Showing papers in "The Journal of Agricultural Science in 1982"

The effect of three levels of intake of Ostertagia Circumcincta Larvae on growth rate, food intake and body composition of growing lambs

Abstract: Forty-eight 4-month-old lambs, reared worm-free from birth, were allocated to six groups and offered ad libitum a complete diet containing 139 g crude protein/kg D.M. One group was killed at the outset as initial control (CI). Further groups, ALC, 1, 2, 3 and 4 were dosed daily for 84 days with zero, 1000, 3000, 5000 and 5000 larvae of Ostertagia circumcincta, respectively. Lambs in group 4 also received anthelmintic (fenbendazole, 5 mg/kg) on days 21, 42, 63 and 84. Lambs were killed after 98 days and their carcasses and those of the initial controls analysed for fat, protein and mineral contents.

A study of the growth of sheep to maturity

Abstract: Two groups of weaned sheep weighing about 30 kg, one born in March and the other in September, were each divided into two and given ad libitum one of two pelleted diets, ruminant diet A or ruminant diet AA6. The March-born sheep commenced experiment in July and those born in September in January. The experiment continued for 4½ years. At intervals sheep were killed and the fat protein and ash contents of their digesta-free bodies determined.The voluntary intake of feed showed a seasonal periodicity with minima in the winter and maxima in summer. The amplitude was 30% in the 1st year and in subsequent years averaged 13%. Those given the higher quality diet (AA6) consumed slightly less than those given the poorer one.Mean daily feed intake averaged over 6-month periods from January to July and July to January was invariant with age during 4 years of observation. In this time the sheep increased in weight from about 30 kg to about 130 kg. There were, however, considerable differences between individual sheep in the amount of feed they habitually consumed.The body weight of the sheep increased and eventually plateaued. The asymptotic weight defined as A in the equation W = A–Be–kt, where W is weight at time t and B and k are constants, was related to the mean daily feed intake averaged over 6 months; mean daily feed intake measured over 6 months was proportional to a fractional power of body weight indistinguishable from 0·75, the interspecies power to which metabolism is proportional. Growth of wool during successive 6-month periods did not vary with age of animal but differed significantly between animals.Fasting metabolism of the sheep was 316 kJ/kg W0·75 for wethers and 336 kJ for rams.Analysis of the bodily composition data showed that over a range of digesta-free body weight from 46 to 130 kg it was not possible, on statistical grounds, to distinguish between linear relationships between body weight and its fat, protein, ash and water content, and allometric ones. The linear relationships had marginally smaller residual standard deviations and the regression coefficients show that the gain of the empty body in these sheep consisted of 68% lipid, 8% protein, 1% ash and 24% water. The lipid in the carcass accounted for 88% of the total lipid gain and half the accretion of protein and ash was in the carcass. These results confirm those of Searle, Graham & O'Callaghan (1972) based on tritium dilution which showed that post-puberal growth in sheep is of constant composition.The results of the metabolic studies are shown to be consistent with the growth studies.Growth to maturity, as affected by different hypotheses related to the determinants of maintenance energy expenditure and the regulation of appetite, was examined algebraically. It is shown that mature weight is the rate of feed intake divided by the rate of maintenance metabolism per unit weight, and for defined feeding systems the rate constant for the approach to mature weight is the rate of maintenance metabolism divided by the feed equivalent of unit gain.The implications of the results in terms of the measurement and prediction of feed intake and the use of metabolic body size as a scaling factor in comparative and genetic studies of growth are briefly discussed.

