Three groups of 10 Large White gilts were allocated on a littermate basis to 3 feeding regimes, for 3 successive pregnancies and lactations, to provide the following daily allowances: (A) 6 lb feed per day in pregnancy and 2 lb plus 1 lb per pig suckled in lactation; (B) the same total as (A) but given as 4 lb per day in regnancy and 6 lb plus 1 lb per pig suckled in lactation; (C) a lower overall allowance distributed during pregnancy as 5 lb during weeks 1, 2, 15 and 16, 3 to 5 lb during weeks 3, 4, 13 and 14 and 2 lb during weeks 5 to 12, and during lactation increasing by 1 lb per day to appetite or a maximum of 26 lb at the 21st day, and then decreasing by 1 lb every alternate day to a minimum of 5 lb. Creep-feed was provided ad libitum from 3 weeks of age until weaning at 8 weeks of age. Differences between groups in litter size and weight at birth were not significant but the combined measure of litter weight was significantly lower in C than in A and B (P<0·05); litter size (P<0·05) and litter weight (P<0·01) but not individual pig weight increased with parity. At 3 and 8 weeks of age there were no significant differences between groups in size or weight of litters or in individual pig weights. Pigs of Group C sows consumed significantly more (P< 0·001) creep feed (7 lb per head) than those of Groups A and B. Sows of Group A gained double the weight of Groups B and C during pregnancy (P<0001) and lost significantly more (P<0·001) during lactation; Groups B and C did not differ significantly in either respect. Efficiencies of feed conversion (EFC) of total food into total weight by sow and litter were poorest in Group A and best in Group C.

Six diets providing ratios of concentrate to hay of 100 : 0, 95 : 5, 90 : 10, 80 : 20, 70 : 30 and 60 : 40 were given ad libitum to 24 British Friesian steers. The hay (in the long form) was offered separately from the concentrates. From 91 to 136 kg live weight, as the proportion of hay in the diet increased, daily dry-matter intake decreased. Over the weight range, 136 to 363 kg live weight, the addition of small amounts of hay to the concentrate diet caused an increase in intake. At 42 weeks of age a digestibility trial was carried out. Daily drymatter intake was maximal when the diet contained 80% concentrates. The apparent digestibility and mean retention time of the diets increased as the proportion of concentrates increased. Differences in estimated gut fill were not significant. The diet consisting of concentrate only resulted in the lowest concentration of acetic acid and the highest concentration of propionic and butyric acids in the rumen liquor. Net-energy intake tended to increase as the proportion of concentrates increased from 60 to 90% but then remained fairly constant.

The growth and carcass characteristics of autumn-born Hereford × Ayrshire castrated male calves reared on two planes of nutrition have been studied. Restricted feeding for 12 weeks after weaning from liquid feed to the time the calves were turned out to grass created a difference of 52·0 lb per head in live-weight gain and 15·2 lb of this difference persisted at slaughter. There were small differences in carcass conformation and composition.

1. A comparison was made of the output per hectare and per cow of 3 systems of grazing management each based on a cycle of 5 days grazing followed by a 20-day rest period. The treatments were: C, strip grazing within a paddock, varying the area allotted so that a similar quantity of herbage was available each day, the pasture being frequently trimmed; treatment R, restricted grazing; the cows being allotted a fixed area of the paddock each day (67–5 m2 per cow per day) which was not trimmed or cut after grazing; and treatment RS, as treatment R but with each cow receiving cereal concentrates. Eight cows were on each treatment. Nitrogenous fertilizer was applied at the rate of 86 kg N per ha [1 kg per ha = 0.891b per acre] four weeks before the first grazing and at the same rate after each grazing; a total of 516 kg/ha was applied. The feed intake of each cow was measured on six occasions during the experiment.

2. The experiment continued for 150 days and the mean stocking rate on treatment C was 4–09 cows per ha [1 ha = 2·47 acre] and on the other two treatments 5·92 cows per ha. The number of cow grazing days per hectare were 610, 890 and 890 for treatments C, R and RS respectively and the outputs of milk were C 8450, R 12 420 and RS 13 380 kg/ha. Allowing for the concentrates given the milk outputs were C 7440, R 10 350 and RS 6660 kg/ha.

3. There were only slight differences between the treatments in output per animal.

4. The average intakes per kg W0·73 were similar in treatment C and R but the average intake of cows on treatment C was more uniform over the season. Cows on treatment RS ate consistently more digestible organic matter than those on treatment C and R but the differences became smaller as the season progressed.

