A small flock of 16 Blackface ewes occupying 40 acres of hill ground grazed as a fairly tight community. From observations over a complete year, 1960, it has been shown that sheltering behaviour was largely dependent on wind speed exceeding 24 m.p.h. Sheltering increased markedly at temperatures below freezing. Temperature above freezing, except for rapid falls in temperature exceeding 4° F., exerted little effect on sheltering. No relationship could be found between sheltering behaviour of the sheep and other factors which included rain, relative humidity, wind direction or season of the year.

It would appear therefore that the sensitivity of sheep to exposure is influenced more by wind speed than any other climatic factor.

1. Seventy-two individually fed, virus pneumonia-free Large White weaners were used to determine the effect of supplementing diets containing either some animal protein or only vegetable protein with either 0·1% CuSO4.5H2O or 2½% E.C. Feed (molasses distillers dried solubles).

2. The marked growth-promoting effect of supplementing a diet containing animal protein with Cu was again confirmed. The response when Cu was added to the all-vegetable diet was significantly less than that on the diet containing some animal protein, the significant improvement in growth rate on the two types of diet being respectively 5·1% and 14·5%.

3. The addition of 2½% E.C. Feed to the diet containing some animal protein significantly increased growth rate by 5·1%. This response was significantly less than that obtained from Cu supplementation. The 3·6% increase in mean growth rate when E.C. Feed was added to the all-vegetable diet was not statistically significant.

4. Whereas Cu improved the efficiency of food utilisation of the pigs, particularly when added to the diet containing animal protein (a significant improvement of 5·2%), E.C. Feed did not on either type of diet. Both Cu and E.C. Feed similarly increased the rate of food consumption of the pigs on both types of diet.

5. There were no differences in the performance of the control pigs given either the unsupplemented diets with animal protein or the corresponding all-vegetable diets.

A pilot experiment is described to observe the effect of a constant environment (temperature 65° F., relative humidity, 60%, artificial light for 12 hours daily alternating with 12 hours darkness, and constant diet) on the subsequent reproductive performance of fowls maintained under these conditions from hatching to the end of the 3rd annual cycle of egg laying.

The elimination of normal seasonal moulting of the plumage both at the beginning and at the end of the pullet laying year gave an advantage of 57 eggs for experimental birds over a group of sisters maintained under a more normal system of intensive husbandry.

This advantage in eggs laid was much reduced in succeeding years owing to a persistent and continuing decrease in rate of lay of hens in the constant environment.

All eggs were incubated and, although no differences in fertility, dead germs and hatchability were observed over the first full year of production in the birds in contrasting environments, the deleterious effects of a constant environment became increasingly apparent with age.

It is suggested that control of the environment induces a premature senility in the domestic fowl.

1. Four roughages were given ad lib. to each of eight steers. The amount consumed and the apparent digestibility of the energy of each roughage were determined together with the weight gains of the steers.

2. The mean voluntary intake of dry matter was related to the mean apparent digestibility of the energy of the roughages in the same quantitative way for the steers as had been noted with sheep. Mean weight gains were proportional to the mean number of calories of energy apparently digested.

3. Significant differences between individuals occurred in their voluntary food intakes, and those animals which consumed most digested it least efficiently. The variation in intake from individual to individual expressed as a standard deviation was ±7·5% of the mean.

4. The quantitative similarity of sheep and cattle as far as the relationship between their voluntary consumption of food of different apparent digestibility is concerned, is contrasted with their dissimilarity with respect to fasting metabolism. It is suggested that sheep are likely to prove more efficient convertors of the energy of roughages to body gain than are cattle.

Further work is clearly necessary to explore the extent of these differences.

This paper describes the estimation of genetic changes in farm livestock using field data. The method proposed depends on a difference in rate of change in performance of the population and of the successive progenies of individual sires. The change in the population with time is taken as t+g, where t represents environmental change and g represents genetic change, while the within-sire change is taken as t+½g. Their difference measures half the genetic change.

This principle can be applied, with certain precautions, tofielddata where there is some spread of sires over time. The method has two advantages over other methods in that past as well as current changes can be measured and no additional facilities are required. However, selection among sires may bias the estimates of genetic change. Approximate sampling errors of the estimates of change can be obtained and hence the rate of genetic change which a certain body of data will demonstrate to be significant can be estimated.

