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.

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.

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.

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.

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.

1. The voluntary dry-matter intake, water intake and rate of live-weight gain of indigenous, exotic and crossbred cattle on low- and medium-roughage diets have been compared under similar conditions of management.

2. At similar live weights and on similar diets exotic cattle usually have a higher food intake than indigenous animals.

3. When roughage was freely available the voluntary dry-matter intake of both types of cattle increased.

4. Water intake was closely related to dry-matter intake and varied with the nature of the diet. The ratio of water to dry-matter intake was not affected by live weight and varied only slightly between the different types of cattle.

5. Exotic cattle were generally more efficient than indigenous cattle of comparable live weight in converting food into live-weight gain; crossbred animals were intermediate. It is suggested that this largely reflects their higher intake of food relative to their maintenance requirement.

6. One group of indigenous animals that were initially mature but under weight gained weight as quickly, and converted their food as efficiently, as did exotic animals.

1. Two experiments are described in which groups of 12 autumn-born calves were strip-grazed at different intensities. In Experiment 1 (1966), ‘standard’ and ‘high’ grazing intensities were compared. In Experiment 2 (1967), ‘standard’ and ‘low’ intensities were compared. In both experiments the same meadow fescue—ryegrass ley provided 0·24 ha per head for grazing and conservation; herbage surplus to grazing requirements was conserved as silage.

2. The grazing season was divided into three parts according to the type of grazing, and estimates were made of daily herbage allowances, herbage quality, efficiency of herbage utilization and the live-weight gain of the cattle.

3. Grazing intensity was regulated by controlling daily herbage allowances by strip-grazing. Within grazing seasons, differences in grazing intensity had little effect on the digestibility of the herbage dry matter on offer. Dead herbage accumulation was low (10%) in the early and late parts of the season, but rose to 25% in mid-season.

4. The efficiency of herbage utilization was estimated in three ways: from sample cuts of herbage on offer and refused; from measurements of herbage intake; and from feeding standards for maintenance and gain. Efficiency was highest for the ‘high’ group of Experiment 1 and lowest for the ‘low’ group of Experiment 2. The validity of efficiency estimates is discussed in relation to measurements of pasture yield, herbage intake and the assessment of the nutrient requirements of growing cattle.

5. Live-weight gain over the whole season was 0·59 and 0·89 kg/head per day for the ‘high’ and ‘standard’ groups of Experiment 1, respectively. In Experiment 2, the ‘low’ and ‘standard’ groups gained weight at 0·95 and 0·84 kg/head per day, respectively.

1. Two experiments are described in which the consequences of variation in grazing intensity were studied during the subsequent period of winter feeding from 12 months of age to slaughter at 18 months. The cattle were loose-housed and fed on silage ad libitum, together with allowances of rolled barley. Individual organic-matter intake was measured periodically, chromic oxide being used to estimate faecal output. The digestibility of the diet was estimated with stall-fed steers.

2. Groups of 12 steers were grazed at different intensities over five-month periods, so that those grazed at the higher intensity were 38 and 16 kg lighter at the start of the 1966 and 1967 winter feeding periods respectively. They did not make significant compensatory growth over the subsequent winter feeding periods, although they had a significantly higher intake of feed organic matter per 100 kg live weight than the control steers.

3. With supplements of 3·63 and 1·81 kg/head per day of barley, live-weight gains were 0·77 and 0·50 kg/head per dayin the first half of the winter, but in the second half, when barley allowances were raised to 4.54 and 2·72 kg/head per day, both groups gained weight at the same rate (0·94 kg/head per day).

4. The higher level of barley feeding reduced silage intake by 0·4 kg OM/kg barley OM at all stages of the winter, and the additional 306 kg of barley was associated with the production of 21 kg more carcass weight at slaughter. This higher yield of carcass was reflected in a higher weight of fat in a three-rib sample joint.

1. Performance tests were made on 221 bulls of eight breeds or crosses from 90 days of age (weaning) up to 400 kg live weight. Feeding was in individual pens on a high-energy complete diet.

