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. A study has been made of the relative development of some regions in the fleece of twin lambs of a Suffolk ♂ × Suffolk (Border Leicester-Cheviot) ♀ cross during growth. The different regions develop in the following order: shoulder → leg → belly → tail. It is concluded that an improved animal is one in which the latest developing part of the fleece has the least possible number of undesirable fibres at the earliest possible age. The breeds of sheep begin their wool improvement by changes in the earliest developing regions (shoulder) and finish it in the latest (tail).

2. The properties of the fleece studied were the colour of the fibres, the medullated fibres, the fineness of the fibres, and uniformity of fibre size. In general a relationship is found between the stage and rapidity of development of the area, and the properties of the fibre. The intensity of the colour is stronger during the early active stages of development. There is a tendency to lose some kinds of coloured fibres, and to diminish the intensity of the colour in others as the development of each region in which the fibres grow proceeds.

The medullated fibres appeared in greatest quantities in the later developing regions, except the belly which presents few medullated fibres.

The staple is much finer at the first month of growth than in the later stages. Frequency curves of fibre size are of more value than average fibre size in estimating the value of the fleece.

3. It is suggested that the examination of the fleece of the lamb will give some idea of its genetic constitution and will reveal defects which would be concealed in the adult. Such a “phaeno-genetic” selection can be made best in a “late developing” area of the body such as the tail of the lamb at one month old.

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.

When a set of experiments involving the same or similar treatments is carried out at a number of places, or in a number of years, the results usually require comprehensive examination and summary. In general, each set of results must be considered on its merits, and it is not possible to lay down rules of procedure that will be applicable in all cases, but there are certain preliminary steps in the analysis which can be dealt with in general terms. These are discussed in the present paper and illustrated by actual examples. It is pointed out that the ordinary analysis of variance procedure suitable for dealing with the results of a single experiment may require modification, owing to lack of equality in the errors of the different experiments, and owing to non-homogeneity of the components of the interaction of treatments with places and times.

When this investigation was begun in 1929, the conception of intensive grassland management, involving rotational grazing and the liberal use of manures, including artificial nitrogenous fertilizers, was just coming into prominence in this country. It had become necessary to secure information about the improvement of yield and composition of herbage that could be brought about by such a system of management, since somewhat extravagant claims were being made for the magnitude of the effect of sulphate of ammonia and other soluble nitrogenous manures on the yield and composition of pastures.

This publication should be read in conjunction with the paper immediately preceding it in the present issue of this Journal (Woodman & Evans, 1938). It deals with a particular phase of the general problem described in the first paper, to which reference should be made for details about the wider objects of the trials, the design of the experiments and the different manurial treatments to which the subplots were subjected.

This paper deals with the final phase of the investigations described in the two papers immediately preceding it in the present issue of this Journal. These earlier papers may therefore be consulted for complete details concerning the general design and wider issues of the work as a whole (Woodman & Evans, 1938a, b).

In a previous paper (Pizer, 1937) it has been shown that the physical state of composted horse manure is of great importance as regards the growth of the mushroom mycelium. A granular condition obtained by flocculating the manure with small amounts of calcium—0·5 part of calcium per 100 parts of dry compost, wt./wt. —is most suitable for rapid, vigorous growth, while a dispersed greasy condition arising through a shortage of calcium is very unfavourable and may prevent growth entirely. In both flocculated and dispersed composts, mycelial growth is made more vigorous by small additions of a soluble phosphate, equivalent to 0·031 g. phosphorus per 100 g. of dry compost. Further experiments dealing with the practical application of these results are described in the present paper. The calcium compounds used were commercial flake calcium chloride (26),1 ground gypsum (24), superphosphate of lime (21) and hydrated lime (53), the latter being used in error for ground carbonate of lime (38). All these materials, except hydrated lime, were found to be satisfactory in laboratory trials for promoting mycelial growth, but the best results were given by the first three. The materials differ greatly in composition and properties, in ease of application and reactivity, and probably in their influence on the metabolism and productivity of the mushroom, and it was the main object of the experiments to discover the most suitable one for the grower to use.

Although it is well known that application of nitrogenous fertilizers to wheat often results in considerable increases in yields of grain and straw, and while experiments at Rothamsted and Cambridge have been very valuable not only in demonstrating the magnitude of the yield increases but also in showing how nitrogenous fertilizers bring about these increases, there is singularly little experimental evidence available regarding the increases in yield which may be expected in other parts of the country. Further, there is very little experimental evidence as to the optimum time of application of nitrogen, except at Rothamsted and Cambridge, both of which are in relatively dry districts.

The experiments of Briggs & Shantz led them to conclude that the “wilting coefficient” is a soil “constant” which is (a) independent of the kind of plant used as indicator, (b) independent of the conditions under which the plant was grown, and (c) directly related to several other soil constants.

