A 2·year grazing trial was carried out on an equatorial Themeda triandra range grassland in the Rift Valley of Kenya, at 1890 m altitude with a bimodal rainfall of 700 mm p.a., to characterize seasonal changes in the pasture and to determine the influence of climatic and management factors on forage availability and composition, grazing selection and live-weight gains on Boran steers (Bos indicus).

Fourteen categories of sampling and measurement techniques used in this work are described and some methodology problems in rangeland evaluation discussed.

For precise estimation of herbage yields in large paddocks unacceptably large plotsizes and numbers were required so an arbitrary sample of twelve 10 yd x 1 yd plots per paddock was adopted giving c.v.s of 16–50%. Subsequent sampling was limited to three contrasting treatments in the most uniform block. A ‘forceps point’ method was developed for botanical estimation of oesophageal fistula samples and provisional weight correction factors calculated. In a parallel feeding trial regressions were calculated for relating the chemical composition of oesophageal fistula samples to that of the herbage ingested.

The environment, design and methods of this 2-year Kedong grazing trial in the Rift Valley of Kenya were described in Part I.

Crude protein of grasses varied seasonally, usually between 3 and 6 %, while most shrubs and herbs, leguminous and non-leguminous, were in the 10–20 % range, although contributing only about 3 % by weight of the total sward, excluding large bushes and trees. Steers selected herbage of 2–3 % units higher C. P., more Themeda leaf and more herbs than the sward average. Treatment effects on sward and diet C. P., and their relationships, were generally small and inconsistent. Higher C. P. in post-burning ro-growth declined to average levels after 2–3 months, except when grazed at one steer to 4–4 acres, rotational (i.e. 1–5 acres available). At this pressure available herbage fell below 1000 lb D.M./acre (1120 kg/ha). In all other treatments 2500–4500 lb D.M./acre wore available at all times. Estimated herbage production varied from almost nil to 320 lb D. M./acre/month. Burning removed 3000 lb D.M./acre. Relationships between herbage C. P., diet c. p. (oesophageal fistula samples) and faeces N were determined.

An analysis of germination characteristics of progeny from a diallel cross between five sugar-beet plants showed that the genotype of the maternal parent controlled to a marked extent the behaviour of the progeny. This may be related to the presence in the fruits of inhibitory substances.

Some evidence was found for genie and maternal interactions but these were always of less importance than the maternal effects. Heritability estimates from parent, off spring regression and analysis of half-sib family variances demonstrated that genetic variation for germination characteristics had not been eliminated during the improvement of sugar beet from the wild form.

The two experiments described here were the 3rd and 4th in a series of experiments investigating the effect of time of application of nitrogen and potassium on the growth and yield of potatoes.

The effect of applying all the fertilizer nitrogen in the seed bed was compared with applying all the nitrogen at the time of tuber initiation or dividing the dressing between these times. Similar times of application were tested for potassium. CCC was applied after a leaf area index of 3 had been reached (on all but the no N treatments) in order to offset the tendency for late nitrogen to increase stem growth, but to avoid any tendency for CCC to depress yield by reducing leaf area indices (L) below an assumed optimum value of 3. These treatments were applied in separate experiments to a second early variety (Craig's Royal) and a maincrop variety (Pentland Dell), planted a month later.

In both crops the response to nitrogen was large and delaying or splitting the application of nitrogen increased tuber yield compared with nitrogen applied in the seed bed. Responses to potassium were small, but there was a tendency for split applications to be superior to late or early applications.

The beneficial effect of delayed or split applications of nitrogen was associated with an improvement in the recovery of nitrogen in the crop which was largely ascribed to a reduction in loss due to leaching. Total and tuber dry-matter yields were linearly related to leaf area duration (D) in both crops, although the earlier variety was more efficient per unit of D. High values of L (6) were recorded for both crops, but there was no indication of an optimal value of L; consequently CCC which reduced L also reduced yield. D was closely related to the maximum quantity of nitrogen accumulated in the leaves per unit area of ground.

