1. An experiment is described in which the effect of the level of nutrition, as determined by stocking rate and the use of supplementary concentrates, on milk yield and efficiency of production was studied.

2. Three levels of nutrition were used: Treatment (A)—one milking cow per acre plus 1 lb. of concentrate mixture for each 5 lb. of milk produced. Treatment (B)—one milking cow per acre—no concentrates. Treatment (C)—one milking cow per sixtenths of an acre—no concentrates.

3. Fifteen sets of identical twins were used per year over an experimental period of 3 years. The groups were rotationally grazed with a daily shift to a fresh pasture on a 14-day rotation. Ninety complete lactations were available for analyses.

4. The A cows produced 45% and the B cows 16% more f.c.m. than the C cows. Per unit area, however, the C treatment produced 30% more than the B.

5. Significant differences in milk composition were established, but these were of much smaller magnitude than those in milk yield.

1. Ammoniated invert molasses when used as a food for yearling dairy cattle proved toxic in doses of 1 lb. per day.

2. When ammoniated invert molasses had been acidified with phosphoric acid the toxicity was markedly reduced but not entirely eliminated. Ammoniated molasses acidified with acetic acid produced no toxic effects but the live-weight responses of yearling cattle was inferior to a ration markedly deficient in protein. The poor responses may have been partially due to the unpalatability of the ammoniated molasses.

3. The ammoniated molasses used in experiment 1 did not produce toxic symptoms in rats but it did result in reduced food consumption and poor growth.

4. The ammoniated molasses treated with acetic acid, when included at the rate of 10% of the diet of guinea-pigs, depressed appetite and caused toxic effects.

The addition of essential amino acids to all-vegetable diets, so as to raise the biological value of their proteins to the level of animal-protein concentrates, has often been advocated in the past by animal nutritionists. This aim was frustrated in practice since it was impossible, until recently, to secure the necessary supplies at prices that would make such additions economical. Feeding stuffs with added amino acids are now being sold commercially. This is possible following the manufacture of synthetic DL-methionine and crude L-lysine monochloride.

It seemed desirable, therefore, to carry out investigations into the potential value of these amino acids to the pig feeder. This paper deals with the effect on growth, food utilization and retention of nitrogen of adding small amounts of lysine and methionine to the diet. An attempt is made to correlate the amino acid composition of the pig's diet with its rate of growth, the energy supply being adequate.

The effect of short leys and arable cropping on the yields of the following arable crops has been tested since 1937 at Woburn Experimental Farm, Bedfordshire. The leys were a 3-year grazed ley and 3 years of lucerne cut for hay and the arable cropping was potatoes, winter cereal and either a 1-year ley or a third tillage crop. The effects of these crop sequences were measured by test crops of potatoes and barley, uniformly treated except that 15 tons farmyard manure was applied on one-half of each plot for potatoes.

Without farmyard manure, the yield of potatoes after the grazed ley was higher than after three tillage crops by an average of about 3 tons per acre; after lucerne it was about 2 tons per acre more than after the tillage crops and after the 1 -year ley under 1 ton per acre more. With farmyard manure the benefit from leys was less (about 2 tons per acre for both lucerne and the grazed ley). The average effect of the farmyard manure was about 2·8 tons except after the grazed ley, where the increase was only 1·6 tons per acre.

Effects of the previous cropping on the yield of barley were small in the early years of the experiment, but in the last 5 years the yield after ley and lucerne has exceeded that after the tillage crops by about 15%.

Part of the difference in potato yield between the ley and arable sequences can be attributed to the differential incidence of potato-root eelworm, which has reached a high level of infestation on some of the arable plots. Much of the remainder may be ascribed to the low level of basal manuring which has affected the yield of all plots, but particularly those under tillage crops. How far the observed differences can be explained by these considerations remains a matter for speculation, but may to some extent be clarified when further results are obtained from a revised scheme of cropping and manuring.

