1. Four fitter-mates from 20 litters on each of 3 farms were divided equally and distributed at random between two treatment groups. Each piglet was injected intramuscularly with 2 c.c. of an iron preparation between 1 and 2 days of age. The control group received an iron-dextran complex which provided 150 mg. of iron per piglet and a second group received an irondextrin complex which provided 200 mg. of iron per piglet.

2. The body weight and the level of haemoglobin in the blood of each piglet were measured at 1, 8, 15, 22, and 56 days of age and the incidence and cause of disease and mortality were recorded.

3. The level of haemoglobin in the blood of both groups was comparable throughout the experiment.

4. At the 22nd and 56th day, the group receiving 200 mg. of iron was approximately 6% heavier than the group receiving 150 mg. of iron. These differences were highly significant at the 0·1% level.

5. From each of 3 additional litters, 3 piglets received no supplementary iron while 5 piglets received 200 mg. of iron provided by the iron-dextrin complex. The three whole litters were slaughtered on days 3, 8, and 22 respectively. The mean level of iron per 100 g. of liver and spleen within the untreated group on the above occasions was 5·8, 5·8, and 3·7 mg. respectively, compared with 72·9, 55·1, and 17·6 mg. respectively within the treated piglets. The differences were highly significant at 0·1 % level.

There were no differences in toughness, juiciness, intensity of flavour and incidence of taints between samples of meat from wether lambs and cattle which had been treated with oestrogens and similar meat samples from untreated controls.

During feeding trials prior to slaughter both the cattle and sheep which had been given oestrogens gained in live-weight significantly faster than their respective controls.

A report is given on a progeny testing scheme for bacon pigs which operated at Wye College from 1953 to 1957. Boars were brought to the unit, mated to a random selection of sows and 20 progeny (4 pigs from each of 5 litters) were individually fattened under standard conditions. Growth, feed efficiency and carcass measurements were recorded. The data were examined by analysis of variance. Significant differences in most characters were shown between sows, between boars and between tests. There was a progressive improvement in growth performance but not in carcass measurements from the earlier to the later tests. This was attributed in the main to improved management.

Differences within litters were small for carcass length but large for backfat measurements. Significant differences between boars could be detected but this was limited by small numbers of boars within tests and the high variability of some characters. The growth performance and carcass characteristics of female pigs were significantly better than for castrated males. Estimates of heritability were fairly high for most characters.

Disease incidence declined in the later tests. In earlier tests congestion of lungs associated with virus pneumonia was associated with a slight reduction in speed of growth and feed efficiency.

The results are discussed with particular reference to their contribution to the evaluation and utilisation of progeny testing on a national basis.

1. Two experiments each with 3 dry cows, 3 heifers and 3 calves were carried out in 1959 and 1960 under uniform continuous grazing conditions on a ryegrass-white clover sward to measure individual feed intake by the chromic oxide-faecal nitrogen method.

2. Estimates of digestibility were high (70–82% in organic matter) and there was evidence that calves selected a diet of higher digestibility than cows.

3. Mean daily estimates of organic matter intake were for cows (1300 lb. live-weight) 23·5 lb., for heifers (790 lb. live-weight) 20·8 lb. and for calves (450 lb. live-weight) 14·3 lb. Corresponding digestible organic matter intakes were 17·4, 15·3 and 11·0 lb.

4. Relationships between digestible organic matter intake and liveweight were calculated and the merits of the exponents 0·62 and 0·73 of liveweight discussed.

5. The results were compared with accepted cow equivalent standards and, regardless of the exponent chosen, agreed with the system which adopts higher values for young grazing cattle.

1. Data from the first 3 litters of each of 21 Wessex Saddleback sows were analysed on within-Utter, between-litter/within-sow and between-litter/ between-sow bases.

2. There were highly significant differences between sows in the mean weight of their pigs at birth, 3 and 8 weeks of age; between litters of the same sow there were no significant differences at birth or 8 weeks but pigs in third litters were significantly lighter than those of the first and second Utters at 3 weeks of age. There was a significant increase in number born but not in number weaned from first to third litters.

