Showing papers in "The Journal of Agricultural Science in 1976"

Analysing data with repeated observations on each experimental unit

Abstract: Split-plot (or split-block) analyses are commonly applied to experimental results where several successive observations of the same variable have been recorded on each experimental unit. The assumptions required for such analyses receive scant attention and it often seems unlikely that these assumptions would be satisfied in experimental situations. Five sets of results are presented to support this proposition. An alternative analytical approach is suggested in which contrasts over time are analysed; such a method is always valid, computationally simple, and readily interpretable, and may also be used to gauge the validity of the split-plot analysis.

Intake and utilization of food by growing lambs with parasitic damage to the small intestine caused by daily dosing with Trichostrongylus colubriformis larvae

Abstract: Four groups of eight lambs, 4 months of age and reared parasite-free from birth, were used to investigate the effect of the intestinal parasite Trichostrongylus colubriformis on the intake and efficiency of utilization of food, using balance trial and comparative slaughter techniques. One group (CI) was killed initially as control. Two further groups (ALC and ALI) were offered ad libitum a complete ruminant diet. The ALI group was dosed orally each day for 14 weeks with 2500 infective larvae. Sheep in a further group (PF) were individually paired to members of the ALI group, and given the same amount of food as their pair. Balances of nitrogen, Ca and P and the digestibility of dry matter and energy were determined for the ALI and PF groups during weeks 6–7 and 12–13 and after 98 days of infection the sheep were killed. The bodies of these and the CI and ALC sheep were analysed for water, fat, nitrogen, Ca and P contents.Parasitism reduced food intake over the whole experiment by 9%, but had no effect on the digestibility of energy or nitrogen. At the first trial the N balances of the ALI group were inferior to those of the PF group due to increased urinary N excretion, but there was no difference at the second trial. Ca and P balances of the ALI group tended to be inferior to those of the PF group at both trials. The weight gain of the ALI sheep was only 50 % of that of the PF sheep with the same digestible energy and protein intakes. The protein content of the gain in empty body weight of the ALI sheep was 80 g/kg compared with 112 and 124g/kg in the ALC and PF groups, respectively. Possible causes of the poor protein anabolism are discussed.The gross efficiency of utilization of metabolizable energy for growth was calculated to be 13·3 % in the ALI sheep, compared with 26·2 and 24·2 % respectively, in the ALC and PF groups. It was not possible to determine whether this was due to change in maintenance requirement or in efficiency of fattening.The Ca and P content of the skeletons of the ALC and PF sheep increased by 55 % during the 98-day period, while no net change occurred in the ALI sheep. It was concluded that this was caused by an induced mineral deficiency resulting from parasitic damage in the small intestine.

The effects of a granular nitrogen fertilizer and a foliar spray of urea on the yield and bread-making quality of ten winter wheats

Abstract: Ten winter wheat varieties, representing a range of milling and bread-making quality were grown in a split-plot field trial with two levels of irrigation and three levels of nitrogen fertilizer Grain yield was increased by irrigation and by fertilizer treatments Application of 90 kg N/ha applied in granular form increased yield by 124 and 61% and grain protein by 130 and 337% for the irrigated and non-irrigated plots respectively A further 45 kg N/ha applied as an aqueous foliar spray of urea (0125 kg/1) at anthesis increased protein by 124% for the irrigated plots and by 88% for the non-irrigated plots with little effect on yield The varieties differed significantly in yield and protein content, resulting in negative regressions of yield and protein content at each N treatment The production of protein (weight N/unit area) was similar for all varieties, but flour extraction was reduced by the urea treatment Varietal differences in flour extraction were stable and not correlated with either 1000-grain weight or test weight Loaf volume was increased by the granular N fertilizer but not by the urea spray, despite the increase in flour protein and a decrease in flour α-amylase activity, indicating that applications of nitrogen after anthesis are likely to be later than the optimum for improving bread-making quality

The effect of herbage allowance on herbage intake and performance of lambs grazing perennial ryegrass and red clover swards

Abstract: The effect of daily herbage allowance on herbage intakes and growth rates lambs grazing perennial ryegrass and red clover was investigated in two experiments. Herbage allowances defined as g herbage D.M./kg live weight (LW)/day were controlled by varying the areas of plots grazed for 2 days by groups of six lambs.In the first experiment five herbage allowances in the range 20–120 g D.M./kg LW/day were offered on two areas of a perennial ryegrass (cv. S. 23) sward that received nitrogen fertilizer applications of 39 or 78 kg N/ha/28 days. In the second experiment five herbage allowances in the range 30–160 g D.M./kg LW/day were offered on perennial ryegrass (cv. S. 23) and red clover (cv. Hungaropoly) swards.Asymptotic curves were fitted to describe the relationship between herbage allowance and daily intake of herbage. In Expt 1 nitrogen fertilizer rates did not affect the yield of herbage or animal performance. In Expt 2 intakes were higher on the clover sward than on the ryegrass sward at the higher herbage allowances.The asymptotic curves to describe the relationship between herbage allowance and growth rate of lambs differed widely between periods. Growth rate of the lambs increased linearly with increase in digestible organic matter intake. Live-weight gain per unit of digestible organic matter intake was higher on the red clover than on the ryegrass.The conclusion is drawn that if the herbage present to ground level is not more than three times the daily intake of the animals, intake of herbage of the animals may bo restricted.

