The first paper of this series (Alder, Tayler and Rudman, 1964) described experiments carried out over 4 years on the effects of hexoestrol on live-weight gain and herbage intake in grazing steers. The 52 steers used weighed between 750 and 1,100 lb. initially and included four pairs of twins. The experiments lasted between 55 and 124 days and involved both summer and winter grazing. This paper is concerned with observations made on the animals after slaughter.

A study has been made of the performance of crosses and backcrosses of Bos taurus and Bos indicus cattle using records covering a period of 15 years from the Experimental Station, Tanga. The gene combinations found in ½-bred animals were the most productive in this environment, and ¼-bred Bos taurus animals gave higher average daily yields of milk between calvings than those with ¾ taurus blood.

Donald (1962) has recently pointed out the paucity of available data on production from British sheep, though some information is available for hill sheep (see for example Donald, 1958; Purser and Roberts, 1959; Purser and Young, 1959; Dalton, 1962). Most of these refer mainly to the Scottish Blackface and Welsh Mountain breeds. Hill sheep form approximately 40% of the national flock of over 11 million breeding ewes. Another 40% of ewes are found in crossbred flocks mainly kept on the lowlands; these produce fat lambs and hoggets with wool as a secondary product. Very little information has so far been published on these crossbred ewes, exceptions being work reported by Bywater (1945) and Rennie (1957). This is the first of three papers to be presented with the object of providing such information, and is based mainly on the work of Yalçin (1963). It is hoped that these papers will be of use on two counts:

1. To provide a documentation of one specific cross, the Border Leicester × Cheviot ewe and her Suffolk-cross lambs under North of England grassland conditions.

2. To analyse the usefulness of keeping production records within such flocks as aids to good commercial management, to culling and to selective breeding.

In this paper the traits studied are body weight, fleece weight and litter size of the ewes, and the weights of the lambs between birth and slaughter or weaning. Estimates were obtained for the effects upon some of these traits of age and live-weight of ewe, and of sex, year and type of birth and rearing of the lambs. The usefulness of such correction factors is considered within recording schemes. In subsequent papers the effects on production of differences between crossbred ewes and between the rams used as fat lamb sires will be considered.

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.

Progress by selecting in a single line for overall merit is compared with the progress by selecting and crossing specialised sire and dam lines. The sire line is selected for growth and carcass traits, the dam line for number of offspring produced. The rate of improvement through specialised lines is never less than that in a single line and can be considerably greater but only i f there is an unfavourable genetic correlation between progeny number and performance and if there is a certain balance between the heritabilities and economic weights of the two sets of traits. In a sire line the selection may ignore progeny number without loss in efficiency but in a dam line progeny growth and carcass performance must be considered in addition to the number of offspring or else substantial losses in the efficiency of improvement may be suffered.

From estimates of the relative economic weights and relative heritabilities of number of progeny produced and the efficiency of feed conversion in several meat species it was concluded that selecting in specialised lines will have little advantage over selecting for overall performance in a single line.

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.

There are many flocks in Britain where first-cross ewes are mated with a Down ram in order to produce offspring of both sexes to be fattened for slaughter between 3 and 12 months of age. The ewes are normally bred out of hill ewes by rams of the special crossing breeds, the Border Leicester being the most popular example. Commonly the crossbred flock is maintained by the annual buying in of young sheep at 6 or 18 months old. These replace animals lost through normal wastage and those sold after a set number of lamb crops. In such a situation the flock owner relies on others to produce his crossbred ewes and can himself do nothing to improve their performance through selective breeding. He can only attempt to cull ewes with a poor performance. Any gains from such culling are, of course, temporary and must be maintained by a regular system of culling within each separate intake of females. The success of a culling scheme depends partly upon the extent to which future production is predictable from past performances. This is normally assessed by the correlation between an individual's successive records: the intra-class correlation or repeatability (t). The work reported here estimates the repeatability of various productive traits within two crossbred ewe flocks and considers the scope for culling within such flocks.

