The effect of three centres of production, two times of lifting and two post-harvest treatments of apparently virus-free seed tubers on sprout development at planting was studied over two seasons. Sprout length and degree of development were determined mainly by the light and temperature conditions during storage. Under similar storage conditions tubers from the most southern region, lifted early and allowed to sprout from lifting produced longer sprouts than those from the more northerly regions, lifted late and sprouted from midwinter. At planting all tubers had sprouts longer than 2·5 cm. Desprouted tubers from the more southern regions had the highest number of sprouts at planting and tubers 'greened' immediately on lifting had the least.

An index of sprout development at planting was defined. The conditions and duration of storage had most influence on the degree of development as measured by this index; sprouts were most developed on tubers sprouted over a long period and on those sprouted in a heated glasshouse. The effects of varying centres of production and times of lifting on sprout development at planting were small compared with those readily produced by varying the storage conditions.

Studies were carried out on the effect of source, time of lifting and post-harvest treatment of apparently virus-free Arran Pilot seed potatoes on subsequent crop growth. The experiments were carried out in 1961–2 and 1962–3 at Efford, Sutton Bonington and Edinburgh. Seed tubers from the more southern region, which were older and showed greater sprout development at planting, gave plants with a higher stem number at soil level, a higher tuber number and a greater percentage of the tuber yield as seed grade than northern-produced seed. High bulking rates were associated with early emergence, high tuber numbers and late apparent time of tuber initiation. In 1962 southern seed produced plants which initiated tubers early and had low bulking rates and low final yields. In 1963 seed source had little effect on the time of tuber initiation of resulting plants, and southern-produced seed gave plants with high bulking rates and high final yields. Early lifted and greened tubers gave rise to plants with the same pattern of response as seed produced at the southern centre. It is suggested that this variation in response between years was due to the climatic conditions at the time of tuber initiation in the field crop.

Seed of a required state at planting can usually be obtained by growth at the centre of ware production provided disease can be controlled and the time between harvesting of seed and planting is longer than about 3 months.

Mutton Merino ewes, all of which had lambed in the preceding in-season, were divided into two groups some 30 days after lambing.

The ‘light’ group was subjected, over 84 days, to a simulated decrease in daylength, achieved by first adding artificial light to the daylight and then stepping down the light at weekly intervals, from approximately 17 h, on 22 January, to natural daylength (13 ¾ h), on 20 April 1967. The control group was exposed to the normally increasing daylength.

Starting on 1 March, the ewes in both groups were ‘teased’ and hand-service commenced on 20 April.

The breeding activity (oestrus, ewes lambing, lambs born and twin births) as well as the length of gestation and birth weight appeared to be unaffected by the light.

It would appear that the ‘short-day’ photoperiodic theory is not applicable to all breeds of sheep, and it is suggested that in sheep with a long sexual season genetic heterozygosity may be responsible for regulating the breeding season by allowing other environmental stimuli, besides light, to trigger-off sexual activity.

A method of preparation of the whole bodies of pigs, suitable for the analyses of their mineral contents, has been described. Two litters of pigs were slaughtered at birth and another two at 8 weeks of age and each pig was analysed for whole body content, of Ca, P, Mg, Na, K and Cl. From another litter of pigs a gilt and castrated male were slaughtered at 23, 41, 54 and 90 kg live weight and their bodies analysed for the same elements. The data were used to derive a series of regression equations relating mineral contents to empty body weight for pigs at birth, 8 weeks of age and from 23 kg to 90 kg live weight. The regression coefficients, which provide a measure of the amount of a particular mineral retained in g/kg increase in empty body weight were, for pigs at birth Ca, 7·9; P, 6·3; Mg, 0·3; Na, 1·5; K, 1·9; Cl, 4·8; for pigs at eight weeks of age, Ca, 13·3; P, 7·4; Mg, 0·5; Na, 1·6; K, 2·3; Cl, 1·7; and for pigs from 23–90 kg live weight Mg, 0·4; Na, 1·3; K, 2·0; Cl, 1·1. For the older pigs Ca and P retentions (g/kg increase in empty body weight) ranged from 13·5 (Ca) and 7·6 (P) at 23 kg empty body weight to 4·3 (Ca) and 1·0 (P) at 90 kg empty body weight.

