A pre-synchronization program at early postpartum might increase the chances of Bos indicus cows cycling prior to 50 days regardless of the length of calf separation

The aim of this study was to establish if pre-synchronization would enhance the number of animals cycling prior to conventional breeding at 45 days irrespective of the length of calf separation. Multiparous Bos indicus cows were allotted in four groups (n = 10). Control group (C) dams remained with their calves; groups G24, G48 and G72, which were partially weaned for 24, 48 and 72 h, respectively, were estrus synchronized using a controlled internal drug. These procedures were performed at 25 days and again at 45 days postpartum. The number of follicles, presence of a corpus luteum and back fat thickness (BFT) were determined by ultrasound. The proportion of cows with estrus and ovulation at day 25 postpartum was statistically different between the control and treated groups, with the values being 20, 60, 50 and 70 for the control, G24, G48 and G72 groups respectively (P < 0.05). At days 45 postpartum, the proportion of cows with estrus and ovulation was different in group G48 compared with the other groups (P <0.05). The average BFT and body condition score for the four experimental groups in the two periods were similar (P >0.05). Animals with a higher proportion of follicles from 17 to 21 mm, BFT values above 3.5 mm and a regular body condition were significantly different regardless of whether the dams remained with their calves or were separated, regardless of the length of this event. It can be concluded that (1) a pre-synchronization program at day 25 could trigger the onset of ovarian activity and facilitate a breeding program at day 50 and (2) temporary weaning enhances the effect of a pre-synchronization program.     

Enigmatic biodiversity correlations: ant diversity responds to diverse resources

A pattern noted in ecology is that diversity at one level begets diversity at other levels. In the case of consumers competing for similar resources, the diversity of those resources is thought to provide some degree of niche diversification in which a diverse set of consumer species can coexist. If, however, the diverse resources are not sufficiently distinct from one another, from the standpoint of the consumer species, such niche diversification will not exist. We experimentally show that a diverse array of twigs attracted 80% more species of twig-nesting ants than a monospecific collection of twigs. The specific tree species from which the twigs were derived did not explain the pattern. It appears that diversity per se at one level (twigs) creates conditions that promote diversity at another level (nesting ants).     

Cuba and the dilemma of modern agriculture

Having lost 73% of its purchasing power and 42% of it gross national product since the fall of the Soviet Union, Cuba faces a crisis with the modern agricultural system it had developed over the past 30 years. The response has been to put an alternative model into practice. The successes and problems associated with this model are discussed.     

A keystone mutualism drives pattern in a power function

Data that can be described by a power function are ubiquitous in nature. Although there is consensus that such data frequently emerge generally from nonlinear complex systems, a variety of specific mechanisms may be responsible for creating the pattern in particular cases. Here, we report on the distribution of a scale insect (Coccus viridis) that is a common agricultural pest. Its distribution in an organic coffee farm in southern Mexico generally follows a power function, but there are subtle deviations from that function. We offer a biological explanation for both adherence to the power functions and associated deviations, along with supporting evidence.     

Enhanced resistance to bacterial infection byErwinia carotovora subsp.atroseptica in transgenic potato plants expressing the attacin or the cecropin SB-37 genes

Blackleg and soft rot diseases, caused by the bacteriumErwinia carotovora, are among the diseases that cause important losses in culture and storage of potato. In this paper, we introduced bacterial resistance into potato, via genes encoding for proteins with antibacterial activity. For this purpose, potato clones were transformed either with the gene encoding the acidic attacin protein fromHyalophora cecropia, or with the gene encoding the cecropin analog peptide SB37. These clones were evaluated for soft rot and blackleg resistance, after inoculation with the bacterial strainErwinia carotovora subsp.atroseptica T7. Results reported in this paper indicate that a considerable percentage of the potato clones (15–22%) showed increased resistance to bacterial infection, revealed by reduced severity of blackleg or soft rot symptoms. Expression of the transgenes was demonstrated in some of the clones by Northern blot analysis. This is the first report indicating that expression of the gene encoding for an attacin protein and for the cecropin SB-37 peptide in transgenic potato confers increased resistance to bacterial infection.     

