Probiotics to replace antibiotics as cattle growth promoters?

A historical need in the livestock field is to find strategies to keep animals healthy and, at the same time, stimulate rapid and sustained growth so that production costs can be reduced and demand can be met. In this way, starting in the 1950s, when intensive systems for raising meat animals (feedlot) were developed, small doses of antibiotics began to be used as growth promoters. However, its excessive or improper use has contributed to the development of bacteria resistant to antibiotics, which cause infections that are very difficult to treat and endanger human lives, such as Escherichia coli O157:H7, responsible for Hemolytic Uremic Syndrome.

Now, a group of scientists from the Reference Center for Lactobacilli (CERELA), attached to the National Council for Scientific and Technical Research (CONICET), in Argentina, as well as the Catholic University of the Sacred Heart, in Cremona-Piacenza, Italy, have published in the academic journal Scientific Reports the results of a study showing that adding certain probiotics to the diet of cattle is a “promising” way to replace antibiotics as growth promoters.

Probiotics are living organisms – lactic acid bacteria, bifidobacteria, bacilli or yeasts with immunostimulatory capacity – which, administered in adequate amounts, confer a beneficial physiological effect on the health of those who ingest them by improving the balance of the microbiota (previously called intestinal flora) . Unlike antibiotics, which destroy both harmful and beneficial bacteria, probiotics are capable of promoting the growth of beneficial strains or species of bacteria in the gut at the expense of less desirable ones.

“Among the antibiotic replacement strategies in meat animals raised in intensive systems, the use of feed additives that favorably affect animal health, particularly through the modulation of the gastrointestinal microbiota, generated great expectations at the research level. The use of lactic acid bacteria has been and continues to be the object of study of CERELA”, one of the authors of the research, CONICET senior researcher and PhD in Chemistry, Graciela Vignolo, told the CyTA-Leloir Agency.

Vignolo added: “By supplementing cattle diets with these probiotics, we saw increases in productivity through greater bacterial stability of the ruminal environment, essential for the digestion of nutrients; the reduction of pathogenic bacteria in the gastrointestinal tract; stimulation of the immune system; and a higher meat yield, among other benefits.”

Containers with frozen lactobacilli to administer to animals. (Photo: CyTA-Leloir Agency / CONICET / CERELA)

In the European Union, the use of antibiotics to stimulate the growth of cattle has been prohibited since 2006. In Argentina, the recent sanction of the Law for the Prevention and Control of Antimicrobial Resistance points to the “gradual” elimination of the use of antimicrobials as growth promoters in the livestock and poultry industry and, in fact, in 2018 SENASA prohibited the use of the antibiotic monensin for this purpose, allowing only its therapeutic administration. “But due to the absence of substitutes that stimulate weight gain and maintain a good state of health of the animals, its use in the country still persists,” explained Vignolo.

To determine the beneficial effects of probiotic lactic acid bacteria, the group led by Vignolo and Fatima Nader, CONICET Senior Researcher at CERELA, carried out studies with animals in a feedlot in the province of Santiago del Estero: they administered Limosilactobacillus fermentum CRL2085 and Limosilactobacillus mucosae CRL2069 during different periods of bovine development.

The lactic acid bacteria were produced in large quantities in the CERELA pilot plant to be later administered to cattle separated into batches with the same number of animals, and they were added to the feed poured into the trays for each animal group.

Unlike other meat animals (pigs, poultry), in ruminants the focus of action of probiotics is the rumen, a kind of digester that depends on microbial action for the degradation of the components of the diet. In order to evaluate this effect on the bovine gastrointestinal tract, the researchers analyzed the changes produced by the probiotics tested in bovine feces.

Fecal matter was collected from each animal at different time periods for 163 days. The stool samples were then subjected to total DNA extraction and analysis by high-throughput sequencing to identify the bacterial groups present. These were compared to the “core microbiome” of cattle fed without probiotics.

In the animals that received the probiotic bacteria, there was no evidence of effects on the diversity of the intestinal microbiota, although “the analysis made it possible to detect a greater presence of organisms recognized as beneficial for animal health and welfare, such as different genera of lactic acid bacteria, bifidobacteria and fecalibacterium”, highlighted Nader, specialist in microbiology and biotechnology of lactic acid bacteria.

For her part, Cecilia Fontana, a researcher at the National Institute of Agricultural Technology (INTA) in Argentina, assured: “We found a positive effect on the increase in the biometric parameters weight and daily weight gain. In addition, the presence of probiotics in the diet allowed a significant reduction of enteropathogenic E. coli in the feces, which reduces the risk of meat contamination and a negative effect on the health of consumers”,

According to Vignolo, “the supplementation of probiotic lactic acid bacteria in feedlot cattle diets represents an effective tool for the replacement of antibiotics as growth promoters: it improves the metabolic-nutritional state of the animals, increases productive performance with a reduction in stay in the feedlot (less costs) and decreases the emission of methane into the environment and of pathogenic species in the meat and derived products”. (Source: CyTA-Leloir Agency)