GROWTH PERFORMANCE AND GUT PROMOTING ACTIVITY OF THREE CONVENTIONAL FIBRE FEEDSTUFFS IN DIETS OF GROWING PIGS † [GANANCIA DE PESO Y ACTIVIDAD PROMOTORA A NIVEL INTESTINAL DE TRES ALIMENTOS FIBROSOS CONVENCIONALES EN DIETAS DE CERDOS EN CRECIMIENTO]

Background. The increasing utilisation of fibre feedstuffs in diets of pigs nowadays calls for concerns not only on the growth but also the health status of the animals and the possibility to eradicate the use of in-feed antibiotics for pigs. Objective. To evaluate the growth performance and gut promoting activity of three fibre feedstuffs (Palm kernel cake (PKC), Brewers’ dried grain (BDG) and Wheat offal (WO)) in diets of growing pigs. Methodology. Three dietary treatments containing 40 % each of PKC, BDG and WO were randomly allotted to 24 growing crossbred (Large White x Hampshire) pigs of average initial weight of 30± 0.50 Kg in an 82 d feeding trial. Results. There was an influence (p<0.05) of sources of fibre feedstuffs for the arabinoxylanand mannanoligosaccharide concentrations of the dietary treatments with BDG having comparatively higher values than WO and PKC diets. The short-chain fatty acid (SCFA) concentrations and pH of gut digesta were different (p<0.05) across dietary groups with pigs fed BDG diet having higher SCFA concentration in the foregut and hindgut. In the gut flora, BDG and WO promoted the highest (p<0.05) Lactobacillus population in the small and large intestines respectively. There were significant (p<0.05) effects of fibre sources on the final weight, average daily gain and daily intake of pigs fed the different treatments with those fed WO diets showing superior performance over pigs fed either PKC or BDG diet. Implication. The WO diet promoted the fastest growth and better gut effects but BDG resulted in the most efficient feed to gain conversion. Conclusion. All the diets exhibited prebiotic activity, enhanced the growth of beneficial bacterial in the gut and could reduce the use of in-feed antibiotics for pigs.


INTRODUCTION
The spike in global food-feed prices occasioned by the competition between human and livestock especially the bulk feeders such as pigs and poultry for available cereal gains has consistently generated increasing attention of global debate on how to feed the world 9.2 billion population by 2050 (FAO, 2009;Tian et al., 2021).At the same time, livestock production continues to grow in developing nations amidst changing climate (van Zanten et al., 2016;Kang et al., 2017;Kawabata et al., 2020), further increasing pressure on production resources (land and water).One of the suitable pathways to resolve this challenge is the use of agro-industrial byproducts (AIBPs).
In the last two decades, there is continuous interest in the use of AIBPs as feedstuffs in the diets of pigs despite high fibre levels.The sustained interest may be due to its relatively cheap cost, eco-friendly and contributions to development of circular economy (Murray et al., 2017;Toop et al., 2017;Diluccia et al., 2020).On the bases of availability and cost, palm kernel cake (PKC), brewers' dried grains (BDG) and wheat offal (WO) are the AIBPs most investigated by Nigerian pig nutritionists.Evidence from these studies showed variability in nutrient composition, impaired nutrient digestion, inferior growth performance and recently possible prebiotic effects (Amaefule et al., 2009;Akinfala et al., 2014;Akinfala et al., 2017;Ogunjobi et al., 2021).Meanwhile, fibre inclusion in diets of pigs could improve health, reduce cost of production and use of in-feed antibiotics (Jha et al., 2019;Ogunjobi et al., 2021).Nonetheless, its utilization by pigs is variable and depends on inclusion levels, sources and type, processing techniques and the peculiar attributes of the fibre.
To a large extent, fibre feedstuffs are not wholly degraded by endogenous enzymes of the small intestine, but are partially fermented by gut microbiota in the colon of pigs to produce short-chain fatty acids (SCFA) (Hu et al., 2020).Findings have shown that SCFA has important physiological functions including improving the gastrointestinal motility associated with host health by selectively stimulating the growth and activity of the beneficial microbiota (Flint et al., 2012;Koh et al., 2016;Gensollen et al., 2016;Liu et al., 2018).The gut promoting attribute of fibre depends on the extent of fermentation and degradation in the gut, the intensity of microbial balance and structure (Natividad and Verdu, 2013;B äumler and Sperandio, 2016;Ogunjobi et al., 2021;Bai et al., 2022).Earlier studies by Ogunjobi et al. (2021) documented the prebiotic activity of conventional fibre feedstuffs for growing pigs with peculiar conditions for inclusion in diets of pigs.Prior to this, there is a growing interest in the fate of different dietary fibre especially with respect to changes in gut microbiota and rate of fermentation in pigs (Feng et al., 2018;Wang et al., 2019).Understanding the gut modulation and performance of different dietary fibre in practical diets for pigs could provide more information for the formulation of functional feeds devoid of antibiotic growth promoter.The study aimed at evaluating the growth performance and gut promoting activity of three conventional fibre feedstuffs in diets of growing pigs.

