1. The characters of the semen of twenty-one bulls were compared with their fertility as expressed by the service rate—the number of services required for each conception.

2. It was found that, on the basis of the density of the semen, the total number of spermatozoa ejaculated, the motility and change in pH of the semen on incubation at 37° C, the animals could be divided into a higher fertility group with service rates from slightly more than 1·0 to about 3·5, and a lower fertility group with service rates from above 3·5 to ∞. Totally sterile animals could be detected.

3. It is suggested that other factors than the quality of the semen can vary fertility so as to give service rates at different levels from 1·0 to about 3·5. Below a certain level of semen quality fertility appears to be impaired no matter what other factors operate.

4. No relationship could be detected between the percentage of abnormal spermatozoa ejaculated and the service rate.

5. Standards for use in diagnosis of fertility are suggested.

1. The fertility records of two groups of bulls, one group used for controlled service, and one group used for free service, were compared over a period of one year.

2. The fertility of the free-service group was consistently better except during the months of December, January, February and March.

3. The difference in fertility between the two groups was correlated with the varying length of the oestral periods of the cows at different seasons of the year.

4. It is suggested that the higher fertility in the free-service group was due to a closer relationship of service to the end of heat and thus to ovulation.

Carrots of Chantenay type wefe grown in cultures of a black fen soil shown by analysis to be deficient in phosphate but normal as regards potash. When phosphate was absent, the cotyledons, and sometimes the whole of the foliage, were dark bronze in colour. There was a statistically significant increase in yield following applications of phosphate, but a tendency for applied nitrogen and potash to diminish yield.

We thank F. Shaw, Esq., N.D.H., of the Cambs. C.C. Staff for Agricultural Education, for his assistance in obtaining the fen soil used in this experiment.

The fatty acid composition of the back fats of pigs whose basic diets were buttermilk or skim milk have been determined by ester-fractionation, and the results are compared with those of previous workers. Pigs whose diets were supplemented with copra contained up to 13 mol. % of myristic acid, with smaller amounts of lauric acid.

Experimental evidence supports the view that dietary linoleic acid is assimilated to a greater extent by slow-growing than by fast-growing pigs. Dietary lauric and myristic acids, however, appear in greater proportions in the depots of fast-growing, as compared with slow-growing pigs.

The di-, and polyethenoid C18 acids of the fat of unsupplemented milk-fed pigs appeared not to contain appreciable amounts of linoleic acid.

Consideration of the composition of pig depot fats from the point of view of Callow's growth-rate theory (Callow, 1935a,b), shows that the theory appears to explain the iodine values of fats both of groups of animals and of depots of an individual pig. When, however, the fatty acid compositions of the fats are considered, the theory is untenable in respect of the depots of an individual pig. Differences in unsaturation between outer back fat, inner back fat, and perinephric fat are essentially determined by differences in the ratio of oleic acid to stearic acid, differences in linoleic acid content being inconsiderable.

It can equally be shown that the growth-rate theory does not explain the results obtained by Hilditch & Pedelty (1941) for depot fats of sheep. Differences between different depots both of the pig and of the sheep seem to be characteristic of the species and cannot readily be altered by altering either the quantity or the quality of the diet.

From time to time during the course of the present war, pig feeders have reported that they have experienced considerable difficulty when making use of extracted palm-kernel meal as a major constituent of the rations of bacon pigs. This has been attributed partly to the lack of palatability of the extracted meal, which leads to a reduction in food consumption and a consequent depression in the rate of live weight increase, and partly to its high fibre content, which causes the ration to be somewhat bulky and of lowered digestibility and nutritive value. The present experiments were designed to throw light on these somewhat contentious matters, since little guidance is to be obtained from the scanty references to this subject in the scientific literature dealing with animal nutrition.

1. Data are presented for the chemical and botanical compositions of ryegrass seed and various by-products of the ryegrass seed cleaning industry.

2. Digestibility data are presented for a more limited range of samples of ryegrass seed, ryegrass seed cleanings and, for comparative purposes, of certain by-products of the milling of oats.

3. Ground high quality perennial ryegrass seed has a chemical composition and digestibility comparable with that of oats.

4. Ground rough (i.e. uncleaned) perennial ryegrass seed has a chemical composition and digestibility such that its starch equivalent is 90–95 % of that of oats.

5. Ground bulked ryegrass seed cleanings has a starch equivalent of about four-fifths that of oats and is comparable in feeding value with better grades of oat feed, i.e. those containing not more than about 20 % of fibre.