J.C. Kim

Gastrointestinal health and function in weaned pigs: a review of feeding strategies to control post-weaning diarrhoea without using in-feed antimicrobial compounds.

For the last several decades, antimicrobial compounds have been used to promote piglet growth at weaning through the prevention of subclinical and clinical disease. There are, however, increasing concerns in relation to the development of antibiotic-resistant bacterial strains and the potential of these and associated resistance genes to impact on human health. As a consequence, European Union (EU) banned the use of antibiotics as growth promoters in swine and livestock production on 1 January 2006. Furthermore, minerals such as zinc (Zn) and copper (Cu) are not feasible alternatives/replacements to antibiotics because their excretion is a possible threat to the environment. Consequently, there is a need to develop feeding programs to serve as a means for controlling problems associated with the weaning transition without using antimicrobial compounds. This review, therefore, is focused on some of nutritional strategies that are known to improve structure and function of gastrointestinal tract and (or) promote post-weaning growth with special emphasis on probiotics, prebiotics, organic acids, trace minerals and dietary protein source and level.

Feeding a diet with decreased protein content reduces indices of protein fermentation and the incidence of postweaning diarrhea in weaned pigs challenged with an enterotoxigenic strain of Escherichia coli

This study evaluated the effect of feeding low protein (LP) diets for 7 or 14 d after weaning or a high protein (HP) diet for 14 d after weaning on postweaning diarrhea (PWD), indices of protein fermentation, and production in pigs infected or not infected per os with an enterotoxigenic strain of Escherichia coli. A total of 72 female pigs weaned at aged 21 d with initial BW of 5.9 +/- 0.12 kg were used in a 3 x 2 factorial arrangement of treatments. The factors were 3 feeding regimens associated with different combinations of feeding duration and diet CP level: (i) HP diet (256 g of CP/kg) fed for 14 d after weaning, (ii) LP diet (175 g of CP/kg) fed for 7 d after weaning, and (iii) LP diet fed for 14 d after weaning; and infection or noninfection with an enterotoxigenic strain of E. coli (10(7) cfu/mL, serotype O149:K91:K88) at 72, 96, and 120 h after weaning. The LP diets were fortified with crystalline Ile and Val to achieve an ideal AA pattern. A second-stage diet (213 g of CP/kg) was fed to pigs at the conclusion of each feeding regimen, and the study finished 4 wk after weaning. None of the diets contained antimicrobials. Feeding the LP diets decreased (P < 0.001) plasma urea nitrogen, fecal ammonia nitrogen concentrations, and the incidence of PWD, but increased (P = 0.001) fecal DM content compared with pigs fed HP in the 2-wk period after weaning. Infection increased shedding of beta-hemolytic E. coli (P < 0.001), the incidence of PWD (P < 0.001), and fecal ammonia nitrogen concentrations (P < 0.01), but did not interact with feeding regimen, after weaning. Pigs challenged with E. coli grew more slowly (P < 0.001) and had decreased G:F (P < 0.01) compared with nonchallenged pigs in the 4-wk period after weaning. Feeding an LP diet for 7 or 14 d after weaning markedly reduced the incidence of PWD after infection with beta-hemolytic E. coli. Infection was associated with decreased indices of protein fermentation in the distal gastrointestinal tract but did not compromise the growth of weaner pigs in the 4-wk period after weaning.

Effects of feeding low protein diets to piglets on plasma urea nitrogen, faecal ammonia nitrogen, the incidence of diarrhoea and performance after weaning

This study evaluated the effects of feeding pigs low protein (LP) diets for different lengths of time after weaning on indices of protein fermentation, the incidence of post-weaning diarrhoea (PWD), growth performance, and total-tract apparent digestibility. Sixty weaner pigs weighing 6.1 ± 0.13 kg (mean ± SEM) were used in a completely randomised design having five treatments: (i) a high protein diet (HP, 243 g/kg CP) fed for 14 d after weaning (HP14); (ii) a low protein diet (LP, 173 g CP/kg) fed for 5 d after weaning (LP5); (iii) LP diet fed for 7 d after weaning (LP7); (iv) LP diet fed for 10 d after weaning (LP10), and (v) LP diet fed for 14 d after weaning (LP14). All diets were supplemented with lysine, methionine, tryptophan and threonine, with all LP diets additionally fortified with crystalline isoleucine and valine to conform to a proposed ideal amino acid (AA) pattern. A second-stage diet (215 g CP/kg) was fed to pigs at the conclusion of each treatment. None of the diets contained antimicrobial compounds. Feeding a LP diet, regardless of duration of feeding, decreased plasma urea nitrogen (p < 0.001) and faecal ammonia-nitrogen (p < 0.001) contents. Feeding a LP diet, irrespective of feeding duration, decreased the incidence of PWD at day 8 after weaning (p = 0.044), and pigs fed diets LP7, LP10 and LP14 had firmer faeces (p = 0.030, p = 0.047 and p = 0.007, respectively) between days 10 and 12 after weaning. Treatments LP5, LP7, LP10 and LP14 did not reduce (p > 0.05) growth performance up to 106 days after weaning compared to pigs fed the HP diet. Total-tract apparent digestibility of dry matter, energy and crude protein were similar (p > 0.05) between treatments. Our data suggest that feeding a LP diet, supplemented with AA to conform to an ideal AA pattern, for 7–10 days after weaning can reduce PWD in pigs fed antibiotic-free diets without compromising production.

