As environmental concerns increase in the U.S., there is a push to go "green". This has fueled the development of ethanol production in the U.S. as a renewable source of energy. In the U.S., corn is used to produce ethanol. Therefore, displacement of corn used in the animal industry to ethanol production has, inevitably caused an increase in the price of corn. Replacing conventional ingredients, such as corn, in monogastric diets with lower cost by products can be attractive economically. The objective of this study was to determine if exogenous enzymes that free reducing sugars from fiber will increase the dispensability of bound nutrients in the economically favorable by-product of ethanol production, distillers dried grains with solubles (DDGS). Effects of non-starch polysaccharidase (NSPase) inclusion rates and combinations with phytase on the ability to release reducing sugars were investigated. Distillers dried grains with solubles was tested in vitro in combination with hemicellulase (0, 0.1, 1, and 10 U/g of DDGS), cellulase (0, 1.5, 15, and 150 U/g of DDGS), xylanase (0, 2.5, 25, and 250 U/g of DDGS), ï ¢ glucanase (0, 0.006, 0.06, and 0.6 U/g of DDGS), and phytase (0, 250, 500, and 1,000 FTU/kg of DDGS). Results indicated an inhibitory effect of phytase on the ability of NSPases to release reducing sugars from DDGS (P = 0.0004). A second study was conducted to determine individual enzyme kinetics of NSPase on pure substrates when combined with increasing concentrations of phytase. Cellulase (P = 0.03), xylanase (P = 0.09), and ï ¢-glucanase (P = 0.06) combined with increasing concentrations of phytase showed a reduction in the velocity of reducing sugars release from pure substrate. However, we speculate that due to the inability to reach Vmax, the Lineweaver-Burk results were inconclusive. The 1/Km was calculated for all enzymes, and the presence of phytase increased 1/Km for xylanase (P = 0.006). However, -1/Km did not change for cellulase (P = 0.62), ï ¢-glucanase (P = 0.20), and hemicellulase (P = 0.13). In addition, the 1/Vmax was calculated for all enzymes, and the presence of phytase decreased 1/Vmax for cellulase (P = 0.03) and ï ¢ glucanase (P = 0.01). However, the presence of phytase resulted in no change for the 1/Vmax for xylanase (P = 0.81) and hemicellulase (P = 0.14). The slopes of the regression lines for the Lineweaver-Burk plots showed no effect of the presence of phytase for cellulase (P = 0.40) and hemicellulase (P = 0.27). However, the presence of phytase decreased the linear slope for xylanase (P = 0.006), and increased the linear slope for ï ¢ glucanase (P = 0.006). In summary, phytase appears to act as an inhibitor of NSPase activity in the in vitro digestion on DDGS; however, inconsistent results from the inhibition curves preclude us from determining the type of inhibition. / Master of Science

Pigs can consume a wide range of feeds to meet their nutritional needs and there is a renewed interest in the use of cheaper nutrient resources for animal feeding. Forages have been proved to be a substantial source of nutrients for pigs, however, the bulk of the existing work has focused on sows and grower-finisher pigs above 50 kg. This study was conducted during May-June 2009 at the Agricultural Research Council (Irene, Pretoria) to determine the voluntary forage intake and nutrient digestibility in growing pigs fed a mixed diet (concentrate + Kikuyu grass). Twenty five 8 weeks old Large White x Landrace crossbred pigs (27 ± 3.8 kg) were blocked by weight into 5 groups of 5 pigs each. One of 5 treatments (A, B, C, D and E), corresponding to 100, 90, 80, 70 and 80 % of a basal concentrate ration, respectively, was randomly assigned to a pig within each block. Indoor treatments were either fed the concentrate only (A) or also received freshly cut Kikuyu grass (Pennissetum clandestinum) ad libitum (B, C and D). Only treatment E animals were housed outdoors in Kikuyu grass paddocks while all other treatments were housed indoors. Forage intake was recorded daily and also estimated using a pair of n-alkanes as markers. Nutrient and diet digestibility were calculated using acid-insoluble ash (AIA) and dotriacontane (C32) as markers. The results showed that the concentrate intake (CI) in treatments A, B and C was significantly different from treatments C and E (P < 0.05) and there was positive correlation between the concentrate level and its intake (P < 0.01). The recorded intake of Kikuyu grass (RKI) and the animal’s average daily gain (ADG) were similar between treatments (P > 0.05). The estimated (EKI) and recorded (RKI) Kikuyu grass intakes were not influenced by CI or the level of concentrate allowance (CL) and RKI was higher (P < 0.05) than EKI. Digestibility estimates with AIA were higher than C32 Keywords: Dotriacontane; Kikuyu; growth performance; forage; monogastrics estimates (P < 0.05). It was concluded that Kikuyu grass intake was not affected by the reduction of the concentrate level allowance. It was proposed that forage intake in a mixed diet (forage + concentrate) was more dependant on its own characteristics than the concentrate’s nutritional value. / Agriculture, Animal Health and Human Ecology / M. Sc. (Agriculture)

Pigs can consume a wide range of feeds to meet their nutritional needs and there is a renewed interest in the use of cheaper nutrient resources for animal feeding. Forages have been proved to be a substantial source of nutrients for pigs, however, the bulk of the existing work has focused on sows and grower-finisher pigs above 50 kg. This study was conducted during May-June 2009 at the Agricultural Research Council (Irene, Pretoria) to determine the voluntary forage intake and nutrient digestibility in growing pigs fed a mixed diet (concentrate + Kikuyu grass). Twenty five 8 weeks old Large White x Landrace crossbred pigs (27 ± 3.8 kg) were blocked by weight into 5 groups of 5 pigs each. One of 5 treatments (A, B, C, D and E), corresponding to 100, 90, 80, 70 and 80 % of a basal concentrate ration, respectively, was randomly assigned to a pig within each block. Indoor treatments were either fed the concentrate only (A) or also received freshly cut Kikuyu grass (Pennissetum clandestinum) ad libitum (B, C and D). Only treatment E animals were housed outdoors in Kikuyu grass paddocks while all other treatments were housed indoors. Forage intake was recorded daily and also estimated using a pair of n-alkanes as markers. Nutrient and diet digestibility were calculated using acid-insoluble ash (AIA) and dotriacontane (C32) as markers. The results showed that the concentrate intake (CI) in treatments A, B and C was significantly different from treatments C and E (P < 0.05) and there was positive correlation between the concentrate level and its intake (P < 0.01). The recorded intake of Kikuyu grass (RKI) and the animal’s average daily gain (ADG) were similar between treatments (P > 0.05). The estimated (EKI) and recorded (RKI) Kikuyu grass intakes were not influenced by CI or the level of concentrate allowance (CL) and RKI was higher (P < 0.05) than EKI. Digestibility estimates with AIA were higher than C32 Keywords: Dotriacontane; Kikuyu; growth performance; forage; monogastrics estimates (P < 0.05). It was concluded that Kikuyu grass intake was not affected by the reduction of the concentrate level allowance. It was proposed that forage intake in a mixed diet (forage + concentrate) was more dependant on its own characteristics than the concentrate’s nutritional value. / Agriculture, Animal Health and Human Ecology / M. Sc. (Agriculture)