Changes in liveweight and behaviour of alpaca dams and offspring following weaning

The effects of offspring sex, weight, age, and level of interaction with the dam on responses to weaning were examined to assist in the development of a weaning protocol for alpacas. In the first study, preand post-weaning activities, and weight change over Days -12-0,0-7 and 7-16 with respect to weaning, were recorded for 20 dam-offspring (hembra-cria) pairs aged 81-200 days. Pre-weaning changes in dam and offspring weights were positively related (P<0.05). Although heavier crias tended to be found closer to their dams than lighter crias (P<0.05) no additional effect of age on the dam-offspring relationship was found. Following weaning, cria growth rates were low over Days 0-7 but improved over Days 7-16, and hembra weight change followed the same pattern. Over Days 0-2, grazing and sitting activities of hembras and crias were replaced by standing and walking along paddock fencelines, although by Day 2 fenceline activities had decreased (P<0.05). Crias which were more frequently observed at fencelines had lower post-weaning growth rates (P<0.05). In the second study, pre-weaning sucking behaviour, and weight change over Days -30-0, 0-8 and 8-16 with respect to weaning, were recorded for 19 hembra-cria pairs aged 124-160 days. During 10 hours of observation on Days -5 and -4, the total duration of sucking by individual crias varied from 0-18 minutes, and the mean +/- SEM duration of sucking was 1.94 +/- 0.113 minutes. Cria sucking behaviour was positively related to growth rate prior to and weight at weaning (P<0.05). As in the first study, pre-weaning changes in dam and offspring weights were positively related (P<0.05). Following weaning, growth rates of the crias were depressed and the hembras lost weight over Days 0-8 and 8-16. The changes in growth rate and behaviour in Studies 1 and 2 indicated that weaning can be stressful for hembras and crias. However, there was no evidence from either study that pre-weaning behavioural or physical characteristics were related to the changes.     

Vascular characteristics of the cartilage and subchondral bone of the distal radial epiphysis of the young foal

The vascular features of the distal epiphysis of the radius of 27 foals aged from 3 weeks premature to 120 days postpartum were determined. The limbs were perfused with barium, and the distal radius was sawn into sagittal slabs which were decalcified, cut into thin slices and radiographed. More arteries approached areas of thick cartilage than thin cartilage. In thick cartilage, vessels in a lattice network were observed, and adjacent to these vessels was sinusoidal filling in the epiphyseal subchondral bone, which had a similar pattern to sinusoidal filling in the metaphysis. The sinusoidal filling adjacent to thick cartilage was at the predisposition site for epiphyseal osteomyelitis lesions in foals. This particular type of bone infection occurs commonly in the foal, but much less commonly in other species. The vascular features of the immature epiphysis may account for the predominance of epiphyseal osteomyelitis in the foal.     

The pharmacokinetics of thiamphenicol in lactating cows

The pharmacokinetics of thiamphenicol were studied after intravenous and intramuscular administration of 25 mg/kg body weight in lactating cows. Distribution (t _1/2) and elimination (t _1/2) half-lives of 6.10±1.39 min and 1.60±0.30 h, respectively, were obtained after intravenous administration. The body clearance was 3.9±0.077 ml/kg per min and the apparent volume of distribution was 1220.79±256.67 ml/kg. The rate at which thiamphenicol appeared in the milk, as indicated by the penetration half-life (t _1/2P) (serum to quarters), was found to be 36.89±11.14 min. The equivalent elimination half-life (t _1/2E) (quarters to serum) from the milk was 3.62±1.06 h and the peak thiamphenicol concentration in the milk was 23.09±3.42 µg/ml at 2.5±0.32 h.After intramuscular injection, the elimination half-life was 2.2±0.40 h, the absorption half-life was 4.02±1.72 min and the peak concentration in the serum was 30.90±5.24 µg/ml at 23±8.4 min. The bioavailability after intramuscular administration approached 100%. The penetration half-life was 50.59±6.87 min, the elimination half-life was 5.91±4.97 h and the mean peak concentration in the milk was 17.37±2.20 µg/ml at 3.4±0.22 h.Abbreviations AUC area under the concentration-time curve - CAP chloramphenicol - C _max peak concentration - IM intramuscular - IV intravenous - TAP thiamphenicol - t _1/2 distribution half-life - t _1/2 elimination half-life - V _c volume of central compartment - V _d volume of distribution     

Optimal cultivar mixtures in focal plant diseases

This paper deals with a study on the effects of mixtures of partially resistant cultivars in focus forming plant diseases. The focus expansion velocity in a mixture of two partially resistant cultivars depends on four parameters, the focus expansion velocity in a crop of cultivar 1 only and in a crop of cultivar 2 only, the net-reproduction in a crop of cultivar 1 and of cultivar 2, respectively. An explicit equation is developed for the damage of a cultivar mixture where the crop is infected by two physiological races of the pathogen. It is shown that cultivar mixtures exist where damage is smaller than in crops of either of the two cultivars only. A simple explicit formula is given on the basis of which it can be decided whether an optimal mixture exists for a given pathosystem.     

A 2000-year tree ring record of annual temperatures in the sierra nevada mountains

Tree ring data have been used to reconstruct the mean late-season (June through January) temperature at a timberline site in the Sierra Nevada, California, for each of the past 2000 years. Long-term trends in the temperature reconstruction are indicative of a 125-year periodicity that may be linked to solar activity as reflected in radiocarbon and auroral records. The results indicate that both the warm intervals during the Medieval Warm Epoch ( approximately A.D. 800 to 1200) and the cold intervals during the Little Ice Age ( approximately A.D. 1200 to 1900) are closely associated with the 125-year period. Significant changes in the phase of the 125-year temperature variation occur at the onset and termination of the most recent radiocarbon triplet and may indicate chaotic solar behavior.