Variation in the chemical composition of wheats grown in Western Australia as influenced by variety, growing region, season, and post-harvest storage

Two experiments were conducted to examine varietal and environmental influences on physical characteristics and chemical content in a cohort of wheats grown in Western Australia. In Expt 1, a 3 × 3 × 2 factorial experiment examined the relationships between wheat variety (Arrino, Stiletto, and Westonia), growing region (high, medium, and low rainfall zone), and 2 harvest years (1999 and 2000). In Expt 2, the effect of storage for 6 months on the chemical composition of the wheats was examined. Wide variations in the content of crude protein (CP, CV 19.4%), total starch (CV 5.45%), total non-starch polysaccharides (NSP, CV 9.4%), insoluble NSP (CV 10.4%), and soluble NSP (CV 20.7%) were observed. The crude protein content of wheat was inversely related to total starch content (r = -0.779, P < 0.001). Variety influenced fast digestible starch (P < 0.001), acid detergent fibre (ADF, P < 0.01), total NSP (P < 0.05), insoluble NSP (P < 0.05), and in vitro extract viscosity (P < 0.05). The annual precipitation level (mm) irrespective of growing region was correlated to bushel weight (r = -0.683, P < 0.01), CP (r = -0.631, P < 0.01), total starch (r = 0.526, P < 0.05), ADF (r = -0.687, P < 0.01), lignin (r = -0.863, P < 0.001), soluble NSP (r = 0.826, P < 0.001), and free sugar contents (r = -0.795, P < 0.001), indicating the importance of annual rainfall for accumulation of protein, carbohydrates, and lignin in wheats. Harvest year had a strong influence on chemical composition (P < 0.05 to <0.001) and bushel weight (P < 0.001) of wheat. Storage for 6 months decreased soluble NSP (P < 0.01), ADF (P < 0.05), and lignin content (P < 0.01), and increased free sugar content (P < 0.001). AR Chepose J. K et al

Addition of oat hulls to an extruded rice-based diet for weaner pigs ameliorates the incidence of diarrhoea and reduces indices of protein fermentation in the gastrointestinal tract

An experiment was conducted to determine whether adding oat hulls to weaner pig diets based on extruded rice or unprocessed wheat influenced post-weaning diarrhoea (PWD) and protein fermentation in the large intestine. Ninety-six male piglets (5.16 (SEM 0.08) kg) were allocated to (i) extruded rice plus animal proteins (RAP); (ii) RAP with added oat hulls (20 g/kg); (iii) wheat plus animal proteins (WAP); (iv) WAP with added oat hulls (20 g/kg). Blood and faecal samples were collected on days 7 and 14 after weaning at about age 21 d. Pigs fed RAP had more PWD than pigs fed WAP (P < 0.05). Oat hull supplementation to diet RAP decreased the incidence of PWD (P < 0.05). The total-tract digestibility of DM, starch and energy was higher in rice-based diets than in wheat-based diets (P < 0.001); however, oat hulls decreased digestibility of DM and gross energy (P < 0.001). Pigs fed RAP had higher plasma creatinine concentrations (P < 0.01), which were positively correlated to cumulative beta-haemolytic Escherichia coli scores after weaning (R2 0.928; P = 0.015). Addition of oat hulls decreased plasma urea concentrations only in pigs fed RAP (interaction; P < 0.05). Pigs fed RAP had lower faecal total biogenic amine concentrations than pigs fed WAP (P < 0.001). Oat hull supplementation tended to decrease total biogenic amine concentrations (P = 0.103). These data indirectly suggest that a mostly insoluble dietary fibre source such as oat hulls can decrease PWD in dietary situations where there may be a misbalance of carbohydrate to protein entering the hindgut.

