Epsilon Archive for Student Projects

Abstract

Half of Sweden’s 140 000-150 000 sows are culled and replaced by 75 000 gilts annually. Culling of old sows is necessary and allows new breeding material to enter the herd. However, many of the culled sows are young, and have not yet become profitable at the time for culling. Therefore, it is an important question for the pig industry, how to raise gilts to sows with a high and sustainable production level.

Several rearing factors are thought to influence the reproductive performance as well as the longevity of the sow. However, it is not well studied in which way these factors act. This thesis aims to find relationships between rearing factors and the performance of sows, so that a suitable way of raising gilts can be proposed. As a part of this work a study was performed, with the purpose of comparing how herds with high respectively low production results and culling frequencies raised their gilts. It is also described how gilt rearing is performed and varies between herds. Data was based on an interview study and the herd monitoring program PigWin Sugg.

The analysis at herd level showed that purchasing gilts was associated with a lower annual sow removal rate, compared with raising gilts on the own farm. In herds with own production of replacement gilts, the use of a breeding computer program when selecting gilts, resulted in a small proportion of litters from gilts in the farm. Herds with the highest average mating age for gilts had the highest number of live born pigs in the first litter and the herds that accepted more returns to oestrus had better longevity and most pigs born alive during lifetime of their sows.

Housing gilts in pens with slatted floor and concrete during mating and pregnancy was associated with a high proportion of sows culled due to leg and claw injuries and few pigs born alive in the first litter compared with gilts housed on deep straw litter. However, gilts raised in pens with slatted floor and concrete between the age of 12 and 24 weeks had most live born pigs in the first litter.

The crude protein content in the gilt feed did not influence the production results or culling reasons. However, a low feeding intensity gave a high proportion of sows culled due to leg and claw injuries. A high feeding intensity at mating (flushing) was associated with better longevity.

Only 55 of the total contacted 125 herds participated in this study and the result showed great variations in how gilts were reared in different herds. Several other rearing factors, beyond those analysed in this paper, can be of interest to analyse in how they affect the performance of sows. To successfully raise gilts to sows with a high and sustainable production, it is important to consider already known relationships between rearing and performance. Therefore, advices in how to raise gilts (based on literature and the results from this study) are presented in the end of this paper.