Three gilts and three castrated males weighing 23 kg live weight were given four semi-synthetic diets containing increasing amounts of Ca and P. The Ca and P contents (% dry basis) and Ca:P ratios for the four diets were A, 0·30, 0·38, 1:1·27; B, 0·58, 0·68, 1:1·17; C, 0·94, 1·13, l:l·20; D, 1·16, 1·47, 1:1·27. Each animal was slaughtered at 41 kg live weight and the whole body contents of Ca and P determined. Six pigs were slaughtered at 23 kg live weight and their bodies also analysed for Ca and P contents. Dietary concentration of Ca and P did not influence rate or efficiency of live weight gain nor carcass characteristics. Net retention of Ca and P increased with increasing dietary concentration of these elements. Analyses of isolated femurs suggested that optimal mineralization of the bone was associated with a net retention of 8·2 g Ca/kg live weight gain. The data were used to calculate a value of 32·9 mg/kg live weight/day for the endogenous loss of Ca in pigs of 23–41 kg body weight. The values have been used to compute a mineral requirement of dietary calcium which is in excellent agreement with that derived from estimates in the literature.

Blood potassium and haemoglobin types were investigated in three breeds of sheep in India. Both high and low blood potassium types and all three haemoglobin types—A, B, and AB—were found to be present in two of the breeds examined, namely Bikaneri and Corriedale x Bikaneri. Mandia sheep had both potassium types but only two haemoglobin types—B and AB. Haemoglobin B and high potassium types predominated in all the three breeds; this would clearly point to the comparative suitability of these animals for relatively drier parts of India.

The differential effect of subclinical helminthosis on digestion and nitrogen metabolism in 1-year-old Brahman x Hereford/Shorthorn cross and British (Hereford/Shorthorn cross) steers was investigated.

When helminths were present, the British steers had lower digestibilities of dry matter and nitrogen, lower nitrogen balances, and higher dialysable faecal nitrogen, than had the Brahman cross steers. There were no breed differences in plasma gastrointestinal leakage (estimated by Cr labelling of plasma proteins), plasma content, total plasma protein, plasma protein half-life or plasma urea.

When helminths were eliminated, plasma gastrointestinal leakage was reduced, and plasma content and total plasma protein were increased. These changes were relatively larger in the British steers. The Brahman crosses had lower plasma protein concentrations and higher plasma urea concentrations than the British steers. Plasma protein half-life was unaffected by parasites.

The breed difference in the haematocrit was not affected by the presence or absence of helminths.

Internal and external follicle diameters of both primary and secondary follicles of Texel x Ossimi and Merino x Barki ewes were greater, at birth, than those in either respective parent breed; the density of primary follicles at birth was less in the cross-breds than in the parental breeds, for both crosses. There was a greater increase of follicle diameter with age in the Egyptian breeds, and mean follicle diameters of the crossbreds were intermediate between those of parent breeds at ages of 3–6 months and above.

Grading up Ossimi sheep with the Caucasian Merino resulted in progressive decrease of mean internal follicle diameter. The F2, with more merino blood, had a greater frequency of the smallest diameter follicles than had the F1.

Statistical analyses were carried out on the data obtained under very strict conditions in metabolism stalls with 41 different rations fed to 127 adult non-pregnant dry cows and with 14 other different rations fed to 35 adult non-pregnant lactating cows that had calved 2–6 months earlier and whose daily milk production ranged from 11 to 20 kg.

The correlations between faecal and urinary phosphorus losses, phosphorus in milk, digestible phosphorus and phosphorus balance and the other nutritive factors of the 55 above-mentioned experimental diets have been calculated.

In dry and lactating cows, with very variable intakes of phosphorus, phosphorus faecal and urinary losses show very wide variations and may be important. They are not influenced by phosphorus intake, and are related, among the many other nutritional factors we analysed only to ingested water and to a lesser extent to the nitrogen of the diet.

The phosphorus balance is thus also very much variable and not really related to the composition of the ration.

