Effects of pig genotype (Iberian v. Landrace × Large White) on nutrient digestibility, relative organ weight and small intestine structure at two stages of growth

Abstract

Although the effects of pig genotype on total-tract apparent digestibility (TTAD) have been widely reported in the literature, there is controversial information on the digestive capacity of indigenous breeds compared with lean-type pigs. The strategy of this study was to test the effects of pig genotype and crude protein (CP) supply on performance, digestive utilization of nutrients, relative organ weight and morphometric analysis of the small intestine. Thirty-eight Iberian (IB) and Landrace 3 Large White (LD) pigs were used. Three pigs per genotype were slaughtered at approximately 15 kg BW. The remaining pigs were fed one of two diets differing in CP content (13% or 17% as fed) using a pair-fed procedure. Feeding level was restricted at 0.8 3 ad libitum of IB pigs. Nutrient digestibility and nitrogen (N) balance trials were performed at 30 and 80 kg BW. Four pigs per dietary treatment and genotype were slaughtered at approximately 50 and 115 kg BW. The gastrointestinal tract and the rest of the visceral organs were weighed and samples of the small intestine were taken to carry out histological and histometrical studies. Daily gain and gain-to-feed ratio were higher in LD than in IB pigs during the fattening and growing-fattening periods ( P , 0.01). N TTAD was significantly higher for LD pigs at 30 kg BW ( P , 0.05), whereas at 80 kg BW we observed greater values for digestibility of organic matter and energy in IB pigs (averaging 1.5%, P , 0.01). Both N retention (NR) and efficiency of NR were increased in LD pigs at 30 and 80 kg BW (30% as mean value). The proportional weight of the small intestine was greater in LD than in IB pigs at 50 and 115 kg BW. Histometry showed that IB presented a lower muscle layer thickness than LD pigs in ileum, irrespective of the BW ( P , 0.05). In contrast, LD pigs showed approximately 10% higher ileal villi length and villi-to-crypt ratio than IB pigs at 115 kg BW. CP supply affected to a larger extent the small intestinal micro-anatomical structure of LD pigs at 50 kg BW. In conclusion, our results suggests that although the higher growth rate, NR and efficiency of NR observed in LD pigs might be associated with presumably more efficient structural aspects of the small intestine, the main differences between the two genotypes should be attributed to a larger extent to protein and energy utilization in tissues with consequences for the overall efficiency of energy use.

Evolution of the fatty acid profile of subcutaneous back-fat adipose tissue in growing Iberian and Landrace × Large White pigs

“…Average daily feed intake was 2474 and 2600 g/day in LR 3 LW pigs and 2535 and 2515 g/day in IB pigs for LP and HP diets, respectively. However, as reported in our previous paper (Barea et al, 2011), daily gain was higher in LR 3 LW (835 and 847 g/day, respectively for LP and HP diets) than in IB pigs (648 and 573 g/day, respectively for LP and HP diets).…”

“…Part of the experimental design and the experimental diets have been described in detail by Barea et al (2011). Briefly, a total of 38 purebred IB and Landrace 3 Large White (LR 3 LW) barrows (n 5 19 per genotype) were used.…”

“…Four pigs per treatment and genotype were slaughtered by exsanguination after electrical stunning at 50 kg BW, whereas the remaining pigs were kept on the trial until slaughter at 115 kg BW. The pigs slaughtered at different BWs (,15, 50 and 115 kg) were used for determinations of organ weight and micro-anatomical studies of small intestine, as described previously (Barea et al, 2011). Repeated sampling of the back-fat subcutaneous tissue was used to investigate the effects of pig genotype and dietary protein content on the FA profile and evolution of the subcutaneous fat during the growing and finishing stages.…”

“…Chemical analyses Nutrient content of feed samples was determined as described by Barea et al (2011). The FAs of feeds were extracted and quantified by the procedure described by Sukhija and Palmquist (1988).…”

“…It is well known that the efficiency of utilization of dietary protein for body protein deposition is strongly related to pig genotype (Campbell and Taverner, 1988;Rivera-Ferre et al, 2006;Barea et al, 2011). It is accepted that a low dietary CP supply may limit muscle growth so that the dietary energy that would be used for an increased protein synthesis under unrestricted provision of amino acids may be used for fat accretion if the amino acid supply is insufficient.…”