Duration and sex-dependent effect of betaine supplementation on growth performance and carcass backfat of finisher pigs

Context. Developing strategies to reduce carcass fatness is vital to the profitability of animal production, particularly in a market where excessive backfat causes price penalties. Studies have shown that betaine supplementation has inconsistent effects on carcass fatness, which are due in part to variability in the betaine dose, duration of supplementation and growth state. Grower pigs have a greater lean:fat deposition ratio than do finisher pigs and are more sensitive to anabolic stimuli. The betaine-spared energy may be deposited as more lean tissue when betaine is supplemented during the grower phase. We hypothesised that 0.1% betaine supplementation within the grower phase is more effective in reducing carcass backfat than is supplementing in the finisher phase. Such an effect may also interact with sex. Aims. The objective was to optimise betaine supplementation duration to reduce carcass backfat thickness of finisher pigs. Methods. Eighty pens of pigs (39 pigs/pen) were allocated to a 2 x 2 x 2 factorial arrangement on the basis of sex (immunocastrated male vs female pigs), betaine supplementation (0 vs 0.1%) during the grower phase (10-16 weeks of age) and the finisher phase (16 weeks of age to approximately 22 weeks of age). Growth performance, carcass weight and backfat thickness were recorded. Key results. Betaine supplementation during the grower phase or finisher phase reduced backfat thickness in female pigs by 0.7 mm and 0.5 mm respectively. But the effect in reducing female backfat diminished when the supplementation extended to both grower and finisher phases. No such effect was found in immunocastrated male pigs (grower phase diet x finisher phase diet x sex, P < 0.05). Betaine supplementation during the finisher phase reduced growth rate by 40 g per day, regardless of sex (finisher phase diet, P < 0.05). Conclusions. The effect of betaine in reducing carcass backfat was observed in female pigs only. Additionally, this occurred only when betaine was supplemented for 6 weeks in either the grower or finisher period, with supplementation for the 12-week period negating the effect. Implications. The effectiveness of betaine supplementation in reducing carcass backfat is sex and duration dependent.