The Agricultural Research Council's system of feed evaluation provides a method of predicting the most profitable ration composition, given information about available feedingstuffs and the values of the parameters in the beef-feed production functions. Because these functions are non-linear, parametric estimation based on average data for a group of animals will give biased results. A method of determining unbiased estimators of the parameters is derived and the magnitude of the bias is shown to be small. Some simplifications of the ARC formulae are proposed.

Little is known about the carcass characteristics of unimproved commercial (or ‘Criollo’) cattle although these still account for a large proportion of slaughter animals in Latin America.

Data were collected from 52 commercial cattle in a commercial slaughterhouse in Monterrey, N.L. Mexico. They included carcass weight, length, total edible meat (carcass fat was negligible), total bone and eleven typical Mexican cuts whose anatomical relations are described. The age of the animals was judged according to dentition and data were stratified using this criterion for analysis. Variations in total edible meat, which averaged 77·4%, were almost entirely accounted for by differences in body weight. Data are presented to indicate amounts of various cuts in the carcasses and some significant differences were demonstrated in values for these cuts among age groups; possible explanations for this were discussed. Prediction equations were calculated to relate total edible meat with the selected cuts and carcass weight and it was found that carcass weight gave the best prediction of total edible meat and could also be used to predict expected weights of individual joints with reasonable accuracy.

Carcass measurements have been used by various authors to predict total edible meat content of carcasses.

Measurements were made on 180 commercial quality cattle of different phenotypes and sexes in a commercial slaughterhouse in Monterrey, N.L. Measurements were carcass weight, length, forequarter depth, side circumference, length of leg, length of forearm, leg shape, area of m.l.d. and total dissected meat. Multiple regressions were computed for both linear and allometric equations using a CDC 3300 computer.

It was found that in both forms of the equation carcass weight accounted for the majority of the total variance (97·0% and 96·8% for the linear and the allometric forms respectively). Various measurements of forequarter depth improved the goodness of fit only slightly as did circumference of side and length of forearm.

Simulated swards of Dactylis glomerata (var. S.37) and Lolium perenne (var. S.23) were grown in large lysimeters or vertical pipes of 15 cm diameter, both sufficiently deep to allow largely unrestricted root development.

Rainfall was excluded, and the effect of a drying cycle on the plant water balance was compared with irrigated controls in a sequence of sampling harvests at increasing soil water deficits.

Leaf water potential (ΨL) fell during the day, both in treatments and controls, to levels which might be expected to reduce extension growth and, frequently, stomatal diffusion. Rapid recovery occurred in the evening to levels which might allow normal functioning of growth processes not dependent on sunlight. Defoliation reduced plant stress and stomatal restriction.

The amelioration of plant water stress appeared to require a reduction in atmospheric evaporative demand, and irrigation had relatively little effect. The possibility is discussed that the major benefits of irrigation are other than through the relief of water stress within the plant. The significance of this is considered in relation to conventional irrigation techniques.

The leaf water status was more sensitive to drought, transpiration was reduced more, and the root system extended more slowly in Dactylis than in Lolium. Consequently, the onset of permanent wilting due to exhaustion of water from the profile was delayed compared with Lolium. It is deduced that this characteristic might enhance the survival of Dactylis in prolonged drought, but prove disadvantageous in terms of growth during short droughts, when reduced stomatal opening might limit CO2 uptake. This would not be an impediment, however, if investigations suggesting that partial closure has a minor effect on CO2 uptake compared with that on transpiration were to be confirmed.

Pigs weighing 25–40 kg were fed either once or twice per day and glucose and insulin concentration in portal and right atrial plasma measured during a 24-h cycle. Feeding resulted in an immediate increase in both portal and atrial glucose concentration. Portal glucose concentration tended to show cyclical changes with the peaks ascending and descending progressively. Under both feeding treatments glucose was absorbed from the gut for 18–20 h/day. Feeding of pure starch resulted in a rise in portal plasma glucose concentration within 10 min, but feeding of pure casein had no effect.