In four series of experiments Merino ewes were exposed to ambient temperatures of about 44 °C and water vapour pressure of 33 mmHg for 9 h daily, and to 32 °C and 18 mmHg for the remaining 15 h daily, during the middle third, the final third or the final two-thirds of pregnancy. Birth weight and the weight of the placenta were considerably reduced by the treatments and the reductions were considerably more than could be accounted for by the partial loss of appetite produced by heating.

There was a close inverse relationship between birth weight and the elevated rectal temperature of heated ewes in several series; but the absence of foetal dwarfing in ewes with elevated rectal temperatures due to daily heating for only 9 h at 44 °C indicates that the elevated rectal temperature of the ewe is not the main cause of dwarfing.

Contrary to previous suggestions, the dwarfed lambs were not proportional miniatures, for the head components, the body lengths, the kidneys and adrenal glands were disproportionately large in heated lambs, while the liver, thyroid and thymus glands and the biceps femoris muscle were disproportionately small, and the ratio of secondary to primary wool fibres was very much reduced. There were cavities in the white matter of the cerebral hemispheres of heat-dwarfed lambs.

The hypothesis that foetal dwarfing is due to stunting of the placenta was examined, but conflicting evidence was obtained in the different series. However, it appears that under some circumstances a heat-stunted placenta is capable of considerable growth in the absence of heating during the final third of pregnancy, when the placenta is normally shrinking, and that placental shrinkage in late pregnancy may be greatly accelerated by the application of heat.

Neither thyroxine nor a preparation of ovine growth hormone, injected into heated ewes, prevented foetal dwarfing; the injections of growth hormone appeared to increase foetal mortality.

An experiment, involving 68 female pigs, was undertaken to measure the effects of two diets differing in protein content, and of two patterns of feeding. The animals were housed in an enclosed building. The experiment extended through several parities; culled sows were replaced by gilts during the experiment, the whole course of which lasted 5 years.

The diets were given at the rate of 1–8 or 2–3 kg per day throughout gestation, but the rate was reversed during the 5-week lactation so that, for litters of eight to nine pigs sows in each treatment group received the same quantity of food per parity. As a result of unsatisfactory performance, dietary composition was changed after 2 years so that for the last 3 years the digestible energy contents were higher.

Treatments significantly influenced gestation live-weight gain, lactation weight loss and gestation backfat gain. The lower rate of gestation feeding was associated with low or negative gestation weight increases after the third to fourth litters, and a greater apparent rate of decline with increasing age in birth and 3-week weight per piglet. The high gestation, low lactation, rates of feeding led to slightly greater litter size and lower weaning weights per pig. A daily intake of 208 g crude protein and 8'3 g lysine appeared to meet the sow's requirements throughout gestation.

In the pregnant sow feeding area, winter air temperatures were on average 16 °C below those in the summer, but were rarely below freezing point. Winter backfat gain was lower than, and gestation gain only half that in the summer. Litter size was also greater following summer pregnancies and 3-week weight per pig was greater following winter pregnancies. Independent of litter size, birth and 3-week weight per pig were positively correlated with gestation gain within treatment and season. The apparent positive correlation of litter size at 3 weeks with gestation backfat and weight gain was not found at birth. Litter size at birth was negatively correlated with gestation gain within season. The percentage of fertile matingswas less for matings between 1 September and 31 January. This coincided approximately with the reduced litter size (alive) which occurred following winter gestations.

Lactation weight loss and 3-week weight per pig declined with increasing age of sow and the degree of weight loss was unrelated to subsequent litter size.

The apparent effect of seasons and treatments on litter size at birth appeared not to be an obvious function of changes in live weight, which were also marked between seasons and treatments, but level of food intake in early gestation may have affected litter size independently. It was concluded that birth weight especially in the older sows, was associated with the rate of food intake in gestation, and possibly also in lactation, and with gestation empty weight gain.

