1. The availability of K in potassium metaphosphate was investigated in an experiment with large pots using a red sandy soil, low in exchangeable potassium. Potatoes were grown. The effects of potassium metaphosphate in three different granule sizes, applied at two rates, were compared with those of equivalent potassium chloride and potassium sulphate.

2. Characteristic deficiency symptoms appeared in plants receiving no K and the crop responded to K fertilizer in potassium concentration, yields of tubers, and dry matter, and starch concentrations.

3. Potassium metaphosphate, regardless of granule size and of application rate, was as effective as potassium chloride and potassium sulphate in giving normal development of potato plants, high potassium uptake in the foliage, and yield of tubers.

Recent studies on maize in Nigeria showed that the new ‘FARZ series’ of maize, which were specially bred for high yield, respond to high density treatments (Lucas, 1981; Remison & Lucas, 1982). The optimum maize grain yields were obtained by these workers at density treatments 6·6 and 5·3 plants/m2. Prior to the release of these varieties, optimum grain yields were obtained between 3·7 and 4·3 plants/m2 (Fayemi, 1963; Chinwuba, 1967).

Two fattening experiments are reported with 60 cross-bred bulls. In the first experiment three pen groups (9–16 months old) of eight Simmental, eight Friesian and eight Jersey crosses, from Boran and Barca dams, were fed for 98 days on a common diet consisting of maize cobs, molasses and concentrate. There were no significant differences among sire or dam breeds, with the Barca cross bulls performing non-significantly better than the Boran crosses. Simmentals and Friesians consumed about the same amount of feed and the latter were the most efficient feed converters. In the second experiment, 36 bulls ranging from 11 to 18 months of age were fed for 51 days diets consisting of either 30 or 50% maize stalks and concentrate; maize stalks were replaced by maize/sorghum silage for the next 61 days. There were no significant differences in rate of gain between sire breeds. Bulls from Boran dams gained faster (P < 0·01) than those from Horro dams while a higher (P < 0·05) daily gain was recorded for the diet with the lower than with the higher percentage of maize stalks.

1. An experiment was conducted to study the effects of progesterone and pregnant mare serum (p.m.s.) on incidence of oestrus, macroscopic changes in the ovaries, histological appearance of the genital tract, the vaginal smear and cervical mucus of New Zealand Romney Marsh ewes in deep anoestrus. Ten animals served as controls, thirty-five received progesterone daily for 4–12 days and ten were given p.m.s. alone. The remaining fifteen ewes were treated with progesterone for 4–6 days followed by p.m.s.

2. In ewes treated with progesterone alone, neither ovulation nor oestrus resulted. After p.m.s. alone six animals ovulated, while injection with both hormones caused ovulation in all 15 ewes and one was in oestrus.

3. Sections cut from the mid-region of the fallopian tube, uterine horn and cervix were examined. Histological responses to progesterone and p.m.s. were found in all positions of the tract and were greatest in the ewes which had ovulated.

4. In the ewes which ovulated a sequence of macroscopic and microscopic changes occurred in the vagina and these seemed similar to those associated with ovulation during the oestrous cycle.

5. Crystallization patterns in cervical mucus were seen in some ewes of all groups. Accompanying ovulation the phenomenon was seen for several days but was absent during most of the luteal period. When no follicles ruptured cervical mucus patterns often persisted. In most cases the presence and absence of arborization was presumably related to follicular oestrogen and progesterone from an induced corpus luteum and was in similar time relationship to that normally accompanying ovulation in the oestrous cycle. Some inconsistency in the response of cervical mucus following hormone treatment was noted.

6. No evidence was found that hormone treatment had initiated a regular cycle of ovarian activity.

The effects of changing plant density and nutrient supply on the yield of swedes were measured in nine experiments over 3 years. With small populations, a large nutrient supply was required to reach the maximal yield of roots, but with large plant populations the same nutrient rate depressed yield. This interaction is illustrated by a response surface, and reasons for it are discussed. The interaction is of limited importance in practice because it was small over the range of population and nutrient supply commonly used. Even with small populations, the compensation achieved by applying more fertilizer was uneconomic. On crops with large populations, such as swedes for human consumption, however, the normal recommended rate of fertilizer should not be exceeded because of loss of yield as well as increased cost. More fertilizer and greater plant density were needed to give maximal total yield (roots + tops) than of roots alone. Effects of nutrient supply and plant population on plant establishment and dry-matter content of the swedes are discussed.

