In a series of observations the association between within-litter variation in growth performance of piglets to 3 weeks of age and other parameters was examined in 28 litters. Growth rate was correlated significantly with birth weight and milk intake of the piglet. Birth order and location of the preferred teat did not influence significantly the milk intake or growth performance. In a second series of observations the individual behaviour of the piglets immediately after birth was examined in relation to the within-litter variation in growth performance to 3 weeks of age in three litters. The amount of time that each teat was sucked during the period of continuous suckle was positively correlated with the growth performance of the piglet which preferred the teat at day 21 of lactation.

Seventy-five enzootic pneumonia-free female pigs (sows) were allocated at random to one of five treatment groups. Four of these groups were weaned following a 10-day lactation period and were fed either 2 or 4 kg per day in lactation and either 2 or 4 kg per day from weaning to remating, such that the patterns of feeding for the four groups in the two periods were: 4 kg, 4 kg (HH); 4 kg, 2 kg (HL); 2 kg, 4 kg (LH) and 2 kg, 2 kg (LL). A fifth treatment group (control) was weaned following a 42-day lactation period and was fed up to 6·3 kg/day, depending on litter size and 2·7 kg/day from weaning to remating. Level of feeding for the four early-weaned groups in both lactation and in the interval from weaning to remating significantly (P < 0·001) affected the weight changes of the sows during these periods. The interval from weaning to oestrus for the early-weaned sows (8·2 days) was significantly (P < 0·001) greater than for the control sows (4·5 days), but this interval was not affected by level of feeding either in lactation or in the remating period for the early-weaned sows. Litter size at the subsequent farrowing for the early-weaned sows (9·3 piglets) was significantly (P < 0·001) less than litter size for the control sows (12·0 piglets). Level of feeding in lactation or in the weaning to remating period had no effect on subsequent litter size of the early-weaned sows.

Starting in 1959 from a crossbred foundation, a specialized synthetic sire line has been developed with the aim of making rapid genetic improvement in lean meat production. Within-line selection, firston ultrasonic backfat and then on a performance index, was supplemented over 11 generations by a process of competitive immigration, in which individuals of any breed from outside were incorporated into the line on merit. By Generation 11 the Sire Line contained genes from 9 pure breeds and 2 hybrid strains.

After a rapid initial phenotypic decline in backfat, there was little apparent response to index selection. In Generation 11, a centrally tested sample of the Sire Line showed significant improvements over contemporary Large Whites in growth rate, feed efficiency, eye-muscle area, lean percentage and some fat depths, but was significantly worse in killing-out percentage. With the exception of teat number there was no evidence of a decline in reproductive performance, to which no attention was paid during selection. Estimated heritabilities of growth rate and backfat were not sufficiently different from those reported for purebred pig populations to indicate that additive genetic variance had been changed by mixing breeds. Some of the advantages and disadvantages of the ‘open synthetic’ method of genetic improvement are discussed.

The implications of genetic variation in maternal performance for the relative merits of common selection strategies have been investigated. If the accuracy of progeny testing is computed without taking maternal effects into account, the estimate is biased upward. This bias increases as the correlation between direct and maternal genetic effects decreases from positive to negative values. The relative efficiency of progeny and performance test selection is a function of the heritability of direct and maternal genetic effects and the correlation between them. In terms of genetic gain per unit time, progeny testing is almost always less efficient than performance testing. For sire line improvement progeny testing is relatively more useful but is still likely to be less efficient than performance test selection unless there is a negative correlation between direct and maternal genetic effects or the correlation between purebred and crossbred direct genetic effects is very low or negative.

Analysis of body weight at 6 and 14 weeks of age in Galway sheep has shown that maternal genetic effects are an important source of variation in this population.

Two groups of 4 Suffolk rams were each subjected to mating pressures of 90 ejaculates (High) and 45 ejaculates (Low) over a 3-day period during summer and autumn. Every sixth (High) or every third (Low) ejaculate was collected into an artificial vagina and assessed for volume, sperm density, total sperm per ejaculate, motility and percentage of live and abnormal sperm.

There was a general lowering of semen quantity and quality with successive ejaculations. Rate of change of the various measures was greater on the High than on the Low mating pressure. Volume and percentage of live sperm showed a greater decline, and percentage of abnormal sperm a greater increase, during the autumn than during the summer. Density showed a greater decline in summer than in autumn.

The significance of the changes in semen characteristics observed is considered in relation to requirements for high fertility after pro-gestagen treatment.

