Field experiments were made at the Punjab Agricultural University, Ludhiana, during 1974–5 to 1978–9 to study the possibility of improving wheat yield by more efficient use of radiant energy through modification of the shape of the canopy under varying levels of fertilizers, irrigation and seed rates. The results showed substantial yield increase by sowing half the seed and fertilizers in one direction and half in rows at right angles, giving a spacing of 22·5 × 22·5 cm, thereby intercepting more light, which showed a significant direct relationship with yield, but there were negative correlations with soil temperature. The increase in row spacing decreased the yield. With 33% extra fertilizer than the local recommendation, sowing the crop in two directions gave 0·96 t/ha (33·4%) higher yield, whereas none of the other sowing methods showed significant increase. Mixing varieties to form a prismatic canopy gave higher yield than the mean of the varieties sown alone. Irrigating the crop more than thrice did not prove beneficial. North-south row direction tended to improve yield compared with east-west rows. Seed rates varying from 50 to 200 kg/ha showed neither significant effect, nor interaction with canopy shape except in 1978–9 when 150 kg seed/ha showed yield improvement over 100 kg/ha.

Eight Merino and eight Dormer ewes, none of which had been on heat for 2–3 months prior to treatment, were given six intra-muscular injections of 30 mg. progesterone at 3-day intervals. The ewes were divided into four groups, each consisting of two Merinos and two Dormers. On the second day after the last progesterone injection, 1000 i.u. P.M.S. were administered to each of the ewes in group I. The remaining ewes each received an injection of 500 i.u. P.M.S. on either the first and second days (group II), the second and third days (group III), or the first and third days after the end of the progesterone treatment (group IV).

Five of the Dormer ewes, but not one of the Merino ewes, were served after the treatment. Mean ovulation rates for the four groups were 2·50, 2·75, 2·00 and 2·50, respectively, and the mean numbers of large follicles (i.e. those which were observed at laparotomy, approximately a week after treatment, to have a diameter of not less than 4 mm.) were 3·00, 2·75, 1·00 and 2·00, respectively. Contrary to expectation, it was observed that only one of the ewes (a Merino) showed evidence of a silent ovulation shortly before treatment.

It is suggested that (i) the amount of oestrogen produced by the ovarian follicles of the Merinos may have been exceptionally low, thus accounting for the non-occurrence of oestrus in these ewes, (ii) ovulation rates might be increased by greater reductions in the time between the last progesterone injection and P.M.S. treatment, and (iii) if silent heat in the Merino is rare, it may be simpler to induce coincident heat and superovulation in ewes of this breed by two injections of P.M.S. at 16-day intervals.

Birth weight and pre-weaning performance are recognized as important components in determing economic returns from beef cattle. The accuracy of ranking animals based on their breeding values, and hence the effectiveness of selection, will be increased when allowance is made for non-genetic sources of variation. Furthermore, the proper evaluation of identifiable sources of variation in calf weaning weight aids in more accurate appraisal of genetic differences in mothering ability among beef cows.

The application of chemical desiccants to lucerne and red clover after cutting is studied from the standpoint of increasing the drying rate in relation to pan evaporation. Significant increases in the evaporation-based drying constant are found on both first and second cuttings of these crops, but the savings of a full day's drying time is expected only for second-cut lucerne in the north-eastern U.S. climate. The effect of crop density on drying rate is also studied. In conjunction with a theoretical analysis, it is determined that the drying constant varies as γ-0.65, where γ is the areal density. The evaporation-based drying constant is then related to crop yield and the ratio of cutting width to windrow width.

The results obtained from artificial insemination of high grade Merino sheep in Kenya are given and discussed in relation to the season of the year, time of insemination during oestrus, the number of inseminations in each oestrous period and the degree of dilution of sperm.

A heat-exchange chamber made of perspex was inserted beneath the skin of a Merino sheep. By passing water at predetermined temperatures through the chamber, the normal subdermal temperature of 37°C was raised approximately 4°C for 4 days, then lowered approximately 5°C for 4 days.

In response to heating, the animal's temperature regulating mechanism was able to maintain a fairly constant subdermal temperature. However, it was unable to maintain as constant a subdermal temperature in response to cooling. There was, during the cooling period, an obvious nervous response to environmental disturbances manifested by sudden transient decreases in subdermal temperature over the chamber.

During the cooling period there was a decrease of 12% in mean length growth rate of wool over the chamber but mean fibre diameter was unchanged. Heating produced a small decrease in mean fibre diameter, but no change in mean length growth rate. Heating appeared to produce a slight reduction in pigmentation of some fibres but neither heating nor cooling produced demonstrable changes in crimping.

