The effect of dam parity on growth, white blood cell count, haemoglobin and immunoglobulin levels of weaner pigs

Dam parity affects the growth rate of finisher pigs and gilt progeny have lower growth rates than progeny from multiparous sows, although the magnitude of this effect varies between herds (Hermesch and Li 2013). Gilt progeny had lower levels of immunoglobulin (Ig) G and IgA at birth (Klobasa et al. 1986). However, differences in IgG and IgA were the reverse between piglets from gilts v. multiparous sows at 2 (IgA) and 3 (IgG) weeks of age, due to higher de-novo synthetisation of Ig in piglets from gilt litters (Klobasa et al. 1986). Similarly, Miller et al. (2013) found no dam-parity effect on multiple immune parameters measured in piglets. This study hypothesised that gilt progeny have reduced growth and similar haematological and immunoglobulin levels in weaner pigs in comparison to progeny from multiparous sows.

All traits were recorded from January 2013 until October 2014 in 799 Large White pigs that originated from 217 litters and 209 dams. Serum samples were taken at an age of 37.7 ± 3.4 days and a weight of 11.3 ± 2.17 kg after being weaned at 27.1 ± 2.4 days with a mean weight of 8.9 ± 1.30 kg. Capture ELISA were performed using purified Ig (Sigma Aldrich, Castle Hill, NSW, Australia) or known reference serum as standards and polyclonal antibody sets (Bethyl Laboratories, Montgomery, TX, USA). Quantitative analysis of the samples was executed using four parameter logistic fit (4PL) software. Dam parity and weekly batch were fitted as fixed effects for all traits using the SAS software (v9.4, SAS Institute Inc., Cary, NC, USA). Sex had significant effects on growth rate until weaning (GRW), white blood cell count (WBC) and haemoglobin (HGB). Age was fitted as a linear covariable for IgA. Dam parities above the sixth parity were defined as one level in the analyses.

The statistical power to detect differences between parities was large due to the large number of records and dam parity was a statistically significant effect for most traits in Table 1. Dam parity affected growth rate most, which was lowest for gilt progeny. For example, pre-weaning growth of gilt progeny was 20 g/d and 28 g/d lower than growth of progeny of second- and fourth-parity (P2, P4) sows. Similarly, growth from weaning to 5 weeks (GR5) was 25 g/d and 34 g/d lower in gilt progeny in comparison to progeny from P2 and P4 sows. These differences can be expressed relative to the mean (or standard deviation, s.d.) of each trait to make a comparison between traits possible. The growth gap of gilt v. P4 progeny was 9% of the mean (63% of the s.d.) for GRW and 16% of the mean (29% of s.d.) for GR5. Gilt progeny had superior WBC and HGB than progeny from multiparous sows. Further, IgA levels were not significantly different in gilt progeny compared to progeny from multiparous sows. The levels of IgG in progeny tended to increase with parity number and gilt progeny had significantly lower IgG levels than progeny from P3 or P6 sows; however, dam parity was not a significant effect overall.

Table 1.  Least square means (standard error) for dam parity (P1 to P6) of growth rate until weaning (GRW) and from weaning to 5 weeks (GR5) as well as white blood cell count (WBC), haemoglobin (HGB) and immunoglobulin (IgA, IgG) levels in weaner pigs

These results illustrate the reduced capacity of younger sows to support the growth potential of their progeny. Haematological and immunoglobulin levels of weaner pigs were not inferior in gilt progeny.