Leptin in sow milk: impact on offspring plasma concentrationsand growth
A Mostyn1, JC Litten2, KS Perkins2, J Laws2, ME Symonds1 & L Clarke2
Neonatal mortality is greater in the leaner commercial porcine genotypes compared to the Meishan breed. Leptin is a 16 kDa protein involved in energy regulation, a number of studies have demonstrated leptins presence in maternal milk. Meishan sows have a significantly higher body fat content than commercial pigs, but it is unknown whether they produce more leptin in milk. The extent to which this dietary supply provides the neonate with leptin and any effects on growth and development are unknown. This study investigated if leptin in maternal milk differed between Meishan and commercial sows; and whether this influenced piglet plasma leptin concentrations and growth.
Eight Meishan and 6 commercial sows were entered into the study and had a milk sample taken daily from the day of parturition to the 4th postnatal day. The piglet with median birth weight in each litter was selected and had weight and a venous blood sample taken daily from the first day of life to the 4th. Plasma leptin concentrations were measured using an ELISA (Linco Multi species kit).
Leptin was higher in commercial sow milk throughout the study (average milk leptin, Meishan, 9.8±1.3; commercial, 26.0±6.0 ng/ml (P<0.05)); but this did not affect plasma leptin in the piglets. Milk leptin was significantly positively associated with piglet plasma leptin in the Meishan group on days 0 and 1 of postnatal age, but on day 2 this relationship was reversed. Average milk concentration of leptin was significantly positively related to body weight and growth rate as well as gut, heart and spleen weight in Meishan piglets.
In conclusion, we have found a significant disparity in the provision of leptin in Meishan and commercial sows milk. These changes are not translated to plasma concentrations, suggesting first pass metabolism, protein binding or digestion prior to leptin to reaching the plasma. We have also found that milk leptin concentrations are related to a number of growth parameters in the piglet and despite the high concentrations observed in milk not being translated to plasma, milk leptin may play an important role in organ growth during early neonatal development.