Forty-eight cross-bred wether lambs were used to measure the effects of severe feed restriction and realimentation on the body and carcass composition of immature sheep. Ten of the total number of sheep were used as an initial slaughter group, 12 were continuously fed (six at the ad libitum level of intake and six at 70% ad libitum), 26 were progressively underfed and 18 of them were realimented after a mean loss of about 25% empty body weight (EBW).

Shrunk body weight (SBW = weight after an 18-h fast with access to water) was a good predictor of empty body weight (EBW = SBW minus gastro-intestinal contents) and the EBW of continuously growing sheep was a good predictor of body water, protein, fat, energy and ash, but it was not precise after realimentation, particularly in the early stages of refeeding. Restricted continuous supermaintenance feeding did not alter the body composition of the sheep from that of the sheep on the ad libitum intake at any given EBW except slightly to increase the carcass protein content.

Although underfeeding to produce an EBW loss of 25% generally produced changes in the chemical body components which were similar to a reversal of normal growth, body fat did not decrease during the first half of the submaintenance feeding and did not increase during the first 2 weeks of realimentation. Under all circumstances percentage body fat was very closely related to percentage body water.

Sheep realimented at 26 kg (after losing 25% EBW) contained, at 45 kg EBW, more bodywater and protein and less fat and energy than continuously-fed animals of the same EBW. The treatment effects were greater in the carcass and had little effect on the non-carcass EBW, with th e result that the refed sheep had 1800 g more water × protein in a carcass that weighed 700 g more than one from a normally grown sheep of the same EBW. The regression of calorific value of th e ash-free dry matter on body fat as a percentage of ash-free dry matter gave calorific values of body protein and fat as 5·652 and 9·342 kcal/g of ash-free dry matter, respectively.

Experimental conditions and design were described in part I. Separable lean and fat were highly correlated with the carcass and whole body components of protein and ether extract. The carcasses of refed sheep at 45 kg empty body weight (EBW) had about 1 kg less fat and more lean than carcasses from sheep of similar weight which had been continuously fed. Restricting feed intake to 70% ad libitum gave carcasses that had more protein than those from sheep fed ad libitum both during continuous growth and after realimentation.

Sheep that had lost 25% EBW to 26 kg and then were refed to 31 kg EBW had 34% less separable carcass fat than sheep which had been continuously fed to EBW of 36 kg and then had lost weight from that level to 31 kg EBW, and the separable fat was higher in water content than during normal growth (an effect shown consistently in realimented sheep).

Severe underfeeding rapidly reduced bone water but bone ether extract continued to accumulate. After a period of refeeding, bone fat was rapidly mobilized and bone water quickly returned to normal. During early weight loss following food intake reduction, there was a larger decrease in carcass water than expected, and most of the discrepancy could be accounted for by the disproportionately large loss of water from bone and separable fat.

It is concluded that during early regrowth there is a marked stimulus of lean tissue growth and depressed fat synthesis. After this initial period, growth rate of carcass tissues is not greatly different from that found in continuously growing sheep although there is some evidence of a small positive rate of protein growth effect following through to 45 kg EBW in the refed animals. The ratio of muscle gain to fat gain from 30 to 40 kg EBW was 2·23 in realimented sheep and 1·08 during normal growth.

Experimental conditions and design were described in Part I. When compared with continuous growth, there was a 46% increase in rate of gain following refeeding, but no increase in intake per kg0·734 (MBS) per day. Part of the reason for this was the rapid accumulation of body water after realimentation. If the total cost of feed, including that of the weight-loss phase, is used to calculate the feed required per unit of gain, however, the sheep realimented at 26 kg to reach an empty body weight (EBW) of 45 kg had a requirement 27% higher than ad libitum continuously fed sheep taken to the same final EBW.

The only treatment effect on digestibility or metabolizability of the diet that was not accounted for by level of intake was a depression immediately after underfeeding commenced. The metabolizable energy (ME) value later decreased markedly as a result of the relatively high proportion of gross energy lost in the urine (14·4%).

There were no significant differences between normal growth and refeeding in maintenance requirement or efficiency of energy retention above maintenance. The combined figures were 107 ± 14 kcal ME/kg MBS/day and 52 ± 7% respectively.