A conservation experiment is described in which a comparison of the nutrient losses and quality of sodium metabisulphite silage and molassed silage is made. The loss of dry matter in molassed silage is shown to be 3·5% higher than in metabisulphite silage.

The lactic-acid content of metabisulphite silage is found to be some 40% less than that of molassed silage.

The results obtained are discussed in relation to published work on conservation by metabisulphite and to the practical application of the method.

1. An attempt was made to verify a report that mixed samples of bull semen show better motility and survival than their unmixed controls.

2. The claim was not confirmed; in 83 of 104 samples the motility score of the mixed sample was less than the score for the better individual constituent sample.

1. Ten experiments on spring barley (mainly Proctor) and four on spring wheat (mainly Atle) in 1954–6 compared 0·25 and 0·5 cwt. N/acre (as ammonium sulphate) when drilled with the seed, with dressings broadcast before sowing. Tests were also made of ‘Nitro-Chalk’ dressings given in mid-May. In heavier split applications seedbed dressings were supplemented by top-dressings of 0·5 cwt. N/acre.

2. Barley gave much larger average responses than wheat. For barley combine-drilling 0·25 or 0·5 cwt. N/acre gave consistently larger yields than broadcasting the same nitrogen dressing on the seedbed; for wheat combine-drilling gave slightly higher yields at the high rate of dressing only.

3. For both crops 0·5 cwt./acre of N drilled with the seed was almost sufficient for maximum yields, but where only 0·25 cwt. N was applied at sowing a mid-May top-dressing of 0·5 cwt. N/acre gave higher yields.

4. At most centres May top-dressings of ‘Nitro-Chalk’ gave lower yields than equivalent ammonium sulphate drilled with the seed. Yields were often reduced by lodging on plots which received seedbed dressings plus top-dressing or the heavier rates of top-dressing alone; these treatments also reduced the quality of the grain. Combine-drilled or broadcast seedbed dressings did not cause serious lodging or reduce grain quality.

5. 0·25 or 0·5 cwt. N/acre broadcast on the seedbed or combine-drilled had little effect on the percentage of nitrogen in the grain; equivalent topdressings in mid-May consistently increased nitrogen content. Seedbed dressings plus top-dressings supplying heavier total quantities of nitrogen continued to increase nitrogen percentage in grain without giving any increase in yield.

Leaf-rust infection of severity 3–4 on the modified Cobb scale reduced the dry-matter yield of Dun oat leafage by 30% and N.I.A.B. ryecorn by 23%. The reduction in root growth of ryecorn was similar to that of the aerial parts.

The dry-matter percentage of the green forage was significantly increased in two of the three experiments. Palatability reduction due to leaf rust is suggested from field observations.

With Dun oats leaf-rust infection increased the percentage of crude protein (C.P.) by a fifth, of ash by a tenth and decreased that of crude fibre (C.F.) by an eighth, and of nitrogen-free extract (N.F.E.) by a nineteenth. With ryecorn, rust increased the percentage of c.p. by a fourteenth, of ash by a fifth, and decreased that of N.F.E. by a twentieth.

The decreased forage yield caused by rust is in accord with the results of experiments of other research workers and with field observation. The effect of rust on proximate constituents was interpreted as an improvement to feed value. This agrees with the results of most reported experiments but conflicts with the field evidence.

The hypothesis that leaf rust affects forage composition mainly by reducing the physiological age of cereals is proposed.

Three calves (Australian Illawara Shorthorn, Shorthorn and Zebu × Australian Illawara Shorthorn) were exposed to different combinations of wet- and dry-bulb temperatures in a psychrometric chamber at the Physiology Department of the University of Queensland. These animals were 2–3 months old when first exposed to heat.

Measurements were made on these animals for cutaneous and respiratory water losses, and skin and rectal temperatures.