1. Total concentrations of volatile fatty acids and molar proportions of acetic, nrooionic and butyric acids were determined in the rumen of Blackhead Persian sheep given sixteen low-protein diets.

2. Total concentrations of acids ranged from 2·89 to 9·33 millimoles/ 100 ml. of rumen liquor. Both digestibility and protein content of the ration had a significant effect on the concentration of volatile fatty acids in the rumen liquor. Protein content of the diet probably influenced the latter through controlling the rate of ruminal fermentation.

3. Molar proportions of acetic acid varied from 59·7% to 69·3%, of propionic acid from 21·2% to 29·6%, and of butyric plus higher acids from 7·6% to 16·3%. Protein content of the diet had no significant effect on the composition of the acid mixture, but organic matter digestibility was inversely related to the proportion of acetic acid.

4. The fermentation in the rumen of Blackhead Persian sheep, as judged by the volatile fatty acids produced, appears to be similar to that found in European breeds of sheep.

1. Four groups of diets made up with differing proportions of roughage and concentrates were each given ad lib. to 4 Blackhead Persian wether sheep. The four diets in each group contained approximately 4, 6, 8 and 10% crude protein. The distribution of nitrogen in the rumen at various times after feeding and the nitrogen balance of the sheep were measured.

2. Total N and ammoniacal N content of the rumen liquor were both closely related to the N content of the diet. Diurnal changes in the concentrations of these components were most marked with the diets which had the highest concentration of protein, and consisted of rapid increases after feeding followed by declines later in the day. Each group of diets produced characteristic patterns of change and these changes appeared to be related to the proportion of concentrates in the diet.

3. With sheep given poorly digested veldt grass, very low in protein, levels of ammonia in the rumen were unusually high. This effect was thought t o be due to the recycling of urea and its conversion to ammonia in the rumen.

4. The amounts of digestible N required by the sheep for N equilibrium differed between groups of diets. High apparent requirements of digestible N were associated with relatively high ruminal ammonia levels, but the latter were not considered to be the cause of high requirements.

5. On all groups of diets, sheep were in N equilibrium only when their intakes of total digestible nutrients (TDN) were adequate for maintenance. This indicates that the protein requirement for maintenance was a function of protein content and TDN content of the diet and the effect of these factors on voluntary intake of TDN.

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.

Six comparable groups, each of 4 castrate pigs, were used to compare the feed value of maize and sorghum as estimated by live-weight gain, food conversion efficiency, slaughter quality and ham composition.

The maize ration contained 40% yellow maize and the sorghum ration 40% Sorghum vulgare subglabrescens, all other ingredients being the same for both diets.

No statistically significant differences were found between the maize and sorghum pigs with regard to the criteria mentioned.

It is concluded that no difference exists between the feed value of the maize and the sorghum used. This result is in better agreement with the net energy values of maize and sorghum as calculated by the formula of Hoff-mann and digestion coefficients for pigs, than with “classical” starch equivalents.

1. Carcass dissection data and specific gravity determinations from 76 pigs slaughtered at either 120 lb., 200 lb., or 260 lb. live-weight have been analysed to study the value of specific gravity and its reciprocal in predicting fat and lean in the carcass.

2. Possible effects that the bone content of the carcass might have on the accuracy of prediction have been investigated.

3. Specific gravity was highly correlated with percentage fat and lean in the half carcass. Correlation coefficients for the reciprocal were of similar magnitude but opposite in sign.

4. The residual standard errors in percentage lean and fat at constant specific gravity were 1·74% and 1·72% respectively.

5. The replacement of specific gravity by its reciprocal did not increase the accuracy of prediction for either lean or fat tissue expressed as a percentage of the trimmed half carcass.

6. The muscle/fat ratio exerted a markedly greater influence on specific gravity than did the muscle/bone ratio. However, the inclusion of the latter ratio in equations relating specific gravity and percentage lean in the carcass, reduced the residual variation.