Impact of bark and foliage harvesting on fruit production of the multipurpose tree <Emphasis Type="Italic">Afzelia africana</Emphasis> in Burkina Faso (West Africa)

In sub-Saharan Africa, extraction for daily livelihood needs often results in uncontrolled exploitation of bark and leaves of valuable medicinal and fodder trees. However, overharvesting of bark and foliage can reduce fruit production and threaten reproduction. This study evaluates the impact of combined bark and foliage harvesting on the performance of fruit production of Afzelia africana in Burkina Faso. We compared fruit and seed production at different harvesting intensities. Data on fruit yields were collected by stratified random sampling of 91 trees with no, low, severe, and very severe harvesting intensities. The fruit production varied with harvesting intensity, tree size and number of branches. Fruit and seed quantity and quality decreased with increasing harvesting intensity. However, no significant difference was detected between trees without and trees under low harvesting. Trees of all size classes under very severe harvesting intensity had no fruits. Under low harvesting impact, large trees had twice as many fruits as the control, whereas fruits were reduced by half to 95 % for the small trees. High harvesting intensity is an unsustainable practice that should be completely prohibited in order to ensure longterm persistence of Afzelia africana. Low harvesting intensity should be allowed, but only on large reproductive individuals.     

Traditional knowledge and pest management in the Guatemalan highlands

Adoption of integrated pest management(IPM) practices in the Guatemalan highlands has beenlimited by the failure of researchers andextensionists to promote genuine farmer participationin their efforts. Some attempts have been made toredress this failure in the diffusion-adoptionprocess, but farmers are still largely excluded fromthe research process. Understanding farmers'agricultural knowledge must be an early step toward amore participatory research process. With this inmind, we conducted a semi-structured survey of 75Cakchiquel Maya farmers in Patzún, Guatemala, tobegin documenting their pest control practices. Theirresponses revealed that their understanding ofbiological and curative pest control is limited.However, their broad knowledge of cultural preventivepest control practices could explain why they hadfaced few pest problems in their traditionalmilpa (intercrop of corn, beans, and other edibleplants). The majority of these preventive practicesare probably efficient and environmentallyinnocuous.     

Shade over coffee: its effects on berry borer, leaf rust and spontaneous herbs in Chiapas, Mexico

The objective of this research was to determine the relationships between different ecological features of shade and the incidence of coffee berry borer, coffee leaf rust and spontaneous herbs in rustic coffee plantations in Chiapas, Mexico. Thirty-six 10 m by 10 m plots were established within coffee plantations. The following variables were measured or estimated: number of vegetation strata, percent canopy cover, direct, diffuse and total sunlight below the canopy, plant species richness and diversity, shade tree/shrub density, altitude, aspect, basal area, yields, percentage of coffee berry borer (Hypothenemus hampei Ferr), percentage of coffee leaf rust (Hemileia vastatrix Berk & Br.),percentage of spontaneous herb cover and the presence of paths and runoffs.Results showed a complex agroforestry system, composed of five strata. Coffee berry borer and coffee leaf rust incidence averages were 1.5% and 10.1%,respectively. Average spontaneous herb cover was 34.1%. Coffee leaf rust percentage correlated positively with the coffee berry borer. Number of strata of shade vegetation correlated negatively with leaf rust, while the presence of paths correlated positively with the leaf rust. Species richness and diversity correlated negatively to broad-leaf-herb cover and the presence of runoffs correlated positively to this last variable. Shade tree density (> 10cm d.b.h.) correlated negatively to linear-leaf-herb cover. Percentage of shade cover, light, coffee density, aspect, stand age, basal area and yields were not correlated to pest, disease and weeds. Results support the ecological theory that postulates that diversity and structural complexity in mixed plant systems maintain a healthy system.This revised version was published online in November 2005 with corrections to the Cover Date.     

Ants (Azteca sp.) as potential biological control agents in shade coffee production in Chiapas, Mexico

The role of Azteca sp. ants as potential biological control agents was studied in an organic coffee farm in Chiapas, Mexico. Individual larvae of Pieris rapae were placed on trees with artificially enhanced ant activity and both time to disappearance of the larvae and ant activity were recorded. There was a general negative relationship between time to disappearance and ant activity. A census of spiders was made of coffee bushes with and without foraging Azteca, encountering a negative relationship between ants and spiders. These results indicate that Azteca ants have potential as pests through their positive effect on scale insects, but also have potential as biological control agents, through their negative effect on potential herbivores. Furthermore, the correlation between ant and spider densities suggests a complicated relationship between these two predatory organisms, implying a more complicated food web structure than simply ants, homoptera and other herbivores.This revised version was published online in November 2005 with corrections to the Cover Date.