Feed and Nutrition Featured Articles
Advantages of Organic Acids for Feed and Feed Raw Materials
Prevention of disease transmission and enhancement of growth and feed efficiency are critical factors in modern animal production (Mroz, 2005). When pathogenic bacteria contaminate feed, it becomes a potential route of transmission of disease to animal and human populations, and is consequently of great concern to producers and consumers (Crump et al., 2002; WHO, 2006).
Food-producing animals (e.g. cattle, chickens, pigs, and turkeys) are the main reservoirs for many of these microorganisms, which include non-Typhi serotypes of Salmonella enterica, Campylobacter species, Shiga toxin producing strains of Escherichia coli, and Yersenia enterocolitica (Mead et al., 1999). The microflora found in feed materials comes from a variety of ecological niches e.g. soil and the animals’ gastrointestinal (GI) tract. The GI tract pathogens can be introduced into food chain by animals defecating in the farm environment or by fertilisation of crops with manures (Maciorowski et al., 2007), consequentially making feed a carrier for animal and human pathogens.
Feed materials may be inoculated with microorganisms, mostly bacteria and fungi, at any time during growing, harvesting, processing and storage. Counts of microorganisms vary depending on the function of materials, location of its origin and climatic conditions (D’Mello 2006). It is known that microfloral growth is dependent on moisture, pH value, temperature and composition of feed materials (Maciorowski et al., 2007). For example, the optimal temperature for E. coli O157:H7 is 37°C, with a minimum of 7-8°C and a maximum of 46°C. The optimal pH is between 6 and 7, however it might stand a pH range between 4.4 to 9.0. The E. coli O157:H7 doubles in number approximately every 0.4 h at the optimal temperature and pH value. Some microorganisms including E. coli may adapt to conditions without water and can actively grow in stored feed. Some authors reported that grains and oilseed crops possess a diverse microflora, with populations ranging from 5x103 to 1.6x108 colony-forming units (CFU)/g that are highly resistant to low moisture conditions (Multon, 1988; Richard-Molard, 1988). The orientation values of mesophilic bacteria, including Listeria monocytogenes, Pesudomonas maltophilia, Thiobacillus novellus, Staphylococcus aureus, Streptococcus pyrogenes, Streptococcus pneumoniae, E. coli and Clostridium kluyveri etc. for swine compound feed are shown in Table 1 (VDLUFA, 2007).
