 |
    |
|
|
by Kathryn Cooke
The increasing public concern over the production of food from animals has led to worries about the routine use of antibiotics in animal production. It is now feared that antibiotic residues could get into food for human consumption. This in turn has led to worry about resistance of many human pathogenic bacteria to antibiotics. Antibiotics have been used as production enhancers and as a treatment for illness in animals for
a number of years. The use of antibiotics as promoters of animal performance in the EU will be banned by January 2006 (Øverland et al., 2003) in an effort to save the few available antibiotics for human use. In light of this, animal producers perceive the need to find alternatives in order to maintain the same efficiency of production after the ban has been implemented.
There are a number of substances that can offer some of the benefits that antibiotics do, including organic acids, probiotics, prebiotics, herbs and other plant extracts, natural oils, volatile fatty acids and organic acids (Gadd, 1999; Øverland et al., 2003; International, 1999; Geboes, 1999; Adams, 1999; van Kol, 1999). Whilst these substances may have some beneficial effect on animal production, their mechanisms of action vary (Gadd, 1999).
Antibiotics work by altering the population of bacteria present within the gastrointestinal tracts of cattle, sheep, pigs and poultry (McDonald et al., 2002). The modification of the bacterial population in the rumen, can for example, cause a reduction in the amount of methane produced, as well as reduce the deamination of amino acids from feed protein. (Lopez et al., 1995). Thus, antibiotic inhibition of this loss allows the animal to utilise feed to a greater extent than would normally be found, leading to an increased level of performance and a reduced level of pollution.
It is thought by many that acid supplementation of feed will be of greatest benefit to the animal when antibiotics are no longer available (Geboes, 1999; Adams, 1999; van Kol, 1999; Øverland et al.,.2003). Trials using acid supplementation have found that not only does it lead to increased growth rates (Geboes, 1999; International, 1999; van Kol, 1999; Blanchard et al., 201), but it has also been found to increase litter size and survival rates in pigs (Adams, 1999). Adams (1999) found that piglets from sows administered an acidifier had superior performance when compared to those from sows who were not given an cidifier.
Similar effects to feeding antibiotics have been found when feeding organic acids (Geboes, 1999). Both lactic acid and formic acid supplementation have shown improvements in feed conversion rates and thus live weight gains (van Kol, 1999; Geboes, 1999). Lactic acid based mixtures have also been shown to cause a significant decrease in the scouring of pigs (Geboes, 1999). Not all trials have found such positive results with the use of organic acids, however; Thacker et al., (1992) found no improvement in growth rate, feed intake, carcass traits or feed efficiency when barley fed pigs were supplemented with propionic or fumaric acids.
Organic acids are thought to work in much the same way as antibiotics, by essentially manipulating the microbial population (Lopez et al., 1995). In order to decrease methane production, other metabolic pathways are encouraged to compete for hydrogen uptake (Lopez et al., 1995).
Probiotics are also considered to have advantageous effects on animal performance (van Kol, 1999; Gadd, 1999; Theodorou et al., 1990). Whilst Theodorou et al., (1990) found a significant increase in animal liveweight during supplementation with a fungal probiotic in weaned calves, and thus an increase in intake, it was found that feed conversion was not altered. Probiotics are live cultures that stimulate bacterial activity in the gastrointestinal tract (McDonald, 2002; van Kol, 1999). Probiotics decrease the chance of pathogenic bacteria inhabiting the gastrointestinal tract, thus allowing greater utilization of feed (van Kol, 1999). A problem with the use of probiotics is their instability in heat, which would make it difficult to produce stable products.
Recent trials supplementing ruminant diets with essential oils have shown to have some advantageous effects. Greathead et al., (2000) found a significant increase in daily live weight gain and dry matter intake, and a decrease in food conversion ratio in calves supplemented with a formula of essential oils. Essential oils change rumen fermentation by altering the populations of microbial species in the rumen (McIntosh et al., 2003). The oils effect the deamination of amino acids enabling more dietary protein to become available to
the animal (McIntosh et al., 2003).