Effects of maternal nutrition and plasma progesterone concentrations on survival and growth of the sheep embryo in early gestation

Abstract: Mature Merino ewes (n = 320) were fed either maintenance (100% M) or 25% maintenance (25% M) rations from the day after mating until embryos were collected at either day 11 or 21 after mating. On the 4th day after mating 223 ewes were ovariectomized and given 5, 10, 15, 20 or 25 mg progesterone/day (intramuscular) until embryo collection. A further group of sham operated ewes (n = 54) acted as controls. Despite live-weight losses of 10·7 and 15·8% from mating to days 11 and 21 after mating respectively, ewes on 25% M rations showed no evidence that embryonic survival was influenced by undernutrition. The embryos from ewes fed 25 % M rations were significantly (P < 0·05) smaller than those fed 100% M (crown-rump measurements were 5·93 ± 0·139 mm and 6·39 ± 0·116 mm at day 21 after mating in the 25 % M and 100% M groups respectively). Development, assessed by formation of the first pharangeal lobe and the fore- and hind-limb buds, was significantly retarded (P < 0·05) in the 21-day-old embryos from the undernourished ewes. Embryo survival in ovariectomized ewes receiving 5 or 10 mg progesterone/day was significantly (P < 0·05) lower than in ovariectomized ewes receiving 20 and 25 mg progesterone/ day at day 11 after mating. Embryo survival at both days 11 and 21 after mating increased with increasing doses of progesterone. Ewes fed 25% M rations had elevated (P< 0·001) concentrations of peripheral progesterone compared with those fed 100% M. This occurred when the progesterone was derived from either exogenous or endogenous (ovarian) sources, dismissing the possibility that changes in secretion rates could account for these observed differences. Differences in embryo growth and development were not related to these variations in the plasma progesterone concentration. Undernutrition restricted both growth and development to 21 days of pregnancy.

A mathematical model of the rumen

Abstract: A dynamic model of rumen processes is constructed. The nine state variables considered are: rumen metabolic volume, non-rumen-degradable β-hexose, rumen-degradable β-hexose, α-hexose, water-soluble carbohydrates, non-protein nitrogen, rumendegradable protein and non-rumen-degradable protein. The dietary and salivary inputs to the rumen may be continuous, or pulsed. Rumen outflow given by the model is compared with data on sheep fed with different diets. Reasonable agreement is obtained when the model is run in the continuous mode, but there are considerable discrepancies between the experimental data and the pulsed model.

Adjustment for competition between varieties in plant breeding trials.

Abstract: A method is proposed for correcting for competition effects in yield trials by joint regression of plot yields on to the yields of neighbours. Estimation of the variety effects and competition coefficient along with tests of significance are described for a sugar-beet trial with single-row plots where competition effects are assumed to extend only to plants in immediately adjacent rows. For designs which are balanced for neighbouring varieties it is feasible to estimate separate varietal competition coefficients which may be partitioned into components for sensitivity and aggressiveness. An example is given of this extended model fitted to a competition diallel of seven species. While species differed in their sensitivity to competition there was no essential difference between inter- and intra-species behaviour. The model is used to assess comparative varietal performance in monocultures from performance in small plot trials.(Note that the general term ‘variety’ is used throughout this paper to refer to progenies at any stage in a selection programme.)

Leaf appearance and extension in field-grown winter wheat plants: the importance of soil temperature during vegetative growth

Abstract: Mainstem leaf appearance and leaf extension were monitored at 7-day intervals throughout the vegetative development of field-grown winter wheat plants, during two growing seasons 1977–9. Using hourly air and soil temperature records, it was found that the rate of leaf appearance was controlled by soil temperature, with the best linear relationships being obtained using accumulated soil temperature above a base temperature of 0 °C at 1 and 5 cm depth. Leaf appearance could be predicted equally well using 09.00 G.M.T. screen air temperatures although deviations from each linear relationship were found during very cold periods when slow leaf extension rates delayed leaf appearance.Leaf extension was also found to be linearly related to temperature, with the best fit being obtained using accumulated soil temperature above 2·5 °C at 5 cm depth, suggesting a threshold of 2·5 °C for leaf extension. The response to temperature (extension per unit of accumulated temperature) was the same for all the leaves of a given plant, or sowing date; however, the fact that the rate of leaf extension increased progressively with sowing date suggests that plant response to temperature may be determined at crop emergence (possibly mediated by rate of change of day length). Leaf extension rates could be predicted satisfactorily using 09.00 G.M.T. soil temperatures (5 or 10 cm) but less so using screen air temperatures.The prediction of plant leaf areas or crop leaf area indices using such relationships between temperature and leaf growth was found to be hampered by rapid and irregular rates of leaf senescence.