Experimental location and collection of test ingredients
The study was carried out at the Swine Unit of the Teaching and Research Farm, Obafemi Awolowo University (OAU), Ile-Ife, Nigeria.The OAU lies on Latitude 7 0 28 ' N and Longitude 4 0 33'E with an altitude of about 244m above sea level.The test ingredients (palm kernel cake (PKC), brewers' dried grain (BDG) and wheat offal (WO)) were purchased from a commercial feed mill in Ile-Ife, Osun State, Nigeria.

Experimental diets, animals and management
Three experimental diets were formulated using National Research Council (2012) recommendation as guide.Each of the dietary treatments (PKC, BDG and WO) contained 40% PKC, BDG and WO respectively, and were randomly allocated to 12 experimental pens.The composition of experimental diets is shown in Table 1.Twenty-four growing cross bred (Large White x Hampshire) pigs of average initial weight 30±0.50 kg were used in 84-d feeding trial.For each treatment, there were eight animals arranged in two animals per pen on the basis of sex in a completely randomized design (CRD).The animals were weighed at the beginning of the experiment, and thereafter, weekly throughout the experimental period.Feed and water were given ad libitum and routine management practices was carried out on the experimental pigs on treatment basis.Daily feed allocation and intake was measured while daily weight gain and feed efficiency ratio were evaluated.

Slaughtering procedures and collection of digesta from the gut
All experimental research procedures conformed with the institutional, national and international guidelines were approved by the Animal Welfare Committee of the Obafemi Awolowo University, Ile-Ife.At the end of the 84 th day of feeding, six experimental pigs per treatment were randomly selected, labelled and humanely slaughtered according to the procedure outlined by Close et al. (1997).The collection of digesta from both the small and large intestines for the determination of bacterial profile (total heterotrophic bacteria count, Lactobacillus count and total coliform count) was carried out by adopting the pour plate techniques.The pH was determined with the aid of a pH meter while short chain fatty acids (SCFAs) were determined using spectrophotometric method following the procedure of Kayol and Borilek (1995).

Data analysis
Data were subjected to Analysis of Variance (ANOVA) using the General Linear Model (GLM) procedure of SAS (2009) based on the following statistical model: in which Y is the dependent variable; i is for diets PKC, BDG or WO; j is for replicates 1, 2, 3, or 4; μ is the overall/group mean, Ti is the treatment effect of i th diets; and e is the random error associated with completely randomized design.Standard error of the mean is for n = 4 and Duncan Multiple Range Test was used to separate means at 5% level of significance.

