Background/Objectives: Early postmortem mitochondrial function and apoptotic activation affect meat quality development. Nicotinamide riboside (NR) supplementation to pigs prior to harvest can improve pork color stability, but its mechanism remains unclear. This study aimed to evaluate the impact of NR supplementation on early postmortem mitochondrial functionality and apoptosis. Methods: Sixteen pigs (N = 16) were individually fed a control or NR-supplemented diet (30 mg·kg body weight⁻¹·d⁻¹) for 10 days prior to harvest. Longissimus dorsi muscle samples were collected at 45 min and 24 h postmortem and analyzed for mitochondrial functionality using high-resolution respirometry and apoptotic protein abundance (apoptosis regulator Bcl-2-associated X (BAX), apoptotic inducing factor (AIF), and caspase 3 (CASP3)) via immunoblotting. Results: NR-supplemented muscle exhibited lower proton leak-associated respiration at 45 min postmortem (p < 0.05), followed by a slower accumulation of mitochondrial outer membrane permeabilization (MOMP; p < 0.05) and a slower loss of mitochondrial integral function (p < 0.05) from 45 min to 24 h postmortem. NR supplementation decreased BAX abundance at 45 min postmortem but increased mature AIF abundance (62 kDa) at 24 h postmortem (p < 0.05). The abundance of CASP3 fragments (~29 kDa) decreased from 45 min to 24 h postmortem, independent of treatment (p < 0.05). Conclusions: NR supplementation demonstrated the potential to protect mitochondrial integral function and alleviate apoptotic activation in early postmortem porcine skeletal muscle, which might contribute to a higher meat color stability in NR-supplemented pork during retail display.

The objective of this study was to determine the daily dietary nicotinamide riboside (NR) dose required to maximize the delay of subjective muscle fatigue onset. Barrows (N = 100) were assigned to one of five treatments: a conventional swine finishing diet containing 0 (CON), 15 (15NR), 30 (30NR), 45 (45NR) mg·kg body weight⁻¹·d⁻¹ NR, or CON supplemented with 45 mg·kg body weight⁻¹·d⁻¹ NR by drench or cookie dough (DRE). All treatments were administered for the final 11 days of feeding. On supplementation d 10, barrows individually experienced a performance test at 1.09 m/s until they were subjectively exhausted. Wireless electromyography (EMG) sensors were affixed to the biceps femoris (BF), tensor fascia latae (TFL), and semitendinosus (ST) to measure real-time muscle activity. There were no treatment effects for barrow speed (p = 0.57), a tendency for a treatment effect (p = 0.07) for distance, and a treatment effect (p = 0.04) on time to exhaustion. Barrows of the 15NR and DRE treatments had greater (p = 0.05) distances to exhaustion than CON barrows but did not differ from other NR barrows (p > 0.11). Barrows in the 45NR treatment did not differ (p = 0.11) in distance from 30NR barrows but tended to have a greater (p = 0.07) distance compared to CON barrows. All other treatment comparisons did not differ (p > 0.27). Barrows in the DRE treatment moved for longer (p < 0.01) than CON barrows, but all other treatments did not differ from each other (p > 0.15). There was no treatment × period interaction for all muscles’ root mean square (RMS) values (p > 0.16), but there were Period effects for all muscles (p < 0.01) and a Treatment effect (p = 0.04) in the TFL. For all muscles, period 4 had greater RMS values than all other periods (p < 0.01), who did not differ from each other (p > 0.29). In the TFL, CON barrows had greater RMS values during the performance test compared to all NR treatments (p < 0.02), who did not differ from each other (p > 0.18). Overall, NR demonstrates potential in being a useful tool in fatigue prevention, but efficient administration of the compound needs further investigation.

When measuring real-time in vivo muscle fatigue with electromyography (EMG), data collection can be compromised by premature sensor removal or environmental noise; therefore, the objective of this study was to develop a postmortem in vivo methodology to induce muscle fatigue and measure it using EMG. Barrows (N = 20) were stratified by weight and randomly allocated into one of two treatments. The treatments consisted of barrows being subjected to a hog electric stunner super-contraction cycle (ES) or not (CON) postmortem. The right hind limb bicep femoris (BF) and semitendinosus (ST) were selected for ambulatory movement simulation using electronic muscle stimulation (EMS). Muscle workload during EMS was measured with EMG using median power frequency (MdPF) and root mean square (RMS) as indicators of action potential velocity and muscle fiber recruitment. Ambulatory movement was induced and recorded for 20 min with a 4:4 duty cycle at 70 Hz. Muscle biopsies were collected pre- and post-EMS for metabolite analyses to corroborate muscle fatigue onset. There was a TRT × Muscle interaction for normalized RMS percentage (p < 0.01), where BF from CON barrows had greater values (p < 0.01). There were no interactions or TRT main effects for the MdPF normalized value (p ≥ 0.25), but there were Period and muscle effects on MdPF (p < 0.01). Bicep femoris had smaller (p < 0.01) MdPF than ST. The percentage of MdPF decreased (p < 0.01) by Period 5 compared to the other Periods, which did not differ from each other (p ≥ 0.38). There were TRT × Muscle and Muscle × Period interactions for ATP muscle concentration (p ≤ 0.03). The concentration of CON BF ATP was greater (p < 0.01) than that of ES BF and CON and ES ST, which did not differ from each other (p ≥ 0.11), but the APT concentration tended to differ between ES BF and ES ST (p = 0.06). Semitendinosus ATP concentration decreased (p < 0.01) post-EMS compared to ST pre- and BF pre- and post-EMS (p ≥ 0.29), but BF and ST concentration tended to differ pre-EMS (p = 0.07). The data indicated that EMS is a valuable tool for replicating ambulatory movement or physical activity, but super-contraction is not a means to accelerate postmortem muscle fatigue onset. Therefore, further refinement, such as longer EMS stimulation time, should be considered.

