Eight adult ewes were fasted for 114 hr. During the last 48 hr. the heat emission of each sheep was measured by direct calorimetry and was found to be 35·2 kcal./kg.0·87/24 hr., that is, 973 kcal./24 hr. for a sheep of 45·4 kg. (100 lb.) live-weight. From this value it is estimated that the 100 lb. sheep would require daily 0·79 lb. digestible organic matter (DOM) from pasture herbage for maintenance.

In a second experiment, 49 adult sheep were kept indoors and fed on fresh herbage for a period of 72 days. Measurements were made of the mean daily DOM intake (D), mean live-weight (W) and mean daily weight gain (G) of each sheep. The regression of D on Wk and G, and the underlying or functional relationship between D, Wk and G were both estimated for k = 0·73 and k = 1·0. From the underlying relationships, the preferred equations, the maintenance requirement of a 100 lb. sheep was estimated to be 0·82 lb. DOM daily. This value and those calculated for other live-weights are approximately two-thirds of the corresponding values given in ‘Rations for Livestock’ (Evans, 1960).

The mean daily digestible organic matter intake (D) of each of 47 adult sheep during a grazing period of mean length 48 days was estimated by the chromium sesquioxide/faecal nitrogen technique. Mean live-weights (W) and mean daily weight gains (G) were also measured.

The regression of D on W and G, and the underlying or functional relationship between D, W and G were both estimated. From the underlying relationship, the preferred equation, the maintenance requirement of a 100 lb. sheep at pasture is estimated to be 1·02 lb. digestible organic matter daily. This value is 24% higher than the corresponding value for housed sheep obtained previously by us.

This result is compared with other estimates of the energy cost of grazing and it is concluded that further work is needed in order to define those circumstances which elevate the maintenance requirements of grazing animals.

1. Two experiments were conducted, the first during May, July and August, 1958, and the second during August 1960. The first experiment measured the intake and digestive efficiency of cattle fed on fresh cut herbage from low-and high-nitrogen manuring treatments with and without irrigation. The second experiment tested the effect of water added to fresh cut herbage on the intake of cattle.

2. Rainfall during the summer of the first experiment was high and irrigation had no effect on any of the criteria used.

3. Although the dry-matter content of the fresh herbage from the high nitrogen treatment was consistently lower than that from the low nitrogen treatment (16·6% compared with 19·7% on average when free of surface moisture) the dry-matter intake was the same at 1·97 lb. dry matter per 100 lb. live-weight, on both herbages.

4. The average digestibility of the high and low nitrogen treated herbage was 77·6% and 75·4%, the difference being significant. No scouring occurred. Digestibility was 78·9% in May, 76·1% in July and 74·5% in August (average of N levels).

5. Rain water carried on the leaf surface was shown to have no effect on dry-matter intake.

6. It is concluded that the dry-matter intake of cattle feeding on fresh herbage is unlikely to be restricted either by a high internal water content in the herbage or by rain water on the leaf surface.

1. The energy value of three hays cut at three stages of maturity was. measured by calorimetric methods and, in addition, the amounts of the hays consumed voluntarily by sheep were measured. Voluntary intake was alsa measured when 200, 500, 800 and 1,200 g. of pelleted concentrates were given.

2. The metabolisable energy values of the three hays measured at the-maintenance level were 2·45, 2·26 and 2·16 kcal./g. for cuts 1, 2 and 3-respectively (cut 1 being the earliest). The net energy values for fat production were 0·96, 0·85 and 0·68 kcal./g. respectively.

3. The apparent digestibility of the hays fell with increasing intake, but supplementation with concentrates increased their apparent digestibility.

4. The voluntary intake of the hays given as the sole food was 70, 62 and 57 g./kg. W0·73 for the three cuts, respectively. When concentrates were given in increasing amounts, the intake of cuts 2 and 3 increased to maxima of 65 g. and 64 g./kg. W0·73 respectively and thereafter declined. With cut 1, intake of hay declined even with the smallest intake of concentrates. Voluntary intake of the hays was maximal when the protein content of the whole ration was 8·5%.