The phosphorus requirement of the buffalo (Bos bubalis) for maintenance has been determined from the data of two feeding and balance experiments each with twelve animals in randomized block designs and one with six animals using 3x3 latin square designs in duplicate. The level of phosphorus intake was varied by adding appropriate quantities of sodium dihydrogen phosphate in Exp. 1, by adding wheat bran in Exp. 2 and by adding dicalcium phosphate in Exp. 3.

Regressions of phosphorus outgo (7) on P intake (X) gave values of 14–7 g/day in Exps. 1 and 2 and 17–2 g/day in Exp. 3. These values can be taken to be estimates of the P requirement of the adult buffalo for maintenance.

The initial and final serum inorganic phosphorus in Exp. 1 also indicated that the phosphorus requirement was between 12 and 17 g/day.

Field experiments were carried out in central Scotland to assess the lime and fertilizer dressings required for the establishment and growth of grasses and clovers on deep acid peat. Without lime, the sown grasses and clovers failed when ammonium sulphate and mono-ammonium phosphate were used, but with Nitro-Chalk and single superphosphate a poor establishment was obtained. With adequate P, lime at rates as low as 0–25 metric ton Ca per ha produced a marked improvement. The yields obtained with 1, 2 or 4 metric tons Ca per ha were similar, but the herbage from the last treatment contained the highest Ca percentage.

Even with adequate lime, the grasses and clovers failed in the absence of applied P. Superphosphate and basic slag gave similar establishments but the former produced higher yields. Ground mineral phosphate was inferior to basic slag in the first and second years but in the fourth, fifth and sixth seasons it was equal to superphosphate and superior to slag. After establishment the 98 kg P rates were always better than the 49 kg levels. The 490 kg P treatment of superphosphate did not produce a bigger yield than the 98 kg rate, but it did give a higher percentage of P in the herbage.

Dressings of N and K had appreciable effects on establishment and growth, especially on the botanical composition of the sward and yield of herbage produced in the second year.

The effects of treatment on the pH value of the peat and on the Ca, P and K extracted by 2·5 % acetic acid were measured. To get a satisfactory establishment of grasses and clovers on deep acid peat it is suggested that about 3 metric tons Ca, 35 kg N, 100 kg P and 140 kg K per ha should be applied.

Stocking rates of 3, 6 and 9 acres per 2- to 3-year old steer on Acacia-Cymbopogonj Themeda complex pasture in Ankole, Uganda, demonstrated that 3 acres per head gave significantly lower individual live-weight gains, but that there was little difference between 6 and 9 acres over a 6-year period. Although cattle grazed at 3 acres averaged only 175 lb per head per annum, compared with 207 lb at 6 acres per head, the income was Sh. 34 per acre compared to only Sh. 20–50 at 6 acres per head. At 9 acres/head the return was Sh. 13–50 an acre.

A comparison of a 2 paddock/1 herd system with continuous grazing revealed no differences in production, despite the heavier capital investment involved in the former system. Growth rates at all three stocking rates were similar for most of the year, but in the dry season when all the cattle lost weight those stocked at 3 acres per head suffered the greatest losses (50–60 lb) and those at 9 acres per head the least (20–30 lb).

The current status of herbage grass breeding is considered in relation to the utilization of first-generation hybrid vigour. A breeding scheme is outlined by which it is suggested that interpopulational F1 hybrid varieties could be developed to provide a simple and effective means of exploiting heterotic potential in herbage grass species. A survey of interpopulational F1 heterosis expressed, under two levels of fertility in non-competitive spaced-plants conditions, by the hybrids of a group of six adapted perennial ryegrass varieties, is reported here.

Although the F1 hybrid populations studied were not on average superior to the parental varieties there were large variations between specific hybrids. Two hybrids were particularly promising, exhibiting 25% and 31% heterosis over the higheryielding of their parents for total green-matter yield over two harvest years and two fertility levels. The bulk of this heterosis arose under high-fertility conditions, when the mean yield response of the interpopulational F1 hybrid was twice that of the parental varieties.

