The water content and turnover of six pairs of identical twin cattle were measured in the Kenya highlands. Three pairs were stall fed, and one twin of each pair received water daily. Their water turnover averaged 14.21./24 hr. while the others watered each 4 days had an average turnover of 12.41./24 hr. These stall-fed animals used 74-132 ml./kg.0.82/ 24 hr., about one-third the water turned over by grazing cattle (261-364 ml./kg.0.82/24 hr.). There was little relationship between estimates of water intake measured from the trough and that derived from tritium dilution.

Members of each grazing pair differed in weight by an average of 4.2% and their total body water by 5.9%, whereas the water turnover differed by only 2.2% amongst the twin pairs.

The dry-matter yield, in vitro digestibility and crude protein content of four varieties of spring cereals (one barley, one wheat and two oats) were examined at weekly intervals at two levels of nitrogen fertilization during two successive years. The ensiling characteristics of crops cut at two dates were also determined. Dry-matter yields increased until the end of July. Digestibility and crude protein content declined until mid July when values of 56–60 and 6–7% for the barley and wheat, and 53–55 and 5–6% for the oats respectively were maintained. Crops of all varieties were suitable for ensiling at maximum yield.

Other experiments investigating level of whole-crop cereal yields obtainable with higher levels of fertility produced yields of over 16 metric tons D.M./ha with applications of 200–250 kg N, P2 O5 and K2O per hectare.

The effect of maturity on the nutritional quality of hay from two alfalfa varieties and four grass species was studied. Each hay was harvested at six different stages of growth, chopped in 4–6 cm lengths, and fed to sheep in quantities of 10% in excess of voluntary intake. The relationship between intake (Y) and digestibility (X) of dry matter was best expressed by regressions of the form: Y = a + b1X + b2X2. The rate of intake declined 1·5 g daily per kg0·75 of body weight per unit decrease in digestibility percentage, and was the same for both alfalfa and grass hays. However, the intake of alfalfa hay was about 10% higher than that of the grass hays of similar digestibility. No differences in the relationship between intake and digestibility (P < 0·05) were observed between the two alfalfa varieties or between the four grass species. When the nutritional quality was expressed as voluntary intake of digestible organic matter daily per kg0·75 of body weight, and time of harvest as day-number of the year, the difference in quality between the six kinds of hay was very small or absent at the beginning of the season (immature to prebloom) and increased toward maturity (dough stage to seed ripe). The decline in quality of alfalfa hay was slower than that of grass hay, and ceased at the mature to overripe stage. On the average, voluntary intake of digestible organic matter declined 0·29 g daily for each day delay in harvest time; this decline varied from 1·2% of the daily intake of digestible organic matter in the beginning of the season to 0·6% at the mature stage. Time of harvest ‘accounted for’ 77–89% of the variation in the quality of the hays. The confounded effect of maturity and leanness on the nutritional quality of the hays was expressed best by concave, second degree polynomial regressions. On the average a unit decline in percent leaves corresponded to a decline of 0·58 g and 0·73 g respectively in the daily intake of digestible organic matter from alfalfa and grass hay. This varied from over 1 g early in the season to less than one tenth of a gram late in the season. The confounded effect of leafiness and growth stage ‘accounted for’ over 75% of the variability in nutritional quality. The relationship between intake and digestibility of the alfalfa and grass hays was used to illustrate how voluntary intake of metabolizable energy (percent of requirement for maintenance) from hay of pure or mixed species may be predicted from in vitro digestibility.

Trials were established at two sites in 1982 to compare six 2-course rotations, in which barley alternated with feed legumes (pure or mixed with barley), fallow or barley, in partial factorial combination with different N and P fertilizer regimes. This paper summarizes data from the second to the seventh cropping seasons.

Barley yielded most after fallow and more after legumes than after barley; but, on the basis of total dry matter production over both courses, barley-legume rotations outyielded barley-fallow and barley-barley rotations. In terms of net nitrogen offtake, which may be taken as a rough measure of feed value, barley-legumes surpassed the other rotations by c. 100% at both sites, whether the comparison was made on values obtained from plots with or without added fertilizer. Of the legumes, Lathyrus sativus was slightly more productive than Vicia saliva, and this carried over into the rotational yield of both dry matter and nitrogen. Rotations involving pure legumes were slightly more productive than those involving legume/barley mixtures.

