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When growing pig increase their body weight (BW) the energy digestibility also increases and may differ between breeds of pigs or between lines selected on other criteria than digestion. However, little is known about the variability in energy digestibility within a line or a breed of pigs, especially when fibrous diets are fed. Variations in diet composition, feed technology, animal development (BW) or animal breed can impact on digestibility coefficients of nutrients and energy. For the present purpose, 20 Large White castrated male growing pigs originating from four boars (five per boar), and three to four sows per boar. From 25 kg to slaughter these pigs were allocated individually in digestibility cages and were fed a unique diet with a high dietary fibre diet (18% NDF). The experimental diets contained 0.90 g digestible lysine per MJ net energy. The measurements lasted over 10 successive weeks and started when pigs reached at least 30 kg BW until to 95 kg BW. Apparent faecal energy, nitrogen and organic matter digestibility was recorded. Each week, faeces were totally collected over 5 days and the feed dry matter intake over the same days was recorded.
All digestibility coefficients were affected by period (P<0.001) with a continuous and linear increase over the time or with BW. Energy digestibility was increased by 0.6 point per 10 kg BW increase; the higher value is probably dependent on the high dietary NFD content. The rate of increase was not affected by boar origin (no interaction; P>0.05). The digestibility coefficients were affected by boar origin (P<0.005 for energy), with about 2 points for energy between the extremes (81.7% v. 79.5%), and there was no marked interaction between boar origin and period.
In conclusion, this study confirms the increase in energy digestibility with BW increase; this increase would be independent on genetic background. The results also suggest that energy digestibility and digestion in general would be dependent on heritable genetic variability in growing pigs. These preliminary results suggest the possibility of selecting growing pigs for an increased digestive efficiency when fed high DF diets. The mechanisms involved in the genetic differences of digestion (microbiote, genomics, gut structure and physiology, etc.) deserve further studies.
J. Noblet, H. Gilbert, Y. Jaguelin-Peyraud and T. Lebrun 2013. Evidence of genetic variability for digestive efficiency in the growing pig fed a fibrous diet. Animal, 1-6. doi:10.1017/S1751731113000463