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.

1. Twenty spring-born Friesian calves, housed indoors, were divided into two groups each of 10 calves. During their first three weeks all calves were fed alike on whole milk containing 3·5% butterfat. At three weeks of age calves in one group were changed to a diet consisting of reconstituted buttermilk powder which was made up to the same energy content as the milk. Up to the 30th day intake was gradually increased to 20% of body weight; thereafter till slaughter of the calves at approximately 200 1b. live-weight both groups were fed to appetite twice daily.

2. Calves in both groups grew well and differences between groups in growth rate, and age at slaughter, food consumption and food conversion, were all statistically non-significant.

Twenty-two triplet or small twin lambs were reared in two ways. One group received cow's milk and the other a synthetic milk designed to approximate in composition to ewe's milk.

The group fed synthetic milk made significantly better live-weight gains to weaning. This difference was not maintained after weaning. Possible reasons for this are discussed.

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.

1. The results of four experiments on the effects of oral and implanted hydroxyzine on lambs are reported.

2. The effect of hydroxyzine on daily rate of live-weight gain ranged from +7·8% to −6·2% improvement with a mean value of +2·3%.

3. Lambs receiving hydroxyzine in the creep feed manifested significantly higher killing-out percentages and lower thyroid weights than the controls. Pituitary weights were not affected by hydroxyzine.

4. In an experiment on individually-penned, weaned wethers, given a high energy diet, hydroxyzine by either route did not affect live-weight gain but significantly increased killing-out percentage, rate of gain of carcass weight and fat deposition in certain tissues. Hydroxyzine did not affect the fresh weights of the pituitary, thyroid and adrenal glands or the weights of the teats.

Two 2 × 4 factorial experiments each involved 8 litters of 8 pigs, one pig from each litter being allocated to each treatment. Diets containing supplements of a commercial grade of copper sulphate were compared with others containing Analar (Experiment 1) or micro-analytical reagent grade copper sulphate (Experiment 2). Four levels of each of two grades of CuSO4.5H2O, providing 16, 62, 125 or 250 p.p.m. Cu in the diets, were given in each experiment.

The pigs were put on experiment at 8—9 weeks of age and most were slaughtered as their individual weights reached about 200 lb. The exceptions were 4 litters in Experiment 1 which were taken off experiment at that weight but not slaughtered. The pigs were fed in individual compartments, meal allowances being determined from a fixed scale based on live-weight.

Purity of copper sulphate did not affect growth rate, feed conversion efficiency or carcass measurements in either experiment.

Response to level of copper sulphate between about 45 and 100 lb. liveweight differed somewhat between experiments. In Experiment 1 pigs receiving 125 or 250 p.p.m. in the diet grew 4 or 9% faster and had better feed conversion efficiencies than those receiving 16 or 62 p.p.m. Cu. In Experiment 2, pigs receiving 62, 125 or 250 p.p.m. Cu all grew about 4–5% faster and had 1–5 % better feed conversion efficiencies than those receiving 16 p.p.m. Cu, but the effect on feed conversion efficiency was not statistically significant.

Increase in copper sulphate above the trace level supplying 16 p.p.m. Cu in the diet had no effect on growth rate or feed conversion efficiency between 100 and 202 lb. live-weight or on killing-out percentage or carcass measurements.

Comparison of the results with those from a previous experiment showed that in pigs fed according to a fixed scale the greatest consistent increases in growth rate and feed conversion efficiency have occurred with copper sulphate as 0·1% of the diet, giving 250 p.p.m. Cu. This supplement has only improved performance between 100 and 200 lb. live-weight in one experiment out of five.

1. Nine groups of 4 litter-mate Wessex Saddleback gilts were divided on a within-litter basis between 4 treatments so that they were reared from 8 weeks of age to 200 1b. live-weight according to different levels of total feed intake; (a) a high level rising to 8·0 1b. meal per day at 200 1b. live-weight, (b) a medium level approximately 80% of the high, (c) a low level approximately 60% of the high and (d) changing from the low to the medium level between 14 and 16 weeks of age. From 200 1b. live-weight to mating at first heat after reaching 300 1b. all were fed to the medium scale (6·5 1b. meal per day), and all were treated alike during each of 3 pregnancies and lactations.

2. Mean rate of growth from weaning to 100 1b. and from 100 to 200 1b. differed significantly between treatments (P<0·001), and mean efficiency of feed conversion of the low-plane group was significantly poorer than that of the high-plane group (P<0·05) from weaning to 100 1b. live-weight.

3. All gilts, regardless of treatment, reached puberty at approximately the same age (25 weeks), with the result that mean weight at puberty differed markedly between treatments (P<0·001); 116, 154, 189 and 147 1b. for treatments (a) to (d) respectively.

4. Gilts reared on medium and high planes of feeding exhibited oestrus less strongly than those reared on the low-plane, with the result that mean weight at successful mating was significantly greater in these two groups (P<0·05).

5. Four gilts in the low-plane group and one in the high-plane group failed to conceive after repeated matings, but numbers were insufficient to indicate the significance of this.

