1. Because dressing percentage increases as body weight increases, an adjustment for body weight is necessary when the dressing percentages of animals of different body weights are being compared. Instead of comparing animals on this basis, it is suggested that the power function y = axb, relating carcass weight and body weight, when computed in the logarithmic form, provides a suitable method for making adjustments of this kind.

2. Using this function, differences in yield of carcass have been shown, between breeds and between seasons, in a study involving Hereford, Aberdeen Angus and Beef Shorthorn cattle.

3. A similar function has been used to describe the relationship between fat content of carcass and carcass weight and body weight, using data from the same breed study.

Relationships between the intake of energy and the rate of gain on the one hand, and the chemical composition of gain on the other were studied in bacon pigs, assuming that: (1) the only important determinants of the energy balance are the expenditures of energy in maintenance, in protein deposition and in fat deposition; (2) the net energy cost of fat or of protein deposition remains constant in pigs of all ages and live-weights, whatever the level of nutrition; (3) the average maintenance requirements of pigs growing over the same live-weight range and kept under similar conditions are constant, irrespective of their daily gains; (4) the ratio of non-fat components to protein in the gains of pigs over a similar live-weight range is virtually constant. Deductions based on these assumptions enabled the expression of the feed conversion ratio as a function of the average daily protein deposition, the average daily maintenance requirements and the average daily intake of energy to be made. The dependence of the feed conversion ratio on each of these three factors was demonstrated.

After the substitution of plausible values for the energy costs of protein and of fat deposition, as well as for the average maintenance requirements, equations were derived for the estimation of the content of protein and of fat in the live-weight gain, when the total feed consumption and the number of days on test (20 to 90 kg.) were known. Using these equations, the average gain of fat and of protein in each year were estimated for the Danish Progeny Testing Stations during the period from 1926–7 to 1962–3. It was found that the decrease of the feed conversion ratio and consequent reduction in fat deposition which were achieved during this period, were accounted for mainly by an increase in daily protein deposition.

Monthly coat and skin samples were taken from three goats for one year in Australia, and from six others for two years in Scotland. The coat appeared to have a simple cycle of active growth in summer followed by inactivity in winter.

The kemp fibres of the outer coat formed brush ends at about the time of the autumn equinox and remained dormant until late spring. Follicles developed first in the foetus formed a brush first. No moult was obvious because new kemps grew before all the old ones had shed, the only manifestation of shedding being a shortening of the coat. The old wool tended to be lost before growth of the new, so that wool was completely lacking in the coat during summer.

Observations on skin sections showed that the majority of both kemp (primary) and under-wool (secondary) follicles become active immediately after the longest day, although there was a tendency for re-growth of wool fibres to be delayed, particularly in females.

Whereas the proportion of kemps with brush ends during winter reached 100%, the proportion among wool fibres was as low as 50%. A complete explanation for this is not yet evident. The bad winter of 1963 apparently caused a greater proportion of secondaries to form brush-ends earlier and to remain inactive longer.

Details are given of some of the histological features of brush formation.

This paper reports a paternal half sib analysis of data collected over 3 years to estimate additive genetic variance of growth between birth and 16 weeks in crossbred progeny derived from Down rams. The data were divided into two groups and pooled estimates of parameters obtained by two methods. The paternal half sib intra-class correlations varied between 0·017 and 0·057 depending on pooling group and method. It is suggested that such low correlations arise because (a) most of the lambs in the study were still sucking at slaughter, close to 16 weeks of age, and the trait measured is thus largely influenced by maternal milking ability (b) the selection practised in the Down breeds may have been effective and reduced genetic variation and (c) there is considerable inbreeding in the Down breeds.

In further analysis of data from four farms involving rams mated to more than one breed of ewe there was limited evidence of specific combining ability of growth between birth and 16 weeks of age for Welsh ewes compared to ewes of other breeds.

During the last 10 years many genetical polymorphisms have been discovered in blood proteins. The phenotypes within each system have usually been found to be determined by a series of two of more alleles at a single locus and between which there is no dominance. A number of investigations have compared the fitness of heterozygotes and homozygotes at these loci. Apart from examining for possible associations between heterozygosity and traits for which selection is likely, such as production characters in domestic animals, these investigations have taken one of two forms; either family data have been examined for agreement with Mendelian ratios or else the genotypic numbers in a population have been examined for agreement with Hardy-Weinberg expectations.

Results are presented of an investigation in which 10 bull calves were subjected to heat stress in a climatic chamber from 26 weeks of age to the age of puberty. A similar group of 8 calves sired by the same bull were simultaneously subjected to ambient temperatures in another chamber. Maximum temperature in the hot chamber was 35–36° C. for 8 hours daily and maximum temperature in the temperate chamber was 27° C.

