Effects of dietary fiber content and different fiber-rich ingredients on endogenous loss of fat and fatty acids in growing pigs

Abstract

Background Determination of the endogenous loss of fat (ELF) is used to adjust for the estimation of true total tract digestibility (TTTD) of fat in diets and ingredients. Any factor which affected ELF may further affect the digestibility of fat, including sources and concentrations of fat and fiber in the diet. There are some reports of determining the ELF using regression methods based on different levels of fat intake, while reports on effects of dietary fiber content and different fiber-rich ingredients in pig diets on ELF are very limited. Therefore, the objective of this study was to determine the effects of dietary fiber content and different fiber-rich ingredients on endogenous losses of fat and fatty acids at the end of ileum and throughout the entire intestinal tract in growing pigs. Methods In Exp. 1, the effect of fiber content on endogenous loss of fat was determined using six growing pigs (Duroc × Landrace × Yorkshire; 27.6 ± 2.4 kg), fitted with a T-cannula at the end of ileum. The experimental design was a 6 × 6 complete Latin square design with six periods of feeding and six diets. The six experimental fat-free diets were formulated to include graded levels of neutral detergent fiber (NDF) (0, 40, 80, 120, 160 and 200 g/kg) and soybean hull (SH) was the only fiber source, providing 0, 75, 150, 225, 300 and 375 g/kg, respectively. Chromic oxide was included at 4 g/kg in all diets as an indigestible marker. In Exp. 2, six crossbred growing barrows (27.6 ± 1.6 kg) were used and the experimental design was the same as for Exp. 1. The six fat-free diets were formulated to include six common fiber-rich ingredients and the concentration of NDF was 100 g/kg. The six fiber-rich ingredients were defatted rice bran (DRB), sugar beet pulp (SBP), rice hull (RH), corn germ meal (CGM), SH and wheat bran (WB) and they were fed at represented 250, 270, 145, 250, 170 and 280 g/kg in the diet, respectively. Results In Exp. 1, the endogenous loss of fatty acids profile did not change as dietary NDF increased in growing pigs. The endogenous losses of fat, C16:0, C18:0, C18:1, C18:2, total unsaturated fatty acids (UFA) and total saturated fatty acids (SFA) in growing pigs at the end of ileum and throughout the entire intestinal tract increased linearly as NDF content of diets increased. The endogenous losses of fat, as well as C16:0 and C18:0 throughout the entire intestinal tract also increased quadratically as NDF content of diets increased. The ELF increased from 0.71 to 3.14 g/kg of dry matter intake (DMI) and 0.56 to 8.21 g /kg DMI at the end of ileum and throughout the entire intestinal tract in growing pigs, respectively. The ELF occurred in the hindgut except for the growing pigs fed 0 and 4% NDF in their diets. The endogenous losses of C16:0 and UFA occurred primarily in the upper regions of the gut and the greatest endogenous losses of C18:0 occurred in the hindgut. The endogenous losses of fat, individual SFA and total SFA througho...

Endogenous Losses of Fat and Fatty Acids in Growing Pigs Are Not Affected by Vegetable Oil Sources but by the Method of Estimation

“…Instead of feeding traditional diets based on natural ingredients (corn, barley, soybean meal, canola meal), cornstarch and soy protein isolate containing lower fiber content were formulated in the present diets. Previous studies reported that greater dietary fiber content resulted in increasing endogenous fat excretion [2,6,7]. In addition, purified ingredients with high digestibility may decrease endogenous fat excretion [22,23].…”

“…1 Sixteen observations in each equation. 2 Calculated from regression equation y = ax + b, where x = dietary fat intake (g/kg of DMI), y = apparently digested fat (g/kg of DMI) of total intestinal tract. 3 Values for endogenous loss of individual fatty acid in pigs fed palm oil, soybean oil, flaxseed oil or rapeseed oil were compared, but no differences were observed (p > 0.10 and standard error of the means = 2.57).…”

“…These endogenous fats are mixed with dietary lipids then partially digested and absorbed. The unabsorbed fraction is excreted and considered as the endogenous loss of fat (ELF) [1,2]. Precise measurement of these inevitable losses is of great significance for the determination of true digestibility of fat and determining fatty acid requirements.…”

“…Previous studies have focused on comparing the ELF of intact oils with their corresponding extracted oils [6][7][8]. In addition, effects of dietary fiber on ELF have been well researched by Kil et al [6] and Chen et al [2]. Saturation degree and carbon chain length of fatty acids have an impact on digestion and absorption of oils in pigs [9], and thus may impact reabsorption of endogenous fat.…”

“…One of the most common methods is to provide graded dietary concentrations of fat and perform a regression to estimate endogenous loss and true digestibility of fat [11]. A second method requires feeding the animal a fat-free diet and measuring the fat content in feces, which represents the endogenous losses [2]. Regression methods have been widely used to evaluate ELF in pigs [6][7][8]11], but research on fat-free diet methods is limited.…”