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SummaryTwenty-one Jersey cows in their 6th–8th week of lactation grazed Chloris gayana pastures fertilized with nitrogen and were treated in three ways, no casein (control), casein (1 kg/cow/day) or formal-casein (1 kg/cow/day) in seven 3 x 3 Latin squares to measure the effect of protein protection on milk yield and milk composition. Additional animals fitted with oesophageal and rumen fistulae were used to determine composition of the diet selected and rumen characteristics on three treatments.Cows ingested herbage containing 20% crude protein with a protein solubility of 40%. The untreated casein supplement increased milk yield by 3%, fat 5% and protein 2·4%. Formal-casein produced 20% (3·3 kg/day) more milk than the control, a 13% higher yield of butterfat and 27% more protein. Rumen ammonia concentrations in the afternoon were similar for the control and formal-casein supplemented cows (21 and 23mg/100ml) but significantly higher when casein was fed (74 mg/100 ml) indicating extensive deamination of the untreated protein.Yields of C4–C16 fatty acids in milk fat were 8 and 21% higher for the casein and formal-casein treatments than for the controls, which together with the higher live weight of formal-casein supplemented cows indicated that the milk yield response to the protein supplements was mainly due to a higher daily intake of herbage.

SummaryTwenty-four lactating Jersey cows, grazing a 3-week regrowth of nitrogen-fertilized Chloris gayana cv. Pioneer pastures selected a diet containing 18% crude protein and were given 0, 2 or 4 kg/day of fresh Leucaena leucocephala or 250 g/day of formal-casein. The effect of the treatments on milk production was measured in a 4 × 4 latin-square design experiment with experimental periods of 14 days.Mean milk yield of unsupplemented cows was 9·6 kg/day, 10·1 kg/day when cows were supplemented with formal-casein and 10·3 kg/day when fed 2 or 4 kg Leucaena/day. Yields of solids-not-fat, protein, casein, butterfat and short and medium-chain (C4–C16) fatty acids in milk fat were higher when cows were fed supplements (P < 0·01). Intake of digestible organic matter was lowest on the unsupplemented diets although feed in excess of 40 kg D.M./cow/day was offered and cows had little difficulty harvesting feed with a mean bite size of 350 mg organic matter/bite and mean grazing time of 507 min/24 h.It was concluded that a tropical grass diet containing 18% crude protein was deficient in protein for lactating cows and that small quantities of the legume Leucaena can alleviate such a deficiency.

SUMMARYThe effects of temperature and method of feeding on the intake characteristics and digestibilities of two milk substitutes were examined.Forty Finnish Landrace x Dorset Horn lambs (20 males and 20 females) were fed one of two milk substitutes from 3 to 25 days of age when they were slaughtered and chemical composition of the empty body was measured.The two milk substitutes contained 30% fat in the dry matter as butter fat (diet B), or tallow and coconut oil (diet TC).The diets were offered at either 34°C (W) or 5 °C (C) and three methods of feeding were used. The diets were given: ad libitumcold (AL1), four feeds to appetite per day either warm or cold (AL2W and AL2C) and four feeds restricted to an intake of 62 g D.M./kg live weight0·5 either warm or cold (RW or RC).Digestibilities of the milk substitutes were not affected by the temperature at which they were offered or the feeding regime used. Diet B had an apparent dry-matter digestibility of 97·6% and diet TC 92·5%. The fat digestibility of diet TC was 13·6 units lower than diet B and this affected the digestibility of all the other dietary components.Lambs tended to consume more of diet B and grow faster.Lambs on treatment AL1 consumed 21% more milk substitute than those on treatment AL2.The composition of the body-weight gain was found to alter with rate of gain.The temperature at which the milk substitutes were offered had only a minor effect on the performance of the lambs. The type of milk substitute and feeding regime used had a greater influence on both lamb intake and growth.