The use of titanium dioxide for determining apparent digestibility in mature domestic fowls (Gallus domesticus)

Abstract: The apparent digestibility of a diet can be calculated from the amounts of food eaten and excreta voided. This ‘total collection’ method is laborious because it requires a period lasting several days. It can be circumvented by the inclusion in the diet of a suitable reference substance (Kotb & Luckey, 1972). From the concentration of the reference substance (marker) in the diet and in the droppings, apparent dry-matter digestibility can be calculated.

Inverse relationship between concentration of progesterone and nutrition in ewes

Abstract: Mean progesterone concentrations were measured in the peripheral plasmas of Merino and Border Leicester × Merino ewes which were fed from day 2 to day 16 after mating on rations designed to provide twice maintenance (2 M), maintenance (M) and one quarter maintenance (¼ M) of food requirements. Mean plasma progesterone concentrations were consistently higher in the ¼ ewes than in the M or 2 M ewes whether they had two corpora lutea (CL) and two embryos surviving or one CL with either one embryo surviving or no embryo surviving, and tended to be lower in the 2 M than M ewes. It is concluded that there is an inverse relationship between levels of nutrition and progesterone within an oestrous cycle in ewes.

Fasting and maintenance metabolism of sheep.

Abstract: A series of measurements of the heat production of 16 adult sheep made at intervals of not less than 4 weeks when they were given precise amounts of different diets at about the maintenance level of nutrition were analysed statistically. The total number of observations was 365. For some sheep the observations spanned periods of more than 3 years and none spanned less than 1½ years.There were no time-related trends in the metabolizability of the gross energy of the diet. It was found that the measured heat productions, the heat productions corrected to zero energy retention and the heat productions corrected to zero feed intake (calculated fasting metabolism) were sinusoidal with time. The amplitude of the sine coefficient was about 14% of the mean value, and in some sheep there was in addition a linear secular trend. The phase of the sine function was such that minimal metabolism occurred in midwinter and maximal metabolism in midsummer.The results suggest that the seasonal variation in voluntary feed intake is associated with a similar seasonal variation in basal metabolic rate. The fact that all animals were given maintenance rations throughout further suggests that the higher metabolism is not due to higher feed intake.

Sweating response in cattle and its relation to rectal temperature, tolerance of sun and metabolic rate

Abstract: Sweating rates were analysed in relation to rectal temperatures of cattle to yield a measure of sweating response within and between animals. The measurements, performed over 36 days, were done in a natural radiant environment on six steers in each of three breeds, Brahman (B), Brahman × Hereford–Shorthorn cross-breds (BX), and Shorthorn (S). Each steer was recorded for 30 min on six occasions randomly distributed among 6 h between 08.00 and 13.00 h, and on six occasions between 11.00 and 16.00 h, all on different days. Sweating response, e.g. the linear slope of the relationship between sweat rate and rectal temperature, was greater for B (294 g/m2. h/°C) than for BX (146 g/m2.h/°C) or S (194 g/m2.h/°C) which did not differ; this helped to explain why the range and mean rectal temperature in B were lower and little affected by environmental heat. Curvilinear models of the sweating response indicated that in the environmental conditions of this study, the limit of sweating for B and BX was not reached, while for S, the sweating response approached a plateau. Between animals, the relationship of sweating response to mean rectal temperature was negative (P < 0·01) and its relationship to the time spent in the sun at pasture positive (P < 0·025). Thus this measure of sweating response was a good indicator of thermoregulatory ability of the cattle. However, the sweating response of the steers did not relate to their grazing time or growth. The reasons for this are discussed. Finally, the sweating response was found to be negatively correlated with metabolic rate between animals within breeds (P < 0·01) and this suggested that it may be difficult to combine the desirable traits of good heat adaptation and high metabolic potential in cattle.