1. Samples of faeces obtained from eleven continuous digestibility trials in which sheep, steers or cows were given fresh herbages grown in different seasons in 2 years were analysed for the ‘dissolved faeces fraction’ (D.I-.F.).

2. Dry-matter intake by sheep was linearly related to the weight of D.F.F. excreted and the equation predicted intakes that were 20 %higher at the mean intake than those estimated from a similar type of relationship obtained by Owen (1961). A logarithmic relationship was derived when the observations for all species were combined.

1. The effects of birth weight, sex, twinning, parity of dam and dry season on mortality rates of lambs were studied between birth and weaning at 20 weeks in a flock of East African Blackheaded sheep.

2. The mean birth weights of non-surviving lambs were lower than those of surviving lambs. Singles from gimmers and twins from ewes were 0.5 and 1.0 lb., respectively, lighter at birth, and had higher mortality rates than singles from ewes. The overall mortality rate of singles from ewes was 16%, singles from gimmers 20% and twins from ewes 28%. Male and female lambs born alive had similar mortality rates (18%).

Few problems have been reported with the use of the isotope dilution technique for measuring volatile fatty acid (VFA) production in the rumen of sheep. However, early studies carried out in this laboratory, using a standard technique (Leng & Leonard, 1965) showed serious limitations associated with losses of activity from the infusates. Subsequent inquiries suggested that other laboratories had experienced similar problems (J. D. Sutton, National Institute for Research in Dairying, Shinfield, and D. E. Beever, Grassland Research Institute, Hurley, personal communication). When solutions of [U-14C]Na acetate, [l·14C]Na propionate and [l·14C]Na butyrate obtained from the Radiochemical Centre, Amersham, were each diluted with deionized water to provide 0·5 μtCi μtmol/ml (hereafter designated 14Ac, 14Pr and 14Bu respectively) and left to stand at room temperature for 6 h, losses of activity of C, 15 and 3% respectively were found.

The variations in fleece components over the body of the Blackface sheep are described. The differences amongst regions are relatively large and highly significant. The structural components—density, fibre type ratio and weight per unit area—are more variable than the fibre characteristics—weight, length and diameter. Fairly regular patterns are found which approximately correspond to those found in other breeds and there is evidence of significant animal by site interaction. It is concluded that neither fixed nor random site sampling can be regarded as ideal but that the best procedure would be single or multiple sampling in the mid-side region.

Analyses of data on first peak yields of 1346 Holstein Friesian (HF) × Sahiwal crossbred cows belonging to four Indian military dairy farms were carried out. There were highly significant differences amongst different grades. The < ⅛ HF had the minimum (9·35 kg) and £ HF had the maximum (12·77 kg) peak yield during first lactation. Half-breds appeared to be most suited for peak production. Genetic grades, farms and periods of calving had highly significant, and season of calving had significant, influences on peak yield in cross-bred cows. Heritability of peak yield was 0·405±+ 0·023. Peak yield had highly significant and positive genetic and phenotypic correlations with total lactation yield, 300-day milk yield, milk yield per day of first calving intervaland milk yield per day of age at second calving. Interval, in days, between the dates of first and second calvings was considered the first calving interval. Age, in days, at the time of second calving was considered age at second calving. The high heritabilities and desirable correlations indicate the possibility of satisfactory correlated response in thesetraits, if selection is based on peak yield.

An investigation has been described in which an attempt has been made to measure the losses of dry matter in a number of regularly spaced layers of silage contained in a tower silo, the immediate object being to determine the average loss of nutrient matter in the entire mass of material. The work was continued over the period of two silage seasons. The more important findings are summarised below:

1. It is usually asserted by writers on ensilage that the attainment of such high temperatures as are necessary for the production of “sweet” silage necessarily involves an excessive loss of the dry matter of the crop as a consequence of the oxidation of carbohydrate. This statement has been shown to be erroneous both on theoretical grounds and on the grounds of actual measurements of the losses of dry matter entailed in the production of “sweet” silage. The amount of destruction of carbohydrate bears no significant relation to the temperature attained during preservation, and the factors of (a) juice drainage, (b) bacterial decomposition of carbohydrate, (c) partial spoiling by undesirable bacterial activity, as with “sour” silage, are of much greater significance in causing unduly large losses of carbohydrate.