The effects of inherent relationships between the parental varieties on the observed levels of heterosis are considered, as are the possibilities for the practice of recurrent selection procedures for the enhancement of heterotic expression in some of these hybrids. It is concluded that there is sufficient evidence for the existence of interpopulational heterosis in this species to merit an extension and application of this approach to include a wider range of varieties and. populations, both adapted and introduced.

Triple superphosphate (21.6% P), potassium metaphosphate (25.0% P) and magnesium ammonium phosphate (19.0% P) were compared as phosphate fertilizers alone and in combination, and as powders and granules, in two experiments on acid soils. Basal nutrients were adjusted to allow for the amounts of N, K, and Mg in the test fertilizers. Immediate effects of the fertilizers were measured by early potatoes and barley, and residual effects by radishes and ryegrass.

All powdered fertilizers, alone or in combination, were equivalent to powdered superphosphate for early potatoes. The value of granular fertilizers for potatoes increased with the proportion of superphosphate in the mixtures. Superphosphate equivalents of the granular fertilizers were: magnesium ammonium phosphate, 14%; potassium metaphosphate + magnesium ammonium phosphate, 36%; potassium metaphosphate, 53%; superphosphate + potassium metaphosphate + magnesium ammonium phosphate, 54%; superphosphate + magnesium ammonium phosphate, 60%; superphosphate + potassium metaphosphate, 81%.

Residues from powdered fertilizers, applied to potatoes, were equivalent, for radishes, to residues from powdered superphosphate. Residues from granular fertilizers were more effective for radishes than residues from powders.

All powdered fertilizers were equivalent to powdered superphosphate for barley cut green. Granular magnesium ammonium phosphate, either alone or mixed with potassium metaphosphate, was slightly less effective than powder.

Residues from all powdered fertilizers applied to barley were equivalent for ryegrass. Residues from granular fertilizers, especially potassium metaphosphate and magnesium ammonium phosphate, produced more grass than residues from powders.

Apparent recoveries of P by the four crops ranged from 24% to 32% and were more from granules than from powders. Residues from all fertilizers increased 0.5M-NaHCO3-soluble P in soils, and mean yields of ryegrass, the final test crop, increased by 3.2 to 5.1 cwt dry matter/acre/ppm NaHCO3-soluble P in the soils.

Several criteria which have been used hitherto in the hope of selecting large-yielding clones of tea have been examined. The heights, girths, root weights and branching a gles of young seedlings in the nursery are correlated with the sizes and yields of the same plants when mature, but not with the rates of growth in the nursery, or the yields at maturity, of the plants derived from these seedlings by vegetative propagation. The pruning weight, size and yield of a mature plant grown from seed are not related to the rate of growth in the nursery or the yield at maturity of the clone derived from that plant. The proportion of cuttings which form roots and the growth rate of the cuttings of a clone are not related to the yield of the clone. It is concluded that these criteria are, at best, of limited value in the selection of large-yielding clones.

Phloem Index, which is the number of calcium oxalate crystals counted in the phloem parenchyma in a cross-section of the petiole, varies with the age and rate of development of the shoot from which the petiole is taken and with the concentration of nutrients in the soil. It is therefore not useful as an alternative selection criterion under normal field conditions.

1. When roughage rations of medium to high quality were given to steers and aduit sheep, the excretion of non-dietary faecal nitrogen was positively related to the intake of truly digestible dry matter. In these experiments no significant relationships were noted between non-dietary faecal nitrogen excretion and the intake of either truly digestible nitrogen or truly indigestible dry matter.

2. When concentrate rations containing 1.6–3.2% nitrogen were given to lambs weighing 19–27 kg the excretion of non-dietary faecal nitrogen was positively and significantly related to the intake of both truly digestible dry matter and truly indigestible dry matter, but not related to the amount of truly digestible nitrogen consumed.