Variation in nutrient content of feedingstuffs rich in protein and reassessment of the chemical method for metabolizable energy estimation for poultry

Abstract: A series of five metabolism trials was made to determine apparent nitrogen digestibility and metabolizable energy (ME) contents of protein rich feedingstuffs. The mean nitrogen digestibilities of fish meal, groundnut, mustard, sesame and cottonseed cakes were 66, 69, 68, 57 and 40%, respectively. Corresponding values for metabolizable energy values were 1820, 2460, 2330, 1870 and 1530 kcal/kg, respectively. The metabolizable energy contents of coconut cake, niger cake and blood meal were 1190, 2360 and 2190 kcal/kg, respectively. The quantity of protein, its digestibility and crude fibre content in the cakes are the prime factors for this trend in MB. Simple and multiple regression equations were derived from biologically assayed metabolizable energy and chemically analysed energy-yielding nutrient contents of the feedingstuffs. The simple regression equation is:ME kcal/kg = 32·95 (% crude protein + % ether extract × 2·25+ % available carbohydrate)–29·20.The multiple regression equation is:ME kcal/kg = 370·29 + (24·47 × % crude protein)+ (65·77 × % ether extract)+ (44·07 × % available carbohydrate)- (8·15 × % crude fibre).The correlation coefficients of simple and multiple regression equations were 0·72 and 0·73, respectively, indicating that there is very little advantage for prediction in using the multiple regression equation. The usefulness of the equation for routine checking of poultry feeds for ME is apparent since the nutrients required to predict metabolizable energy can be analysed within a short period of time.

Evaporative water loss in domestic fowls and its partition in relation to ambient temperature

Abstract: The rate of evaporative water loss has been studied in domestic fowls in the ambient temperature range from 0 to 40°C.Results for whole-body evaporation were similar when obtained by the open-flow and direct-weighing methods. At low levels of absolute humidity the rate increased by 0·03 mg/(g.h.°C) from 0 to 22 °C and by 0·17 mg/(g.h.°C) from 23 to 40 °C. Wholebody evaporation decreased with rising ambient water vapour pressure by 0·7 mg/(g.h.kPa).Cutaneous water loss was greater than respiratory water loss below 21 °C; it accounted for 78% of whole-body evaporation at 0 °C, falling to 25% at 40 °C.The rates of respiratory and whole-body evaporation could both be expressed as linear functions of respiratory frequency.

The digestion of frozen and dried grass by sheep

Abstract: S. 24 perennial ryegrass, containing 2·9 g nitrogen/100 g D.M.>, was conserved by freezing (to represent the fresh material) or by drying. Three dehydration treatments were imposed, comprising low temperature (inlet temperature 145 °C) high temperature (inlet temperature 900 °C) or oven drying (100 °C for 18 h) and in addition part of the high temperature dried grass was treated with formalin (1 g/100 g crude protein) prior to feeding.The digestion of the energy and nitrogen components of all diets was investigated using sheep fitted with re-entrant cannulae at the proximal duodenum and terminal ileum.Dehydration and formalin of the grass reduced nitrogen solubility and apparent energy and nitrogen (P < 0·001) digestibilities but led to increased quantities of nitrogen entering the small intestine (P < 0·01) compared with the frozen diet. A significant relationship describing nitrogen transformations was established: Y = 165–1·13X (r = –0·98, P < 0·001), where Y is g nitrogen entering the small intestine per 100 g N consumed and X is dietary nitrogen solubility. All dried diets showed increased losses of nitrogen within the small intestine compared with the frozen diet, the largest values being observed on the oven-dried and formalin-treated diets.Neither total VFA production within the rumen nor overall cellulose digestibility was influenced by dehydration, but on the formalin-treated diet there was a marked shift of cellulose digestion from the rumen to the caecum and colon compared with the other diets, associated presumably with the large reduction in protein solubility on this diet.Dehydration improved the efficiency of conversion of ruminally digested energy to VFA energy within the rumen, and in relation to the nature of the total absorbed nutrients a significant relationship was established:Y = 30·97–0·22X (r = –0·98; P < 0·001),where Y is g digestible crude protein lost in the total intestines per 100 g digestible organic matter intake and X is dietary nitrogen solubility.

In situ estimation of root length at natural soil profiles

Abstract: A thin layer of soil was washed from a smoothed soil profile and the length of the roots visible at the profile wall estimated. A grid net was used to count every visible part of a root which was nearly 5 mm long. Roots which were longer than 5 mm were counted more than once. This improvement of the traditional trench profile method provides an estimate of the root length in a soil volume.