Effect of daily infection with Ostertagia circumcincta larvae on food intake, milk production and wool growth in sheep

Abstract: Forty pregnant sheep were allocated to four groups and maintained indoors in individual pens on a pelleted diet. During the last 6 weeks of pregnancy and the first 6 weeks of lactation groups were infected daily with 4000 larvae of Ostertagia circumcincta or remained as controls in a cross-over design. Thus groups were either not infected (CC), infected only during pregnancy (IC), during lactation (CI) or during both pregnancy and lactation (II). Food was offered on the basis of body weight at the beginning of pregnancy and lactation. Food intake, body-weight change, faecal egg counts, plasma pepsinogen and milk production were measured weekly, wool growth and fibre diameter during 21-day periods and tensile strength of wool over the whole experimental period.Eggs were seen in faeces of only three sheep infected during pregnancy, but in all sheep infected during lactation; maximum mean values were 467 ± 144 and 222 ± 58 eggs/g fresh faeces in CI and II sheep, respectively. Pepsinogen concentrations rose after 1 week of infection during pregnancy and lactation; peak values were 868 + 57 and 1104 ± 146 m-u/l, respectively.Infection reduced food intake by 16% during lactation but had no effect during pregnancy. There were significant interactions between pregnancy and lactational treatments on intake during lactation. Infection during lactation increased bodyweight loss; mean values were 57, 40, 114 and 78 g/day for groups CC, IC, CI and II respectively. Milk production was decreased during weeks 4–6 of lactation, mean values being 1·59 and 1·32 kg/day in control and infected groups, respectively.Infection reduced wool growth and wool fibre diameter by 20 and 7%, respectively, during the final 3 weeks of infection during lactation. The staple strength of wool grown during the experiment was reduced by 14, 45 and 23% in IC, CI and II groups, respectively. Infection moved the point of greatest wool tenderness from parturition in control sheep to a time during the period of infection, particularly when infection occurred during lactation.

Floret survival in wheat: significance of the time of floret initiation relative to terminal spikelet formation

Abstract: Wheat (Triticum aestivum L.) cv. Gamenya was grown in a Mediterranean type environment in two separate field experiments, to determine the effects of nitrogen application and date of seeding on floret survival. One treatment, intermediate in nitrogen level and sowing date, was common in both experiments. Rates and durations of spikelet initiation and durations of the floret initiation period were estimated. At maturity, yield and yield components were measured and occurrence of individual grains at each floret position on odd-numbered spikelets were recorded. The time of floret initiation relative to terminal spikelet formation and the subsequent occurrence of grain were examined.Florets developed first in spikelets 5-13 and last in spikelet 1. Added nitrogen hastened the initiation of florets but did not affect the number initiated; it also increased the numbers of grains per spikelet. In the last sowing date treatment, time to floret initiation decreased, but the sequence of floret initiation was unaffected.Numbers of florets and grains on tillers were less than on main shoots. Only about 28% of all florets initiated developed into grain.The main conclusion was that the florets which initiated before the terminal spikelet formed grain and those that initiated afterwards did not; we accordingly postulate that the vascular system between the rachis and the floret develops as the floret is initiated, but that after terminal spikelet formation, this is inhibited and further grains then fail to develop.

The effects of oxalate in tropical grasses on calcium, phosphorus and magnesium availability to cattle

Abstract: Cattle were fed four hays in mineral balance experiments. Two of the hays (Cenchrus ciliaris and Setaria sphacelala var. sericea) contained 1·8 and 1·3% total oxalates and provided above- and below-maintenance intakes of calcium respectively. These grasses contain calcium oxalate crystals. The other two hays (Aristida spp –Bothriochloa spp. mixture and Triticum aestivum) contained 0·1% oxalates, and also provided above- and below-maintenance intakes of calcium. The absorptions of calcium from the hays providing above-maintenance intakes were 51% for the high and 57% for the low oxalate hay. At below-maintenance intakes, the cattle were in negative calcium balance and calcium absorptions were 52% for the high and 64% for the low oxalate hay. While in negative calcium balance the cattle were given single doses of calcium oxalate, followed by single doses of either limestone or rock phosphate. The cattle fed S. sphacelata hay absorbed sufficient calcium from calcium oxalate to achieve positive calcium balance, although the amount absorbed was only 52% of that absorbed from limestone. The cattle fed T. aestivum hay also absorbed calcium from calcium oxalate, but in insufficient amount to result in a positive calcium balance. The amount absorbed was 47% of that absorbed from rock phosphate. The results demonstrate that in tropical grasses containing calcium oxalate crystals, the availability of calcium is about 20% lower than it is in grasses containing little oxalate. Adaptation to oxalate may improve the ability of the rumen to utilize calcium oxalate. It is suggested that the availability of calcium to cattle grazing tropical grasses should be considered to be a maximum of 50%. Neither magnesium nor phosphorus absorptions from tropical grasses were affected by oxalate.