The method was applied to a set of pig records collected over nine years by a private pig breeder. There was considerable change with time in all six traits examined and in at least three of them there appeared to have been a substantial genetic change accounting for the whole of the observed change.

Counts were made before and after fixation of the numbers of fertilised and unfertilised ova recovered from 3 mated sows, 7 unmated sows and from 34 sows inseminated at varying times before and after the onset of heat.

The percentages of fertilised ova for sows inseminated the day before heat (day — 1) on the first day of heat (day 0) the second day of heat (day 1) and the third day of heat (day 2) are respectively for unfixed and fixed ova: 7·1 and 9·8, day – 1 ; 55·9 and 68·8, day 0; 63·4 and 98·2, day 1; 20·1 and 15·2, day 2. No fertilised ova were recorded from unmated sows; the percentages for mated sows were 94·3 and 95·5.

It is concluded that failure of fertilisation is likely to be the greatest source of loss of fertility in inseminations made before heat and late in heat.

Most ova from sows inseminated on day — 1 and from sows inseminated in day 2 had no spermatozoa on the zona pellucida. A few ova from sows inseminated on day 2 had very large numbers of spermatozoa present.

It is suggested that failure of the spermatozoa to reach the site of fertilisation rather than their loss of fertilising capacity is likely to be the cause of the low fertility of early inseminations.

In 1,347 parentage cases in cattle it was determined whether conception resulted from the first or second service. Among cows served twice within short intervals (1–11 days) about 20% remained pregnant from the previous service. At an interval of one day this proportion amounted to 37%.

About three-quarters of the cows had service intervals of 18–24 days. In most of these the calving took place between the expected dates according to the two services. In 6% of the cases with intervals of 18–24 days pregnancy resulted from the first service. It was estimated that about 1% of all cows mated twice within these intervals had become pregnant from the first service.

Rules are suggested for when blood grouping should be required for registration of pedigrees in the herd book.

Results of an experiment involving a total of 24 individually-fed pigs, covering the growing period between about 40 and 210 lb. live-weight, indicated that the addition of 20 g./ton griseofulvin to the diet had a slight depressing effect on the rate of growth of the pigs. It had no significant effect on the efficiency of food utilisation, but caused a small reduction in daily food consumption.

1. A comparison of the performance of Scottish Blackface ewe hoggets with and without an exteriorised flow to the duodenum was carried out while the animals were fed on hay with a low nitrogen content and added salt. No evidence was found from the food and water consumed, from the weight changes or from a comparison of the organic matter, nitrogen and ash contents of the food and the faeces that the operation caused any permanent disturbance to digestion.

2. Regular measurements of the flow of abomasal contents to the duodenum established a pattern of flow that was influenced by feeding. A relationship between the quantities passed per hour from the abomasum and the time devoted to rumination was found, but the relationship appeared to be dissociated in time so that increased rumination preceded the increased passage of contents.

3. The mean quantity of abomasal contents passed from four animals was 398 ml./hour. According to the quantities of chromium sesquioxide administered by mouth, passed from the abomasum, and excreted in the faeces this value represents not more than 90% and not less than 86% of the flow that can normally be expected.

4. The quantities of organic matter that disappear in the stomach were calculated and represent about half or more of the total disappearance in the alimentary tract.

5. Substantially more nitrogen left the abomasum than was eaten in the food daily. Of the nitrogen passing to the duodenum the greater part disappeared in the intestines.

6. About twice as much ash left the stomach as was present in the food and about two-thirds of the ash entering the duodenum disappeared in the intestines.

The effects of sex, twinning and age of ewe on birth weight, weaning weight and fertility have been studied in 5 years' records of a small grassland flock of Wiltshire × Blackface crossbred ewes with the object of providing provisional correction factors for these variables in recorded flocks under similar management. All these variables produced large effects in the flock studied. On birth weight these were; sex, 0·6 lb.; twinning, 2·1 lb.; hogg's lamb, 2·3 lb. The corresponding adjustments for weaning weight were 7 lb., 14 lb., and 11 lb. Ewes first bred as hoggs subsequently performed well.

Since the year 1900 the number of Border Leicesters has been fairly stable, between 3,000 and 5,000 females being registered each year. The number of flocks, however, has shown a fairly steady increase from 200 to over 600. There has been a decline in the number of ewes registered per flock from 16 to about 6 to 8. The important flocks would seem to number 15 to 20; only a few flocks persist for any appreciable length of time. Generation intervals are short, being only about 2 years on the sire side and 3½ years on the female side.

