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.

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.

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.

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.

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 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.

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.

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.

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.

Dobruja Finewool ewes were mated to two rams of each of the Clun Forest, Hampshire, Suffolk and Oxford Down breeds as well as to rams of their own breed. The crossbred and purebred lambs were compared in terms of growth, food consumption and carcass attributes. The crossbred lambs of Hampshire, Suffolk and Oxford Down breeding were superior to the purebred control lambs on all counts while Clun Forest crossbred lambs were superior to controls only in carcass attributes and the time taken to reach slaughter weight but not in efficiency of conversion.

1. Twenty-four Southdown and 24 Welsh Mountain year-old female sheep, half on high plane and half on low plane nutrition, were closely shorn and given two short acute cold exposures (−20°C, 4 mph wind) in climate chambers. For two weeks before the first acute exposure half the sheep were kept at a moderately cold temperature (+8°C) and the remainder at a thermoneutral temperature (+30°C). During the next two weeks between acute exposures these temperatures were reversed for each group of sheep.

2. Resistance to body cooling during acute cold exposure was significantly greater after exposure to + 8°C. This was attributed to acclimatization. No further acclimatization resulted from acute cold exposure in addition to chronic moderate cold exposure.

3. Sheep which had been kept at +8°C cooled 33% more slowly than those which had been at + 30°C. High plane sheep cooled 34 % more slowly than low plane sheep. Southdowns cooled 32 % more slowly than Welsh sheep, but the Welsh sheep showed relatively greater acclimatization on low plane nutrition.

4. Compared with Scottish Blackface sheep given similar temperature treatment in an earlier experiment, the Southdowns and Welsh showed less initial cold resistance and less capacity for acclimatization.

From observations made over 3 years on a flock of Welsh Mountain sheep kept at 210 to 330m above sea level there was no indication that ewes especially sought shelter for lambing when wind speed was under 8 km/hr or the Kata cooling power was below 20 millical/cm2 per sec. When wind speed or cooling power rose, lambing sites chosen by the ewes were progressively more sheltered. Average wind speed and Kata cooling power at sheep height at lambing sites were about 14 km/hr and 35 millical/cm2 per sec.

Variability in wind speed and cooling power at an unsheltered site accounted for only 24% and 18% of the variability in these measures at the lambing sites, thus the lambing sites chosen depended to a considerable extent upon other factors, which are discussed.

The environment at lambing sites chosen by ewes cannot be taken as the optimum. No attempt was made to correlate lambing site environment with ewe or lamb performance.

Shorn Southdown and Welsh Mountain sheep on high or maintenance levels of nutrition were subjected to two acute (−20°C; 4 mph wind) cold exposures in climate chambers. Before and between exposures the sheep were kept in either a cold (+8°C) or a thermoneutral (+30°C) environment.

1. At +8°C, all the sheep shivered and showed sustained vasoconstriction and elevated heart rates.

2. At + 30°C, heart rates, skin temperatures on the extremities and muscular tone were all consistently higher in sheep which had previously been kept at +8°C.

3. During cooling, the onset of vasoconstriction and increase in heart rate were both delayed in sheep previously kept at + 8°C.

4. These effects (2, 3) were retained for at least 2 days but less than 12 days after the sheep returned to thermoneutrality. They decayed faster than the increased resistance to body cooling produced simultaneously in the same sheep (Sykes and Slee, 1969), since this was still detectable after 2 weeks.

5. Breed differences were mainly small.

6. It was concluded that acclimatization induced by chronic cold exposure was associated with a temporary increase in basal metabolic rate.

A series of animal feeding trials was designed to determine differences between grasses in dry-matter intake and animal live-weight gain, with a view to indicating better selection criteria for improving the feeding value of herbage.

Wide differences were demonstrated in feed intake and live-weight gain between single-variety grass feeds at similar levels of digestibility.

S.37 cocksfoot gave consistently good and S.51 timothy, consistently poor responses.

Supplementation of grass feeds with red clover frequently resulted in marked improvement in feed intake and animal performance.

1. The rates of eating silages and hay throughout a meal were recorded in eight cows consecutively using a special manger and an automatic recording apparatus. At each meal the rate of eating was highest in the first five or ten minutes and then fell gradually. These characteristics were observed both on silages and on hay and for all the experimental cows. The mean rates of eating hay, but not of silages, agreed with previous reports.

2. The highest rate of eating was slightly faster at the evening meal than at the morning meal, when cows received equal amounts of feeds twice each day. The rate of eating declined at much the same rate throughout each meal when the cows received from 2 to 5 meals daily.

3. When the cows were fed twice daily, the rate of eating throughout a meal was not affected by changing the interval between meals from 12 hr to 6 hr.

4. When cows were given large amounts of feed at any one time, three stages of rate of eating, fast, decreasing and slow, were recognized.

5. The quality of feed, individuality of cow and pregnancy evidently affected the rate of eating throughout a meal.