Simultaneous Determination Of Fluctuating Age Structure And Mortality From Field Data

The use of a Leslie matrix for analysis of a population normally implies that the age structure of the population is known. However, this restriction can be overcome if the population can be partitioned into recognisably different stages, and some information on stage duration and fecundity is available, in which case the age structure may be determined by the analysis itself. As an example of this approach we consider the estimation of the mortality rate applying to a population from a sequence of observed stage frequency vectors. The technique does not require that the population has attained a stable age structure nor that distinct cohorts can be recognised.

Effect of supplementation silage ("Festuca dolichophylla, Avena sativa and Vicia sativa") on weight gain and mortality in adult alpacas ("Vicugna pacos")

This study was conducted in order to evaluate the effect of supplementation with silage (Festuca dolichophylla, Avena sativa and Vicia sativa) on weight gain and mortality in adult alpacas, during the months of dry season (June to August) in Huancavelica region. 300 female alpacas 3 and 4 years of age (physiological state: pregnant) were used, which were assigned to the following treatments: SP, grazing only PSE15, grazing plus supplementation of 1.5 kg of silage. Alpacas were supplemented once daily. In each alpaca they were recorded live weight at the beginning and end of the experiment. The weight gain was -0.02 y 2.05 kg for SP and PSE15 respectively (p <0.001) treatments. Mortality was 5.3% and 2.7% for SP and PSE15 respectively (p=0.073) treatments. It can be concluded under the conditions of this trial silage supplementation has effect on weight gain and maybe also on mortality in alpacas.