Thirty six individually-fed pigs were used in a within-litter comparison of the 6 treatments of a 3 × 2 factorial experiment. The pigs were about 9 weeks old at the start and were slaughtered as their individual weights reached about 200 lb.

Three types of basal diet were given with and without a supplement of CuSO4.5H2O included at 0·1% (250 p.p.m. added Cu).The diets were based on (1) barley and fish meal, with 17% crude protein for pigs up to 103 lb. live-weight and 15·4 % from then on, (2) maize and soya (extracted soya bean meal), with about the same levels of protein and (3) maize and soya, but with only 13·4% crude protein for pigs up to 103 lb. and 11·9% for pigs of 103 lb. to 200 lb. Daily feed allowances were determined from a fixed scale based on live-weight.

Pigs given the high-protein maize-soya diets grew more rapidly, required less feed per lb. gain and had fatter carcasses than those given the barley-fish meal diets. This was probably because of the higher TDN content of the maize-soya mixture.

Pigs given the low-protein maize-soya diets grew less rapidly, required more feed per lb. gain and had fatter carcasses with smaller ‘eye’ muscles than those receiving the high-protein maize-soya diets, these being the usual effects of an inadequate supply of total protein or of an essential amino acid.

CuSO4.5H2O4 added as 0·1% of each of the three types of diet improved growth rate before 103 lb. live-weight but had no consistent effect on feed conversion efficiency. Between 103 lb. and slaughter the copper sulphate did not affect performance on the barley-fish meal or high-protein maize-soya diet, but in the low-protein maize-soya diet it reduced feed conversion efficiency and rate of gain by 5%. Although this interaction was not statistically significant it agrees with an observation made in Florida and warrants further investigation.

1. A feeding trial was conducted on 64 individually-fed pigs given diets varying in crude protein content, and containing as a protein supplement either white-fish meal or groundnut meal alone, or groundnut meal with L-lysine monohydrochloride or DL-methionine or both.

2. Daily live-weight gain and feed conversion ratio of pigs given diets containing fish meal were best when the diet provided 18% crude protein on an air-dry basis (15·7% white-fish meal).

3. Additions of L-lysine monohydrochloride to a diet providing 18% crude protein and containing 21% groundnut meal as the main source of protein produced highly significant (P<0·001) improvements in daily gain and feed conversion ratio and these measures were not significantly different from those of pigs given the control (fish meal) diet which provided similar total lysine and crude protein levels. The white-fish meal diet containing 18% crude protein produced pigs whose half carcasses were of higher specific gravity (P<0·05) and rib cuts with more protein and less fat (each P<0·05) than did the groundnut meal diet at the same protein level.

4. DL-methionine did not significantly affect live-weight gain, feed conversion, fat or protein content of the rib cut or the specific gravity of the half carcass.

5. Pigs on a 12% crude protein diet containing groundnut meal supplemented with lysine grew at the same rate as pigs on an 18% crude protein diet in which no lysine supplement was added to the groundnut meal. Their rib cuts contained more protein and less fat.

Forty-eight individually-fed Large White pigs, initially 10 weeks of age, were used to test the effects of growth checks induced by severe restriction of feed intake. The checks were imposed at 50 lb. or 100 lb. live-weight and lasted for 5 weeks, during which live-weight gains averaged only 1·6 lb. and 4·1 lb. per pig, respectively. The daily feed allowances of the unchecked controls and of other pigs while not on check were according to a fixed scale based on live-weight. All pigs were slaughtered as their individual weights reached 200 lb. and a number of measurements were made on the carcasses.

Excluding the period of the check, efficiency of feed conversion and rate of gain were better for pigs checked at 50 lb. than for the controls. The difference in age at a given weight caused by the check was narrowed by about 6 days at the end of the experiment. Indications of a similar compensation in growth of pigs checked at 100 lb. were mostly explained by the rapid growth of these pigs before 100 lb. and by the sudden increase i n their weight at the end of the check period which was probably due to increased gut fill.

A check at 50 lb. or 100 lb. did not affect either the specific gravity of the carcass, which was taken as an indication of the overall proportion of lean to fat, the area of ‘eye’ muscle, the depth of backfat over the shoulder, the thickness of streak or the Danish ‘slight of lean’ measurement, but the check at 50 lb. increased the thickness of fat at position (1) over the ‘eye’ muscle. Both checks increased the minimum thickness of back fat in females but not in castrates and reduced the average rump fat in castrates but not in females. It was concluded that the checks did not affect carcass composition although they probably caused changes in the distribution of the backfat.

Milk yields of three strains of Scottish Blackface ewes (Lewis, Lanark and Newton Stewart) were recorded over periods of eight weeks on reseeded pasture and on hill pasture. There were no differences in milk yields between strains in the respective environments, but there were significant differences between environments in all three strains.

Relationships between udder width and milk yield were investigated in the Lewis and Newton Stewart strains.

Analyses of milk samples (taken by hand) showed there were no significant differences in the contents of fat or solids-not-fat. There was evidence that the percentage of fat and solids-not-fat in all groups tended to decrease initially and then to increase gradually as lactation advanced.

Live-weights of the ewes were compared and it was shown that the Lewis ewes were characteristically lighter than either of the other strains.

On the reseed all lambs were approximately equal in live-weight and condition. On the hill the Lewis lambs were inferior in weight and condition, and it is suggested this reflected the Lewis strain ewes' grazing preferences for higher ground.

1. The mean daily live-weight gains of lambs from the 1956–59 flock records were used to estimate the milk yield of ewes during the first six weeks of lactation.

2. The yield was affected by the number of lambs suckled but not by the number born. Ewes rearing twins on the hill gave a higher yield than those rearing singles (145%–155%). Good grazing raised the yield to twice that of ewes rearing singles on the hill.

3. In 3 out of the 4 years the utilised yield was remarkably constant in the case of ewes rearing single lambs, but ewes rearing twins on the hill were more variable. Ewes rearing twins on low ground did not show any significant seasonal differences.

4. From an experiment on 36 ewes it was confirmed that twin-rearing ewes produce more milk than single-rearing ewes in all environments. There was no difference between ewes rearing one lamb whether born as a single or as a twin. Leaving two lambs on the ewe for a few days to establish a high level of milk yield did not benefit the remaining lamb after its twin was removed.

Four trials were carried out to determine the effect of feeding a supplement to stirks 6–9 months of age when turned out to grass. In two trials there was no response and in two there was a response to supplementary feeding.

No response was obtained in five trials when supplements were fed to store and fattening cattle. The feeding of undecorticated cotton cake did not have any apparent effect either on rate of live-weight gain or on scouring.

It is concluded that while the feeding of a supplement to young animals can bejustified when maximum live-weight gain is required, feeding of supplements to older cattle cannot be recommended so long as the animals are grazing good swards.

Results are given from two digestibility trials in which the following three diets were fed to sheep: (i) grass only, (ii) grass+5 oz. cotton cake daily, (iii) grass+10 oz. cotton cake daily.

In the first trial the average dry-matter content of the grass was low (approx. 14%), intake was low and the supplements were eaten in addition to the grass. In the second trial where the dry-matter content (approx. 20%) of the grass and the intake were higher, the cake supplements reduced herbage consumption.

The feeding of cake did not have any significant effect on the dry-matter percentage in the faeces but depressed the digestibility of the dry matter, crude protein, crude fibre and nitrogen-free extract in the diets including cake and reduced their starch equivalent and total digestible nutrient values.

No evidence was found to support the recommendation that undecorti-cated cotton cake should be fed to grazing animals.

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.

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.

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.

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.

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.

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.