Portal insulin concentration increased immediately on feeding as did atrial insulin concentration, and under both feeding treatments portal and atrial insulin concentration followed a pattern similar to the corresponding glucose concentration. Feeding of pure casein was without effect on the concentration of insulin in either portal or atrial plasma.

Two experiments, which investigated the effect of three seed sizes and three withinrow spacings on the graded yield of the two early maincrop varieties Pentland Crown and Maris Piper, are described and the results discussed.

Relationships were established between yields in various grades and stem population, and are used to explain the response of yield to changes in seed size and spacing. Comparisons between any two levels of the same treatment were affected by the size grade in which they were made. In addition, the tendency towards interactions between variety and seed size and between variety and spacing suggests that comparisons between varieties are affected by the populations at which these comparisons are made.

Data are presented from two experiments which examined the effect of three seed sizes and three within-row spacings on the bulking rate of graded potatoes from the two early mainorop varieties Pentland Crown and Maris Piper.

There were significant linear and quadratic regressions of yield on time and there were significant effects of all main treatments on the bulking rate of the crop. Differences in yield between the levels of each treatment depended upon the time of harvest and the size of tubers considered.

Satisfactory comparisons of the incidence of virus yellows in sugar-beet fields or experimental plots with different amounts of N fertilizer can be made from visual symptoms early in the growing season, but not later because dressings of N fertilizer may then mask or delay the appearance of symptoms. Sugar-beet plants in the field infected with beet mild yellowing virus (BMYV) are less likely to show symptoms than those with beet yellows virus (BYV), and plants with BMYV in the glasshouse often fail to show clear symptoms.

Crop yield will be affected by the spread of viruses and colonization of plants by aphids, which in turn are affected by such factors as plant density, nitrogen supply and irrigation. The presence or absence of virus diseases and of aphids should therefore be considered during studies on the effects of these agronomic factors on the growth and yield of sugar beet. Where ample rather than little N fertilizer is used a small increase in the percentage of plants infected with yellows can be expected, and aphids will be more numerous, if plants are not treated with insecticide. Irrigation may also increase yellows incidence (e.g. from 16% to 20% of plants at Broom's Barn in 1967), but any loss of potential yield from increased virus incidence will be small compared with that gained from the use of fertilizer or irrigation. However, plant density can appreciably affect yellows incidence. For example, at Broom's Barn in 1972, 51% of plants in crops with 17500 plants/ha contracted BMYV but only 15 % of plants in crops with 126500 plants/ha. The less dense crop lost 3–4% more of its potential yield due to yellows than the dense crop; this represents a difference due to virus of about 0·25 t sugar/ha.

Five successive trials were conducted using eight adult rams (Sudan desert sheep) to study the effect of restriction of water intake on some aspects of digestion and nitrogen metabolism. The feeds used in this study were berseem hay (Medicago sativa), lubia hay (Dolichos lablab), maize hay (Zea mais), a concentrate mixture, and dry desert grasses (hummra) (a mixture of Dactyloctenium aegyptium, Schoenefeldia gracilis, Eragrostis pilosa, Aristida funiculata and Aristida spp.).

Restriction of water did not affect the digestibility coefficients of organic matter, crude protein and crude fibre significantly. The digestibility coefficient of ether extract was significantly reduced whereas that of nitrogen-free extract was slightly higher when water was restricted.

The concentrations of ammonia and volatile fatty acids in the rumen and of urea in the blood were recorded before and 3 h after feeding. Increases in rumen ammonia and blood urea nitrogen concentration were reduced by water restriction except when hummra was fed.

Restriction of water intake also slightly increased the in vitro rate of fermentation of rumen contents which is taken as a measure of microbial activity in the rumen, and the retention of nitrogen. These results are interpreted as indications of more efficient nitrogen utilization under conditions of water restriction.

There were no significant effects of the treatments on changes in the concentration of volatile fatty acids.

The significance of these findings in relation to the management of desert sheep in the arid parts of the Sudan is discussed with special reference to the effect of the level of dry-matter intake on nitrogen balance.

