Cadmium uptake by onions, lettuce and spinach in New Zealand: Implications for management to meet regulatory limits.

Paired soil and plant samples collected from the main commercial growing areas for onions (Allium cepa), lettuce (Lactuca sativa) and spinach (Spinacia olearacea) in New Zealand were used to assess the influence of plant and soil factors on cadmium (Cd) uptake in these crops. Differences in Cd concentration between eight lettuce sub-types were not consistent across sites, nor were differences in Cd concentrations in three crisphead cultivars assessed at two sites. Similarly, differences in Cd concentrations between four onion cultivars were inconsistent across sites. Mean lettuce Cd concentrations in eight lettuce varieties (range 0.005-0.034 mg∙kg-1 (fresh weight, FW) were markedly lower than those in baby leaf and bunching spinach, (range 0.005-0.19 mg∙kg-1 FW). Significant regional variation was observed in Cd concentrations in one onion cultivar (mean range 0.007-0.05 mg∙kg-1 FW). Soil Cd concentration, pH and region were statistically significant predictors of onion Cd concentration, explaining low (38% for soil Cd and pH) to moderate (50% for all three parameters) percentage of the variation. Soil Cd concentration and exchangeable magnesium or total carbon were statistically significant predictors of Cd concentration in baby leaf and bunching spinach, respectively, explaining a moderate percentage (49% and 42%) of the variation in Cd concentration. Increasing pH and soil carbon may assist in minimising Cd uptake in onion and bunching spinach, respectively. The low to moderate proportion of explained variation is partly attributable to the narrow range in some measured soil properties and indicates factors other than those assessed are influencing plant uptake. This highlights a challenge in using these relationships to develop risk-based soil guideline values to support compliance with food standards. Similarly, the inconsistency in Cd concentrations in different cultivars across sites highlights the need for multi-site assessments to confirm the low Cd accumulation status of different cultivars.

Dietary arginine stimulates humoral and cell-mediated immunity in chickens vaccinated and challenged against hydropericardium syndrome virus.

The effects of dietary supplement of arginine on protective humoral and cell-mediated immune responses of broiler chicks vaccinated and challenged against hydropericardium syndrome virus (HPSV) were investigated and compared with those of 2 reference drugs (cyclophosphamide and cyclosporine). Percentage ratios of lymphoid organs (bursa, spleen, and thymus) to BW, postvaccination and challenge serum antibody responses to HPSV, cutaneous basophil hypersensitivity reaction, peripheral lymphoproliferation, postchallenge detection of HPSV in the tissues of infected birds, and ability of chicks to resist virulent HPSV challenge were the parameters utilized to determine the effects of arginine on protective immune responses of chicks. A total of 600 chicks were used in this study. Arginine-supplemented chicks showed significant (P < 0.05) stimulation of lymphoproliferation and cutaneous basophil hypersensitivity reactions compared with untreated control chicks. Similarly, significantly higher body and lymphoid organ weights were (P < 0.05) recorded in arginine-supplemented chicks compared with untreated control chicks. The highest survival rate was recorded in arginine-supplemented HPS-vaccinated chicks compared with immune-suppressed (cyclophosphamide- and cyclosporine-treated and HPS-vaccinated chicks) and untreated unvaccinated control chicks after virulent HPSV challenges. Postchallenge tissue samples from arginine-supplemented and HPS-vaccinated chicks yielded negligible HPSV detections by virus isolation in cell culture or PCR method, or both, compared with untreated control chicks. Thus, it was concluded that dietary supplementation of arginine had beneficial effects on humoral and cell-mediated immune responses of broiler chicks against HPSV.