Observations were made on weight and age at puberty and characteristics of the first five ejaculates obtained from each bull. Post-mortem examinations included: carcass weight, weight of all genital organs, measurement of sperm reserves in testicles and epididymides and histological observations of the seminiferous tubules. The results indicated that the hot temperature exposure retarded fertility but that libido was exhibited at essentially the same intensity by both groups. The quality of semen obtained and the concentration of the spermatozoa were much lower in the bulls subjected to the hot environment during their growth period prior to puberty. The poor quality of semen was associated with impaired spermatogenesis.

It is recommended that in all fertility studies conducted with exotic breeds in the tropics, semen of known uniform quality be used. Natural service should not be used.

Sixty-four yearling Friesian steers, in eight groups with eight animals per treatment, were fed on pelleted diets containing ground barley straw, maize and soya bean meal. The percentage of straw in the diets varied from 0% to 50% and the crude protein was adjusted in all diets to 12% on an air dried basis. Levels of 0, 10, 20 and 30% ground straw were tested in 1963–4 and 20, 30, 40 and 50% in 1964–5.

Growth rates in the range of 8·28–9·49 kg. per week were obtained, with growth rate falling significantly (P<0·05) by 0·36±0·15 kg. per week for each 10% increase in straw in the 1964–5 trial; the differences between treatments in the 1963–4 trial were non-significant. The efficiency of food conversion varied from 6·5:1 for 0% straw to 7·7:1 for 50% ground barley straw. Feed intake increased as the percentage of straw in the diet rose above 20%. Regressions relating those carcass measurements in which differences between groups were significant to the percentage of straw in the diet were not significant except that for eye muscle area (P<0·05). Neither carcass nor meat quality differed significantly in animals given 20 % and 50 % ground straw.

The results of digestibility trials with male hoggets showed a linear depression in the digestibility of diets as the percentage of straw increased.

The results are discussed in relation to previous knowledge of the factors affecting the voluntary feed intake of ruminants.

Agricultural Research Council, 1965. Recommended procedures used in the measurement of beef cattle and carcasses. H.M.S.O., London.

Fleece characteristics of three distinct strains of Scottish Blackface sheep were studied by sampling eighteen ewes of the Lanark, Galloway and Lewis strains on three occasions in a single year. During the period of maximum growth the Lewis strain, which is largely of historical interest, differed significantly from the others in S/P ratio and mean weight, diameter and degree of medullation in fine and coarse fibres. The differences between the other two strains were small and although a considerable range in fleece characteristics was found, most of the whole fleeces would be classed as ‘medium’ wool.

All three strains showed a considerable reduction in follicle output during the winter and spring months when differences amongst them were minimised.

Conditions exist in Ghana which could implicate vitamin A deficiency as a factor in causing the poor growth and breeding difficulties observed in local cattle. Lansbury (1960) reviewed some of the limiting factors in the nutrition of cattle on the Accra plains, and stated ‘the bleached dried up appearance of the Accra plains over much of the year is due to the fact that most of the grassland is little more than standing hay from which most, if not all, of the vitamin A or its precursors are likely to have been lost’. Northern Ghana, with its longer dry season, presents such an appearance for a more extended period.

Data are presented concerning the efficiency of growth of Specific-Pathogen-Free Large White boars on individual performance test. Various aspects of growth rate, backfat thickness and food conversion are compared.

It is suggested that tests should be shortened by starting later, rather than finishing earlier.

Some support is given to the theory that one type of pig may not be suitable, from the point of view of efficiency of growth, for supplying the full range of carcass weights in current demand.

The physiology of indigenous West African cattle has not been investigated thoroughly. The ability of native cattle to survive on dietary regimes drastically deficient by standards based on requirements of temperate zone cattle, indicates an adaptability suggestive of a physiology differing from that of temperate zone cattle. The study reported herein was conducted to provide information on one aspect of this problem; namely the haemoglobin levels of indigenous cattle, as influenced by breed, season of year, growth characteristics and nutrient intake.

The variations that occur in saliva flow in cattle at rest may affect digestive processes in the reticulo-rumen (Bailey and Balch, 1961). To learn more about the effects of variations in saliva flow on digestion, it would be of value to have a reliable method of measuring saliva flow in intact animals. Stevens and Sellers (1959) showed that emptying the rumens of cows altered the rate at which saliva was swallowed and suggested that this was a result of changes in the rate of secretion. The rate of swallowing was measured during the course of experiments on saliva secretion described earlier (Bailey and Balch, 1961). Those earlier values are here analysed to study the relationship between rate of secretion of saliva and rate of swallowing.