3. Within litters, the variation in 3-week weight accounted for by variation in birth weight was 30% in first litters, 48% in second litters and 45% in third; respective relationships between birth weight and 8-week weight were 14, 27 and 26%. Between litters of the same sow, differences in mean birth weight accounted for 50 % of the difference which occurred in 3-week weight and for 26 % of the difference in 8-week weight. Differences in mean creep-feed consumption accounted for 18% and differences in mean 3-week weight for 44% of the differences which occurred in weight at weaning. Between litters of different sows, the variation in birth weight accounted for 48% of the variation in 3-week weight, and 8% of the variation in 8-week weight. Differences in creep-feed consumption accounted for 36% and differences in 3-week weight accounted for 26 % of the difference in weight at weaning.

4. Season of birth had some effect on weaning weight due in part to an effect on creep-feed consumption. There was a negative correlation between birth weight and mortality and a positive correlation between mortality and Utter size.

Results are presented on weight changes in sows which indicate (1) that checks to increases in weight at specific stages appear to be a normal function of pregnancy in sows, (2) that most of the weight gained during pregnancy in excess of that accounted for by the litter and placenta is lost before the next pregnancy, either during lactation or, if this is prevented, immediately after weaning, (3) that considerable weight loss occurs between weaning and re-mating on a level of feeding which is sufficient to allow a mean gain of 1 lb. per day during pregnancy, and (4) that sows given a relatively low level of total feed during lactation appear to lose considerably less weight between weaning and re-mating, and to gain weight more rapidly during the first few weeks of pregnancy, than those fed to a relatively high level during lactation. Practical implications of these results are considered.

The extent of the genetic differences existing among a sample of the dairy herds of New Zealand was assessed by a direct experimental approach. In part one of the experiment, 240 young calves were taken from 40 herds of markedly different production levels and reared and milked as a uniformly treated herd of cattle at Ruakura. In part two of the experiment 120 sets of identical twin calves were divided amongst these 40 high- and low-producing herds.

Results indicated that in general there were no obvious genetic differences between the cattle in the high and low herds in body size, fertility, milk production or days in lactation. There were, however, genetic differences between the high and low herds in milk composition; approximately 50% of the differences between herds in butterfat and protein content and 25% of the SNF content were due to genetic differences between herds.

Genetic differences between herds in yield were found within the high group of herds but not in the low.

Evidence was obtained indicating that interactions between herd environment and the genotype of individual animals provided an appreciable source of variation.

The production level of a herd in which an animal was reared was without effect upon its subsequent production potential for milk yield.

1. In the summer of 1958, 15 mg. of hexoestrol was administered to Blackface wether lambs in one of the following ways; 5 mg. before weaning followed by two 5 mg. tablets at weaning, three 5 mg. tablets at weaning, and thirdly a single 15 mg. tablet at weaning. In a further series of experiments in 1959 the effect of both raising the pre-weaning implantation to 10 mg., and the total hexoestrol dosage to 20 mg. was studied.

2. Suckled lambs implanted with 5 mg. of hexoestrol at the milk clip gained significantly more in live-weight (18%) up to weaning in 1958 than did untreated lambs; in 1959 the difference was only 11%.

3. Between weaning and the end of the trial all treatments with the exception of that in which hexoestrol dosage was raised to 20 mg. showed a very highly significant increase in live-weight gain over untreated lambs, the increases ranging from 26 % to 54%.

4. In neither year was the overall gain in live-weight from pre-weaning to the end of the trial significantly increased by implanting part of the hexoestrol dose prior to weaning.

5. Live-weight gain of the lambs was not significantly increased when three 5 mg. tablets of hexoestrol replaced a single 15 mg. tablet.

6. The implanting of lambs with 20 mg. hexoestrol failed to give a response superior to that obtained with 15 mg. hexoestrol.

7. Each group of lambs receiving hexoestrol treatment showed an increased average carcass weight.

The gestation lengths of cattle are considered in terms of variation due to the month in which calving occurs. The well-known summer decrease in gestation length is re-established but in addition there is a short-term decrease in April which appears to be related to the cattle being put out to grass at a late stage of pregnancy after they have been housed for the winter.