2. The results obtained in this investigation with crops containing from 26·5 to 33·9 per cent. of dry matter show that “acid brown” silage can be made in the tower silo with an average loss of dry matter equal to 5–6 per cent. of that contained in the green crop. It is further concluded that “sweet” silage, if made under good conditions, can also be produced in the tower silo with an average dry matter loss of the same order. With “green fruity” silage, the average loss under proper conditions of ensilage in tower silos is of the order of 8–9 per cent. The evidence affords strong disproof of the statement that the ensilage of green crops cannot be accomplished without large losses of nutrient matter.

A number of mutant lines showing different levels of improved quantitative resistance to bacterial leaf blight (BLB) were obtained through selection of plants or lines derived from seeds of the rice cultivar Harebare exposed to thermal neutrons and gamma-rays. The selections were made on M2–M4 materials under natural BLB-epidemic conditions and/or by artificial inoculation of one of the BLB isolates. Bacterial isolates predominating under the natural conditions were identified as belonging to the differential BLB isolate group I, and the isolates of this group were used in the artificial inoculation for selection of mutants. The selected M4 mutant lines were tested in M5 for BLB resistance by artificial inoculations of four differential bacterium isolates, groups I, II, III and IV. The M6 mutant lines showed quantitatively elevated resistances to the isolate of bacterium group I and also to the other three differential isolates. Analysis of variance of the data demonstrated that the observed elevated quantitative resistances of the mutants to the isolates I, II, III and IV were isolatespecific. Host-parasite interactions in quantitative resistance to BLB and their modification by induced mutations are discussed.

In earlier studies, results from incubation experiments were combined with measurements of outflow rates of small particles from the rumen to predict the extent of degradation of dietary protein in vivo (Orskov & McDonald 1979). The degradability of a protein supplement was shown to decrease when fractional outflow rate increased (Orskov 1982). In a series of experiments, the factors affecting the fractional rates of outflow of dietary protein supplements from the rumen of sheep and lactating dairy cows were investigated (Agricultural Research Council 1984). In addition, outflow rate of soyabean meal from the rumen of dry and lactating Chios sheep and Damascus goats offered high concentrate diets was determined in recent studies (Hadjipanayiotou et al. 1988). Chromium-treated protein supplements were used to measure their outflow from the rumen using the marker concentration in faeces (Ørskov 1982). This paper reports outflow from the rumen of growing Chios lambs and Damascus kids offered concentrates ad libitum.

A study was conducted to compare field crops and varieties grown at the Kufra Agricultural Project, Libya, and the Imperial Valley Field Station, El Centro, California. Lucerne (Medicago sativa L.), barley (Hordeum vulgare L.), wheat (Triticum octivum L.), sudangrass (Sorghum bicolor Moench) were grown at both locations in 1969–70.

Yield studies at Kufra, Libya, and the Imperial Valley Field Station indicated that the crop performances were equally well adapted at both locations. Lucerne yields were higher at Kufra, which may have been due to more moderate temperatures and less salt in soil and water at Kufra. Low yields in some of the other crops at Kufra such as wheat may be due to inexperience and inadequate fertilizers. Newly developed varieties for Imperial Valley should be adapted to the Kufra area.

Percentages of soluble dry matter (S.D.M.), determined in expressed sap from the pith of kale stems by using a hand refractometer, were higher near the vascular bundles than in the centre of the pith and also varied from the top to the base of any one stem. Sampling errors were minimized by taking vertical borings midway between the vascular bundles and the pith centre and by taking two bores per stem (base and top). Inbred lines varied for mean S.D.M. Relative S.D.M. values for two inbred lines were maintained through wet and dry periods in the autumn, and values for fifty-eight inbred lines were significantly correlated in the successive years, one with a dry autumn and the other with a wet.

S.D.M. values were positively and significantly correlated with dry-matter percentage (D.M.) of the pith and with total water soluble carbohydrates (W.S.C). Close correlations were also found between S.D.M. and resistance to cold damage, both in the field and in freezing cabinets for inbred lines of marrow-stem kale and for other cultivars of Brassica oleracea. Although there are some exceptions to these correlations, the rapid method for determining S.D.M. should be very useful in screening breeding material for cold resistance. The combination of high percentage digestibility of the dry matter of stems and improved winter-hardiness can be achieved by selecting in addition for low fibre content using penetrometer tests.