Alternatives to antibiotics are required if the efficiency of animal production is to be maintained at present levels. Whilst all the substances discussed above have potential uses as alternatives to antibiotics, further research needs to be undertaken to find substances, or combinations of substances, that will help to improve livestock performance.
ADAMS, CA., (1999) Continuous improvement in performance International Pig Topics 14(5) 25
Alternative Agricultural News (2001) 19(11) Published by Henry A Wallace Centre for Agricultural & Environmental Policy
APGAR, GA., KORNEGAY, ET., LINDEMANN, MD. & WOOD, CM., (1993) The effect of feeding various levels of bifidobacterium globosum A on the performance, gastrointestinal measurements and immunity of weanling pigs and on the performance and carcass measurements of growing-finishing pigs. Journal of Animal Science 71(8) 2173-2179
BLANCHARD, PJ., COONAN, C., GUY, JH. & FEUERSTEIN, D., (2001) Influence of Naptuphos® phytase and organic acids on the performance of growing/finishing pigs. Proceedings of the British Society of Animal Science 2001. 143
CHAPPLE, DG., GRUNDY, HF., WHEELER, KPA. & MARSH, SP., (1998) The effect of feeding dried yeast culture on the performance of beef cattle finishing on grass silage based ration. Proceedings of the British Society of Animal Science 1998. 74
DIVA, A., CASADEI, G. & BIAGI, G., (2002) An organic acid blend can modulate swine intestinal fermentation and reduce microbial proteolysis. Canadian Journal of Animal Science 82(4) 527-532
GADD, J (1999) Antibiotic Alternatives: `Sorting out the men from the boys!' Pig Farming 47(6) 9-10
GEBOES, F., (1999) Acid-An Antibiotic Alternative? International Pig Topics 14(5) 23-24
GREATHEAD, HMR., FORBES, JM., BEAUMONT, D. & KAMEL, C., (2000) The effect of a formulation of natural essential oils used as an additive with milk replacer and a compound feed on the feed efficiency of calves. Proceedings of the British Society of Animal Science 2000. 68
INTERNATIONAL, (1999) A new era in performance. International Pig Topics 14(5) 19
JENNY, BF., VANDIJK, HJ. & COLLINS, JA., (1991) Performance and fecal flora of calves fed a Bacillus subitillis concentrate. Journal of Dairy Science 74(6) 1968-1973
LÓPEZ, S., VALDéS, C., NEWBOLD, CJ. & WALLACE, RJ., (1995) Decreased methane production and altered fermentation in response to the addition of fumaric acid to the rumen stimulation technique (rusitec). British Society of animal production. Winter meeting 1995. Paper 109 McDonald, Edwards, Greenhalgh & Morgan (2002) Animal Nutrition. 6th edition, Longman publishing. 172-173
MCINTOSH, FM., WILLIAMS, P., LOSA, R., WALLACE, RJ., BEAVER, DA. & NEWBOLD, CJ., (2003) Effects of essential oils on ruminal microrganisms and their protein metabolism. Applied and Environmental
Microbiology 69(8) 5011-5014
?ERLAND, M., KJELDSEN, KC. & GRANLI, T., (2003) Antibiotic properties of dietary potassium diformate in pigs. Feed Composer 23(10) 17-20
THACKER, PA., CAMPBELL, GL. & GROOTWASSINK, J., (1992) The effect of organic acids and enzyme supplementation on the performance of pigs fed barley-based diets. Canadian Journal of Animal Science 72(2) 395-402
THEODOROU, MIC., BEEVER, DE., HAINES, MJ. & BROOKES, A., (1990) The effect of a fungal probiotic on intake and performance of early weaned calves. Programme and Summaries, British Society of Animal Production, Winter Meeting 1990. Paper 111
VAN KOL, EMR., (1999) Alternatives to growth promoters International Pig Topics 14(5) 26-27