A technique for determining the proportion of C3 and C4 species in plant samples using stable natural isotope's of carbon

Abstract: A technique is described which uses the ratio of the natural 12C and 13C isotopes of carbon to calculate the proportions of Calvin pathway (or C3) species and C4 dicarboxylic acid pathway (or C4) species in mixed samples of shoots, roots or seeds. Mean percentage of a particular component can be predicted to within ± 2% of actual values with average standard errors of less than 1% with two component mixtures under good conditions using threefold replication. The technique is particularly useful for estimating the proportion of C3 and C4 species in samples of visually indistinguishable, intermingled root systems from mixed field communities or from competition experiments. The proportion of C3 and C4 species in both oesophageal fistula and feed samples can be obtained using this technique, and it is proposed that data from fistula and pasture samples could be used to determine the extent to which animals selectively eat C3 or C4 species. The advantages and disadvantages of the technique are discussed.

Equations to predict the leaching of nitrate uniformly incorporated to a known depth or uniformly distributed throughout a soil profile

Abstract: Equations to predict the leaching of nitrate either uniformly incorporated to a known depth or uniformly distributed in field soils can be reduced to the approximate form:where f is the fraction of nitrate leached below h cm in a soil of field capacity Vm (% by volume) after P cm of drainage has passed through the profile. If nitrate is initially incorporated uniformly to a depth of w cm, then x = h – ½w(where h ≥ w); if nitrate is distributed uniformly throughout the whole profile, then x = ½h. For surface-applied nitrate x = h (Burns, 1975).Observed mean displacements in published experiments have been compared with predictions from the equations and from equations in which the mean movement of nitrate and water are assumed equal. The new equations give better agreement with the observed data.

In vitro digestibility of the testa in tannin-free field beans (Vicia faba L.)

Abstract: The seed-coat of all white-flowered varieties of Vicia faba and segregants tested was free of tannin. In two field trials, the whole grain of white-flowered varieties wassignificantly higher in in vitro digestibility of the dry matter, on average 4·7% higher, than coloured-flowered varieties of similar seed size. In subsequent trials where the testa and cotyledon were examined separately, this difference was shown to be largely due to a mean D value (digestibility of the organic matter) of the testa in tannin-free varieties of 56·4% compared with 17·2% in tannin-containing varieties. Seed size was positively correlated with D value but not because of differing proportions of testa.Differences between varieties in acid-pepsin solubility and protein content of the testa were much smaller and not associated with presence of tannin. The testa colour of some tannin-free F2 plants was a darker shade of grey than either parental population. An inbred line completely lacking in anthocyanin in flowers and stem but with the normal black wing spot had tannin in its testa.Grains of peas from the coloured-flowered variety, Minerva, reacted to a tannin test wheieas those from white-flowered varieties, Greenshaft and Flavanda, did not.The case for breeding further tannin-free varieties of Vicia faba is discussed.

Prediction of the lean content of lamb carcasses of different breed types

Abstract: Carcass data for 424 castrated male lambs, comprising seven breed-type groups, were used toevaluate a series of linear measurements, subjective scores and the lean content of sample joints as predictors of percentage lean in carcass. The groups represented the main types of British lamb and mean carcass weights ranged from 12·8 kg (Welsh Mountain) to 20·8 kg (Lowland Longwool). Lambswere selected from commercial abattoirs to cover the ranges of fatness and conformation normally found in practice within each group. The pooled within-group S.D. for percentage lean was 3·70 and theoverall S.D. (ignoring groups) was 3·96.Predictors were compared in terms of precision and the stability of their prediction equations. Of the characteristics measured on the intact carcass, subjective scoring of external fatness gave the most precise prediction both within groups and overall (R.S.D.within = 2·82, B.S.D.overall = 3·17). Fat thickness over the eye muscle (0) was the best predictor among those taken on the quartered carcass (R.S.D.within = 2·76, R.S.D.overall =3·00). The most precise individual predictors were percentage lean in the best end neck and shoulder joints (R.S.D.within = 1·51 and 1·59 respectively). Among pairs of predictors not involving dissection, the combination of C and percentage kidney knob and channel fat in the side gave the most precise prediction (R.S.D.within = 2.51, R.S.D.overall = 2·68). The stability of the prediction equations between groups tended to increase with the precision of the predictors. Among the more precise predictors, the equation for percentage lean in the leg was a notable exception, being particularly variable from one group to another.

The nutrition of the early weaned lamb. IV. Effects on growth rate, food utilization and body composition of changing from a low to a high protein diet

