(1) Two trials on the effect of copper glycine injections on the live-weight gains of suckling beef calves under commercial conditions are described.

(2) One injection supplying 120 mg. of copper increased live-weight gains by approximately 10% during the suckling and grazing period. A second injection given two months after the first gave a further positive but not statistically significant response.

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.

The design and manufacture of plastic cannulae are described and the chief hazards associated with cannulated re-entrant fistulae in sheep are discussed.

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.

1. Thirty-two individually-fed pigs were used to determine the effects of soaking their daily meal ration in either water or in liquid skim milk and water for approximately 24 hr. before feeding. The experimental period continued from about 10 weeks of age to bacon weight.

2. Neither soaking procedure had any significant effect on the rate of growth, efficiency of food utilisation, dressing percentage, carcass length, backfat thickness or commercial grading results of the pigs.

3. The growth rate and efficiency of food utilisation of the pigs given meal plus skim milk were significantly better than for those given the all meal diet. The dressing percentage of the former was also significantly higher than the latter, but there were no significant differences between the two groups in carcass length or backfat thickness.

4. Possible reasons for the difference in performance of the all meal and meal plus skim milk-fed pigs are discussed.

Two experiments are described to investigate the effect of different weights of pigs at 56 days of age on live-weight gain, efficiency of feed utilisation and bacon carcass quality.

1. In Experiment I a comparison was made between 32 pairs of weaners, reared on the sow, which weighed 31·0 1b. and 45·4 1b. respectively at 56 days of age. After separation into heavy and light groups the pigs were group fed to bacon weight.

The heavy weaners reached 200 1b. eighteen days earlier than the light weaners but this difference was due completely to the slower rate of growth to 50 1b. live-weight. The heavy weaners required 3·59 1b. of meal per 1b. live-weight gain from 56 days of age to bacon weight compared with 3·50 1b. for the light weaners but there was no difference in efficiency of feed utilisation during the period taken to grow from 50 to 200 1b. There were no significant differences between the carcasses apart from an increased flare weight in the light weaners.

2. In the second experiment both suckled and early-weaned pigs were reared to 30, 40 and 50 1b. at 56 days of age and then fed individually to 200 1b.

The number of days taken to reach 200 1b. was 168·6 for the 50 1b. pigs, 176·6 for the 40 1b. pigs and 182·1 for the 30 1b. pigs; there were no differences due to the methods of rearing. The efficiency of feed utilisation from 56 days to 200 1b. was not affected by method of rearing but as weight increased from 30 to 50 1b. at 56 days, the meal required for a pound of subsequent live-weight gain increased from 3·06 to 3·24 1b.

The number of days to increase from 50 to 200 1b. live-weight was 110·4 for the 50 1b. pigs, 109·3 for the 40 1b. and 106·3 for the 30 1b. pigs, again there being no differences due to the methods of rearing. There were no differences in efficiency of feed utilisation from 50 to 200 1b.

Neither weight at 56 days nor method of rearing markedly affected the quality of the carcass but there was an indication that 56-day weight caused greater differences in the early-weaned treatments than in the suckled treatments.

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.

1. Analyses of records of eight-week body weight in broiler chickens have been carried out to estimate the effect of management level (measured by mean body weight of all varieties on each farm) on the components of variance due to differences between and within varieties, and to find out if there is any evidence of genotype-environment interaction.

2. It was found that as management improved, the between-variety genetic variance remained constant or possibly increased whilst the withinvariety (genetic and environmental) variance decreased markedly. The cause of these regressions is not known.

3. In four cases out of six there were significant genotype-environment interactions. In two cases, the genetic correlation between the performance of varieties on different locations was significantly different from 1·0.

4. It is suggested that on the basis of these findings it would be necessary to select between varieties on records taken from chickens maintained under conditions similar to those in which they will eventually be used. However, fewer chickens would be required to measure, with a predetermined level of accuracy, mean differences on well managed farms than on poorly managed ones.

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. Carcass measurement and dissection data from 250 pigs reared at the stations of the National Pig Progeny Testing Board have been analysed to study the value of the carcass measurements in predicting the percentage lean in the carcass.

2. Differences between sexes in the carcass characteristics were generally larger than those between breeds. Gilts had a higher percentage of lean meat than the hogs, with larger eye muscle dimensions and smaller measurements of backfat thickness.