Background/Objective: Delaying muscle fatigue could alleviate economic and food security, and welfare concerns associated with transporting market-weight pigs to harvest. Previous research demonstrates barrow nicotinamide riboside (NR) supplementation at varying doses during the last 10 d of finishing shows to be a countermeasure to muscle fatigue by reducing muscle fiber recruitment and increasing mitochondrial DNA expression in a dose-dependent manner. Therefore, this study aims to determine if a greater NR dose further enhances barrow fatigue resistance and characterize muscle mitochondria content and efficiency. Methods: Barrows (N = 87) were assigned to one of two dietary NR supplementation doses (TRT): 0 (0NR) or 150 (150NR) mg/kg body weigh NR administered during the last 14 d of finishing. Muscle (MUS) biopsies were collected on supplementation d (DAY) 0, 7 and 14 from three hind-leg muscles for NAD+ quantification and mitochondrial DNA expression and efficiency. On days 15 and 16, barrows were subjected to a performance test until they were subjectively exhausted. Electromyography data collection during the performance test were divided into five periods (PER) and included normalized root mean square (nRMS) from the same muscles. Results: There were no three-way interaction for nRMS (p > 0.83), but there were MUS × TRT and PER × TRT interactions (p < 0.05). During performance testing, 150NR had greater nRMS than 0NR in the bicep femoris (BF) and tensor fasciae latae (TFL; p < 0.01), but there were no differences in the semitendinosus (ST; p = 0.77). Treatments did not differ during PER 1 and 2 (p > 0.14) but 150NR had greater nRMS than 0NR during PER 3, 4 and 5 (p < 0.01) across all muscles. There was no three-way interaction for normalized (nNAD+; p = 0.14), but there was a DAY × TRT interaction (p < 0.05). There were no differences between 0NR and 150NR at d 0 (p = 0.95); however, by d 7 and 14, 150NR muscles had greater nNAD+ than 0NR muscles (p < 0.01). There tended to be a three-way interaction for mitochondrial DNA expression (p = 0.09). At supplementation d 14, all 150NR muscles had greater mitochondrial DNA expression and electron transport chain complex I and II activities (p < 0.01). When normalized to citrate synthase activity, electron transport chain complex I and II activity did not differ (p > 0.05). Conclusions: Large-dose NR supplementation appears to support sustained muscle fiber recruitment during prolonged activity and enhance fatigue resilience, primarily through increased NAD+ and mitochondrial biomarkers abundance and not through mitochondrial efficiency.

We hypothesized that maternal overfeeding and restricted feeding during gestation would alter the collagen content, muscle fiber cross-sectional area (CSA), and meat tenderness in offspring. Pregnant ewes were fed 100% (CON), 60% (RES), or 140% (OVER) of their requirements from day 30 of gestation until parturition. Male offspring were necropsied at 282 ± 1.8 days of age. Gene expression and CSA were quantified in the longissimus (LM) and semitendinosus (STN) muscles. The Warner–Bratzler shear force (WBSF) was quantified in LM. Data were analyzed by one-way ANOVA, with diet as a fixed effect. Differences were considered significant at p ≤ 0.05 or a tendency at p ≤ 0.10. Semitendinosus CSA was smaller in OVER and RES than CON rams (p = 0.02). Longissimus CSA was larger in RES than OVER and CON rams (p = 0.002). OVER LM had reduced WBSF compared with CON rams (p = 0.03). Myogenic genes bone morphogenic protein 1 (BMP1) and paired box 7 were greater in RES LM than OVER (p ≤ 0.02). Maternal diet altered the fibrogenic genes fibronectin 1 (p = 0.07), lysyl oxidase (p = 0.07), and collagen 1A1 (COL1A1; p = 0.08) in the LM and COL1A1, COL3A1, and BMP1 (p ≤ 0.09) in the STN. Poor maternal diet during gestation alters muscle and meat characteristics that may impact meat quality.