Difference in short-term responses to a high-fiber diet in pigs divergently selected for residual feed intake1

Abstract

Residual feed intake (RFI), defined as the difference between observed and predicted feed intakes, has been explored as a relevant selection criterion to improve feed efficiency in growing pigs. Previous studies exploring the genetic and physiological bases of RFI have been focused on pigs fed a regular diet. The aim of this study was to evaluate the effects of RFI selection on pigs' ability to digest and metabolize a diet enriched in fiber. After 11 wk of age, pigs of 2 lines divergently selected for RFI (low or high; n = 7 pairs of littermates in each line) were fed either a control diet (133 g NDF and 9.69 MJ NE/kg) or a high-fiber diet (244 g NDF and 8.36 MJ NE/kg) for 3 wk. Irrespective of diet, ADFI and water consumption were lower (P < 0.001) in the low RFI line, whereas G:F over the test period was 16% greater (P < 0.001) in that line compared with the high RFI line. There was no line-associated difference in the digestibility of nutrients and energy, despite a lighter digestive tract (-6.4%, P = 0.04) and a lower colon weight (-8.6%, P = 0.03) in the low RFI pigs than in the high RFI pigs. As compared with the control diet, ADFI was reduced (-7.5%, P < 0.001) in both lines when fed a high-fiber diet, but ADG and G:F were lowered for the high RFI line only (P < 0.05). The high-fiber diet decreased (P < 0.01) the digestibility values of nutrients and energy similarly in both lines. However, it increased the ratio of acetate to propionate concentrations in the distal part of the gastrointestinal tract for the high RFI line only (P < 0.07). The pattern of response of plasma metabolites and hormones to a meal test was altered by RFI selection, but it was not affected by the diet. The increase in glucose concentration after meal ingestion was more pronounced (P < 0.05) in the low RFI line, and long-lasting plasma concentrations of lactate tended to be lower (P < 0.10) in the low RFI line than in high RFI line. Plasma NEFA concentrations were greater in that line compared with the high RFI line. The activity levels of catabolic enzymes in muscle and the liver did not differ between lines and diets. In conclusion, the low RFI pigs seem to better utilize a high-fiber diet than high RFI pigs. This was not associated with marked changes in digestion, and the underlying metabolic mechanisms remain to be clarified.

Pigs that are divergent in feed efficiency, differ in intestinal enzyme and nutrient transporter gene expression, nutrient digestibility and microbial activity

“…The RFI value found in this experiment of −140 g/day is in line with previous experiments proving that the pigs in this study are a population of pigs divergent in RFI (Young and Dekkers, 2012). In contrast to previous RFI studies (Young et al, 2011;Mani et al, 2013;Montagne et al, 2014) backfat was not included in the model in this study. However, Do et al (2014) established a correlation coefficient of 0.96 between models with or without backfat, suggesting that the non-inclusion of backfat in this study will not unduly influence the results.…”

“…This is in agreement with work by Harris et al (2012) where LRFI pigs had improved digestibility of DM, N and GE and a tendency towards improved ash digestibility. In contrast, no difference in nutrient digestibility was previously reported between pigs divergently selected for RFI (Montagne et al, 2014). Interestingly while the difference between RFI lines for the CATTD of GE was also seen in the CAID, this difference was not seen in the CAID of N. Similar results were seen in a study by Rakhshandeh et al (2012) where LRFI pigs had improved CATTD with no improvement in CAID.…”

“…In this study HRFI pigs had increased production of acetic acid (P < 0.05) in the colon (Table 4). Previously Montagne et al (2014) found a similar response in relation to total VFA production, with HRFI pigs having increased total VFA production compared to LRFI pigs. Acetate is the principle VFA produced from the fermentation of non-digestible carbohydrates (Bergman, 1990).…”

Effect of inflammation stimulation on energy and nutrient utilization in piglets selected for low and high residual feed intake

“…In the present study, piglets received equal and fixed amounts of feed, which were 30% below the voluntary feed intake capacity of both lines (Table 1). This resulted in similar supplies of digestible protein and energy, because digestibility coefficients were not affected by genetic selection, as confirmed by other observations in these genetic lines of pigs (Barea et al, 2010;Renaudeau et al, 2013;Montagne et al, 2014). The proportion of digested N that was excreted in urine was similar in both lines and the value measured in our experiment was in accordance with previous Table 2 Effect of period of measurement (before or after the complete Freund's adjuvant (CFA) injection) on the energy balance (kJ/kg BW 0.60 per day) in piglets selected for a low or a high residual feed intake (n = 13) 63 ME = metabolizable energy; RHP = resting heat production; TEF s = short-term component of thermic effect of feeding; AHP = activity-related heat production; RFI− = low residual feed intake; RFI+ = high residual feed intake.…”

“…The RE f calculated in our experiment is probably in the upper range of the 'true' RE f of piglets from these two genetic lines. In our study, we also observed a faster utilization of dietary glucose in RFI− than in RFI+ piglets after feeding (measured as the time to recover 50% of 13 C expired as 13 CO 2 , Table 3), which suggests that restoring postprandial blood glycemia or lactatemia may occur faster in RFI− piglets because of increased tissue synthesis, in relation to higher IGF-1 levels (Bunter et al, 2010;Montagne et al, 2014).…”