A comparative kinetic study of thiamphenicol in pre-ruminant lambs and calves

Eight healthy Holstein-Friesian calves and 8 Massese lambs of either sex (10–15-days old) were used to evaluate the pharmacokinetics of thiamphenicol after intravenous (i.v.) and oral (p.o.) administration (30 mg/kg). Plasma concentrations of thiamphenicol were determined by high-performance liquid chromatography on blood samples collected over 24 h following treatment. Pharmacokinetic variables of the drug were calculated for both species and after both administration routes. After intravenous administration of thiamphenicol, a rapid distribution phase was followed by a slower elimination phase and, when thiamphenicol was administered p.o., the bioavailability was about 60% in both species. The higher volume of distribution and the longer biological elimination half-lives in pre-ruminant compared with adult animals indicate that thiamphenicol distributes widely into the extravascular compartment of pre-ruminants. Interspecies differences were observed in the kinetic behaviour of thiamphenicol with respect to peak plasma concentration (Cmax), time of peak plasma concentration (Tmax), elimination half-life ðT1=2Þ and total clearance ðClBÞ. In conclusion intravenous or oral administration of 30 mg/kg of thiamphenicol provides plasma concentrations higher than minimum effective concentrations inhibiting bacterial growth (MICs) against most pathogens in pre-ruminant lambs and calves

Association between a polymorphism at the Stearoyl CoA Desaturase locus and milk production traits in Italian Holsteins

Associations between stearoyl-CoA desaturase (SCD) gene polymorphisms and milk production traits (milk, fat, and protein yields, fat and protein contents, somatic cell score) were investigated on a sample of 701 lactations of 313 Italian Holsteins. Test-day records (5,097) were analyzed with a mixed linear model that included the fixed effects of herd, date of test, parity, genotype at the SCD locus, and lactation interval nested within SCD genotype, and the random effect of cow. An effect of the SCD genotype on milk and protein yields was detected, with VV cows producing more milk (about 2 kg/d) and protein (about 0.07 kg/ d) compared with AA cows. The contribution of the SCD locus to the phenotypic variance of the 2 traits was about 0.015. These results suggest a possible use of the SCD locus in gene-assisted selection programs for the improvement of milk production traits in dairy cattle, although large-scale studies in different breeds are required