7. Application of the pooled regression equations to independent data, obtained by the use of identical techniques, has given promising results.

1. The transferrins in two cattle herds were studied by means of starch gel electrophoresis. Three phenotypes were observed in a Hereford herd and six in a Hybrid herd comprised of Galloway, Aberdeen Angus and Charolais breeds.

2. Gene frequencies were calculated for each herd. Great variation was found in the frequency of the transferrin alleles between breed and source within the Hybrid herd and between the Hybrid and Hereford herds. The frequencies of the transferrin alleles found in the cows in the Hereford herd were TfA = 0·467 and TfD = 0·533; those found in the cows in the Hybrid herd were TfA = 0·382, TfD = 0·506 and TfE = 0·112.

3. Progeny data were in general agreement with the three-allele theory of inheritance, although the data suggested that offspring in the Hybrid herd carrying the TfE allele occurred at a lower frequency than expected.

4. The possible relation of transferrin type to embryonic mortality was studied. The results were in general agreement with those of other workers, indicating a possible interaction between the genotypes of the foetus and dam.

5. The characteristics of the transferrin types and the postulated three-allele genetic mechanism for the control of the observed variation are discussed.

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.

1. Normal rations containing oleandomycin (2·5 g./ton), oxytetracycline (10 g./ton) and oleandomycin (2·5 g./ton)plus oxytetracycline (10 g./ton) were given to females and castrates which had previously received creep feed with or without oxytetracycline.

2. Forty-eight pigs were individually fed on the rations from 50 to 200 lb. live-weight, a restricted scale of intake based on live-weight being adopted.

3. Pigs receiving the mixed supplement and those given oxytetracycline alone grew significantly faster and utilised their feed more efficiently than those given oleandomycin alone. Differences between the mixed supplement group and those receiving oxytetracycline were not significant.

4. Treatment with antibiotic, either in the creep feed or after weaning, had no effect on carcass measurements. Females had less depth of fat at the shoulder, mid-back and loin compared with castrates and the carcasses were significantly longer.

5. Visceral weights were not influenced by antibiotic treatment but pigs supplemented with oleandomycin had a shorter gut than those receiving a combination of antibiotics. There was a significant reduction in gut weight n i pigs which had received unsupplemented creep feed but no consistent effect on the thickness of the intestine wall or gut diameter. Females had significantly heavier kidneys and spleens than castrates.

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.

In determining the milk yield of the sow by weighing the litter before and after suckling, loss of weight due to metabolic processes must be considered.

An experiment is described to investigate the loss of weight of piglets caused by metabolic processes between two consecutive weighings, and to investigate the relationship between this loss on the one hand and the body weight and the age of the piglets on the other. Weight changes of 15 litters of average 9·8 piglets were studied during 66 weighing periods of 16 minutes, by putting the pigs in a cage, fixed on a differential balance. Each weighing period consisted of 8 periods of 2 minutes, so that in all, loss of weight was studied during 528 2-minute periods.

In 1956 the authors showed that formalin could be satisfactorily used for the preservation of skim milk subsequently given to growing pigs from weaning to slaughter (Barber, Braude and Mitchell, 1956). Since then a large proportion of the skim milk used by pig producers in this country has had formalin added to it. No evidence from controlled experiments was hitherto available concerning the value of formalin-treated skim milk for the sucking pig, and it was for this purpose that the experiment reported was carried out.

Foote, Tyler and Casida (1959) found that the birth weight of Holstein calves from the right horn was significantly heavier than that of calves from the left horn but found no significant effect of side on gestation length. In a further study Foote, Hauser and Casida (1960) found no effect of side of pregnancy on either birth weight or gestation length in an analysis of 128 gestations among Angus and Shorthorn cows. They did find, however, a significant interaction of breed and side of pregnancy on gestation length.