The effect of parity on haemoglobin levels in sows prior to farrowing and in 1-day-old piglets

A decreased haemoglobin level in piglets is associated with a decreased survival rate (Rootwelt et al. 2012). While haemoglobin levels have been studied in piglets, few studies have focused on sows. In sows, low iron levels were associated with reduced reproductive performance (Buffler et al. 2017). Haemoglobin levels in sows decrease with increasing parities (Gannon et al. 2011a). It has been suggested that the body haemoglobin reserves cannot be restored between parities (Auvigne et al. 2010). In this study it was hypothesised that with an increasing parity, both the sow haemoglobin and the piglet haemoglobin decrease.

In 2012 and 2013, haemoglobin samples were collected from 171 Landrace and 216 Large White sows with 581 litters on a breeding farm in the region of Adelaide, South Australia. The sow parity ranged from 1 to 5+, there were between 75 and 162 observations per parity. A droplet of blood was collected from sows 5.0 ± 2.7 days before farrowing via the ear vein. The haemoglobin levels were estimated using the HemoCue Hb²⁰¹⁺ analyser (HemoVue AB, Angelholm, Sweden), which was validated by Gannon et al. (2011b). Some sows had observations in multiple parities, resulting in 568 observations on haemoglobin level. The haemoglobin levels of three piglets in each litter (selected visually as a light, medium and heavy piglet) were measured on 1-day-old piglets before iron supplementation based on the same procedure used in sows. The average haemoglobin level of the three piglets was used for analysis (n = 503). A linear model was fitted in R with haemoglobin measurement date (66 levels) and parity (five levels) added as fixed effects (R v3.3.2, R Foundation, Vienna, Austria). Breed was also tested as a fixed effect and was found not to be significant. The R function TukeyHSD was used to determine which means were significantly different from each other.

Sow haemoglobin ranged between 74 and 146 g/L, with a mean of 111.6 ± 12.8 g/L. Average piglet haemoglobin ranged between 58 and 149.5 g/L, with a mean of 103.3 ± 15.1 g/L. The linear model showed a decreasing trend of sow haemoglobin levels with increasing parity (R² = 0.27), while the average piglet haemoglobin stayed relatively constant with increasing parity (R² = 0.12) (Table 1).

Table 1.  The least-squares mean (SE) level of sow haemoglobin and the average litter haemoglobin across parities

This study showed that with increasing parity, sow haemoglobin level decreased, while piglet haemoglobin levels stayed constant. The haemoglobin levels found in this study were lower than found in the study of Gannon et al. (2011a). A haemoglobin level of 100 g/L has been suggested as the normal-range threshold for sows (Gannon et al. 2011a). In this study, the mean sow haemoglobin level was above this threshold for all parities. However, 6.8% of the sows in Parity 1 and 36% of the sows in Parity 5+ were below this threshold. Awareness of the increasing danger of anaemia in later parities could help identify problem cases earlier, thereby ensuring that sow health and welfare is not compromised.