1. A 2×2×2 factorial experiment was carried out with 8 blocks of 8 early-weaned Friesian male calves on the 8 treatment combinations of the following factors: (A) groundnut meal versus white-fish meal as the major protein source; (B) presence versus absence of antibiotic and (C) restricted versus ad lib. feeding. The experiment was conducted over the live-weight range 55–90 kg.

2. The inclusion of fish meal rather than groundnut meal in the diet resulted in highly significant increases in both rate of gain and feed conversion efficiency (P < 0·001). This effect was most apparent at the higher level of feed intake.

3. The addition of antibiotic to the diet increased rate of gain (P < 0·001) and improved feed conversion ratio (P <0·01). Feed intake was increased slightly but non-significantly (P <0.1) on the ad lib. feeding level as a result of antibiotic supplementation.

4. Feed conversion ratio was lower and feed intake and rate of gain were higher on ad lib. than on restricted feed (P < 0·001 in each instance).

5. There was a significant (P < 0·05) level of feeding × antibiotic interaction, indicating that the difference between restricted and ad lib. feeding was greater in the presence than in the absence of antibiotic. No other significant interactions were observed.

6. The use of fish meal in preference to groundnut meal is shown to be justified on economic grounds.

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).

1. The intakes of herbage organic matter (OM) and digestible organic matter (DOM) by twenty dairy cows were measured during two periods of strip grazing on one pasture, in spring and late summer of the same year.

2. Results from the first 5-day measurement period in the spring suggested that intakes at this time were restricted primarily because the cows had difficulty in gathering the short herbage. Measurements on ten of the cows continued during a further 5 weeks while the digestibility of the OM of grazed herbage declined from about 80 to 68%. There was a fall of about 20% in DOM intake by the cows during this period; one-quarter of the fall could be ascribed to a reduction in OM intake and the remainder to the decline in digestibility as such.

3. Intakes were measured during two weeks in late summer and were compared with those measured during two weeks in the spring when the digestibility of the grazed herbage was similar. Intakes of DOM expressed as lb./lb. live-weight0·73 were the lower by about 10% in the late summer, or by from 10 to 20% in terms of DOM available for production when allowance had been made for maintenance requirements. This finding is discussed in relation to practical experience of the feeding value of autumn grass.

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. Nitrogen balance studies have been conducted on 16 early-weaned calves given four diets containing groundnut meal or herring meal, the protein of which had been rendered soluble or insoluble by different methods processing.

2. There were highly significant differences in nitrogen retention between ‘soluble’ and ‘insoluble’ herring meals but no differences between ‘soluble’ ‘insoluble’ groundnut meals.

3. ‘Insoluble’ herring meal gave retention values which tended to be higher (significantly so, in one experiment), and ‘soluble’ herring meal gave values significantly lower, than either type of groundnut meal. Mean daily live-weight gains tended to follow the same pattern.

4. Blood-urea concentration was significantly lower on the diets containing herring meal than on those containing groundnut meal but within each type meal did not differ according to solubility.

5. These results are discussed in the light of in vitro studies on the effect of pH on protein solubility.

6. It is concluded that solubility is of minor importance in groundnut meals but of major importance in fish meals when these are included in early weaning diets for calves.

7. Under conditions of low or ‘potentially low’ solubility the amino acid content of the protein source appears to be of considerable significance.

Transfers were made to recipient ewes of sheep eggs stored in serum at 37° C. for up to 5 hr. (fresh eggs), in serum at room temperature for 24 to 48 hr. (stored eggs), or in Whitten's modified Krebs-Ringer-bicarbonate medium for 24 to 48 hr. (cultured eggs). The success of transfer was judged from the presence of embryos at autopsy 25–30 days after transfer.

Fifteen of 42 fresh eggs, 11 of 23 stored eggs and 3 of 15 cultured eggs were found to have developed after transfer.

The findings are discussed.

