South African Journal of Animal Science
On-line version ISSN 2221-4062
Data (n = 4836) from a pig company in Namibia recorded over the period 2002 - 2007 were analysed to: (i) compare performance of two sow lines for the age at first farrowing (AFF), number born alive (NBA), life total born (LTB), weaning-to-conception interval (WCI), farrowing index (FI) and; (ii) estimate preweaning piglet mortality, non-productive sow days (NPSD) and replacement rates in two sow lines. The mating scheme involved a within herd grandparent programme where line A was the grandparent stock and line C the parent stock. NBA and WCI were analyzed as repeated measures traits. The least square means (d) for AFF were 363.3 ± 3.1 and 353.6 ± 2.4 for A and C, respectively. The NBA increased from first to fifth parity and then declined, but females served during the summer months of October - December (mean monthly temperature = 24.5 ºC) had smaller litter sizes, compared to those in other seasons. Sows weaning piglets in the cold months of May - September (mean monthly temperature = 15.4 ºC) had the shortest WCI. LTB increased by 10.9 ± .1 piglets per unit increase in parity at culling. The FI was 2.4 for both lines. The preweaning piglet mortality was 10.7% for A and 14% for C. The NPSD was 76 d in A and 52 d in C; replacement rate was 50.5% in A and 42.1% in C. Component traits of reproduction indicate depressed performance during the summer period. Management efforts should be directed at further mitigation of heat stress in breeding pigs and reduction of preweaning piglet mortality in line C.
Keywords : Reproduction; non-productive sow days; NBA; swine; mortality.