Liver and skeletal muscle mitochondria proteomes are altered in pigs divergently selected for residual feed intake

Animals selected for residual feed intake (RFI) can be used as a model to elucidate molecular explanations for differences in growth efficiency. The objective of this study was to determine the extent to which the protein profile and posttranslational modifications of mitochondria from skeletal muscle and liver relate to feed efficiency gains in pigs divergently selected for RFI. Mitochondria were isolated from the longissimus dorsi (LD) muscle and the liver from pigs (n = 9 each for the high and low RFI line; BW = 95.8 kg). Mitochondria protein profile differences were determined using two-dimensional difference in gel electrophoresis. Proteins were identified using electrospray ionization mass spectrometry. In the line comparison, the β subunit of ATP synthase, heat shock protein (HSP) 60, and HSP70, were identified as being increased in mitochondria from the liver of the low RFI line (23 to 50%; P \u3c 0.1). These differences were not observed in the other comparisons. In the LD, proteins identified as being different between RFI phenotypes included HSP70 and subunit 1 of the cytochrome bc1 complex. These data indicate that genetic selection for RFI tends to result in a consistent change in mitochondrial protein profile. In contrast, classification by phenotype demonstrates that phenotypic differences in RFI are not specifically associated with alterations of the mitochondria protein profile

Selection for Residual Feed Intake Alters the Protein Profile of the Mitochondria in Pigs

Understanding the biological mechanisms underlying feed efficiency is paramount to creating a more efficient pork production system. Selection for residual feed intake (RFI) is a measure of feed efficiency and can be used as a model to determine these biological mechanisms. The mitochondria are responsible for the conversion of dietary energy to cellular energy in the form of ATP. ATP is used by many biological pathways for both growth and maintenance. These data show the mitochondria protein profile is altered with genetic selection for RFI. This alteration in protein profile indicates mitochondria from more efficient low RFI pigs may be better equipped to handle physiological stress than their less efficient high RFI counterparts. Some of these differences are highlighted in heat shock proteins, and proteins responsible for ATP production. These alterations in the protein profile provide clues for determining the biological differences between pigs genetically selected from low and high RFI

Effect of Selection for Reduced Residual Feed Intake on Pork Carcass Composition and Fresh Pork Quality

Selection for reduced residual feed intake (RFI) resulted in leaner carcasses and less intramuscular lipid in the pork loin. However, the selection approach did not result in differences in water holding capacity and color of fresh pork loin chops. Selection for reduced RFI has the potential to improve carcass composition with few detrimental effects on meat quality

Development of Protein Biomarker Identification Protocols

Protein biomarkers can be used to predict biological traits or diseases. There is a need for robust methods to identify protein biomarkers that are linked to livestock production traits. Serum from blood is often used for detecting and screening for biomarkers. Albumin is a protein that comprises 50% or more of the total content of serum, and has historically been removed from serum before biomarker development and testing. We have shown that it is possible to successfully identify potential biomarkers without albumin removal, thus reducing steps and potentially cost in both development and routine testing phases

Improved nutrient digestibility and retention partially explains feed efficiency gains in pigs selected for low residual feed intake

Residual feed intake (RFI) is a unique measure of feed efficiency (FE) and an alternative to traditional measures. The RFI is defined as the difference between the actual feed intake of a pig and its expected feed intake based on a given amount of growth and backfat. Therefore, selecting pigs with a low RFI (LRFI) results in a more feed-efficient animal for a given rate of growth. Our objective was to determine the extent to which apparent total tract digestibility of nutrients and energy use and retention may explain FE differences between pigs divergently selected for LRFI or high RFI (HRFI). After 7 generations of selection, 12 HRFI and 12 LRFI pigs (62 ± 3 kg BW) were randomly assigned to metabolism crates. Pigs had free access to a standard diet based on corn (Zea mays) and soybean (Glycine max) meal containing 0.4% TiO2, an exogenous digestibility marker. After a 7-d acclimation, total urine and feces were collected for 72 h. Nutrient and energy digestibility, P digestibility, and N balance were then measured and calculated to determine differences between the RFI lines. As expected, ADFI was lower (2.0 vs. 2.6 kg; P \u3c 0.01), ADG did not differ, and FE was higher in the LRFI (P \u3c 0.001) compared to the HRFI pigs. The digestibility values for DM (87.3 vs. 85.9%), N (88.3 vs. 86.1%), and GE (86.9 vs. 85.4%) were higher (P ≤ 0.003) in the LRFI vs. HRFI pigs, respectively. The DE (16.59 vs. 16.32 MJ/kg DM) and ME (15.98 vs. 15.72 MJ/kg DM) values were also greater (P \u3c 0.001) in LRFI pigs. When correcting for ADFI, P digestibility did not differ between the lines. However, the LRFI pigs tended to have improved N retention (P = 0.08) compared to HRFI pigs (36.9 vs. 32.1 g/d). In conclusion, the higher energy and nutrient digestibility, use, and retention may partially explain the superior FE seen in pigs selected for LRFI

Effects of selection for decreased residual feed intake on composition and quality of fresh pork