The study investigated the effects of chronic elevation or suppression of circulating prolactin levels on seasonal wool growth in Romney sheep. Ewes (n = 10/group) were housed indoors under natural lighting (latitude 34 °S) and received either 50 mg bromocriptine i.m./ewe/28 days (Group B), 1 mg spiperone s.c./ewe/day (Group S) or no treatment (Group C) commencing in summer. Wool growth and liveweight were measured every 4 weeks and venous blood samples were collected for prolactin determination. Plasma prolactin levels (mean±s.E.) in Group C exhibited a gradual seasonal decline from 121±29 ng/ml to 35±9 ng/ml. Bromocriptine suppressed prolactin levels rapidly from a pretreatment value of 118±2 ng/ml to below 12±7 ng/ml for the duration of the study. Prolactin levels in Group S were not significantly higher than Group C, with the exception of the first 14 days following the initial treatment. A seasonal reduction in wool growth of c. 25% was observed in all groups; however, no significant treatment effect was evident. Mean liveweight of all animals increased from 50·4±0·8 to 56·8±0·7 kg during the study. These results indicate that perturbation of the annual cyclic secretion of prolactin does not affect wool growth in the Romney ewe.

The objective of the current study was to develop, validate and describe a decision support system (DSS) to evaluate cull dairy cow finishing strategies. The DSS was developed within a Microsoft Excel framework. The purpose of a DSS is to assist the process of making accurate and repeatable calculations, assisting the decision on which cull cow finishing strategy is most profitable under individual farm circumstances. The model was based on data from two evaluation experiments including eight finishing strategies in total: ad libitum grass silage (GS); GS+3 kg concentrate (GS+3); GS+6 kg concentrate (GS+6); GS+9 kg concentrate (GS+9); ad libitum grass silage prior to ad libitum spring grass (GS+G); 0·75 grass silage and 0·25 straw prior to ad libitum spring grass (GS+S) and finally grass silage plus 6 kg concentrate dry matter (DM)/cow/day and milked twice daily prior to ad libitum spring grass (EXTLAC). Stochastic budgeting was included in the model to account for variability in key input and output variables on the overall profitability of various finishing strategies. The stochastic input and output variables included in the model were initial carcass value, feed strategy, concentrate cost and final carcass value. Net profit per cow was selected as the output distribution. The mean net profit per cow with the GS, GS+3, GS+6, GS+9, GS+G, GS+S and EXTLAC was €85·3, €73·7, €95·6, €58·5, €158·8 and €186·8 and €283·0, respectively. Profitability for the EXTLAC strategy was stochastically dominant to all other strategies evaluated meaning a higher level of profit and a lower level of risk is associated with the EXTLAC strategy. The optimal strategy of cull cow beef production depends greatly on the prevailing economic environment, purchase and sale price, milk price, feed costs, housing and labour.

A general account of investigations carried out at the Plant Breeding Institute, Cambridge, on winter oats was published by Hunter (1935). In it brief mention is made of the origin of a series of oats designated the ‘ex 109/1 series’. It is the purpose of this article to give a more detailed account of the origin and behaviour of this series, from which the winter variety Picton was selected, and to detail a further number of anomalous features which have arisen in the course of breeding work at Cambridge.

Thirty-six Border Leicester x Scottish Blackface ewes were separated from their lambs after approximately 12 weeks lactation and brought indoors. They were allocated at random to nine dietary treatments comprising three dietary ratios of chopped roughage to concentrate, each offered at three levels of feeding. During the course of the experiment digestibility and nitrogen balance trials were carried out using three ewes from each dietary treatment.

The daily nitrogen intakes required for nitrogen equilibrium were calculated from the regressions of nitrogen intake on nitrogen retained for each of the three ratios. The intakes increased from 0·47 g/kg W0·75 on the diet containing the lowest proportion of roughage to 0·59 g/kg W0·75 on the diet containing the highest proportion of roughage. The corresponding digestible organic matter intakes did not differ significantly from the pooled value of 18·8 g/kg W0·75.

The daily digestible organic matter intakes required for the maintenance of live weight on the three ratios did not differ significantly from the pooled estimate of 26·9 g/kg W0·75 which is in close agreement with other published results. The nitrogen intakes required for the maintenance of live weight increased from 0·70 on the diet containing the lowest proportion of roughage to 0·84 g/kg W0·75/day on the diet containing the highest proportion of roughage.

The coefficients for live-weight change in the regression equations relating digestible organic matter to live weight and live-weight change for each ratio did not differ significantly from the pooled estimate of 2·0 g DOMI/g live-weight change.

The significance of the results are discussed in relation, to the nutritional status of the ewe and other research findings.