6. From the original 36 gilts, 27 first litters, 26 second litters and 25 third litters were produced and reared to 8 weeks of age. There was no significant difference between treatment groups in litter size at birth, mean weight of piglets at 3 or 8 weeks of age or total litter weight at weaning.

7. Trouble from temporary collapse of the legs was experienced in all but one gilt of the high-plane group between 6½ and 7½ months of age.

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. Nitrogen balance studies were made on eight early weaned calves given diets varying in crude protein content from 11·6% to 22·6% in dry matter.

2. Nitrogen retention increased significantly as the level of crude protein increased to 19·20%; there was no further increase in nitrogen retention when the level of protein was increased to 22·6%.

3. Dry matter digestibility and apparent digestibility of dietary nitrogen rose progressively as the level of crude protein increased.

4. The nitrogen retention of calves fed diets adequate in protein was calculated to be 2·88 g. per 100 g. gain in body weight.

1. Nitrogen balance studies were conducted on 6 early-weaned calves fed three diets containing respectively commercial groundnut meal, heattreated groundnut meal and fish meal as the major protein sources.

2. Nitrogen retention and live-weight gain differed significantly between diets, being highest on the fish meal diet and least on the commercial groundnut diet.

3. Blood urea concentration was significantly lower on the fish meal diet than on either of the groundnut diets but differences between the groundnuts were not significant.

4. Differences between diets in nitrogen utilisation were due almost entirely to differential urinary nitrogen losses.

In the herd of Nganda cattle at the Government Livestock Experiment Station, Entebbe, Uganda, it was found that of the known environmental factors affecting milk production, the more important ones were age (in lactations) and length of the calving interval preceding the second and third lactations. The correlations between performance in different lactations of the same animal were high for lactation milk yield (0·73) and average daily milk yield (0·62) and low for calving interval (0·21) and dry period (0·15). The repeatability of lactation length was intermediate (0·42). The heritability values were around 0·3 for the weight measurements, around 0·2 for yield characteristics and around 0·1 for length of lactation and age at first calving.

The sires used in the breeding programme at Entebbe made little impact on production performance in the herd. The estimated genetic improvement in milk yield through selection of dams of cows was also low. It is argued from comparison with results from other parts of the tropics that superior genotypes for milk production are difficult to come by among indigenous cattle in these areas and that we should therefore look for other opportunities and methods to move ahead faster in the future.

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.

1. Two groups of Friesian calves, one group of 10 reared on whole milk and the other group of 9 changed gradually from whole milk at 21 days of age to a full diet of reconstituted buttermilk powder at 29 days of age, were slaughtered at a live-weight of approximately 203 1b. Data obtained at slaughter showed a highly significantly heavier weight of omental fat from the calves of the whole milk group, and a significant difference in the weight of the unemptied intestinal tract in favour of the buttermilk group.

2. One side of each carcass was dissected by anatomical joints into the primary tissues; bone, muscle, fat, and tendon and waste. The absolute proportional weight of the dissectible fatty tissues and the weight of kidney and channel (pelvic) fat were statistically highly significantly heavier in the carcass sides of the calves reared on whole milk. The percentage of muscular tissue in the sides of the buttermilk reared calves was significantly higher than for the sides in the other group.

3. The chemical composition of the dissected muscular tissue revealed highly significant differences in fat (ether extract) and a significant difference in water percentage in favour of the carcass sides of the calves reared on whole milk.

4. The chemical composition of the dissected fatty tissue showed statistically highly significant differences in favour of the calves reared on whole milk for the items: water weight and percentage, fat weight and percentage, protein weight, and ash weight. The buttermilk group had in their dissectible fatty tissue a highly significantly greater proportion of water and protein.

5. The dissectible components of the individual joints showed: significantly heavier weight of fatty tissue from the leg, loin, pelvis, 9–10–11 rib cut, thorax, and shoulder of the left sides of the calves reared on whole milk. The weights of the dissectible muscular tissue of the loin and the rib cut were significantly heavier for the buttermilk-reared calves.

6. Cutting-out data on a limited number of sides showed no consistent differences between groups.

7. The meat trade did not differentiate against the buttermilk-fed calves despite their lower fat content. The high muscular tissue content at 65–68% makes veal a very desirable product.

The transferrins in Swedish cattle were studied with the starch gel method. A continuous tris buffer system was used. With sera from young calves each transferrin allele appeared to determine four fractions. Among some animals from Norway two seemed to have a transferrin type not earlier described for the European cattle breeds. The frequencies of the transferrin alleles found in a bull sample from the Swedish Red-and-White breed were TfA = 0·53, TfD = 0·18 and TfE = 0·29. Family data were in good agreement with the theory of inheritance. The transferrin types were used in parentage testing and a formula is given for the possibility of making exclusions. The value of the transferrin types in diagnosis of zygosity in cattle twins is shown. The transferrins seem to occur in bovine milk also.

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.

1. A series of experiments with adult sheep were carried out in an attempt to place on a quantitative basis the generalisation that the voluntary food intake of ruminants increases with the quality of the fodder they are given.