The objectives of this study were to determine the extent to which selection for decreased residual feed intake (RFI) affects pork composition and quality. Pigs from the fifth generation of selection for decreased RFI (select) and a randomly selected line (control) were utilized. Two experiments were conducted. In Exp. 1, barrows (22.6 ± 3.9 kg) from select and control lines were paired based on age and BW. The test was conducted in 8 replicates of pairs for the test period of 6 wk. Calpastatin activity and myosin isoforms profile were determined on samples from the LM. Control barrows were heavier (59.1 vs. 55.0 kg; P \u3c 0.01) at the end of the test period. Calpastatin activity was greater (P \u3c 0.01) in LM of select barrows than control barrows. In Exp. 2, composition and quality of gilts (114 kg) from control and select lines were determined. The model included fixed effects of line, slaughter date, melanocortin-4 receptor (MC4R) genotype, barn group, line × slaughter date, genotype × line interactions, a covariate of off-test BW, and sire, pen, and litter fitted as random effects. The select line (n = 80) had 0.043 kg less (P \u3c 0.05) RFI per day than the control line (n = 89). Loin quality and composition were determined at 2 d postmortem. Desmin degradation was measured at 2 and 7 d postmortem. Purge, cook loss, sensory traits, and star probe texture were measured at 7 to 10 d postmortem on cooked chops. Residual correlations between RFI and composition and quality traits were calculated. Compared with the control line, carcasses from the select line tended to have less (P = 0.09) backfat, greater (P \u3c 0.05) loin depth, and greater (P \u3c 0.05) fat free lean. Loin chops from the select line had less (P\u3c 0.01) intramuscular lipid content than loin chops from control line. Significant residual correlations between RFI and both tenderness (r = 0.24, P \u3c 0.01) and star probe (r = −0.26, P \u3c 0.01) were identified. Selection for decreased RFI has the potential to improve carcass composition with few effects on pH and water-holding capacity. However, decreased RFI could negatively affect tenderness and texture because of decreased lipid content and decreased postmortem protein degradation

Changes in the Protein Profile of Porcine Liver in Response to Immune System Stimulation

Immune system function has a direct influence on swine growth. Using lipopolysaccharide (LPS) to stimulate the immune system of pigs provides insight on how they handle immunological stress. Several proteins were shown to be part of the liver’s response to LPS. These proteins included heat shock protein (HSP) 60, HSP70, and peroxiredoxin-2. Changes in the abundance of these proteins indicate the extent to which an animal can respond to this immune system stimulation (ISS). Proteins responsible for cellular rescue were found to be increased in abundance in pigs with stimulated immune systems

The Effect of Selection for Residual Feed Intake on General Behavioral Activity in Yorkshire Gilts

The objectives of this study were to determine the effect of selection for reduced residual feed intake (RFI) on behavior and activity in gilts in their home pen. A total of 192 gilts were used, 96 were from a line that had been selected for low residual feed intake over 5 generations (LRFI) and 96 from a randomly bred control line (CRFI). Gilts were housed in 12 pens, containing 8 gilts from each line in a conventional grow-finish unit. Twelve hours of video footage was collected on the day of placement and then every 4 wk for 3 more observational periods. Video was scored using a 10-min instantaneous scan sampling technique. Four postures (standing, lying, sitting and locomotion) and one behavior (at drinker) were collected. Categories of active (standing, locomotion and at drinker) and inactive (sitting and lying) were also created. Analyses were done using Proc Mixed of SAS. There were no differences (P \u3e 0.05) between genetic lines for all postures and the behavior at drinker on the day of placement. However, over subsequent rounds it was observed that LRFI gilts spent less (P = 0.03) time standing, more time sitting (P = 0.05) and were less active (P = 0.03) overall. In conclusion, on the day of placement there were no behavioral differences between genetic lines. Behavioral differences were observed between genetic lines over subsequent rounds, with LRFI gilts becoming less active. Therefore, overall behavioral repertoire of the gilt in their home pen may be beneficial for future RFI selection programs and may contribute to variation in efficiency of the grow-finish gilt

The Effect of Selection for Residual Feed Intake on Lesion Scores in Yorkshire Gilts

The objectives of this study were to determine the effect of selection for reduced residual feed intake (RFI) on lesion scores in gilts in their home pen. A total of 192 gilts were used; 96 were from a line that had been selected for low residual feed intake over 5 generations (LRFI) and 96 from a randomly bred control line (CRFI). Gilts were housed in 12 pens (16 gilts/pen; 0.82 m2 /gilt) containing 8 gilts from each line in a conventional grow-finish unit. Lesion scores were collected the day after placement and every 4 weeks for 3 subsequent periods. The gilt’s body was divided into 4 regions, with each region receiving a score of 0 (0 lesions) to 3 (5+ lesions). All analyses were done using Proc Mixed of SAS. The data were analyzed separately for the day after placement and the subsequent three rounds. Lesion scores for each region of the body were analyzed as repeated measures. Gilts from the LRFI line had lower (P \u3c 0.045) lesion scores on the day after placement. However, over subsequent rounds there were no (P \u3e 0.05) differences between the genetic lines. In conclusion, gilts from the line selected for low RFI had lower lesions scores on the day after placement into the grow-finish environment and this may be a useful tool to use in a selection program for more efficient gilts

Composition and Quality Characteristics of Pigs Selected for Divergent RFI on High or Low Energy Diets

Carcass composition (n= 338) and meat quality (n=151)data were collected on pigs from the eighth generation of the Iowa State University Residual Feed Intake (ISU RFI) selection project fed either high or low energy diets. Both RFI line and diet were found to impact carcass composition, while having minimal effects on pork quality and sensory characteristics. RFI shows promise as a selection tool for improved efficiency without compromising pork quality, even if fed low energy diets