Abstract: About sixty male lambs were fed ad libitum from 6 weeks of age on low- or highprotein diets based on barley or barley and fishmeal and containing respectively 120 and 200 g crude protein/kg dry matter. Some lambs were changed from one diet to the other when they reached 28 kg live weight. All were slaughtered as they attained a predetermined series of live weights ranging from 20 to 75 kg.Throughout the experiment, rates of live-weight gain were substantially higher with the high-protein (HP) than with the low-protein (LP) diet, but were highest after a change from low to high protein (LHP). The feed consumption of the LHP lambs did not exceed that of the HP lambs, but the former showed a substantial superiority in feed conversion ratio at the same live weight.At similar empty body weights, the LP lambs contained more fat and less water in the empty body than the HP lambs. Although the percentage differences decreased at higher weights, differences were still apparent at 70 kg live weight.The LHP lambs showed dramatic and rapid changes in body composition, particularly in water and fat content. By 40 kg live weight, their composition approached that of the HP lambs.The ratio of water to protein was consistently lower for the LP lambs. The ratio of protein to ash also differed between LP and HP lambs. It was initially highest for the HP lambs, at about 40 kg live weight it was the same, and at 70 kg live weight it was highest for the LP lambs.The ash content of the LHP lambs remained virtually constant during the period of rapid growth and rapid deposition of water, protein and fat which took place immediately after the change of diet, and only showed compensatory increases after 35 kg live weight. This finding was supported by the pattern of changes in weight and specific gravity of the femur and tibia + fibula.Use was made of separate relationships between live weight and body composition for the LP, HP and LHP lambs to estimate rates of accretion of crude protein, fat and water in the empty body. There was a particularly striking increase in the rate of accretion of water immediately following the change of diet. There was an increase in the water content of empty-body gain and a reduction in the ratio of gain in fat to gain in protein.Derived estimates of the ratio of metabolizable energy intake above maintenance to the energy content of empty-body gain gave some suggestion of an improvement in efficiency of utilization of metabolizable energy for gain following the change from low to high protein. It is concluded however that the improvement in food conversion ratio following the change is attributable mostly to difference in the composition of gain.

Urinary allantoin excretion and digestible dry-matter intake in cattle and buffalo

Abstract: A linear relationship between the amount of allantoin excreted in the urine of cattle and the digestible dry-matter intake, has been found for cattle fed different roughage diets. The relation was also linear for buffalo although they excreted less urinary allantoin than cattle at the same level of digestible dry matter intake. It is postulated that the relationship arises because of the contribution that degraded microbial nucleic acids make to the excreted allantoin in the urine of cattle.

Yield potential in a dwarf spring wheat and response to crop thinning

Abstract: SUMMARY Experiments with wheat describing the effects of crop thinning on grain yield and its components are presented. These were carried out over 5 years in northwest Mexico, using a high-yielding dwarf spring-wheat variety (Triticum aestivum cv.' Yecora 70') grown under irrigation and high fertility. It was shown that thinning largely relieved competition for light, thus increasing photosynthate levels in the plants remaining after thinning. The objective was to evaluate this simple technique as a guide to understanding when grain yield and its components were determined and, in particular, the extent to which post-anthesis photosynthate supply limited yield. There were major responses in grain yield with thinning between about 50 and 100 days after seeding, and in number of spikes and of grains with thinning between 50 and 90 days (50 % anthesis was reached at 87 days). Number of spikelets per spike showed small responses to early thinning (before 50 days). Number of grains/spikelet and kernel weight snowed positive responses to thinning between 65 and 90 days, and 90 and 115 days, respectively. These results agreed with adjacent shading and CO2 fertilization studies but, because of certain difficulties in interpretation of responses, pre-anthesis thinning was not considered a very useful technique. Anthesis thinning was carried out on 21 separate crops: the kernel weight increase relative to the unthinned control ranged from 6 to 41% , averaging 20%. Anthesis thinning led to increases in stem weight during the first half of the grain filling period, followed by increases in grain growth rate in the latter half. The increase in final kernel weight was greater with higher temperature and lower radiation during grain filling; these variables explained 64 % of the variation in kernel weight response. It is suggested that the kernel weight response does indicate the degree of photosynthate limitation during grain filling, showing reasonable agreement with adjacent shading and COa fertilization studies. It was concluded that anthesis thinning, because of its relative simplicity, is a useful technique. Implications for yield improvement in Yecora of the results provided by this technique are discussed.

A comparison of body composition and tissue distribution of Friesian and Angus steers

Abstract: Fourteen Friesian and 13 Angus steers, grown at pasture, were selected so that their carcass weights fell evenly throughout the range 200–300 kg. The right half of each carcass was dissected into muscle, fat, bone and fascia and tendon, and the left half boned-out and fat trimmed into retail cuts. A step-wise multiple regression procedure, including a pseudovariable for breeds, was used to compare compositional components on a common weight basis.Angus, at the lower end of the live-weight range, had heavier empty bodies than Friesians; at the heavier end of the live-weight range, this was reversed. This relationship between live weight and empty body weight was due to variation between breeds in the weight of contents in the fore stomachs but not the intestines.When compared at either the same live weight or the same empty body weight, Angus had more hot carcass than the Friesians (8·0 and 8·4 kg, respectively). There was no difference between breeds in loss of carcass weight in the 24 h post-slaughter.There was no breed difference in weight of blood, head, kidney and channel fat, kidneys, liver, diaphragm, heart, lungs, tail or fore-stomachs, when compared at the same offal weight. The feet and intestines were, respectively, 0·55 and 2·43 kg heavier for Friesians than for Angus at the same offal weight, but the pizzle was 0·11 kg lighter. Hide weight was greater in the Angus at all offal weights, with the difference between breeds being 0·016% of (offal weight).There was no difference between breeds in the weight of muscle or the weight of fascia and tendon when compared at the same dissected side weight; however, the Angus had 4·8 kg more fat and 3·0 kg less bone than the Friesians at the same dissected side weight.When compared at the same muscle weight the Friesians had 1·04 kg more proximal hind-limb muscles, 0·30 kg more proximal fore limb muscles, but 0·74 kg less abdominal muscles than the Angus. At all dissected muscle weights the Angus had a greater weight of muscles of the neck and thorax, and this difference increased with increasing weight of dissected muscle. The Friesians also had 1·52% more of their muscle as ‘expensive muscle’. There were no breed differences in the distribution of any other muscle groups.There was no breed difference in the distribution of dissected fat between subcutaneous and intermuscular depots when these were the only fat depots considered. However, when kidney and channel fat was included in the total dissectable fat of the carcass, Friesians had 22·4 % more kidney and channel fat, the same weight of intermuscular fat and less subcutaneous fat than the Angus at the same total dissected fat weight.Friesians tended to have more of their bone weight in their legs (humerus, femur, tibiar–tarsus, radius–ulnar–carpus) and Angus more in their thoracic region (thoracic vertebrae and ribs, scapular and sternum-costal cartilages).At the same retail side weights there was no difference between breeds in the weight of fat-trimmed, boned-out, retail cuts; however, the Friesians had 3·3 kg more retail bone than Angus, but 2·3 kg less fat trim and 0·46 kg less sausage mince.There was no difference between breeds in the distribution of retail bone or of fattrimmed, boned-out cuts between the forequarter and hindquarter. However, the Friesians had 13·2 % more fat trim in the hindquarter. Friesians had 0·27 kg more retail cuts located in the rump but 0·80 kg less in the loin, when compared at the same weight of retail cuts. Also, the Friesians had more of their retail cuts as topside, thick flank and foreshin. There were no other differences between breeds in the distribution of retail cuts.