Wool samples from 49 ewes representing four breeds of sheep, Ossimi, Rahmani, Barki and Merino were used to study the seasonal variation in wool growth. The first three breeds are of the local carpet-wool types of Egypt.

Consistent differences were found between breeds in diameter and length of fibres (i.e. genetic effects). These effects were not modified by the environment (i.e. time of year) although the latter had different effects on diameter than on length. Medullation, however, was not consistent from breed to breed in all seasons (i.e. there was genotype x environment interaction). It is concluded that seasonality in wool growth exists under the semi-arid conditions of Egypt in local breeds but to a lesser extent in imported Merino sheep.

In field and wind tunnel experiments in 1988 at the Scottish Centre of Agricultural Engineering, moisture loss in the 24 h after cutting increased when grass swaths were mixed, spread or turned and was positively related to the number of mixings. In the field trials, dry matter loss from conditioned swaths increased when the swaths were mechanically mixed or spreadafter cutting.

A 2 × 3 factorial trial designed to investigate the effects of castration and three diets on growth and body composition of 30 male Dorset Horn × (Border Leicester × Merino) lambs is described. The three diets were: (a) a standard ration of equal weights of lucerne chaff and pelleted concentrates; (b) a similar ration to (a) plus 7·5% by weight of lipid (peanut oil and tallow); (c) a greater ration of (a) calculated to be isocaloric for digestible energy with diet (b).

At the beginning of the trial a group of 40 lambs (20 rams, 20 wethers) were shorn and five rams and five wethers were selected at random and slaughtered to establish initial body composition. The remaining 30 lambs, 15 rams and 15 wethers aged about 22 weeks and having mean weights of 33·0 kg (rams) and 31·2 kg (wethers), were randomly divided within sex into three groups and allocated to the three diets for 92 days. At the end of this period the lambs were again shorn, and then slaughtered and dressed.

During the trial, rams gained significantly (P < 0·001) more weight than wethers, and lambs on diet (a) gained significantly (P < 0·01) less weight than those on (b) and (c). Weight gains on the latter two diets were similar. Diet generally had little effect on body composition, although there was a tendency, within sexes, for lambs on diet (b) to have a greater fat content than those on the other diets. Rams had significantly greater carcass weights (P < 0·01), head percentage (P < 0·001) and various m. longissimus dorsi dimensions than wethers, but significantly less fat in all the locations measured, including a lower percentage of chemically extractible fat in the offals and carcasses. Estimations of the energy stored in the wool-free body during the trial indicated that wethers stored significantly more energy in the form of fat than rams (P < 0·001), but that rams stored significantly more non-fat energy than wethers (P < 0·001). It is concluded that a maximum growth rate exists for the non-fat body, and that it is higher in rams than wethers. Thus the addition of dietary lipid (which increases energy intake with comparatively small increases in weight or volume of feed), is more likely to promote fat deposition in wethers, which have a lower maximum capacity for non-fat storage, than in rams.

Results of a co-ordinated trial carried out at 20 centres indicated that increasing the dietary crude-protein percentage by 2·5 and the lysine by about 0·2 over the ARC recommended levels failed to improve performance or carcass quality, whereas decreasing these nutrients to a similar degree below the recommended levels adversely affected performance and carcass quality.

At four centres there were six to eight replicates. Substantial differences in estimates of both the level of response to a given treatment and the magnitude of treatment effects were observed between individual centres.

Factors affecting the size of these co-ordinated trials are discussed.

Conformation of carcasses from 98 steers from ten different sire breeds was classified according to two visual systems and two objective measurements, which were related to both commercial and dissected carcass composition of their hindquarters. The visual carcass conformation systems, unlike the objective systems, accounted for only a small percentage of the variation in some carcass traits after adjusting for the weights of the right hindquarter and of dissected fat from that hindquarter. Of the carcass conformation systems tested, the objective measurement of area appears to be the best predictor of carcass traits, with the variation in the weight of meat being reduced by 13·4% (P < 0·001) by the inclusion of area measurements. It is suggested that an objective assessment of carcass conformation might be of use in a national carcass classification or grading system.

In 12-year (1975–87) fertilizer trial on a pearl millet-wheat rotation, there were no responses to applied K and exchangeable K decreased from 620 to 200 kg/ha. In spite of progressively diminishing exchangeable K, removal of K by crops was independent of soil K status, indicating that exchangeable K had no relation to K uptake in this soil. Thus, nonexchangeable K made a major contribution to plant K, up to 90% in untreated plots and > 70% in K-treated plots. A significant (r = -·708) relationship between nonexchangeable K and K fixation capacity was found. Nonexchangeable K was also significantly but negatively correlated (r = -0·583) with free energy exchange (ΔGr). Potassium supply values, expressed by pK-½p (Ca + Mg), were positively and significantly correlated with K removal by crops in 1987 and with the K saturation values of the exchange phase, so that both these measures can be successfully used to test soil K availability. The results of this study suggested that on this soil, under a pearl millet-wheat crop system, inclusion of K in the fertilizer programme may soon be needed.