Crop characteristics and the potential yield of wheat

Abstract: The potential yield of the best varieties of winter wheat currently grown in eastern England is estimated to be in the range 12–14 t/ha (15% moisture, 10% protein, freshweight basis).Increases in the leaf area index at anthesis, in the duration of the grain-filling period and in the light-saturated rate of photosynthesis of the leaves, slower decline in their photosynthetic capacity, and decreases in the respiratory losses of assimilated carbon would increase this potential yield. Such changes might be brought about by breeding or by improved agronomic practices.The grain growth rates predicted by several published simulation models are shown to be in reasonable agreement with each other.

A reappraisal of stem reserve contribution to grain yield in spring barley (Hordeum vulgare L.)

Abstract: Pre-anthesis stem reserve contribution to grain yield was assessed in two spring barley cultivars of contrasting height. It was greatest in the taller, but final grain yields were similar. Partitioning of total reserve capacity to various plant parts showed that the leaf and sheath below the peduncle were most important, followed by stem internodes which had increasing reserve capacity up to internode 4.It is suggested that stem reserves are valuable for yields commonly achieved in U.K. commercial practice.High grain yields were associated with large positive increases in stem dry weight after anthesis. This would indicate that the source capacity to boost yield is more than proportional to that required to fill the grain alone.

The effect of urea and urea plus sodium sulphate on microbial protein production in the rumens of sheep given diets high in alkali-treated barley straw

Abstract: The effects of virea and urea plus sodium sulphate on the production of microbial protein were studied in sheep fitted with rumen fistulae and re-entrant cannulae in the proximal duodenum and terminal ileum. Diets containing a high proportion (0·68–0·72) of sodium hydroxide-treated barley straw supplemented with starch, glucose and solka floe were fed at hourly intervals to the sheep at 830–870 g dry matter/24 h.The addition of the urea and urea plus sulphate supplements, although inducing a stepwise reduction in overall digestibility of OM, resulted in increased microbial protein synthesis in the rumen, which was reflected in increased quantities of amino acid nitrogen entering the small intestine (8–38, 12–03 and 17–84 g of total amino acid nitrogen (TAA-N)/24h respectively). The efficiency of microbial protein production (g bacterial TAA-N/kg OM actually digested in the rumen) was significantly increased by the addition of urea and still further by additions of urea plus SO4-S (11·1, 20·2 and 29·6 grespectively).Digestibilities of the individual amino acids in the small intestine were very similar on each dietary treatment. Apparent digestibilities of total amino acid-N within the small intestine (based on amounts entering the small intestine) were 0·623, 0·672 and 0·688 on the basal diet, basal diet plus urea and basal diet plus urea and S respectively.The proportions of cyst(e)ine-S in rumen bacteria synthesized from the rumen sulphide pool were 0088, 0·075 and 0·669 on the basal diet, basal diet plus urea and basal diet plus urea and S respectively. The data confirm appreciable recycling of S into the rumen.

A mass-selection method for the acclimatization and improvement of edible diploid potatoes in the United Kingdom

Abstract: A mass-selection scheme for outbreeding diploid potatoes of the Phureja-Stenotomum Group is described; the scheme includes both seedling and ongoing tuber populations. Provision is made for higher yielding clones to contribute more true seed to ensuing generations. A computer is used to document and randomize the plantings. Selection criteria and methods are described. Results are given from an experiment to monitor progress. The use of diploid potatoes in British breeding, and the historical development of breeding methods, are reviewed in relation to the present mass-selection scheme.

