Data from 22, 28, 36 and 41 pregnant cows in weeks 4, 3, 2 and 1 before calving respectively and 51, 65, 56 and 36 cows in weeks 1 to 4, 5 to 8, 9 to 12 and 13 to 16 of lactation respectively were used in multiple regression analyses to study the feasibility of predicting the daily total and the roughage organic matter and digestible organic matter intakes of cows given known weights of concentrates plus roughage ad libitum. The digestibility of the total intake and of the roughage component, the weight of concentrates eaten per day, the proportion of roughage in the total intake, age, milk yield, fat-corrected milk yield, live-weight gain and the 1·0, 0·73 and 0·66 exponents of live weight were used as independent variables.

The accuracy of the models was assessed from the significance of the partial regression coefficients, the size of the residual standard errors, and the population tolerance limits about predicted values, and by applying selected models to a set of data not included in the study. The results indicated that the precision likely to be achieved in the prediction of intake for individual cows was of limited practical application, but the mean intakes of groups of 30 similar cows could be predicted with an acceptable level of accuracy for practical application. In general, weight of concentrates offered and the digestibility of the roughage were the most effective independent variables in all cows, together with milk yield in lactating cows. The application of the results to conventional feeding systems and to complete diets offered ad libitum is discussed.

Barley which had been stored after treatment with 0·8 % propionic acid was incorporated into pig diets in either the milled or the rolled form and its feeding value compared with that of barley stored dry and then ground, and of moist barley stored anaerobically and then rolled. The pigs were fed from 50 to 200 lb live weight on the four diets. Their performance was not affected by the method of storage of the barley, but those given rolled barley required 11% more dry matter per unit of live-weight gain than those given milled barley. There were no significant differences between the treatments in carcass measurements, or in apparent digestibility coefficients as measured by the chromic-oxide method.

1. Seventy-two Blackface ewes with 96 Greyface (Border Leicester ♂ × Blackface ♀) lambs were allocated to three groups. Twenty-four ewes with 32 suckling lambs were set-stocked on 2·4 hectares (ha) of grass (A); 32 lambs were weaned and set-stocked on 2·4 ha of grass (B) and 32 lambs were weaned, housed and given concentrates (C). Beef cows with calves were used to control the grass in the two grazing groups.

2. The average initial live weight of the lambs was 18 kg. Treatments had a significant effect on performance, the live-weight gains per lamb over the initial 35 days being 11·2, 9·1 and 5·9 kg for groups A, B and C respectively. The total gains over 70 days, when the suckled lambs (A) were weaned, were 17·6, 15·5 and 14·3 kg.

3. The total live-weight gain per ha from lambs and calves over 88 days was higher on treatment B than on treatment A. The lambs weaned on to grass took 9 days longer than the suckled lambs to reach a slaughter weight of 42 kg and had significantly poorer killing-out percentages.

4.The lambs given concentrates had an overall food conversion efficiency of 4·89 kg concentrates per kg live-weight gain.

Regression equations have been tested relating average daily gains in pigs to average daily intake of crude protein, lysine, and TDN for each of three growth stages. The tests were based on output contour curves representing 1 lb, 1·4 lb and 1·75 lb live-weight gain per day in the three stages. On each contour, while crude protein intake was held constant, points were selected to represent the economically optimum combination of lysine and TDN intakes, a ‘high energy-low lysine’ combination and a ‘low energy-high lysine’ combination. For the latter two points, least cost mixes of feed ingredients were computed. Four feed mixes were computed at the economically optimum combination of lysine and TDN intakes. Comparisons were made between the performance of pigs given the six different mixes to assess the validity both of the slope of the output contour and its position and to examine the influence on growth performance of the ingredient specification of diets formulated to the same nutrient levels.

Using the six diets formulated on each contour, 12 feeding systems were developed all of which theoretically would take the pig from 50 to 200 lb in the same number of days. Six of these systems maintained the same diet type for each period; the others involved a change of diet type at least once during the three stages of growth. Diets formulated to meet the economically optimum combination of nutrients based largely on maize and groundnut meal stimulated inferior daily gains compared with alternative formulations. Both diets with a larger percentage of their lysine supplied from synthetic sources (the economically optimum combination based on maize and groundnut meal, and a low energy-high lysine combination) led to inferior daily gains. Pig performance was generally poorer than expectation, particularly from 50 to 150 lb live weight.

No differences could be attributed to differing ingredient composition in equi-nutrient diets. Similarly, no significant differences in growth rate were found between those systems which maintained a constant diet type throughout the three stages of growth. Pigs on systems which involved a change in diet type from one stage of growth to another grew in general slower than those pigs which had a fixed-diet type throughout.

Pigs on both diet combinations with a high percentage of weatings (a high cost formulation and a low energy-high lysine combination) had the best carcass results.