A synthetic sire line has been developed over 11 generations by a process of selection accompanied by immigration. In each generation prospective immigrants of any breed were mated to native pigs already i n the Sire Line, and, ignoring breed, their progeny were given the same opportunity of being selected as the progeny from matings involving natives alone. This method of immigration is shown to be biased as a result of (a) heterosis in crosses of immigrants with natives, and (b) treating natives and immigrants as if they were members of the same population. When affected by both sources of bias, the breeding values of inferior immigrant progeny may be seriously overestimated with the result that inferior genes may enter the native population and hold back genetic progress. Methods of removing the bias and alternative systems of immigration are discussed.

Forty-five female pigs (sows) were allocated at random to one of three lactation lengths: 7 days, 21 days, 42 days. All sows were remated at the first post-weaning oestrus and were slaughtered at 20 days post coitum. The reproductive tracts were removed, dissected and examined. Ovulation rates as determined by luteal count were similar for all three groups, but the number of viable embryos decreased significantly (P < 0·05) from 13·0 for the 42-day lactation group to 9·2 for the 7-day lactation group. This difference was reflected in a significant (P < 0·01) reduction in the percentage embryo survival rate as lactation length was reduced. Uterine lengths for the 7-day lactation group were significantly (P < 0·05) shorter than the other two groups. Six sows in each treatment group were blood sampled: at weaning, at remating, at 2 days post-mating, at 10 days post-mating and at 20 days post-mating. The plasma samples obtained were assayed for progesterone. No differences were observed between treatment groups for plasma progesterone concentration at any of the sampling times. It is concluded that the reduction of the litter size at the next farrowing following a short lactation length is largely a result of increased embryo death in the first 20 days of gestation.

A model designed to simulate growth in pigs has been developed to include the following aspects of protein and energy use.

1. It is proposed that the ratio of protein accretion to protein synthesis is a function of protein mass. Synthesis rate influences the efficiency of protein use, the energy cost of protein accretion and the energy cost of maintenance. A calculated energy cost for protein synthesis of 7·3 MJ ME/kg is suggested; the calculated energy yield from deaminated protein is 11·5 MJ ME/kg.

2. Urinary losses of nitrogen are derived from estimates of protein quality by essential amino acid index, endogenous losses and the rate of protein accretion.

3. A minimum fat to protein ratio in the gain of growing pigs of 1: 1 is assumed.

4. An estimate of critical temperature which is dependent upon live weight and heat output is used to calculate energy expenditure for cold thermogenesis.

Four 2½-year-old Suffolk rams were each mated to groups of 24 Polled Dorset Horn ewes in which the oestrous cycles had been synchronized by the use of progestagen-impregnated vaginal sponges. Ram introduction occurred at either 24 or 48 hr after vaginal sponge withdrawal. Few ewes were in oestrus 24 hr after sponge withdrawal, but the majority were showing oestrus at the time of the 48-hr introduction. Mating behaviour and subsequent lambing performance of the ewes were recorded. All rams mated with the majority of their ewes. Rams introduced 48 hr after sponge withdrawal were found o t serve their ewes less frequently and over a more limited period, but they did succeed in mating with a greater proportion of their ewes during their first 30 services. There were no statistically significant differences in overall lambing rate between treatments, but the ratio of ewes lambing to ewes served on the 48-hr treatment was 92·5% compared with 72·2% for the 24-hr treatment (P < 0·05).

The taste responses of pygmy goats to addition of gymnemic acid (GymA), inosinic acid (InoA), or monosodium glutamate (MSG) t o sucrose or quinine monohydrochloride (QHC1) solutions were studied. Addition of 20, 40 or 100 p.p.m. GymA to 25 % sucrose (aversive) solution caused the goats to show strong preference responses. Addition of GymA to a 30 % sucrose solution did not change the response from strong rejection. Addition of GymA to 1000 p.p.m. QHC1 did not change the strong rejection response, but additions of 10, 20, 60, 80 or 100 p.p.m. GymA to a 200 p.p.m. QHC1 solution changed the response from rejection to non-discrimination or weak preference.

Addition of 50 to 500 p.p.m. InoA to 0·08 % sucrose solution did not change the response from non-discrimination; InoA added to a 6·25 p.p.m. QHC1 solution, changed the response from non-discrimination to rejection at 50 p.p.m. and to strong rejection at 250 p.p.m. When MSG was added to 0·08% sucrose solution, the response remained non-discriminatory until 500 p.p.m. MSG was reached; this elicited a weak rejection. MSG (5, 50, or 500 p.p.m.) added to 10 % sucrose solution, changed the response from moderate preference o t non-discrimination. With 30 % sucrose solution the response was changed from weak rejection to non-discrimination by addition of 5 or 50 p.p.m. MSG but reverted to weak rejection at 250 p.p.m. MSG and to non-discrimination at 500 p.p.m. MSG. The addition of 5 to 250 p.p.m. MSG to 100 p.p.m. QHC1 solution changed the taste response from moderate rejection to non-discrimination; 500 p.p.m. resulted in slight rejection. Addition of 5 to 500 p.p.m. MSG to 6·25 p.p.m. QHC1 solution did not change the response from non-discrimination.