Investigations of measurable properties of pig muscle have been carried out in many countries (Scheper, 1962). This note describes the effect of sex on six characteristics of longissimus dorsi muscles, i.e. content of moisture, fat, total nitrogen, expressible moisture, myoglobin, total pigment and colour (light reflectance).

Open front pole barns have proved to be very economical for the housing of feeder cattle, dry stock and, in certain areas, milking cows in Canada. In California, Heitman and Hughes (1949), Heitman, Kelly and Bond (1958) and Heitman, Kelly and Hughes (1949) investigated the effect of ambient temperatures (40 to 110° F.) and humidity on rate of gain in swine. Optimum temperatures for rate of gain were 73·5° F. and 61° F., for pigs of 100 lb. and 300 lb. live-weight, respectively. Hazen, Currie and Giese (1950), at Iowa State College, showed that growing swine weighing under 100 lb. are less severely affected by cold weather (34 to 40° F.), when protected from wind and wet, than heavier animals are by high temperatures.

The maintenance requirement for digestible organic matter of adult sheep has been derived by Wood and Capstick (1926) and more recently by Lang-lands, Corbett, McDonald and Pullar (1963) by means of regression analysis of data for feed intake, live-weight and live-weight gain.

As data from digestibility trials carried out both in Trinidad and Venezuela were available, similar equations were derived for adult male sheep under tropical conditions. Groups of six adult male sheep were housed individually and total collections of faeces and urine were made for periods of 10 days after preliminary periods of 7 or 10 days. The quantity of forage offered was generally that which the individual sheep would eat without leaving a large residue. The results obtained in these trials and a more detailed description of the methods used have been described elsewhere (Butterworth, 1963; 1965). In all, 178 sets of data were used. Each set for an individual animal consisted of daily intake of digestible organic matter (D), the mean (W) of initial and final body weights, and daily change in weight (G) all in lb. Values of D and G were means obtained from the results for the 10-dayperiod. The value of G was subject to high error in determination as periods were short and measurement of weight change in ruminant animals over short periods is most unreliable (see for example, Lush, Christensen, Wilson and Black, 1928; Whiteman, Chambers, Loggins, Pope and Stephens, 1954). Mean values and ranges of the values were as follows: D=0·96 lb. (0·46–1·87 lb.), W=84·2 lb. (56·0–149·0 lb.) and G=0·02 lb. (-0·5-+0·5 lb.). The digestibility coefficients for the dry matter of the various forages used ranged from 47·3 to 68·0%.

The design and evaluation of breeding programmes for live-weight-for-age (LFA) in dairy cattle requires estimates of the heritability and the additive genetic and residual components of variance for this trait, and also of its genetic correlation with milk production. A number of estimates of these parameters are available (summarised recently by Langelet, 1963; Mason, 1964; and Nichols and White, 1964). They are, however, generally based on rather limited data, on data from cows rather than bull-calves, or on data from dual purpose cattle. In this note estimates of the variance components and heritability for LFA in dairy cattle bull calves, and of the genetic correlation between bull calf LFA and milk production will be presented.

Since, under Irish conditions, the source of protein used in pig rations often varies from one area to another, an experiment was conducted to determine the accumulation of copper in the tissues of pigs given the commonly-used

protein sources in diets containing 250 ppm of supplemental copper. The protein sources compared were (a) white-fish meal (370 ppm Cu), (b) soya bean meal (17 ppm. Cu), (c) roller-dried skim milk (2 ppm Cu), and (d) a mixture of soya bean meal and meat and bone meal (5 ppm Cu) (Table 1). The minerals, vitamins and copper sulphate were premixed with about 5 kg. of barley and distributed over the total feed before mixing. The copper sulphate was sieved to remove coarse particles. Analyses of complete feed mixtures are shown in Table 1. As far as possible, the rations were balanced for crude protein, calcium and phosphorus.

Livingston (1962) showed that high levels of dietary protein during pregnancy increased the mean thickness of muscle fibres of M. longissimus dorsi and M. psoas majoris in newly-born piglets. Livingston did not detect this effect in pigs killed at pork weight. Preliminary results of Elsley and MacPherson (1964) indicated that the concentration of dietary protein during pregnancy can influence the nitrogen content of newly-born pigs when birth weight is standardised to 1 kg. to reduce variation; subsequent results (Elsley, MacPherson and McDonald, unpublished data) did not confirm these findings. Any differences attributable to the nutrition of the pregnant sow which are present in the newly-born pig are of practical importance only if they are reflected in changes in subsequent performance.