The mammary gland is controlled at two levels in the body. The genetically controlled pattern of parental investment during lactation is modified by nutritional status and signalled to the mammary gland by the endocrine system (see Peaker 1989). The response to this strategic control of the rate of milk secretion is modulated by a tactical control mechanism operating within each mammary gland. The local intramammary mechanism responds to changes in the frequency or completeness of milk removal and acts to match the rate of milk secretion to the rate of milk removal by the young or, in dairy animals, by the milker. It is the local control of milk secretion by milk removal which has been uncovered in recent years, following the realization of the physiological significance of unilateral effects of frequent milking in goats (Linzell & Peaker 1971) and cows (Morag 1973) that is the subject of this brief review.

A study of 76 F1 hybrids involving four sources of cytoplasmic male sterility and 19 male-fertility restorers indicated great diversity among the cytoplasms for total soluble solids. The exploitation of cytoplasms other than milo is recommended for breeding programmes aimed at high total soluble solids content. Most of the Indian restorers showed significant positive general combining ability (GCA) effects, whereas exotic restorers showed negative GCA effects for total soluble solids content.

Two steers totally nourished by intragastric infusion of volatile fatty acids and casein were given an abomasal infusion of a microbial protein preparation (Pruteen) at eight rates with a purine input ranging from 0 to 170 mmol/day over 11 successive 5-day periods. The urinary excretion of purine derivatives relative to the purine input was measured. Negligible amounts of xanthine plus hypoxanthine were present in the urine. The relative contributions of allantoin and uric acid to the total excretion were not affected by the rate of purine infusion. Total purine derivative excretion (uric acid and allantoin) was linearly correlated with purine input. Recovery in the urine of the infused purines was 0·77. It is suggested that utilization of exogenous purines may only occur in the intestinal mucosa and that the remaining purines may be completely converted, before entering the liver, to uric acid and allantoin, which are subsequently eliminated by the renal and extrarenal routes. The differences between cattle and sheep in excretion of purine derivatives, and the implications of these differences for the use of purine excretion values in order to estimate microbial protein supply to the ruminant, are discussed.

Wheat straw (WS), paddy straw (PS), farmyard manure (FYM) and water hyacinth (Eichhornia crassipes) compost (WHC) were applied at four rates and on four dates before transplanting to the rice cultivar Ratna, in a pot experiment at Kharagpur, India in the wet (first crop) and dry (second crop) seasons of 1985/86. Grain yield of the first crop increased significantly with increasing rates of FYM and WHC up to the equivalent of 15 t/ha but, with the application of WS and PS, the yield was greatest at 10 t/ha and decreased at 15 t/ha. On the other hand, yield increased appreciably when WS and PS were applied up to 30 days before transplanting (DBT) but, with FYM and WHC, such increases were less pronounced. The effect of higher rates (10 and 15 t/ha) was more pronounced with early application of organic materials (20 and 30 DBT). Residual soil fertility estimated by organic carbon and available N, P and K increased under all the organic materials, which favourably influenced growth and yield of the second crop grown without supplementary fertilization. The residual effect of increasing rates of WS and PS in increasing grain yield was significantly higher than with FYM and WHC.

Compositional analysis of feeds and other materials by near-infrared reflectance (NIR) has been proposed as a cheap and rapid alternative to traditional wet chemical methods. A theoretical basis for NIR measurements is needed and may be obtained from the study of artificial mixtures of pure chemicals.

Mixtures of lactose, casein and sodium oleate, in widely differing concentrations, were analysed by NIR. Principal component analysis was used to study the variations between spectra, and multiple linear regressions gave predictors of sample compositions from the spectra. Optical densities at most combinations of wavelengths gave good predictions of sample compositions because there was much less unexplained variation between NIR spectra than would occur between natural samples.

On a clay loam soil, the cultivar Col 148, planted in spring 1987 at 57560 three-budded setts/ha received 0, 75, 100 and 150 kg N/ha and 0, 10, 20 and 30 t/ha fresh sulphitation press mud either separately or in combined applications, at 80% moisture. Separate applications of up to 150 kg N/ha and up to 30 t press mud/ha increased the cane biomass by 24·6% and 13·2%, respectively, whereas combined application increased it up to 38·1% more than in the control. A N concentration of 1·95–2·12% in the blades of leaves 3·6 from the top of the plant from tillering to the grand growth stage was necessary for maximum dry matter production. Sulphitation press mud enhanced uptake and availability of N and P to the crop and reduced soil pH. Application of 10 t press mud/ha saved 75 kg/ha of fertilizer N.