3. For pigs of the same breed and sex, the best predictions of leanness possible without cutting the carcass were derived from measurements of shoulder and minimum loin backfat (see Figure 1). Mid-backfat measurements improved the accuracy of prediction, but length and depth of carcass did not. The residual standard error in percentage lean at constant shoulder and minimum loin backfat was 2·66% of side weight overall but this was reduced to 2·28% by adjustments for breed and sex.

4. Measurements made after cutting the carcass at the last rib gave more accurate predictions of percentage lean than did the split carcass measurements. The residual standard error in percentage lean at constant B, C and K (see Figure 2) was 1·97 % of side weight overall, reduced to 1·88 % by adjustments for breed and sex.

5. The implications of these relationships in carcass grading and carcass evaluation generally are discussed.

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.

An analysis has been made of milk production data from indigenous East African zebu cattle at the Baraton, Maseno and Sangalo Livestock Improvement Centres in Kenya, covering a period of twenty-five to thirty years.

The relationships between milk production and length of lactation, dry period, calving interval, month of calving and age were examined. Lactation length accounted for from 53% to 66% of the total variance in milk yield. Variations in length of dry period caused significant differences in milk yield between, but not within cows. Increasing length of previous calving interval improved current lactation milk yield but month of calving had no significant effect. Yield increased from first to second lactation by 8% after which it remained relatively constant up to the fifth lactation. Age at first calving was positively correlated with first lactation milk yield.

Intra-herd repeatabilities were 0·55 for milk yield, 0·38 for lactation length, 0·17 for calving interval and 0·12 for dry period. The highest estimates of heritability were those obtained for lactation yield and length (0·5); the lowest, for calving interval, was close to zero. All heritability estimates had high standard errors. The probable genetic improvement in milk production achieved by the selection practised in the herds was estimated as ranging from zero to 0·15% of the average yield per year.

1. Using the data from the dissection of 24 sides of beef from Hereford, Dairy Shorthorn and Friesian steers on four levels of nutrition a critical study has been made of the relation of the weight of tissue in an anatomical joint to the total weight of the same tissue in the whole side.

2. There was a significant eifect of breed and level of nutrition in the case of bone. The heaviest breed (Friesians) had a bigger proportion of bone in those bones which support the animal (i.e. the radius-ulna, humerus, femur and tibia-fibula) than had the lighter breeds (Herefords and Shorthorns). The effect of level of nutrition was not the same for all the bones and was difficult to interpret. There was little or no significant effect of breed or level of nutrition on the distribution of muscular or fatty tissue among the joints.

3. The relation of the weight (in kg.) of a tissue (x) in a joint to that in the whole side (y) was expressed by groups of equations of the form, y = a+bx, there being a separate group for bone, muscular tissue, subcutaneous fatty tissue, intermuscular fatty tissue and total fatty tissue. Tables are provided giving the values for the constants ‘a’ and ‘b’ and standard errors of prediction joint by joint for each tissue.

4. No general significance could be attached to the values for the constant ‘a’ but for each tissue there was a correlation between the value for ‘b’ and the inverse of the average weight of tissue in the corresponding joint. For each tissue there were one or two joints which were significantly aberrant. Aberrance is associated either with exceptionally high or with exceptionally low levels of errors of prediction.

5. The high order of magnitude for the standard errors of prediction for estimating muscular tissue (± 12·2 1b. or more) and for estimating total fatty tissue (± 12·7 1b. for the loin), led to exploring the following rule of thumb method.

6. The weight of muscular tissue in a carcass is approximately one-third of the live-weight of the animal, the weight of bone, tendon etc. is onequarter of the weight of muscular tissue and the remainder of the weight of a carcass is the weight of fatty tissue.

7. Using the weights of the animals on the farm, the weight of the sides after hanging in the slaughter house overnight, and the weights of the tissue after dissection it was shown that the above method of estimation gave values for muscular tissue within ± 10·1 1b., for fatty tissue ± 11·8 1b. and for bone etc. ± 3·1. These values compare favourably with those calculated from the weight of muscular tissue in a joint (±12·2 1b. for the foreshin), and fatty tissue (neglecting thorax ±7·0 1b. and 13th rib ±9·8 1b.) ± 12·7 1b. for the loin. The estimate of bone etc. from the weight of radiusulna (± 1·7 1b.) was somewhat better.

