1. Twenty newborn Ayrshire male calves were used in a comparison of milk substitute diets containing two different margarine fats. The liquid diets were offered in two feeds daily ad libitum and the calves were slaughtered at 118 kg live weight.

2. The two diets consisted of reconstituted spray-dried skim milk powder containing 200 g margarine fat/kg. One fat contained coconut and palm oils (CP) and the other coconut, palm and groundnut oils (CPG). The essential fatty acid content of margarine CP was less than half that of margarine CPG.

3. The incidence of diarrhoea and of a high rectal temperature, and the severity of lung lesions tended to be higher, the incidence of nasal discharge was higher and daily dry-matter intake and liveweight gain were lower for calves given margarine CPG.

4. Digestibility and balance trials were made at 1, 4 and 10 weeks of age. Nitrogen balance and apparent digestibility of the fat and other nutrients were not affected by the source of margarine, but the digestibility of dry matter and of fat was highest at 4 weeks of age, and of protein was lowest at 1 week of age. Apparent absorption of ash and calcium declined with age and absolute calcium retention was highest at 4 weeks. Total plasma lipids at 13 weeks of age did not differ between treatments.

5. Age at slaughter was greater for calves given margarine CPG but dressed-carcass weight, killing-out percentage, perirenal fat deposition and kidney weight did not differ between treatments. Skin weight tended to be lower for the calves given margarine CPG. 6. It is suggested that the apparent increased susceptibility to infection of calves given margarine CPG was associated with its higher unsaturated fatty acid content.

1. Fifty-one Jersey, Ayrshire and British Friesian male calves were reared from birth to veal weights on one of three liquid diets.

2. Two ultra-high fat milk powders containing 680 g fat, either beef tallow (T) or a mixture of coconut oil and beef tallow (CT)/kg dry matter were prepared and mixed with liquid skim milk (35 g powder/kg) to give diets TLS and CTLS, containing 200 g fat/kg dry matter. A third diet consisted of reconstituted spray-dried skim milk powder containing 200 g margarine fat/kg (MDS).

3. The incidence of diarrhoea and of nasal discharge for all breeds, and of a high rectal temperature for the Ayrshire breed was greatest for calves given diet MDS and lowest for those given diet TLS. The incidence of lung lesions at slaughter was 100, 72 and 57% for the Jersey, Friesian and Ayrshire breeds respectively. Severity of lung lesions was lowest for calves given diet TLS.

4. Dry-matter intake and live-weight gain, especially for the Ayrshire breed, were greater for calves given diets containing liquid skim milk and the ultra-high fat powders (TLS and CTLS).

5. Fat digestibility was lowest on diet TLS. Protein digestibility increased with age. Digestibility of dry matter and lactose, and absorption of ash and calcium decreased with age. Calcium and N retention were lowest on diet MDS.

6. Killing-out percentage was highest for the Friesian and lowest for the Jersey breed. Perirenal fat deposition was highest for the Jersey and lowest for the Ayrshire breed. Skin weight/kg0·73 was higher for the Ayrshire calves than for the other two breeds.

1. British Friesian male calves were offered, in two experiments, either chopped, or ground and pelleted dried grass diets to appetite. In one experiment the pelleted diet was also given in restricted quantities. The calves were slaughtered without being fasted, 6 to 9 weeks after weaning, and detailed measurements were made of the weights and volumes of the sections of the alimentary tract and its contents, and of other abdominal organs.

2. Grinding and pelleting the diet reduced mean retention time by approximately 50% and digestibility by 6 to 8 units, and increased dry-matter intake in the two experiments by 55 or 32% respectively, and growth rate by 53 and 69% respectively.

3. The ground and pelleted diets resulted in a smaller quantity of fluid digesta in the rumen, and a much greater quantity in the abomasum and small intestine.

4. There were smaller differences between diets in the quantity of digesta in the combined caecum and colon, or in the total volume of the organs of the abdomen, than in the amount of digesta in the rumen. It is suggested that further critical studies are required upon the importance of the contents of the alimentary tract, or of the abdomen as a whole, in the control of voluntary food intake in ruminants.

Four trials with 24 and 38 British Friesian male calves, 39 male Damascus kids and 36 lactating Damascus goats were conducted over a period of 9 months, 6·5 months, 3 months and 12 weeks respectively to study the effects of carob pod meal on growth rate or milk yield. Carob pod meal was used to replace barley at rates from 0 to 30% of the diet. Urea was added to the diets of some of the treatments as a source of supplementary nitrogen.

The final weights and average daily gains of the calves and kids fed on carob pod meal were as good as those of the controls but their feed intakes and feed conversion ratios were higher. The differences in fat-corrected milk between the goats fed on carob pod meal and the controls were not significant. The results showed that carob pod meal constituting up to 30% of the diet had no depressing effects on the growth rate of calves and kids or on the performance of dairy goats, and that the calves and kids could compensate for the lower energy content of carob pod meal by increasing their feed intake.

