Young Lean And Obese Mice given diets containing, respectively, 5% reducing to 3% and 5% rising to 7% of typical alkaloid-containing ergot (Claviceps purpurea) showed inappetence, failed to grow during the period of 19 days and some individuals died. In contrast, ergot of a strain which cannot biosynthesize ergoline alkaloids was generally well accepted in dietary proportions, rising stepwise from 5 to 12% over the same period; growth rates of animals on control and alkaloid-free ergot diets did not differ significantly. The findings provide a context in which to discuss differentiation of ergoline alkaloids from the inappetence which is a prominent feature of ergot poisoning.

Over five growing seasons (1976–80) experiments were carried out using at least three contrasting sites per season to study the relationship between growing conditions and storage losses in Pentland Crown potatoes. Crops were harvested by hand and storage was carried out in a single environment over a period of 6–7 months without sprout suppressants. The range in growing conditions was great and reflected in the pattern of leaf growth and range in yields of the stored crops (30–90 t/ha). Crops from Tenby (S. W. Wales) produced the most consistent and frequently the highest yields and usually lost the least weight during storage. Although the range in total weight loss over all experiments was large from 5·4 to 16·3%, treatment effects were much smaller than in field growth and yield. Delaying the date of harvest usually increased weight loss and tubers harvested in early August stored at least as well as late-harvested tubers. Tubers harvested without prior defoliation stored as well as tubers harvested on the same day from crops defoliated at least 2 weeks previously. Lengthening the interval from defoliation to harvest usually increased weight loss in storage. Although the tubers were hand harvested effects on saleability were found at the end of storage and there was no evidence that earlier harvesting, which may involve some loss of field yield, would result in any loss of saleable yield out of store.

The results provided no evidence to support the widely-held view that the suitability of a tuber for harvesting improves during maturation associated with natural or imposed crop senescence. It is therefore suggested that the use of the term maturity be avoided as it is wholly unhelpful in studies of the relationship between field growth and storage losses in potatoes.

The interaction of water stress and time from sowing to floral initiation was investigated in the field with pearl millet hybrid BJ 104. Extended daylength was used to delay panicle initiation (PI) and flowering (FL) of crops exposed to single periods of mid-season drought. Growth, yield and yield components were related to the number of days for PI and FL in both irrigated and water-stressed treatments. Delay in PI resulted in more leaves and tillers per plant, and greater leaf area, height and total dry matter. Grain yield, however, was not affected resulting in lower ‘harvest index’. There was, however, an increase in the grain yield of main shoots which was offset by a proportional decrease in the grain yield of tillers.

Water stress effects were dependent on the physiological stage of the crop at which stress occurred, as a result of the photoperiod treatments. Water stress prior to panicle initiation did not affect the grain yield of the main shoot but increased tiller grain yield, resulting in a higher total (crop) grain yield. Water stress during panicle development reduced the grain yield on the main shoot but this loss was compensated by the grain from the increased number of tiller panicles which reached flowering. Water stress during flowering and grain filling reduced grain yields of both main shoot and tillers, making this the most sensitive stage. Photoperiodic control of floral initiation can provide an escape mechanism to avoid the coincidence of mid-season water stress with sensitive periods of growth.

The number of kernels per m2 (K) in well managed and watered wheat crops was studied using results of experiments in Mexico and Australia in which short spring wheat cultivars were subjected to independent variation in radiation, largely via artificial shading, and in temperature. Also crops subjected to differences in weather (year), sowing date and location within Mexico, revealed responses to the natural and simultaneous variation which occurs in radiation and temperature. Responses in K were interpreted in terms of spike dry weight at anthesis (g/m2) and number of kernels per unit of spike weight.