A technique is described for assessing the profitability of selecting sheep for wool production. A model of the breeding system incorporating three submodels is developed: one to represent the flock from which the selection intensities for rams andewes are calculated; a second to determine gains made in wool production and the year in which they accrue; and the third uses discounting procedures to examine the economics of selecting for wool production.

Flock and genetic parameters were set at ‘average’ values for an Australian Merino wool producer and gains were determined for a range of lambing percentages. Three measures were used to evaluate profitability; the net present value of the programme which shows overall profits, the internal rate of return, which gives the earning rate of the programme, and the payback period, which identifies the number of years before early costs are repaid.

sensitivity analysis was used to examine changes in the three measures of profitability resulting from changes in interest rate, wool price, costs for labour and computer analysis, wool testing costs and lambing percentage. Profitability was sensitive to changes in all parameters except wool testing charges, and of the remainder the producer has a degree of control only over labour costs. A programme can be profitable, however, if wool price and lambing percentage are adequate and costs can be kept at reasonably low levels. Simple breeding programmes should be studied in which labour inputs are kept to a minimum or where costs are confined to studs (nuclei) and genetic gain disseminated by the sale (migration) of rams.

From among 27 rams of haemoglobin type A the two rams with the highest plasma copper concentration and the two rams with the lowest were selected on the basis of a single determination. In the same way four rams were selected from among the 29 rams of haemoglobin type B. The average difference between the ‘high’ and the ‘low’ rams was 103 μg copper per 100 ml plasma. The rams were mated to 105 unselected females. Lambs born as a result of these matings were blood-sampled on eight occasions from 3 weeks to 29 weeks of age.

The plasma copper levels of the lambs sired by the ‘high’ copper rams were higher on average than those sired by ‘low’ copper rams. The two groups diverged from 12 weeks of age onward to a maximum difference, at 29 weeks, of 18 μg copper per 100 ml plasma. There was also an initial difference of 13 μg at 3 weeks but a much smaller one at 6 and 9 weeks.

There was no corresponding difference in plasma copper concentration between the offspring of haemoglobin A and haemoglobin B rams. The results are therefore consistent with the hypothesis that the association previously observed in the same flock between haemo-globin type and plasma copper level is unlikely to be due to an effect of the gene controlling haemoglobin type, but could be due effectively to a linked ‘copper gene’.

Correlations between maternal plasma copper concentration 3 weeks after parturition and lamb's plasma copper level showed a marked decline as the lambs grew older, starting from around 0·6 at 3 or 6 weeks old. This suggests a maternal ‘environmental’ influence on lamb's plasma copper in addition to any genetic effects.

Two experiments were carried out using 130 Friesian-type castrated males (steers) to compare pelleted dried grass with rolled barley as supplements to high quality grass silage for fattening steers. There were six treatments in each experiment and, in addition, Experiment 1 had a pre-experimental slaughter group. The animals on each treatment were group-fed grass silage ad libitum for 98 and 112 days in Experiments 1 and 2 respectively. The treatments were (1) no supplement, (2) 1·5 kg dried grass, (3) 3·0 kg dried grass, (4) 4·5 kg dried grass, (5) 1·5 kg barley and (6) 3·0 kg barley per head daily. Each increase in the level of supplement depressed silage DM intake but there was no difference between dried grass and rolled barley. At each level of supplementation, live-weight and carcass-weight gain for animals fed dried grass and barley were similar. Responses in terms of live weight and carcass weight to increasing increments of supplementary feed declined as the level of supplementation was increased.

Insemination and calving dates were obtained for 2618 British Friesian cows served twice by artificial insemination, the first time unsuccessfully, the second time successfully. The intervals between the two inseminations formed a multi-modal set of normal distributions with peaks at 21-day cycles. The standard deviation of the Kth distribution was 3·0y/K days, with about 58·5% of eligible animals submitted at each cycle. Nearly 84% of all intervals conformed to the normal distributions, suggesting that embryonic mortality occurred in about 16% of cases following the first oestrus after insemination.