Previous work has shown that the technique of laparoscopy in anaesthetized ewes is a practical and reasonably accurate method for the diagnosis of pregnancy between 17 and 28 days after conception and for estimating numbers of foetuses (Phillippo et al. 1972). This method in common with other reported endoscopic techniques for sheep positions the animal on its back, necessitating the use of either general anaesthesia (Roberts, 1968; Boyd & Ducker, 1973) or tranquillization and local anaesthesia (Kelly & Allison, 1976). These methods have the disadvantages of the necessity to withhold food and water for up to 24 h prior to surgery and the risk associated with general anaesthesia and the positioning of the animal. A new procedure with the sheep standing was therefore developed from the method used in cows (Mariana, 1969; Wishart & Snowball, 1973).

In dealing with fertility in sheep there are a number of initial difficulties. On the one hand, there is generally a lack of any uniform definition of such terms as ‘fertility’, ‘fecundity’ and ‘prolificacy’ (cf. Marshall & Hammond, 1947; Lush, 1938; Rice, 1942; Asdell, 1946; and others); on the other hand, investigators have been confronted with a real difficulty in procuring suitable information which would conform to the requirements of any single and adequate definition of fertility. Because of this, fertility figures have been calculated in different ways* and may differ by as much as 30%. The situation is at present so confused that reference to similar work, especially when the original papers are not available, or the terms not clearly denned, is often of dubious value if not altogether misleading. In the past the data analysed were mostly based on farmers' answers to questionnaires or on flock records. The limitations of such methods are only too obvious; yet it must be clearly realized that in commercial flocks there is no possibility of any basic departure from them, even though their accuracy could in many cases be improved. In other words, only such information is collected as the circumstances allow. This, for instance, may be the number of lambs docked per ewes put to ram in one flock and number of lambs docked per ewes lambed in another.

The yield and chemical composition of Sabrina hybrid ryegrass and RvP Italian ryegrass were compared, with special reference to regrowth after defoliation in spring and early summer. Initial cuts were taken on 6, 20 April and 4. and 18 May; subsequently a conservation crop was harvested at either 5 or 7 weeks, and a second regrowth 30 days later. There were four fertilizer treatments. Tiller density, stem development and individual tiller dry weight were recorded in selected treatments.

At the initial cuts and in the conservation crops after the first three initial cuts, varietal differences in yield and dry-matter digestibility (DMD) were relatively small. In all other harvests, RvP was appreciably higher yielding than Sabrina, and it showed greater responses to fertilizer in all second regrowth harvests. The water-soluble carbohydrate (WSC) content of RvP was consistently higher than that of Sabrina in regrowth harvests; the DMD was higher in Sabrina.

In primary growth of the two cultivars, tillering was suppressed at the time of head emergence, but active tillering was resumed earlier in RvP, the later-heading cultivar. In RvP, tillers arising early in the regrowth periods attained head emergence within 5 weeks. In Sabrina there was a marked decline in head production during June, and an increase in the size of individual vegetative tillers.

In regrowth harvests both the yield and the % WSC were markedly reduced when drought conditions were most severe; the most marked varietal differences occurred at this time, both in terms of yield of dry matter and % crude protein responses to fertilizer treatment.

In the two cultivars the DMD of 7-week conservation crops harvested in late May was at least equal to that of 5-week crops harvested later during drought conditions. A distinctly more advanced stage of development was attained in the earlier, heavieryielding crops.

Vigorous cauliflower plants sometimes bear abnormally small curds, yet this common problem has received little recognition or attention from research workers. Curd size is often reduced towards the end of the harvesting period of a crop, and this is more marked if environmental conditions reduce mean curd size and lengthen the time to maturity. Small late curds may be a consequence of their slow growth rather than their late initiation. Cultivars differ in their tendency to produce plants with late maturity and small curds. This may not be due to genetic differences within cultivars. Moreover, breeding to eliminate or reduce this condition may not be possible without affecting overall maturity time and curd size.

1. A digestibility trial is described using sheep fed on the product remaining after herbage leaf-protein extraction.

2. The material gave an analysis of 25.7% dry matter, 16.2% crude protein, 0.26% phosphorus, 1.26% potassium and 1.13% calcium.

3. The animals showed no loss in body weight during the feeding period.

4. The material was of low palatability, and the sheep consumed a maximum of 2½ lb. of dry matter per head daily.

5. The average digestibility coefficient of the dry matter was 52.1% and that of the crude protein 67.6%.

6. Nitrogen balance determinations indicated a sufficiency of protein in the feed.

7. The material barely supplied sufficient potassium and was inadequate in its supply of phosphorus and calcium.