Four Finnish Landrace and four Scottish Blackface rams were exposed at 21-day intervals over a period of 19 months to two ovariectomized ewes, which had been induced to show oestrus. The behaviour of each ram was observed for 10 minutes with each ewe. Over the period of the experiment the Finnish Landrace rams consistently mounted the ewes more often than did the Blackfaces and in this respect in particular the reproductive behaviour of the males of these breeds was found to be positively correlated with that of the females of their breed.

Initially, however, the Finnish Landrace rams mated more ewes than did the Blackfaces, but from the time that all rams became sexually active it was impossible to differentiate between the ability of the two groups of rams to mate the ewes presented to them. Semen collections from each ram were attempted by the use of an artificial vagina, again at three-weekly intervals. The motility, density and proportion of live sperm did not differ between the two groups of rams.

The average number of mounts accredited to each ram during the test increased from around 5 in the summer to around 35 in the autumn.

Individual observations made in different weeks of lactation (WL) of live weight (LW, lb), milk yield (MY and FCM, lb/day), age (years) live-weight change (LWC, lb/day) and digestibility of the organic matter consumed (D, %) were used to produce models pre-dicting organic-matter intake (OMI, lb/day), digestibleorganic-matter intake (DOMI, lb/day) and faecal output (lb OM/day) in 72 grazing cows (Analysis A). Estimates of herbage availability (HA, lb dry matter/cow per day) applicable to 44 of the cows, together with the above variables were used in a similar manner (Analysis B). The multiple regression methods of analysis were applied solely to between-cow observations by selection of a single set of data from the many available for each cow.

FCM and LW0·73 gave better results than MY and LW, and together with age, were all significant variables for the prediction of the dependent variable. HA was not a significant source of variation, D was only effective in models of DOMI and faecal output, and stage of lactation was not considered a consistently useful variable. The application of the multiple regression technique to the problem of partition of nutrients and the prediction of intake is considered. Precision of prediction is discussed in terms of tolerance limits for predicted values, and it is concluded that the lack of accuracy of measurement of intake in the individual grazing cow is the major obstacle to the accurate prediction of intake in grazing cows.

The biological efficiency of meat production (E) is defined as the weight of carcass produced per 100 units of digestible organic matter (DOM) consumed. The factors affecting this relationship, for ewes and lambs, are discussed and the results of experiments are used to demonstrate the effect of number of lambs per year and size of ewe on the value of E. Calculations are made to show the effect on E of other factors such as the growth rate of the lambs and the weight at which the lambs are slaughtered. The general conclusions are that the highest values for E will be obtained from small breeds of ewes producing large litters and crossed with a large breed of ram, leading to a high growth rate and final size in the lamb. A relatively small increase in litter size in the small breeds of ewe (i.e. from one to two lambs) may result in a level of efficiency as high as that achieved by a larger breed with a large litter size (i.e. three to four lambs) without having to resort to techniques such as the artificial rearing of lambs.

The position of the incisor teeth in relation to the maxillary pad was examined in bulls (at approximately 10 months old). Visual gradings grouped into five classes were made on 5582 bulls of eight breeds in the course of inspection for licensing. In addition, measurements of the tooth positions (grouped into 11 classes) were made on separate samples of 1163 Galloway and 191 Ayrshire bulls.

Among the beef breeds 84·0% of all tooth positions were classed as being normal and 96·6% of those among the dairy breeds. The proportion of mouths with incisor teeth forward of the maxillary pad was higher among the beef breeds. Individual breeds within the beef and dairy types also differed significantly.

Herds of the Galloway and of the Ayrshire breeds, judged on the bulls submitted for licensing, differed in the distributions of the position at which the incisor teeth met the pad. Herds also differed when judged on the occlusion of the sons of their bulls.

Heritability was calculated for Galloways by half-sib correlation and sire-son regression, yielding estimates from 0·31 to 1·28, suggesting that at least some of the variation is inherited. The undershot and overshot conditions were found together only rarely among the male offspring of any one bull.

Twenty-eight female and 26 uncastrated male Scottish Blackface sheep were shorn and subjected to two acute cold exposures one week apart. Between exposures and for one week before the first exposure the sheep were kept either at +30°C (thermoneutral), or at +8°C (subcriticai), or at + 30°C with daily short cold shocks. Food intakes were restricted.

Females showed significantly greater resistance to body cooling than males during both acute exposures.

Both males and females showed acclimatization (increased resistance to body cooling) as a result of the first acute exposure.

Exposure to +8°C for one week did not produce significant acclimatization. Exposure to +8°C for two weeks tended, in females only, to increase acclimatization above that resulting from the first acute exposure.

Daily short cold shocks reduced cold resistance and inhibited acclimatization in females, but had little effect in males.

