DEMOGRAPHY AND GROWTH: A UNIFIED TREATMENT OF OVERLAPPING GENERATIONS

We construct a unified overlapping-generations framework of equilibrium growth that includes the Blanchard “perpetual youth” model, the Samuelson model, and the infinitely lived–agent model as limit specifications for a “realistic” two-parameter survivorship function. We assess how the limit specifications compare with the general survival function, and analyze how exogenous changes in demographic conditions affect equilibrium growth and savings rates. Predicted effects are consistent with some cross-country correlations between demographic conditions and growth rates.

Temporal pattern of feeding and drinking behaviour of gestating sows

The aim of the present study was to investigate the temporal pattern of feed and water intake behaviour of gestating sows housed in a dynamic group. The dataset included 90 sows (parity 1 to 7). Feed and water intake were recorded by electronic feeding and drinking stations. To describe the feed and water intake behaviour single visits were combined into meals and drinking bouts. A log survivorship function identified the characteristic interval length to differentiate between two bouts. Interval lengths larger than 12 min separated two meals (29 min two drinking bouts). The meal and drinking bout criteria were used to derive the following traits: feeding and drinking duration per day (FD, DD), interval duration within feeding (pauseF) or drinking (pauseW) meal, feeding and drinking meal duration per day (FMD, DMD) and feeding and drinking visits per day (FV, DV). Additionally, an eating rank was calculated according to the order of the sows at the feeding station. The results showed that nulliparous and primiparous sows had higher FD, pauseF, FMD and FV in contrast to biparous and multiparous sows (P<0.05). The DD of primiparous sows was significantly lower than that of older sows. The eating rank increased over time while nulliparous sows increased their rank more slowly than older sows. Low to moderate repeatabilities were found for feed intake traits (0.23 to 0.41); higher repeatabilities for drinking traits (0.45 to 0.55) and eating rank (0.71) indicating high variation between sows, which could be used for the identification of diseases.