In a comparative slaughter trial which covered growth from about 16 kg to 40 kg live weight, five groups of six Romney × Swaledale lambs were offered ad libitum five pelleted diets (A to E) in which rolled barley was gradually replaced by an 80 : 20 mixture of rolled oats : oat husks to the extent that the calculated metabolizable energy (ME) concentration fell from approximately 2–9 (A) to 2·5 (E) Mcal/kg DM.

Although daily live-weight gains did not differ significantly between treatments, the daily carcass gain fell from 143 g/day on A to 105 g/day on E (P<0·05) whereas gut contents increased from 9·9% of live weight to 16·1% (P< 0·001) from A to E. Differences in efficiency of utilization of ME above maintenance were variable but for gross efficiency (i.e. retention/total ME intake), there was a significant decline from A to E.

Dry-matter intakes for the whole experimental period were similar for all five diets, but initially intake was lower for diet E than for A (780 v. 927 g/day) and ultimately it was higher for E (1410 v. 1150 g/day). In a second experiment, involving diets A and E and a third diet of chopped dried grass, the pattern of intake and growth changed with live weight in a similar manner to that described above, except that appetite and growth on dried grass were consistently poorer. Daily variation in intake and rumen pH tended to be greater on the concentrate diets.

It is suggested that, amongst other factors, the stage of maturity of an animal may influence the point at which the digestible energy content of the diet restricts dietary intake in preference to physical limitations.

The effect of gradually replacing barley with swedes or potatoes on intake of digestible dry matter and on the volatile fatty acid (VFA) composition of liquor was measured in an experiment with eight female and four castrated male sheep approximately six months old. The total intake of digestible dry matter was greatest when rolled barley was given at two-thirds of estimated maximal intake and roots given ad libitum. The intake of digestible dry matter was reduced to 80% of the highest intake when all the barley was substituted with swedes and to 70% of the highest intake when all the barley was substituted with potatoes. Replacing barley with roots had little or no influence on VFA composition.

1. Two experiments have been carried out to study the nutritive value of dilute solutions of fatty acids (consisting mainly of ammonium acetate) when incorporated in the diet of lactating Jersey cows.

The first, a continuous trial, extended over a total of 17 weeks and involved five pairs of cows. One cow in each pair received the treatment and one the control diet. The second trial, of change-over design, involved four pairs of cows; one cow in each pair received one or other of the experimental diets alternately over four 28-day periods.

2. The cows received basic diets comprising hay ad libitum and concentrates regulated according to milk yield. On the control treatment cows received water and a concentrate containing an appropriate percentage of groundnut cake; on treatment cows received a dilute solution of salts and an ‘all-cereal’ concentrate. The treatment provided cows with approximately 30% of their total DCP intake as ammonia-N and with 270 to 310 g of acetate and 43 to 49 g of propionate/day from the salt solution.

3. Solutions of salts have been offered to the cows at various concentrations in the range 0·25 to 2·6% (w/v) as a substitute for drinking water. Nineteen of the 20 cows consumed solutions of 1·4% concentration in normal quantities equivalent to water.

4. Treatment was associated with an appreciable depression in the yield of cows producing 13 to 14 kg of milk per head/day, but had little effect on the yield of cows producing 10 to U kg or less. This result has been discussed with reference to the role of the ammonia-N as a substitute for protein-N.

5. Treatment significantly increased the fat content of the milk produced by these Jersey cows above the high control level of 5·4%. Total milk fat production was also increased. This result has been discussed with reference to the role of acetate in dairy cow diets.

1. The effect of feeding a salt solution containing ammonium acetate on the yield and fatty acid composition of cows' milk fat has been studied.

2. The trials involved eighteen lactating Jersey cows. In the first trial one group of 5 cows was fed the treatment diet throughout an experimental period of 10 weeks and another group of 5 cows acted as controls. In the second trial which extended over four 28-day periods, two groups of 4 cows spent alternate periods on treatment or control diets. The overall results of the two trials were in agreement.

3. The outputs of C4-C14 acids and of palmitic acid per kg of milk yielded were greater than the intakes. The output of C18 acids was less than the intake per kg of milk yielded. These observations were noted on both treatment and control.

4. Treatment resulted in an increased secretion of C4-C14 acids and of palmitic acid and a decreased secretion of C18 acids per kg of milk yielded.

5. The results have been discussed in the light of present knowledge concerning the synthesis of fat in the mammary gland.