Yields of all crops and rotations varied greatly from year to year depending on rainfall. Those of the barley-fallow rotation were much less variable than those of the barley-barley rotation at the wetter site (323±103 mm), with the barley-legume rotation intermediate; but variability was much greater at the drier site (250±79 mm), with much less difference between rotations. Nevertheless, fertilizer use and rotations including legumes gave a significant yield advantage under the driest conditions.

The effects of contrasting management systems either of infrequent rotational grazing by town milk supply dairy cattle, or of frequent defoliation by continuously grazing sheep and beef cattle, on the morphology of independent plants and populations of ‘Grasslands Roa’ tall fescue in mixed pastures, were measured over 1 year (1992/93) in New Zealand. Volunteer perennial ryegrass plants were also measured for comparison.

While both species exhibited a similar pattern of clonal growth, tall fescue developed more plants of higher branching complexity than perennial ryegrass, chiefly through maintaining more connective stems, as herbage production was confined to the three youngest branching orders in both species. Greater resistance to microbial degradation of old stems through poorer quality organic matter (wide C[ratio ]N ratio) compared to perennial ryegrass may be responsible for the greater complexity of fescue plants. In addition, tillering rates in tall fescue were three times lower which was offset by greater longevity and size of leaves and tillers, compared to perennial ryegrass. As a result, seasonal fluctuation in the distribution of plants among the various branching orders in tall fescue was small, producing a more stable population relative to the distinct seasonal changes in the population of perennial ryegrass plants. Grazing management had no effect on the seasonal population structure in either species.

Differences in plant structure due to grazing management were small, with only slightly more tillers on sheep-grazed than on cattle-grazed tall fescue plants. The major effect of grazing management was on dry weight or size of plant components. Cattle-grazed tall fescue plants were 120% heavier, with greater numbers and lengths of stolons and flower heads than those under sheep grazing. For the volunteer perennial ryegrass, the difference was only 65%, possibly due to competition from the more vigorous tall fescue under rotational cattle grazing.

Both species produced stolons throughout the year, although these were primarily associated with reproductive growth in spring. In tall fescue, an additional distinction was made between stolon and rhizome, the latter occurring mainly in the summer–autumn. Their possible functions in plant growth are discussed.

Twelve sorghum lines resistant to sorghum shoot fly were evaluated for their combining ability for shoot fly resistance and traits associated with resistance, using three male sterile lines in two environments. Using a completely randomized block design with three replications, 36 hybrids and 15 parental genotypes were raised. Considerable genetic variation was observed for all the traits studied. Non-additive gene effects played an important role in governing glossiness, seedling vigour and proportion of plants with deadhearts. For trichome density, both additive and non-additive gene actions were important. Among the lines evaluated, those identified to be good combiners were SFCR 1047 for seedling vigour, deadheart proportion and trichome density, RSE 03 for glossiness, deadheart proportion at 21 DAE and trichome density, and SPSFR 94032 for seedling vigour and shoot fly eggs per plant. Genetic diversity and cluster analysis grouped the 15 parents (12 resistant and 3 susceptible parents) into five clusters. Utilization of the resistant lines belonging to different clusters in improving shoot fly resistance in sorghum is discussed.

Forty-eight Hereford × Friesian steer calves purchased at 7–10 days of age were reared on reconstituted milk substitute and groups of 12 were weaned at 86, 128, 170 or 212 days. Six calves at each weaning age were fed high (H) and low (L) quantities of milk normally associated with 240-day lactation yields of 2000 or 1000 kg. Calves were housed until day 63 of the experiment and then strip-grazed on swards of Loliun perenne with a daily allocation of herbage dry matter equivalent to 60 g/kg LW.