Density and row spacing effects on irrigated short wheats at low latitude

Abstract: During four winter seasons eight spacing and density experiments were made under irrigated high fertility conditions in north-west Mexico (latitude 27° N). Experiments included various Triticum aestivum and T. durum genotypes of spring habit, short stature derived from Norin 10 genes, and contrasting plant type. Measurements included dry-matter production, photosynthetic area index, and light interception during one experiment, total dry matter at maturity in most others and grain yield and its numerical components in all experiments.Grain yield and most other crop characters were unaffected by row spacings within the range 10–45 cm interrow width. The optimal seeding density for maximum grain yield was 40–100 kg/ha (80–200 plants/m2). Yield reductions at lower densities (20, 25 kg/ha) were slight and accompanied by reduced total dry-matter production. Yield reductions at higher densities (160–300 kg/ha) were also slight and were associated with more spikes/m2 but fewer grains/m2 and reduced harvest index. It is suggested that lower than normal preanthesis solar radiation or weather conditions leading to lodging can magnify these yield depressions at higher densities.Measurements showed rapid approach of crops to 95% light interception, reached even at a density of 50 kg/ha within 50 days of seeding. It is suggested that provided this occurs before the beginning of substantial dry-matter accumulation in the growing spikes (60 days after seeding) there will be no loss of grain yield with reduced seeding density. Results point to a ceiling photosynthetic area index for maximum crop growth rate although there was a tendency for rates to fall at very high indices (> 9). This tendency was associated with very high density, high maximum numbers of shoots, poor survival of shoots to give spikes (< 30%) and reduced number of grains/m3;. The relatively low optimal densities seen here may be characteristic of genotypes derived from Norin 10.Genotype × spacing, genotype × density and spacing × density interactions were generally non-significant and always small. There was a tendency for the presence of non-erect leaves or branched spikes to reduce the optimal density, but large differences in tillering capacity had no influence. Differences in lodging susceptibility can however lead to substantial genotype x density interactions.

Effects of pre-mating environmental stress, ACTH, cortisone acetate or metyrapone on oestrus and ovulation in sheep

Abstract: Administration of ACTH to Finnish Landrace × Dorset Horn ewes during days 13–16 of the pre-mating oestrous cycle resulted in a significant delay in the onset of oestrus (mean cycle length of 17·5 ± 0·39 days as compared with 16·4 ± 0·61 in a control group). Subsequent ovulation rate was significantly higher than in the control group (3·12 and 2·44 ova/ewe respectively).In a second experiment with Scottish Blackface ewes the effects on time of onset of oestrus and on ovulation rate of environmental stress, ACTH, cortisone acetate or metyrapone were studied. Environmental stress and administration of ACTH through the oestrous period significantly reduced ovulation rate (1·54 and 1·39 ova/ewe respectively) compared with the control (1·96). ACTH administered during days 13–16, as in the first experiment, and cortisone acetate administered through oestrus had no effect on ovulation rate (1·88 and 1·86 respectively). Administration of metyrapone reduced ovulation rate to 1·70 but this was not significantly different from the control. Both forms of ACTH treatment resulted in a delay in onset of oestrus but environmental stress had no effect on this character.Levels of plasma luteinizing hormone (LH) were estimated on representative animals. These showed that ACTH and environmental stress influenced the pattern of the ovulatory surge of LH in respect of time of onset of the surge relative to onset of oestrus, duration of surge and peak levels.

Pollination as a factor limiting the yield of field beans (Vicia faba L.)

