Journal Article

Effect of diets rich in starch or digestible fiber on glucose metabolism of ewes and goats in mid-lactation

Knupp, L S, Decandia, M, Cannas, A, Atzori, A S, Bomboi, G C, Molle, G, Gaspa, G, Lunesu, M F

2016

Overview

This study evaluated if dietary carbohydrate type (starch vs. fiber) can modulate glucose metabolism in ewes and goats in mid-lactation. At c.a. 95 d in milk (DIM), 20 ewes and 20 goats were subdivided into two groups. The first one (10 sheep and 10 goats) received a high-starch diet (HS; 24.1% starch, 36.4% NDF, 15.4% CP, DM basis) and the other (10 sheep and 10 goats) a highly-digestible fiber diet (HF; 10.5% starch, 46.8% NDF, 15.4% CP, DM basis), obtained by replacing corn and barley meal with soybean hulls. At 153 DIM, glucose tolerance tests (GTT) were performed on 10 sheep and 10 goats selected from each group. Diet was withdrawn in the afternoon of the day before the test. One mL of a 50% glucose solution per kg of BW was injected into the jugular vein of each animal. Blood samples were collected 15 min before and at 5, 10, 15, 30, 45, and 90 min after glucose injection. At 165 DIM, all the animals were subjected to blood postprandial sampling at 30, 60, 120, 180, and 240 min post feeding. Blood glucose was assayed by an enzymatic-colorimetric method. Blood glucose concentration data were analyzed by the PROC MIXED of SAS with repeated measurements. For GTT the incremental area under the curve (AUC), the fractional turnover rate (k), and the half-life were calculated and data were analyzed with a two-factor (diet within species and species) ANOVA. The -15-min glucose concentration was higher in sheep than goats (73.5 vs. 53.6 mg/dl; P < 0.005) but was not affected by diet. During the GTT, the mean blood glucose concentration was greater in sheep than goats (228.1 vs. 209.2 mg/dl; P < 0.05) and in HS goats than HF goats (217.9 vs. 198.6 mg/dl P < 0.01), whereas it did not differ between HS sheep and HF sheep. The values of AUC, k and half-life were not affected by species or diet. Regarding the postprandial sampling, mean blood glucose concentration was higher in sheep than goats (60.3 vs. 50.3 mg/dl; P < 0.001) and in HS goats than HF goats (52.2 vs. 48.1 mg/dl; P < 0.001), whereas it did not differ between HS sheep and HF sheep. In conclusion, it seems that the source of carbohydrates modulated blood glucose metabolism in goats but not in sheep.

• Publisher: Oxford University Press
• Subject: Animal lactation / Barley / Blood / Blood levels / Caprinae / Carbohydrates / Colorimetry / Corn / Data analysis / Diet / Glucose / Glucose metabolism / Glucose tolerance / Goats / Half-life / Hulls / Jugular vein / Lactation / Metabolism / Ovis aries / Sampling / Sheep / Soybeans / Starch / Studies / Turnover rate / Variance analysis