This low influence of the diet on the apparent fate of phosphorus can be explained by the interference of unpredictable but certainly quite variable endogenous phosphorus excretion, which is also probably responsible for the effect we found of individual factors and of the previous nutritional status.

In the lactating cows, the phosphorus requirements for milk production influence the utilization of phosphorus since a significant correlation exists between phosphorus secreted in the milk and urinary phosphorus.

In our experimental conditions, the Ca: P ratio does not seem to influence the fate of dietary calcium and phosphorus.

Statistical analyses were carried out on the data obtained under very strict conditions in metabolism stalls with 41 different rations fed to 127 adult non-pregnant dry cows, and with 14 other different rations fed to 35 adult non-pregnant lactating cows that had calved 2–6 months earlier and whose daily milk production ranged from 11 to 20 kg.

The authors have calculated and studied the correlations between faecal and urinary losses of chloride, chloride excretion with the milk, digestible chloride and chloride balance and many other nutritive factors which were analysed for each of the 55 above mentioned experimental diets.

The results show that the digestion and utilization of chloride is not influenced by the amount of ingested chloride at the time of the trial. The digestion is generally very high, negatively correlated with dry matter, energy, and pentosans intakes, and positively with nitrogen and potassium intakes. But the most important factor in the fate of dietary chloride seems to be the necessity for the cow to eliminate most of the time high amounts of potassium in the urines.

A simple and rapid technique for estimating changes in fibre brush-end formation rate is described. The technique was used to give a quantitative estimate of the extent of brush-end formation induced by exogenous hormonal treatment of normal sheep and to establish the time relationship between treatment, fibre brush-end formation and the subsequent casting of the fleece.

The growth of ½ ⅝, and ¾ bred Dorset Horn lambs was examined in Western Uganda. These were produced by mating Dorset Horn rams with East African Blackheaded, ¼ bred Dorset and 1/2 bred Dorset females respectively.

The influence of type of birth (single or twin) was maximum at the end of the main 2-month suckling period and progressively decreased to 11 months of age. The influence of maternal age did not decline as lambs grew older. Dorset ewes, ¼ and ½-bred, had superior milking capabilities, as measured by lamb growth at 2 months of age, to indigenous ewes. Lambs, ⅝ and ¾-bred, were 26 % heavier than ½-bred lambs at 2 months of age, and as all three types grew at the same rate from 2 to 11 months, ⅝- and ¾-bred lambs retained this initial advantage.

The experiment described here is the second of a series of experiments investigating the effect of the time of application of certain plant nutrients on the growth of the potato crop. In this experiment all combinations of three rates of nitrogen (0, 0·75 and 1·50 cwts nitrogen per acre), two times of application (at planting and at the time of tuber initiation) and two rates of application of CCC (0 and 4 lb/acre applied twice, shortly after emergence) were tested and studied by the technique of growth analysis.

There was a linear relationship between leaf area duration (D)and tuber dry matter yield, D accounting for 95 % of the variation in the latter. The maximum amount of nitrogen accumulated in the leaves (Nmax) was linearly related to D, and accounted for 86 % of the variation in D. This relationship was improved if separate regressions were calculated according to whether CCC had been applied or not. Calculated in this way, the regressions indicated that more nitrogen was required for a given value of D when plants were treated with CCC.

Delaying the application of nitrogen resulted in a considerable improvement in the recovery of fertilizer nitrogen (ammonium nitrate). A heavy dressing of nitrogen at the time of planting did not enable the crop to take up sufficient nitrogen for maximum yield. Because of these factors, delaying the application of nitrogen significantly increased tuber yield at both rates of nitrogen tested.

Increasing the rate of nitrogen and delaying its application tended to increase the proportion of stem in the total dry matter; CCC had the opposite tendency. CCC, however, reduced leaf area and the mean effect of CCC was to reduce tuber yields. While there wore no significant interactions between CCC and nitrogen treatments on final tuber yield, it was observed that CCC slightly increased yield when the highest rate of nitrogen was applied late. Ways are suggested in which CCC may be more effectively used.

