Ionophores & B-agonist Flashcards
1
Q
Why were ionophores originally created?
A
- To enhance growth and feed conversion
- Monensin and Iasalocid have secondary label as a coccidiostat
- Increase milk production efficiency
2
Q
What are the ionophores available today
A
- Monensin (RumensinTM) - most common
- Narasin
- Salinomycin
- Lasalocid
- Laidlomycin proprionate
- Semduramicin
- Maduramicin
3
Q
What is the dosage for monensin?
A
- Dose: 0.14 - 0.42 mg/lb BW
- up to 480 mg/hd/day beef
- up to 660 mg/hd/day dairy
- Monensin 90 = 90.7 gm/lb
4
Q
What can Monensin be fed with?
A
- decoquinate
- Tyolsin
- MGA
- ractopamine
- zilpaterol
- tilmicosin
5
Q
What is the MOA of ionophores?
A
- “ion Mover”
- assists in membrane exchange of sodium, calcium, hydrogen, and other ions
- Shifts microbial fermentation to produce mor propionic acid (rather than acetic and butyric)
- more efficient energy production ⇢ increase rate of gain / feed efficiency
- Interferes with transmembrane ion balance in muscle
- Intracellular calcium build-up ⇢ decrease in ATP production ⇢ apoptosis
- Myocardial degeneration and necrosis
6
Q
What are the microbial shift effects of Ionophores?
A
- Propionate synthesized at the expense of acetate and butyrate
- Reduced levels of ketone bodies in early lactation cows
- reduced ketosis
- Sparing effect on AA normally used for gluconeogenesis
- Protein-sparing effects in the rumen by decreasing rumen proteolysis and AA deamination
- Increased ruminal escape of dietary protein
- Decrease rumen ammonia production
- Milk fat depression with little effect on lactose or protein content
7
Q
What are the kinetics of Ionophores?
A
- Rapidly absorbed, widely distributed
- Metabolized in liver - CYP450
- Parent compound and metabolites excreted in bile
8
Q
What species is most and least affected by monensin?
A
- Horses (LD50 2-3 mg/kg)
- Trout (>1000ppm)
9
Q
What are the risks of ionophores?
A
- OD
- cattle 10x dose
- Unintended species
- Repeat exposure
- cattle: LD50 26.4 mg/kg ⇢ 7mg/kg
- Synergisms - macrolide antibiotics
10
Q
What increases and animal’s sensitivity to ionophores?
A
- Repeat exposure
- Low quality diet
- Poor body condition
- compromised metabolism
- Synergism - macrolide antibiotics
11
Q
What is the clinical picture associated with ionophore toxicosis?
A
- Initial 24-48 hours:
- Off feed and diarrhea
- Depression, colic, ataxia, weakness, knuckling, recumbency
- Sudden death especially with stress, forced exercise or elevated ambient temperatures
- Progressive disease as muscle lesions worsen
- Signs of congestive heart failure
- weakness, collapse, recumbency, dyspnea, death
- Signs of congestive heart failure
12
Q
What is the clinical pathology associated with ionophore toxicosis?
A
- Clinical Pathology:
- Elevations in:
- CPK
- ALP
- LDH
- AST
- BUN
- bilirubin
- hematocrit
- Cardiac troponins can be used for a few days post-exposure to evaluate heart damage
- Elevations in:
13
Q
How is Ionophore toxicosis diagnosed?
A
- Chem 10
- Gross lesions
- Histopathology
14
Q
What are the gross lesions associated with ionophore toxicosis?
A
- Pale, streaky heart
- epicardial & endocardial hemorrhage
- Fluid accumulation in body cavities
- Pulmonary congestion and Edema
15
Q
What is the histopathology results common with ionophore toxicosis?
A
- Myocardial degeneration and necrosis
- skeletal muscle lesions
- occasional necrosis in liver and kidney
16
Q
What does monensin do to horses?
A
- Myocardial necrosis
- muscle fibers are hyalinized, fragmented and have a loss of cross striations. They are infiltrated and separated by neutrophils, macrophages, and serocellular debris
