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The Optimum Crude Fiber Level in Rations of Growing Pigs

Royal Agricultural College¹, Sweden

Abstract

The optimum crude fiber level in rations of growing pigs was studied in 4 experiments of 4 lots each, and of 4 pigs in each lot, the total number of pigs being 64. The pigs were fed ad libitum from self feeders. Each experiment embraced a preliminary period from 20–30 kg. of body weight. The trial proper was divided into three periods: period 1 from 30 to 50 kg., period 2 from 50 to 70 kg., and period 3 from 70 to 100 kg. of weight. The rations were balanced in all respects, with the exception of crude fiber content. By substituting wheat straw meal for grain, this content was raised from 4.8 percent (lot I) to 9.3 percent (lot IV) of the dry matter of the feed mixtures. The feed evaluation was based on metabolizable energy determined in experiments with swine.

The daily amount of consumed feed increased, though in a slight degree, with increased crude fiber content. On the other hand, the daily amount of metabolizable energy decreased at the same time. A crude fiber content of dry matter of 6.57 percent was optimum as to gain in weight, and a content of 7.26 percent as to feed efficiency. The economical optimum was at 6.64 percent. The maximum daily gain in weight of the pigs averaged 629 gm. in period 1, 806 gm. in period 2, 870 gm. in period 3, and 768 gm. in periods 1–3 (from 30 to 100 kg. of weight). The minimum of metabolizable energy per kg. of weight gain averaged 9.20 mcal, in period 1, 10.72 mcal, in period 2, 12.12 mcal, in period 3, and 11.03 mcal, in periods 1–3. A tendency to lessened fatness of the carcasses appeared when the crude fiber content was raised. Finally, the importance of balancing the rations as to their crude fiber content is discussed.

¹ Institute of Animal Nutrition.