The association between faecal host DNA or faecal calprotectin and feed efficiency in pigs fed yeast-enriched protein concentrate

Abstract

Gut cell losses contribute to overall feed efficiency due to the energy requirement for cell replenishment. Intestinal epithelial cells are sloughed into the intestinal lumen as digesta passes through the gastrointestinal tract, where cells are degraded by endonucleases. This leads to fragmented DNA being present in faeces, which may be an indicator of gut cell loss. Therefore, measuring host faecal DNA content could have potential as a non-invasive marker of gut cell loss and result in a novel technique for the assessment of how different feed ingredients impact upon gut health. Faecal calprotectin (CALP) is a marker of intestinal inflammation. This was a pilot study designed to test a methodology for extracting and quantifying DNA from pig faeces, and to assess whether any differences in host faecal DNA and CALP could be detected. An additional aim was to determine whether any differences in the above measures were related to the pig performance response to dietary yeast-enriched protein concentrate (YPC). Newly weaned (∼26.5 days of age) Large White × Landrace × Pietrain piglets (8.37 kg ±1.10, n = 180) were assigned to one of four treatment groups (nine replicates of five pigs), differing in dietary YPC content: 0% (control), 2.5%, 5% and 7.5% (w/w). Pooled faecal samples were collected on days 14 and 28 of the 36-day trial. Deoxyribonucleic acid was extracted and quantitative PCR was used to assess DNA composition. Pig genomic DNA was detected using primers specific for the pig cytochrome b (CYTB) gene, and bacterial DNA was detected using universal 16S primers. A pig CALP ELISA was used to assess gut inflammation. Dietary YPC significantly reduced feed conversion ratio (FCR) from weaning to day 14 (P<0.001), but not from day 14 to day 28 (P = 0.220). Pig faecal CYTB DNA content was significantly (P = 0.008) reduced in YPC-treated pigs, with no effect of time, whereas total faecal bacterial DNA content was unaffected by diet or time (P>0.05). Faecal CALP levels were significantly higher at day 14 compared with day 28, but there was no effect of YPC inclusion and no relationship with FCR. In conclusion, YPC reduced faecal CYTB DNA content and this correlated positively with FCR, but was unrelated to gut inflammation, suggesting that it could be a non-invasive marker of gut cell loss. However, further validation experiments by an independent method are required to verify the origin of pig faecal CYTB DNA as being from sloughed intestinal epithelial cells.

Keywords: cytochrome b; faeces; gut; sloughing; swine.

Figure 1

The effect of an YPC-inclusion diet and when the pig faeces were collected on (a) DNA yield (ng/mg faecal material) and (b) the DNA quality (260 nm/280 nm). Mean values + Standard Error of the Mean, n = 9 for all groups. SEDs for YPC × day interaction=: (a) 7.60 and (b) 0.021. DNA yield was greater at day 14 compared with day 28 (P = 0.016). YPC=yeast-enriched protein concentrate; SED=standard error of the differences of the means.

Figure 2

The effect of an YPC-inclusion diet and when the faeces were collected on faecal (a) pig CYTB DNA content, (b) bacterial 16S DNA content, (c) pig CYTB DNA normalised to bacterial 16S DNA content and (d) pig CALP concentrations (ng/ml). Mean values + SEM, n = 9 for all groups. SEDs for YPC × day interaction=: (a) 0.045, (b) 0.018, (c) 0.445 and (d) 0.600. There were significant effects of diet on both CYTB DNA content (P = 0.008) and CYTB normalised to 16S DNA (P = 0.045), but not 16S DNA content and no significant diet × day interactions or effects of day (P>0.05). See Table 4 for post hoc Bonferroni analyses for effects of diet on CYTB DNA content and CYTB normalised to 16S DNA. Pig CALP concentration was greater at day 14 compared with day 28 (P = 0.009). YPC=yeast-enriched protein concentrate; CYTB=cytochrome b; SED=standard error of the differences of the means; CALP=calprotectin.

Figure 3

(a) The relationship between the pig CYTB DNA content in faeces at day 14 and recorded FCR (weaning to day 14). (b) The relationship between the pig CYTB DNA content in faeces at day 28 with FCR (day 14 to day 28). (c) The relationship between pig faecal CALP concentration (ng/ml) at day 14 and FCR (weaning to day 14). (d) The relationship between pig faecal CALP (ng/ml) at day 28 and FCR (day 14 to day 28). CYTB=cytochrome b; CALP=calprotectin; FCR=feed conversion ratio.