Growing conditions and testing methods were varied to investigate the use of the Pelshenke test in breeding wheat varieties for good bread-making quality in the United Kingdom. Varieties of winter wheat representing a range of bread-making quality were consistently differentiated. Fresh compressed yeast gave greater varietal differences than did dried yeast but kneading time and grain moisture content were not critical. The values obtained were relatively insensitive to the early stages of germination, to the addition of α-amylase and to variation in grain protein content resulting from N fertilization and irrigation. Thus it appears that the Pelshenke test mainly reflects gluten quality, rather than the whole complex of characters which are integrated by baking tests, and the ranking of the varieties is sufficiently independent of environmental conditions to be of considerable value for selection of early generation breeding material.

Seeds of okra were sown in moist soil and subjected to heat stress of 45 °C for 10 h on day 0 (day of sowing), day 1 or day 2 after sowing. Stresses on day 0 and, to a lesser extent, on day 1 promoted hypocotyl elongation and accelerated seedling emergence. Stress on day 2 retarded hypocotyl elongation and did not accelerate emergence. The results were similar for seeds sown at depths of 1, 4 or 7·5 cm. For 10-h stresses on day 0, 40 °C was slightly less promotive than 45 °C; but 50 °C or above resulted in no emergence whatsoever. Subjecting dry seeds to 40–60 °C for 24 h before sowing gave no appreciable acceleration of emergence; instead, at 60 °C there was a 24-h delay in the onset of emergence. Seeds were also incubated for 1·5 h in water at temperatures ranging from 40 to 80 °C. Emergence was accelerated at 40 to 65 °C, with the greatest acceleration at 45 °C. It is suggested that incubating the seeds at 45 °C for 1·5 h before sowing could afford a practical means to accelerate field emergence of okra.

In order to examine whether high yield of maize could still be maintained at high plant densities by creating an ‘erectophile canopy’ through artificial defoliation of laminae, an experiment at Pantnagar, India, was made on the effect of density, stage and degree of defoliation in two divergent seasons, Kharif (rainy) and spring, of the year 1972. The defoliation treatments were either partial (clipping off the apical half of individual leaves) or complete (full leaf removal) and were imposed at three stages of plant growth, namely when 10 or 16 leaves were fully open or 12 days after silking. These treatments were applied at two plant densities, 60000 and 90000 plants/ha.

Grain yield of maize increased significantly with the increase in population density in the spring season. The trend was diametrically opposite in the Kharif season. Defoliation at the 10th fully open leaf stage produced more grains than defoliating 12 days after silking, which in turn produced more than defoliating at the 16th fully open leaf stage, when plants were in full bloom. Increase in the degree of defoliation at the latter two stages of plant growth reduced grain yield, the effect being more at the 16th leaf stage. However, 50% defoliation at the 10th leaf stage increased grain yield in the Kharif season.

The percentage protein content of grain declined with the increase in population density whereas increase in degree of defoliation increased the grain protein content. Higher protein content of grain was recorded in the spring than in the Kharif season. The leaf protein decreased as the plants neared maturity, especially at the higher degree of defoliation treatments.

Sucrose and reducing sugars declined significantly with the increase in degree of defoliation. The reduction in sucrose was large enough to account for the reduction in total sugar percentage. Similar trends were observed in the sugar-to-protein ratio.

Data are presented from an experiment made in two crop seasons, to examine the effects of plant density and degree of defoliation at different stages of growth in maize at Pantnagar, India, on the dry-matter accumulation in different plant parts, leaf area index (LAI), time of silking and grain yield components.

Different patterns of dry-matter accumulation in various plant parts was observed. Silking was delayed by increasing plant density. Defoliation (even partial) at the 16th fully expanded leaf stage resulted in substantial reduction in LAI and such yield components as number of ears, ear length, ear diameter and 1000-grain weight. On the other hand, partial defoliation done at the 10th fully expanded leaf stage to simulate an ‘erectophile canopy’ led to yield increases even under high plant density (90000 plants/ha) in the Kharif (rainy season), mainly through an increase in number of ears, 1000-grain weight and grain to stover ratio coupled with a reduction in barrenness and percentage of lodging. It is suggested that an increase in the photosynthetic efficiency per unit area of leaf resulting from the ‘erectophile canopy’ is the reason for these effects.

Twelve rumen-fistulated British Friesian castrated male calves, initially three months of age and 77 kg live weight (LW) were fed, both ad libitum and at a restricted level of 21 g organic matter (OM)/kg LW, on either maize silage (26% dry matter, 8.6% crude protein in D.M.) alone or with 2% of urea in the silage D.M., added at the time of feeding. At each level of urea (0 or 2%) silage pH was either increased to pH 5·45 by the addition of sodium bicarbonate, or left unchanged (pH 3·95) in a change-over design within each urea level. Addition of urea increased voluntary silage D.M. intake by 8% (P < 0·05) and partial neutralization increased consumption by 12% (P < 0·01). However, the response to urea only occurred when the silage was partially neutralized.

