As we apply genetic selection for more prolific sows, the challenges for piglet survival increase; piglets are smaller and more vulnerable at birth, face greater competition for the vital early colostrum intake, and are thus more at risk of dying from hypothermia, starvation and crushing. To address these challenges, the PROHEALTH project is investigating different genetic and management interventions which might improve the vitality of the newborn piglet and the maternal behaviour of the sow in order to reduce mortality risk.
A collaborative study between Newcastle University and the JSR Genetics breeding company is looking for new neonatal and maternal traits which might be utilised in future genetic selection strategies. Observations from more than 1500 farrowings, with individual records on more than 21000 piglets, are now being analysed to assess the heritability of different sow and piglet traits and their association with piglet mortality risk.
Piglet maturity at birth is of great importance and early results show that, in addition to birthweight, other simple visual indicators of intra-uterine growth retardation (IUGR) such as the head shape of the piglet affect their survival prospects. Preliminary analysis at the piglet level has shown that piglets affected by IUGR have a much higher probability of being born dead or being born alive but dying within 24 hours compared with piglets not affected by IUGR when at lower birth weights (Figure 1), although this relationship reverses as birth weight increases.
The piglet level heritability for intra-uterine growth retardation (as de ned by head shape) is low at 0.05 ±0.016. Therefore, growth retardation may be considered a property of the dam, in part due to uterine capacity. However, uterine capacity cannot be equated to litter size and is thus difficult to measure on farm. A novel approach to this may be to consider the proportion of IUGR piglets in a litter as a proxy for uterine capacity. Sow level analysis shows that the heritability for the proportion of IUGR piglets in a litter is 0.20 ±0.055, thus suggesting it could be a suitable proxy for uterine capacity to be included in future breeding programmes.
With so many vulnerable offspring, another key factor is the care taken by the mother as she changes posture, a time when crushing of piglets can easily occur. A novel approach to characterise the movement patterns of farrowing sows uses small rump-mounted accelerometers, which record the 3-dimensional changes in acceleration of her body.
Preliminary results show that both the type of flooring in the farrowing pen and the leg conformation of the sow can influence the speed of body movements and the associated risk of crushing. The shape of the fore- and hind-limbs has been shown to have an effect on the speed of descent of the sow when lying, whereas the placement of the hind legs under the body of the sow seems to have an effect on the side to side movement in posture changing (Figure 2.) Once the methodology is fully developed, these accelerometer data may be used to reduce piglet crushing by identifying the structural adequacy of the farrowing environment, such as suitability of floor type, or selecting sows with better movement characteristics.
Since sudden and careless movements of the sow are one of the biggest factors affecting crushing risk, management procedures which might reduce their occurrence are being investigated in a study involving more than 400 highly prolific sows, carried out by the Danish Pig Research Centre (SEGES). Brief daily contact with the sows (friendly scratching for 15 seconds) in the days immediately before farrowing has been shown to reduce their fear of humans, especially where sows initially showed marked negative responses. An alternative and less labour-demanding approach to generate calm sows which is being evaluated is the use of a background of classical music in the farrowing room, which should reduce the likelihood of startle responses to other environmental disturbances. Personnel on the farms running these trials, when asked about the effect of the two treatments, stated that they found sows in all treatment groups less reactive and easier to handle than sows in the non-treatment group. Furthermore, they did not consider the treatments to be time consuming or annoying. The effect of these calming measures on sow restlessness at the time of farrowing and the consequences for piglet mortality are now being assessed.
Work in the PROHEALTH project is demonstrating how the challenges of prolificacy for keeping piglets alive can be addressed by incorporating new maternal traits in the breeding programme or by implementing new management approaches in day to day practice.