1. The normal pattern of social behaviour in growing Large White and Berkshire pigs is described. The pigs were observed from 8 to 16 weeks of age in pens of 6 to 10 pigs. Large Whites were more aggressive than Berkshires.

2. Social rank was found to be positively correlated with initial weight.

3. Initial weight and social rank both influenced growth; the relative effect of rank compared with that of initial weight was greater in the second month than in the first.

4. The contribution of social rank to the total variance in growth over the 2-month period was estimated at about 13%.

5. It is suggested that the use of individual housing in pig progeny test schemes may not be desirable because of the absence of social environmental effects.

1. From a review of the literature it has been shown that there are two opposing views regarding the best method of interpreting growth data, which arise from conflicting opinions as to the role of fat deposition in the growth of the animal.

2. Data of McMeekan and Palsson and Verges have been re-analysed and their own results are compared with results obtained when the effects of variation in fat content are eliminated.

3. No evidence has been found of any effect of plane of nutrition on the total weights of bone and muscle relative to the weight of bone plus muscle together.

4. The weight of bone plus muscle in the head and neck was increased relative to the total weight of bone plus muscle during periods of restricted nutrition. Apart from this there was no clear evidence of a relationship between the order of maturity of the joints and their relative retardation of development.

5. Huxley's allometry equation was found appropriate for standardising the measurements, and the exponent was taken as a numerical expression of the relative maturity of each tissue or part.

1. Wool production and fleece structure were studied by fibre analysis in six groups of lambs subjected to different pre- and post-natal levels of nutrition. Samples were taken at 6, 12, 28 and 48 weeks of age.

2. Pre-natal limitation (twin pregnancy) reduced the number of secondary fibres present at birth but, providing post-natal nutrition was adequate, this difference had disappeared by 6 weeks. There were no permanent effects on fibre number, wool production or fleece structure.

3. Severe post-natal restriction of feed intake during the first few weeks of life had a marked effect on the development of the secondary fibre population, on wool production and on the birthcoat shedding cycle. The effects persisted beyond the period of nutritional limitation but had disappeared by 12 months of age.

4. The results are discussed in relation to the normal development of the adult Blackface fleece.

1. Thirty Suffolk × Half bred lambs were slaughtered at the following ages: two twin lambs at birth and two singles and two twins at 1, 2, 3, 4, 6, 8 and 16 weeks of age.

2. The following weights were recorded: live-weight immediately before slaughter; and carcass, head, skin, feet, alimentary tract, heart, liver, kidneys, lungs and trachea, and blood immediately afterwards.

3. The alimentary tract was emptied and weighed in four separate parts; reticulo-rumen, omasum-abomasum, small intestine, large intestine.

4. The volumes of the reticulo-rumen and the omasum-abomasum were measured by immersing in water and filling the organs with water to 2 cm. pressure.

5. The in vitro digestive efficiency of rumen liquor from lambs of 1, 2, 3 and 4 weeks of age was assessed.

6. Empty body weight was considered to be valuable in comparing animals of different ages or from different feeding regimes or at different times of the year because variations in gut ‘fill’ were eliminated.

7. There were no differences between singles and twins in the relationship of the fresh weights of the parts of the body to empty body weight, except that development of the liver and the blood was rather slower for singles.

8. Little evidence was found of a difference in rate of development of the alimentary tract between singles an d twins, although the log an d square root transformation suggested a possible difference in reticulo-rumen size in favour of twins, significant at the 5% level.

Results have been presented from a small scale investigation into operational and theoretical aspects of progeny testing Down rams as sires of crossbred fat lambs. Twenty-six Suffolk rams were evaluated from the growth records of 922 lambs out of Border Leicester × Cheviot ewes. In addition measurements were recorded on 260 carcasses. Significant differences were found between corrected progeny means, which were equivalent t o heritabilities of between 0·03 and 0·13 for live-weights up to 15 weeks, and o t higher values for skeletal measurements.

