Abstract
For the most part solutions to farm animal welfare issues, such as piglet mortality, are likely to lie within the scientific
disciplines of environmental design and genetic selection, however understanding the ecological basis of some of the
complex dynamics observed between parent and offspring could make a valuable contribution. One interesting, and often
discussed, aspect of mortality is the propensity for it to be sex-biased. This study investigated whether known physiological
and behavioural indicators of piglet survival differed between the sexes and whether life history strategies (often reported
in wild or feral populations) relating to parental investment were being displayed in a domestic population of pigs. Sex ratio
(proportion of males (males/males+females)) at birth was 0.54 and sex allocation (maternal investment measured as piglet
birth weight/litter weight) was statistically significantly male-biased at 0.55 (t35 = 2.51 P = 0.017), suggesting that sows
invested more in sons than daughters during gestation. Despite this investment in birth weight, a known survival indicator,
total pre-weaning male mortality was statistically significantly higher than female mortality (12% vs. 7% respectively z = 2.06
P = 0.040). Males tended to suffer from crushing by the sow more than females and statistically significantly more males died
from disease-related causes. Although males were born on average heavier, with higher body mass index and ponderal
index, these differences were not sustained. In addition male piglets showed impaired thermoregulation compared to
females. These results suggest male-biased mortality exists despite greater initial maternal investment, and therefore
reflects the greater susceptibility of this sex to causal mortality factors. Life history strategies are being displayed by a
domestic population of pigs with sows in this study displaying a form of parental optimism by allocating greater resources
at birth to males and providing an over-supply of this more vulnerable sex in expectation of sex-biased mortality.
Original language | English |
---|---|
Pages (from-to) | 9 - 6 |
Number of pages | 2 |
Journal | PLoS ONE |
Volume | 7 |
Publication status | First published - 2012 |
Bibliographical note
1023365Keywords
- Animal welfare
- Behavioural indicators