Dietary energy sources affect the partition of body lipids and the hierarchy of energy metabolic pathways in growing pigs differing in feed efficiency1,2

Abstract

The use and partition of feed energy are key elements in productive efficiency of pigs. This study aimed to determine whether dietary energy sources affect the partition of body lipids and tissue biochemical pathways of energy use between pigs differing in feed efficiency. Forty-eight barrows (pure Large White) from two divergent lines selected for residual feed intake (RFI), a measure of feed efficiency, were compared. From 74 d to 132 ± 0.5 d of age, pigs (n = 12 by line and by diet) were offered diets with equal protein and ME contents. A low fat, low fiber diet (LF) based on cereals and a high fat, high fiber diet (HF) where vegetal oils and wheat straw were used to partially substitute cereals, were compared. Irrespective of diet, gain to feed was 10% better (P < 0.001), and carcass yield was greater (+2.3%; P < 0.001) in the low RFI compared with the high RFI line; the most-efficient line was also leaner (+3.2% for loin proportion in the carcass, P < 0.001). In both lines, ADFI and ADG were lower when pigs were fed the HF diet (-12.3% and -15%, respectively, relatively to LF diet; P < 0.001). Feeding the HF diet reduced the perirenal fat weight and backfat proportion in the carcass to the same extent in both lines (-27% on average; P < 0.05). Lipid contents in backfat and LM also declined (-5% and -19%, respectively; P < 0.05) in pigs offered the HF diet. The proportion of saturated fatty acids (FA) was lower, but the percentage of PUFA, especially the EFA C18:2 and C18:3, was greater (P < 0.001) in backfat of HF-fed pigs. In both lines, these changes were associated with a marked decrease (P < 0.001) in the activities of two lipogenic enzymes, the fatty acid synthase (FASN) and the malic enzyme, in backfat. For the high RFI line, the hepatic lipid content was greater (P < 0.05) in pigs fed the HF diet than in pigs fed the LF diet, despite a reduced FASN activity (-32%; P < 0.001). In both lines, the HF diet also led to lower glycogen content (-70%) and lower glucokinase activity (-15%; P < 0.05) in the liver. These results show that dietary energy sources modified the partition of energy between liver, adipose tissue, and muscle in a way that was partly dependent of the genetics for feed efficiency, and changed the activity levels of biochemical pathways involved in lipid and glucose storage in tissues.

NMR-based metabolomics highlights differences in plasma metabolites in pigs exhibiting diet-induced differences in adiposity

“…Within each line, they were randomly assigned to one of the two dietary groups (n = 12 per diet) and fed ad libitum either a low-fat, low-fibre (LF) diet or a high-fat, high-fibre (HF) diet, considering coarsely ground insoluble fibres as a diluent of energy in the HF diet. The HF diet was formulated by the partial replacing of cereals (wheat and barley) in the LF diet by wheat straw (11.5 %) and a mixture of rapeseed and soya oils (7.5 %) [15]. Each diet had the same crude protein and metabolizable energy contents (Table 1).…”

“…The pig lines and feeding trials used in the current study have been previously described [15]. Briefly, a total of 48 purebred French Large White castrated male pigs in the course of a divergent selection experiment for RFI (n = 24 per line) were considered.…”

“…The detailed dietary composition of the diets has been described previously [15] a For each dietary group, the growing diet was distributed to pigs during 6 weeks from 76 days of age, and the finishing diet was distributed thereafter and until slaughter 1 H NMR spectra were acquired at 303 K using the NOESYPR1D (1D nuclear Overhauser effect spectroscopy with water pre-saturation) pulse sequence (RD-90°-t 1 -90°-t m -90°-acquire) with a relaxation delay (RD) of 4 s, a mixing time (t m ) of 150 ms and a fixed t 1 delay of 20 µs. Water suppression was achieved by pre-saturation during the relaxation delay and mixing time.…”

“…The RFI is a measure of feed efficiency that comprises typically the difference between the observed feed intake and the feed intake predicted from growth and maintenance requirements [16]. Irrespective of selection line, pigs fed a high-fat, high-fibre diet had a lower body fat mass when compared with pigs fed an isoenergetic lowfat, low-fibre diet [15]. The current study was undertaken to highlight changes in plasma hormones and metabolites by global and standard biochemical approaches and to determine the relationships between plasma parameters and body adiposity.…”

“…Therefore, investigation of plasma parameters of pigs exhibiting differences in fat deposition may be very helpful in this context. In a recent study, we used an experimental strategy combining genetics and nutrition to induce marked differences in adiposity [15]. This study was based on the use of pigs divergently selected for residual feed intake (RFI) and fed diets with contrasted energy sources and nutrients.…”