3. Grinding and pelleting a grass ration for steers resulted in an increase in the excretion of non-dietary faecal nitrogen and bacterial + endogenous debris nitrogen, of 28 and 30% respectively, compared with the chopped material.

4. It is concluded that these responses reflect the dominating influence of nitrogen of microbial residues from the rumen and hind-gut on the excretion of bacterial + endogenous debris nitrogen and non-dietary faecal nitrogen.

Attempts were made to relate various parameters of growth in wheat substitution lines to final yield of grain and assess the extent to which such relationships could be useful as early predictors of yield. The associations were measured by calculating correlation coefficients, partial regression coefficients, standard partial regression coefficients and independent contribution to yield. Significant correlation coefficients were common but significant partial regression coefficients were rare. The remaining estimates provided a ranked order of characters associated with yield. Those parameters of vegetative growth showing most association with final yield were themselves related fairly directly to ear and grain size. It was concluded that direct estimates of yield must remain the most appropriate character on which to base selection in cereals.

Casein in amounts ranging from 10 to 124 g/day was administered as an abomasal infusion to seven Merino wethers whose daily ration comprised 600–700 g of either chopped wheaten hay alone or a mixture of chopped wheaten and lucerne hays. Increases in both the length growth rate and diameter of the wool occurred at all levels of supplementation tested. When casein was infused at the rate of 100 g/day for a 20-day period the biggest increases in wool growth occurred during the first 4 days and there was little further change after the first 8 days.

There were marked wool growth responses to the infusion of up to 80 g casein per day. The results suggest that little further increase could be expected with the infusion of more than 120 g/day.

Despite the fact that early embryo mortality commonly leads to the loss of 25% of fertilized ova in ewes (Edey, 1969), little is known of factors associated with this loss. Severe, acute undernutrition (Edey, 1966) and high ambient temperatures (Dutt, Ellington & Carlton, 1959) are specific factors which are known to cause embryo death, but these do not normally occur in most sheep producing areas.

Intravenous glucose tolerance tests were performed on thirty-four sows when they were either non-pregnant or in very early pregnancy. It was found that there was a relation between each sow's glucose tolerance and the mean of the mean birth weight of all her litters. The relation was expressed by the equation Y = 0.013T + 0.81 (R.S.D. ± 0–124 kg) where Y = birth weight and T = glucose tolerance as minutes for blood glucose to return to fasting concentration. The correlation coefficient was +0.58. The addition of further variables to the equation (sow's live weight at test, sow's parity at test and the number of pigs per litter) did not give any useful improvement of the estimate of birth weight.

The wool growth cycle in six rams and eight ewes was studied by taking monthly coat and skin samples for 3 years from each. Coat length was measured, and the percentage of inactive follicles was noted as well as the percentage of medullated fibres.

In the spring moult ‘mainland’ sheep (stock removed from St Kilda 60 years ago) cast less completely than ‘St Kilda sheep’ (Soays removed more recently from St Kilda). Mainland rams cast less than the ewes, but St Kilda rams began casting earlier, and completed casting more quickly than the ewes. Despite differences between years in the rate of casting, similarities in the pattern of casting were observed between years in the same animal, and between parent and offspring.

This apparent annual cycle was confirmed by graphs of follicle inactivity which showed that most inactivity occurred from September to March in the rams, and from October to April in the ewes. It was possible to fit sin and cos waves of 12-month duration to the graphs and further analysis revealed superimposed a 6-month cycle in one group, and a 4-month cycle in another group, which were associated with subsidiary peaks of inactivity in the summer. There were suggestions of a cycle about 2 months in length throughout the year, and sin waves of this duration could be fitted to the data from one of the groups of ewes. Possible control mechanisms for the annual and shorter cycles are discussed.

Peaks of follicle inactivity were frequently followed by troughs in coat length which suggested actual loss of the longest fibres.

Medullation was absent or minimal from December to March, and there were two peaks during the period of maximum medullation, that in the spring being greater than the one in the autumn.