Blood grouping was used to investigate 1000 parentage cases in Swedish cattle. The blood samples were tested for 39 antigenic factors belonging to 9 different systems. One of the two possible bulls could be excluded as the sire in about 80% of the complete parentage cases in the Swedish Friesians (SLB) as well as the Swedish Red and White breed (SRB). The additional use of the transferrin systems in 79 of these cases resulted in a considerably increased efficiency. The probability of making exclusions with the aid of the various blood grouping systems was estimated from gene frequency data and showed good agreement with the results actually obtained. In the SRB the combined use of tests for cellular antigens and transferrins is expected to give solutions in about 84% of the complete paternity cases with two possible sires.

The value of using genotypic classifications in the complex blood group systems in parentage tests is discussed. Finally, attention is given to the difficulty encountered in parentage cases involving twin-born animals with erythrocyte admixture.

The results are given from trials which were designed to demonstrate the effects of feeding antibiotics and a tranquiliser to beef cattle. In Trial 1 the feeding of 80 mg. aureomycin daily produced no significant effect. In Trial 2 the feeding of neither 2·5 mg. hydroxyzine nor 80 mg. terramycin nor the two combined produced any significant effect except to depress the level of intake of dry-matter over the whole trial period. This reduction in drymatter intake did not lead to an increase in efficiency of conversion (lb. dry-matter intake per lb. live-weight gain). In trial 2 the tranquiliser tetrahydrozoline was unsuccessfully used at the beginning of the trial in an attempt to reduce the loss in live-weight suffered when the animals were tied up.

1. High and low dry-matter silages were fed to fattening bullocks on the self-feed system giving daily live-weight increases per head per day of 2·6 lb. and 1·7lb. respectively, over a feeding period of 10 weeks.

2. Chemical data on the composition of a low dry-matter silage and high dry-matter silage are presented.

3. Digestibility studies using sheep were carried out to obtain the starch equivalent values of the two types of silage. The starch equivalent of the high dry-matter silage was 12·4 while that of the low dry-matter silage was 9·9. This difference in starch equivalent explains the extra 0·9 lb. per head per day live-weight increase made by the bullocks on the high dry-matter silage.

4. Mineral balances were carried out. The results show that the low dry-matter silage would supply an inadequate amount of calcium for satisfactory production.

Observations on duration of the period of receptivity in two groups of Milking Criollo, one of Jersey and one of Brahman cows are presented. After one or two oestrus periods measured without service the cows were bred naturally in the case of Jerseys, Brahmans and one group of Milking Criollos. In the other group of Milking Criollos, artificial insemination was used. The period of receptivity was shortened after natural service by 8·7 hours in Milking Criollo and by 4·1 hours in Brahman cows. No shortening of oestrus occurred in the Jerseys and no significant shortening in artificially inseminated Milking Criollos.

Nine of the cows under observation (and seven other cows with some Zebu blood) allowed only one service by the bull.

The requirements of bacon and heavy pigs for lysine and methionine have been investigated. The trials employed 3rd and 4th cross Large-White × Essex pigs.

In the first trial, which involved 560 pigs during the 40 to 120 lb. growth stage, the amount of herring meal in the standard weaner diet was progressively reduced from 7 to 1%. Total protein was kept constant by including soyabean and groundnut meal.

Growth efficiency worsened progressively as herring meal was reduced but growth was restored by adding lysine and methionine to the levels of the 7% herring diet. The optimum levels of lysine for pigs during the 40 to 120 lb. growth stage appeared to be higher than reported elsewhere (0·85% against 0·76% and 0·65%).

Treatments prior to 120 lb. had no residual effects on growth during the 120 to 200 lb. stage when all pigs were on a normal fattening diet containing no animal protein and there were also no residual effects on the carcass composition of the pigs at 200 lb. live-weight.

The results support the view that the nutritional value of animal proteins to pigs lies solely in the quantity of essential amino acids that they supply. Under the conditions of this trial, the particular essential amino acids were lysine and methionine.

The second trial involved 260 individually and group-fed heavy pigs. Lysine supplementation of the barley-mineral diet during the 140 to 260 lb. growth stage improved food conversion and increased the lean content of the carcasses of heavy pigs fed ad lib.; with restricted feeding growth rate was also improved.

Under the conditions employed the optimum lysine content of heavy pig diet during the final growth stage is at least 0·67%.