Specialized techniques, previously used in surgically prepared goats, which simultaneously measure udder metabolism (arteriovenous difference of milk precursors x udder blood flow) and the whole body turnover of the milk precursors, have been successfully transferred to dairy cows. Methods of obtaining representative samples of arterial and mammary venous blood and of measuring udder blood flow are described.

The rates of entry into the circulation, as determined by isotope dilution, of glucose, acetate and plasma free fatty acids were 3·3–4·0, 1·7–2·1 and 0·5 kg/day respectively. Acetate and glucose contributed 32–50 and 4–11% respectively of the total CO2output by the animal.

Measurement of the uptake of precursors of milk constituents and their transfer into milk showed that there were substantial arteriovenous differences of glucose, acetate, triglyceride and β-hydroxybutyrate which were not significantly different between breeds or related to milk yield. Isotopic and balance data confirm that glucose is the main precursor of lactose and that the oxidation and transfer of glucose into lactose accounted for 69–98% of the glucose entry rate. As in the goat, plasma triglycerides and blood acetate accounted for 35–80% and 25–50% of the milk triglycerides respectively. Propionate was extracted from plasma but the uptake was only about 8% of the value for acetate.

There was no net arteriovenous difference of phospholipids, cholesterol esters or free fatty acids, but the fall in specific radioactivity of free fatty acids across the mammary gland indicated there was an exchange of free fatty acids between plasma and mammary tissue. In agreement with previous findings, acetate contributed to all the milk fatty acids up to a chain length of C14 and part of the C16 fatty acid. Plasma triglycerides contributed to the remainder of the C16 fatty acid and all the milk fatty acids with a chain length of C18 or higher.

In contrast to the lactating goat, cow plasma contained very few chylomicrons. The majority of the triglycerides taken up by the udder were derived from the lowdensity lipoprotein fraction.

The essential amino acids were extracted from blood in amounts sufficient to account for the essential amino acids secreted into milk protein. Although the plasma level of methionine was low, 52–72% of the material reaching the mammary gland was taken up. The uptake of arginine was far in excess of the requirement for milk protein synthesis.

The effects of changing to a high starch: low roughage diet have been studied in two Friesian and two Jersey cows, surgically prepared for the simultaneous study of udder metabolism (arteriovenous difference x udder blood flow) and whole body turnover of milk precursors (isotope dilution).

In the Friesian cows milk fat concentration was lower on the high starch diet but in the Jerseys fell only slightly in one animal. In both Friesians and in the one Jersey these changes were accompanied by an increase in total rumen VFA concentration. Rumen acetate concentration did not change but propionate doubled. Thus this confirms that the usually reported fall in ‘acetate:propionate ratio’ is due to a rise in propionate production rather than due to a fall in acetate production.

There were significant falls in the blood concentrations of acetate and β-hydroxy-butyrate. The rate of extraction by the udder of acetate and β-hydroxybutyrate did not change but triglyceride extraction fell. Therefore since udder blood flow did not alter the uptake of all three fat precursors fell.

The entry rate of glucose into the circulation and its contribution to total body CO2 increased. The entry rate and contribution to CO2 of acetate decreased but this was probably mainly due to a fall in endogenous acetate production by the body tissues. Plasma FFA concentration showed little change but the entry rate of palmitate fell on the high starch diet. There was also an increased proportion of unsaturated and trans fatty acids in the plasma and milk triglycerides.

Twenty-four Friesian bull calves purchased at 10 weeks old were reared in three groups to slaughter at 420 kg live weight. One group (BB) was fed on a barley-concentrate diet to grow rapidly at 1·41 kg/day, a second (GG) was fed on dried grass cubes to grow slowly at 0·97 kg/day and the other (BG) was fed to grow rapidly to a live weight of 250 kg and thereafter at a slow rate, overall 1–20 kg/day.

Efficiency of food conversion, energetic efficiency and efficiency of dissectible muscle production were best for BB animals, followed by BG and then GG. Changes in carcass composition mainly resulted from differential fat deposition, and bone/ muscle development was allometric in relation to fat-free empty body mass. The development of certain characteristics, the head, depth of forequarter, pelvic length and tibia length followed a time scale and may have reflected the priority for nutrients of some entire male characteristics irrespective of body size.