SummaryThree experiments were carried out to study the effect of replacing milk carbohydrates and part of the milk fat in milk with partially hydrolysed starch (Protamyl 110). Male and female cross-bred lambs (Suffolk × (Finnish Landrace × Dorset Horn)) were used in these experiments. They were weaned from their dams after having received colostrum at 1–2 days of age. The experimental diets were given at room temperature, in eight aliquots, at 3-h intervals through an automated feeding unit. The level of feeding was 1·05 MJ/kg0·75 live weight/day.In the first experiment, the diets were formulated to contain 28, 17 and 55% of their gross energy as protein, carbohydrate and fat respectively. Diet 1 contained glucose, while diets 2, 3 and 4 had 33, 67 and 100% of glucose respectively replaced by Protamyl. There were no significant differences in growth rate and food utilization between levels of starch inclusion.In Expt 2, the maximum Protamyl that could be incorporated in lamb milk replacers was examined. Four experimental diets were prepared so that 17 and 55; 25 and 47; 33 and 39; and 41 and 31% of their gross energy was supplied by Protamyl or butter fat respectively. It was found that up to 33% of the gross energy of the diet (41% of the dry matter) could be replaced with Protamyl without adverse effects on lamb performance. When the level of inclusions was increased to 41% of the gross energy (49% of the dry matter), lamb performance was depressed, particularly during the first 15 days of the experiment.In Expt 3, a direct comparison was made between Protamyl and lactose. The two diets used were similar in composition to diets 1 and 4 in Expt 1, except that lactose was used as a control instead of glucose. There were no differences in growth rate or food utilization as a result of replacing lactose with Protamyl.The results are discussed in relation to the development of carbohydrases in new born ruminants.

(1) Further experiments are described, the results of which support the relationship between the presence of vitamin A in the diet of the cow and its presence in milk fat.(2) The typical winter ration of concentrates, roots and hay may be adequate to maintain the vitamin A value of the milk fat for considerable periods provided that at least one of the components supplies adequate amounts of that dietary principle. Well cured green meadow hays are in this respect greatly superior to dry brown seeds hays.(3) The addition of cod liver oil to a winter ration deficient in vitamin A will induce a sharp rise in the vitamin A value of the milk fat of cows. No such effect is seen when oils deficient in this dietary factor (coconut oil, arachis oil) are given.(4) The administration of cod liver oil in doses from 1 to 8 ozs. daily to milking cows caused no “fishy” taint in the milk or butter-fat.(5) The administration of cod liver oil caused no appreciable change in the yield of milk but the higher doses appeared to cause a noticeable drop in the percentage of fat. Further experiments are required to throw more light on this observation.

1. An experiment was carried out from 1 August 1953 to 31 July 1955 to compare strip grazing with rotational grazing on the basis of the total animal production obtained from dairy cattle on irrigated pasture.2. The same overall stocking rate was used for both treatments. Herbage surplus to grazing requirements at any time was conserved as hay and fed back to the appropriate group of cows at the end of the grazing season.3. The aim was to manage the area under each technique as efficiently as the technique permitted.4. The average production from the rotationally grazed group during the main pasture season of 260 days was 8740 lb. milk per acre (including 354 lb. of butterfatand 766 lb. of solids-not-fat) and from the strip-grazed group 8867 lb. milk per acre (including 358 lb. of butterfat and 766 lb. of solidsnotfat).The average weight of pasture nutrients utilized per annum by the rotationally grazed group was 5887 lb. starch equivalent per acre and by the stripgrazed group 5896 lb. starch equivalent per acre.None of the treatment differences in animal production was significant.5. The differences between the results of this experiment and those obtained by other workers are discussed.

1. On the basis of 5000 records from twelve leading herds of Ayrshire cattle in south-west Scotland for the period 1930–9, a statistical study has been made of some of the causes of variations which occur in butterfat percentage.2. Butterfat percentage was found to be affected only very slightly by month of calving, age and length of calving intervals.3. Selection for milk yield would not affect butterfat percentage adversely to any appreciable extent.4. The average repeatability of butterfat percentage was 0·691 in the present material, and heritability was of the order of 0·50–0·60.5. Mass selection would be an effective tool in bringing about improvement in butterfat percentage.

1. Pasture parameters have been correlated with animal production parameters from a trial in which two management systems (‘controlled’ and ‘uncontrolled’ grazing), each at two stocking rates (0.95 and 1.19 cows/acre), were compared.2. Per acre butterfat production was positively related to percentage utilization of available D.M., but negatively related to yield of available D.M.3. Per cow butterfat production was significantly and positively correlated with yield of available D.M. in the two months after calving (August and September) and in the penultimate month of lacta-tion (April), but this correlation was not significant in other months.4. It is concluded that management system was as important as stocking rate in increasing the utilization of pasture and animal production from pasture.

