A 2 £ 2 factorial experiment was conducted to investigate the interactions between laminarin (LAM; 0 and 300 parts per million (ppm)) and fucoidan (FUC; 0 and 240 ppm) levels on intestinal morphology, selected microbiota and inflammatory cytokine gene expression in the weaned pig. There was an interaction between LAM and FUC supplementation on the Enterobacteriaceae population (P,0·05) and the abundance of attaching and effacing Escherichia coli (AEEC) strains (P, 0·05) in the colon. Pigs offered the FUC diet had a reduced Enterobacteriaceae population compared with pigs offered the basal diet. However, the effect of FUC on the Enterobacteriaceae population was not observed when combined with LAM. Pigs offered the LAM diet had reduced abundance of AEEC strains compared with pigs offered the basal diet. However, there was no effect of LAM on the abundance of AEEC strains when combined with FUC. There was an interaction between LAM and FUC supplementation on villous height (P,0·01) and the villous height:crypt depth ratio (P,0·01) in the duodenum. Pigs offered the LAM or FUC diet had an increased villous height and villous height:crypt depth ratio compared with pigs offered the basal diet. However, there was no effect of the LAM and FUC combination diet on intestinal morphology. Pigs offered the LAM-supplemented diets had a lower IL-6 (P, 0·05), IL-17A (P, 0·01) and IL-1b (P,0·01) mRNA expression in the colon compared with pigs offered the diets without LAM. In conclusion, supplementation with either LAM or FUC alone modified intestinal morphology and selected intestinal microbiota, but these effects were lost when offered in combination.

In the present study, two experiments were conducted to (1) evaluate the effect of laminarin and/or fucoidan on ileal morphology, nutrient transporter gene expression and coefficient of total tract apparent digestibility (CTTAD) of nutrients and (2) determine whether laminarin inclusion could be used as an alternative to ZnO supplementation in weaned pig diets. Expt 1 was designed as a 2 £ 2 factorial arrangement, comprising four dietary treatments (n 7 replicates, weaning age 24 d, live weight 6·9 kg). The dietary treatments were as follows: (1) basal diet; (2) basal diet þ 300 ppm laminarin; (3) basal diet þ 240 ppm fucoidan; (4) basal diet þ 300 ppm laminarin and 240 ppm fucoidan. There was an interaction between laminarin and fucoidan on the CTTAD of gross energy (GE) (P,0·05) and the expression of sodium -glucose-linked transporter 1 (SGLT1/SLC5A1) and GLUT1/SLC2A1 and GLUT2/SLC2A2 (P,0·05) in the ileum. The laminarin diet increased the CTTAD of GE and increased the expression of SGLT1, GLUT1 and GLUT2 compared with the basal diet. However, there was no effect of laminarin supplementation on these variables when combined with fucoidan. Expt 2 was designed as a complete randomised design (n 8 replicates/ treatment, weaning age 24 d, live weight 7·0 kg), and the treatments were (1) basal diet, (2) basal diet and laminarin (300 ppm), and (3) basal diet and ZnO (3100 ppm, 0-14 d, and 2600 ppm, 15-32 d post-weaning). The laminarin diet increased average daily gain and gain: feed ratio compared with the basal diet during days 0 -32 post-weaning (P,0·01) and had an effect similar to the ZnO diet. These results demonstrate that laminarin provides a dietary means to improve gut health and growth performance post-weaning.

Feed efficiency is an important trait in pig production, with evidence to suggest that the efficiencies of a variety of biological systems contribute to variation in this trait. Little work has been conducted on the contribution of the intestinal innate immune response to divergence in feed efficiency. Hence, the objective of this study was to examine select bacterial populations and gene expression profiles of a range of targets relating to gut health and immunity in the intestine of pigs phenotypically divergent in feed efficiency in: a) the basal state; and (b) following an ex-vivo lipopolysaccharide (LPS) challenge of ileal and colonic tissue. Male pigs (initial BW 22.4 kg (SD = 2.03)) were fed a standard finishing diet for the final 43 days prior to slaughter to evaluate feed intake and growth for the purpose of calculating residual feed intake (RFI). On day 115, 16 animals (average weight 85 kg, SEM 2.8 kg), designated high RFI (HRFI) and low RFI (LRFI) were slaughtered. The LRFI pigs had increased lactobacillus spp. in the caecum compared to HRFI pigs (P < 0.05). RFI groups did not differ in the expression of the measured genes involved in the innate immune system in the basal ileal or colonic tissues (P > 0.10). Interestingly, there was an interaction between RFI and LPS for the cytokines IL-8, IL-1, IL-6, TNF-α, Interferon-γ (IFN-γ) and SOCS3, with the LRFI group having consistently lower gene expression in the colon following the LPS challenge, compared to the HRFI group. The lower gene expression of SOCS and cytokines following an ex vivo LPS challenge supports the theory that a possible energy saving mechanism exists in the intestinal innate immune response to an immune challenge in more feed efficient pigs.

Feed efficiency is an important trait in the future sustainability of pig production, however, the mechanisms involved are not fully elucidated. The objective of this study was to examine nutrient digestibility, organ weights, select bacterial populations, volatile fatty acids (VFA's), enzyme and intestinal nutrient transporter gene expression in a pig population divergent in feed efficiency. Male pigs (n = 75; initial BW 22.4 kg SEM 2.03 kg) were fed a standard finishing diet for 43 days before slaughter to evaluate feed intake and growth for the purpose of calculating residual feed intake (RFI). Phenotypic RFI was calculated as the residuals from a regression model regressing average daily feed intake (ADFI) on average daily gain (ADG) and midtest BW 0.60 (MBW). On day 115, 16 pigs (85 kg SEM 2.8 kg), designated as high RFI (HRFI) and low RFI (LRFI) were slaughtered and digesta was collected to calculate the coefficient of apparent ileal digestibility (CAID), total tract nutrient digestibility (CATTD), microbial populations and VFA's. Intestinal tissue was collected to examine intestinal nutrient transporter and enzyme gene expression. The LRFI pigs had lower ADFI ( P < 0.001), improved feed conversion ratio ( P < 0.001) and an improved RFI value relative to HRFI pigs (0.19 v. −0.14 SEM 0.08; P < 0.001). The LRFI pigs had an increased CAID of gross energy (GE), and an improved CATTD of GE, nitrogen and dry matter compared to HRFI pigs ( P < 0.05). The LRFI pigs had higher relative gene expression levels of fatty acid binding transporter 2 ( FABP2) ( P < 0.01), the sodium/glucose co-transporter 1 ( SGLT1) ( P < 0.05), the glucose transporter GLUT2 ( P < 0.10), and the enzyme sucrase-isomaltase (SI) ( P < 0.05) in the jejunum. The LRFI pigs had increased populations of lactobacillus spp. in the caecum compared with HRFI pigs. In colonic digesta HRFI pigs had increased acetic acid concentrations ( P < 0.05). Differences in nutrient digestibility, intestinal microbial populations and gene expression levels of intestinal nutrient transporters could contribute to the biological processes responsible for feed efficiency in pigs.

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