8. The general conclusion is that in studies of meat quality, and of the effect of breed and plane of nutrition on meat quality (including carcass conformation) it will be necessary to dissect the whole side or carcass joint by joint, tissue by tissue and muscle by muscle. There are no adequate short cuts.

A genetic study of the grading-up of the East African zebu to the Indian Sahiwal has been undertaken on records, covering about 25 years, from three Livestock Improvement Centres in Kenya. It appears from this study that the indigenous East African zebu cow has only about half the genetic potential of the Indian Sahiwal for milk production, and the scheme of gradingup has resulted in substantial and worthwhile increases in milk production.

This report is an attempt to interpret evidence concerning geneticenvironmental interaction as it relates to the effectiveness of selection.

Methods of estimating genetic-environmental interaction were investigated with the conclusion that the standard analysis of variance is a satisfactory tool provided (1) the interaction component of variance is adjusted for important variation between environments in the scale of genetic effects and (2) the variance component for the average effects of genetic groups is recognised as equivalent to the average covariance of the same genetic group in different environments (i.e. ) to include the real possibility of negative genetic correlation.

It is shown that (1) response to selection for improved average performance over varying environments (ΔGt) is proportional to the genetic correlation between expressions of the same genotype in different environments (rG), that (2) gain in ΔGi, from measuring performance in k environments is proportional to if k times as many animals are tested, but to if total numbers per genotypic class (nk) are held constant, where g2 is heritability of individual variation within environments and rG is the correlation between the phenotypic expressions of the same genotype in different environments.

Evidence is presented that (1) variations among poultry-farm environments in California cause important, but largely unpredictable, shifts in ranking of genetic stocks for egg production, and (2) improved accuracy in measuring genetic differences in average performance across environments probably justifies utilising a sample of 5 to 10 farms representing the range of environments for which the stock is bred.

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.

The influence of maternal and genetic factors on the size of lambs at birth and on their gestation length has been studied from the results of two experiments involving the transfer of fertilised eggs from one breed of sheep to another. In the first experiment, eggs were transferred reciprocally between old ewes of the large Lincoln breed and of the small Welsh Mountain breed. Results are based on 20 transfer lambs and 14 normally born singles. In the second experiment, 35 pure Lincoln and 28 pure Welsh lambs were born as a result of transferring eggs into 18-month-old nulliparous Scottish Blackface sheep.

The breed type of the lamb was found to be the most important factor influencing weight and cannon length at birth, although maternal-foetal interactions were present. As the maternal environment became poorer, genotypic differences remained distinct but decreased in magnitude. The maternal environment provided by 4th parity Lincoln ewes, if judged by lamb's size at birth, was better than that provided by 4th parity Welsh ewes, and this in turn was better than that provided by 1st parity Blackfaces. Lincoln and Welsh lambs in the same maternal environment differed in average birth weight by 5·7, 3·8 and 3·0 1b. respectively in the Lincoln, Welsh and 1st parity Blackface maternal environments. Lincoln and Welsh lambs, each in their own normal maternal environment, differed by 6·5 lb. The maternal influence on cannon length was similar but small. Gestation length of Lincoln lambs in Welsh recipients was almost 4 days shorter than that of Welsh lambs in Lincoln recipients. In the Blackface maternal environment, Lincoln and Welsh lambs differed little in gestation length but males were, on average, carried about a day longer than were females.

At the individual level, weight of (Blackface) recipient ewe had a somewhat greater effect on lamb's size than had weight of (Lincoln or Welsh) donor ewe. The magnitudes of these ‘genetic’ and ‘maternal’ effects were comparable with those found at the level of group means; even so, donor's and recipient's weight together accounted for only a small part of the individual variation in lamb's size about the group means.

It was concluded that a ewe was able to respond to progressively greater demands made by a lamb or lambs of progressively larger (combined) potential size—but in accordance with the law of diminishing returns—and that the upper limit of maternal accommodation must be considerable. By contrast, the upper limit of mean genetic size at birth appears to be not far above the mean size of single lambs born to their natural mothers in good condition. A model has been constructed from which mean birth weight of lambs can be predicted.