Effects of duration of betaine supplementation on growth performance and blood IGF-1 in light- and normal-weight weaner pigs under commercial conditions

Context. Betaine supplementation has been reported to increase insulin-like growth factor 1 (IGF-1) in pigs. Betaine is not generally added to weaner pig diets due to a lack of knowledge on the duration of supplementation and effect on targeted bodyweight class. Light-weight weaners, known for their inferior growth performance, may benefit from betaine supplementation during the early days post-weaning. Aims. This experiment aimed to identify the timing of betaine supplementation over the weaner phase (early (0-7 days) or late (7-35 days) post-weaning periods) and targeted weaning weight class (light vs normal). Methods. The experiment followed a 2 x 2 x 2 factorial arrangement for studying the effects of 0.1% betaine supplementation during early (0-7 days post-weaning) and late (7-35 days post-weaning) weaner phase in light-weight and normal-weight weaners. One hundred and forty-four pens (18 pigs/pen) of weaned pigs (26 days age) were allocated into a 2 x 2 x 2 factorial arrangement on the basis of weaning weight class ((light (3.6 +/- 0.75 kg, mean +/- s.d.) vs normal (6.6 +/- 0.84 kg, mean +/- s.d.)), early weaner phase diet (control vs 0.1% betaine) and late weaner phase diet (control vs 0.1% betaine). Basal diets contained sufficient methionine and choline as per industry practice. Growth performance during early, late and whole weaner phase were recorded. Blood IGF-1 was measured at 7 days and 35 days post-weaning. Key results. Supplementing 0.1% betaine during the early weaner phase reduced (P < 0.05) growth rate over the early post-weaning period (0-7 days) in both light- and normal-weight weaners, although blood IGF-1 concentration (7 days post-weaning) was not affected. Betaine supplementation during early or late weaner phase did not affect growth performance over the late weaner phase (7-35 days), whole weaner phase (0-35 days) or blood IGF-1 concentration (35 days) of light- or normal-weight weaners. Light-weight weaners had a lower feed intake, and a lower average daily gain than did the normal-weight weaners during the early, late and whole post-weaning periods (all P < 0.01). Conclusions. Light-weight weaners had inferior production performance during the weaner phase, which was not improved by betaine supplementation. Implications. Betaine supplementation is not recommended in the weaner phase when other dietary methyl donors are sufficient.