As with other breeds, relatively few rams have an importance out of proportion to their numbers—14 rams and 2 ewes with direct coefficients of relationship greater than 5% were found. Inbreeding per generation was only 0·32%, and there was no evidence of strain effects.

Long continued administration of a substance (dienoestrol diacetate) having oestrogenic properties as a dietary additive to chickens from hatching over a period of 4½ years resulted in:—

(1) an early, transient, hindrance to sexual development in both males and females,

(2) a wide range of individual variation in response to the drug, shown i n the degree of feminisation of the plumage in males, and certain characteristics associated with egg laying in the females,

(3) shell defects and related early embryonic deaths which could be attributed to an interference by the drug with development and differentiation of the oviduct.

The birds were maintained throughout the experiment under two contrasting environments ‘natural’ and ‘constant’. In the former group two birds developed tumours (one a typical adenocarcinoma) while four of the ‘constant’ birds had adenocarcinomata on examination post-mortem. The incidence of the condition was much lower than that encountered in a previous experiment and suggested that the oestrogen employed was not of itself a carcinogenic agent.

The primary function of the ovary was apparently unaffected and egg production to normal expected levels in both environments was attained.

The disproportionally high number of hens dying with inspissated yolk i n the oviduct and/or free yolk in the abdomen emphasises the possible effect of oestrogen on oviduct development and activity.

The danger of increasing the ‘load’ of oestrogens to susceptible individuals destined for breeding stock (and not short term administration of oestrogens for growth and ‘finishing’ of birds for slaughter) is referred to, and also its wider application were natural and synthetic oestrogenic substances in the diet to exceed a non-effective level.

Reciprocal matings between large, improved Swedish Landrace and small, primitive South African Native pigs produced strong evidence of a maternal effect at birth. However, compared with purebred Landrace piglets, the crossbred offspring out of large dams weighed less; conversely, compared with purebred Native piglets, the crossbred offspring out of small dams were heavier at birth. Differences between the various mean weights were all statistically significant.

At weaning (eight weeks of age), the weights of crossbred pigs out of large Landrace sows equalled those of purebred Landrace pigs. Crossbred pigs out of Native-pig sows occupied an intermediate position between the above-mentioned and purebred Native pigs. The differences between the latter group means remained significant statistically.

1. The influence of seasonal, maternal and genetic variation on body weight and fleece characters of Welsh Mountain sheep is reported.

2. Fertility and rearing ability of ewes improved from first to third lamb crop.

3. Male lambs were on average 0·4 lb. heavier at birth than females. Birth weight increased with number of pregnancies of the dam.

4. Early growth of the lamb between birth and marking (24 days old) used partly as a measure of milk production of the ewe, was greater in males than in females. Lambs born to older ewes made the greatest gains over this period, although the trend was not significant.

5. Weaning weight of the lamb was affected by the dam's weight at tupping, the number of preceeding pregnancies, her milk yield and also by the season in which the lamb was born. Despite these effects weaning weight proved a good guide to the weight (at subsequent matings) at 1½ and 2½ years old.

Heritability by intra-sire parent-offspring regression was 0·51±0·07 (P<0·001) and repeatability was 0·43 (P<0·001).

6. Fleece weight was not affected by season or age of ewe. However, the heaviest lambs at weaning tended to have heaviest fleeces the following year.

Heritability by intra-sire daughter-dam comparison was 0·58±0·11 (P<0·001) and repeatability was 0·46 (P<0·001).

7. Staple length measured on the mid-side of the animal had a repeatability between years of 0·56 (P<0·001) while heritability by daughter-dam regression was 0·38±0·ll (P<0·001).

8. Fourteen Welsh Mountain rams were progeny tested. Nine of the rams were purchased at local sales and 5 were home bred. They were not selected for the traits examined.

No statistically significant differences were obtained between sire progeny groups for weaning weight and fleece weight.

Wool growth on tattoo patches and mitotic activity in follicle bulbs were studied in a sheep on low and high levels of nutrient intake. The rate of wool growth on the high intake was 156% greater than that on the low intake while the rate of cell production from the follicle bulbs was 56% greater. The remainder of the increase in rate of fibre output was attributed to an increase of about 64 % in the volume of the individual cells of the fibres.