Field experiments were conducted to study the differential responses of a wheat crop to water stress during different stages of its growth. Evidence was produced to show that both the flowering phase and the stage of grain filling and maturation were more sensitive to drought than the vegetative period of growth. Yield of wheat was not reduced when the crop suffered from cycles of water stress induced during the vegetative period, if the crop received favourable water regimes thereafter. Efficiency of water utilization from different water treatments was assessed. There was no relation between the protein and starch contents of the grain and the type of water treatment.

The effects of different water treatments on crop development and on components of yield were studied.

Three-hundred and thirty-four female sheep of the Blackface, Cheviot and Welsh Mountain breeds and the crosses among these breeds kept as one flock at pasture were bled in September 1966. Concentrations of Ca, Mg, K, Na and Cl were determined on plasma and P on whole blood. Mean concentrations (mg/100 ml) were: Ca 9·65; P 5·54; Mg 2·02; K 23·2; Na 345; Cl 365; and coefficients of variation (%) 11·1, 18·1, 29·0, 10·5 6·7 and 2·3 respectively.

Breed was a highly significant (P < 0·01) source of variation for Ca, P, Mg and Cl, but except for Mg, the contribution to the total variance was small (< 10 %). Average values for cross-bred ewes deviated significantly (P < 0–05) from those of pure-bred for Ca and P concentration. Live-weight, within class, had a small but significant effect on Ca and Mg concentration.

The concentration of Ca and Mg declined very significantly with age of ewe, there was a similar trend for K, while P showed a slight but steady tendency to increase with age, and Cl showed a more erratic increase.

For Ca, barren ewes had a lower concentration (– 0·44 mg/100 ml) than ewes with lambs whilst ewes with single lambs at birth had lower concentrations (– 0·35) than ewes with twins. Other factors with effects too large to be ignored (P < 0·1) were the interaction of breed x no. of lambs (K and Cl) and swayback history (Cl).

Two sets of correlations among blood mineral concentrations were calculated (1) those attributable to the effects of various factors (breed, age, lambing performance, etc.) and (2) those remaining (residual) when the effects of such factors had been removed as sources of variation in mineral concentration (the equivalent of correlations within subclasses).

Correlations arising from breed differences in mineral concentrations were highest for Ca.P (– 0·81), Ca.Cu (0·83) and P.Cu (–0·95). Correlations consequent on changes with the age of the sheep were most marked for Ca.Mg (0·97, P < 0·01) and Cu.K (–0·92, P < 0·05) and approximately 0·8 (P < 0·1) for Ca.K, P.Mg, P.K and K.C1.

Residual correlations were all below 0–2 (although seven of the twenty-one were statistically significant, P < 0·05) suggesting that within subclasses most of the variation in the concentration of anyjone mineral was independent of that in the other minerals. Simple and partial correlations were very similar in magnitude suggesting that the associations found between pairs of minerals were not attributable to joint co-variance with any of the other five minerals.

As the sheep grew older, changes in the concentrations of Ca, P and Mg were significantly correlated with the increases in live weight. Within subclasses, differences among the sheep in live weight were significantly (P < 0·05) and positively correlated with differences in the concentrations of Ca (r, 0·11), Mg (0·13) and Cu (0·11).

Two experiments were carried out to study the effect of the ad libitum feeding of whole-milk substitutes, either warm or cold, and the availability of drinking water, on the level of food intake and live-weight gain of calves. Freshly cut grass or pasture was the sole source of solid feed.

In Exp. 1 forty Hereford x Friesian male calves were reared individually indoors in a 2x2x2 factorial design experiment. The treatments were full-cream milk powder υ milk substitute, temperature at which the milk was offered, and drinking water υ no drinking water available to the calves. Fresh grass was cut daily and fed ad libitum to all animals from the sixth day of treatment.

In Exp. 2, twelve Hereford x Friesian male calves were reared at pasture on warm or cold full-cream milk during weeks 1–7, and on milk substitute during weeks 8–15.

During both experiments calves receiving warm milk drank slightly more than calves receiving cold milk; this difference was significant in Exp. 1 only. There was a tendency for calves receiving cold milk to make higher live-weight gains (0·05 < P < 0·1) when drinking water was available than when it was not. In Exp. 1, the rates of live-weight gain of calves receiving warm or cold milk substitute with drinking water available were 0·99 and 0·89 kg/head/day, respectively: for calves receiving full-cream milk powder the corresponding rates were 0·86 and 0·80 kg/head/day. When drinking water was not available the rates of gain of calves on warm or cold milk substitute were respectively 0·93 and 0·82 kg/head/day, and on full-cream milk powder, 0·94 and 0·55 kg/head/day.

