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.

Of eight experimental fertilizers (with %N; %P2O5; %K2O ratios of 2:1:1) obtained, four contained triple superphosphate and four mono-urea phosphate; all contained muriate of potash. In the first four, urea supplied either 100, 66, 33 or 0% of the total N (ammonium nitrate supplied the remainder); in the second four, urea and ammonium nitrate supplied only the balance of the N, but in the same proportions.

For barley, each fertilizer was combine-drilled to give 0·5 or 1·0 cwt N/acre. In 1965, much rain fell after drilling, early growth was not harmed and yields from each fertilizer were the same. In 1966, dry weather followed sowing and all fertilizers checked growth; those containing urea killed many plants and diminished yields. Also, yields from the fertilizers containing urea phosphate were larger than from those containing superphosphate; thus urea phosphate was safer than urea alone. For kale, the fertilizers were broadcast in May to give 1·25 or 2·50 cwt N/acre. None seriously diminished plant number and yields from all were similar.

Increasing the proportion of urea in the fertilizers greatly increased %N in the barley grain in 1966, but not in 1965. The crops recovered more N from ammonium nitrate than from urea.

Forty-two Persian Blackhead ewes were used to investigate the effect of three prenatal planes of nutrition 6 weeks before lambing on birth weights and weights at 4 and 12 weeks after birth of their progeny. Nutritional regimes were: good grazing with concentrate supplement (high), good grazing without supplement (medium) and poor grazing without supplement (low). Pastures used were rotationally grazed Pangola grass. High-plane ewes gained significantly more weight during the last 6 weeks of gestation than ewes of the other two groups. Ewes nursing twin lambs lost significantly more weight than ewes nursing singles during the first 4 weeks of lactation. Birth weights of male single lambs and lambs from mature ewes were significantly affected by the prenatal plane of nutrition of the ewe. Lambs from mature ewes weighed significantly more than lambs from maiden ewes and male lambs weighed significantly more than females. Live-weight gains to 4 weeks were significantly affected by prenatal plane of nutrition in all cases. Type of birth was an important factor affecting growth rate and maturity of the ewe less so. Male lambs gained more weight than females during this period. Similar tendencies were apparent during the growth period of 4–12 weeks after birth although rate of gain was lower.

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).

Statistical analyses were carried out on the data obtained under strictly controlled 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 potassium losses, potassium excretion in the milk, digestible potassium and potassium balance, and the 75 other nutritive factors which were analysed for each of the 55 above mentioned experimental diets.

The results show that three nutritional factors, potassium, dry-matter and nitrogen intakes, influence the fate of dietary potassium. The apparent digestibility of potassium is hyperbolically related to potassium content of the diet since the true digestibility of potassium is very high, unrelated to potassium intake and rather constant and since about 2·2 g of endogenous potassium are excreted in the faeces per kg of ingested dry matter.

The quantities of digestible potassium strongly influence both the potassium urinary outputs and potassium balance. An increase in digestible dry matter enhances too the urinary potassium excretion as well as faecal output and lower potassium balance twice as much.

But the most interesting feature in the potassium metabolism is that at any level, ingestion, digestion, excretion, there is a very close correlation between potassium and nitrogen.

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).

Colchicine induced 64-chromosome white clover was compared at a number of centres with control material (2n = 32), as spaced plants and in broadcast plots with and without companion grasses.

The chromosome-doubled material generally conformed to the well-known reaction of polyploids; the plants were later flowering, had thicker petioles and stolons, broader leaflets and spread less vigorously. Yield of green matter of spaced plants was much less, and in broadcast plots the gross yield (grass + clover) and that of the clover fraction was 7% less than in comparable S. 100 plots. The Finlay-Wilkinson analysis indicated that the chromosome-doubled form did not respond to improved conditions to the same extent as did the control varieties. The presence of grass in the mixture partly compensated for low clover yield, but was insufficient to increase total yields to that of S. 100 controls.

Statistical analyses were carried out on the data obtained under strictly controlled 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 sodium losses, sodium excretion in the milk, digestible sodium and sodium balance and the 75 other nutritive factors which were analysedfor each of the 55 above mentioned experimental diets.

