Effect of birth litter size, birth parity number, growth rate, backfat thickness and age at first mating of gilts on their reproductive performance as sows
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Abstract
The present study was performed to evaluate retrospectively the influence of birth
litter size, birth parity number, performance test parameters (growth rate from birth
to 100kg body weight and backfat thickness at 100kg body weight) and age at first
mating (AFM) of gilts on their reproductive performance as sows. Traits analysed included
remating rate in gilts (RRG), litter size, weaning-to-first-service interval (WSI),
remating rate in sows and farrowing rate (FR). Data were collected from 11 Swedish
Landrace (L) and 8 Swedish Yorkshire (Y) nucleus herds and included 20712 farrowing
records from sow parities 1-5. Sows that farrowed for the first time during 1993-1997,
having complete records of performance test and AFM, were followed up to investigate
their subsequent reproductive performance until their last farrowing in 1999. Analysis
of variance and multiple regression were applied to continuous data. Logistic regression
was applied to categorical data. The analyses were based on the same animals and the
records were split into six groups of females, i.e. gilts, primiparous sows, and sows
in parities 2-5, respectively. Each additional piglet in the litter in which the gilt
was born was associated with an increase of her own litter size of between 0.07 and
0.1 piglets per litter (P<0.001). Gilts born from sow parity 1 had a longer WSI as
primiparous sows compared with gilts born from sow parity 4 (0.3 days; P<0.05) or
parity 5 (0.4 days; P<0.01). Gilts with a higher growth rate of up to 100kg body weight
had a larger litter size (all parities 1-5; P<0.05), shorter WSI (all parities 1-5;
P<0.05) and higher FR (parities 2 and 5; P<0.05) than gilts with a lower growth rate.
Gilts with a high backfat thickness at 100kg body weight had a shorter WSI as primiparous
sows (P<0.001) compared with low backfat gilts, and 0.1 piglets per litter more as
second parity sows (P<0.01). A 10 day increase in AFM resulted in an increase in litter
size of about 0.1 piglet for primiparous sows (P<0.001) and a decrease (P<0.05) for
sow parities 4 and 5.