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A trial was carried out to estimate how accurately calves sorted into classes by sex, breed and nutritional background can be placed into one of three sub-classes by visual assessment. Eight recorders independently assessed each group twice in August when calves were a month old, and six recorders repeated the exercise 4 months later. Calves were visually assessed first for liveweight, as if they were potential breeding stock ('weight assessment'), and secondly for whatever criteria the recorders might use for potential breeding stock for sale in their own herds ('stud assessment'). The objective was to simulate two possible forms of visual assessment in a bull breeder's herd, with the actual weight records being used here for comparison. Both visual assessments were compared additionally with weight records adjusted for calf age and dam age. The results were expressed in terms of the weight difference (W1) of animals visually classed by the recorder into the top vs bottom third of a group, compared with the weight difference (W2) attainable by using objective measurement at the same age, i.e. 100x W1/W2. Where the standard was unadjusted weight, then W2 in August was 31.6 kg overall. In the stud assessment recorders found that calves in the top vs bottom third differed by 17.4 kg, and by 18.4 kg in the weight assessment, equivalent respectively to 55% and 58% of the possible selection pressure attainable. Comparing only weight assessments against August weights which were adjusted for calf age and dam age, 48% of the potential selection pressure was attainable. In the December assessments, recorders were randomly allocated to first making stud assessments followed by weight assessments, or vice versa. Subsequent analysis showed that the sequence was not important. Compared with December liveweights adjusted for calf age and dam age, the selection intensities attainable by stud and weight assessment were 41 and 48%, respectively. The implications of these findings for the Australian beef bull breeding industry are discussed.

Data from cows in two Angus lines, established in 1971 and comprising a yearling weight selection line (AS1) and its contemporary control (ACO), were recorded over three periods per year to estimate food intakes at pasture in a 3-year study begun in 1991. In each period, daily organic matter intake (DOMI) was estimated using chromic oxide slow-release devices. In total, 126 cows were included over an average of 2.6 periods each. Forty-six cows were slaughtered after weaning to determine if there were any line differences in body composition. The repeatability of DOMI estimates was 0.460.04, whilst the value between cows was 0.240.05. The AS1 cows were 15.0% heavier and ate 10.5% more than the ACO cows (P < 0.001). Estimated intakes per unit body weight or per unit metabolic body weight did not differ between lines. Adjusted calf weaning weights at 6 months of age per unit DOMI of the dam were 20.2 and 19.4 kg/kg respectively ( P < 0.05), a 4.1% increase by the AS1 line. The AS1 cows had 17.7% (P < 0.001) heavier carcasses than ACO cows. When adjusted to equal hot carcass weight on a log-log basis, AS1 cows had significantly more bone and less fat ( P < 0.01) than ACO cows. Kidney weights, but not heart or liver weights, were significantly greater for AS1 cows than for ACO cows (P < 0.01) when adjusted to a constant empty live weight. It was concluded that the cow-calf pairs in the AS1 line had a 4% greater calf weaning weight per unit of DOMI by cows than those in the ACO line, and differences were associated with cows which had relatively larger kidneys, more % bone and less % carcass fat soon after weaning.

