Influence of unsaturated to saturated ratio of fatty acids reaching the duodenum on postruminal digestion of stearic acid in Holstein steers fed a high-fat finishing diet.

Alejandro Plascencia,Alberto Barreras,Richard Zinn,Yissel A

doi:10.5455/javar.2021.h535

Abstract

Objective:To evaluate the influence of the unsaturated to saturated ratio of fatty acids (FAs) reaching the duodenum on postruminal digestion of FAs, mainly focused on stearic acid (C18:0).Materials and Methods:Six Holstein steers [208 ± 3 kg initial live weight (LW)] with cannulas in the abomasum and proximal duodenum were used in a replicated 3 × 3 Latin square design. Steers were fed a fixed amount of a basal steam-flaked corn-based diet containing 8% supplemental fat and were daily infused via abomasum with 0, 67, and 165 gm oleic acid (C18:1). The experiment lasted for 42 days.Results:The daily total FA (TFA) intake (dietary FA intake plus abomasal infusion of oleic acid) represented a 1.78, 2.10, and 2.56 gm TFA/kg LW ratio. The unsaturated to saturated ratio of FAs entering the duodenum increased (p < 0.01) as level C18:1 infusion into the abomasum increased. Infusion of C18:1 tended (quadratic component, p = 0.07) to improve postruminal TFA digestion, being maximal for the 67 gm/day infusions. This increase in TFA digestion was due to increased (quadratic component, p = 0.03) postruminal C18:0 digestion (postruminal digestion of the other FAs was not different, p ≥ 0.13). Conclusion:Increasing the unsaturated to saturated ratio of FAs entering the small intestine will enhance intestinal C18:0 digestion. This positive effect is expected to be more likely beneficial when FA intake is high (and thus, the duodenal flow of FA is high), but this benefit looks diminished when the quantity of TFA reaching the intestine exceeds the proportion of 2.13 gm FA/kg LW.

Highlights

The net energy of maintenance (NEm) value assigned by the current standards [1] for supplemental fats for feedlot cattle is from 5.65 to 6.03 Mcal/kg
In as much as DM intake of the basal diet was constant for all steers, differences in fatty acids (FAs) intake and saturated to unsaturated FA ratio between treatments was due to the C18:1 infused into the abomasum (Table 2)
Analyzing data from other experiments carried out with feedlot cattle fed high-energy diets supplemented with fats which report FA intakes and FA intestinal flows [5,9,16,17,18,19], the relationship between FA intake versus the duodenal FA flow is as follows: Y = 1.134X (R2 = 0.91), where Y = duodenal FA flow and X = FA intake, gm/day

Summary

Introduction

The net energy of maintenance (NEm) value assigned by the current standards [1] for supplemental fats for feedlot cattle is from 5.65 to 6.03 Mcal/kg. In as much as feedgrade fats largely (~90%) comprise fatty acids (FAs), their net energy value is closely associated with FA digestibility [2]. Fat intake level has the greatest impact on fat digestion [3,4]. This effect results from the limitations on intestinal absorption of saturated FA due to upper limits on bile production [5]. Another factor that limits intestinal FA digestion is the saturated-to-unsaturated FA ratio reaching the intestine. As a consequence of ruminal biohydrogenation of unsaturated FA, C18:0 accounts for 65%

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Results

Conclusion