Cutaneous water losses in all the animals studied increased with increases in air temperature. Comparing these results with those on men with congenital absence of sweat glands exposed to high air temperature below the sweat point, suggests that the cutaneous evaporative losses in cattle are more than those that can be accounted for by diffusionmoisture alone.

Increase in cutaneous evaporation under hot conditions is accompanied by increase in skin and rectal temperatures. In the Zebu cross, however, the skin temperature did not rise with rise in air temperature.

Keeping the humidity constant, rise in dry-bulb temperature caused increase in respiratory water loss. On the other hand, rising humidity at a constant dry-bulb temperature resulted in decrease in respiratory evaporation. Respiratory evaporative loss was, therefore, greater in hot-dry than in hot-wet conditions.

The ovaries from 251 cattle with known histories were dissected, and this work was linked with clinical and histopathological studies. In almost 20% of the cattle, resorption of corpora albicantia appeared to have taken place, beginning usually, after the fourth pregnancy. In 10% of cattle more corpora albicantia were found than corresponded with the normal pregnancies. Most such cases appeared to be associated with unrecognized ‘temporary pregnancies’, but normal pregnancy associated with two corpora lutea, as in the camel, may occur, though rarely. A scheme with correction factors, for allocating random samples to age categories, has been prepared. In 110 cattle, or 44%, miniature as well as full-sized corpora albicantia were recovered. Evidence from their histories is brought forward that the miniature corpora correspond to ‘temporary pregnancies’ of perhaps 2–5 months duration. This is cross-checked and confirmed, both from the histories of 112 cows yielding no miniature corpora, and also by correlation with the histopathological findings from the genitalia.

The soil nitrate content has been determined at fortnightly intervals on bare fallow plots and on plots under crops and natural vegetation in the forest and savannah regions of Ghana. Nitrifiable nitrogen, ammonium and soil moisture contents have also been determined. It has been found that the changes in nitrate content are related to changes in the content of nitrifiable nitrogen. During the dry season, a partial sterilization of the soil occurs and consequently the content of nitrifiable nitrogen rises. This nitrifiable nitrogen is slowly converted to nitrate in the dry season and rapidly converted once the rains commence. Nitrate is then lost from the soil by leaching and denitrification. Under bare fallow conditions leaching is the most important cause of nitrate loss, but it is probable that denitrification makes some contribution on cropped soils and those under permanent vegetation. There is no indication of microbial nitrate absorption under a crop. This is presumably due to the rapidity with which nitrate is lost by leaching and denitrification, and to the greater quantity of organic matter required in these free-draining tropical soils than in most temperate ones to produce an equivalent absorption of nitrate. The high levels of nitrate and nitrifiable nitrogen which are found under natural forest probably represent an equilibrium level typical of a cycle in which nitrogen fixation and nitrification as well as nitrate losses proceed very rapidly. Natural savannah grassland suppresses nitrogen mineralization in the field almost entirely, but the nitrifiable nitrogen content is at times high, in spite of the very high carbon/nitrogen ratio of the soil of over 20. This confirms the view that little nitrate absorption takes place in spite of the presence of what might be considered excess carbonaceous material. The suppression of mineralization under grass is considered due to an excretion of the plant roots which is toxic to the nitrification process. The failure of organic matter to build up in these savannah soils, although mineralization is suppressed, is most probably associated with their low general fertility.

In many animal production experiments, carcass weight is used as the sole criterion for the effectiveness of the treatments and of the nutritional status of the animals involved. In these experiments some knowledge of the carcass components would be desirable in order to assess any effects on the various tissues. Determination of these components has hitherto been costly and time consuming. Accordingly, these disadvantages have lead to a search for simple indices of carcass composition which can be readily applied even in relatively large-scale experiments. Until recently, however, no research worker has specified a relationship between carcass weight and carcass composition which would justify the use of carcass weight alone. There are, of course, many indications which suggest that such a relationship would exist, at least, for the main tissues of the carcass.