The male sheep lost significantly more weight during treatment and became thinner than the females. It was suggested that this, and their low cold resistance, might be related to a lesser ability of males to store fat as a subsequent source of energy.

A total of 156 pigs of the Large White breed were used in a series of four experiments to test the suitability of barley which had been stored with a high moisture content as an ingredient in the diets of growing pigs. Barleys with mean moisture contents of 26·3%, 28·1% and 21·2% and a range from 19·6% to 30·5%, from three successive harvests were used.

In all the trials there was evidence that the use of moist barley in diets for growing pigs had an adverse effect on live-weight gain and feed conversion ratio, the effect being independent of whether feed intakes were equated on the basis of the dry-matter content of the diets. In one of the experiments performance was depressed to the extent of causing changes in carcass characteristics. The performance of pigs given rolled barley was similar to that of others given ground barley.

In the national pig progeny test stations one diet is given up to about 55 kg live weight and another, with less protein, is given from then until slaughter. These diets were compared with four ‘single’ diets, similar in digestible-energy content, but containing either 15·6, 17·4, 18·7 or 22·1% crude protein, and each given unchanged from 18 to 93 kg live weight. There were twenty groups of one castrate and one gilt on each treatment.

Pigs given the lowest protein levels had the poorest growth rates and feed conversion efficiency up to 57 kg live weight, but the best from 57 to 93 kg. Hence there were no differences in overall feed efficiency, and overall growth rate was only slightly less with the lowest protein level than with other treatments.

Carcass leanness rose with protein level in the ‘single’ diets over the range 15·6·18·7% crude protein, but a further increase to 22·1% reduced leanness.

Pigs given the progeny test diets had carcasses intermediate in composition to those of pigs on the ‘single’ diets with 17·4% and 18·7% protein.

Data from 38000 Large White litters farrowed in 146 British herds were analysed to investigate the relative importance of various sources of variation affecting litter productivity. The effects of the season and the year of farrowing were very small relative to the effect of the herd of farrowing which was particularly large on the litter and average pig weights at three weeks. There was a small increase in the size of gilt litters as the age of the gilt at first farrowing increased. Litter size increased progressively with parity up to around the fourth litter and then declined gradually at higher pari-ties. There was a suggestion that the sire of a litter may hve a very small effect on litter size at birth but not at three weeks or eight weeks.

1. Scottish Half-bred ewes carrying twin foetuses were fed individually to make live-weight gains in the last six weeks of pregnancy of (1) 20%, (2) 10% and (3) 0% of their live weight in week 14 of pregnancy. In lactation the ewes were fed ad libitum. The lambs were removed 12 to 16 hr after parturition and the ewes were machine-milked twice daily for the first six weeks of lactation.

2. Total birth weights per ewe of twin lambs from the treatments were (1) 10·10 kg, (2) 9·44 kg and (3) 8·18 kg and differed significantly.

3. The level and pattern of voluntary intake in lactation did not differ significantly between the treatments. Total dry-matter intakes in the six weeks of lactation were (1) 121·9 kg (2) 105·9 kg and (3) 109·5 kg.

4. The pregnancy treatments affected the level of milk production and the shape of lactation curves. The total yields in the first six weeks of lactation were (1) 58·8 kg, (2) 43·5 kg and (3) 26·9 kg. Higher contents of fat and protein and the lower content of lactose in the milk from treatment-3 ewes on days 1 and 3 of lactation indicated a slower onset of lactation in these ewes. Between days 7 and 35 of lactation the contents of fat and SNF were lowest on treatment 3 but the differences were not significant.

5. The live-weight changes in lactation, which were in inverse order to the gains in late pregnancy, were (1) 3·4 kg, (2) 5·5 kg and (3) 9·5 kg.

Estimates of the heritability, the repeatability and the genetic cor-relation coefficients of litter performance traits were calculated from data on 38000 Large White litters farrowed in 146 British herds.

The repeatability estimates of number of live pigs per litter at birth, three weeks and eight weeks were 0·15, 0·14 and 0·14 respectively. The corresponding heritability estimates were 0·07±0·02, 0·07±0·02 and 0·09±0·03, respectively. The repeatability estimates of litter weight at three weeks and eight weeks were 0·15 and 0·04, while the corresponding heritabiUty estimates were 0·08±0·02 and 0·03±0·02. High positive genetic and phenotypic correlations were obtained between litter size and litter weight.

A number of model culling schemes were considered and it was found that even at relatively high culling levels the improvement in overall herd mean performance was very small. Direct selection for litter size may yield a useful rate of improvement if selection is con-fined to one trait and large selection differentials are achieved, but could not be economically justified.