Complete chemical analyses of all body components of 20 Large White pigs were carried out. At the average live-weight of 90·3 kg. (empty body weight 86·5 kg.) the total protein content was found to be 12·7 kg. and that of the chemical fat 25·4 kg. The edible parts of the carcass (i.e. lean and separable fat) contained only 58·5% (range 55·2–61·3) of the total protein but as much as 85% of the total chemical fat. Simple and multiple correlations were computed between various carcass characters and protein, chemical fat and energy content. The results indicate that it may be possible to obtain fairly accurate estimates of the chemical composition and energy content of the edible parts of the carcass, of the whole carcass, and of the empty body by methods based on various systems of assessing the carcass quality.

Estimates of heritabilities and genetic correlations among 35 measurements and scores of British Large White bacon pigs are reported. The data came from pigs tested at the five National Progeny Testing Stations during the period autumn 1957 to spring 1959, and comprised full records on 1936 pigs from 200 sires. Independent analyses were carried out for each sex, and adjustments were made to the data for differences among stations, six-monthly periods and weight at slaughter.

Genetic parameters were estimated from sire components of variation and covariation obtained by conventional heirarchical analyses of variance and covariance. Estimates of the heritabilities and their standard errors are given in Table 2, and of genetic and phenotypic correlations in Table 3. These estimates, which agree in general with other estimates in the literature,, indicate that a large part of the variation and covariation is of genetic origin and that carcass traits, growth rate and food conversion efficiency are amenable to change by selection. Moreover, no serious antagonisms were found to exist with regard to improvement by selection.

An attempt has been made to summarise the correlation matrix pattern among 24 of the more important traits by using a principal component analysis. The first two principal components account for a disproportionate fraction of the correlation pattern especially of the genetic correlation matrix. Two principal components are given for each trait; the first may be associated with measurements of fat depth.

Results are presented of an investigation involving 328 pigs on 7 farms in East Anglia, on the effect of oxytetracycline (10 g./ton), oleandomycin (2·5 g./ton) and oxytetracycline (10 g./ton) plus oleandomycin (2·5 g./ton), on the live-weight gain, feed consumption and feed conversion efficiency of pigs from weaning to slaughter at approximately 260 lb. live-weight. Effects on number of days from weaning to slaughter and carcass characteristics are also given.

Both antibiotics gave significant improvements in daily live-weight gain (5·4% for OTC and 4·0% for OM) and feed conversion efficiency (3·9% for OTC and 2·3% for OM). There was a significant negative interaction between the antibiotics on live-weight gain from weaning to slaughter.

The average number of days from weaning to slaughter was significantly reduced by both antibiotics (5·8 days for OTC and 5·4 days for OM) and there was a significant interaction between antibiotics.

Feed conversion efficiency for all pigs was significantly better on those farms where antibiotics had not previously been used but the antibiotic treatment effects were the same in both categories of farm studied.

1. The stability with which dairy cattle develop in body size up to 2 years of age was studied in 60 pairs of uniformly treated identical twins, i.e. an assessment was made of the influence of season, genotype, mean size of twin pair, age and degree of maturity on the level of within-pair variability.

2. The frequency distributions of size differences shown by one-egg twins were in many cases decidedly leptokurtic.

3. The similarity in size of the identical twins studied was only slightly, if at all, influenced by season. Within-pair variability under free outdoor grazing was certainly not any greater than under semi-controlled conditions indoors.

4. The stability with which cattle grew appeared to depend on their genotype. Identical twins of the Shorthorn breed were somewhat more alike in size than were the twins of other breed-types; crossbreds were, on average, 50 % less stable than purebreds in average size () ; although crossbreds grew with somewhat greater stability ().

5. Whatever their mean size, all pairs of identical twins of the same breed appeared to grow postnatally with more or less equal stability (). Small, slow growing pairs showed a greater disparity in average size ().

6. Stability of development continually changed with age but not violently. Each body measurement appeared to have its own characteristic age trend. It is false to believe that variation automatically increases with increasing age. As they grew older, identical twins tended to become less alike in their later maturing body measurements whereas their early maturing body measurements tended to decline in variability. There was an overall trend with degree of maturity; variability steadily increased to a maximum and subsequently declined.

7. It is suggested that environmentally induced instability of development may remain at a minimum level so long as growth curves are not seriously distorted from their exponential path to maturity.