Effect of concurrent infection with Ostertagia circumcincta and Trichostrongylus vitrinus on the performance of lambs

The interaction between Ostertagia circumcincta and Trichostrongylus vitrinus was investigated in lambs continuously infected over 12 weeks. Four groups of seven lambs were given either zero, 1000 T vitrinus larvae per day, 2500 O circumcincta larvae per day or infected concurrently. Overall liveweight gain was reduced by 17, 20 and 30 per cent in T vitrinus, O circumcincta and concurrent infection, respectively. T vitrinus infection significantly lowered serum phosphorus concentrations by week 4. In the concurrent infection the decline in phosphorus concentration was more gradual and only differed significantly from the controls during the final four weeks of the trial. There were no significant differences between the total numbers of T vitrinus or O circumcincta recovered from single or combined infections. The lack of an additive effect on performance may be due to a delayed establishment of T vitrinus in the presence of O circumcincta.     

Anesthesia and surgery of laboratory animals

This article reviews anesthetics and anesthetic techniques applicable to small laboratory animals. Anesthetic and analgesic dosage tables are presented for each species to guide the practitioner. The actions of the various agents are reviewed in the text, and key references are presented. Surgical considerations are also reviewed.     

Effects of age, castration, and season on difficulty of pelt removal in lambs

Sixty-four white-faced rams and wethers were dressed with the aid of a commercial pelt puller. The effects of age, castration, and season on difficulty of pelt removal and pelt damage were evaluated. Lambs were divided into two age groups (5 and 12 mo) within gender (ram and whether) and season (spring and fall). A greater force (P less than .05) was required to remove pelts from rams than from wethers in both 5- and 12-mo-old groups. Older lambs slaughtered in the fall required more force (P less than .05) to remove their pelts than did those slaughtered in the spring, but differences by season did not exist for 5-mo-old lambs. The difference between rams and wethers in percentage of live weight that was closely shorn pelt weight was not significant (P greater than .05). The area of grain crack in the flank expressed as a percentage of total area of the skin was lower (P less than .05) for skins from 5-mo-old lambs and ram lambs than it was for skins from 12-mo-old lambs and wether lambs, respectively. Factors involved in difficulty of pelt removal in ram lambs included crosscut shoulder weight, fat firmness, and carcass weight. Difficulty of pelt removal in wether lambs was best predicted by including crosscut shoulder weight and bodywall thickness in multiple regression equations.