A numerical model of AI selection procedures has been constructed in an attempt to assess the efficiency of current selection methods and to examine possibilities for their improvement. The results indicate that (1) present selection methods are relatively efficient in their utilization of test resources, but much less efficient in their usage of tested bulls. Additional investments in bull testing are likely to profit the dairy industry. (2) The main effects of improved bull utilization are (a) to permit increases in selection pressure with no increase in cost over current selection procedures and (b) to extend the limits to profitable selection. (3) The adoption of alternative stud management systems, in which bulls are slaughtered early in life, are likely to require excessively large investments in semen processing and storage.

1. A growth and digestibility trial was carried out with 27 British Friesian calves given diets having either 3·1, 2·8 or 2·4 Meal metabolizable energy per kg dry matter and either the same concentration of protein or the same protein-to-energy ratio.

2. Daily dry-matter intake and rate of gain in live weight increased significantly as the energy concentration of the diet was reduced. There were no significant differences in digestible-energy intake between calves given the different diets, although the trend was the same as for dry-matter intake.

3. Both dry-matter digestibility and energy digestibility were lowest for the low-energy diet.

Three trials were conducted to investigate the effect of length of journey by road to the abattoir, resting and feeding before slaughter on carcass characteristics of pigs of about 200 lb live weight.

Trial 1 investigated feeding or no feeding on the morning of slaughter, followed by a ½-hr or 8-hr journey by lorry to the abattoir with all pigs ending their journey and being killed at the same time. Ninety-six pigs were divided equally among the four treatments and the trial was repeated with a further 108 pigs. Measurements recorded on the live pigs and their carcasses included the live weight before the imposition of treatments, weight of liver, carcass and matured sides and the composition of a sample joint. Trial 2 studied lairaging overnight with food and water after a ½-hr or 8-hr journey to the abattoir compared with these journey lengths on the morning of slaughter. Eighty pigs were divided equally among the four treatments. Similar measurements to those in trial 1 were recorded. Trial 3 involved 49 pigs applied to each of three treatments, or 7-hr journey on the day of slaughter, with all pigs finishing their journey and being slaughtered at the same time.

In trial 1, pigs which travelled for 8 hr before slaughter had carcasses averaging 0·9% less than those which travelled for ½ hr, regardless of whether or not they were fed. It could not be established where this loss occurred. Liver weights were greater for those pigs which were fed and was greatest for those pigs which were fed and had the ½-hr journey. Streak thickness was found to be decreased by feeding, but was not affected by the length of the journey. No effects of the treatments were found on pH or eye-muscle colour, but the ultimate pH of the pigs fed before the 8-hr journey was lower than for the other treatments. Trial 2 pigs showed no effect of the treatments on carcass weights. Liver weights were similar on all treatments except for the treatment involving 8-hr journey followed by lairage where the liver was about 220 g (16%) heavier. The ultimate pH value was lowest among pigs which travelled 8 hr on the morning of slaughter but was similar for pigs on the other treatments. In trial 3, loss of live weight tended to increase with increasing journey length. Pigs on the 7-hr journey treatment had about 90 g (6%) more liver than those on the shorter journeys. pH1 values increased with length of journey and the longer the journey the thinner tended to be the maximum shoulder fat thickness.

From the differences in the results from the three trials, notably with carcass weight, it may be inferred that the behaviour and handling of pigs during the journey and during loading and unloading, may play an important part in determining the result of the length of the journey, resting and feeding. Further work is considered necessary to study such factors.

The potential benefits to be obtained from the adoption of performance testing for meat production in a dual-purpose breed have been examined and contrasted with those obtainable from improvements in dairy progeny test procedures.

It was concluded that capital investments in performance testing are likely to prove profitable, but less profitable than similar investments in the improvement of the dairy progeny test. Where performance testing is practised, there appears to be little advantage to be gained from the application of selection rates in excess of 1 in 3.

A system which allows group-housed animals to feed individually is described. In this systm animals have sole access to their individual feeding point and this access is unlimited in duration and frequency. The food intake and performance of growing Friesian castrated male calves housed and fed by two arrangemente of this feeding device have been compared with cattle that were group-housed and group-fed, and cattle individually penned. A4 × 4 latin square design was used.

No significant treatment differences were detected and the feeding device did not appear to affect the food intake, performance or behaviour of the cattle.

1. A growth trial was carried out with 21 Friesian steers given diets containing either 0%, 30% or 50% ground straw, and concentrates up to 100%.

2. Steers offered the diet containing 0% straw consumed less dry matter per day than steers on the other two treatments.

3. Rates of live-weight gain were 1·20, 1·04 and 0·87 kg/day for the three treatments respectively, and carcass gains were 690, 550 and 440 g/day.

4. Killing-out percentage dropped and alimentary-tract fill increased as the proportion of straw in the diet increased.

5. The dry-matter digestibility coefficients for the three diets, determined at maximal intake, were 79·1%, 62·3% and 56·6%, respectively.