Effect of Crude Fiber Level on Ration Digestibility and Performance in Growing-Finishing Swine1

Abstract

Three trials involving a total of 76 weanling pigs were conducted to study the effects of diluting the ration with corn cobs at two protein levels on growth and digestibility of nutrients. Conventional chromic oxide and bomb calorimetry techniques were used in the digestion trials. In trial 1, average daily gain was significantly reduced by the addition of 24.8% corn cobs to either a 10 or 18% protein ration. High protein (18%) rations produced significantly faster rate of gain than low protein (10%) rations. In trial 2, average daily gain was not significantly affected by protein level but was reduced significantly by the addition of 12.4% corn cobs to the ration. Back-fat thickness was significantly less when corn cobs were fed. A significant reduction in apparent digestibility of dry matter, nitrogen-free extract and crude protein was obtained by the addition of corn cobs to the low protein ration. The reduction in dry matter digestibility was of greater magnitude than would be expected on the basis of the energy-diluting effect of an inert material. The percent of digestible energy as determined by bomb calorimetry was similar to, though higher than, TDN values determined using the chromic oxide technique. In trial 3, apparent digestibility of dry matter, crude fiber and nitrogen-free extract was significantly reduced by the addition of 12.4% corn cobs to the ration when measured by conventional (total fecal collection) means. Similar differences were noted when computations were made based on the indicator (chromic oxide) method. The latter method also revealed a reduction in apparent protein digestibility in the presence of added corn cobs.