Herbage intake per unit live weight prior to weaning was consistently greater for the calves receiving low quantities of milk. Following weaning there was a rapid rise in herbage intake towards a maximum of 30 g OM/kg LW when sward conditions were non-limiting. The amount of milk fed prior to weaning affected herbage intake after weaning, and H groups did not achieve similar intakes to their L contemporaries until some weeks after weaning. The H groups grew faster from birth to weaning than the L groups but they experienced a more severe check in live-weight gain after weaning which nullified the advantage of better weight gains between the start of the grazing period and weaning. In consequence, there was no significant effect of the quantity of milk consumed prior to weaning upon live-weight gain during the grazing season. The results indicate a marked benefit from distributing a given quantity of milk over a longer feeding period as similar growth rates occurred for the H86 v. L128, H128 v. L170 and H170 v. L212 groups. Calves receiving milk consumed less herbage and spent a smaller proportion of the day grazing than weaned contemporaries, which suggests that metabolic rather than physical or behavioural factors are likely to limit their intake.

Winter wheat (Triticum aestivum L., cv. Hereward) was grown in the field within four double-walled polyethylene-covered tunnels along which near-linear temperature gradients were imposed at normal atmospheric or at an elevated CO2 concentration (c. 700 μmol mol−1 CO2) in 1991/92 and in a further experiment in 1992/93. Development was more rapid the warmer the temperature. In 1991/92 an increase in mean seasonal temperature of 3·5 °C reduced the duration from sowing to harvest maturity (the stage when grain moisture content reduced naturally to 15–18%) by c. 38 days, and reduced the duration from the double ridge stage to harvest maturity by c. 34 days. A similar difference resulted from only 1·6 °C warming in 1992/93. Although the range of mean seasonal temperatures differed between years, the relation between temperature and rate of development from sowing to harvest maturity was common to both years (base temperature, −0.8 °C; thermal time 2410 °C d). Carbon dioxide concentration had no effect on this relation or on that between temperature and the rate of development from sowing to the double ridge stage and from the double ridge stage to harvest maturity. Carbon dioxide enrichment increased tillering substantially in 1991/92; there were 200 more shoots m−2 at terminal spikelet formation in crops grown at elevated compared to normal CO2 (additional shoots were principally coleoptile tillers and those developing after tiller 2) and this difference was reduced to 100 shoots m−2 approaching harvest maturity (additional shoots remaining were those developing after tiller 2). In contrast, no effect of CO2 enrichment on tillering was detected at any stage of development in 1992/93. The number of tillers per plant at terminal spikelet formation was a linear function of main stem dry weight at this developmental stage; this relationship was not affected by year or CO2. As CO2 enrichment increased main stem dry weight in the first year only, when main stem dry weights at normal CO2 were only one half of those values determined in the following year, it is concluded that any benefit of increase in CO2 concentration to tillering in winter wheat may be greatest in those crop production environments where main stem dry weights at terminal spikelet are least and vice versa.

Castration of males is a long-established practice in animal husbandry, and although the use of boars rather than hogs was advocated by Fitzherbert in 1534 the use of castrates in pig production has continued to the present day.

The movement of water in soil, and the manner in which water is distributed over the particles and within the interstices, i.e. the dynamical and statical aspects respectively of moisture distribution, are of fundamental importance in soil science. The literature of the subject abounds with experimental determinations, but the difficulties of theoretical treatment are great, and it is only within recent years that any serious attempts have been made in this direction.

