When selecting antibiotic feed additives for cattle, there are many factors that can influence the performance of your animals. For example, the concentration of antibiotics in the feed, the nutrient content of the diet, and the health of the cattle may all play a role. In addition, the bacteria that live in the rumen, colon, and cecum can all impact the way that an antibiotic acts.
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Phylum-level distribution of bacteria in rumen, colon, and cecum
The functional composition of the microbial flora in the rumen, colon, and cecum was analyzed in post-weaning Mongolian cattle. This study explored the role of microorganisms in the nutrient digestion of the hindgut of Mongolian cattle.
A total of eight57 bacterial genera were identified. Firmicutes were the most abundant phylum. They accounted for 73.0% of the microbial community. However, a significant decrease in the number of gram-positive families was observed in the GIT of AB steers.
Bacteroidetes were the most prevalent phylum in the rumen. They correlated positively with amino acid and glycan metabolism. Membrane transport and translation pathways were also abundant in the rumen. These are important metabolic pathways involved in regulating physiological activities.
Nonionophore feed grade antimicrobials improve growth rate
Monensin, a bactericidal ionophore, has been used to increase the growth rate of steers. It is an anti-bacterial agent that is metabolized by the liver. In vitro studies have shown that monensin decreases rumen bacterial diversity in vivo.
This study investigated the effect of monensin and tylosin, two feed grade antibiotics, on the microbial composition of the GIT of steers. The results showed that treatment with tylosin and monensin decreased the Firmicutes to Bacteroidetes ratio. However, there was no significant change in the abundance of Erysipelotrichaceae, Lachnospiraceae and Ruminococcus.
This is a small study, but does provide important information on how the use of feed grade antibiotics can affect the microbial composition of the rumen and colon. A shotgun metagenomics sequencing approach was employed to allow higher resolution bacterial community analysis.
Ionophores increase gain of cattle on forage based diets
Ionophores are antibiotic-like compounds used to increase gain of cattle on forage based diets. These compounds can be given as a dry supplement or liquid, and they are absorbed in the small intestine.
There are several different commercial ionophores available to consumers. These include Lasalocid, Latilomycin Propionate, Cattlyst, and Monensin. They can be administered through feed or through mineral mixtures.
Studies have shown that ionophores may improve forage based diets by increasing gains and efficiency, decreasing bloat, and reducing acidosis. In addition, they may reduce the incidence of coccidiosis.
However, the economics of ionophore supplementation depend on the market value of the animal. The adoption of ionophore use is skewed towards stocker production, with less adoption for cow-calf operations.
Influence of antibiotic resistance genes in rumen, colon, and cecum
A study was conducted to evaluate the influence of antibiotic resistance genes on the rumen, colon, and cecum microbiome of cattle fed a grain-based diet with antibiotic feed additives. Species diversity and richness were not found to be significantly affected by feeding these additives.
The relative abundance of detoxification genes was 0.3%. This number was lower than other studies with a dietary treatment of Monensin or Tylosin. Similarly, there was no difference in the presence of AMR genes between control and treated steers. However, the relative abundance of Syntrophomonas decreased in the cecum of AB steers.
Moreover, the abundance of gram-positive Firmicutes and the unclassified members of the Erysipelotrichaceae and Lachnospiraceae family members were reduced in the rumen of AB steers. On the other hand, gram-negative Veillonellaceae increased. These genera are known to produce propionic acid and are associated with the prevention of lactic acid accumulation.
Meta-analysis of the effects of monensin on feed efficiency, body weight gain, and dry matter intake
Monensin is a polyether monocarboxylic acid antibiotic. It is widely used as a routine feed additive in ruminants. It is believed to reduce ammonia accumulation, increase feed efficiency, and reduce methane emission. The effect of monensin on milk production, body weight gain, and dry matter intake in cattle is investigated in this meta-analysis.
This study evaluated the effects of monensin on three important physiologic indicators of beef cows: feed efficiency (FE), body weight gain (BW), and dry matter intake (DMI). The results indicated that monensin increased FE and decreased DMI. It improved ADG, BCS, and FCR.
There was moderate heterogeneity for all 3 outcomes. However, there was low heterogeneity for milk fat and protein content.
Regulations for the use of antibiotics in food-producing animals
In the last decade, countries around the world have introduced restrictions on the use of antibiotics in food-producing animals. This is a response to growing concerns about the potential consequences of increased antimicrobial resistance.
Antibiotics have been used to treat disease in animals for decades. The World Health Organization has called on countries to cut down on unnecessary antibiotic use.
The United States Food and Drug Administration recently released an advisory on the best way to control infectious disease. It recommends limiting the use of medically important antibiotics for growth promotion and clinically diagnosed infectious diseases. However, some critics claim the FDA hasn’t gone far enough.