In Exp. 2 the rate of live-weight gain measured during the first 7 weeks, whilst calves were receiving full-cream milk powder, was 0·88 kg/head/day irrespective of the temperature at which the milk was given. During weeks 8–14 milk substitute was given, which resulted in rates of live-weight gain of 1·05 kg/head/day for calves receiving warm milk and 0–92 kg/head/day for calves receiving cold.

The rates of gain attained on cold milk are considered adequate for rearing calves intended for an intensive system of production. It is also suggested that the use of cold milk could facilitate a marked decrease in the daily labour requirements associated with the artificial rearing of calves.

Two-hundred-and-seventy-three Scottish Blackface ewes in three ages (5, 4 and 2 years) were differentially group fed over 6 weeks in such a manner that at 6 weeks before mating there were approximately equal numbers in each of six subjectively assessed body condition groups ranging from score 1 (lean) to score 3½ (moderately fat). Over the 6 weeks prior to mating these groups were either well fed, fed at about maintenance, or underfed so that at mating the maj ority of ewes were in either condition 1½ or 3.

A predetermined random sample of mature ewes from each of the six original condition groups was killed 2–3 days post-mating for ovulation counts. Surviving ewes were fed above maintenance post-mating and the number of lambs recorded at birth. Condition at mating had a significant, positive effect on both ovulation and lambing rates but had no effect on infertility measured as the difference between them.

The level of food intake prior to and at mating had no effect on either ovulation or lambing rates of moderately fat ewes (condition 3) but the results can be interpreted as indicating that the level of food intake had a positive effect on both ovulation and lambing rates of lean ewes (condition 1½).

In a comparison involving 1467 births significantly more Dorset Horn than Merino ewes lambed during the period 08.00–18.00 h. The distribution of lambing during the day differed significantly between breeds. The daytime patterns averaged over breeds, and differences between breeds in patterns, did not change from year to year. At winter and spring lambings, 37% of Merino and 62% of Dorset Horn ewes lambed during the day (08.00–18.00 h) while during summer the corresponding percentages were 23 and 39.

For both breeds, the percentages of primiparous and multiparous ewes lambing during the day period were approximately the same. For Dorset Horns, the proportions of single and multiple births occurring during the day were similar.

In a factorial experiment the effect of two protein intakes and three patterns of feeding in the second pregnancy of 48 Large White x Wessex Saddleback sows was examined. The high protein (HP) diet (19·5% crude protein) contained 15% white fish meal. The low protein (LP) diet (10·5% crude protein) contained cereal protein only. Nutrient components of the diets differed in protein only. The pattern treatments involved allowances of 1·8 kg (L), 2·7 kg (C) and 3·6 kg (H) per day, the three pregnancy patterns being HL, C and LH with the changeovers made from the 49th to the 63rd day post coitum (p.c). Sows on the three pattern treatments received the same total amount of feed from 0–112 days p.c. and were treated alike at farrowing and during lactation.

Fertility and parturition results were similar for all treatments, but the number of piglets alive after birth (when weighed) was least for LP sows on the HL pattern. At 3 weeks of age the size and weight of litters on HP sows were significantly greater than those on LP sows (P < 0·05 and < 0·001 respectively). More piglets were weaned by HP sows than LP sows (P < 0·05). HP sows gained more weight in pregnancy (P < 0·001) which was slightly longer, and lost more weight in lactation (P < 0·05) than LP sows.

The HL pattern of feeding was associated with smaller live weight gains in pregnancy than the LH pattern (P < 0·001) and the total birth weight of HL litters was lighter than LH (P < 0·05), mean piglet weights being similar. Lactation performance was unaffected by pattern treatment.

The main conclusion is that a low intake, particularly during the latter half of pregnancy, of protein which is of vegetable origin, is associated with decreased viability of the piglets at birth and in early suckling life, and with lower capacity of the sows for milk production.