An attempt has been made to analyse the lactation yield into its two components, maximum yield and persistency; the latter has been defined as the ratio of lactation to maximum yield, and has been measured by a S.F. calculated from , where R is the mean ratio for the month of calving concerned.

Whilst, when corrections for external factors are applied, maximum and persistence are equally constant throughout the cow's life, these factors cause wider individual fluctuations with persistency; maximum yield is subject to a more rigid limit and may be largely determined by the area of the mammary gland, but persistency seems to be chiefly a nutritional factor—that is to say, it depends on the success of the mammary gland in competing with the other tissues of the body for the available nutriment. This leads to the view that persistency is higher in the dairy type of cow; it also appears to be associated with high constitution, for very definite positive selection is apparent with persistency, as compared to marked negative selection for maximum—this is attributed to pathological attrition falling more heavily on cows with high initial yield and low persistency.

The results of these experiments are, on the whole, disappointing, since they have failed to reveal a reliable treatment for parasitic gastritis of sheep other than that caused by H. contortus, but they do confirm the experiments of other workers in that there are several drugs available which are more or less effective against this worm. Of these perhaps copper sulphate would seem to be in many ways the best for general use, since it is cheap and safe, and can be easily given either dry in capsules or in solution. Better results are obtained when two doses are given, and probably the interval of 7 days between the doses could, with advantage, be shortened to one or two days. The addition of sodium arsenite did not, in these experiments, increase the efficacy of the copper sulphate.

Carbon tetrachloride, given in 12 c.c. doses would seem to be effective against Haemonchus. In such doses it is rather expensive, and although in these experiments toxic symptoms were not observed, deaths from smaller doses have been recorded by others.

Tetrachlorethylene (Nema) given in capsules containing 5 c.c. gave, in most cases, good results against Haemonchus, and except in Sheep 10 reduced the egg count very considerably. It did, however, cause considerable constipation, and in a few instances post-mortem examination revealed some inflammation of the small intestine. The administration of a laxative with or shortly after the Nema therefore appears to be indicated.

(1) The maintenance requirement of Light Sussex cockerels has been found by a feeding trial and comparative slaughter method. The maintenance requirement found was 22.1 calories per sq. m. of surface per hour. The net energy of the ration fed (Sussex ground oats: whole dried milk = 13 : 3) was 1.8 calories per gm.

(2) A new method of determining the surface area of birds is described.

(3) The value of K in the equation area = K has been found by this method to be 9.3.

It has been shown that in this trial the increase in milk yield of the nine cows considered as a herd is within the limits normally expected in the case of thrice-daily milking.

The increase in the case of the heifers is below expectation, and the probable reasons for this are indicated.

The effect of three 8-hour intervals on butter-fat percentage has been studied, and it is shown that as far as the individual cows are concerned there is little difference between the number of low fats produced under thrice milking at equal intervals and twice milking at unequal intervals in the case of the herds specified. It is shown that the reason for the bulk milk of the thrice-milked cattle maintaining a high standard of fat percentage at each milking is that each individual cow maintains a fairly high level consistently at one specific milking, and that this is not the same milking for each cow.

(1) Previous work suggests that there are two types or degrees of foetal atrophy. In one case, so far only reported in rats, the atrophy extends to all members of a litter and produces complete sterility. This has been shown to be connected with a pathological condition of the uterine tissues brought about by the absence of vitamin E.

Even when vitamin E is in optimum supply, however, there remains a certain amount of foetal degeneration ranging from 7 to 14 per cent, which must arise from causes other than vitamin E starvation.

In the second case a partial degree of foetal atrophy has been widely observed by different workers to occur in many different classes of mammals. Average figures for this type quoted for the pig vary from about 2 to about 20 per cent, and the residual degeneration just referred to in the rat appears to be of this nature. The present investigation was carried out to determine the effect on this second type of a deficiency in the diet of protein and of calcium. Evidence is submitted to support the conclusions which follow.

(2) Partial foetal atrophy in sows is not due to a deficiency of protein in the ration.

(3) Calcium deficiency is not the major factor in producing this type of foetal atrophy though it may be a contributory cause.

In England, the corn-growing situation, after a span of precarious years, has now become critical. Even if prices rise substantially and fairly soon, what may be described as essentially the “English cereal yield problem” will remain.