Protein profile and reactive oxygen species production in mitochondria from pigs divergently selected for residual feed intake

The world population is expected to hit 9 billion people by the year 2050. The need to efficiently and sustainably produce high quality nutritious food will be a key challenge for producers. Meat is a complete source of protein, B-vitamins, and other macronutrients, and a necessity for a balanced diet [1-2]. As the world population continues to grow and developing countries become more affluent, the demand for meat will increase. In order to efficiently and sustainably produce enough meat to satisfy the demand, research must be conducted to establish the biological differences between animals with differing feed efficiencies. It has long been established that traits such as breed, sex, age, and season (temperature) impact the ability of an animal to efficiently convert dietary energy to metabolic energy (ATP). However, these aforementioned factors do not explain all of the variations in efficiencies. These variations can be partly explained by calculating residual feed intake (RFI). The concept of RFI was developed to account for the difference between actual feed consumption and expected consumption given average daily gain [3] and backfat [4]. A low RFI value would indicate the animal is more efficient in the converting dietary energy to metabolic energy than its contemporaries. Similarly an animal with a high RFI value would consume more than expected based on average daily gain and backfat. To understand and improve efficiency in meat production, the molecular differences between high and low RFI animals need to be better characterized. One of the end products of the conversion of dietary energy to metabolic energy is ATP. ATP is the metabolic currency of the cell. The mitochondria, known as the power house of the cell, generates up to 90% of ATP produced by the cell. The molecular make up of the mitochondria may impact the efficiency of an animal. Investigations into the electron transport chain and the protein profile of mitochondria may provide evidence for the observed differences in efficiencies from animals genetically selected from RFI. The electron transport chain is responsible for the conversion of the metabolic products originating from the TCA cycle into an energy gradient that is used to synthesize ATP from ADP. Superoxide anions are a form of reactive oxygen species (ROS) that originate from electron transport. Superoxide anions can cause oxidative stress and damage to cells and proteins. Energy is required to repair this oxidative damage, potentially leading to the partitioning of dietary energy away from protein accretion and growth towards cellular repair and replacement. In addition to ROS damage, the protein profile of mitochondria may hold clues as to the overall molecular differences between animals genetically selected for high and low RFI. Changes in the abundance of proteins related to ATP production, antioxidant defenses, and cell rescue could provide clues for the observed differences in RFI. Our overall objective was to determine potential molecular differences in the mitochondria using pigs genetically selected for RFI status as a model. Our data show there is a tissue specific increase in ROS production from the mitochondria in the less efficient, high RFI line. Coupled with the increase in ROS, proteins related to ATP production and cellular rescue were more abundant in the more efficient low RFI line. In addition to the data comparing RFI lines, a minimal difference in the protein profile was observed when animals separated by RFI phenotype irrespective of line. [1] McNeill S, Van Elswyk ME. Red meat in global nutrition. Meat Sci. 2012;92:166-73. [2] Murphy MM, Spungen JH, Bi X, Barraj LM. Fresh and fresh lean pork are substantial sources of key nutrients when these products are consumed by adults in the United States. Nutrition Research. 2011;31:776-83. [3] Boddicker N, Gabler NK, Spurlock ME, Nettleton D, Dekkers JCM. Effects of ad libitum and restricted feeding on early production performance and body composition of Yorkshire pigs selected for reduced residual feed intake. Anim. 2011;5:1344-53. [4] Koch RM, Gregory KE, Chambers D, Swiger LA. Efficiency of feed use in beef cattle. J. Anim. Sci. 1963;22:486-94

Influence of Beef Carcass Chilling Rate on Steak Case Life and Quality Traits

Objective To determine if beef carcass weight influences chilling rate, pH decline, beef color, case life and tenderness of steaks from the round, loin, rib and chuck

Temperature During Beef Product Transport Impacts Subprimal and Steak Yield

Objective The objective of this study was to determine the impact of ambient temperature during striploin and sirloin transport on moisture loss, color, and tenderness

Influence of Beef Carcass Chilling Rate on Steak Case Life and Quality Traits

Study Description: Twelve head of fed beef cattle were harvested at the SDSU Meat Laboratory over two days. Carcasses were allotted into two weight groups based on hot carcass weight (HCW): Heavyweight (HW) and Lightweight (LW). Data logging thermometers were placed in the left side of each carcass within the round, loin, rib, and chuck primals to track temperature decline. Carcass measurements including 12th rib fat thickness, ribeye area and marbling score were collected approximately 48 hours postmortem. Steaks from each primal were collected to measure Warner-Bratzler shear force (WBSF), objective and subjective color