In addition to being most efficient, the fastest growing bulls yielded carcasses with sufficient fat deposition to meet grading requirements, whereas both the slower growing groups of bulls were penalized in this respect.

Eight mature female sheep were offered a ration which maintained body weight constant during a 20-week period. During the final 10 weeks a comparison was made in each animal of the pattern of equilibration and urinary losses of tritiated water during 8 h after dosing by four different routes. These were intravenous, intraperitoneal, intraruminal and a combination of the intraperitoneal and intraruminal routes. Tritiated water spaces were calculated from (a) the 8-h plasma specific activity and (b) by extrapolation to zero time of the plasma specific activities during the 7 days after injection. At the end of the experiment the fat and water contents of the bodies of the sheep were determined directly.

Complete equilibration of tritiated water between plasma and rumen water was not achieved in all animals 8 h after intravenous or intraperitoneal injection but was when the rumen was primed by the combination of intraperitoneal and intraruminal dosing. After intraruminal dosing equilibration was not achieved in any animal within 8 h of dosing.

Urinary losses of marker were lower after intraruminal dosing but otherwise averaged 4–5 % of the dose/1 urine. This was equivalent to 0·3–6·7% of the dose for individual sheep.

Errors resulting from incomplete equilibration and urinary loss of marker did not influence the efficiency of prediction of total body water from tritiated water space. The multiple correlation coefficient relating body fat with empty body weight and its water content was very high (r = 0·99). Errors introduced into this relationship by the inclusion of gut water in the prediction equations were apparently of a similar magnitude to those resulting from the errors in the estimation of tritiated water space.

The extrapolation method for the determination of tritiated water space was shown to have the same accuracy as equilibration techniques under these controlled dietary conditions.

Experiments were conducted to study the effect of plant injection with growth regulators on the dormancy of onion bulbs cv. Elba Globe. Application of abscisic acid induced early senescence of the leaves and prolonged the rest period of the bulbs. This effect was partially overcome by subsequent applications of gibberellin, auxin or cytokinin and totally overcome with the application of a mixture of the three hormones. Maleic hydrazide application prolonged the rest period by inhibiting both sprouting and rooting of the bulbs throughout the storage period. This inhibitory effect was not overcome by the subsequent application of auxin, gibberellin, kinetin, or their combinations. Ethephon application increased rooting of bulbs and partially overcame the effect of abscisic acid on dormancy.

The largest yields of potatoes in the Woburn Reference Experiment were obtained by giving both farmyard manure (FYM) and fertilizers, rather than fertilizers alone; an explanation was sought in experiments made on the coarse sandy loam there from 1968–71. Each year, single and double amounts of NPK fertilizer (supplying 250 or 500 kg N/ha plus P and K) were incorporated, either deeply or shallowly, into the seed bed. From 1969, FYM also was tested at rates giving the same amounts of N, similar amounts of K, but more P than the fertilizers; it was tested both alone and with fertilizers.

FYM was less effective than fertilizer when given alone. The combination of FYM and fertilizer gave a larger yield than the single amount of fertilizer and a larger yield than the double amount of fertilizer incorporated shallowly, but a smaller yield than the double amount of fertilizer incorporated deeply, which gave the largest yield each year.

The NPK contents of the potato tubers were used to construct nutrient balance sheets; large residues of N, P and K remained in the soil after harvest. Winter wheat was grown to value these in 1971 and 1972. Fertilizer residues increased only straw yields, but FYM residues increased yields of both grain and straw. Both kinds of residues were less effective than freshly applied N, so most of the N leached during winter.

The yield of saleable tubers was increased, not decreased, by the double amount of fertilizer.

Three factorial experiments made in 1969 on Northern Ireland pastures to measure effects upon yield and mineral content of 0, 180 and 360 kg N, 0, 30 or 60 kg P and 0, 150 or 300 kg K/ha/year, both with and without 1380001 slurry/ha, were continued on the same sites with the same treatments in 1970 and two of them were continued again in 1971.