2. Methods of determining voluntary intake free of subjective bias were developed. It was shown that voluntary intake varied with a fractional power of body weight close to 0·734. The length of time necessary to establish stable intakes was 12–15 days and the number of times fresh food was offered each day had no apparent effect on intake.

3. It was found that voluntary intake of long fodders was related to the apparent digestibility of their energy, increasing rapidly as digestibility increased from 38% to 70% and thereafter more slowly.

4. The giving of concentrated food resulted in a drop in the voluntary intake of fodder. With high quality hay 100 g. concentrates replaced 100 g. hay. With poor quality hay, 100 g. concentrates replaced 47 g. of hay.

5. The passage of three widely different hays through the gut was measured and the poorest passed most slowly. Calculations showed that the dry matter content of gut contents was the same for all three materials irrespective of their quality.

6. It was shown that an increase in digestibility of 10 units in the range 40–60% resulted in considerable increases in the total amount of energy apparently digested and in equivalent increases in daily gain.

7. The digested energy consumed/day/kg. W0·734 (E) can be related to voluntary intake (I) g./day/kg. W0·734 by the equation:—

E=4·(I—31)

which provides a rapid and easy method of assessing fodder quality under conditions of ad libitum supply.

8. The results are discussed and it is shown that under ad libitum feeding conditions an increase in the nutritive value of unit feed from 50 to 55, i.e. by 10%, increases body gain by 100%.

1. Three groups, each comprising four Hereford-cross and four Friesian half-sib male calves, were fed milk substitute and offered grass cut from autumn pastures. Two of the groups received meal supplements of similar energy value but differing in protein content. The third group received no meal supplement.

2. As the consumption of meal rose the intake of herbage dry matter decreased but total dry matter intake increased.

3. The effects of the two meals on the progress of the calves were similar but not apparent until after the first 6 weeks. The lack of response to the high protein content of one meal suggests that energy may be the limiting factor to growth of calves reared on autumn pasture.

4. Hereford-cross calves which did not receive a meal supplement tended to make the best live-weight gains during the subsequent grazing season, but no such recovery was made by the Friesians.

Forty-eight sows were inseminated into the uterus with semen (sperm fraction) diluted to 20 ml. with an egg-yolk glucose phosphate (YPG) diluent to contain 10·0 × 109, 1·0 × 109 and 0·1 × 109 spermatozoa. In 24 sows (120 ml. group) insemination of the 20 ml. diluted semen was followed by the intra-uterine insemination of 100 ml. YPG diluent, alone. The success of insemination was judged at autopsy from ova recovered 2-4 days after insemination (Experiment A) or from counts of foetuses present 25 days after insemination (Experiments B and C). In Experiment A the numbers of ‘cleaved’ ova were recorded before fixation: the numbers of ova judged to be ‘fertilised’ were counted in preparations of fixed and stained ova. For 24 sows inseminated with 20 ml. semen alone at the three dosage levels (10·0 × 109, 1·0 × 109 and 0·1 × 109 spermatozoa) the percentages of ‘cleaved’ and ‘fertilised’ ova were 78·5 and 80·9; 83·5 and 81·2; 24·6 and 19·8. For sows inseminated with the same sperm numbers in 20 ml. semen followed by 100 ml. diluent, the percentages were 41·5 and 43·9; 44·2 and 36·2; 24·6 and 6·7. Comparison of numbers of sows with some ova cleaved (or ‘fertilised’) and sows with none cleaved (or ‘fertilised’) showed no significant differences in sow fertility between treatments.

Comparison of numbers of sows with all ova cleaved (or ‘fertilised’) and sows with none cleaved (or ‘fertilised’) shows that inseminations with the 20 ml. volume, alone, were of significantly higher fertility than those inseminated with 120 ml.

Estimates of fertility based on the examination of unfixed ova differed in 9 sows from estimates based on the examination of fixed and stained ova. In one sow some uncleaved ova were shown to be pronucleate after fixation and staining. Morphologically abnormal ova were identified in 6 sows; most of these abnormal ova showed multinucleate blastomeres. These abnormal ova were found only in sows inseminated with not more than 1·0 × 109 spermatozoa.

Counts of the numbers of spermatozoa on fixed ova showed that these tended to decline as the number of spermatozoa inseminated declined. Comparing sows inseminated with the same number of spermatozoa there tended to be fewer spermatozoa on ova from sows inseminated with 120 ml. than on ova from sows inseminated with 20 ml.

Of 13 sows in Experiment B inseminated with 20 ml. semen containing 10·0 × 109 spermatozoa, 9 had foetuses present at autopsy 25 days later (11·6 foetuses per sow).

Of 17 sows in Experiment C inseminated with 20 ml. semen containing 1·0 × 109 spermatozoa, 7 had foetuses present at autopsy 25 days later (7·1 foetuses per sow).

The difference in pregnancy rate for the two groups is not statistically significant.

Differences in litter size between the two groups of sows are explainable by differences in ovulation rate between the two groups (group B, 18·2 corpora lutea per sow, group C, 13·4 corpora lutea per sow).

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.