1. The effect of different levels of protein on the digestibility of the carbohydrate fraction of two compounded diets which differed widely in their contents of indigestible organic matter has been determined.

2. Digestibility of the available carbohydrate (the sugars, dextrins and starches expressed as starch) apparently increased with increase in the protein content of the diet.

3. Alteration in the cereal portion of the diet involves an adjustment in the amount of protein supplement if the nutritive ratio is to remain unaltered.

Though there has been a considerable amount of recent research on the early weaning of calves, few scientific papers have been published. Preliminary studies at the Rowett Institute have indicated that early weaned calves show greater thriftiness and increased liveweight gains when small quantities of antibiotics are included in the diet (Preston, 1955). Pilot trials carried out at Cockle Park in 1955/6 suggested that there is little difference between the performance of abruptly and gradually weaned calves (Quayle, 1956a). This present study has been carried out to verify these observations, and includes some comments on nutritional scouring.

1. The efficiency of food utilization for egg production by pullets has been determined for two diets, one high in energy and the other low.

2. Both groups laid at the same rate (245 eggs/bird) throughout the year.

3. Birds fed the low-energy diet ate more food, but the intakes of digestible protein, non-protein digestible energy and metabolizable energy were the same for both groups.

4. The cost of food perton was higher for the high-energy diet; per bird per year it was the same for both groups.

1. Good quality cod-liver oil, produced by modern methods and containing anti-oxidants, is a highly satisfactory ingredient of the diet of young chicks whether fed fresh or stored as an ingredient of mixed mash for from 2½ to 3½ months before use at the recommended rate of 1 pint/cwt.

2. Chicks so fed had slightly better food conversion ratios and a better appearance, and slightly lower liver vitamin A levels, than those birds receiving a comparable amount of vitamin A in powdered form.

3. Chicks so fed had better food conversion ratios and appearance, a higher liveweight gain, and slightly higher liver vitamin A reserves than those receiving a powdered vitamin preparation at the recommended rate of use of 0·05 lb./cwt.

4. It may be concluded that both this form of codliver oil and the powdered preparation are reliable sources of vitamin A as such.

5. Chicks hatched in early December grew better and maintained their vitamin A reserves for longer than comparable chicks hatched in early March.

1. Fresh, good quality cod-liver oil, containing an antioxidant, was incorporated at varying levels of up to 5% in the rations of pigs throughout the whole period from weaning (at 56 days) to bacon weight (at 196 days), without any evidence of detrimental effect.

2. Cod-liver oil did not at any level produce discoloration of the body fat, fishiness or other taint, or any other adverse effect upon carcass quality as judged subjectively and by routine measurements. Increasing levels of cod-liver oil increased the iodine number of the body fat, but this was not accompanied by any visual softening.

3. Although the experiment was not designed to assess the effect of high levels of cod-liver oil upon productive efficiency, it was, nevertheless, found that improvement in food conversion accompanied increases in the amount of cod-liver oil fed.

The results of an interim examination of the experiments at Rothamsted and Woburn on the effects of nitrogen, phosphate and potash on a six-course rotation of crops are reported.

It has become apparent that the main aim of the experiments, to relate the effects of the fertilizers to weather conditions, is not being fully realized. This is in part a consequence of the design, which has inherently low accuracy and results in low responses to phosphate and potash. In addition, faulty randomization and, at Woburn, fertility irregularities and pest damage have further reduced the accuracy attained.

The faulty randomization also seriously affects the estimates of experimental error given by deviations from smoothed response curves. Alternative estimates of error are provided to overcome this difficulty.

The mean yields and mean standard responses over the period 1931–55 are presented.

There is very little year-by-year variation in the responses to phosphate, but the responses to nitrogen and, for some crops, the responses to potash show sufficient variation to justify further analysis. As a first step the regressions of the responses to nitrogen on winter rainfall and on rainfall during the growing season and, for the root crops only, the regressions on sowing or planting date are briefly considered.