Eight feeds were treated with seven solvents and the proportion of seven mineral elements (Ca, Mg, P, Na, K, Cu, Zn) released was assessed. Six of the feeds were from Sri Lanka (Panicum maximum ecotype Guinea A, Glyricidia maculata, Artocarpus heterophyllus, untreated and urea-treated rice straw, and rice bran) and two from the Netherlands (maize silage and wheat straw). The solvents were water, tris buffer, rumen fluid from a cow deprived of (RF -) or fed (RF +) mineral supplements, neutral detergent solution with (NDS +) or without (NDS -) EDTA, and acid detergent solution (ADS).

Both the type of feed and the solvent significantly influenced (P < 0·01) the amount of dry matter loss and the proportion of minerals released. Maize silage released over 80% of its minerals, except Cu, in water and tris buffer, probably because of the low pH (3·7) during ensiling. The other feeds differed widely in their ability to release minerals. In general, P, Na and K. were more soluble in water than Ca, Mg and Zn.

Mineral concentration in RF influenced not only the amount of minerals released, but also the extent of sorption by the feed. The latter effect was more pronounced in feeds with low mineral concentration, maize silage being no exception.

Treatment with NDS+ and ADS removed all minerals except Cu. With all feeds, 12–34% and 5–34% of the Cu remained in the ND and AD residues, respectively, indicating its association with the cell wall. Results of the NDS- treatment showed that some of the Ca and Mg may be associated with the cell wall.

Comparison of the feeds across the different solvents tested indicated that, in terms of absolute quantity of mineral released, G. maculata could be a good source of Ca, Mg, K and Cu, and that rice bran is a good source of P and Zn. The variety of rice straw tested released high amounts of Na. A. heterophyllus is rich in available Ca.

Serial sowings of three cultivars of oilseed rape were made from autumn (May) to spring (October) at two sites, one in the north and one in the south of Tasmania, in 1981. The highest seed yields at both sites exceeded 5 t/ha from early sowing, ranging down to c. 2 t/ha from late sowing at a site where irrigation was adequate and to < 1 t/ha where late-sown crops suffered from water stress. The midseason cultivar Marnoo gave the highest yields at both sites, resulting from a combination of substantial (800 g/m2) top growth before flowering, excellent seed survival, a long period for grain filling and high oil content. The early-flowering line RU1 made much less growth before flowering; while this was partly made up for in later growth, nearly as many seeds per pod being retained as in Marnoo, oil content was low. The later-flowering cultivar Wesbell made more growth before flowering than the other cultivars, but when sown early it tended to grow tall, lodge and lose many pods in the dense, tangled canopy. This, combined with generally fewer seeds per pod, resulted in a much less efficient crop in allocation of dry matter to seeds and oil. Wesbell failed to flower uniformly from the late sowings, indicating segregation for vernalization response. The many immature seeds at harvest gave a low overall oil content. All three cultivars responded to vernalization and longer photoperiod in a pot experiment. While photoperiod appeared to be the main factor controlling the development rate to flowering in the field, there were interactions with vernalization response andtemperature.

Inadequate soil moisture is one of the main constraints on the productivity of chickpea in the rainfed farming systems of the dry areas in West Asia and North Africa. The response to irrigation at flowering and pod filling of winter- and spring-sown kabuli chickpea was studied in 1983–86 at ICARDA's main research station at Tel Hadya in northern Syria. In 1983/84 when the cultivar ILC3279 was sown in winter, irrigation increased yield by 105% over a crop receiving 229 mm of precipitation. In 1984/85, ILC3279 was sown in winter and spring. Advancing the date of sowing to winter increased yield by 65% and irrigation increased seed yield by 73% in winter and 143% in spring sowings compared with crops grown receiving 373 mm rainfall.

In 1985/86, six cultivars (ILC482, ILC3279, FLIP81–57W, FLIP81–293C, FLIP84–19C and FLIP84–80C) were compared, but differences in their response to irrigation were negligible. Advancing sowing from spring to winter increased seed yield by an average of 66%. Irrigation increased seed yield in winter and spring sowings by 56% and 72%, respectively, over those receiving 316 mm annual precipitation. Irrigation is, therefore, a way of increasing the productivity and yield stability of chickpea in northern Syria but the improvement in yield depends on the total rainfall and its distribution over the growing season.