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

Influence of Carcass Chilling System on Chuck, Loin, and Round Temperature Decline, Carcass Characteristics, and Tenderness

Objective Determine the effect of chilling systems on beef carcass temperature decline, carcass characteristics, and tenderness

Beef Carcass Weight and Quality Grade Influence Tenderness

Objective The objective was to investigate whether hot carcass weight (HCW) affected Warner-Bratzler shear force (WBSF) and tenderness formation of Denver, strip, and eye of round steaks from USDA Select (Se) and low Choice (LC) beef carcasses.Study Description Select and LC carcasses were selected at a commercial beef plant by HCW (light = 650–750 lb; middle = 850–950 lb; heavy = 1,025–1,150 lb). Steaks were fabricated and aged for 5, 10, and 14 days. Tenderness was determined through WBSF based on industry standards. Additionally, protein degradation was analyzed to determine tenderness formation

Maternal Nutrition and Meat Quality of Progeny

The concept of fetal programming is based on the idea that nutritional status and environmental conditions encountered by the dam during pregnancy can have lifetime impacts on her offspring. These changes in the gestational environment have been shown to influence fetal development and subsequent growth performance, carcass composition, and meat quality characteristics. Beef fetuses can be particularly prone to experiencing variations in the maternal environment during development owing to a relatively long duration of pregnancy potentially exposing the dam to environmental temperature stress and/or seasonal conditions that can compromise feed quality or quantity. If feed is limited or forage conditions are poor, a maternal deficiency in protein and/or energy can occur as well as fluctuations in body condition of the dam. As a result, the fetus may receive inadequate levels of nutrients, potentially altering fetal development. There are critical windows of development during each stage of gestation in which various tissues, organs, and metabolic systems may be impacted. Skeletal muscle and adipose tissue are particularly vulnerable to alterations in the gestational environment because of their low priority for nutrients relative to vital organs and systems during development. The timing and severity of the environmental event or stressor as well as the ability of the dam to buffer negative effects to the fetus will dictate the developmental response. Much of the current research is focused on the influence of specific nutrients and timing of nutritional treatments on offspring carcass composition and meat quality, with the goal of informing strategies that will ultimately allow for the use of maternal nutritional management as a tool to optimize performance and meat quality of offspring

Evidence of decreased muscle protein turnover in gilts selected for low residual feed intake

The objective of this study was to evaluate the contribution of muscle protein turnover (synthesis and degradation) to the biological basis for genetic differences in finisher pigs selected for residual feed intake (RFI). Residual feed intake is defined as the difference between expected feed intake (based on the achieved rate of BW gain and backfat depth of individual pigs) and the observed feed intake of the individual pig. We hypothesized that protein turnover would be reduced in pigs selected for low RFI. Twelve gilts from a line selected for 7 generations for low RFI and 12 from a contemporary line selected for 2 generations for high RFI were paired by age and BW and fed a standard corn–soybean diet for 6 wk. Pigs were euthanized, muscle and liver samples were collected, and insulin signaling, protein synthesis, and protein degradation proteins were analyzed for expression and activities. Muscle from low RFI pigs tended to have less μ- and m-calpain activities (P = 0.10 and 0.09, respectively) and had significantly greater calpastatin activity and a decreased μ-calpain:calpastatin activity ratio (P \u3c 0.05). Muscle from low RFI pigs had less 20S proteasome activity compared with their high RFI counterparts (P\u3c 0.05). No differences in insulin signaling intermediates and translation initiation signaling proteins [mammalian target of rapamycin (mTOR) pathway] were observed (P \u3e 0.05). Postmortem proteolysis was determined in the LM from the eighth generation of the low RFI pigs versus their high RFI counterparts (n = 9 per line). Autolysis of μ-calpain was decreased in the low RFI pigs and less troponin-T degradation product was observed at 3 d postmortem (P \u3c 0.05), indicating slowed postmortem proteolysis during aging in the low RFI pigs. These data provide significant evidence that less protein degradation occurs in pigs selected for reduced RFI, and this may account for a significant portion of the increased efficiency observed in these animals