Sulphur (S) is one of the six main macroelements required to sustain the growth of plants. Sources include soil, fertilizer and atmospheric deposition, which has been reduced by 85% over the last three decades. Risks of S deficiencies are now recognized in high S-demanding species such as Brassica napus L. With the aims of evaluating the risk of excessive or insufficient fertilization and identifying robust relationships that may be used as plant S status indicators, 57 commercial crops of oilseed rape were selected among contrasting soils and along a rainfall gradient that may affect soil S availability. Cultivation practices were investigated and the S and nitrogen (N) concentrations of soil, senescing leaves, stems and seeds were analysed. Despite an excessive organic N supply and large variation in S supply (from 0 to 112 kg S/ha), principal component analysis using 43 parameters indicated that seed yield was poorly related to N and S fertilization rates. While the N and protein-N concentrations in seeds were inversely related to oil and glucosinolate concentrations, they were linked to S and sulphate (SO42−) accumulation in the seeds. Sulphate concentrations in senescing leaves, stems or seeds could be deduced from total S concentrations, as they were positively and highly correlated. Sulphate accounted for on average 0·69 of total S in senescing leaves with minimum and maximum values of 0·007 and 0·94, which revealed conditions of limited and excess supply of S, respectively. This high variation of SO42− concentration in leaves can be interpreted as the result of its mobilization triggered by S deficiency, but cannot be used alone as an indicator of plant S status. A comparison with plants grown in controlled conditions under different S supplies suggests that the intensity of S starvation affects N metabolism, leading to NO3− (nitrate) accumulation. It is further suggested that dual evaluation of SO42− and NO3− concentrations in senescing leaves could be used at the vegetative stage as a field indicator to adjust S fertilization.

It has been known for a long time that there exist varieties of wheats and other cereals which appear to be practically free from, or immune to, the attacks of certain fungal parasitic pests, by which closely allied forms are ravaged.

When open flowers were removed from cowpea plants for periods between 3 and 12 consecutive days beginning from the first day of anthesis, more flowers opened on the deflowered than on the untreated plants, thus compensating for those removed. However, most of these extra flowers dropped prematurely.

In experiments in the greenhouse or on dry-season irrigated plots, deflowering for up to 9 days did not decrease the seed yield of the varieties Adzuki or Westbred. In an early-season field experiment, deflowering of Westbred did not decrease the seed yield unless repeated for 12 days. All periods of deflowering Adzuki decreased the seed yield, and the longest period gave the smallest yield.

The effects of plant population (one-tenth of the optimum to four times the optimum populations in 1998/99 and 10–400 plants/m2 in 1999/2000) and sowing depth (2, 5 and 10 cm) on yield and yield components of four grain-legumes (Cicer arietinum, Lens culinaris, Lupinus angustifolius and Pisum sativum) were studied. Seed yields were strongly positively correlated with the number of pods and seeds/m2 in both years in all species. The mean seed weight and number of branches/plant were inversely related to plant population. There was a nearly six-fold reduction in the number of branches/plant as plant population increased, which was due to restricted branching, and not to branch senescence. Generally, the variation in yield components was species dependent. However, for all species the number of pods/m2 and seeds/m2 could be used as primary criteria for selection in a breeding programme.

When incoming radiation was reduced artificially to 50% daylight during the postflowering period in peas, the rate of abscission of flowers and pods increased in the same way as when the density of planting is raised. Shading from flowering onwards reduced yield almost to the level of peas that were shaded throughout the growing season, even though peas that received full daylight until flowering had many fertile tillers and a greater reproductive potential in terms of the total number of flowers produced. Conversely, when shades were removed at flowering time the crop was able to compensate and yields approached those of peas grown entirely in full daylight, this was mainly due to a reduction in absoission losses of flowers and pods so that the majority of pods formed on the main stem contributed to final yield.

It is suggested from these results that the major source of dry matter for pea yield is the photosynthate produced during the post-flowering period rather than that translocated from roots or stems following storage during the vegetative period.

Agroforestry systems can play an important role in mitigating the effects of climate change given their capacity to increase tree diversity and to store more carbon than conventional farming. This study aims at assessing carbon stocks and the use of shade trees in different coffee growing systems in the Northeast Peruvian Amazon. Carbon stocks in trees were estimated by field-based measurements and allometric equations. Carbon stocks in dead wood, litter and soil (upper 60 cm) were determined using field sampling and laboratory analysis. The diversity analysis drew on the Shannon–Weiner diversity index, and focus groups were used to obtain information about the local use of shade trees. The total carbon stock in the polyculture-shaded coffee system was 189 t C/ha, while the Inga-shaded and unshaded systems totalled 146 and 113 t C/ha, respectively. The soil compartment contributed the largest carbon stock in the coffee growing systems and contained 67, 82 and 96% of the total carbon stock in the polyculture-shaded, Inga-shaded and unshaded coffee systems, respectively. The Shannon–Weiner index and tree species richness values were highest for the polyculture-shaded coffee system, with a total of 18 tree species identified as important sources of fodder, food, wood, firewood and medicine. Therefore, coffee agroforestry systems play a significant role in carbon storage, while promoting conservation of useful trees in agricultural landscapes in the Peruvian Amazon.

