Seed exchanges,a key to analyze crop diversity dynamics in farmer-led on-farm conservation

Sustainable management of genetic resources is a crucial issue in the global context of food security. On-farm conservation is now widely acknowledged as a relevant strategy to reach this goal because it maintains evolutionary forces within and between the different components of the agricultural system. Seed exchanges between farmers play a key role in this process but are complicated to study over different agricultural contexts. This review begins by illustrating how interdisciplinary approaches combining ethnobotany and genetics helps provide a detailed analysis of the role of social and genetic dynamic interactions related to seed exchanges in traditional farming systems with farmer-led on-farm conservation. Secondly, the evolution of crop genetic diversity management is described in the context of industrialized farming systems. We follow the evolution of crop biodiversity perception by involved actors using a socio-historical perspective. After the agricultural shift from a traditional to a productivist model, recent social developments such as citizen science and participatory research movements are emerging and are strongly concerned by the question of biodiversity. These emerging trends which recognize and value seed exchanges between farmers show similarities to farmer-to-farmer seed exchanges in traditional farming systems. To what extent are these systems comparable? To fully benefit from studies in both traditional and industrialized contexts, it will be critical to develop an interdisciplinary framework to rigorously compare seed exchange systems and more generally farmer-led on-farm conservation strategies in diverse agricultural systems.     

Effects of high iron and sulfate ion concentrations on dry matter digestion and volatile fatty acid production by ruminal microorganisms.

The inhibitory effects of iron- and sulfate-containing compounds on the in vitro digestion of a balanced forage diet by mixed populations of ruminal microorganisms were examined in batch cultures. Compounds containing ferrous and ferric cations consistently inhibited DM digestion by up to 36% when added Fe concentrations in cultures were between 100 and 1,000 mg/L. Increased sulfate concentrations of up to 200 mg/L or chloride concentrations of up to 635 mg/L were not associated with decreased DM digestion. Ammonium sulfate additions that provided 200 mg/L of added sulfur increased (P less than .05) digestibility by 10%. Sulfate-containing iron salts tended to be less inhibitory than chloride salts and were associated with increased gas production during digestion. Ferric chloride inhibited (P less than .05) microbial activities at lower concentrations than ferrous chloride. Data suggest that excessive iron supplementation or contamination of feeds with iron-containing pollutants may decrease microbial activities in the rumen.     

Sulfur and nitrogen metabolism in the bovine fed different forms of supplemental sulfur

Twelve growing Angus heifers averaging 282 kg in weight were fed a tall fescue hay-based diet in a completely randomized design experiment to determine sulfur (S) and nitrogen (N) metabolism and bioavailability of different forms of supplemental S:elemental S (E), sodium sulfate (SU) and DL-methionine (M). The study included a 72-h adaptation phase that was followed immediately by a 5-d retention phase. Control (C) heifers were fed a ground fescue hay diet twice daily throughout the study. Supplementation with .15% S from E, SU or M to the basal diet began at h 0. Differences in total blood S, plasma S and ruminal NH3 N were dependent on sampling time in the 72-h adaptation phase. Urinary S excretion during 0 to 72 h was greater for S-supplemented calves than for C. Mean molar proportions of acetate, butyrate, isobutyrate and valerate were affected by form of S supplementation. No treatment differences (P greater than .10) were noted in total VFA concentrations. Sulfur supplementation increased daily urinary sulfate (P less than .01), total urinary S (P less than .01) and fecal S (P less than .01) excretion during the retention phase. Methionine and SU heifers had the greatest urinary S losses, and fecal S was highest for E (P less than .01). No differences (P greater than .10) in DM digestion occurred among treatments. N retention (g/d) and N retention as a percentage of intake averaged 5.9, 8.5; 13.2, 18.7; 13.8, 20.5; and 11.3, 19.2, respectively, for C, E, SU and M. Sulfur retention (g/d) was increased (P less than .10) by S supplementation. Sulfur supplementation of a basal fescue hay diet increased S retention transitorily, although much of the added S was lost through excretory routes. Supplementing S as E, SU or M appeared to be equally beneficial, despite differences in route and extent of S excretion among the three S sources.     

IgG1 antibody in milk protects lambs against rotavirus diarrhoea

Newborn gnotobiotic lambs were fed a diet of diluted evaporated milk supplemented either with normal ewes' milk or with milk obtained from ewes injected parenterally during gestation with rotavirus. Lambs fed 150 ml per day of milk collected 5 days after lambing from normal ewes were susceptible to rotavirus infection and diarrhoea, while lambs fed milk from vaccinated ewes collected either 5 or 12 days after lambing were protected. Analysis of the milk by column chromatography showed the anti-rotavirus activity to be in the fractions containing IgG1.     

Anti-fungal and anti-bacterial activities of some pyrrole,furan-and thiophen-sulphonamides and sulphonanilides

The anti-fungal and anti-bacterial activities and phytotoxicity of pyrrole- and 5-nitropyrrole-2-sulphonamides are compared with furan and thiophen analogues. Certain compounds of the group have appreciable anti-bacterial activity consistent with structure-activity investigations of other anti-bacterials derived from these heterocycles.     

An enzyme-linked immunosorbent assay for detection of antibodies to avian adenovirus and avian adenovirus-associated virus in chickens

An enzyme-linked immunosorbent assay system (ELISA) was adapted for the detection of antibodies to avian adenovirus (AV) and avian adenovirus-associated virus (A-AV). Both before and after exposure, sera from chickens undergoing natural and experimental infections were assayed by ELISA, virus neutralization (VN), and immunodiffusion (ID) for antibody to both CELO virus and A-AV. The ELISA system was found to be comparable to VN for determining antibody concentrations to CELO virus and A-AV. In many cases, ELISA was found to be more sensitive than ID.