2. Pre-weaning gain was not significantly related to gain on test (r = 0·11) nor was 90-day weight to gain on test (r = 0·26) or feed conversion (r = −0·15). Weight for age at 200 and 300 kg was highly correlated with final weight for age (r = 0·72 and 0·89 respectively) while gain on test and final weight for age had a pooled correlation (across breeds) of r = 0·95. The correlation of feed conversion with gain on test was highly significant in all breeds. The range of values (−0·72 to −0·86) is higher than any previously reported estimates possibly due to an absence of initial weight effects, a reduction in the proportion of feed used for maintainenance and the use of complete diets.

3. It is suggested that with this testing system at least 50% of bulls could be culled at 300 kg without affecting selection of the best 20% of all bulls starting the test.

On a fattening diet in which final molasses supplied from 68 to 76% of the metabolizable energy and napier grass some 10%, the treatments in a 2 × 2 × 3 factorial design were breed (Brahman or Brown Swiss × Brahman), source of supplementary protein (fish meal or poultry waste) and protein level (low, medium or high—replacing urea). Mean daily gains to 404 kg live weight were better for the crossbreds (0·89 compared with 0·77 kg), as was conversion rate in terms of Meal ME per kg gain (25·6 compared with 29·5); fish meal improved gains by 44% and conversion rate by 39% as compared with poultry waste when the two supplements were fed at levels designed to equate N intakes from this source. The superiority of the crossbreds was only apparent on the fish meal diets where they averaged 1·19 compared with 0·94 kg/day for the Brahmans. Daily N × 6·25 intakes decreased from 3·8 g/kg live weight on the low level of poultry waste to 2·9 on the high level due to low palatability of this material. On this treatment (poultry waste), daily gain (kg) was significantly related (b = 0·119±0·031; P<0·01) to N×6·25 intake (g) per unit live weight (kg). Commercial half carcass dissection showed the crossbreds to have significantly more edible meat, more bone and less e×cess fat than Brahmans. Protein source had no effect on carcass composition.

In light-proofed buildings experiments were conducted with six groups each of ten Clun Forest ewes to determine whether the onset of anoestrus was affected by the absolute size of increase in the case of an abrupt increase in daylength, and by the rate of increase in the case of a given total increase in daylength. The mean number of days from the onset of the light treatments to the cessation of oestrus (the reaction interval) for ewes receiving gradual increases in daylength of 3·5, 7·2 or 10·9 min per day from 23 December were 79·8, 84·1 and 75·7 days respectively. The reaction interval for ewes receiving abrupt increases in daylength of 3·75, 7·75 or 11·75 hr on 23 December were 86·3, 76·5 and 61·5 days respectively. A control group of ten ewes at pasture on natural daylength had a reaction interval of 93·6 days.

The results show that increasing daylength largely controls the mean date of onset of aneostrus in Clun Forest ewes. The greater the increase in daylength the sooner the onset of anoestrus occurs.

The observations on vaginal smears indicate that photoperiodic changes, whilst affecting the oestrous status of the ewe, may have no effect on ovulation.

A crossbreeding trial was conducted in the hot wet tropical zone of Ceylon at Karagoda-Uyangoda. Sinhala cows were mated to Jersey, Friesian and Sinhala bulls. A few reciprocal matings were done with the Jersey breed.

The milk yields of the Friesian crosses were higher than those of the corresponding Jersey crosses which were higher than those of the Sinhala. The ½ Sinhala ½ Friesian also had a longer lactation and larger body size than the Jersey cross or purebred Sinhala. A decline of about one-third of the milk yield of the F1 was evident in the F2 generation.

The liability to perinatal mortality increased from the F1 generation calves to F3 calves.

1. Experiments have been performed to determine the thermal effects, on pigs, of the ingestion of whey at various temperatures while housed at various air temperatures.

2. Measurements of carotid artery and rectal temperatures showed that a general cooling of deep-body tissues occurred after the ingestion of cool whey.

3. Measurements of rectal and skin temperatures, and observations of respiratory rate and shivering activity, indicated that thermo-regulatory responses were induced by the ingestion of cool whey; the nature of the responses was dependent on the air temperature.

4. The results indicate that the temperature of liquid food offered to animals is a significant parameter in their climatic environment.