1. Rumen-ammonia concentration, pH of rumen liquor and blood-urea concentration have been measured at intervals after feeding in six calves given diets containing ‘soluble’ groundnut meal, ‘soluble’ herring meal or ‘insoluble’ herring meal as the major protein source.

2. There were no significant differences between diets in any of the measurements examined. A difference approaching significance was, however, observed between ‘soluble’ herring meal and the other diets in the direction and extent of the change in rumen-ammonia concentration during the first hour after feeding.

3. On all diets, pH of rumen liquor fell to a value in the region of 5·5 immediately after feeding and increased gradually to around 6·5 during the following 8 hr. Rumen-ammonia concentrations were at all times very low.

4. There was no significant residual correlation between changes in blood-urea concentration and the corresponding changes in rumen-ammonia concentration.

5. Rumen-ammonia concentration increased markedly on the ‘soluble’ herring meal diet when the nitrogen intake of the animals was increased by 50%; under similar conditions, only slight increases in this measurement were observed on the other diets.

6. Thesefindingsare discussed in relation to the efficiency of utilisation of dietary nitrogen.

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.

Two groups of twelve-week-old Friesian steer calves were self-fed to a slaughter weight of 400 kg. on diets composed solely of either 85% rolled barley or ground maize and 15% of a supplement providing additionalprotein, calcium, phosphorus, iron, copper, cobalt, salt and vitamin A and vitamin D.

There were no health problems on the barley diet, but five of the 15 cattle given maize died from bloat.

Surviving animals on the maize diet took 344 days to reach a carcass weight of 231 kg.; comparable data for the barley-fed cattle were 362 days and 222 kg. The tenth rib cuts from the carcasses of cattle given maize contained significantly more fat and less water and ash than comparable cuts from the barley animals. Feed conversion ratio on the barley diet was 4·76.

A comparison between the Friesian steers in the present trials and others given a lower energy diet containing ground roughage showed that with increasing concentration of the ration there was an increase in rate of gain, killing-out percentage and content of ether extract in the tenth rib cut.

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.

Records of cows each milked in two different herds have been used to estimate a component of variance due to cows that is free of variation arising from cow-by-herd interaction effects. By making use of a prior estimate of within-herd repeatability the variance component due to cow-by-herd interaction effects was estimated, and found to represent 35% of the total within-herd variance of butterfat yields and 9% of that of butterfat percentage records.

Three experiments were carried out to evaluate zinc bacitracin as compared with penicillin, as a feed supplement for bacon pigs. The first experiment compared pig performance on a control diet with performance on the control diet supplemented with penicillin, 5 g./ton, or with zinc bacitracin, 10 g./ton. Experiment 2 compared the control diet with penicillin at 10 g./ton and zinc bacitracin at 10 g./ton with pigs housed in a different piggery. Experiment 3 compared the control diet with penicillin at 10 g./ton and zinc bacitracin at two levels, 10 g./ton and 5 g./ton. In none of the experiments was there any significant response to penicillin in terms of rate of gain, feed conversion efficiency or carcass composition. In the first experiment there was a small but significant improvement in rate of gain up to 100 lb. live-weight and for the whole experimental period by the pigs receiving 10 g./ton of zinc bacitracin. There was no significant response in feed conversion efficiency or carcass measurements. In the other two experiments there was no response to zinc bacitracin. The implications of the results are discussed.

Data from the Danish progeny test reports were used in an attempt to measure the genetic change in backfat thickness in the Danish Landrace breed from 1952 to 1960. Over this period the average backfat thickness of tested pigs fell from 34·2 mm. to 28·5 mm., a change of two standard deviation units.

The method used to measure genetic change depends on the differencein performance in two or more years of progeny from particular sires or dams. Environmental differences between the years are avoided by measuring performance relative to the year mean. However, allowance has to be made for selection among parents on the basis of their first set of progeny records, through adjusting the initial records by theoretical regression factors. The genetic change is then estimated as a function of the difference between the adjusted first progeny records and the records of subsequent progeny groups.