Year, type of gestation (single or twin foetuses) and age of foetus all had highly significant independent effects on both foetal weight and length (P>0·01). Twin foetuses were both longer and heavier than single foetuses at 21 to 30 days post coitum. Continuous illumination, continuous darkness and intermittent light appeared to reduce foetal length and weight (P>0·05). Control foetuses were longer and heavier than those on other treatments. Neither feeding level (75 to 150% N.R.C. maintenance requirements) nor body weight of the dam had significant effects on foetal size within the age range studied.

Eight research and teaching centres have co-operated in an experiment involving 132 sows. Six treatments were used, combining three levels of feeding in pregnancy with two in lactation. Pregnancy treatments were High 3−2 kg meal/day, Medium 2·4 kg/day and Low 1·6 kg/day; in lactation either a high level, 4·1 kg plus 0·2 kg/pig (h) or a medium level, 2·3 kg plus 0·2 kg/pig (m) were given. The sows were maintained on the same nutritional regime for three parities although inevitably some sows were lost before the completion of the trial. Sow live-weight gains in pregnancy were directly related to feed intake; in lactation, losses in sow live weight were dependent on gains made in the previous pregnancy and on the level fed while suckling. After the first parity, in which animals fed the low level in pregnancy tended to produce larger litters (though the difference was not significant), there were no differences in numbers born attributable to treatments.

Increases in the feed intake of sows in pregnancy resulted in consistent and significant increases in the weight of the pigs at birth. This increase in birth weight also resulted in an increase in weight at weaning in the second and third parities. Level of feeding in lactation, which had a highly significant effect on sow live weight, had much less influence on weaning weights of pigs. There were no consistent pregnancy × lactation interactions, the effects of treatments in the two phases being additive.

An assessment is made of the relative efficiency of the six treatments and the value of the experiment is discussed in relation to other studies concerned with sow nutrition.

A portable EEL reflectometer was modified to measure the variations in the brightness of pig meat. The instrument was calibrated spectrophotometrically with reference to the luminous reflectance of standardized materials and selected meat samples. A very satisfactory level of agreement between the instrument and the visual assessment of muscle paleness was found in an investigation involving 251 pigs.

Haemoglobin types in three breeds of sheep were investigated. All three haemoglobin types—A, B and AB—were found to be present in the animals in two of the breeds examined, namely Bikaneri and Corriedale × Bikaneri (F1 generation). Mandia sheep had only Hb B and Hb AB types. Haemoglobin JB animals predominated in all the three breeds, the Mandia breed having the highest percentage of these animals. The possible significance of these findings is discussed.

The effect of the time of mating on ewe fertility and subsequent lamb growth was examined in Clun sheep in Scotland. The flock of 249 females was divided into six mating groups, the first was put to a fertile ram on 12 October 1962, the remainder being added at two weekly intervals.

There was a marked decline in the average number of lambs born per female lambing as the time of mating moved from October to December (b = −0·007 per female per day). Other components of fertility were not affected.

The mean birth weight was slightly greater in the later mating groups; however, by the time the lambs were 9 weeks of age, the trend was reversed, the regression of 9-week weight on day of mating being −0·063 lb per day.

A by-product of the distilling industry designated ‘distillers’ grains plus solubles' was evaluated using forty-eight growing pigs. The product was included at 0, 14·7 and 25% in three diets in which the proportion of other constituents was adjusted to give similar concentrations of TDN, dry matter and crude protein.

The performance and carcass quality of pigs receiving 0% and 14·7% of the by-product in the diet was similar, but inclusion at 25% significantly reduced growth rate (g/day) from 632 for the 0% diet to 578.

Voluntary hay intake and milk yield were measured in 11 singlesuckling and 4 twin-suckling ewes for the first seven weeks of lactation. There was no significant difference between the intakes of the two classes of ewe and milk yield differed only in the seventh week. Variations in milk yield and live-weight change were significantly associated with variations in voluntary intake. Lamb weight gain was correlated with milk yield and voluntary intake of the dam.

A small scale ewe-recording scheme, involving a minimum of weighing, is described. Results for two years and two breeds have been analysed to produce correction factors in each year for birth type, sex and age of dam in respect of birth weights and weights at 84 days of age derived with and without reference to birth weight. The results suggest that breed differences in correction factors may exist and that differences between years in correction factors may be of minor importance. In standardizing weaning weights to a constant age the influence of birth weight appeared to be relatively unimportant.