Feed Composition Differences Resulting from Organic and Conventional Farming Practices Affect Physiological Parameters in Wistar Rats—Results from a Factorial, Two-Generation Dietary Intervention Trial

Abstract

Recent human cohort studies reported positive associations between organic food consumption and a lower incidence of obesity, cancer, and several other diseases. However, there are very few animal and human dietary intervention studies that provide supporting evidence or a mechanistic understanding of these associations. Here we report results from a two-generation, dietary intervention study with male Wistar rats to identify the effects of feeds made from organic and conventional crops on growth, hormonal, and immune system parameters that are known to affect the risk of a number of chronic, non-communicable diseases in animals and humans. A 2 × 2 factorial design was used to separate the effects of contrasting crop protection methods (use or non-use of synthetic chemical pesticides) and fertilizers (mineral nitrogen, phosphorus and potassium (NPK) fertilizers vs. manure use) applied in conventional and organic crop production. Conventional, pesticide-based crop protection resulted in significantly lower fiber, polyphenol, flavonoid, and lutein, but higher lipid, aldicarb, and diquat concentrations in animal feeds. Conventional, mineral NPK-based fertilization resulted in significantly lower polyphenol, but higher cadmium and protein concentrations in feeds. Feed composition differences resulting from the use of pesticides and/or mineral NPK-fertilizer had a significant effect on feed intake, weight gain, plasma hormone, and immunoglobulin concentrations, and lymphocyte proliferation in both generations of rats and in the second generation also on the body weight at weaning. Results suggest that relatively small changes in dietary intakes of (a) protein, lipids, and fiber, (b) toxic and/or endocrine-disrupting pesticides and metals, and (c) polyphenols and other antioxidants (resulting from pesticide and/or mineral NPK-fertilizer use) had complex and often interactive effects on endocrine, immune systems and growth parameters in rats. However, the physiological responses to contrasting feed composition/intake profiles differed substantially between the first and second generations of rats. This may indicate epigenetic programming and/or the generation of “adaptive” phenotypes and should be investigated further.

Integrated Soil and Crop Management in Organic Agriculture: A Logical Framework to Ensure Food Quality and Human Health?

“…It is important to note that the concentrations of pesticides in pesticide-treated crops may also be affected by both environmental conditions and agronomic practices other than pesticide use [58,[142][143][144]. For example, wheat produced with conventional, pesticide-based crop protection regimes had significantly higher chlormequat levels in manure-fertilized plots, compared with mineral NPK-fertilized plots in the NFSC trial [58] (Figure 9).…”

“…The higher chlormequat residues in manure-fertilized crops are thought to be due to the 1-2-week earlier wheat grain maturity In contrast, concentrations of the insecticide aldicarb and the herbicide diquat were lower in compound feeds made from manure-fertilized crops, compared with mineral NPK-fertilized cereal, potato, carrot and onion crops, when feeds made from pesticidetreated crops were compared [58,143]. Aldicarb is an insecticide applied as granules to soils for soil-borne pests, and nematode control and was only used in potato crops, whereas Diquat is a semi-selective herbicide that was applied in potato and vegetable crops in the NFSC trials [58,143]. Soil-applied herbicides and insecticides are known to be absorbed by soil organic matter, and aldicarb metabolism in topsoil is thought to be mainly by microbial activity [144,145], which is known to be higher in soils receiving regular organic fertilizer inputs [78,[146][147][148].…”

“…Compound feeds made from manure-fertilized cereal, potato, carrot and onion crops grown in the NFSC trials and used in animal dietary intervention studies (see Section 2.1) therefore contained significantly higher concentrations of chlormequat, than feeds produced with mineral NPK fertilizer [142]. In contrast, concentrations of the insecticide aldicarb and the herbicide diquat were lower in compound feeds made from manure-fertilized crops, compared with mineral NPK-fertilized cereal, potato, carrot and onion crops, when feeds made from pesticidetreated crops were compared [58,143]. Aldicarb is an insecticide applied as granules to soils for soil-borne pests, and nematode control and was only used in potato crops, whereas Diquat is a semi-selective herbicide that was applied in potato and vegetable crops in the NFSC trials [58,143].…”

“…Two of the published dietary intervention studies with rats had a factorial design, and investigated effects of and interactions between contrasting fertilization (manure versus mineral NPK) and crop protection regimes (with and without synthetic chemical pesticides) used in organic and conventional farming on growth, hormone and immune system parameters (Figure 13) [142,143]. and selected hormones and immunological parameters (response variables) in the first (G1) and second (G2) generation of rats, data from [143] Results from both studies suggested that the relatively small changes in dietary intakes of (i) polyphenols and other phytochemicals, (ii) endocrine-disrupting pesticides, (iii) toxic metals (Cd, Pb) and/or (iv) fiber, lipids and protein resulting from pesticide and/or mineral NPK fertilizer use, have complex and often interactive effects on endocrine, immune systems and growth parameters in rats (Figure 13). Moreover, both studies reported that the consumption of organic feed resulted in higher levels of lymphocyte proliferation (a marker for immune system responsiveness) when compared with the consumption of conventional feeds [142,143].…”

“…and selected hormones and immunological parameters (response variables) in the first (G1) and second (G2) generation of rats, data from [143] Results from both studies suggested that the relatively small changes in dietary intakes of (i) polyphenols and other phytochemicals, (ii) endocrine-disrupting pesticides, (iii) toxic metals (Cd, Pb) and/or (iv) fiber, lipids and protein resulting from pesticide and/or mineral NPK fertilizer use, have complex and often interactive effects on endocrine, immune systems and growth parameters in rats (Figure 13). Moreover, both studies reported that the consumption of organic feed resulted in higher levels of lymphocyte proliferation (a marker for immune system responsiveness) when compared with the consumption of conventional feeds [142,143].…”