156 Influence of viscosity and fiber on nutrient digestibility and intestinal physiology in growing pigs

Fiber is known for decreasing nutrient utilization in pigs. The addition of fiber alters diet viscosity, but our understanding of the effect of diet viscosity on nutrient digestibility is limited. This knowledge is necessary for improving dietary fiber utilization and when evaluating alternative feed ingredients. Thirty-six T-cannulated barrows (n = 6/treatment; initial BW = 26.5 ± 3.9 kg) were fed either corn-soybean meal (CSBM) basal diets or CSBM with 30% distillers dried grains with solubles as fiber source (CSBM+DDGS). The viscosity of diets were modified by using non-viscous cellulose (CEL), medium-viscosity carboxymethylcellulose (MCMC), or high-viscosity carboxymethylcellulose (HCMC) to assess viscosity effects on nutrient digestibility and intestinal physiology. After 29 d on diets, ileal digesta were collected to determine viscosity and apparent ileal digestibility (AID). Also, intestinal tissue and contents were harvested to determine morphometry, goblet cell quantitation, and digestive enzymatic activity. Data were analyzed using a linear mixed model with treatments as fixed effects and initial BW as a random effect. Results are shown in Table 1. No interactions were observed between viscosity and diets. Inclusion of MCMC and HCMC increased viscosity of supernatant and whole digesta compared with CEL. Increasing diet viscosity decreased AID of DM and CP in pigs fed MCMC and HCMC compared with pigs fed CEL, respectively. The AID of DM and CP were greater in CSBM than CSBM+DDGS. Inclusion of CMC increased crypt depth in the jejunum and goblet cell area in the ileum compared with pigs fed CEL regardless of basal diet fed. Digesta trypsin activity was not different among treatments, but inclusion of CMC increased amylase activity by 43% in jejunal digesta compared with CEL. The addition of DDGS reduced AID; however, viscosity affected intestinal morphology and function, suggesting that viscosity is the main characteristics of fiber affecting nutrient utilization of pigs.

Effect of Diet Viscosity on the Operation of the Pharyngeal Pump in the Blood-Feeding Bug Rhodnius Prolixus

1. The rate of pumping and total number of pump strokes was recorded whilst Rhodnius prolixus fed on measured amounts of artificial diets. 2. Increasing the viscosity of the diet caused a decline in both the frequency with which the pharyngeal pump operates and the average stroke volume of the pump. 3. In 5th-instar Rhodnius, the stroke volume tends toward a maximum value of about 60 nl at viscosities lower than abeut 3 cP. 4. Feeding rates (volume per unit time) agree with Poiseuille's law at high viscosities, but are less than predicted at low viscosities. 5. The maximum power output of the pump occurs at a viscosity between 1 and 3 cP, which is probably the range of the effective viscosity of blood in tubes with the dimensions of Rhodnius stylets. 6. These results are inconsistent with a hypothesis of a central nervous system ‘oscillator’ controlling the pump muscle, independent of feedback, but are consistent with a model involving peripheral feedback from stretch receptors, with an appropriate delay.