Effects of induced, subclinical phosphorus deficiency on feed intake and growth of beef heifers

Abstract: Hereford heifers were fed a diet (7·0 MJ ME/kg D.M.) containing 0·09 % phosphorus but complete with regard to other nutrient constituents. Only after 19 weeks wore the effects of subclinical aphosphorosis evident in the form of reduction in feed intake, cessation of weight gain, increased feed conversion and decreases in tho concentration of inorganic phosphorus in blood and saliva. Heifers supplemented daily with 12 g phosphorus sustained a weight gain of about 0–2 kg/day over 62 weeks as did other supplemented heifers whose feed intake was restricted to that of tho low phosphorus treatment. The effects of phosphorus supplementation were thus demonstrated without being confounded by concomitant increases in feed intake.Phosphorus supplementation resulted in significantly lowered apparent crude protein digestibility and a slight increaso in cell wall digestibility.

Modification of water balance of dryland wheat through the use of chlormequat chloride

Abstract: In field trials made for two years in the dry period of a semi-arid tract under natural precipitation at the Indian Agricultural Research Institute, New Delhi, overnight seed-soaking of wheat in 0·5% solution of 2-chloro-ethyl-trimethyl ammonium chloride (CCC) prior to sowing increased the grain yield. When treated with foliar application of the chemical in concentrations ranging between 40 and 1000 mg/1, wheat plots yielded better than did the untreated control, but no consistency was noted between the concentrations or stages of their application. The benefit from CCC was due to more root growth, increased stomatal resistance and higher leaf water potential. Treated plants extracted more water from deeper soil layers, increasing their water-use efficiency.

Immediate behavioural consequences of fostering 1-week-old piglets

Abstract: Twenty-four sows and their 4- to 7-day-old litters were observed in batches of four for approximately 2h to ascertain piglet teat preferences and timings of suckling periods. In each batch, two litters were then selected to have two piglets exchanged between them while the other two remained intact as controls. In the subsequent 3 h, sows with fostered piglets initiated significantly more suckling periods than controls; but many were disturbed at an early stage and only 35% of such periods resulted in milk letdown (compared with 93% in controls). Many sows displayed aggression specifically towards fostered piglets. Many fostered piglets showed signs of distress and attempted to escape. Fostered piglets were significantly more likely to take 10 sec or more from the start of suckling to approach the udder, and less likely to be sucking at milk letdown. Many of these effects were greater when piglets had to compete with a resident piglet with the same teat preference and all were still evident in the third of the three observation hours.

Studies on the aerobic deterioration of whole-crop cereal silages.

Abstract: As a result of the treatment of made whole-crop barley silage with antimicrobial agents which are specifically inhibitory to fungi or bacteria, it was shown that the subsequent aerobic deterioration was essentially caused by yeasts. These microorganisms were instrumental in the rise in pH, the increase in temperature and the loss of dry matter observed. The filamentous fungi, like one group of bacteria (the streptomycetes), apparently had no part in the process. Bacteria, such as the lactobacilli and particularly proteolytic bacteria, may have had a role in the terminal stages of deterioration, although it was considered more likely that the yeasts again were involved.The whole-crop wheat silage employed in this work was stable in air, a factor attributed to the combined antimicrobial effects of butyric acid present and the relatively high dry-matter content.

The effect of lactation on protein synthesis in ovine skeletal muscle

Abstract: SUMMARY Protein synthesis was measured in non-breeding sheep and in sheep at two stages of lactation by constant intravenous infusion of [3H] tyrosine. In early lactation plasma tyrosine flux was 50% higher than in non-breeding ewes and it remained somewhat higher in late lactation. Estimates of protein synthesis per day in the whole body showed similar changes. In early lactation the weights of the longissimus dorsi and semitendinosus muscles were respectively 37 and 28% lower than those for non-breeding ewes, but both muscles regained weight in late lactation. There were corresponding changes in the total protein, total RNA and total lipid contents of both muscles. The fractional rates of protein synthesis in the longissimus dorsi and the semitendinosus were between 2 and 3% per day, but it was higher in heart muscle. At both stages of lactation the synthesis rate in the longissimus dorsi was similar to that in nonbreeding ewes, but in the semitendinosus and in the heart synthesis rates were lower in lactating animals. In both skeletal muscles the total protein synthesized per day was lower in early lactation because their total protein contents were lower at this time. It is concluded that the maternal skeletal muscles may undergo a controlled depletion during lactation.