Subsequent research as well as an examination of their own results has shown that (c) is untrue, while (a) and (b) are substantially correct for hygrophytes and mesophytes. Earlier writers have been led to wrong conclusions regarding (a) and (b) through assuming (c) to be correct and through disregarding the particular nature of “permanent wilting” as defined by Briggs & Shantz.

The fact that considerable variation is to be found between the osmotic pressure found in different plants, in different parts of the same plant and in the same part under different conditions is not at variance with conclusions (a) and (b) when properly understood.

An important factor making for the substantial constancy of the “wilting coefficient” for a given soil is the extreme steepness of the curve connecting suction pressure and soil moisture content, in consequence of which differences of suction pressure of unquestionable significance from the standpoint of plant physiology give rise to differences in soil moisture content that are too small to be detected.

Two procedures are described for ascertaining the relationship between the freezing-point and moisture content of a soil. Since the soil sample is dried in the process of freezing, it is necessary to estimate how much water has been frozen out of the soil at the moment when the freezing temperature is recorded.

Procedure A embodies all the precautions which appear desirable when the greatest accuracy is required. Procedure B is simple and rapid and yet accurate enough for routine estimations.

The results obtained in the preliminary investigation were entirely confirmed, the pF at the “wilting coefficient”, as measured by the modified freezing-point method, varied from 4·0 to 4·4 (round figures), with an average of 4·2.

The variation observed bears no relation to the soil texture, neither can it be explained by uncertainties in the freezing-point determinations which have proved to be accurately reproducible. Freezing-point measurements after leaching, conductivity measurements and freezing-point determinations in saturated soil and at the moisture equivalent proved that part of the variation is due to the presence of soluble salts, the more saline soils having a higher pF at the “wilting coefficient”. When the salt content does not exceed about 500 p.p.m. the influence of the salts is hardly detectable, and the pF at the “wilting coefficient” lies between 4·0 and 4·3. Besides unavoidable errors in the wilting experiments several other factors may account for this variation. They are all the factors that have any role in the “history” of the soil. In view of these uncontrollable sources of error a variation of 0·3 pF units can be considered very small.

It can therefore be confidently concluded that in ordinary agricultural soils with a salt content of less than about 500 p.p.m. permanent wilting occurs when a critical pF value (lying between 4·0 and 4·3) is reached.

The gaseous exchange of the sheep can be measured in the apparatus described with considerable accuracy and good agreement obtained with the energy absorbed from a maintenance diet. The apparatus automatically compensates for diurnal changes in temperature and humidity, and maintains a constant rate of ventilation.

The precautions necessary to ensure that the metabolism as measured is a good sample of that of the animal when subsisting on the diet, consist of control of temperature and humidity within the chamber and training the animal so that it is free of psychic strain during the period of measurement. It was found that the sheep takes 14–20 days to adjust its energy turnover to a change in diet.

Modification in structure and operation of the Haldane-Carpenter gas analysis apparatus are described in detail.

The method of A. C. Andersen is used to compute the energy metabolism and respiratory quotient from the gaseous exchange and methane production.

Critical estimations of the recovery of sulphur, when materials such as fodder and excreta were subjected to a number of analytical procedures. The only method in this series which resulted in consistently good estimations was one involving oxidation in compressed oxygen confined in an Emerson Calorimeter Bomb.

Measurements of the gaseous metabolism of sheep in this laboratory are conducted by drawing air through a sealed chamber that contains the animal, sampling the effluent air, and analysing the sample for its carbon dioxide increase and its oxygen deficit. As the analysis is dependent upon the measured fraction of nitrogen with rare gases, and particularly in respect of the oxygen deficiency this fraction must be known rather precisely. It is of course assumed that the animal in no way changes the quantities of nitrogen and rare gases passing through the chamber, but the analysis is incomplete if any gases or vapours other than carbon dioxide and water are given off.

It is well known that considerable quantities of methane, and possibly some hydrogen, are produced by ruminants, and some forms of gas analysis apparatus include a device designed to measure the concentration of methane in the sample. The device, as used in the apparatus of Carpenter & Fox (1926), consists of a platinum spiral heated electrically, the carbon dioxide resulting from combustion being measured volumetrically in the ordinary way, together with the O2 consumed. Experience with the device in this laboratory has led to its abandonment and gravimetric methods are now employed instead.

Attention has been directed to the occurrence of acetonuria in apparently healthy and in diseased cattle.

It has been shown possible to cause an alimentary acetonuria in milch cows experimentally by feeding large quantities of grass silage of the butyric acid type. The reaction of the urine remained alkaline and the ammonia content was within a normal range, showing that there was no real acidosis. The animals seemed by no means to be ill.

As to the cause of the acetonuria, a priori, there seemed to be little doubt that in these cases the ketones resulted, in the animal body, from the incomplete oxidation of the butyric acid of the grass silage. Yet, further experiments with a lactic acid silage containing no butyric acid at all indicated that the question may be more complex.