Growth Performance, Digesta pH and Organ Weight of Weaned Pigs Fed Barley Grain Differing in Fermentable Starch

Published: March 9, 2023

By: J. Sanchez 1, L.F. Wang 1, E. Beltranena 1, A.D. Beattie 2, R.W. Newkirk 2, R.T. Zijlstra 1 / 1 University of Alberta, Edmonton, AB; 2 University of Saskatchewan, Saskatoon, SK.

Summary

Barley grain is underutilised as net energy (NE) source for weaned pigs. Whether fermentable starch and fibre in barley or reduced diet NE value would affect growth performance, digesta pH or organ weight in weaned pigs is unclear. Five diets contained 60−70% cereal grain: 1) lowfermentable wheat (LFW); 2) low-fermentable hulled barley (LFB); 3) LFB, without added oil, low NE (LFB-LNE); 4) high β-glucan, hull-less barley (HFBB); or 5) high amylose, hull-less barley (HFAB). Diets provided 2.45 and 2.33 Mcal NE/kg (2.25 and 2.19 for LFB-LNE), and 5.51 and 5.10 g standardised ileal digestible (SID) lysine/Mcal NE (6.01 and 5.45 for LFB-LNE) for phase 1 (day 1–14) and phase 2 (day 15–28), respectively. Forty pigs (8.6 kg) were fed 1 of 5 diets starting 1-week post-weaning. Overall, average daily feed intake (ADFI), average daily gain (ADG) and gain:feed (G:F) did not differ among diets formulated to equal NE and SID lysine/NE ratio. For day 15–21, ADG and G:F was greater (P < 0.05) for LFB than HFBB. Feces consistency, digesta pH and weights of kidneys, liver, spleen, carcass, non-carcass, and empty body weight (EBW) did not differ among pigs fed the 4 diets. The EBW (% of live BW) was 2.1% lower (P < 0.05) for pigs fed HFBB than pigs fed LFB and LFW. Empty colon and rectum weight (% of EBW) increased (P < 0.05) by 25% in pigs fed HFAB than pigs fed LFW and LFB. Empty cecum weight (% of EBW) increased (P < 0.05) by 27% in pigs fed HFBB than pigs fed LFB and LFW. Comparing LFB with LFB-LNE, low dietary NE value did not affect ADFI, ADG and G:F for the entire trial, but ADG was greater (P < 0.05) for LFB-LNE than LFB for day 1–7. Feces consistency, digesta pH, organ weights, carcass, non-carcass and EBW did not differ between pigs fed LFB and LFB-LNE. In conclusion, dietary fermentable starch and fibre did not affect growth, feces consistency and carcass weight in weaned pigs. High dietary fermentable carbohydrates may reduce EBW and increase large intestine weight. Reducing NE value of a hulled barley diet while maintaining SID AA content did not affect growth, EBW and organ weights. Dietary inclusion of barley grain and formulating low NE diets may reduce feed cost without affecting growth or carcass weight in weaned pigs.

Keywords: barley, fibre, pig, starch

Introduction

In Canada, barley is rarely fed to young pigs due to its relatively high fibre content that is associated with lower energy and nutrient digestibility (Che et al., 2012). Carbohydrates that are not digested in the small intestine may be fermented in the large intestine, and so provide energy and stimulate gut health (Fouhse et al., 2017). Barley cultivars with increased fermentable carbohydrates may enhance gut health in weaned pigs (Jha et al., 2019). Intestinal populations of Bifidobacteria spp. and Lactobacillus spp were increased in weaned pigs consuming 63% of dietary starch as amylose or barley-based diets (Fouhse et al., 2015). Moreover, fermentable carbohydrates may repress pathogen colonisation and enhance immune responses and gut function (Diao et al., 2019). However, fermentable carbohydrates may also alter the physicochemical properties of digesta, predisposing pigs to diarrhoea (Pluske et al., 2002). High-fibre diets may increase the mass of undigested residue flowing into the gut and increase mass of the gastrointestinal tract (GIT) (Agyekum and Nyachoti, 2017). The enlarged GIT would exert additional energy and nutrient demand to meet their increased maintenance costs (Nyachoti et al., 2000). The increase in energy expenditure is likely associated with increased protein synthesis and increased endogenous losses in the GIT when pigs are fed high-fibre diets (Jørgensen et al., 1996) and that may decrease amino acid availability for growth. Hence, research is required to validate the inclusion of barley high in fermentable starch and β-glucan in weaned pig diets and characterize its nutritive and functional value. Thus, the objective of this study was to evaluate growth performance, faeces consistency, digesta pH, and physical body composition of weaned pigs fed diets differing in fermentable carbohydrates content.

