Animal Husbandry sector is one of the fastest growing agricultural sectors contributing about 40 percent of the global value of agricultural production. Livestock provides a major source of disposable income for disadvantaged and marginal populations in developing. Intensive production systems are playing an increasingly important role in the livestock sector worldwide, but this increases the need to ensure that animal welfare issues are appropriately considered. There are two major public health issues; first sub-therapeutic use of antibiotics as growth promoters in animal feed, which has evoked widespread concern due to the potential to develop antibiotic resistance in pathogens and second, food borne zoonotic diseases like salmonellosis, campylobacteriosis etc.
To phase out the sub-therapeutic use of antibiotics, modern livestock production systems are looking for good alternatives to antibiotics. In systems where antimicrobial and anticoccidial agents are banned by law or excluded by preference from animal feeds, it is necessary to change the traditional way of formulating feeds with antimicrobial agents like antibiotics. Antibiotic- and anticoccidials-free nutrition programs must ensure minimal undigested material, especially protein. In short, antibiotic-free animal nutrition programs must use additives that control pathogens and specialty ingredients that minimize the chances of pathogen growth.
Antimicrobial resistance
Antibiotics are used for treating disease, preventing or controlling infection, or promoting animal productivity and growth. When used for growth promotion, antibiotics are administered to healthy animals to make them grow faster or utilize their feed more efficiently. However, rampant use of antibiotics at sub-therapeutic levels leads to antimicrobial resistance of potential pathogens which is a global threat. Antimicrobial resistance refers to micro-organisms bacteria, fungi, viruses, and parasites that have acquired resistance to antimicrobial substances like antibiotics and coccidiostats.
Adoptive measures for antibiotic-free farming
Basic husbandry practices are key to successful antibiotic-free poultry production system, some of the corrective measures for antibiotic-free farming includes:
Farm condition for receiving chicks: First and most important thing is litter quality; it should be treated with disinfectant, should be dry and less dusty. Litter quality plays an important role in coccidiosis control. Consider closing up the housing to induce heating and removal of poultry litter. Resting period of at least 15 days before the arrival of next lot is necessary.
Healthy birds: Pay close attention to the birds in the flocks. Look, listen, smell and touch to evaluate a flock’s condition. Reducing stocking density can be beneficial to avoid overcrowding and optimum ventilation to each bird. Basic husbandry is crucial.
Reduce stress on chicks: Avoid dehydration, chilling and exposure to pathogens that can occur at the hatchery or during chick transport. Reduce the handling stress on chicks; minimize stress involved with chick holding and transport, placement. Proper sanitation is also critical.
Breeder management and sanitation of fertile eggs are essential: Each breeder hen should be vaccinated so that the chicks have the required immunity. Hatching eggs should be sanitized, and clean, uncontaminated eggs should be sent to the hatchery. Proper precautions should be taken to avoid exposure of fertile eggs to microbial contaminations.
Feed processing and formulation: All the possible contaminants like poor quality raw material, fungal infestation due to storage for a longer period etc should be avoided at a feed mill. It is imperative that feed inventory and feed delivery are closely managed. The larger particle size of feed and good pellet quality would benefit gut health and flock performance. Use of alternate feed additives like enzymes, prebiotics, probiotics, organic acids etc instead of antibiotics is a good option.
Preventive measures: Vaccination of breeder hens is essential for overall health of the flock. Coccidiosis control and gut health are of paramount importance. Flocks that need antibiotic treatment should be treated on time and isolated from rest of the flock.
Following are some of the alternatives to antibiotics:
Probiotics
Probiotics are becoming increasingly popular as one of the alternatives to Antibiotic Growth Promoters (AGP). The most important objectives for using probiotics in animal feed are to maintain the GIT microbial balance, improve performance (productivity and growth) of animals, and prevent enteric pathogens. Administration of probiotic strains separately and in combination significantly improves the feed intake, feed conversion efficiency, daily weight gain and total body weight in chicken, pig, sheep, goat, and cattle.
Organic acids
Organic acids are widely accepted as a healthy alternative to reduce the pathogenic load of feed. Free, coated, straight or salts, these compounds have been shown to possess the strongest antibacterial activity. It includes a wide range of products that act at different parts of the gut depending on its pKa chemical trait and local pH at a gut level.
Phytobiotics and Phytogenics:
Some research proves that a combination of phytogenic compounds and organic acids is the best possible combination where phytogenics increase the penetration level of organic acids that disrupt pathogen internal functions.
Enzymes:
Enzymes are well-known additives in poultry nutrition. Use of fiber/non-starch polysaccharides (NSP) digesting enzymes is increasing and is now considered as one of the best alternates to antibiotics growth promoters. Enzymes help to improve feed digestion by releasing prebiotics compounds thereby reducing substrate availability to pathogenic growth.
Yeast:
Due to a ban on antimicrobial agents as growth promoters, application of yeast derivative has gained popularity as a potential alternative. Research has shown that yeast-derived products can be used to control the composition of the microbial population in the gastrointestinal tract, prevent colonization with pathogens. Yeast is being used as antimicrobial compound because of its antagonistic activities toward undesirable bacteria, and fungi.
Antimicrobial peptides:
Antimicrobial peptides derived from beneficial bacteria are a promising alternative for growth promotion that may aid in disease prevention and possibly treatment. Antimicrobial peptides are short molecules with antibacterial properties that are toxic to certain bacteria. In many cases, these peptides are generated by microorganisms. In vitro studies provide strong circumstantial evidence that the use of antimicrobial peptides in broiler chickens, as well as pigs, improves intestinal health and suppresses harmful bacteria by favoring the growth of beneficial microorganisms. Bacteriocins like nicin, pediocin are some of the proven antimicrobial peptides used as antibacterial peptides.
Zinc, copper and other heavy metals:
Zinc, copper and other heavy metals are naturally occurring necessary trace elements in the diet but it may be added to the diet in higher concentrations for growth promotion, and occasionally as therapy for the enteric disease. Experimental studies have demonstrated that in chickens, daily gains were significantly improved when broiler feed was supplemented with a combination of inorganic minerals including copper, iron, manganese, and zinc; these inorganic supplements produced a statistically significant increase in broilers’ weight gain. A variety of other substances have been proposed as growth promoters, including clay minerals (e.g., bentonites, zeolites).
Conclusions:
Antimicrobial resistance has created awareness among consumers for antibiotic and residue free animal products. Use of Antibiotic Growth Promoters (AGPs) has been banned in Europe and USA, India is also in consideration for enforcement of a ban on the sub-therapeutic use of antibiotics in farm animals. Strict hygienic conditions at a farm and healthy animals can reduce the use of antimicrobials at farm levels. Today, alternative products are primarily used for growth promotion and infection prevention, with fewer options available for treatment. However, the efficacy of alternative products tends to be variable across individual livestock operations and with the disease status of herds and is often accepted by external factors such as weather or feed composition.
References are available on request.
by Dr. Dinesh Bhosale, AB VISTA