RESULTS
The oligosaccharide, proximate and cell wall composition of fibre feedstuffs is shown in Table 2.The arabinoxylan-and mannan-oligosaccharide contents of the fibre feedstuffs had significant difference (p<0.05)across treatment groups.The WO diet had the highest arabinoxylanoligosaccharide content while PKC and BDG were 22% and 52% lower.On the other hand, BDG diet gave the better mannan-oligosaccharide content compared to WO and PKC which were 44% and 56% inferior.
There existed significant variations (p<0.05) in the proximate (CF, ash and NFE) composition of the different fibre feedstuffs.Higher values were obtained in BDG diet for the CF (7.23%) and ash (8.72%) contents while PKC had the least values (5.39% and 5.14%) respectively.The NFE values also varied between 56.5% and 49.49% for WO and BDG diets respectively.All the different fibre feedstuffs had significant variations (p<0.05) in the values obtained for the different cell wall components except the cellulose content.Higher values were found in PKC diets while the least values were obtained in WO.
Table 3 show the effects of different sources of fibre diets on digesta pH and short chain fatty acid (SCFA) profile in the gut of growing pigs.The different fibre sources had significant effects (p<0.05) on the digesta pH measured in the small and large intestines of growing pigs.Higher pH values (7.08 and 6.48) were found in the digesta of pigs fed BDG diet in both the small and large intestines while those fed PKC had the least pH values (6.08 and 5.49) in both regions of the gut.
Similarly, all the SCFA components were significantly different (p<0.05) for all treatment groups in the small and large intestines of pigs fed fibre diets.The pigs fed BDG diet produced significantly (p<0.05)higher values for the different SCFAs (acetic, propionic and butyric acids) and the total SCFA concentrations in the small and large intestines.On the other hand, the digesta from pigs fed PKC diet gave comparatively lower values for individual and total SCFA concentrations.
Table 4 shows the bacterial population in the gut of growing pigs fed fibre diets.The total aerobe count obtained from the digesta in the small intestine of pigs fed fibre diets had significant (p<0.05)variations, which is associated with fibre source.The highest value was found in pigs fed WO diet while those fed PKC and BDG diets were 30% and 88% lower.Contrarily, the total lactic acid bacteria population in the digesta of pigs fed BDG was comparatively higher (p<0.05)than those fed PKC and WO, which were -24% and -99% respectively.
In the large intestine, there was significantly (p<0.05)higher total aerobe in the digesta of pigs fed BDG than either of those fed WO or PKC.The WO fed pigs promoted the highest total lactic acid bacteria population while PKC performed the poorest.The total coliform count was significantly (p<0.05)higher in the digesta of pigs fed BDG diet while those fed PKC had the least population (2.75 x10 4 CFU/g digesta).
The performance of growing pigs fed experimental diets is shown in Table 5.There were significant differences (p<0.05) in the final weight (FW), average daily gain (ADG) and daily feed intake (DFI) of pigs fed the different fibre diets.The final weight of pigs fed experimental diets increased across treatment groups from those fed PKC diet to WO.The heaviest (63.25 kg) and lightest (55.50 kg) pigs were found in WO and PKC diets respectively.The WO fibre diet promoted the fastest growth (63.25 kg), ADG (397 g/d) and highest DFI (1.50 kg/pig/d) while those on PKC diet had the poorest FW (55.50 kg), ADG (299 g/d) and least DFI (1.13 kg/pig/d).Pigs on BDG diet were the most efficient feed converter compared with those on PKC and WO diets.

