Use of Oral Tolerance Tests to Investigate Disaccharide Digestion in Neonatal Foals

1. Use of Oral Tolerance Tests to Investigate Disaccharide Digestion in Neonatal Foals Authors: L. Rice, E.A. Ott, D.K. Beede, C.J. Wilcox, E.L. Johnson, S. Lieb, and P. Borum Presented by: S-- S--

2. Introduction • Purpose • Investigate possible replacements for lactose in artificial diets for lactose-intolerant foals; to determine disaccharide digestion in neonatal foals. • Previous Research • The negative effects of high osmolarity diets has not been documented in foals • Development pattern of disaccharidase activity unknown for foals less than one week old • Results gathered using oral tolerance tests and homogenized intestinal tissue samples from foals have been shown to agree

3. Treatments • 20% (wt/vol) solutions • Maltose, Lactose, and Sucrose • Dosed at 1 g/kg BW • Glucose • Dosed at 0.5 g/kg BW

4. Experimental Procedures • Animals • Two thoroughbred and 11 quarter horse foals used. • Dams and foals maintained on bahiagrass (Paspalum notatum) pasture and a supplemental balanced concentrate mix to meet the mares’ NRC requirements.

5. Experimental Procedures(continued) • Foals • Nursed within 2 h postpartum • Allowed to nurse normally first 6 h postpartum • Weighed at 6-8 h postpartum and on d 5 • Blocked by sex at birth and assigned randomly to 4 treatment groups • Remained with dams during trial periods

6. Experimental Procedures(continued) • Blood Sampling and Treatment Administration • Jugular vein catheters fitted to foals 6 h postpartum • Foals allowed to resume normal activity • After nursing, foals muzzled for 2 h fast • Blood collected (time=0) • Oral administration of treatment • Foals remuzzled for rest of trial period • Blood collected every 15 min for 1 h, then every 30 min. for 3 h • Procedure repeated on d 3 and d 5 postpartum

7. Experimental Procedures(continued) • Analyses • Blood collected in tubes containing EDTA • Stored on ice • Centrifuged and plasma removed and frozen • Plasma glucose concentration determined using the Trinder peroxidase method • Absorbance measured at 505 nm

8. Experimental Procedures(continued) • Statistical Analyses • Performed using the GLM procedure of SAS with time as a class variable • Equations for the time curves were obtained using reduced models with time as a continuous variable

9. Table 1. ANOVA model for changes in plasma glucose

10. Table 2. Pooled regression model for plasma glucose time curves (reduced model)

11. Results and Discussion • Fasting Blood Glucose • Fasting glucose concentrations = Data from plasma samples at time=0 • Data from all foals pooled since there had been no treatment • No differences due to sex found, therefore data from both sexes pooled • [Blood Glucose] fasted foals d 1 = 4.14 mM • d 3 = 6.08 mM • d 5 = 6.31 mM

12. Results and Discussion(Continued) • Glucose Absorption Time Curves • Time was a continuous variable • Only treatment x day curves shown • Changes in plasma glucose levels from glucose, lactose, maltose, and sucrose for days 1, 3, and 5 shown.

13. Table 3. Polynomial equations for changes in plasma glucose over time Regression coefficientsa aThe equation is represented by U = b0 + b1x + b2x2 + b3x3 + b4x4 + b5x5 + b6x6; U = plasma glucose (mM) and x = minutes, 0 ≤ x ≤ 240.

14. Day 1 Curves

15. Day 3 Curves

16. Day 5 Curves

17. Glucose Time Curves(Glucose) Day 1 Day 5 Day 3

18. Glucose Time Curves(Lactose) Day 1 Day 5 Day 3

19. Glucose Time Curves(Maltose) Day 1 Day 5 Day 3

20. Glucose Time Curves(Sucrose) Day 1 Day 5 Day 3

21. Conclusion • Maltase and sucrase activity very low in neonatal foals • Glucose may be feasible replacement for lactose in formulas for foals

22. Questions?