Methyl donor supplementation of gestating sow diets improves pregnancy outcomes and litter size

Maternal intake of B-vitamin and methyl donors can affect sow prolificacy. A total of 1079 Large White/Landrace sows (parities 2–9 at mating) were used in a 2 by 2 by 2 factorial design to determine the effects of two levels of betaine supplementation (0 versus 3 g added betaine/kg feed), two levels of folic acid plus vitamin B12 supplementation (0 versus 20 mg/kg folic acid plus 150 µg/kg vitamin B12) during gestation, and two parity groups (parity 2 and 3 versus parity 4 and greater) on litter size and pregnancy outcomes. The number of sows returning to oestrus post-insemination, as well as the number of early (<Day 30) and late (>Day 30) pregnancy losses were recorded. At farrowing, the total number of piglets born, the number of piglets born alive and dead, as well as the number of mummified fetuses were recorded. Pre-prandial blood samples were collected from a subset of 20 sows/treatment on Days 3, 30 and 107 of gestation to analyse homocysteine. The incidence of early pregnancy loss was reduced (P < 0.001) by folic acid plus vitamin B12 supplementation (0.03 versus 0.07). There was a significant interaction between parity at mating (parities 2 and 3 versus parity 4 and greater) and the addition of betaine or folic acid plus vitamin B12 to the gestation diet on litter size. Litter size was higher (0.5 piglets; P < 0.05) for betaine supplemented, compared with unsupplemented, parity 4 plus sows. Folic acid plus vitamin B12-supplemented parity 2 and 3 sows gave birth to more (P < 0.05) piglets than all other treatment groups. Folic acid plus vitamin B12 supplementation decreased (P < 0.001) plasma homocysteine concentration by 2.2 and 2.8 μM, respectively, on Days 3 and 107 of gestation. However, betaine supplementation decreased (P < 0.05) homocysteine on Day 3 only. Overall, folic acid plus vitamin B12 supplementation decreased incidences of early pregnancy failure and increased litter size in early parity sows, while betaine increased litter size in older parity sows.