Neem (Azadirachta indica juss) seed kernel cake was water treated and dried in the sun. It was palatable to cattle, despite its bitter smell.

Twelve growing calves were divided into two equal groups; one group (control) had a standard concentrate mixture consisting of crushed maize 30 parts, groundnut cake 30 parts, wheat bran 38 parts and in the second group (experimental) the concentrate mixture had crushed maize 30 parts, neem seed kernel cake (water washed) 45 parts and wheat bran 23 parts. Both the mixtures had common salt and mineral mixture 1 part each. The roughage fed was the same in both groups.

The mean growth rate of calves in 273 days was 403 g/day in the control group and 344 g/day in the experimental group which did not differ significantly (P > 0·05). The dry-matter intake, digestibilities of all the organic nutrients, total digestible nutrient values and the balances of nitrogen, calcium and phosphorus remained similar (P > 0·05) in the two groups. The blood haemoglobin, serum inorganic phosphorus and the activity of serum alkaline phosphatase, serum acid phosphatase, serum glutamic-pyruvic transaminase and serum glutamic-oxaloacetic transaminase also did not differ significantly (P > 0·05) in the two groups.

It is concluded that water washing of neem seed kernel cake very largely removes toxic principles responsible for retardation in growth.

1. The efficiency with which Ayrshire calves digested the dry matter of fresh grass was measured over two trial periods extending from the third to the tenth week of age.

2. A statistical method for determining digestibility coefficients is outlined and its advantages over the conventional procedure, particularly for young growing animals, are discussed.

3. The mean coefficient of digestibility of the dry matter of the grass for four calves was 74·6%.

4. This digestive efficiency was attained immediately the grass was fed and did not vary throughout the experiment.

5. Simultaneous feeding of milk in the first trial period did not affect the digestion of grass.

A series of tropical maize hybrids, involving 10 single, four double and four three-way crosses were evaluated with their parental inbred lines and three control varieties, at Universiti Putra Malaysia, Serdang, Malaysia, in a randomized complete block design, with three replications. The objectives were to identify hybrids superior for yield, yield components and other agronomic traits, to estimate heterosis revealed by the hybrids, and to estimate broad-sense heritability for important characters in the populations. The hybrids were found to vary highly for grain yield and most other traits measured. High estimates of heterosis were shown by grain yield, ear weight and grain weight per ear, moderate for plant and ear heights, shelling percentage, ear diameter, number of kernel rows per ear, number of kernels per ear row and 100-grain weight. The hybrids flowered and matured earlier than their respective inbred parents. Estimates of broad-sense heritability also varied with characters. Moderate heritability was shown for grain yield indicating a substantial amount of genetic variation in this population of hybrids. Low and negligible heritability for days to silking and 100-grain weight indicate that these traits were very much influenced by environmental factors. Based on the overall performance of the hybrids, the single cross, SC-2, the double cross, DC-11 and the three-way cross, TWC-15, were found to have high potential. No obvious differences were observed in performance among the three categories of hybrids, the single, double and three-way crosses.

Voluntary intakes of a medium-quality grass hay were measured in winter (early January) and in spring (late April) near Edinburgh for two separate groups of six red deer, together with digestibility and mean retention times of the particulate-phase marker, 103Ru-phenanthroline. The deer were then slaughtered and the weights of digesta and the dimensions of the alimentary tract were measured. Voluntary intakes of dry matter were significantly higher in spring than in winter, but there was no difference in digestibility or mean retention time of 103Ru-phenanthroline. There were no significant differences in any of the organ weights or the dimensions of the intestines between the groups slaughtered in winter and spring. Dry matter proportions of digesta in the rumen, abomasum, small intestine and caecum, the wet and dry weights of rumen digesta and the water-filled capacity of the rumen were significantly greater in spring.