Methodology

Forty crossbred barrows and gilts (28 ± 1 days of age, 8.6 kg) were blocked based on gender and randomly assigned to individual metabolism pens (1.1 × 0.8 m). Pigs were allocated to 1 of 5 test diets in randomized complete blocks. Test diets contained 60−70% cereal grain: 1) low-fermentable wheat (LFW); 2) low-fermentable hulled barley (LFB); 3) LFB, without added oil, low NE (LFB-LNE); 4) high β-glucan, hull-less barley (HFBB); or 5) high amylose, hull-less barley (HFAB). Diets provided 2.45 and 2.33 Mcal NE/kg (2.25 and 2.19 for LFB-LNE), and 5.51 and 5.10 g standardised ileal digestible (SID) lysine/Mcal NE (6.01 and 5.45 for LFB-LNE) for phase 1 (day 0–14) and phase 2 (day 15–28), respectively. Test diets were fed ad libitum starting from 1 week after weaning. Pigs, added and remaining feed were weighed weekly to calculate average daily feed intake (ADFI), average daily gain (ADG) and gain-to-feed (G:F). Faeces consistency was recorded daily using an 8-grade score. Pigs were slaughtered at the conclusion of the study and emptied GIT, liver, spleen, kidneys, and blood were weighed. Digesta pH was measured in all GIT segments. Organs and blood were referred to as “non-carcass”, whereas carcass including head and feet were referred to as “carcass.” The empty BW (EBW) of the pig was the sum of carcass and non-carcass. Data were analysed using the GLIMMIX procedure (SAS Inst. Inc., Cary, NC). For growth performance and faeces consistency data the model included week and interaction of diet and week as fixed effects and block as random effect. Digesta pH and physical body composition data were analyzed with digesta temperature and initial BW as a covariate, respectively. A probability of P < 0.05 was considered significant.

Results and Discussion

For the 28-day trial, ADFI, ADG, G:F and faeces consistency did not differ among pigs fed diets formulated to equal NE and SID lysine/NE ratio. For individual weeks, ADG and G:F was greater (P < 0.05) for pigs fed LFB than for pigs fed HFBB for day 25–21. Fibre and fermentable carbohydrates content are negatively correlated with nutrient digestibility and energy value of feed (Le Goff et al., 2002) and may reduce pig growth (Che et al., 2012). Despite greater dietary fibre and fermentable carbohydrates content, pigs fed the barley diets had equal growth performance than pigs fed wheat diet in the present study. The sustained growth may be partly attributed to diets formulated to equal NE and SID AA, which reduces risks associated with feeding ingredients high in fibre on pig performance. Feeding increasing fibre and fermentable carbohydrates may increase visceral organ weight and gut fill which contributes to live BW gain (Agyekum et al., 2012). Additionally, fibre and fermentable carbohydrates in barley may maintain gut health and growth performance (Molist et al., 2014). Comparing LFB with LFB-LNE, addition of dietary oil for NE correction did not increase growth performance in pigs. Pigs fed LFB-LNE did not increased feed intake to compensate for reduced dietary value, indicating that young pigs can efficiently utilize barley grain to support growth.

Live BW at slaughter was 25.2, 26.9, 27.2, 25.0 and 25.6 kg for LFW, LFB, LFB-LNE, HFBB and HFAB diets, respectively, and did not differ among diets. Digesta pH and weights of kidneys, liver, spleen, carcass, non-carcass and EBW did not differ among pigs fed diets formulated to equal NE and SID lysine/NE ratio. However, EBW expressed as percentage of live BW was 2.1% lower (P < 0.05) for pigs fed HFBB than pigs fed LFB and LFW. Empty colon and rectum weight as percentage of EBW increased (P < 0.05) by 25% in pigs fed HFAB than pigs fed LFW and LFB, whereas empty cecum weight as percentage of EBW increased (P < 0.05) by 27% in pigs fed HFBB than pigs fed LFB and LFW. Although treatment did not affect live BW, carcass and non-carcass, pigs fed HFBB had a lower EBW as percentage of live BW than pigs fed LFW and LFB, indicating that high β-glucan may enlarge gut fill by decreasing passage rate and reducing nutrient digestion, thereby increasing the mass of undigested residue (Fouhse et al., 2017). The heavier large intestine as percentage of EBW in pigs fed high β-glucan and high amylose diets than pigs fed low fermentable wheat and hulled barley might be due to increased nutrient fermentation, resulting in adaptive changes in the size of the GIT (Fouhse et al., 2017). Digesta pH, organ weights, carcass, non-carcass and EBW did not differ between pigs fed LFB and LFB-LNE.

Conclusion

Dietary inclusion of barley grain to replace wheat did not affect ADFI, ADG, G:F, faeces consistency, and carcass weight in weaned pigs. Fermentable carbohydrates in barley reduced EBW and increased large intestine weight. Reducing dietary NE value while keeping SID AA content did not affect growth performance, EBW and organ weights in weaned pigs. Barley grain can be fed as energy source to starter pigs. Formulating low NE diets may reduce feed cost without affecting growth performance or carcass weight in weaned pigs.

Presented at the 2022 Animal Nutrition Conference of Canada. For information on the next edition, click here.

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