5. When no supplement was given the digested energy per sheep per day supplied by cut 1 was 64% greater than that supplied by cut 3. When 800 g. concentrates were given, however, the ration including the early cut of hay provided only 2% more energy than that including the late cut.

6. It is shown that if hay were given as the sole food cut 3, which produced 57% more weight of crop per acre, would provide 38% more metabolisable energy/acre and 11% more net energy (starch equivalent)/acre than would cut 1. The late cut would also enable 92% more sheep to be kept feeding to maximal appetite on an acre of produce. However, the total live-weight gain per acre would be only 25% of that obtained with thefirstcut.

7. Comparable calculations have been made for the experiments in which concentrates were given. It is shown that here too optimal times of cutting can only be assessed in terms of estimates of animal production.

The results of a previous experiment suggested that a scale of feeding at about 60% of full-feed level from weaning onwards could result in a high incidence of infertility in gilts, but numbers were insufficient to confirm this. The present trial was carried out, therefore, with 18 Large White gilts per treatment fed to scales rising from either 1·4 lb. meal per day at 36 lb. live-weight to 5·0 lb. at 200 lb. live-weight, or from 1·9 lb. to 6·5 lb. over the same weight range. Average growth rate of the low-plane gilts was 76·5% of that of the medium-plane group but none of the low-plane gilts failed to conceive.

1. Seventeen Friesian steers, 25 Aberdeen-Angus crossbred steers and 33 Aberdeen-Angus crossbred heifers were fed on complete ground diets from 3 months of age until slaughter.

2. The average time taken from 84 days of age to reach a slaughter live-weight of 400 kg. was 334 days for Friesian steers and 356 days for the crossbred steers. The crossbred heifers took 354 days to reach a slaughter live-weight of 350 kg. Feed conversion efficiency was best for Friesian steers and poorest for crossbred heifers.

3. The ratio of hindquarter to forequarter in the carcass did not differ between breeds. There were marked differences in fat development, this being most pronounced in the crossbred heifers and least in the Friesian steers.

4. The commercial value of the carcasses was assessed by a score card based on measurements, analysis of the tenth rib cut and visual appraisal. There was no difference between the scores for crossbred steers and heifers but the mean score for the Friesians was considerably lower.

1. Some characteristics are described of 10 steer progeny of a Friesian bull which is known to have carried the factor for muscular hypertrophy.

2. On average these steers had a higher birth weight, lighter hide and liver, smaller feet and cannon bones, a lower percentage of fat and higher percentage of lean in the 10th rib joint, than the progeny of three other Friesian bulls reared at the same time and under the same conditions.

3. No one character was an adequate criterion for separating affected from normal progeny. It appears possible that the bull concerned was homozygous for the double muscling gene, and that all his progeny showed one or more symptoms of the condition.

1. Some characteristics are described of 10 steer progeny of a Friesian bull which is known to have carried the factor for muscular hypertrophy.

2. On average these steers had a higher birth weight, lighter hide and liver, smaller feet and cannon bones, a lower percentage of fat and higher percentage of lean in the 10th rib joint, than the progeny of three other Friesian bulls reared at the same time and under the same conditions.

3. No one character was an adequate criterion for separating affected from normal progeny. It appears possible that the bull concerned was homozygous for the double muscling gene, and that all his progeny showed one or more symptoms of the condition.

1. Records on lamb mortality from birth to marking at approximately 6 weeks are summarised for four seasons in one Cheviot and three Scottish Blackface flocks and discussed in relation to the breed, environmental and management differences existing on the three farms of Sourhope, Roxburghshire; Lephinmore, Argyllshire and Glensaugh, Kincardineshire.

2. The mortality rates in single-born lambs from three-year-old and older ewes, following hill lambings, were 12% and 6% respectively in the Cheviot and Blackface flocks at Sourhope and 14% in the Blackface flock at Lephinmore. In the Blackface flock at Glensaugh, the mortality rate following regular pre-lambing feeding and lambing on cultivated pastures was 5%.