Non-starch polysaccharides in the diets of young weaned piglets

Carbohydrates comprise between 60% and 80% of the digestible dry matter (DM) in the majority of feedstuff for weaner pigs. The carbohydrate ingested by piglets can be divided into one fraction (starch) that is targeted by the endogenous enzymes of the gastrointestinal tract (a-amylase), and another component (‘dietary fibre’, DF) that is digested predominantly in the terminal ileum and large intestine. The major constituent of DF in diets for young pigs influencing production, gut function and possibly enteric disease susceptibility is derived from non-starch polysaccharides (NSPs). Traditionally the ‘indigestible’ carbohydrate content of foodstuffs has been expressed as ‘crude fibre’, a term that provides no information regarding possible physico-chemical effects of NSP in vivo in the animal or its likely digestibility; simply because it is the residue remaining from extractions of the major plant cell wall components. Non-starch polysaccharides are a large variety of polysaccharide molecules, often in association with phcnolic lignified polymers, protein and starch, that have glucosidic bonds other than the α-(1→4), (1→6) bonds of starch. The building blocks of plant cell wall polysaccharides are the pentoses (arabinose and xylose), hexoses (glucose, galactose and mannose), 6-deoxyhexoses (rhamnose and fucose) and uronic acids (glucuronic and galacturonic acids). These monomers are chemically linked to each other to build various NSPs in the plant cell walls of both cereals and legumes. The major NSPs of plant cell wails, therefore, comprise cellulose (linear β-glucan chains), non-cellulosic polysaccharides (arabinoxylans, mixed-linked β-glucans, mannans, galactans, xyloglucan) and pectic polysaccharides (polygalacturonic acids, which may be substituted with arabinan, galactan and arabinogalactan) (Theander et al, 1989; Lewis, 1993; Bach Knudsen, 1997; Choct, 1997). The NSPs, in turn, can be divided into the ‘soluble’ fraction and the ‘insoluble’ fraction. The term ‘soluble’ refers to solubility in water or weak alkali solutions. It is generally accepted that the large majority of NSPs exhibiting anti-nutritive properties in monogastric animals, or at least the broiler chicken, are water-soluble and give rise to viscous aqueous solutions even when present at relatively low levels (Annison, 1993). The major polysaccharides present in grains and legumes are presented (as average values) in Table 5.1. However, and from a physiological perspective, it is important to consider also the variation that exists within a particular cereal, because this may deter mine some of the physicochemical properties of the grain in vivo that, in turn, are likely to have an effect on digestibility and performance. Further discussion of the implications of this variation will be discussed later in this chapter.

Diets containing inulin but not lupins help to prevent swine dysentery in experimentally challenged pigs

Swine dysentery is a contagious mucohemorrhagic diarrheal disease caused by the intestinal spirochete Brachyspira hyodysenteriae that colonizes and induces inflammation of the cecum and colon. It has been reported that a diet containing chicory root and sweet lupin can prevent swine dysentery. This experiment was conducted to test the hypothesis that inulin in the chicory root rather than galactans in lupins was responsible for protective effects. An experiment with a 2 × 2 factorial arrangement of treatments was undertaken using pigs fed barley- and triticale-based diets, with the main effects being protein source [185 g/kg of canola meal (decreased galactans) or 220 g/kg of lupins (greater galactans)] and inulin supplementation (0 or 80 g/kg). Forty Large White × Landrace pigs weighing 21 ± 3 kg, with 10 pigs per diet, were allowed to adapt to the diets for 2 wk, and then each pig was challenged orally 4 times with a broth culture containing B. hyodysenteriae on consecutive days. Pigs were killed when they showed clinical signs of dysentery or 6 wk postchallenge. Pigs fed diets without inulin had 8.3 times greater risk (P = 0.017) of developing swine dysentery and were 16 times more likely (P = 0.004) to have colon contents that were culture-positive for B. hyodysenteriae, compared with the pigs fed a diet with 80 g/kg of inulin. Diets containing lupins did not prevent pigs from developing clinical swine dysentery; however, inclusion of lupins or inulin or both in the diets delayed the onset of disease compared with the diet based mainly on canola meal (P < 0.05). Diet did not influence the total concentration of organic acids in the ileum, cecum, or upper and lower colon; however, the molar proportions of the organic acids were influenced (P < 0.05). Consequently the pH values in the cecum, and upper and lower colon were not influenced (P > 0.05) by diet. However the pH values of the ileal digesta were decreased in pigs fed the diet with both lupins and inulin compared with the diet containing only lupins (P < 0.05). In conclusion, this study shows that diets supplemented with highly fermentable carbohydrates from inulin protected pigs against developing swine dysentery.

