Comparison of the sedative effects of medetomidine and xylazine in horses.

The sedative effects in horses of the new alpha 2 agonist medetomidine were compared with those of xylazine. Four ponies and one horse were treated on separate occasions with two doses of medetomidine (5 micrograms/kg bodyweight and 10 micrograms/kg bodyweight) and with one dose of xylazine (1 mg/kg bodyweight) given by intravenous injection. Medetomidine at 10 micrograms/kg was similar to 1 mg/kg xylazine in its sedative effect but produced more severe and more prolonged ataxia, and one animal fell over during the study. Medetomidine at 5 micrograms/kg produced less sedation but a similar degree of ataxia to 1 mg/kg xylazine.     

The lack of effect of parvovirus vaccination on the seminal characteristics of dogs

The onset of ejaculation and development of normal seminal characteristics in six young dogs vaccinated and seroconverting against canine parvovirus did not differ from the accepted range, and by 45 weeks of age the ejaculates were considered to be normal. At one year of age three of the dogs were given a large antigenic stimulus by vaccination once a week for four weeks; this produced no change in the output or characteristics of spermatozoa.     

Reversal of xylazine sedation in dogs.

Intramuscular injections of atipamezole (200 micrograms/kg), doxapram (2.5 mg/kg) and saline (0.1 ml/kg) were compared for their ability to reverse xylazine sedation in dogs. Atipamezole effectively reversed the sedative effects and partially reversed the cardiopulmonary effects of xylazine. Doxapram did not arouse the dogs as much as atipamezole, but it shortened the time taken for them to stand although the dogs were still ataxic.     

Suppressed development of cultured mouse and swine embryos by diethylstilbestrol

Effects of prolonged exposure to the synthetic estrogen diethylstilbestrol (DES) on in vitro development of early mouse and swine embryos were investigated. Two-cell mouse embryos cultured in Whitten's medium (WM) for 192 h were exposed to 10(-4), 10(-7) or 10(-10) M DES dissolved in 1, 10(-3) or 10(-6)% ethanol, respectively. One-cell to eight-cell swine embryos were cultured in WM for 192 h containing 10(-4) or 10(-7) M DES dissolved in 1 and 10(-3)% ethanol, respectively. Embryos cultured in WM containing 1 (0 DES1), 10(-3) (0 DES2) or 10(-6)% ethanol (0 DES3) served as controls. Hatching was inhibited (P less than .05) in mouse embryos cultured in 10(-4) M DES (3.0 +/- 2.1% vs 0 DES1, 25.1 +/- 3.7%). Similar (P greater than .10) percentages of mouse embryos hatched in 10(-7) M DES (36.4 +/- 5.4% vs 0 DES2, 29.1 +/- 5.7%) and 10(-10) M DES (44.4 +/- 4.4% vs 0 DES3, 38.9 +/- 5.3%). Diethylstilbestrol at a concentration of 10(-4) M failed to affect the development of one- to eight-cell swine embryos into blastocysts. However, compared with 0 DES2, 10(-7) M DES reduced (P less than .05) the number of swine blastocysts developing from one- to two-cell (36 vs 78%) and three- to four-cell embryos (50 vs 84%). No significant effects of 10(-7) M DES were detected on the ability of six- to eight-cell swine embryos to develop into blastocysts.(ABSTRACT TRUNCATED AT 250 WORDS)     

The use of two mixtures of ketamine and xylazine to immobilise free ranging Bennetts wallabies

Two mixtures of ketamine and xylazine were evaluated as immobilising agents for the capture of free ranging Bennetts wallabies (Protemnodon rufogrisea). The wallabies were given either a dose of 150 mg ketamine and 187.5 mg xylazine (mixture 1), or a dose of 160 mg ketamine and 80 mg xylazine (mixture 2) by intramuscular injection using a projectile syringe. The quality of induction and immobilisation was similar with both mixtures, although immobilisation occurred more rapidly and lasted longer with mixture 1. Respiration was not depressed and blood gas levels were not significantly changed from normal. Bradycardia was produced but no other arrhythmias were recorded. There was a slight fall in mean arterial pressure. Cloacal temperature was not altered to a significant degree. Recovery was good in the unstimulated animal and no side effects were observed. Mixture 1 was preferred owing to its more rapid immobilising effect.     

Effect of rate and time of gain after weaning on the development of replacement beef heifers

Three experiments were conducted during three consecutive years to compare rate and time of gain of weaned heifer calves on growth, reproductive development and future calf production. Three groups of Angus X Hereford heifers were fed in one of the following regimens from 45 d after weaning until breeding: (1) no gain the first one-half of the development period followed by .91 kg x head-1 x d-1 gain the last one-half; (2) .45 kg x head-1 x d-1 gain the entire trial and (3) .91 kg x head-1 x d-1 the first one-half of the development period and no gain the last one-half. The same diet was fed to all heifers, but the intake was varied to meet weight gain requirements. Wither height and heart girth increased (P less than .05) during the periods the heifers were fed to gain weight. By the end of the feeding trials, there were not differences (P greater than .05) in any of the growth measures. There were no differences (P greater than .05) in age at puberty, conception rate or calf production the following year. Adequate growth and development of replacement heifers is necessary, but much latitude exists in the rate and time of growth between weaning and breeding.     

Estrus, ovulation, conception and embryo survival in confinement-managed gilts of three weight groups

Puberty, cycling, ovulation, conception and embryo survival were determined for gilts managed by a specific regimen in confinement. At weights of 70 to 80, 91 to 100 and 109 to 116 kg (groups A, B, C, respectively) gilts were (1) moved from rearing pens to pens in a separate broodstock building, (2) housed in groups of eight to 10 with unfamiliar penmates and (3) exposed to boar presence in an adjoining pen. Groups A and B were mated at third estrus; group C was mated at first estrus. For the three groups 76, 79 and 79%, respectively, of allotted gilts mated; of these 21, 13 and 11%, respectively, showed estrus again and were remated. Ten, 10 and 11%, respectively, were not pregnant when slaughtered at 25 to 28 d of postmating. Average days on experiment to first estrus were 14, 15 and 16 for groups A, B and C; mean interval between estrous periods was 21 d. Ovulations (13.3, 12.9 and 12.6) and live embryos (11.6, 11.1 and 10.7, respectively) did not differ significantly among groups. None of the reproduction traits were significantly associated with differences in mean age or weight among the three groups at breeding.(ABSTRACT TRUNCATED AT 250 WORDS)