3. There was considerably heavier mortality in twin-born lambs, and in single-born lambs from two-year-old ewes, notably as a result of increased loss subsequent to birth.

4. Among single-born lambs, more males were lost than females, the difference being between 1% and 8% according to the farm and being largely due to a greater frequency of difficult births among males.

5. Lambs with birth weights markedly heavier or lighter than average had a higher percentage of mortality.

6. An abnormal incidence of loss from difficult birth in a Cheviot sub-flock in 1957 is described.

The variation and covariation of 12 linear body measurements within 60 pairs of monozygotic twin heifers is analysed in terms of a twin's mean size over a two-year period.

Possibly all the covariation, and two thirds, on average, of the variation can be accounted for by a single factor common to all the measurements.

Interpretation of this factor shows that a twin is a more or less proportional replicate of its identical co-twin. This proportionality, however, is somewhat distorted because of relatively greater differences in the later maturing body parts.

Finally it is shown that the predominant differences in both size and shape can simultaneously be described as twin lagging behind identical co-twin by 0±11·8 days' growth.

An analysis has been made of still-births and difficulties at parturition in a dairy herd in which purebreds and crossbreds of Friesian, Ayrshire and Jersey origin were kept. There were 2,049 calvings including 28 involving twins.

Purebred heifer dams produced 14·7% dead purebred calves (mostly Friesian and Jersey) and 6·4% dead crossbred calves (P < 0·05). For older dams the corresponding values were 2·4% and 3·6% (P > 0·05). Losses were smaller with crossbred dams. Crossbred heifer dams (two-breed crosses) with 6·5% dead calves exceeded older crossbreds with 1·9% dead calves. Three-breed crossbred dams gave similar results (8·2% and 1·2%). An intermediate size of cow of second or later parity was associated with the lowest mortality.

Friesian and Hereford sires, the calves by which were heavier than those by Ayrshire and Jersey sires, were associated with greater losses than were the latter but this applies to heifer dams and not to the same extent if at all, to older dams.

Of 52 parturitions described as difficult, 31 resulted in dead calves. Malpresentation accounted for 32 cases; the majority of these were ‘hindfeet first’. Friesian and Hereford bulls sired a higher proportion of the calves involved in difficult cases than Ayrshire and Jersey sires.

1. Thirty-six Large White fattening pigs, eight to nine weeks old at the beginning of the trial, were used to study the effects of cubing pig rations.

2. There were three treatments, meal, cubes and cubes reground to meal.

3. Pigs fed on cubes had significantly higher growth rates (by 0·09 ± 0·03 lb. per day or 7·1%) than those fed on meal.

4. Food conversion was significantly lower, by 0·18 ± 0·05 lb. feed per pound gain, for cube-fed pigs. The saving in feed was 5·1% for the complete fattening period, this difference being statistically significant (P < 0·001).

5. No significant differences between treatments were recorded for any of the carcass measurements.

6. Meal-fed pigs had significantly lower dressing-out percentages than those fed cubes.

7. There were no significant differences in performance between pigs fed on cubes and ground cubes.

A study has been made of the relative accuracy of twelve linear body measurements of dairy cattle. The results of several repeatability trials are presented together with estimates of observer error derived from the routine measuring of identical twins. Various aspects of precision of measurement have been analysed. The accuracy found from any one trial can rarely be used as a reliable estimate of the accuracy of measuring in any subsequent experiment.

The importance of observer error in identical twin studies has been assessed. It was found that from 10% to 70% of the total variation within pairs of uniformly treated identical twins could be due to measuring error. It was therefore concluded that in such studies, where observer error is a fairly large part of the total variation, a single routine repetition of every measurement would be advisable in long term experiments and several in the case of short term experiments with a small number of animals.

Measurements have been ranked for relative accuracy and the ranking was found to be broadly similar on several different criteria: (a) relative to the variation within pairs of uniformly treated identical twins, (b) relative to the total variation in a population of unrelated animals and (c) relative to the mean size of the body part. The choice of measurements on the basis of relative accuracy is discussed.