The effects of two levels of roughage (18 or 40%), of DES implantation (36 mg, twice), and of the addition of adjoining dirt yards to pens with concrete slatted floors, on the behaviour of intact male calves, were examined in a 2 x 2 x 2 factorial experiment. Observations were carried out on four days, every 15 min for 24 hr. Activities recorded were: standing, lying, eating, drinking, ruminating, jumping and idling.

Animals on the high roughage diet spent 26% more time eating, 5% more time drinking, and 19% more time ruminating, than those on the low roughage diet.

Most of the rumination was performed while the animals were lying down. Animals allowed yards adjoining their pens spent 20% less time ruminating and 13% more time jumping than animals confined to pens alone. Those allowed the yard preferred to stand there and to lie down in the pen. The yards were used more on a cool day than on a hot day.

1. The digestibility of dry barley and acid-treated moist barley was studied with eight Friesian steers in two consecutive trials each of a duplicated, 2x2 factorial design. In the first trial the diet consisted of either dry or moist (30%) acid-treated barley in the rolled or whole form together with chopped hay; in the second trial rolled or whole, moist (24%) acid-treated barley was given with either chopped hay or silage.

2. No significant difference between the diets in dry-matter intake was observed in the first trial, but in the second trial there was a significantly greater (P< 0·001) intake of dry matter with the hay than with the silage diets.

3. For diets containing either of the moist barleys the digestibility of crude protein was higher when the grain was rolled than when it was whole, the differences being significant (P<0·05) for diets with the 24%-moisture barley. Dry-matter digestibility also was higher for diets containing rolled rather than whole, moist (24%) barley, the difference being significant (P < 0·05) for diets based on silage.

4. Digestibility of starch was significantly greater (P<0·05) when acid-treated moist (24 or 30%) barley was given in the rolled rather than the whole form. Differences in starch digestibility between whole and rolled dry barley were not significant.

5. For all diets the digestibility of crude fibre was greater when the barley was whole than when it was rolled, the difference being significant (P < 0·05) for diets containing hay.

Two field trials were conducted to evaluate oestrus synchronization under farm conditions and to determine if increased sperm numbers per insemination would enhance fertility at the first synchronized oestrus. One hundred and seventy-seven previously unmated British Friesian females in 6 dairy herds and 236 suckler cows in 9 beef herds were used. Treated animals received 1·0 mg melengestrol acetate (MGA) daily for 14 days. Treated and control animals were inseminated with either 15 or 60 million sperm per first insemination.

Oestrus was synchronized in 94% of the treated dairy heifers and 66% of the treated suckler cows. Oestrus detection by herdsmen appeared to be much less precise in suckler herds than in the dairy herds.

First inseminations were given during a 21-day breeding period (commencing at withdrawal of MGA) to 97% of treated and 79% of control dairy heifers (P<0·01), and to 77% of the treated and 69% of the control suckler cows (P>0·05). On an average, first inseminations were given 10 days earlier to treated heifers and 7 days earlier to treated suckler cows than to their control counterparts. The 45-day non-return rate to first inseminations was 81% for control and 41% for treated dairy heifers (P< 0·001) and 69% for control and 46% for treated suckler cows (P>0·05).

Oestrus-synchronized animals required significantly more services than control animals during a 30-day breeding period. However, there was no difference between treated and control animals in the non-return rate to one or more services given during the prescribed 30-day breeding period.

Insemination with 15 or 60 million live sperm had no effect on the non-return rate of treated or control animals.

The intakes of concentrates and hay by individuals in three groups of ewes were estimated at three-weekly intervals in late pregnancy from faecal output; chromic oxide was incorporated as a marker in the concentrates. The groups were: (1) 16 mature ewes, (2) 16 2-year-old ewes, (3) eight mature and eight 2-year-old ewes. A constant daily hay allowance of 734 g dry matter (DM)/sheep was given but the concentrate was increased from an equivalent of 96 g DM/sheep at the beginning of the experiment to 435 g at the end. Individual concentrate intakes were most variable when the group allowance was small (CV over 50% in the mixed group) but variation decreased when amounts of concentrates were increased to contribute up to 47% of the total digestible DM intake. The CV for the total digestible DM intake ranged from 13 to 24%.

The younger sheep were at no disadvantage when penned with mature ewes. Intakes by individual ewes were compared with their calculated requirements and several twin-bearing ewes were shown to have a substantial energy deficit which was confirmed by their higher plasma ketone concentrations.

A major practical difficulty in group-feeding pregnant ewes is to ensure that the ewes with the highest foetal burden are adequately fed.