The effects of three 'sire' breeds (Merino, Dorset Horn and Border Leicester) and four lambing dates (LD) on Merino ewe reproductive data and premating liveweights, lamb weights and greasy fleece weights up to 19 months of age were studied. The trial was replicated over 4 lambing years, 1972-75, with approximately 1200 ewes joined per year. A sample 490 lambs per year was recorded after weaning through to 19 months, with the 5-month period between the first December and the following May further subdivided into feeding treatments (two each for the 1972-74 lambings and three for the 1975 lambing). The feeding treatments in all years were pasture v. pasture plus ad libitum cereals (PC), augmented in 1975 by a pasture plus ad libitum cereals and lupins (PCL) treatment. The feeding trials were replicated over seven sites across southern Western Australia, with lambs remaining at the same sites until November. Lamb weaning percentages ranged from 51-80% in the 12 treatment groups (three breeds x four LDs), with sire breed x LD interactions (P=0.06). Year of lambing significantly affected all measured traits of ewes (P < 0.01, except lamb survival, P < 0.05). Breed of ram affected the percentage of ewes lambing (75, 72 and 69; P<0.01) and lambs weaned (72, 67 and 64; P < 0.01), favouring Merino over Dorset Horn over Border Leicester. Lambing in July (LD3, joining about 30 January) was the least productive (P < 0.01), with no significant difference between the two earlier or the later lambing dates. Average ewe liveweights at the start of joining varied with LD treatments (P< 0.01), but group means of ewe reproductive performance were not related to these liveweights. Sire breed effects on lamb birth weight, weaning weight at fixed age of 12-13 weeks and December weight were all ranked in the same order: Border Leicester (heaviest), Dorset Horn, Merino ( P< 0.01). For December weight, the superiority of Border Leicester-sired over Merino-sired lambs was 5.4 kg (21%). The LD effects were also significant ( P < 0.01), with fixed-age weaning weight favouring LD3 lambs, but December weights favouring LD1, LD2 and LD3 in turn above LD4, with a margin of LDr over LD4 of 14.2 kg (64%). December weights of adjacent LD groups differed by 4.7 kg (0.11 kg/day), about equivalent to the within-LD regression of December weight on birth date. Productivity differences (combining reproduction and lamb liveweights), for the 12 sire breed x LD groups indicated an almost two fold range in December weight. For liveweights in the second year of life, regressions ( s.e.) of May or November weights on previous December weights (within subclasses) were 0.86 k 0.02 and 1.05 0.04 kg/kg. The PC feeding treatment achieved a 4.1 kg (7%) liveweight margin in November weight plus 0.7 kg greasy fleece weight, at a food cost of 71 3 g/sheep.day (total 11 3 kg/sheep). The PCL treatment achieved a further 2.6 kg liveweight plus 0.1 kg greasy fleece weight at a food cost of 23 kg (+26 kg lupin grain, - 3 kg oats). The liveweight advantages immediately after the feeding trial in May were about double those 6 months later. Effects of sex and birthtype were significant (P<0.01), even at 19 months of age, but birthdate differences within LD were not significant. Border Leicester cross sheep consumed 139 g/day (22%) more than Merinos ( P < 0.01), but achieved no greater weight margin than when unsupplemented.

In each of 4 years, drafts of Shorthorn and Dairy x Shorthorn heifers were run together and fed to grow either slowly or moderately from weaning at 7 months until joining for two months at 15 months of age. Thereafter they grazed together on improved pasture in a 430 mm rainfall Mediterranean environment. Their performance was compared until their second calving and their calves' performances until weaning. Year x breed type interactions were significant for most variables measured. Between their first joining and first calving, the fourth draft of Shorthorn heifers gained 59 kg less liveweight than the crossbreds, but there was little difference in liveweight gain between the breed types in the other three drafts. Survival of the fourth draft of Shorthorn dams and calves was also 32 and 42% lower than of crossbreds. Concurrently, the third draft of Shorthorns lost 21 kg more liveweight than the crossbreds between first calving and their second joining, but performed similarly or better in the other 3 years. The third draft of Shorthorns also had a 63% lower second calving rate than the crossbreds, but the previous drafts had a similar rate of second calving. The average weaning weights of the second and third drafts of Shorthorn calves were 37 and 34 kg lower, respectively, than the crossbred calves, but only 8 and 16 kg lower in the first and fourth drafts, respectively. The third draft of Shorthorn dams were 90 kg lighter at weaning than the crossbreds but the other Shorthorn drafts were only 20 to 29 kg lighter. The intercalving interval of the fourth draft of Shorthorns was 28 days longer than that of the crossbreds, but was similar to or 23 to 30 days shorter for the previous drafts. Superior performance of the crossbreds was most apparent in the year of lowest rainfall and pasture availability, during which the third draft suckled their first calves and were joined for the second time and the fourth draft calved for the first time. First calving dates of dairy crossbreds were 14 days later than those of Shorthorns if grown slowly before joining, but were similar if grown moderately. Crossbred dams suffered 11 and 25% more dystokia at first calving of the first and third drafts and 14% more if grown slowly, but not if grown moderately before their first joining. Birth weights of calves out of crossbred dams were consistently 2 kg higher than those out of Shorthorn dams. First calving rates of the two types of cattle were similar and high (about 90%).

