Effects Of Meal Frequency On Nutrients Digestibility, Glucose And Lipid Metabolism In Pigs

The objective of Exp. 1 was conducted to investigate the effects of feed intake(FI) levels and dietary nutrient concentration on the determination of apparent ileal digestibility (AID) and total tract digestibility (ATTD) of nutrients and GE for growing pigs. A total of 48 growing pigs (initial BW, 40.7 ± 1.3 kg) were surgically fitted with simple T-cannulas at the distal ileum and assigned to 6 treatment groups in a 2 × 3 factorial arrangement of 2 diets (a low-nutrient density diet or a normal-nutrient density diet) and 3 FI levels (3, 4 or 5% of BW per d). The experimental period consisted of a 5 d adjustment period, 2 d of feces collection (on d 6 and 7), and 2 d of ileal digesta collection on (d 8 and 9). Chromic oxide was used as an indigestible marker to calculate AID of AA, AID and ATTD of CP, EE, ash, ADF,NDF, carbohydrates (CHO) and GE. The AID of CP (P < 0.05), EE (P < 0.1),ash (P <0.05) and GE (P < 0.1), the ATTD of ash (P < 0.1), and hindgut disappearance of CP(P < 0.05), ash (P < 0.1) and most AA were affected by the interaction of dietary nutrient density and FI level. The AID of CP, and the AID and ATTD of DM, EE,CHO and GE decreased linearly for pigs fed a normal-nutrient density (NND) diet, as FI increased (P < 0.05). Furthermore, the AID of CHO (P <0.1) and NDF (P < 0.05),the ATTD of DM (P < 0.1), and hindgut disappearance of CHO and NDF (P<0.1)were influenced by FI. When pigs were fed the NND diet, the AID of most AA decreased (linear, P < 0.05) with increasing FI. However, there were no linear or quadratic effects of FI levels on the AID, ATTD and hindgut disappearance of DM, CP,EE, CHO, NDF, ADF and GE, and AID of most AA for pigs fed the low-nutrient density diet. In summary, the AID and ATTD of nutrients and GE response of growing pigs to FI levels are dependent on dietary nutrients density. The AID and ATTD of nutrients and GE decreased for pigs fed the NND diet as FI increased.The objective of Exp. 2 was to study the effects of meal frequency on AID and ATTD of nutrients and GE. A total of 24 growing pigs (initial BW,35.0 ± 1.1 kg)were surgically fitted with simple T-cannulas at the distal ileum and assigned to 2 treatments (M2 or M12) with 12 replicates per treatment group. Pigs in the M2 and M12 treatments were fed twice and 12 times per day,respectively. The daily feed intake of each pig was calculated according to 5% of their initial BW. The experimental period consisted of a 5 d adjustment period, 2 d of feces collection (on d 6 and 7), and 2 d of ileal digesta collection on (d 8 and 9). Chromic oxide was used as an indigestible marker to calculate AID and ATTD of CP, EE, ash, ADF, NDF, CHO and GE. The results showed that meal frequency had no effects on ADFI, ADG amd feed efficiency of pigs (P > 0.1). The AID of DM, CP, EE, ash, CHO, NDF, ADF and GE were not influenced by meal frequency (P >0.1). Pigs fed twice daily had lower ATTD of DM (P < 0.05), CP (P < 0.1), EE (P < 0.05), ash (P < 0.05), DNF (P < 0.05),ADF (P < 0.1) and GE (P < 0.05) than that in pigs fed 12 times per day. The hindgut disappearance of EE (P < 0.05), NDF (P < 0.01), ADF (P < 0.05) and GE (P < 0.1)were lower for M2 pigs compared with M12 pigs. In summary, meal frequency has no effects on the AID of nutrients and GE in pigs fed a corn-soybean meal-based diet.However, the ATTD and hindgut disappearance of nutrients and GE increase with increasing meal frequency.The objective of Exp. 3 was to investigate the effects of meal frequency on the levels of metabolites in plasma and hepatic proteome of pigs by isobaric tags for relative and absolute quantitation (iTRAQ) analysis. Twenty-four pigs (60.7±1.0 kg)consumed the same amount of feed either in 2 (M2, n=12) or 12 (M12, n = 12) meals per day. After an 8-week feeding period, plasma concentrations of metabolites and hormones, hepatic biochemical traits and proteome were measured. Pigs on M12 regimen had lower average daily gain and gain-to-feed ratio than pigs fed M2 regimen(P < 0.05). M2 regimen resulted in lower total lipid, glycogen and triglyceride contents in liver and circulating triglyceride concentration than that in M12 pigs (P <0.05). The metabolic hormone concentrations were not affected by meal frequency with the exception of elevated fibroblast growth factor 21 (FGF21) concentrations in M2 regimen compared with M12 regimen (P < 0.05). The iTRAQ-based proteomic analysis revealed 35 differentially expressed proteins in the liver between pigs fed 2 and 12 meals per day (P < 0.05), and these differentially expressed proteins were involved in the regulation of general biological process such as glucose and energy metabolism, lipid metabolism, protein and amino acid metabolism, stress response and cell redox homeostasis. Altogether, meal frequency affects the process of glucose and lipid metabolism in pigs.