Measurements were made of the recovery and germination rates of seed of eight species of annual medic (Medicago spp.) and three of clover (Trifolium spp.) after ingestion by sheep. Recovery of medic seed was measured as the number of seeds collected from faeces after feeding, in addition to a basal diet, either (i) 200 g of pods at a single meal, or (ii) a quantity of pods estimated to contain 30000 seeds at a single meal or (iii) 200 g of pods daily for 21 days. Only the first method was applied to the clovers.

There were large differences (P < 0·001) in seed recovery between species, from < 2% to nearly 20% in medics, and up to 59% in T. campestre, which has low single-seed mass. Although there was a curvilinear decrease in seed recovery as single-seed mass increased (r2 = 0·80), the high recovery of M. rotata, a fairly large-seeded species, suggests that there are important differences between species, irrespective of seed size.

When 200 g of medic pods was offered to sheep at a single meal, mean seed recovery was slightly lower than when 200 g of medic pods was offered daily for 21 days. Seed recovery of medics was much higher (P < 0·001) when 30000 seeds were offered at one meal.

Germination rate before ingestion was 1·9–6·5% (P < 0·001) for hard-seeded medics and 2·7–9·7% (P < 0·001) for clovers with low single-seed mass; passage through the digestive tract increased (P < 0·001) germination rate in both medics and clovers.

Effects of hedgerow species on surface soil physical properties were studied in an on-going trial established since 1981 on an Oxic Paleustalf in southwestern Nigeria. The experimental treatments were Leucaena leucocephala, Gliricidia sepium, Alchornea cordifolia and Acioa barterii hedgerows planted at 4 m interhedgerow spacings and a control (no hedgerows). Plots were sequentia-ly cropped with maize (Zea mays) and cowpea (Vigna unguiculata). Soil physical properties, i.e. particle size distribution, bulk density, apparent pore size distribution and water infiltration, were monitored during the dry season in January and the main growing season in June 1989. Soil temperature was monitored at approximately monthly intervals from February to June 1989. Soil properties of alleycropped plots were superior to those of the control. Soil compaction was highest in the control and lowest with L. leucocephala. Between the hedgerow species, within-season increases in soil compaction were largest with A. cordifolia. Lowest soil temperatures were observed with L. leucocephala and A. barterii. Frequency, quantity and quality of prunings produced by the hedgerow species appeared to have a major beneficial effect on soil physical properties.

Lentils (Lens culinaris Medik.) were sown on eight sowing dates from April to November in two seasons in Canterbury, New Zealand. In 1984/85, six sowing dates were combined with two lentil cultivars (Olympic and Titore) and two irrigation treatments. In 1985/86, Titore was sown on two dates, with four irrigation treatments. An additional experiment grown under rain shelters examined the response of Titore to four irrigation regimes. The 1984/85 season was dry and rainfall was only 70% of the long-term mean. In this season, seed yield was high, 3·3 t/ha from the May sowing. The 1985/86 season was wetter than average and seed yields were lower, ranging from 0·6 to 1·5 t/ha. Under rain shelters, seed yield ranged from the equivalent of 0·32 to 2·5 t/ha.

Sowing date had the most marked effect on seed yield. In the 1984/85 season, all autumn and winter sowings yielded 2·4–3·3 t/ha, whereas the spring sowings yielded 0·5–1·5 t/ha. In 1985/86, unirrigated plots from the May sowing yielded 1·5 t/ha, whereas all other plots yielded c. 0·8 t/ha.

Generally, the small-seeded cultivar Titore outyielded Olympic. Dry matter (DM) accumulation followed similar trends to seed yield. Seasonal DM accumulation followed a sigmoidal curve. Functional growth analysis indicated that plants from autumn/winter sowings had a weighted mean absolute growth rate of 110–171 kg/ha per day, whereas spring-sown plants grew at 96–137 kg/ha per day. The maximum crop growth rate was 230 kg/ha per day in the July 1984 sowing.

There was little positive response to irrigation in both seasons. Under rain shelters, there was a linear increase in both dry matter and seed production with increased total water. Fully irrigated plants produced 1·27 g DM and 0·72 g seed/m2 per mm of water received.