The most important factor in the fate of sodium is the amount of dietary sodium. Sodium digestibility is neither total nor constant: faecal losses and digestible amounts are enhanced when sodium intake is increased and faecal losses are also positively correlated with dry matter and nitrogen intakes. An increase in digestible sodium benefits both urinary excretion and balance, the latter being reduced by an increase in dry matter and nitrogen intake.

Sodium balance is always negative when sodium content of the diet is lower than 0.1% in the dry cows and 0.2% in the lactating cows. In our experimental conditions, the sodium requirements for milk production do not influence sodium digestibility, but are met above all to the detriment of urinary losses.

The effect of maturity on the nutritional quality of hay from two alfalfa varieties and four grass species was studied. Each hay was harvested at six different stages of growth, chopped in 4–6 cm lengths, and fed to sheep in quantities of 10% in excess of voluntary intake. The relationship between intake (Y) and digestibility (X) of dry matter was best expressed by regressions of the form: Y = a + b1X + b2X2. The rate of intake declined 1·5 g daily per kg0·75 of body weight per unit decrease in digestibility percentage, and was the same for both alfalfa and grass hays. However, the intake of alfalfa hay was about 10% higher than that of the grass hays of similar digestibility. No differences in the relationship between intake and digestibility (P < 0·05) were observed between the two alfalfa varieties or between the four grass species. When the nutritional quality was expressed as voluntary intake of digestible organic matter daily per kg0·75 of body weight, and time of harvest as day-number of the year, the difference in quality between the six kinds of hay was very small or absent at the beginning of the season (immature to prebloom) and increased toward maturity (dough stage to seed ripe). The decline in quality of alfalfa hay was slower than that of grass hay, and ceased at the mature to overripe stage. On the average, voluntary intake of digestible organic matter declined 0·29 g daily for each day delay in harvest time; this decline varied from 1·2% of the daily intake of digestible organic matter in the beginning of the season to 0·6% at the mature stage. Time of harvest ‘accounted for’ 77–89% of the variation in the quality of the hays. The confounded effect of maturity and leanness on the nutritional quality of the hays was expressed best by concave, second degree polynomial regressions. On the average a unit decline in percent leaves corresponded to a decline of 0·58 g and 0·73 g respectively in the daily intake of digestible organic matter from alfalfa and grass hay. This varied from over 1 g early in the season to less than one tenth of a gram late in the season. The confounded effect of leafiness and growth stage ‘accounted for’ over 75% of the variability in nutritional quality. The relationship between intake and digestibility of the alfalfa and grass hays was used to illustrate how voluntary intake of metabolizable energy (percent of requirement for maintenance) from hay of pure or mixed species may be predicted from in vitro digestibility.

Three dry cows, each fitted with a permanent rumen fistula, were fed hay and flaked maize or hay and rolled barley in widely different proportions. All rations were offered at 7 kg dry matter daily for 3 weeks following hay alone. The cows refused all cereal 3 or 4 days after introduction of rations including 80 and 100% flaked maize; recovery of intake occurred in most instances within a further 3–10 days. On the 100% flaked maize ration, the refusals were associated with very low pH and high concentrations of lactic acid in the rumen.Refusalsof rolled barley were small and showed no clear pattern.

Rumen fermentation was reasonably stable during the last week of each period except with the 100% barley rations. On the rations containing flaked maize, molar proportions of volatile fatty acids (VFA) varied widely but on only one occasion did the proportion of acetic acid fall below 55% and in two cows that consumed flaked maize alone, the proportion of acetic acid in the rumen exceeded 60%. On the rations containing rolled barley, increasing proportions of barley were associated with large decreases in the proportion of acetic acid and increases in the proportion of propionic acid. The maximum proportion of n-butyric acid was found on the rations containing 50% cereal.

It is suggested that, when large proportions of cereals are fed, the proportions of VFA bear no clear relationship to the crude fibre content of the ration but that an association with rumen pH may exist.

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).

Determinations were made of the available-water capacities and moisture release characteristics of six soils of different texture from Rothamsted, Woburn and Saxmundham. The amount of available water retained in the surface foot of soil ranged from 1·59 in in a sandy loam to 2·75 in in a silt loam under permanent grass. With one exception soils which had received additions of farmyard manure had significantly higher available-water capacities than unmanured soils.

