Erosion/productivity modelling of maize farming in the Philippine uplands part II: Simulation of alternative farming methods

A version of the Agricultural Production Systems Simulator (APSIM) capable of simulating the key agronomic aspects of intercropping maize between legume shrub hedgerows was described and parameterised in the first paper of this series (Nelson et al., this issue). In this paper, APSIM is used to simulate maize yields and soil erosion from traditional open-field farming and hedgerow intercropping in the Philippine uplands. Two variants of open-field farming were simulated using APSIM, continuous and fallow, for comparison with intercropping maize between leguminous shrub hedgerows. Continuous open-field maize farming was predicted to be unsustainable in the long term, while fallow open-field farming was predicted to slow productivity decline by spreading the effect of erosion over a larger cropping area. Hedgerow intercropping was predicted to reduce erosion by maintaining soil surface cover during periods of intense rainfall, contributing to sustainable production of maize in the long term. In the third paper in this series, Nelson et al. (this issue) use cost-benefit analysis to compare the economic viability of hedgerow intercropping relative to traditional open-field farming of maize in relatively inaccessible upland areas. (C) 1998 Elsevier Science Ltd. All rights reserved.

Erosion/productivity modelling of maize farming in the Philippine uplands part III: Economic analysis of alternative farming methods

Two previous papers in this series (Nelson et al., this issue) described the use of the Agricultural Production Systems Simulator (APSIM) to simulate the effect of erosion on maize yields from open-field farming and hedgerow intercropping in the Philippine uplands. In this paper, maize yields simulated with APSIM are used to compare the economic viability of intercropping maize between leguminous shrub hedgerows with that of continuous and fallow open-field farming of maize. The analysis focuses on the economic incentives of upland farmers to adopt hedgerow intercropping, discussing farmers' planning horizons, access to credit and security of land tenure, as well as maize pricing in the Philippines. Insecure land tenure has limited the planning horizons of upland farmers, and high establishment costs reduce the economic viability of hedgerow intercropping relative to continuous and fallow open-field farming in the short term, In the long term, high discount rates and share-tenancy arrangements in which landlords do not contribute to establishment costs reduce the economic viability of hedgerow intercropping relative to fallow open-field farming, (C) 1998 Elsevier Science Ltd. All rights reserved.

Increased ovulation rate in Merino ewes immunized against small synthetic peptide fragments of the inhibin alpha subunit

Four experiments were carried out in Merino ewes during a period of 4 years to determine the long-term effects of immunization against different synthetic peptides mimicking the amine terminal of the or subunit of porcine inhibin. Peptides were conjugated to human serum albumin and 100-200 mu g emulsified in Freund's complete adjuvant for the primary immunization. Usually two booster injections were given at monthly intervals with 50-100 mu g conjugated peptide using either incomplete Freund's adjuvant or Montanide : Marcel. In some experiments a further immunization was carried in the next year. Blood samples were taken 10 days after each immunization, during the luteal phase, for estimation of gonadotrophin concentrations and determination of inhibin antibody titres. One day after blood sampling cloprostenol was used to induce luteolysis and laparoscopy was performed in the subsequent oestrous cycle. Immunization of ewes with synthetic peptides 1-32, 1-26, 7-26 and 8-30 resulted in large increases in the ovulation rate (OR). An approximately two-fold increase in OR was observed following the first booster immunization with these peptides and a three- to five-fold increase after the second booster immunization. Immunization with these large peptides resulted in a sustained increase in OR for a period of at least 1 year after the second booster immunization. Of the shorter peptides, peptides 10-26 and 13-26 gave a reasonable ovulatory response, although it was more difficult to obtain a response with peptides 1-16, 8-22, 13-25, 8-19 and 10-19; peptides 7-13 and 1-6 gave no response (but were examined for one breeding season only). The smaller peptides led to lower inhibin antibody titres that were not necessarily associated with increased follicle-stimulating hormone (FSH) or OR. More intensive blood sampling in one experiment showed that following primary immunization against peptide 1-32 there was a transient increase in plasma FSH which did not lead to an increased OR. Moreover, a prolonged period of raised FSH after the first booster was significantly correlated with increased OR. In these animals antibody titres were only slightly increased after primary immunization, but after the first booster immunization higher titres were observed that were significantly correlated with trough FSH values and the subsequent OR. These results are interpreted as showing that (1) to obtain an increase in OR peptides 1-32, 1-26 and 7-26 are suitable as immunogens; (2) smaller peptides are less reliable, often require multiple injections, and the response may be delayed; and (3) an extended period of raised plasma FSH is needed to give a large ovulatory response.

Prey capture and accommodation in the sandlance, Limnichthyes fasciatus (Creediidae; Teleostei)

The eyes of the sandlance, Limnichthyes fasciatus (Creediidae. Teleostei) move independently and possess a refractive cornea, a convexiclivate fovea and a non-spherical lens giving rise to a wide separation of the nodal point from the axis of rotation of the eye much like that of a chameleon. To investigate this apparent convergence of the visual optics in these phylogenetically disparate species, we examine feeding behaviour and accommodation in the sandlance with special reference to the possibility that sandlances use accommodation as a depth cue to judge strike length. Frame-by-frame analysis of over 2000 strikes show a 100% success rate. Explosive strikes are completed in 50 ms over prey distances of four body lengths. Close-up video confirms that successful strikes can be initiated monocularly (both normally and after monocular occlusion) showing that binocular cues are not necessary to judge the length of a strike. Additional means of judging prey distance may also be derived from parallax information generated by rotation of the eye as suggested for chameleons. Using photorefraction on anaesthetised sandlances, accommodative changes were induced with acetylcholine and found to range between 120 D and 180 D at a speed of 600-720 D s(-1). The large range of accommodation (25% of the total power) is also thought to be mediated by corneal accommodation where the contraction of a unique cornealis muscle acts to change the corneal curvatures.

Four cases of equine polysaccharide storage myopathy in the United Kingdom

This paper describes four cases of equine polysaccharide storage myopathy which were confirmed by histological examination of muscle biopsy specimens. The horses were of mixed breeding, with warmblood and thoroughbred dominating. They all had recurrent episodes of rhabdomyolysis, indicated by clinical signs and increased plasma levels of muscle enzymes. They were managed conservatively and have continued athletic careers despite their disease.