1. The variations in production due to age have been investigated with the records of 738 Ayrshire cows for 4380 lactations.2. Milk and butterfat production increase up to about 7 years of age and then show a decrease.3. The fat percentage for 3-year-olds is higher than that for older cows.4. After 3 years of age there is little change in the fat percentage with age that is of any practical significance until advanced ages are reached, when there may be a fall of importance.5. The increase in production associated with age is probably attributable, in part, to the growth of the secretory tissue of the udder and to body growth in general.6. Part of the increase may also be due to an improvement in functional activity through use.7. The tendency for milk to show a slightly lower fat percentage as the cow advances in age is probably due to the fact that as the milk yield changes the fat yield changes in the same direction but at a slower rate.8. There is little known regarding the influence of very advanced age on production, but it is probable that many cows maintain for a long time the production associated with maturity, and then decline slowly.9. Heifers with a low fat percentage need not as a rule be expected to test higher on reaching maturity.10. It is probable that the increase in production with maturity is associated more closely with high initial production than with persistency of production.11. Correction factors for age are presented.

A survey of some environmental and physiological factors influencing milk yield and an analysis of theories of and experiments on milk and butterfat inheritance have been made.Further evidence is given of the fact that the proved dairy sire is the outstanding medium through which improvement in dairy cattle breeding may be effected. The need of (1) prolonging the breeding life of such an animal and (2) evolving a scheme for the regular progeny-recording of all dairy sires is emphasised.The minimum number of unselected daughters necessary to give a reasonably accurate indication of their sire's transmitting ability is six.

Wherever the opium poppy is cultivated its seed forms a valuable secondary crop. India has a bigger outturn of seed than any other country. In the years immediately preceding the war the bulk of the poppy seed produced in India was exported. The following Table gives an idea of the proportion of the total production exported for a number of years past.

The study of lactation has almost always been undertaken from one of two very diverse points of view, the physiological and the commercial. The chief aim of the physiologist has been to determine, either the origin of the various constituents of the milk and the method of their elaboration, or the extent to which internal secretions affect the flow of milk by their initiation, inhibition or stimulation of milk secretion. From the commercial or agricultural point of view, on the other hand, the chief interest has centred round the problem of the production of butter fat, and a very large number of experiments have been conducted to determine by what method of feeding a cow could be caused to give the maximum yield of milk with the highest percentage of fat.

1. From an analysis of the records from 702 cattle of predominating Jersey type tested for at least six consecutive years under normal and average herd conditions in New Zealand, the authors have attempted a detailed study of the nature of the increase in production according to age.2. They are unable to find any evidence supporting the theory that increase in production for dairy cattle operates as a percentage addition from early age to maturity.3. The evidence secured from an analysis of 702 Jersey records of six consecutive lactations commencing at 2 years of age, strongly suggests that the increase in production according to age can be summarized neither by a percentage addition nor a constant addition alone, but is best represented by a regression formula of the nature X = aY + b, where X equals the maturity production and Y the immature production.4. The strict regression formula will probably change according to the interpretation of “maturity equivalent”, but in general its application should lose little of the simplicity of the ratio form of conversion.

1. The transferrin types of 225 Jersey cows in thirteen herds, and 433 Australian Illawarra Shorthorn cows in twenty-four herds in Queensland were determined. The effect of transferrin type on lactation length, milk yield, butterfat yield and butterfat percentage was assessed by a leastsquares multiple linear regression analysis.2. The results for the two breeds did not differ significantly. Combining the data from both breeds, it was found that on average D/D cows had lactations 13·9 days longer than A/A cows (P < 0·01), and yielded 449·7 lb. more mills (P < 0·01). The results for A/D cows were intermediate.

1. Milk and butterfat production rise to about the sixth lactation, but beyond the fifth lactation the increase may be neglected.2. The lactation of maximum production may be taken as the fifth which corresponds to 7 years of age.3. Beyond the fifth lactation the milk and butterfat yields vary irregularly but show a downward tendency.4. The fat yield shows either a fall or only a very small increase in the second lactation.5. The fat percentage is highest in the first lactation, drops markedly in the second, remains fairly steady for a few lactations, though with a slight downward tendency, and then falls off in the higher lactations.6. Results obtained by applying correction factors for either age or lactation are quite comparable and choice in the method to be used will depend largely on the original data available.