A scheme for the selection of Down rams was considered which involved measuring the individual performance of all ram lambs and then progeny testing the best of these by measuring a fixed total number of crossbred lambs. It was concluded that the proportion to be progeny tested could be varied within quite wide limits without seriously changing the genetic merit of the selected group.

1. The effects of gonadotrophins administered during the follicular phase of the oestrous cycle were studied in forty gilts; these were purebred Large White or Large White crosses weighing from 200-275 lb.

2. Superovulation was induced by a subcutaneous injection of PMS; half of the animals received in addition an intramuscular injection of LH.

3. All animals which received gonadotrophins exhibited normal oestrous behaviour and only four of the gilts failed to come into oestrus by Day 21 of the cycle.

4. A relationship has been established between the PMS dose and the mean ovarian response.

5. An injection of LH was not essential for ovulation after treatment with PMS. Similarly, it had no significant effect on ovarian response.

6. Egg recovery was 75% in the group of animals that exhibited fertility. Of these eggs, 93% were fertilised and undergoing cleavage.

1. The data relating to 16 multi-location trials involving several varieties of egg-laying chickens per trial have been analysed to obtain estimates of variety × location (genotype-environment) interactions for rearing and laying mortality, hen-month and hen-housed egg production and 32-week egg weight. Significant interactions were found in about a third of the trials for all five traits though in only two cases did the interaction variance account for more than 20% of the total variance.

2. Genetic correlations for varieties between locations have been calculated as 0·49 for rearing mortality, 0·50 for laying mortality, 0·72 for hen-month production, 0·76 for hen-housed production and 0·91 for egg weight. These are in close agreement with previous published estimates.

3. The between-and within-variety components of variance have been calculated for each trait on each location separately. The regressions within trials and pooled values of the components on the mean level of all varieties on the location have been calculated. For hen-month production the pooled regres-son of the within-variety component on mean was negative, whilst for all other traits the pooled regressions were positive. The pooled regressions of the between-variety components on mean were all positive. It is suggested that this information indicates that comparison of varieties for single traits should be carried out on locations favourable for maximum expression of the trait. The difficulties which variety comparisons, for several traits having different optimum management regimes, would cause and the need for a more intensive investigation of the conditions conducive to genotype-environment interactions are stressed.

Six serum transferrins have been found amongst 1,030 sheep in a Welsh Mountain sheep flock, apparently produced by six genes segregating as alleles at a single locus. All 21 possible phenotypes have been found.

The genes are designated TfA, TfB, Tfc, TfD, TfE and Tfp, TfA producing the fastest, and Tfp, the slowest migrating component. TfE and Tfp are at a much lower frequency (0·01 to 0·06) than the remaining genes (0·2 to 0·3) and Tfp may represent a fifteenth allele at this locus.

A comparison of observed phenotype frequencies with those expected under random mating, showed that a marked disturbance in segregation existed, with homozygous TfCC animals in consistent excess and a marked shortage of heterozygous TfBC and TfCD animals. Variation amongst remaining phenotypes appeared to be at random. However, incompatibility with the Tfc gene also extended to matings including Tfp. Examination of 282 matings confirmed that the effect of the Tfc gene favours maternal-foetal incompatibility as a cause of disturbed segregation, rather than selective fertilisation. However, reciprocal mating data were not available.

1. Six Suffolk rams (two purchased from each of three breeders) were each progeny tested on 10 Scottish Halfbred (Border Leicester ♂ × North Country Cheviot ♀), 10 Welsh and 10 Clun ewes. The progeny of the Clun ewes were reared at a different location from the progeny of the Halfbred and Welsh ewes.