Abstract: Self-pollinating and cross-pollinating by hand samples of flowers in field bean crops usually gave an increased set of seed compared with control flowers left to be pollinated naturally. Hence, insect pollination of field bean crops is often inadequate. In large fields of more than 12 ha the seed yield was greater by plants near the edge than near the centre. Fewer pods were produced from nodes at the upper than the lower parts of a stem, and they contained fewer seeds which were of a smaller size.

Nitrogen requirement of cereals: 1. Response curves

Abstract: Examples of response surfaces for pairs of nutrients and results of 41 multi-level experiments with N only were used to compare the goodness-of-fit of polynomial, inverse polynomial, exponential and intersecting-straight-lines models.Whereas no one model fitted best at every site, many results were well represented by two intersecting straight lines and on average, this model had the least residual mean square. Of 17 experiments with spring barley in south western England the few results best represented by smooth curves were from crops much affected by leaf diseases.Fertilizer response was poorly represented by models without a falling asymptote, like the simple exponential and inverse linear. Study of residuals after fitting the quadratic showed that this widely used model consistently over-estimated both the amount of fertilizer needed for maximum yield and the yield loss when too much fertilizer was given.When fitted to the mean yields of each nitrogen treatment, most models had residual mean squares equal to or less than the error mean square, repeating a result obtained at Rothamsted as early as 1927. We question the validity of some well-known evidence for block and treatment additivity.For 12 experiments in 1970, between-site differences in the parameter values of the two straight lines representing grain yield were related to leaf area at ear emergence.

Milk-fed calves: 1. The effect of milk intake upon the herbage intake and performance of grazing calves

Abstract: Two trials were conducted, using 18 and 30 castrated male calves respectively, to investigate the importance of milk in the diet of calves during the first 8 months of life and its effect on herbage intake and live-weight change. Reconstituted milk substitute was fed in a manner that simulated the supply of milk for lactation, yields of 2101, 1635 and 1165 kg (Expt 1) and 1906, 1609, 1304, 1005 and 701 kg (Expt 2) over a 240-day period. Calves were purchased in mid-February, when approximately 1 week old, and housed individually until turned out to graze at 10 weeks of age. At pasture, the calves were strip grazed on swards of Lolium perenne cv. S. 23 or S. 24 and given a daily herbage allowance of 60 g D.m. /kg live weight. The live-weight gain response to milk consumption was 81 g/kg milk fed during the housed period and 50 g during the grazing season. Herbage and milk intake per unit live weight were inversely related but because the grazing season responses were confounded with the treatments during the housed periods, it was not possible to determine true replacement rates. Herbage intake per head increased with time but there was no general trend when intake was expressed per unit live weight.

Effects of post-mating environmental stress or administration of ACTH on early embryonic loss in sheep

Abstract: In two separate experiments, ewes of the Scottish Blackface breed were subjected to management stresses in the first or second 10-day period after mating or were treated with daily injections of 60 i.u. ACTH for the whole 20-day period. Embryonic loss is defined as the number of corpora lutea not represented by viable embryos at slaughter. Examinations were carried out between 26 and 32 days post-mating. In the two experiments combined, losses were 29·9, 29·0, 37·7 and 17·2%, respectively, for ewes subjected to environmental stress during days 1–10, during days 11–20, treated with ACTH or kept as unstressed control. Expressed as the percentage of ewes in which partial or complete loss of shed ova occurred, the results were 49·0, 46·0, 54·3 and 25·5%, respectively. Losses were significantly higher in all treated groups than in the unstressed control.

A study on the pollination mechanism in field beans (Vicia faba L.)

Abstract: Inbred lines and hybrids of English tick and horse beans and exotic stocks were studied with respect to pod set, floral structure and pollen production and germination to find out why most inbred lines set few or no seeds without tripping whereas most hybrids and some inbred lines set equally well with or without tripping. The most important outcome was new information on variation between genotypes in flower structure and pollen quantity and on how these two characters affect the mechanics of self-pollination. Though heterosis in terms of abundant pollen production could be a factor in the self-pollinating ability of hybrids, some of the inbred lines were capable of self pollination despite limited pollen production, because the structure of the flower permitted the pollen to reach the stigma via a short route. The floral features associated with the ability to self-pollinate in the inbred lines included a relatively short style bending at more or less a right angle, few and short stylar hairs and stigmatic papillae, and less pronounced ridges on the inside of the keel petals. The implications of these findings to the development of self-pollin ated varieties of field beans are briefly discussed.