1. An experiment with dairy cows is described in which the production per animal and per acre obtained in three methods of grazing management were compared during 2 years.(A) An intensive method. Strip-grazing daily on heavily fertilized grass sward.(B) A modified intensive method. Continuous, free-range grazing on a heavily fertilized grass sward.(C) An extensive method. Continuous, free-range grazing on a grass and clover sward receiving a basic application of phosphate and potash only.The intensively fertilized swards received a total of 212 lb. fertilizer nitrogen per acre, together with adequate amounts of phosphate and potash throughout the grazing season. No supplementary foods of concentrate type were fed to the cows during the experiment.2. For the comparison of production per animal 3 × 3 Latin-square experimental design, with twelve Ayrshire cows and periods of 3 weeks' duration, was used. Two separate trials were conducted during the grazing season of 1955 and a third trial during 1956.3. The different methods of grazing management and intensive use of fertilizer had little influence on the milk yield and butterfat percentage of the milk of the cows.

Part of the variation among butterfat yields in dairy cows arises from genetic differences among the animals. The proportion which this bears to the total variance is known as heritability. In the ‘narrow’ sense it is defined (Lush, 1940), as the proportion of the total variance that is due to additive gene effects; the ‘broad’ sense definition includes genetic variation arising from non-additive gene effects as well as that due to additive effects. Since related animals have a proportion of their genes in common the covariance among their production records can be used for estimating genetic variation and hence heritability. This paper discusses three groups of related animals most frequently used for this purpose, twins, daughter-dam pairs and paternal half-sibs, and presents the results of analysing production records of artificially bred heifers in New Zealand, including evidence of the magnitude of the sampling errors of the heritability estimates.

SUMMARYComplete diets were given ad libitum to dairy cows over a whole lactation in order to study the voluntary intake of food, lactation performance and efficiency of feed conversion. The effect of including four levels 16, 24, 32 and 40 % of coarsely milled barley straw in the loose mix was studied for diets based mainly on barley or on sugar beet pulp, using a double 4 × 4 Latin square design.The results confirmed that cows can perform normally when given complete diets for extended periods. Dry matter and digestible energy intake was depressed at the higher levels of straw inclusion and milk butterfat content at the lowest level. The net efficiency of conversion of metabolizable energy (M.E.) into milk was higher at the higher levels of straw. It is concluded that complete diets for the self-feeding of dairy cows should contain a minimum of about 24 % of coarsely milled straw and that estimated metabolizable energy intake and production were depressed by including straw at higher levels.

SUMMARYTwelve Friesian heifers were given four dietary treatments from 2 months before first calving to the end of the first lactation. Two of the treatments involved thead libitumfeeding of a complete diet consisting of a basal concentrate meal of rolled barley with supplements, incorporated into a mixture with either hay or barley straw both coarsely ground and included at a level of 25 % of the complete mix. In the other two treatments either the hay or the straw was givenad libitumin the long form and the concentrate mix fedad libitumfrom a separate self-feeder.Full records were kept of the intake of food and water, the output and quality of the milk and of live weight. Detailed measurements were made of various aspects of rumen function using one cow on each treatment fitted with a cannula. Rumen samples were also obtained from non-fistulated cows by stomach tube.The intake of long roughage, particularly straw, by the cow, when offered in conjunction with a separate supply of the concentrate mix, was very low and led to serious falls in milk butterfat content. Where the roughage was incorporated into the complete diet normal butterfat levels were maintained. However, apart from the depressed butterfat levels on the two long roughage treatments the health and condition of the cows remained good.The very low intake of long straw was associated with a smaller volume of liquid in the rumen, a reduced rate of flow of liquid leaving the rumen, a lower proportion of acetic and butyric acids and a greater proportion of propionic acid in the rumen liquor and finally with a higher blood glucose content. The inclusion of milled roughage resulted in values within the normal range for volume of liquid in the rumen, flow rate of liquid from the rumen, V.F.A. proportions in the rumen liquor and blood glucose.The intake of both food and water over the productive cycle showed a consistent pattern for all cows. Food intake reached its lowest point around calving followed by a sharp rise to a peak in the 4th month after calving and then a gradual but increasing decline. Water intake followed a similar pattern but the fluctuation was greater and the peak consumption occurred in the 3rd month of lactation. Water intake was more closely associated with D.M. intake than with milk output.The efficiency of utilization of the complete diets containing the milled roughages is discussed in relation to comparable data from cattle fed conventionally.