Responses to nitrogen in the second and third seasons were similar to those of the first season. There was no evidence that large nitrogen dressings plus slurry were causing nitrogen to accumulate in the soil.

Repeated cutting of herbage given neither fertilizer potassium nor slurry was beginning to reduce both yield and the potassium content of the herbage in the second and third years. Giving fertilizer potassium prevented these losses, but the potassium in the slurries was less effective because it did not maintain the potassium content of the herbage. Reasons for, and implications of this effect are discussed.

There was no evidence that soil phosphorus reserves were becoming depleted, when judged by the % P in herbage receiving neither fertilizer nor slurry even after the herbage had been cut and removed for two or three years. As there was no immediate need for fertilizer phosphorus, the P in the slurries, even though slower acting than that in mineral fertilizers, seemed suitable for maintaining the phosphorus status of these pasture soils.

Observations on the time of development of the permanent anterior teeth in a herd of Friesian female cattle (heifers + cows) are described. The animals were examined at approximately monthly intervals. A modified longitudinal survey method was employed. A table is presented of the maximum and minimum (i.e. the range), mean and median ages for the stages of development for each permanent pair of teeth. The stages were defined as: one of permanent pair present and/or one/both temporary teeth absent, both permanent teeth emerging, ¼ up, ½ up, ¾ up and fully up. A large amount of variation was found in the ages for each stage of development in individual animals. Tables are included for the time taken for a pair of permanent teeth to pass from first to complete emergence, the time a pair of teeth were fully up before any further development was observed and the time taken between a tooth being at one stage in one pair of teeth to the same stage in the succeeding pair of teeth.

Three experiments studied the behaviour of pigs which were brought together for brief periods of observation on successive days. Two distinct patterns of aggressive behaviour were observed, one involving biting and the other involving butting. Biting was common when the pigs first met, and butting seemed to replace biting in some cases. Pairs of pigs which had no previous contact frequently showed a straight forward type of dominance with one pig performing almost all the biting and butting; among well-acquainted pairs, however, the relationships were frequently more complex.

Of all the experimental manipulations, familiarity between two animals had the most profound effect on the behaviour. Biting, but not butting, was reduced if the pigs were housed in neighbouring pens, or if they had previously shared the same pen. Biting was almost eliminated, and butting was reduced, if the pigs lived together throughout the time of the observations. There were no differences between females and castrated males, or between individually-housed and group-housed animals in either type of behaviour.

Pigs which were subjected to repeated biting generally became less active, refraining from some social and non-social activities. Butting did not appear to have similar effects on the recipient animals.

The experiments illustrated some complex social interactions involving a large number of distinct social activities. In this light, the usefulness of such broad terms as ‘aggression’ and ‘dominance’ is discussed.

When one or two leaves were removed out of the three or sometimes four present on each tiller of five genotypes of perennial ryegrass grown in nutrient solution, it was found that the relative growth rate (RGR) was not much less than that of untreated plants. The removal of lower leaves had no effect on RGR. Removal of all leaf blades depressed RGR. It is suggested that the results obtained indicate that the plant has the capacity to compensate for loss of leaf tissue by increased activity in the remaining leaves. Leaf appearance rate and tiller production were found to be the attributes most sensitive to the defoliation treatments imposed, and the degree to which leaf appearance rates were affected by defoliation was found to be a good indicator of the regrowth capacity of the different genotypes. Evidence was obtained linking high regrowth potential with high relative increases in the proportion of plant material allocated to new shoot growth.

The relationships between mid-silking date, mid-maturity date, spread of silking and spread of maturity were studied in four maize hybrids. Mid-maturity date and spread of maturity were positively related to mid-silking date. The spread of silking ranged from 13 to 18 days and the spread of maturity from 34 to 47 days in different hybrids. Grain moisture content at mid-maturity ranged from 40 to 35%. It was concluded that the common practice of harvesting grain crops at 40% dry matter is likely to result in appreciable loss of yield: variation in the proportion of mature kernels when the grain has reached 40% moisture may account for the large season to season variation in yield observed in commercial crops. The potential benefits of early flowering hybrids are briefly discussed.