Friday, September 9, 2011
Bt Cotton seed meal in Cattle feed
Gossypol is a yellow compound produced by the Bt cotton plant that confers resistance to pests. To prevent any harmful effects of feeding Bt cotton seed meal to cows, this Gossypol content in cattle feed has to be kept to safe levels. Theoretically it is considered possible to analyse and ensure that cattle feed users are educated about Glossypol content in the cattle feed, to ensure that Bt cotton seed meal will not cause any harm to the cattle. But in practice this has never been possible to implement even in Europe. The result is that Europe has practically stopped using cotton seed meal in the cattle feed. It is therefore a suggestion for Indian cows and Indian cattle feed manufacturing industry to avoid use of any cotton seed meal. For interest of more scientific minded persons, the following is reproduced to explain the position in details. Gossypol is a yellow compound produced by the Bt cotton plant that confers resistance to pests. Gossypol shows moderate acute toxicity in most species with oral LD50s of 2400-3340 mg/kg for rats, 500-950 mg/kg for mice, 350-600 mg/kg for rabbits, 550 mg/kg for pigs and 280-300 mg/kg for guinea pigs. Signs of acute gossypol toxicity are similar in all animals and included spnoea and anorexia. Generally, (–)-gossypol is more biologically active than (+)-gossypol. However,(+)-gossypol is more slowly eliminated. The main target organ of gossypol toxicity following repeated exposure to lower doses in rats and humans is the testis with reduced sperm motility, inhibited spermatogenesis and depressed sperm counts. Suppressed spermatogenesis in humans is partly irreversible, particularly in males with varicocele. Gossypol also affects female reproductive organs and embryo development . Gossypol is not genotoxic and it did not induce tumors in a one year study in rat. No health based guidance value (ADI, TDI) has been established for gossypol. The lowest oral doses inhibiting spermatogenesis in humans and monkeys were 0.1 and 0.35 mg/kg b.w., respectively. Gossypol is less toxic to ruminants, and inhibition of spermatogenesis, embryo development and increased erythrocyte fragility occur at doses of 6-18 mg/kg b.w. per day in cattle and cardiomyopathy in lambs at 2-3 mg/kg b.w. per day. Monogastric animals appear to be more susceptible to gossypol toxicity than ruminants. Current legislation includes maximum limits for free gossypol in both cottonseed meal and complete feeding stuffs. Under normal feeding practices, the concentration in complete feeding stuffs will be less than half the maximum permitted level, even assuming the highest permitted concentrations in cottonseed meal and maximum recommended inclusion rates of the meal in livestock diets. The concentrations of free gossypol that theoretically could be reached according to the current legislation on maximum permitted concentrations in complete feeding stuffs would lead to an intake of gossypol that could result in adverse effects in livestock. The potential exposure to free gossypol, based on the maximum permitted concentration in cottonseed meal and recommended maximum inclusion rates in complete feed, would not be expected to result in adverse effects in ruminants, poultry and fish. However, not all mono gastric livestock animals, e.g. pigs, have been fully investigated for potential reproductive effects occurring at low doses in some species. There is a lack of data on gossypol content (free and bound) in feed materials used for livestock in the EU. However, information provided by the livestock feed industry indicates that amounts of cottonseed meal imported into the EU have declined significantly in recent years, and relatively little is now used as a feeding stuff for livestock in the EU. Industry sources confirm that it is not used as a feed for laying hens or fish. Gossypol is transferred to edible parts, muscle and offal of ruminants and poultry, and is probably transferred to cow’s milk as it is transferred to breast milk in rats. There is very little quantitative information on transfer. At high experimental doses substantial amounts are transferred. No information was identified on the bioavailability of gossypol remaining in food products from animals fed gossypol containing feed. Human exposure to gossypol through the consumption of food products from animals fed gossypol seed derived products is probably low and would not result in adverse effects.