K was linearly and most closely related to incident solar radiation in the 30 days or so preceding anthesis, herein termed the spike growth period; for the cultivar Yecora 70 with full ground cover the slope was 19 kernels/MJ. This response seemed largely due to a linear response of crop growth rate to intercepted solar radiation. The proportion of dry weight increase partitioned to the spike increased somewhat with reduced radiation. Also increasing temperature in the range 14–22 °C during this period reduced K (slope approximately 4% per CC at 15 °C). The cause appeared to be lower spike dry weight due to accelerated development. The number of kernels per unit spike weight at anthesis was little affected by radiation or temperature, and averaged 78±2/g for the cultivar Yecora 70.

With natural variation in radiation and temperature, K was closely and linearly correlated with the ratio of mean daily incident or intercepted radiation to mean temperature above 4·5 °C in the 30 days preceding anthesis. As this ratio, termed the photothermal quotient, increased from 0·5 to 2·0 MJ/m2/day/degree, K increased from 70 to 196 × 102/m2. These responses of K to weather, sowing date and location were closely associated with variation in spike dry weight.

It was concluded that the ratio of solar radiation to temperature could be very useful for estimating K in wheat crop models. Also the analysis of K determination in terms of spike dry weight appeared promising, and suggests that wheat physiologists should place greater emphasis on the growth period immediately before anthesis.

Eighteen growing cattle with a mean live weight of 180 kg were used to study the influence of restricted water on feed intake, nutrient utilization and nitrogen metabolism in Zebu cattle in the Sudano–Sahelian ecological zone of Nigeria.

Feed intake and water consumption were negatively correlated (r = 0·63). As the amount of water intake was reduced from 15·8 to 11·91/day, the mean feed intake increased from 5·6 to 6·8 kg D.M./day; water to feed ratios decreased from 2·83 to 1·75 and average daily live-weight gain as well as apparent feed utilization efficiency improved significantly from free-choice water to 50% of free-choice water treatments respectively.

Apparent digestibility coefficients of almost all the nutrients from the 75 and 50% of free-choice water treatments indicated progressively higher (though not significant) values than those of the free-choice water treatment. Nitrogen metabolism did not indicate any difference in the nitrogen intake in any of the three treatments; however, nitrogen balance and nitrogen retained as a percentage of nitrogen intake were significantly (P < 0·05) higher on the 50% of free-choice water treatment.

The survival ability of these Zebu breeds of cattle under water stress during the acute water scarcity of the protracted dry period of the Sudan–Sahelian zone of Nigeria could probably be attributed to increased recycling of nitrogen as well as a reduction in nitrogen loss during the period.

Oestroua activity of three flocks of Ossimi (O) and Rahmani (R) subtropical fattailed and imported Finn (F) ewes was followed over a calendar year under the prevailing subtropical conditions in Egypt.

Rahmani had quite consistent oestrous activity throughout the year, with a slight drop in March and June, and may be regarded as a non-seasonal breed. Oestrous activity of the O ewes was lower than the R at different times of the year. They showed high individual variation. Most of the O ewes had an anoestroua period during July–September but had regular oestrous activity during their breeding season.

Overall number of oestruses per ewe per year was 15·9, 13·0 and 10·3 for R, O and F, respectively. Normal cycle length tended to be longer, though not significantly so, in both R and O subtropical breeds than the F (17·8 and 17·6 v. 17·1 days). Heat duration was significantly longer in F (47·0 h) than in both local breeds (37·7 and 37·5 h for R and O, respectively).

The response of cotton (Gossypium hirsutum L.) to chilling temperatures has been documented mainly for germinating seeds and young seedlings (Christiansen, 1963; Christiansen & St John, 1981; Guinn, 1971; Sellschop & Salmon, 1928). Ratoon (known also as stub or biennial) cotton offers an opportunity to study the chilling injury of mature plants under field conditions. Observations showed that ratooning plants suffer stand loss during the winter. However, the surviving plants recover and start growing vigorously when temperatures rise, early in the following spring (Ellern, 1966; Evenson, 1970; McClintic, 1981).