In each of 4 years, Shorthorn and Dairy x Shorthorn heifers were fed for moderate (55 to 101 kg) or slow (1 7 to 50 kg) growth from weaning at 7 months until joining at 15 months of age. Thereafter they grazed together on improved pasture in a 430 mm rainfall Mediterranean environment. Their performance was compared until their second calving and their calves' performance until weaning. The heifers that had grown moderately prior to their first joining had 25 to 73 kg higher average liveweight and 3 to 7 mm higher ultrasonic backfat reading during first joining, a 9% higher calving rate, 14 kg higher average liveweight but a 10% lower dystokia rate at calving, and 12 kg higher average liveweight and 1 mm higher ultrasonic backfat reading at their second joining, than those that had grown slowly. Survival of dams and calves, date of first calving, calf birth weight, second calving rate, intercalving interval and date of second calving were not significantly affected by the rate of growth prior to first joining. The effect upon dams' weight at weaning (moderate 11 kg higher than slow) was significant only at P< 0.1. Most aspects of performance differed widely amongst years, but significant year x growth interactions were only found for liveweight and condition of heifers at first joining, and for weaning weight of calf. The calves of moderately-grown heifers were of significantly lower mean weaning weight than those of the slowly-grown heifers, but only in those years when the mean mid-joining weight of the moderately grown heifers exceeded 315 kg. It is suggested that high fertility and satisfactory first calf growth are not incompatible provided that growth between the heifers' weaning and first joining is limited to that which results in a mean mid-joining liveweight not more than 20 kg higher than the target weight for 90% calving.

Results from farm performance tests of Landrace and Large White pigs were collected over 14 months in a nucleus herd in Western Australia. They were used to make offspring-sire estimates of heritability for average daily gain and two combined ultrasonic fat depths (CK fat). Pigs were tested at about 85 kg and average daily gain was estimated from birth. Only 60% of records from the offspring of homebred sires were analysed, together with the performance test records from all of these sires. Data were adjusted for breed, and then contemporary deviations were estimated as the deviation of a pig's performance from that of all his contemporaries. The offspring-sire heritability estimates accounted for the effects of breed and sex, with sums of squares then being pooled, giving values of 0.05 0.1 6 and 0.57 0.15 for average daily gain and CK fat, respectively. Adjustments for body weight increased the estimates to 0.27 and 0.68 but with larger standard errors. These latter heritability estimates were very similar to the paternal half sib estimates. The means of all offspring of homebred and purchased boars indicated no advantage of purchased boars over homebreds in the Landrace breed. However, for Large Whites, the purchased boars were genetically superior in average daily gain and inferior in CK fat (by 2.1 and 0.9 a, respectively, in the performance of progeny). The heritability estimates from this study, applied to group-fed farm-tested pigs, suggest similar results to those from central tests or farm tests in Queensland. However, some attention should be given in tested pigs to variation in final liveweights, and possibly to a start weight at weaning instead of at birth.

Economic values were estimated for net reproduction (N) and carcase weight production (P) in beef cattle herds. Weight selection referred to selecting for weight-for-age, not relative growth. Calculations were based on data that apply to the last seven years of Australian production. If considered only in terms of the change in total value of beef sold, a 5% increase in N or P gave an increase of about 4.1 %, according to the model. Improvements in biological efficiency, measured on a herd basis as total food energy input per unit weight of beef produced, were expected to be about - 2.5% per 5% dN/N, according to the model. Values for P were determined by the fundamental assumptions of the model, with literature review estimates having suggested no change in biological efficiency (as long as N remained constant). Small improvements in N resulted in a reduction in both food and non-food costs per unit of meat value sold. Economic efficiency (E) was defined as total costs per unit of meat value sold from breeding stock and growing-fattening stock, with reductions in E being favourable. In total, a 5% improvement in N yielded a change of about - 3% in E. The extent of change in E following selection for P (and for liveweight at the same time) depended on the assumptions applying, particularly with respect to food requirements and correlated cow weight changes. The most likely value was about - 2.5% dE/E for + 5% dP/P. Translated into a profit equation (H) on a dollar per cow-year basis, the most likely formula was H = 140n + 0.51 p, where n and p referred to small improvements in N and P per year, and N is a decimal fraction (not percentage), and P in kg.