Summary
Countermeasures to chronic disease, occurred in many swine housings, should be carefully studied, if intended to complete the rationalized swine production systems. As one of the effective countermeasures, a segregated early weaning system has been introduced to the swine husbandry, in which the weaning age of pig is a very important factor.HomePage
In this paper, the authors discussed the appropriate weaning age of pig, measuring the periodical changes of gamma-immunoglobulin content in blood plasma of 10 head of SPF sows and 19 head of pigs produced from the above sows. IgG content of nursing pigs decreased with the age increasing, and the decreasing rate of IgG content became smaller with the age increasing (P<0.01). For a seasonal effect, there was a tendency for the decreasing rate of IgG content in the season from winter to spring (P<0.08). Furthermore, the decreasing rates of IgG content with the age of pigs were highly correlated to the diurnal range of temperature (r=-0.82) and relative humidity (r=0.88) of air surrounding pigs. However, there were no relationships with the birth weight of pigs, IgG content of sows and a number of litters. Considering the immunity level of pigs, an early weaning, especially less than 14 days, should be recommended, as possible. But the effect of early weaning is little after 16 to 18 days of age, in such case it would be necessary to control the environmental temperature in swine housings in which diurnal change of temperature should be depressed.Keywords: swine production system, large-scaled husbandry, appropriate weaning age, immunity, gamma-immunoglobulin