Endogenous faecal loss of calcium by ruminants

Abstract: A re-examination of the results from 374 sheep used in previovis studies of calcium metabolism show there is a highly significant linear relationship between endogenous faecal loss of Oa and food intake, endogenous loss increasing by about 0·64 mg/day/kg body weight for each 1 g/day/kg body weight increase in food intake. This loss was unaltered by Ca intake or by pregnancy and lactation but was slightly higher in young animals than in adult animals given the same Ca intake on a body-weight basis. It is suggested that a variable factor for endogenous Ca loss, based upon some measure of level of feeding, should be introduced into rationing schemes.

The effects of light illuminance and wavelength on the growth of broiler chickens

Abstract: The effects of light illuminance and wavelength on the growth of male and female broiler chickens from day-old to 8 weeks of age were studied.Different coloured lights, at equal illuminance and peak wavelengths of 425, 525 and 610 nm and a broad-spectrum white light of median wavelength 560 nm had no significant effect on the growth rate or cumulative food intake of birds of either sex.The performance of male broilers was unaffected by light of different illuminances, equal to 0·7, 3·0, 15·0 and 46·5 lux. The weight gain of female broilers, adjusted for food intake, was progressively depressed at illuminances above 3 lux.There is probably no commercial advantage in using broad-spectrum white light at intensities above 3 lux.

Effect of root zone temperature on early growth, nodulation and nitrogen fixation in soya beans

Abstract: SUMMARY Soya-bean plants were grown for 40 days in a range of root temperatures from 10 to 25°C either in a root medium containing N but uninoculated or in a N-free medium but inoculated with Rhizobium japonicum. Low root temperature restricted growth in both cases but the plants depending solely on symbiotic N-fixation were much more affected. At 10 CC root temperature plants failed to nodulate but both nodulation and nitrogen fixation increased greatly in the range 15–25°C. It is concluded that soya beans sown in cool soils would benefit from applied nitrogen at sowing time.

Nutritional evaluation of kale ( Brassica oleracea ) diets:4. Responses to supplementation with synthetic S-methyl-L-cysteine sulphoxide (SMCO)

Abstract: Synthetic SMCO was added to basal diets of either fresh kale or lucerne at the concentrations 0, 0·2, 0·4, 0·8 and 1·6% D.M. and each diet offered ad libitum to groups of four lambs that were individually fed indoors. Within each group, two lambs were of haemoglobin genotype AA and two were AB. Initial live weight (W) was 21 kg and the experiment lasted for 6 weeks.SMCO supplementation depressed voluntary intake, body growth and wool growth, caused the development of haemolytic anaemia and produced kidney hypertrophy. Effects were much more severe when SMCO was added to a kale than to a lucerne diet, with the lowest SMCO intake of kale-fed lambs (0·3 g/kg W) producing marked detrimental effects whereas the highest SMCO intake of lucerne-fed lambs (0·7 g/kg W) produced only small and transient effects. The intake depressions were evident during the first week of SMCO supplementation and persisted throughout the full 6-week feeding period. Approximately 80 and 65% of the changes in body growth and wool growth could be accounted for by changes in intake, and it was concluded that the most important effect of SMCO in ruminant diets is as an intake depressant.It is suggested that the greater ratio of soluble to structural carbohydrate in kale (2·3) compared with lucerne (0·9) probably resulted in a microbial population developing in the rumen of kale-fed sheep that could metabolize SMCO to dimethyl disulphide at a faster rate than occurred in the rumen of lucerne-fed sheep. Dimethyl disulphide production is postulated as the cause of both the haemolytic anaemia and appetite depression. Plasma SMCO concentrations did not increase with increasing SMCO intake in sheep fed either diet, indicating that there must have been negligible absorption of this amino acid from tho digestive system.No haemoglobin C was produced by any of the lambs fed lucerne, and kale-fed lambs produced significant amounts only during weeks 5 and 6, with type AA lambs producing more than type AB lambs. However, there was no difference between AA and AB lambs in rate of decline in total haemoglobin concentration or upon voluntary intake, body growth and wool growth.