At restricted intake, addition of urea increased rumen ammonia nitrogen from 3·17 to 13·41 mg/100 ml (P < 0·001) and blood urea nitrogen from 2·20 to 10·06 mg/100 ml (P < 0·001). There was no significant effect of addition of urea or of bicarbonate on rumen pH, VFA concentration or energy digestibility. However, the addition of urea significantly increased N retention (P < 0·01). Partial neutralization of silage was associated with an increase in venous blood pH from 7·366 to 7·396 (P < 0·001), and urine pH from 7·43 to 8·42 (P < 0·001).

It is suggested that both low nitrogen content and acidity limit the nutritive value of ensiled maize, and that the effects of addition of urea and of partial neutralization may be metabolic rather than ruminal.

Results of a co-ordinated trial carried out at 19 centres and involving 632 growing pigs indicated that the performance of pigs receiving diets supplemented with copper sulphate, at 250 mg Cu/kg diet, can be improved by the addition to the diet of 10 mg/kg of ‘Payzone’ or 50, reducing to 20 mg/kg, of ‘Grofas’. Zinc bacitracin, 50 mg/kg diet, was not effective. There were no marked effects on carcass quality.

Setts of water yarn (Dioscorea alata) weighing 75 g each were pre-sprouted in sawdust and then grown in soil. The plants were subjected to moisture stress by withholding water from day 15 to 35, or day 36 to 56 or by watering only once every 14 days. In all cases, tuber initiation was delayed, the greatest delay being in the plants that were watered once every 14 days.

Some setts of D. rotundata that were placed in moist sawdust were seen to produce new tubers without their shoots emerging above the sawdust level. This was taken to indicate that some of the photosynthate in the sett was being transferred into the new tuber. This could offer a partial explanation for the greater tuber yield that results from larger setts.

Experiments are described which analyse the effects of date of sowing and of a black petroleum soil mulch on the growth of two maize hybrids. The two hybrids used were Anjou 210, which is late maturing in S.E. England, and Kelvedon 75A, which is an early hybrid.

As sowing was delayed from mid-April until the end of May, so there was a greater development of vegetative tissue (mainly stem) and leaf area which reached peaks at a later stage after silking. In Anjou 210 early sowing led to higher grain yields (12%) as the production of peak vegetative weight near to the time of silking allowed dry matter produced after that stage, still at a time of high radiation, to move direct to the oars. Also, the remobilization of the secondary source of grain dry matter, namely previously stored photosynthate from the stem, occurred earlier with early sowing and to a greater extent when a longer grain-filling period was allowed.

The hybrid K 75A had a lower vegetative weight, and earlier silking coincided with higher levels of radiation, and the resultant increase in net assimilation rate led to a higher proportion of dry matter being partitioned into the ear. Because this hybrid flowered and senesced early, reserves of stem carbohydrate were low and the time available to transfer carbohydrate to the ear was short, resulting in lower yields than in the later maturing Anjou 210. K 75A also responded unexpectedly to the sowing treatments. Although late sowing gave higher grain yields in both hybrids up to 156 days after sowing, in the case of K 75 A, the early senescence curtailed the continuation of grain fill that would normally give early sowing an advantage and hence the late sown K 75 A produced 10 % more grain.

The application of a black petroleum mulch to the surface of the soil to raise soil temperature enhanced the benefits derived from early sowing. Plants given this treatment produced greater leaf areas and vegetative dry weights. As a result more carbohydrate was translocated from the stem during the grain-filling period, increasing grain yield by 13% following an increase in both number of grains and individual grain weight.

Metabolite production rates were determined in the portal vein and hepatic veins of catheterized adult dairy cows maintained under normal conditions of husbandry. The production rates were calculated from the metabolite concentrations in arterial, portal and hepatic-venous blood, and from the rates of blood flow in the portal vein and the hepatic veins. In general, qualitatively similar metabolite production was observed in three non-lactating and two lactating cows, but production rates tended to be higher in the lactating cows due to higher blood flow rates.

About half the lactate utilized by the liver was absorbed from the gut, while the other half was derived from endogenous sources. Lactate absorbed from the gut was quantitatively of less significance than propionate as a substrate for hepatic metabolism. Even in cows that were well fed, there was a net production of ketone bodies from the liver that was almost as great as the net production from the gut. However, while the liver produced D-3-hydroxybutyrate it took up acetoacetate. In the lactating cows, acetate, propionate and butyrate were absorbed from the gut in the proportions of 9·5:2·5:1, respectively. About 90% and 80% of the absorbed propionate and butyrate, respectively, were taken up by the liver.

