ABSTRACT
Background: information regarding the metabolic hormones in different metabolic states of high producing dairy cows can aid high producing herds to manage and resolve the metabolic and production problems. Furthermore, it can be considered as a tool to evaluate metabolic status of dairy cows. Herd managers can also evaluate the energy input- output relationships by assessing the metabolic profile to prevent and control negative energy balance, metabolic disorders and nutritional insufficiencies
Objectives: the present study was performed to clarify the metabolic hormone profile in each metabolic state of high producing Holstein dairy cows. The results of this research can reveal the normal metabolic state of these animals
Methods: 25 multiparous Holstein dairy cows were divided to 5 equal groups containing early, mid and late lactations, far-off and close-up dry periods. Blood samples were collected from all cows and sera were analyzed for concentrations of triiodothyronine [T3], thyroxine [T4], free T3 [fT3], free T4 [fT4], cortisol and insulin like growth factor-1 [IGF-1]
Results: serum T3 concentration in early lactation group was significantly higher than other ones [p<0.05]. T4 levels in early and mid-lactation dairy cows were lower than other studied groups, significantly. The cows in early lactation and close-up dry periods had the highest and the lowest serum fT3 concentrations, respectively [p<0.05]. fT 4 in far-off dry cows was significantly higher than others. The highest and the lowest circulating levels of cortisol were detected in mid and late lactation periods, respectively [p<0.05]. The lowest concentrations of IGF1 were detected in early lactation period and its highest levels were seen in mid and late lactation and faroff dry cows [p<0.05]
Conclusions: metabolic hormones change in different metabolic states of high producing Holstein dairy cows. The presented metabolic hormone profile can be considered as criteria to monitor the metabolic status of dairy cows at different metabolic states
ABSTRACT
Salinomycin is a rnonocarboxylic polyether ionophore with antimicrobial properties. It is a dietary additive used as a growth promoter for ruminants and as a coccidiostat in chickens. The mechanism of action of ionophores at the cellular level is to selectively bind certain ions creating intra and extracellular biochemical disturbances. Clinical signs of ionophore intoxication are non specific and similar in all species and include tachycardia, muscle tremor, restlessness, loss of appetite, incoordination, muscular weakness and continual panting. The present study was conducted to determine the changes in ECG parameters and possible arrhythmias and their types due to experimental salinomycin toxicosis in sheep. Acute toxicity with the ionophore [0.5 mg/kg; intravenously] was induced in 6 mixed breed female sheep. A corresponding volume of sterile saline was intravenously injected in each control sheep [n=6]. Blood samples were collected before and at various time intervals after the administration of either salinomycin or saline solutions. Following centrifugation, serum biochemical parameters [ALT, AST, CK, LDH and total protein] were measured using conventional laboratory methods. In both groups, the heart sounds of sheep were carefully monitored and the electrocardiogram [ECG] was recorded. Salinomycin caused a significant [P<0.05] increase in the levels of ALT, AST, LDH and CK in the experimental animals. The mean heart rate in the control group was significantly lower than that in the experimental sheep. Numerous arrhythmias such as sinus tachycardia [11 cases], ventricular premature contraction [2 cases] and T-wave inversion [3 cases] were recorded in the experimental sheep. Acute salinomycin intoxication seems to cause numerous arrhythmias in sheep which might be due to the pathological effect of the ionophore on the myocardium