An investigation of resistance to the white potato cyst-nematode

Abstract: SUMMARY The inheritance of resistance to Globodera pallida was studied in seedling progenies derived from Solanum tuberosum ssp. andigena CPC 2802 (H3) and S. vernei and compared with resistance to G. rostochiensis derived from S. tuberosum ssp. andigena CPC 1673(H1). The resistance of CPC 2802 was originally thought to be due to a major gene (H3), but results presented here demonstrate that it and that derived from S. vernei are inherited in a similar manner quite distinct from the major gene inheritance from CPC 1673 (HI). It is concluded that the resistances derived from CPC 2802 and S. vernei are both polygenic in nature. These findings are discussed in relation to breeding policy and screening methods.

The digestion of untreated and formaldehyde-treated soya-bean meals and estimation of their rumen degradabilities by different methods

Abstract: The effect of treating soya-bean meal with formaldehyde was studied in cattle by supplementing a hay–barley diet with two levels of either untreated or formaldehydetreated soya-bean meal. The formaldehyde treatment had no significant effect upon apparent N digestibility in the whole tract; it increased the amounts of non-ammonia N and amino acid N entering the small intestine but this increase was not statistically significant. However, increasing the proportion of either soya-bean meal in the diet increased the flow of non-ammonia N to the small intestine and apparent N digestibility in the whole tract. The formaldehyde treatment reduced the apparent degradability of the soya-bean meal N, determined in vivo from 0·74 for the untreated meal to 0·38 for the formaldehyde-treated meal. The in sacco technique produced values for the apparent degradability of the two soya-bean meals which ranked them in a similar manner as did the in vivo technique but gave lower values for degradability than the in vivo technique.

An evaluation of the use of dihaploids and unreduced gametes in breeding for quantitative resistance to potato pathogens

Abstract: In a breeding programme to combine quantitative resistance to two important potato pathogens, Phytophthora infestans causing late blight in foliage and Qlobodera pallida (the cream potato cyst-nematode), tetraploid (4 ×) off spring were obtained by crossing dihaploids, mainly as females, with tetraploids. Glasshouse and field tests in the first and second tuber-years showed that most of the off spring of highly blight-resistant dihaploids had high resistance to P. infestans. Two such dihaploids, PDH 182 and PDH 247, crossed with a tetraploid selected for high general combining ability for potato cyst-nematode (PCN) resistance, gave off spring all of which were highly blight resistant. About one third also had high PCN resistance.Detached leaflet tests were used for rapid blight resistance screening of other progenies from dihaploid × 4 × crosses in their seedling year. Differences were found in the effects of 4 × parents on the mean resistances of progenies from blight-resistant dihaploids.The results also showed differences between dihaploids in their effectiveness in transmitting blight resistance to 4 × offspring. This could be due to differences in the mode of unreduced female gamete formation, i.e. first division restitution or second division restitution (SDR). If all the unreduced gametes were produced by SDR, the differences could be due to differences in homozygosity between dihaploids with respect to blight resistance genes.The dihaploid × 4 × crosses gave few offspring per pollination. The few seedlings obtained may be offset by a higher frequency with the required characters. Since fewer seedlings would have to be grown in order to find the required combination of characters, savings could be made in planting and resistance-testing facilities over those required in conventional breeding.The tetraploid hybrids obtained can be used in a second cycle of breeding in three ways simultaneously: by crossing with other tetraploids, by crossing with dihaploids selected for complementary characters and to produce dihaploids with combined resistances.

Energy as the basis of harvest index

Abstract: Harvest index has become a character used in plant breeding programmes and in evaluation of responses to agronomic treatments (Donald & Hamblin, 1976). Donald (1962) defined harvest index as the ratio between weight of grains and the weight of total dry matter, and later described it as a measure of partitioning of photo - synthates (Donald, 1968)