In the field experiments there was no relationship between maximum potential soil moisture deficit (D) and yield. Under rain shelters, however, there was a linear relationship which indicated a limiting deficit of c. 130 mm. The relationship showed that, for each millimetre increase in D above D1, 0·39% of the maximum yield was lost.

Under the rain shelters, there was a strong relationship between yield and actual evapotranspiration (ET). Water-use efficiency (WUE) ranged from 2·81 g DM/m2 per mm ET in unirrigated plots to 0·69 g seed/m2 per mm ET.

The results showed that lentil growers in Canterbury, and presumably in similar environments, are unlikely to benefit from irrigating their crops. In such environments, lentils appear to be an ideal dryland crop.

Irrigation experiments are described in which three cultivars were subjected to varying degrees of drought in the cool and hot seasons in Lima, Peru. The most severely draughted plots received, on average, 20% and 35% less water than the well-watered control plots, resulting in 20% and 52% yield reduction in the cool and hot seasons, respectively. Average fresh tuber yields ranged, according to cultivar, from 1370 to 2450 g/m2 in the summer and from 2800 to 4450 g/m2 in the winter, with tuber dry-matter percentages of c. 17% and 20%, respectively. The production of total dry matter per unit intercepted solar radiation (the conversion coefficient, estimated from the slope of the regression, in g/MJ) was markedly less during the hot season but, regressed on a photo thermal quotient ∑((MJ/m2)/(°C > 4·5°C)), a common relationship across seasons was achieved. The conversion coefficient was less in draughted than in well-watered plots, more so in the hot season.

Crop transpirational and evapotranspirational water use efficiencies (WUE) were less in the hot season largely because of the greater saturation vapour-pressure deficit. However, because of greater harvest index (HI) and more-efficient interception of solar radiation per unit of applied water by draughted than by well-watered plots in the summer, and despite a lower conversion coefficient, draughted plots showed greater WUE. Based on total water applied and final fresh tuber yields, WUE was, on average, 3·9 and 12·4 kg/m3 in the hot and cool seasons, respectively, values close to the extremes of the range of published values. Low HI in the summer was, to some extent, responsible for this seasonal difference.

Two field experiments were conducted in Egypt in 1985 and 1986 to examine the responses of yield and its components and fibre quality in the Egyptian cotton cultivar Giza 75 to the spray application of 0, 10, 20, 40, 60, 80, and 100 mg of 1,1-dimethyl piperidinium chloride (Pix)/litre at 90 days or at 90 and 110 days after sowing. Number of opened bolls/plant, boll weight, seed and lint index, seed cotton yield/plant, seed cotton and lint yield/ha and yield earliness increased, but lint percentage decreased after Pix application. The number of opened bolls/plant increased after one application, but there was no effect from a further application. There were no effects of concentration or number of applications of Pix on any fibre property.

Determinate forms of field bean (Vicia faba L.), because of their altered growth habit, may differ in phenology from indeterminate cultivars and so their responses to environmental conditions may necessitate different optimum sowing dates. This was studied in autumn-sown field beans at the University of Nottingham at Sutton Bonington by standard growth analysis techniques, final yield components and monitoring of crop growth stages in an indeterminate cultivar, Bourdon, and two determinate populations, 858 and 796 (provided by Plant Breeding International, Cambridge), in three consecutive seasons beginning in 1985/86.

Bourdon yielded significantly more (2·4 t/ha, on average) than the determinate selections as a result of more pod-bearing nodes per stem and seeds per pod and a greater individual seed weight. There was, however, no correlation between seed yield and canopy size, either in total or during pod filling. Determinacy, contrary to expectation, did not increase harvest index. In fact, the reproductive stems of Bourdon had higher harvest indices than those of 858. The yield disadvantage of determinates was therefore exacerbated by the existence of reproductive stems, which, by prolonging the maturation phase, may also detract from a further potential benefit of the determinate habit, namely an increase in yield stability.

There seemed to be no cultivar differences in the temperature requirement for the initiation of developmental processes. An average accumulation of 1239 °C days was required from sowing to flowering. Differences between this and other work in the calculated base temperature for flowering were cautiously explained by the lack of data distinguishing day and night temperature in this experiment and by the use of autumn-sown rather than spring-sown cultivars. It is also suggested that photoperiod may be important in initiating flowering.

Both determinate and indeterminate forms gave the greatest seed yields from the earliest sowing dates.