A review of published work emphasizes the existence of a fundamental relationship between the quantity of milk and butterfat per cent. This general relationship may be stated thus: as the quantity of milk increases, the quantity of fat increases also, but at a slower rate. Therefore, the fat per cent, or concentration, falls as the volume of milk increases.

1. A description is given of an adaptation of the Latin square lay-out to experiments with dairy cows. Experiments were conducted to test the effect of adding various fats and oils to the ration, and since effects were rapidly produced the Latin square technique proved very efficient, experimental errors being rather lower than those usually obtained in experiments with crops.2. Seventeen separate experiments, including, in all, twenty-one different cows (many of whom were used more than once), were conducted; fourteen of these were short-term experiments with unit periods of 5 days, two were medium-term with unit periods of 10 days and one long-term with 20 days.3. Palm oil, butter, lard and possibly cotton-seed oil were found to increase butterfat yield, chiefly by raising the butterfat percentage of the milk. Soya-bean, linseed and whale oils were without effect. Cod-liver oil definitely decreased butterfat percentage and butterfat yield.4. It appears that the beneficial oils are those containing a large proportion of the saturated fatty acids.5. Experiments with the same oil were not always consistent, and it appears that the effect may vary from cow to cow, and also with the same cow at different times.

1. The serum β-globulin phenotype of 141 bulls located at Cattle Breeding Centres in England and Wales was determined by starch-gel electrophoresis.2. The distribution of the contemporary comparison values of these bulls with respect to β-globulin type was investigated. The great majority of the bulls were βAA, βAD, or βDDwith very few βAEand βDEand no βEEtypes.3. The contemporary comparison values for 130 bulls of the three types βAA, βADand βDDeach fell into a normal distribution. The mean and its standard error and the standard deviation of the mean and its standard error were calculated for each of the three curves. The mean contemporary comparison value for the βAAbulls was + 12·2 ± 5·4 gal., for the βADbulls + 26·8 ± 5·4 gal., and for the βDD bulls + 38·2 ± 5·5 gal. The βAAand βDDmeans were significantly different (P< 0·01).4. The pooled contemporary comparison values of the βAA, βADand βDDbulls did not give a normal distribution curve, neither did the contemporary comparison values for a sample of 1028 bulls quoted by the Milk Marketing Board. However, when the contemporary comparison values of the βAA, βADand βDDgroups were superimposed around the same mean, the ensuing distribution was normal.5. It is concluded that the β-globulin locus is concerned in the genetic control of milk yield. The estimated mean genetic value of βDover βAis approximately + 50 gal. This is about one-sixth of the total genetic variation in milk yield in the major milk breeds.6. The distribution of butterfat percentages with respect to β-globulin phenotype in four Ayrshire and one Friesian herds was investigated. No difference between the mean first lactation butterfat percentage of the βAA, βAD, and βDDcows in each herd was found. There was an indication (not significant) that the mean butterfat percentage of the βAEand βDEcows in three of the four Ayrshire herds studied was higher than the mean of the other groups.

1. Material is presented which shows month by month the lactation yields of cows in respect of milk and fat. Morning and evening yields are treated separately and differences in relative proportions found.2. Smaller proportions of milk and of fat at the morning milkings are yielded in early lactation by all cows, but this point is most pronounced in heifers and also in heavy yielding cows with relatively small udders. It is suggested that with such animals reabsorption of milk occurs during a long night interval.3. Seasonal variations in yield of milk and fat are shown. It is found that the morning milking does not respond as much as the evening milking to the stimulus to secretion which functions during May and June.4. The quality of milk at different seasons of the year is discussed.

Fourteen pairs of monozygous twin cows of mixed ages were used to determine the effect of underfeeding from the 3rd to the 8th week inclusive after calving on milk and butterfat production and on the composition of the milk.Those cows which were well fed over the 6-week period produced more milk and a larger weight of butterfat than their sisters which had been poorly fed. The milk from the well-fed cows had a lower percentage of butterfat, but higher percentages of solids-not-fat and total protein, than the milk from the poorly fed cows.The complete lactation averages failed to show statistical significant differences in all characteristics except in the case of solids-not-fat percentage. The mean difference between the two groups for solidsnot-fat was found to be highly significant.In general, the results support the conclusions of other workers, that underfeeding dairy cows may depress the solids-not-fat content of the milk.It appeared that differences between the two groups in butterfat percentage over the 6-week experimental feeding period were strongly correlated with differences in weight changes and that the small amount of variance associated with milk yield differences was not significant.