Separate estimates of the genetic change in backfat thickness were calculated in this way from the progenies of sires and of dams at each of the three stations. These were in general agreement and indicated that there was some genetic improvement in backfat thickness in the Danish Landrace from 1952 to 1960 but that not all of the observed change was genetic change. The overall estimate of the genetic change was —015±0·10 mm. per year and this represented about one-fifth of the observed change. Other less critical results are also given and these lead to the same general conclusion.

Wastage and culling rates in Private Milk Records herds during a three year period, October 1957 to September 1960, were estimated from data collected byfieldsmenduring one week in each month.

Total deaths and disposals among cows fell from 29·3% in 1957–8 to 23·4% in 1959–60 due mainly to reductions in the sales of surplus cows, non-attested cows and reactors to tuberculin. Wastage and culling among cows tended to be higher in winter than in summer. The rate of loss tended to increase in successive lactations and the percentage of animals sold for dairying fell from the third lactation onwards whilst disease, accident and old age became increasingly important reasons for culling.

Total deaths and disposals among heifers fell from 17·3% in 1957–8 t o 11·3% in 1959–60 due mainly to a reduction in the sale of stock for purposes other than dairying as ‘surplus’ or ‘fat’, and to a fall in the numbers sold for dairying for miscellaneous reasons. There was a peak in heifer disposals in early summer.

It is estimated that the average herd life in P.M.R. herds from first calving o t disposal is between 3½ and 4½ years and that average total productive life from first calving to death is between 5 and 6 years.

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. Rates of live-weight gain from 2 to 96 weeks of age are compared in twin cattle of 8 breeds and crosses. The 258 animals in the trial consisted of 77 pairs of one-egg (MZ) and 52 pairs of two-egg (DZ) twins. All were females.

2. Between collection during the first week after birth, and 36 weeks of age, treatment of animals was uniform. After this some animals were grazed and others remained housed, depending on their date of birth. Members of each twin pair were, however, always treated alike. Between 36 and 96 weeks of age grazed stock gained 62 lb. more weight than housed stock. This difference was allowed for in making breed comparisons.

3. The trial period was divided into six stages. The most rapid gains were made between 24 and 36 weeks of age (1·43 lb. per day) and between 36 and 52 weeks (1·48 lb. per day). Earlier and later growth rates were about 30% less than these.

4. Rates of gain varied from 1·10 lb. per day in Ayrshires to 1·38 lb. per day in Friesian × Shorthorn crosses. The Friesian and its crosses with Shorthorn generally made fastest gains throughout the trial. The Ayrshire was slower than the rest. The Shorthorn and its crosses with Hereford and Ayrshire were intermediate in performance.

5. Ratios of within-pair variance in MZ and DZ twins indicate that differences in performance are most strongly dependent on genetic differences-at 12 to 24 and 52 to 72 weeks of age.

1. Sixteen foods, ranging in crude protein content from approximately 2·6 to 10·0%, were each offered ad lib. to four wether sheep. Dry-matter intake, N content and apparent digestibility of dry matter for each food were determined.

2. Voluntary intake of food dry matter was closely related to N content.

3. Slow fermentation in the reticulo-rumen and the associated slow rate of passage through the digestive tract may control the intake of low protein foods by sheep.

4. There was evidence of adaptation of sheep to low protein diets as the trials progressed and significant differences occurred in voluntary food consumption between sheep.

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.

Four groups of Scottish Blackface ewe lambs were reared in the period 11–52 weeks old under different regimes. The regimes differed in the age of the lambs at which they were separated from their dams and whether having been separated they were together in a field and/or penned together n i a sheep shed.

These regimes caused differences in social behaviour among the four groups and also resulted in the groups adopting different parts (home ranges) of an enclosed 350 acre hill pasture. The various home ranges within the pasture are dissimilar environments and it is argued that home range and method-of-rearing effects will be confounded making statistical comparisons between the different rearing treatments impossible.

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.