Variation in lean distribution among steer carcasses of different breeds and crosses

Abstract: Summary Dissection data for 753 steer carcasses comprising 17 breed-type × feeding system groups were used to examine the distribution of lean between 14 standardized commercial joints. Breed types included Ayrshire, Friesian, Friesian × Ayrshire and crosses out of Friesians by Angus, Charolais, Hereford, Limousin, Simmental and South Devon sires. Most cattle were grown on cereal or grass/cereal systems of feeding. Group means for weight of lean in the side (half carcass) ranged from 60·0 to 85·2 kg with a pooled within-group S.D. of 7·81 kg. The increase in lean weight in each joint relative to that in the side was examined using the allometric equation. Pooled within-group growth coefficients (b values) indicated that relative lean tissue growth was lowest in the leg (hind shin) and rump (b = 0·84 ± 0·03 and 0·85 ± 0·03 respectively) and highest in the clod and sticking (b = 1·19 ±0·03). The result for the combined higher-priced joints was 0·95 ±0·01. The pooled growth coefficients were used to adjust the weight of lean in each joint to equal total lean weight in the side where this was legitimate. Statistically significant (P < 0·001) but relatively small differences were recorded between groups in the adjusted means for all joints tested. At equal total lean weight, Charolais × Friesian, Limousin × Friesian and Simmental ×; Friesian groups had the highest weight of lean in the combined higher-priced joints and the Ayrshire and Friesian × Ayrshire groups the lowest. The difference between the two extreme groups was 2·1 kg (for one side).

A dynamic model for the effects of potassium and nitrogen fertilizers on the growth and nutrient uptake of crops

Abstract: A dynamic model has been derived to predict the day-to-day changes in the growth and nutrient composition of crops grown in the field with different levels of nitrogen and potassium fertilizer. Equations are included in the model to represent processes such as re-distribution of nutrients down the soil profile after rain or evapotranspiration, transformations between the various forms of potassium, transport of potassium ions through the soil to the roots and the dependence of growth and nutrient uptake on incoming radiation, plant composition, and soil water stress.The model was tested by using it to forecast the responses of a test crop, cabbage, to fertilizers in four separate field experiments at WeUesbourne. From data describing the initial soil conditions and weights of the plant, the soil and crop characteristics and the daily weather conditions, the model correctly predicted the pattern of responses in each experiment, although, in some instances the absolute values of the theoretical and experimental yields differed somewhat. Of special significance was the ability of the model to forecast the effects of different weather conditions on crop response and the interactions between the effects of N and K fertilizers on the growth and chemical composition of plants.

Competition for plant nutrients in soil; a theoretical approach

Abstract: A mathematical model of whole plant growth in soil is presented. Particular emphasis is given to those factors which relate to the absorption of nutrients and water by the root system. There are two basic premises; that a plant is made up of two pools, structural material and precursors to structural material, and that structural material is produced by a reaction between a given ratio of precursors. The precursors are soluble carbohydrate and unbound nitrogen, probably nitrate. Increase in leaf area and root length is a consequence of absorbed nitrogen combining with photosynthate.The absorbing power and the distribution throughout the soil of the roots is controlled, through feedback mechanisms, by the ratio of the precursors, within the plant. The description of plant growth is interfaced with a model of one-dimensional flow of water and solutes in soil, and gives a model for investigating plant growth, or competition between root systems of more than one plant. The results of a number of simulations are presented. A sensitivity coefficient is defined to compare the effect of various properties on overall growth. Its value is calculated for 11 plant properties. It is some measure of the competitive advantage conferred on the plant by a change in the value of each property. The results of the competition experiments are given as replacement diagrams.The model has weaknesses. Because it is explicit, it defines in precise detail the experiments which would support the hypotheses, or suggest modifications to them. As a holistic analysis, it brings together ideas from different disciplines into one comprehensible framework.

Growth rate and its effect on empty body weight, carcass weight and dissected carcass composition of sheep

Abstract: The effect of three different growth rates from 15 to 40 kg live weight on the body composition of lambs was studied. The treatments were: High (H) ad-libitum feed intake, Low (L) restricted feed intake and High–Maintenance–High (HMH) ad-libitum feed intake from 15 to 25 kg followed by a 50-day period during which live weight was maintained constant, which in turn was followed by ad-libitum feeding. The animals were individually penned and fed a pelleted lucerne chaff-cereal grain mixture. Two animals were killed at the start of the experiment (15 kg) and the remaining 27 animals (nine in each treatment) were killed at common live weights of 25, 30, 35 and 40 kg. Analyses of covariance were used to compare linear regression equations representing results from each treatment using the logarithmic transformation of the allometric equation, y = axb.Animals in the H and L treatments had a mean growth rate from 15 kg until slaughter of 0·23 and 0·09 kg/day, respectively. From a live weight of 15 to 25 kg, the HMH group grew at a similar rate as the H group, viz. 0·22 and 0·21 kg/day, respectively. After the 50-day period of maintenance of live weight, the HMH animals killed at 30, 35 and 40 kg showed a marked compensatory growth response to ad-libitum feeding. These HMH animals had a mean growth rate of 0·37 kg/day compared with 0·26 kg/day for H animals over identical live-weight ranges.Empty body weight (EBW) formed a similar proportion of full body weight (FBW) in all three treatments. As a proportion of FBW, hot carcass weight (HCW) was similar in the H and L treatments, while at the 35 and 40 kg slaughter weights HCW was less in the HMH than in the H treatment. HCW also formed a lower proportion of EBW at the 35 and 40 kg slaughter weights in the HMH, than in both the H and L treatments. In the L treatment, HCW formed a greater proportion of EBW than in the H treatment, indicating a greater offal component of EBW in the H animals.The results of carcass dissection studies showed that, at the same dissected side weight (DSW), the amount of muscle, bone, connective tissue and total side fat (TSF) was similar in the three treatments. Although no differences were found between treatments in TSF, there were significant treatment effects on both the subcutaneous and inter-muscular fat depots. Animals in the H treatment had more and less, respectively, subcutaneous and intermuscular fat than the L animals. The amount of intermuscular fat was also greater in the HMH than in the H treatment.