Twenty-seven groups of Finnish Landrace × Dorset Horn lambs, each of two males and two females, were offered daily quantities of 180, 248 or 343 g milk substitute dry matter (DM) for 21, 29 or 40 days. The environmental temperature was 18°C during the first 21 days of rearing, and concentrate pellets and clean water were always available. From 22 to 48 days of age the lambs were offered 150 g of hay per week.

For lambs offered 180 g milk substitute DM, increasing the number of days before weaning increased the daily live-weight gain over the 47-day experimental period. For daily allowances of 248 and 343 g of milk substitute, greater gains were effected only by delaying weaning from 21 to 29 days.

Increasing the daily allowance of milk substitute DM had little effect on the daily gain of lambs weaned after 21 days but increased gain by lambs weaned at 29 days. For lambs weaned after 40 days growth rate was increased only by the first increment of milk substitute DM. Intake of solid food began when the lambs were 3 weeks old and total intake of concentrates was inversely related to total quantity of milk substitute DM consumed and in general was less when weaning was later.

The overall efficiency of conversion of total DM consumed to live weight was positively related to total milk substitute DM consumed and tended to be greatest when weaning was later. A daily allowance of 180 g milk substitute DM for 21 days gave the lowest food cost per unit of live-weight gain.

The incidence of navel sucking is discussed.

The effects of selection for increased and decreased body weight in mice at 5 and at 10 weeks of age on the weight and mean fibre diameter and number of seven different muscles were studied by dissecting and histologically examining animals from large, small and unselected control lines. The purpose was to learn how selection for body size affects muscle weight and its components. Selection for increased body weight significantly increased the weight of m. biceps brachii, m. tibialis anterior, m. pectoralis major, m. brachio-radialis, m. soleus, m. rectus femoris and m. psoas major. These increases in muscle weight reflected increases in both fibre diameter and number although there were a few exceptions. Selection for low body weight produced decreases in the weight of all muscles. These reflected significant reductions in mean fibre diameter and, in most cases, fibre number. Significant estimates of heterosis in mean fibre diameter were obtained in m. biceps brachii and m. tibialis anterior from crosses between the Large and Small lines selected at 5 weeks and also between the lines selected at 10 weeks of age, respectively.

Regression equations derived from Jersey calves fed on either chopped or ground and pelleted dried grass indicated that the volume of the organs of the abdomen or abdomen plus thorax could be predicted from simple external body measurements. The prediction equations did not differ significantly between diets. It is suggested that this measurement may be of importance in studies on the voluntary food intake of ruminants.

A molassed sugar beet product with 32% crude protein and containing added urea (8%), dicalcium phosphate, trace elements and vitamins was evaluated in two experiments as a protein source for intensively-fed 100 kg British Friesian steers. Comparison was made with an equal amount of crude protein supplied as a mixture of decorticated groundnut and cottonseed meals.

Both forms of supplementation equally and significantly increased live-weight gains and improved food conversion ratios compared with those recorded when the basal diet consisted of barley with no protein supplement.

1. The effects of 0·9 to 1·0 kg molassed sugar beet pulp cubes, supplemented with minerals and vitamins and with either 0, 3·0 and 7·8% urea, on the voluntary intake of oat straw (either 2·0 or 3·0% crude protein) were measured in two experiments with 250 to 300 kg British Friesian steers.

2. Straw intake was increased by a maximum of about 20% when a total of about 165 g crude protein was supplied by the urea-containing sugar beet products.

3. In one digestibility trial conducted with 385 kg steers, the inclusion in sugar beet pulp of urea equivalent to 89 g and 169 g crude protein/day comparably and significantly increased the digestibility of dry matter and crude fibre.

Complete C, N and energy balances were carried out on two mature sheep receiving a basal diet of pelleted hay plus continuous intraruminal infusions of either water or 400 kcal/day of propionic acid, butyric acid or a mixture of acetic acid and sodium acetate, for periods of 1 to 5 weeks. The efficiency of utilization for maintenance plus fattening of the basal diet and the basal diet supplemented with acetate, propionate or butyrate was 20·7 ± 1·0%, 28·3 ± 1·5%, 30·2 ± 0·5% and 31·3 ± 0·2%, respectively. The calculated efficiency of utilization for fattening (kf) of the infused energy sources was 69·9 ± 8·4%, 84·0 ± 3·4% and 86·0±2·0% for acetate, propionate and butyrate, respectively. In most instances kf did not vary with the length of the period of infusion but in one sheep there was an adverse response to the infusion of the acetate mixture, and during the first week of infusion kt was only 29·3%. During the third and fifth weeks of the infusion the corresponding values were 76±3% and 72±5%.

A comparative study was made of the utilization of hay (Lasiurus sindicus) by Marwari and Russian Merino × Marwari male sheep. Intakes of dry matter and crude protein and digestibility of dry matter were similar for both groups but the digestibility of crude protein was higher for the purebred Marwari sheep. Within the purebred animals, digestibility of crude protein was higher in those that gave a consistently low fleece yield.