2. Progeny were weighed at birth and every 3 or 4 weeks thereafter so that 56 and 112 day weights could be calculated. Growth rate was considered for the periods 0–8 weeks, 8–16 weeks and 0–16 weeks. The growth rates were corrected for birth type and sex, but not for birth weight. The growth rates of a ram's progeny for a ewe type were converted into a deviation from the mean of all progeny of that ewe type, and measured in standard deviation units. An overall deviation for all ewe types for each ram was also calculated; 0–16 weeks was considered the best period over which to compare ram progeny performance and the difference between the best and worst ram for this trait represented 0·81 of a standard deviation or a 10% increase in growth rate for the progeny of the best ram over the progeny of the worst ram. There was some evidence of ram × ewe-type interaction for this trait.

3. A number of progeny of each ram were sent to a central abattoir and dissected into commercial joints. All pieces were weighed and a total carcass value obtained by multiplying each joint weight by an average retail price per pound and summing. The total carcass value was converted to terms of yield in pence per pound. Subjective assessments were made for colour and texture of meat and for tenderness and flavour of cooked meat. There was little variation between ram progeny groups for any of the carcass traits.

1. An experiment was carried out with forty individually-fed Large White × Wessex pigs to examine the growth rates of females (gilts) and castrated males after varying periods of time on a restricted plane of nutrition.

2. Compensatory growth was made by pigs in all treatments when some restriction in the plane of nutrition had been previously imposed.

3. The immediate growth response after the restriction ceased was directly related to the duration of the period of restriction.

4. In pigs on a restricted scale of feeding to 80 lb. live-weight, no compensatory growth was observed until a later stage in growth, whereas pigs on a restricted scale for a much longer period to 160 lb. live-weight showed immediate and significant compensatory growth.

5. In the periods immediately after the food restriction was lifted, gilts responded more than castrated males on all treatments.

6. The effect on the overall growth rate from 45 to 200 lb. live-weight became progressively worse as the period of restriction was prolonged and in no case did the compensatory growth fully compensate for the setback suffered during restriction.

7. There were no significant differences in overall food conversion efficiency and it appears that pigs with an even rate of gain and an interrupted growth rate may be equally efficient.

8. There were no significant differences in carcass length or dressing-out percentage although a moderate degree of restriction up to 120 lb. live-weight improved grading results, these being related, to non-significant improvements i n food conversion and therefore possibly to a lower carcass fat content.

1. Three group feeding trials and two individual feeding experiments, involving a total of 202 pigs from 8 to 10 weeks of age to bacon weight, were conducted to determine the effect of processing (steaming, followed by rolling and grinding) of maize and barley on pig performance. The effect of supplementation of raw and processed cereal diets with two crude enzyme preparations was also studied.

2. Processing of maize or barley had no significant effects on rate of growth or efficiency of food utilisation in pigs fed on diets containing a proportion of bran and pollard, or of pigs fed on diets in which maize or barley constituted the entire cereal portion.

3. Neither enzyme preparation affected pig performance.

4. The growth rate and efficiency of food utilisation of pigs given diets high in maize were significantly better than for those given diets high in barley.

The teat preference system of sucking behaviour in young pigs has been described by Donald (1937), Braude (1948) and McBride (1963). Briefly, the piglets develop a preference for particular teats during the first few hours of life. Though they may change their teat, particularly during the first two days, they then drink from the same teat or teats until weaning. It is the aim of this note to record some information on this teat preference system collected on litters farrowed at the Queensland Agricultural College at Gatton.

In young pigs, it is common to find individuals which grow appreciably slower than their litter-mates. Such “runts” are an important cause of economic loss in the pig industry. Extreme examples are easily recognisable but an adequate definition of what constitutes a runt is more difficult. It is, however, possible to separate slow growing pigs from the remainder and compare them in a number of ways. During the course of a study involving routine observations on the behaviour and growth of piglets, data were obtained which made it possible to compare slow growing pigs with others. It is the aim of this study to tabulate these differences and to relate them to the weights of piglets at birth.

Animal Production, Volume 6, Part 1, p. 53

In Table 5, the identification numbers of twin pairs should read 3, 4, 1, 2 (and not 1, 2, 3, 4)