The rectal temperature of 208 lambs of Scottish Blackface, Tasmanian Merino, Southdown, Cheviot, Soay and Finnish Landrace breeds was measured between 15 and 25 min after birth, and that of 94 lambs again 1 hr after birth. Relationships within breeds between rectal temperature and birth weight, weather (temperature and wind speed) and gestational age were examined.

Within the range of birth weights and weather encountered over a period of years Scottish Blackface, Cheviot and Soay breeds maintained homeothermy at birth. In contrast, the Merino and Finnish Landrace breeds, which had comparable birth weights to the Black-face and Soay respectively, showed significant reductions in body temperature sometimes exceeding 10°C in cold weather. The Southdowns also showed hypothermia. In the Merinos and Finns, 30 and 54% respectively of the variation in rectal temperature was accounted for by birth weight and weather.

Of those lambs with low rectal temperatures 20 min after birth, few showed any improvement after 1 hr. Merinos in cold weather showed the least tendency to recover.

Possible reasons for the different performance of the breeds and the implications for lamb survival are discussed.

1. The effect of gathering reindeer on the composition of the blood was studied in female reindeer and their calves herded in northern Finland. Blood samples were taken in summer at three gathering places, under differing conditions and in autumn at the same places during gatherings which lasted for longer than 2 days. These were compared with samples taken from little-disturbed animals during winter.

2. Measurements were made of concentrations of glucose and lactate in whole blood and of urea, calcium, sodium, potassium and magnesium in serum, together with serum creatine phosphokinase (CPK) and glutamine oxalacetic transaminase (GOT) activities.

3. Gatherings affected nearly all the blood parameters studied. In summer the temperature during separation seemed to influence glucose and lactate concentrations. The duration of the gathering and the distance the animals were driven clearly affected serum GOT and urea values.

4. During the long autumn gathering serum urea concentration increased about eight-fold in 2 days accompanied by a simultaneous decrease in serum calcium.

5. Serum CPK and GOT activities were higher during the summer and autumn than during the winter. Serum CPK and blood glucose concentrations were higher in young calves than in adult females.

In 1968-69 for a mean period of 101 days before lambing, 72 cross-bred ewes, and in 1969-70 for a mean period of 88 days, 107 ewes were given roughage daily in the form of (a) 0·91 kg field-cured hay (b) 0·45 kg of hay plus 0·23 kg dried sugar-beet pulp nuts, or (c) 0·45 kg of pulp nuts. Each diet was supplemented by a concentrate allowance. From the 6th week before lambing was due to start, this allowance was progressively and uniformly increased.

There was no evidence that the dried sugar-beet pulp had adversely affected performance in terms of ewe body-weight change, lamb numbers, litter weight at birth or 4 weeks of age, fleece weight or general health. It is therefore concluded that dried sugar-beet pulp can be used safely as a replacement for hay in supplying up to 67% of the energy needed for maintenance by ewes.

Ensiled ear maize was compared with rolled barley as the cereal in a finishing diet for cattle weighing about 400 kg. The diets resulted in similar gains of about 1·2 kg/day.

A molassed sugar-beet product with added urea and dicalcium phosphate was evaluated as an energy and protein source for housed lactating ewes. Comparisons were made with a barley-vegetable protein and a barley-urea concentrate each formulated to supply approximately the same amount of crude protein. The overall performance of ewes and lambs given barley and vegetable protein was very significantly superior to that of ewes receiving the sugar-beet product. At 6 weeks after lambing the ewes given barley and vegetable protein had lost 57% (with singles) and 23% (with twins) less weight and their lambs had grown 28% (singles) and 48% (twins) more quickly than for ewes receiving the sugar-beet product. The intermediate performance of the ewes receiving barley and urea illustrated that the difference between the barley-vegetable protein concentrate and the sugar-beet product was both an energy and a protein effect.

Over an 8-week period pH measurements were taken in the longis-simus dorsi muscle of 17 157 bacon-weight carcasses at 45 min post mortem (pH1 ) in one abattoir. The overall least squares mean pHt was 6·38 and 9·9% of carcasses had pHt values of 5·9 or less. Neither sex, type of dam, breed nor testing background of sire of the carcasses examined had a significant effect on muscle pHj or the incidence of values below p H 6·0. Although first-grade carcasses had a higher incidence of low pHj values relative to those in the other grades, it was of no practical significance. Carcasses of homebred pigs had a higher incidence of muscle pHt values of 5·9 and below (2%) compared with those from pigs initially purchased as weaners. There was a marked producer effect on muscle pHj and the incidence of values below pH 6·0.