On the routine hay/concentrate diet there was little net uptake or output of glucose by the gut. However, there was consistent production of glucose by the liver, amounting to a maximum, in this study, of about 11 mol/24 h, assuming constant glucose production throughout the 24 h day. The rate of carbon dioxide appearance in the portal vein was about twice that of oxygen uptake by the gut. The liver used oxygen, and produced carbon dioxide, at nearly equal rates. The uptake of glucogenic substrates by the liver accounted adequately for the observed rates of hepatic gluconeogenesis.

In one of the lactating cows it was observed that there was a net production of acetate by the liver that amounted to half the net absorption of acetate from the gut (ethyl alcohol was not the precursor of this acetate) and that (glutamine + asparagine) and serine had the highest rates of appearance in the portal vein and the highest rates of uptake by the liver.

Transverse sections of Festuca arundinacea Schreb. leaves were incubated in cellulase at 40 °C with and without pepsin pretreatment. The sequence of tissue breakdown (mesophyll-phloem-adaxial epidermis) was the same in both treatments, but the rate of breakdown was much slower without pepsin pretreatment (up to 30 h compared with up to 90 min). Pepsin appeared to make the primary cell wall more susceptible to cellulase attack. Young leaves were digested faster than old. Possible applications to the evaluation of grass nutritive quality are discussed.

The reproductive development and seed production characters of a Lolium multiflorum × Festuca pratensis tetraploid hybrid and a Lolium perenne × Festuca pratensis tetraploid hybrid were compared with those of their tetraploid parental cultivars. Experiments were carried out under glasshouse and natural conditions; single plants were studied as only small quantities of seed were available from the breeder. The lowtemperature/short-day requirements for inflorescence induction of the two hybrids were in between those of the corresponding parental species. The variance of the date at which vegetative primordia changed to the reproductive condition was greater in the hybrids than in the parental cultivars, but the variance of the dates of inflorescence emergence were similar for the hybrids and parental cultivars. Inflorescences ranged from the Lolium type with only sessile spikelets to the Festuca type with primary branches. Inner glumes, which are absent in the Lolium parents but present in Festuca pratensis, were found in the hybrids, though not in all spikelets. In the Lolium perenne × Festuca pratensis hybrid pollen release, potential pollen viability and floret fertility were low, but the Lolium multiflorum × Festuca pratensis hybrid produced large amounts of pollen with a higher potential viability and had floret fertilities similar to those of its two parental cultivars. There was sufficient variation in reproductive characters for further selection, particularly in the Lolium perenne × Festuca pratensis hybrid.

This paper describes the chemical composition of dressed carcasses of Angus steers and relationships between chemical and dissected components of these carcasses. These cattle were grown from 300 to 440 kg at three different rates. The rates were: High (H, 0·8 kg/day), Low (L, 0·4 kg/day) and High-Maintenance (HM, 0·8 kg/day followed by a period during which body weight was maintained constant).

There were no significant differences between treatments in the regression equations for weight of water, protein or chemical fat against left side weight (half carcass). However, weight of ash was significantly greater in the HM group than in the H group. These results are similar to those obtained with dissection data on the right side of the same carcasses.

There were no significant differences between treatments for regression equations predicting dissected composition from chemical composition. The common regressions for each component are as follows:

log y (total side muscle) = 0·282 + 1·061 log × (protein) (Sν,× 3%), (i)

log y (total side bone) = 1·055 + 0·836 log × (ash) (Sν×) (ii)

log y (total side fat) = – 0·380 + 1·076 log × (chemical fat) (Sν,× 4%), (iii)

where all values of × and y are in grams.

Equations (i) and (ii) were used to predict the dissected composition of Angus steers from another experiment in which one group of cattle lost weight. Equation (i) gave useful predictions but equation (ii) did not.