Effect of prostaglandin analogue Cloprostenol on oestrus, ovulation and embryonic viability in sheep

Abstract: The effect of a single injection of 100 μg prostaglandin analogue Cloprostenol, during the luteal phase of the oestrous cycle was examined for synchronization of oestrus, time of ovulation and embryonic viability in ewes.Following injection of Cloprostenol alone, 84% of ewes were detected in oestrus 29–48 h later. Pretreatment with PMSG increased the proportion of ewes in oestrus within 36 h. In these ewes 38% had begun ovulating 30 h after the onset of oestrus and by 36 h 87% had begun ovulating. Normal embryos of 8-cells to blastocysts were obtained from ewes given PMSG and Cloprostenol, and on transfer to recipient ewes, treated with Cloprostenol, all recipient ewes produced lambs.It is concluded that injection of 100 μg Cloprostenol is an efficient method of synchronizing oestrus in ewes and that normal embryonic development would be expected in mated ewes following this treatment.

The effect of interval between harvests and nitrogen application on the proportion and yield of crop fractions and on the digestibility and digestible yield and nitrogen content and yield of two perennial ryegrass varieties in the second harvest year

Abstract: The effect of six intervals between harvests and three levels of N application on the dry-matter yield of total herbage, the proportion and yield of green leaf, dead leaf, ‘stem’ and inflorescence of the sown species, the proportion and yield of unsown species, the digestibility and digestible yield and N content and yield was studied in S. 23 and S. 321 perennial ryegrass during a 30-week period in the second harvest year in a field experiment. In S. 23 the ‘stem’ was divided into true stem, leaf sheath, unemerged leaf and unemerged inflorescence.The results supported the main findings from the first harvest year (Wilman et al. 1976a, b).There was marked ingress of unsown species in the second harvest year with 3-, 4- and 5-week intervals in S. 321. The combination of 262–5 or 525 kg N/ha/year and 8- and particularly 10-week intervals over 2 years was too severe a treatment for the satisfactory survival of S. 23. With 525 kg N and 10-week intervals, S. 321 was equally badly affeoted.The application of 525 kg N/ha/year compared with nil reduced the proportion of green leaf in total herbage of the sown species by 11 percentage units, on average, and increased the proportion of ‘stem’ by 12 percentage units, in the second harvest year. The effect of N application on the proportion of crop fractions was found in both varieties and in all months of harvest. The effect was much greater than in the first harvest year. In S. 23 the application of 525 kg N compared with nil in the second harvest year increased the proportions of both true stem and leaf sheath (in total herbage of the sown species), true stem being the more important of the two, in this context, with the longer intervals and leaf sheath being the more important with the short intervals.Digestibility was not in general affected by N application despite the higher proportion of stem and leaf sheath and the lower proportion of green leaf blade resulting from N application. N did, however, tend to reduce digestibility at the harvests at which the proportion of stem was highest.Digestibility varied from one time of the year to another with a constant interval between harvests, but not as much as in the previous year. Lower digestibility of leafy crops in summer and autumn than in April and early May in both years may have been partly due to a higher proportion of dead material.Three periods were distinguished approximately in both years: May-June, July-August, and September-October. Only in the first of these periods was there a substantial increase in yield of digestible organic matter as a result of doubling the interval between harvests. Doubling the interval reduced digestibility in all three periods, but especially at harvests within the second period. Yield response to N was large in the first period, intermediate in the second, and low in the third. Apparent recovery of N was low and N content of herbage unduly high in the third period. N content of herbage was low with the long intervals between harvests at harvests in the first two periods. Applied N increased N content at these harvests and at all other times.

Accumulated temperature and maize development in England

Abstract: Information is given on dates of sowing and mid-silk for Inra 200 in 40 experiments (two each year at Oxford, 1962–75, and at Cambridge, 1970–5), together with cumulative temperatures between these dates. Two methods of defining effective temperature for maize development have been considered, namely the method advocated by U.K. Meteorological Office with 10 °C as the base temperature (the Ag. Met. method) and that defined in Ontario units. The regression relation between accumulated temperature and dry-matter content of the grain during ripening has also been calculated, from data obtained in the years 1966–74, and assessments made of cumulative totals in Ag. Met. day °C and in Ontario units from the date of silking until the grain D.M. content is 40%, when the crop is considered suitable for ensiling, and from silking until grain D.M. content is 60%, when the crop may be considered ripe.Cumulative temperature totals were significantly more stable over experiments than time expressed in calendar days. Totals of Ontario units were less variable than totals of Ag. Met. day °C. Estimated requirements for Inra 200 were 405 day °C or 1380 Ontario units from sowing to mid-silk, 255 day °C or 800 Ontario units from silking to 40% D.M. in the grain (for silage crops), and 380 day °C or 1235 Ontario units from silking to 60% D.M. in the grain.