Silage contribution to aflatoxin B1 contamination of dairy cattle feed.

ALONSO V; GONZALEZ PEREYRA ML; DOGI C; DALCERO AM; ROSA CAR; CHIACCHIERA SM; CAVAGLIERI LR

Aflatoxins book 2

Intech online publishers

Año: 2011; p. 1 - 18

Dairy production systems have traditionally relied on direct utilization of pastures and annual soiling crop. This feeding strategy is complemented by the use of other feeds such as grains, balanced feed, silage, hay and industrial products, the level of use was variable and it defined in any way the degree of intensification of each dairy production systems. Over recent decades, this intensification has been increasing at an accelerated rate, partly because the farms that remain, integrated into general agricultural-livestock mixed models, increasing land for agriculture, as a result of best price-cost and simplicity of production. This change in management practices in dairy cattle breeding, from the extended to semi-intensive or intensive form, has meant a change in the way animals are fed. The change from grazing over large areas of land to cowshed feeding with grain-based concentrates and silage has greatly improved productivity increase on the number of animals per hectare and, in turn, improved performance and milk production per cow due to the nutritional advantages afforded by the new way of eating. The dairy industry has been driven to higher levels of efficiency and competitiveness. This management system makes storing feed necessary as it is used throughout the year whether it is produced in the same establishment or not. This raises the concern to protect these products from damage by insects, pests and fungal contamination in order to maintain an appropriate level of feed security. Storage systems for feed, both silage and whole grains are a man-made ecosystem in which quality and nutritive changes occur because of interactions between physical, chemical and biological factors. The deterioration by fungi and mycotoxin contamination is one of the greatest risks of stored feed. Apart from reducing palatability and feed consumption, fungal growth leads to loss of nutrients and dry matter causing in animal performance (O´Brien et al., 2005). Fodder, cereals and seeds used in feed for dairy cattle are naturally in contact with yeasts and filamentous fungi, the contamination of raw materials occurs frequently in the field, because of  the infection of plant symbiotic fungi as phytopathogens. This contamination can also occur during harvesting, transport and storage of these products and post harvest mishandling can lead to rapid spoilage. In well-preserved forages fungal growth depends on moisture conditions of the plant during harvest. Stored feed, moisture, temperature and oxygen availability are key parameters that determine risk degree of fungal contamination. The critical water activity for safe storage is 0.7 to 0.8 (Magan & Aldred 2007; Scott, 1957). When this level is exceeded, large degrading ability fungi as Eurotium sp., and species of Aspergillus and Penicillium can grow. Increase in respiratory activity, due to the development of these fungi, leads to an increase in the temperature of feed that can lead to the contamination by other fungi especially thermophilic fungi and, therefore, to further deterioration. Silage is one of the main constituents in the diets of dairy cattle and its deterioration and aflatoxin contamination can lead to considerable production losses and a major impact on human health.