1. Measurements have been made of sensible heat flow, body temperature and some hair coat characteristics, at 10 different air temperatures, on each of 24 Friesian and Jersey calves aged 12 and 76 days.

2. Minimum values for thermal conductance of the trunk tissues were 29·5 and 37·3 kcal/m2.hr per °C for the 12-day-old Friesian and Jersey calves respectively; corresponding values for the 76-day-old calves were 22·5 and 19·9 kcal/m2.hr per °C.

3. Weight of hair per m2 surface area was greater for Friesian calves and for younger calves; Friesian calves had longer hair and deeper coats. Coat depth increased at low temperatures in all calves.

4. The air temperatures at which the ears became vasoconstricted were 18·8 and 21·8°C for the 12-day-old Friesian and Jersey calves respectively; the corresponding values for the 76-day-old calves were 10·1 and 17·8°C. Vasoconstriction occurred in the back legs at a lower air temperature than in the ears or on the trunk surface.

5. The intake of dry matter as fresh grass was 1·15 kg/day for Friesians and 0·72 kg/day for Jerseys, aged 76 days; the Friesians weighed 74 kg and the Jerseys 59 kg at this age.

The effect of introducing a solution of fatty acids (consisting mainly of ammonium acetate) into the drinking water of Jersey and Friesian cows on the yield and composition of milk was investigated. In short-term experiments there were small increases in milk yield and in the yield of fat in Jersey cows receiving either a high-roughage or a high-concentrate diet and in Friesian cows receiving a high-concentrate diet. Friesian cows receiving a high-roughage diet gave no response. In a long-term experiment extending over 16 weeks of lactation with Jersey cows receiving a high-concentrate diet, there was no immediate effect on milk yield but a greater persistency and overall the yield of fat was increased by 5·9%.

Inclusion of ammonia salts in the drinking water caused increases in the ammonia contents of rumen liquor and of blood but there was little effect on rumen pH or the volatile fatty acids of rumen liquor.

Experiments were carried out with Clun Forest ewes to determine the effect on the onset of oestrus of applying the same abrupt decrease in daylength at two different times of the year. An abrupt decrease in daylength of 3·75 hr was applied to the ewes on 1 July 1968 and on 24 April 1969. The mean number of days from the commencement of the light treatment to the onset of oestrous activity was 59·5 and 87·0 days, respectively. It is concluded that the time of year at which the light treatments were applied, or the previous light treatment of the Clun Forest ewes, or both, significantly (P<0·001) affected the date of onset of oestrus.

On a hill farm, 376 Scottish Blackface ewes with all permanent incisor teeth present (whole mouth) at 53 months of age were compared with 118 ewes having one or more of these teeth missing (broken mouth). By 46 months, ewes becoming or already broken-mouthed were significantly lighter in weight and although at their third lambing they gave birth to the same number and weights of lambs as whole-mouthed ewes, their twin lambs were significantly lighter in weight from about three weeks of age onward. At their fourth lambing, broken-mouthed ewes produced and reared significantly fewer lambs and of lighter weight than their whole-mouthed contemporaries. Grazing of turnips increased the incidence of ewes with broken mouths.

Studies of the social behaviour of a hill flock of sheep confirmed the existence of home range groups with each group having a definable territory. The groupings were not broken by a period of individual penning of the sheep.

The nutritional value of dried poultry excreta was investigated by determining the apparent digestibility of dry matter, organic matter, nitrogen, energy and copper in five diets containing 0 to 100% of this feed. Dried poultry excreta supplied 20·21% apparently digestible crude protein and approximately 1·57 or 1·74 Mcal of metabolizable energy per kg dry matter.

The copper in dried poultry excreta was found to be less digestible than the copper in barley. It is concluded that, as far as copper levels are concerned, dried poultry excreta are safe for ruminants, and are a source ofcheap protein. More detailed work is needed to determine the metabolizable energy of the material accurately.

In two trials 20 female pigs were given diets containing up to 50 p.p.m. ‘Bitrex’ during their growth from 100 to 200 lb live weight. Voluntary feed intake, daily live-weight gain and carcass quality were not influenced significantly.