increases in the acidity of the milk or lowering of the pH values. It appears that at low temperatures production of diacetyl by starters in sweet milk and cream proceeds independently of production of lactic acid. Similar results were obtained in a series of experimental buttermaking trials and some small commercial-scale trials, in which varying proportions of starter were added to creams after pasteurizing and before holding overnight for churning. With the cream-holding temperatures used, mainly 40–50°F, the pH values of the butters were not appreciably lowered by the starter additions to the cream. At all the rates of addition there were with Str. diacetilactis starter higher contents of diacetyl in the butter than with Camb starter. There was no indication of any relationship between the proportion of starter added and the keeping quality of the butter.

Summary Cows were treated prior and subsequent to parturition with 150 ml of heavy liquid paraffin B.P. daily, a dose rate previously found effective for the control of bloat. The treatment had no effect on milk and fat yields. It did not cause any change in the levels of carotene, xanthophyll, vitamin A, and tocopherol in the butterfat in the first milk drawn after parturition but it caused in subsequent samples a marked increase in the rate of post-parturition fall in levels of carotene, vitamin A ester and tocopherol, and a slight increase in the rate of fall of xanthophyll level. It did not affect the vitamin A alcohol content of the butterfat. Because of its marked effect on the colour of early post-colostral butterfat, treatment of cows with heavy liquid paraffin for bloat control could be expected to lower the depth of colour of spring-made butter. The treatment with paraffin caused marked decreases in the levels of carotene and tocopherol in the blood, which, near parturition, were superimposed on the changes in the levels normally occurring at that time. There was no evidence of any effect of the paraffin treatment on the health of the cows before, during, or after parturition. The only result of any nutritional importance was the reduced vitamin potency of the colostrum for calf feeding.

Summary Procaine penicillin was given every third day to one cow of each of three monozygous twin pairs. The rates were 100,000 units per dose over a period of 15 days, 500,000 units per dose over a period of 12 days, and 200,000 units per dose over a period of 5 months. There was no evidence of transfer of penicillin to the milk. There was no adverse effect on the weights of the cows, on the yields of milk and butterfat, on fat and solids-not-fat contents of the milk, or on the iodine value, saponification value, softening point, Reichert value, carotene content, and vitamin A content of the butterfat. On this evidence it appears that penicillin may safely be used under New Zealand conditions for treatment and control of bloat at dose rates up to 500,000 units every third day.

1. Measurements, by means of a continuous vaporization equilibrium still, of vapour/liquid equilibrium relationships in the steam distillation of dilute aqueous solutions showed that for mesityl oxide the relationship was linear, equilibrium coefficient (CV/CL)= 74.2. For acetylpropionyl it was linear over the concentration range l–10 p.p.m. in the liquid, CV/CL=51, and above a concentration of 20 p.p.m. it was again approximately linear. At 20 and 50 p.p.m. in the liquid the values found for CV/CL were 34 and 21·5 respectively.3. For acetyl-iso-butyryl it was not linear even at very low concentrations, of the order of 1–3 p.p.m. in the liquid, but there was an approach to linearity at concentrations 0–1 p.p.m., CV/CL=240. At concentrations above 1 p.p.m. in the liquid there was a steady fall in the value for the equilibrium coefficient.4. For acetylvaleryl it was curvilinear even over the concentration range 0·1–4·0 p.p.m. in the liquid. At 0·5–1·0 p.p.m. in the liquid the equilibrium coefficient was of the order of 240. Above a concentration of 4 p.p.m. in the liquid the relationship was linear.5. For acetylcaproyl it was approximately linear only over the concentration 0·1–0·4 p.p.m. in the liquid, CV/CL=180. At 4 and 8 p.p.m. in the liquid the coefficients were 90 and 70 respectively.6. For acetylbenzoyl it was curvilinear at low concentrations, i.e. 0·1–0·5 p.p.m. in the liquid, CV/CL=30 decreasing to 16. Above this concentration there was a gradual fall in the equilibrium coefficient to 11·5 at 70 p.p.m. in the liquid.7. Of the substances investigated only diacetyl and acetylpropionyl and, within limits, acetylbenzoyl were considered to be of suitable properties for use as reference substances in detailed investigations on cream deodorization equipment.