DISCUSSION
Fibre feedstuffs particularly WO, BDG and PKC have been studied for their high contents of nondigestible oligosaccharides especially the arabinoxylan and mannan (Jay et al., 2008;Iyayi and Adeola, 2015;Rajendran et al., 2017).Iyayi (2008) reported 63.4% of NSP in WO as arabinoxylan, findings by Jaworski et al. (2015) were consistent with our results while Ogunjobi et al (2021) obtained higher values than those reported in this study.The observed variations in the oligosaccharide contents are possibly due to the differences in diet composition, processing methods, variety and environmental condition.Also, BDG has been reported to contain exceptionally low arabinoxylan due to variations in extent of extraction during the beer-brewing process (Izydorczyk and Dexter, 2008;Lao et al., 2020).
The proximate and cell wall composition of the fibre feedstuffs were within the range observed by Fatufe et al. (2016) and Akinfala et al. (2017) for the proximate parameters.Jaworski et al. (2014); Rhule (2015) and Ogunjobi et al. (2021) reported lower values for the CF, ash, NDF, ADF and lignin contents, while Fatufe et al. (2016) and Ghodrat et al. (2017) obtained higher values.The differences that occurred in the respective cell wall and proximate contents of the different fibre feedstuffs could be due to varietal differences, soil type and the highly fibrous nature of the outer covering of the fibre feedstuffs.
The observed decrease in digesta pH along the gut from the small intestine/foregut to the large intestine/hindgut reflected a positive inverse relationship with short chain fatty acids, which is occasioned by an increase in fibre fermentation.Our results agree with those of earlier studies by Ngoc et al. (2012); Besten et al. (2013); Ndeh and Gilbert (2018); Chen et al. (2019) and Ogunjobi et al. (2021) who found similar trends.Iyayi and Adeola (2015) indicated that the important determinants of the nature and quantity of fermentation products are the type and amount of fibre as well as the available substrate in the fermentation medium.For instance, BDG and WO contain significantly higher mannanoligosaccharide than PKC which are substrate for the production of SCFA (Michlmayr et al. 2013;Rivière et al. 2014;Chen et al. 2019) Also, BDG and WO contain lesser lignin than PKC which are more rapidly fermented in the hindgut than foregut to produce SCFA.The findings of this study agree with the observations of Rodrigues et al. (2017) that the bulk of microbial fermentation and production of SCFA in pig occurs in the hindgut while partial digestion of the components of dietary fibre in the small intestine is solely for production of fermentation substrate.
The type of dietary fibre and its degree of fermentation within the gut could be the causes of the observed variations in gut microbiota.Also, the proportion of fermentable fibre were higher in BDG and WO than in PKC, which not only influenced the concentration of SCFA but also the composition of gut microflora.The results of this study agree with the findings of Zijlstra et al. (2012) The differences in final body weight and daily gains of pigs fed fibre diets are associated with daily intake and digestive efficiency in the use of absorbed nutrients (Sevillano et al., 2018;Deru et al., 2021).This is a possibility for BDG and WO diets containing lesser lignified contents that are more digestible.The daily weight gain reported in the study falls within the range (0.281 to 0.470kg/day/animal) reported by Akinfala et al. (2017) when different fibre feedstuffs were included at 40% in diets of growing pigs.Mwesigwa (2012) and Mukasafari et al. (2017) reported lower range (0.130 to 0.230 kg/d/pig and -0.153 to 0.317 kg/d/pig) in diets for sow and weaner pigs fed brewers' dried grain, and by-products of maizewheat processing respectively.The change in gut microbiota and reduction in intestinal pH could also contribute to improving the activity of digestive enzymes for better nutrient utilisation.This agrees with the findings of the studies by Carre et al. (2008); Sekirov et al. (2010) that dietary fibre improves the activity of gut microbiome for improved nutrient use.However, higher inclusion of dietary fibre contents is related with lower growth performance and feed efficiency in pigs (Quiniou and Noblet, 2012;Sevillano et al., 2018).The reduced performance may be explained by the negative impact of increased fibre content on digestibility of nutrients in growing pigs (Le Gall et al., 2009;Le Goff et al., 2002;Mauch et al., 2018).Our results found similar trend and agrees with the reports of Akinfala et al. (2014); Imonikebe and Kperegbeyi (2014) who observed higher feed conversion ratio for weaner and growing pigs fed different fibre diets.

CONCLUSION
All the fibre feedstuffs (PKC, BDG and WO) contained nondigestible-oligosaccharides, produced short-chain fatty acids and promoted the growth of Lactobacilli in the gut of growing pigs and could eradicate the use of in-feed antibiotics.For better growth performance and gut effect, WO is the suitable fibre feedstuff but BDG diet was the most efficiently used by growing pigs.
;Haenen et al. (2013);Hamaker and Tuncil (2014);Jha et al. (2019);Ogunjobi et al. (2021);Ma et al. (2022) that revealed types and contents of dietary fibre change the species and their abundance in the gut.Also, increased production of butyric acid has inhibition effects on the growth and proliferation of intestinal pathogenic/aerobic bacteria as well as promotes colonization and development of beneficial Lactobacillus species.This was observed in our results of the amount of gut aerobic and Lactobacillus count and supports the earlier findings byMontagne et al. (2010); Gerritsen et al. (2012); Bach Knudsen et al. (2013); Liu et al. (2017); Ogunjobi et al. (2021) that fibre feedstuffs promoted gut health by enhancing the growth and proliferation of beneficial bacterial population in growing pigs.