This study investigated the productive adaptability of pig breeds under different smallholder production conditions in Vietnam, comparing an indigenous with a Vietnamese improved breed. Fieldwork was conducted in four villages with different remoteness in North Vietnam from 2001 to 2002, in 64 households keeping the improved Mong Cai or indigenous Ban as sow breeds and progeny for fattening. Four visits per farm yielded 234 structured interviews. Reproductive performances were derived from 135 litters. Individual weights of pigs (n = 755) were obtained. Data were analysed by regression, linear and generalised linear, especially loglinear models.
Two distinct pig production systems were identified, that differed in remoteness, market access, resource availability, distribution of pig breeds and pig production intensity. Higher performances of 1.4 and 1.5 litters year− 1, 8.4 and 8.4 piglets weaned litter− 1, 66.6 and 93.0 kg piglets weaned sow− 1 year− 1, and 136 and 177 g day− 1 ADG were found in two villages near town with semi-intensive production conditions and a high rate of improved Mong Cai sows and MC and LW × MC offspring in the observed population. Lower performances of 1.1 and 1.1 litters year− 1, 4.6 and 5.5 piglets weaned litter− 1, 20.5 and 30.9 kg piglets weaned sow− 1 year− 1, and 66 and 85 g day− 1 ADG were observed in parallel to higher incidences of indigenous Ban pigs away from town under extensive conditions. Total live weight offtake per household per year was higher near town and in one village distant to town. MC and LW × MC remained even under demand-driven conditions below the performance potential reported for improved genotypes. Under resource-driven conditions with a saving-oriented production pattern, the higher-yielding but more demanding Mong Cai might not be an efficient production alternative as a further performance reduction can be assumed. A considerable live weight output was observed under resource-driven conditions and with a higher percentage of crossbred LW × Ban offspring in the population, possibly representing a promising production alternative. Factors influencing the performance expression of pigs, and the suitability of different methods for the assessment of performance parameters on-farm are discussed. 相似文献
Current and prior veterinary cancer registries are few in number and scattered. Different inclusion criteria, dissimilar collection methods and variable reference population estimation methods pose obstacles in the comparisons between veterinary and human cancer registries. Veterinary cancer registries have yielded information on the risk and incidence of different cancer types in certain breeds and geographical regions, as well as provided information on genetic and environmental risk factors in some cancers. The objective of this article is to review the prior and current veterinary cancer registries, the information they have contributed and to discuss different issues relating to their structure including inclusion criteria, study populations, reference populations utilized in evaluations, recorded variables and the outcome from these. 相似文献
Neutral landscape models were originally developed to test the hypothesis that human-induced fragmentation produces patterns
distinctly different from those associated with random processes. Other uses for neutral models have become apparent, including
the development and testing of landscape metrics to characterize landscape pattern. Although metric development proved to
be significant, the focus on metrics obscured the need for iterative hypothesis testing fundamental to the advancement of
the discipline. We present here an example of an alternative neutral model and hypothesis designed to relate the process of
landscape change to observed landscape patterns. The methods and program, QRULE, are described and options for statistical
testing outlined. The results show that human fragmentation of landscapes results in a non-random association of land-cover
types that can be describe by simple statistical methods. Options for additional landscape studies are discussed and access
to QRULE described in the hope that these methods will be employed to advance our understanding of the processes that affect
the structure and function in human dominated landscapes. 相似文献
Applied ecology could benefit from new tools that identify potential movement pathways of invasive species, particularly where
data are sparse. Cost surface analysis (CSA) estimates the permeability (friction) across a landscape and can be applied to
dispersal modelling. Increasingly used in a diversity of applications, several fundamental assumptions that might influence
the outputs of CSA (cost surfaces and least-cost pathways) have yet to be systematically examined. Thus, we explore two issues:
the presumed relationship between habitat preferences and dispersal behaviour as well as the degree of landscape fragmentation
through which an organism moves by modelling a total of 18 sensitivity and dispersal scenarios. We explored the effect of
fragmentation by altering the friction values (generally assigned using expert opinion) associated with patch and linear features.
We compared these sensitivity scenarios in two sites that differed in fragmentation. We also used eastern grey squirrels (Sciurus carolinensis) as an example invading species and compared diffusion models and two contrasting cost surface dispersal scenarios. The diffusion
model underestimated spread because squirrels did not move randomly through the landscape. Despite contrasting assumptions
regarding dispersal behaviour, the two cost surfaces were strikingly similar while the least-cost paths differed. Furthermore,
while the cost surfaces were insensitive to changes in friction values for linear features, they were sensitive to assumptions
made for patch features. Our results suggest that movement in fragmented landscapes may be more sensitive to assumptions regarding
friction values than contiguous landscapes. Thus, the reliability of CSA may depend not only on the range of friction values
used for patches but also the degree of contiguity in the landscape. 相似文献