Decreasing dietary particle size of lupins increases apparent ileal amino acid digestibility and alters fermentation characteristics in the gastrointestinal tract of pigs.

Two experiments were conducted to examine the effects of lupin particle size on amino acid (AA) and energy digestibility and fermentation characteristics in pigs. Expt 1 examined the effects of lupin variety (cv. Tanjil and Mandelup) and lupin particle size (746, 888, 1099 and 1136 mum) on the total-tract apparent digestibility of dietary components in 63.5 (sd 7.28) kg pigs. While variety had no effect on total-tract apparent digestibility, decreasing particle size of lupins linearly increased total-tract apparent digestibility of crude protein of diets containing 350 g lupins per kg (P < 0.01). Expt 2 examined the effect of lupin particle size (567, 995, 1198, 1250 and 1304 mum) on digestion and fermentation characteristics in 29.8 (sd 2.9) kg pigs. Pigs were fed the respective diets ad libitum for the first 2 weeks and fed at three times maintenance energy level in the third week. Pigs were euthanised under sedation at 46.7 (sd 4.21) kg to collect digesta samples along the intestinal tract. Decreasing particle size increased apparent ileal and total-tract digestible N (P < 0.01) and the apparent and standardised ileal digestible AA content (P < 0.05- < 0.001) of lupins. Decreasing particle size of lupins linearly decreased the molar proportion of straight-chain volatile fatty acids (sum of acetic, propionic and butyric acids; VFAAPB), while branched-chain fatty acids (sum of valeric, caproic, isobutyric and isovaleric acids) were linearly increased (P < 0.001). The results demonstrated that particle size of lupins is a critical factor influencing nutrient, especially AA, utilisation efficiency and fermentation characteristics in the gastrointestinal tract of pigs.

Levels of total phosphorus, phytate-phosphorus, and phytase activity in three varieties of Western Australian wheats in response to growing region, growing season, and storage

Two experiments were conducted to examine varietal, environmental, and storage influences on total phosphorus (P), phytate-P content, and phytase activity in a cohort of wheats grown in Western Australia. In Expt 1, a 3 x 3 x 2 factorial experiment examined the influence of wheat variety (Arrino, Stiletto, Westonia), growing region (high, medium, low rainfall zone), and harvest year (1999, 2000). In Expt 2, the effect of storage for 6 months on the P composition of the wheats was examined. The total P and phytate-P concentrations ranged from 1.66 to 4.48 g/kg (DM) and from 1.05 to 3.32 g/kg (DM), with mean values of 2.64 (s.e. ±0.142) and 1.79 g/kg (s.e. ±0.127), respectively. Phytase activity ranged from 327 to 811 phytase activity units (FTU)/kg, with a mean value of 563 FTU/kg (s.e. ±29.6). Phytate-P content was significantly correlated with total P concentration (r=0.97, P<0.001). Harvest year tended to influence the total P and phytate-P content (P = 0.079 and P = 0.082, respectively) of the wheats, whereas wheat variety had a significant effect on the phytase activity (P < 0.05). Precipitation level (mm) was positively correlated to total Pand phytate-P contents (P < 0.05). Storage for 6 months after harvest did not change the P content of wheat.

Lupins as a protein source in pig diets

Lupins are a valuable source of protein that can partially replace traditional proteins of animal origin such as meat and bone meal and fish meal. Lupins also have been used as alternatives for soybean meal (SBM) and other oilseed meals in some countries such as Australia and northeastern Europe where use of locally-grown lupins in pig diets is cost-effective. However, the presence of high levels of anti-nutritional factors (ANF), such as non-starch polysaccharides (NSP), oligosaccharides, protease inhibitors, tannins, saponins and alkaloids, have hampered progressive use of lupins in pig diets. Advances in lupin breeding programmes have contributed to the release of varieties with improved digestibility and lower ANF contents. The scope of this review is to evaluate the nutritional value of current varieties of lupins and to summarize recent nutritional concepts covering the strengths and weaknesses of lupins as ingredients in pig diets. The topics discussed will include: (1) chemical characteristics of currently available lupin species; (2) energy and amino acid availability; (3) performance and carcass composition response to lupin-based diets; (4) ANF in lupins; and (5) processing of lupins to improve nutrient digestibility.