Seeds of the plant Crotalaria retusa L., containing 4·4% of the pyrrolizidine alkaloid monocrotaline, were fed in a finely ground form to broiler chickens at 0·005, 0·01, 0·05, 0·10 and 0·50% by weight of the diet continuously for 8 weeks.

Feeding 0·005% and 0·01% had no effect on the growth performance of the birds. A non-significant reduction in live-weight gain, one death and chronic disease resulted from feeding 0·05%. At 0·10% and 0·50% there was high mortality and reduced voluntary feed intake, live-weight gain and feed conversion efficiency, the severity of the response being greater at 0·50%.

Feather development was inhibited in birds fed 0·10% and 0·50% C. retusa seed.

Until further research is done to determine the effect of feeding between 0·01% and 0·05% ground C. retusa seed in the diet of broiler chickens, it is suggested that the maximum should be 0·01%.

Simulating changes in the distribution of the particle marker between particle-phase and fluid-phase dry matter by ±40% resulted in calculated flows of dry matter to the duodenum that differed from the ideal of uniform distribution by 1 to 2%; true digesta flow values were virtually unaffected. These errors are small and can probably be ignored.

In a 3 × 3 latin-square design experiment, 12 British Friesian steer calves with rumen cannulae were offered three red clover silages to appetite, either alone or with a urea supplement of 18.9 g/kg total dietary dry matter (D.M.). The silages were prepared from a second cut of red clover using additives of 2·11 formic acid/t fresh crop together with formaldehyde at 0, 31 or 123 g/kg crude protein (CP) in the crop.

The control silage was well preserved, as indicated by a low content of volatile fatty acids and ammonia N. Formaldehyde treatment generally restricted silage fermentation, although there was an increase in the content of butyric acid at the intermediate level of application, and an increase in 2, 3-butanediol content at the high level of application. A decline in ammonia-N content and an increase in insoluble-N content, with increasing level of formaldehyde application, indicated that formaldehyde had been effective in reducing protein degradation in the silages.

Formaldehyde treatment depressed intake, the apparent digestibility of D.M., organic matter (OM), N, cellulose and energy, and N retention, the effect being particularly evident at the high level of application. Behavioural observations showed an increase in eating time on the formaldehyde-treated silages. Urea supplementation increased intake of the formaldehyde-treated silages, but did not influence intake of the control silage, and increased N retention on all silage diets. Apart from an improvement in apparent N digestibility, urea supplementation did not influence the digestibility of other dietary components.

Within the rumen, formaldehyde treatment reduced ammonia-N concentration and the molar proportions of propionate and butyrate, and increased the molar proportion of acetate. The rate of D.M. and cellulose disappearance from treatment silages suspended in the rumen in nylon bags was reduced by formaldehyde treatment, the effect being most evident at the high level of formaldehyde application. A similar effect on rate of D.M. disappearance was observed when the control silage was placed in nylon bags, indicating that the adverse effect of formaldehyde was probably due to an effect on the rumen environment. Urea supplementation increased rumen ammonia-N concentrations, although this effect was not as great on the high formaldehyde silage, and increased the rate of D.M. and cellulose disappearance from silage in nylon bags.

It appears that the lower intake and the poorer utilization of dietary N on the high formaldehyde silage may have been due to a reduction in the rate of digestion within the rumen. While there was some response to urea supplementation, it could not restore the apparent rate of digestion in the rumen to levels observed on the control diet. Hence, factors other than the supply of rumen-degradable N in the diet must have been responsible for the depression of digestion within the rumen.

Proximal colons taken from lambs up to 3 weeks after birth were shown to transport both sodium and chloride from lumen to blood when incubated in vitro.

Sodium transport fell into three phases during postnatal development. The first covered the period from birth to 3 days of age when sodium transport was high and equal to that calculated from measurement of short-circuit current. The second was seen in 5- and 7-day-old lambs where the short-circuit current was low and the net transport of sodium was negligible. The third was seen in 2-3-week-old lambs where sodium transport was high, but the short-circuit current was low.

Chloride absorption by colons taken from 1-day-old lambs appeared to be in exchange for an anion, possibly bicarbonate. Chloride absorption by colons taken from 3-week-old lambs appeared to be electrogenie or coupled directly to the transport of sodium.

A possible explanation for the failure of electrolyte absorption by colons taken from 5- and 7-day-old lambs is discussed.