Reproductive performance of purebred Hampshire sows in Sweden

The objective of this study was to retrospectively investigate causes of variation in the reproductive performance of purebred Hampshire sows in Sweden. Data analysed comprised farrowings between 1992 and 1998 from five Swedish nucleus herds and included 6347 litters from 2210 sows. The main traits analysed were litter size, weaning-to-first service interval (WSI), farrowing rate, remating rate and age at first farrowing. Analysis of variance was used for the statistical analysis of continuous data. Logistic regression was applied for categorical data using the GLIMMIX macro of the SAS programme. Factors included in the analyses were parity number, herd, year within herd, lactation length and month of the year (season). On average, Swedish Hampshire sows had 9.8 total piglets born / litter, 9.0 piglets born alive / litter, a WSI of 5.0 days, a 22% remating rate, a 68% farrowing rate and were 386 days of age at first farrowing. Parity influenced litter size at birth (P , 0.001) and WSI (P , 0.01). Season influenced (P , 0.001) WSI, farrowing rate and age at first farrowing, but not litter size. However, the interaction between season and parity for litter size was significant. A longer lactation length resulted in a shorter WSI but the interaction between lactation length and season for WSI was significant (P , 0.001). WSI influenced subsequent number of total piglets born / litter (P , 0.01), farrowing rate (P , 0.001) and remating rate (P , 0.001).  2001 Elsevier Science B.V. All rights reserved.