The milk production of 14 Finnish Landrace × Blackface ewes suckling either single, twin or triplet lambs was recorded while they were wholly maintained on a high-quality grazed pasture. Intravenous administration of oxytocin followed by hand milking was used to estimate milk production within 4 days of parturition and then at weekly intervals during a 12-week lactation period. At each milking the milk from each ewe was retained for analysis. Herbage samples for analysis were cut by hand shears at weekly intervals at a height simulating the harvesting by the sheep. In vitro analysis showed a decline in the digestible organic matter in the herbage from approximately 75% in the early stages, to around 67% at the end of lactation. The percentage crude protein in the dry matter of the herbage was variable but tended to increase towards the end of the lactation period. The estimated mean total milk production values were 125, 176 and 193 kg for single-, twin- and triplet-suckled groups of ewes, respectively. Almost all of the difference in total yield between the groups of multiplesuckled ewes occurred in the first 4 weeks of lactation. Analysis of variance showed no significant differences between suckling groups in the concentration of any of the milk constituents. Regression analysis showed significant evidence for differences between the linear and quadratic components of the regressions on stage of lactation for the suckling groups only in respect of daily milk yield, energy and protein production. The concentration of constituents other than lactose was higher in colostral milk but the differences were statistically significant only in respect of energy, total solids and fat. The lactose content of ordinary milk was significantly higher than that of colostral milk. The mean daily live-weight gains of the single- and twin-suckled lambs were significantly greater than that of the triplet-suckled group.

The drying rate of leaves and stem internodes from flowering culms of two varieties of Italian ryegrass (Lolium multiflorum) were measured in the laboratory in controlled conditions of temperature (28 °C), relative humidity (22%) and air speed (40 cm/sec), without treatment, or after being subjected to thermal treatment or to mechanical damage followed by thermal treatment. The two treatments increased the drying rate of leaves and, to a greater extent, stem internodes.

While it cannot be concluded that all treatments that increase crop drying rate will increase the rate for stems more than for leaves, these results are considered to indicate the possibility of devising practical treatments which will. Such treatments could reduce leaf shatter and consequent serious loss of dry matter during the field drying of grass crops.

Grass plots, designed to provide 4 days grazing for three heifers, were divided into four equal sub-plots which were dressed with cow slurry in March at rates between 0 and 100 t/ha. The heifers were put into the plots 7 and 13 weeks after slurry application and were able to choose in which of the sub-plots they spent their time and grazed.

The main effect of slurry on the pasture at 7 weeks was to increase the height of the sward but to decrease herbage dry-matter production. Herbage dry-matter utilization over the 4 days ranged from 94% on the no-slurry sub-plot to only 41% when slurry had been applied at 100 t/ha. The heifers spent most time in and grazed more often in sub-plots with little or no slurry for the first 2 days, but as the grass was eaten down the frequency of grazing on areas with more slurry increased. This was reflected in the amount of grass removed by the heifers from each treatment on each day.

At the beginning of the second grazing, grass height and herbage dry-matter production were both directly related to level of slurry application. The heifers did not distinguish between treatments up to 50 t/ha, but herbage utilization on the 100 t/ha sub-plot was reduced.

The organic-matter intake and the digestibility of grazed tropical pasture mixtures were assessed by the chromic oxide-faecal organic matter-nitrogen technique in five digestion trials. The pasture treatments were designated as: H, Cynodon nlemfuensis var. robustus in a mixture with the legumes Centrosema pubescens and Stylosanthes gracilis; J, Pennisetum purpureum in a mixture with the two legumes in H; K, treatment J plus Panicum maximum; L, a mixture of all the grass and legume species in treatments H, J and K.

The mean organic-matter digestibility of the herbages was determined in indoor digestion trials during the experimental period and varied from approximately 60·0 ± 1·73% to 62·7 ± 4·18% in treatments K and H respectively, with treatments J and L falling between these two values. The mean digestibility of the herbage as grazed, however, was approximately 66·8 ± 1·72, 69·7 ±7·68, 67·1 ± 4·40 and 67·4 ± 4·15 % for treatments, H, J, K and L respectively.

The estimated mean intake of organic matter was somewhat lower, while that of the digestible organic matter was appreciably lower than those reported for animals of corresponding live weights in temperate countries. Grazed pastures were better digested by 4·1 digestibility units in treatment H, by 7·1 in both J and K, and by 5·3 units in L, compared with the indoor digestion trials.

More intensive studies are still needed to warrant any justifiable conclusion as to whether the low intake of herbage by tropical cattle is due primarily to the high crude fibre and the low nutritional values of the pastures, or to the inherent capacity of the animals conditioned to grazing poor·quality pastures.

A method is described of determining the fertilizer P and K requirements of livestock farms from a knowledge of the stock carried and the crops grown on the farm as a whole. Recycling of P and K through organic manures is put on a rational basis and the fertilizer P and K needed to keep soil P and K at an adequate and constant level is easily measured.

A pilot scheme on 100 Northern Ireland farms is testing the method's value for giving advice. It is readily acceptable to advisers and farmers and is enabling substantial savings of fertilizers to be made.