Three experiments were conducted to investigate the influence on nitrogen retention of feeding protein supplements to early weaned lambs direct to the abomasum via the oesophageal groove. In Exp. 1 the lambs received a basal diet of barley and a protein mixture consisting of soyabean meal, sunflower meal and fish meal which was given either in a liquid suspension from a bottle or as dry feed incorporated with the barley. The results showed that the regression coefficients of nitrogen retention on intake were 0.48 and 0.33 with liquid and dry feeding respectively. The regressions of urinary nitrogen on intake were with liquid and dry feeding respectively 0.26 and 0.44.

In Exp. 2, various sources of protein were compared isonitrogenously as substitute for part of a barley concentrate ration. The nitrogen intakes and retentions were 14·28 and 5·09, 20·16 and 9·39, 20·53 and 8·19, 19·00 and 7·80, and 18·87 and 7·86 g/day for the control diet and fish meal, yeast, soyabean meal and sunflower meal supplemented diets respectively.

In Exp. 3 the fish meal supplement was compared with a high lysine, bloodmeal and with casein as liquid supplements to a basal diet of barley concentrate. The intake and retention of nitrogen were for bloodmeal, casein and fish meal respectively 23·41 and 7·48, 22·56 and 9·11, and 21·88 and 8·31 g/day. It appeared that the protein sources high in methionine resulted in the highest nitrogen retention. The implications of these findings in relation to the nutrition of young ruminants is discussed together with an evaluation of the experimental method as a technique to study postruminal digestion.

In the course of an experiment designed to study the effects of calcium and phosphorus supplementation on the performance of Scottish Blackface hill ewes, with particular reference to the premature loss of permanent incisor teeth (Gunn, 1969), blood samples were taken from 40 ewes on ten occasions per year over a 4-year period. These were drawn equally from a control and three treatment groups. The control group followed the existing pattern of ewe management on the farm in question by utilizing improved pastures in the spring and early summer, and the treatment groups were a calcium dosed group (12 g calcium carbonate) and a phosphorus dosed group (13 g monosodium phosphate), both of which received the same management, and an undosed group run permanently on the hill. Details of the management and feeding are given in a previous paper (Gunn, 1969). It is sufficient to say here that mineral dosing took place three times per week between mid-February and the end of May and no minerals except salt were added to the concentrated ration fed to all groups at the rate of 10 oz (283 g)/head/day from mid-February to early May. Lambing commenced at about the end of the first week in April.

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.

Results are presented from freezing tests on five varieties of winter oats from diverse origins, on their crosses in the F1 and F2 generations and on selected F3 lines from six of the crosses.

Analysis of the F1 results indicated that frost resistance was mainly determined by recessive genes, additive in their effect, but in the F2 experiment there was evidence of non-allelic gene interaction. Significant general combining ability (GCA) effects were obtained in both the F1 and F2 experiments but specific combining ability (SCA) effects were significant only in the F2 crosses. The variety Novosadsky II displayed consistently high general combining ability.

Tests on F3 lines derived from selected F2 plants revealed considerable transgression for frost resistance in all six crosses studied. The results are discussed in relation to breeding for improved frost resistance in oats.

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.

An experiment was conducted with 32 spring-born Friesian heifer calves, purchased at an average age of 10 days and fed on cold reconstituted milk substitute at pasture.

The milk feeding treatments were 4, 4½, 6½ and 9½ weeks in length, during which time calves consumed an average of 17, 23, 43 and 70 kg dry matter/head of milk substitute respectively. The differences between treatment mean live-weight gains for 10½ weeks of the experiment were highly significant (P < O·OOl): the gains were 0·49, 0·43, 0·64 and 0·78 kg/head/day. There was no significant difference between mean rates of live-weight gain after the tenth week so that the overall treatment—mean live-weight gains for the first 23 weeks, which were 0·65, 0·61, 0·72 and 0·74 kg/head/day, strongly reflected the length of the milk-feeding period and demonstrated no significant compensatory growth by the calves.

Twenty of these animals were housed for the subsequent winter period and were returned to pasture for a second grazing season. These were artificially inseminated as their individual live weights reached approximately 320 kg. Animals weaned after only 4 weeks of milk feeding took an average of 9½ weeks longer to reach live weights of 320 kg than these receiving milk for 9½ weeks. There were no marked indications of compensatory growth during this extended period of observations.