The Use of Biochemical Measurements to Identify Pre-Slaughter Stress in Pasture Finished Beef Cattle

This study considered the relationship between pre-slaughter stressors and plasma biomarkers in 488 pasture-raised cattle across two experiments. The design aimed to test groups consisting of steer only, heifer only, and mixed sex cattle under direct kill versus rested (14 days in abattoir holding paddocks) protocols. In Experiment One, cattle were sourced from four farms, and transported by trucks and ships on the same day. In Experiment Two, cattle were sourced from four farms where a comparison was made between marketing via two commercial saleyards or direct farm gate consignment to abattoir. Blood samples were collected at exsanguination for subsequent analyses and relation to meat quality attributes. Muscle damage, as indicated by creatine kinase, is the biomarker most correlated to ultimate pH and muscle glycogen concentrations. A two-week rest period is effective for lowering this enzyme and improving muscle glycogen concentration. Although the cattle was subjected to a range of stress inducing treatments, we found that plasma biomarkers alone appeared insufficient for use as diagnostic stress indicators.

Changes in the power-duration relationship following prolonged exercise: estimation using conventional and all-out protocols and relationship with muscle glycogen

It is not clear how the parameters of the power-duration relationship [critical power (CP) and W′] are influenced by the performance of prolonged endurance exercise. We used severe-intensity prediction trials (conventional protocol) and the 3-min all-out test (3MT) to measure CP and W′ following 2 h of heavy-intensity cycling exercise and took muscle biopsies to investigate possible relationships to changes in muscle glycogen concentration ([glycogen]). Fourteen participants completed a rested 3MT to establish end-test power (Control-EP) and work done above EP (Control-WEP). Subsequently, on separate days, immediately following 2 h of heavy-intensity exercise, participants completed a 3MT to establish Fatigued-EP and Fatigued-WEP and three severe-intensity prediction trials to the limit of tolerance (Tlim) to establish Fatigued-CP and Fatigued-W′. A muscle biopsy was collected immediately before and after one of the 2-h exercise bouts. Fatigued-CP (256 ± 41 W) and Fatigued-EP (256 ± 52 W), and Fatigued-Wʹ (15.3 ± 5.0 kJ) and Fatigued-WEP (14.6 ± 5.3 kJ), were not different ( P > 0.05) but were ~11% and ~20% lower than Control-EP (287 ± 46 W) and Control-WEP (18.7 ± 4.7 kJ), respectively ( P < 0.05). The change in muscle [glycogen] was not significantly correlated with the changes in either EP ( r = 0.19) or WEP ( r = 0.07). The power-duration relationship is adversely impacted by prolonged endurance exercise. The 3MT provides valid estimates of CP and W′ following 2 h of heavy-intensity exercise, but the changes in these parameters are not primarily determined by changes in muscle [glycogen].

Effects of pre-slaughter ascorbic acid administration on some physiological stress response and meat quality traits of lambs and kids subjected to road transport

The present study determined the effects of pre-slaughter ascorbic acid administration on some physiological indicators and meat quality traits of road transport-stressed lambs and kids. Eighteen lambs and 18 kids were divided into the following three groups: no transportation (T0), 3-h transportation (T3), and ascorbid acid administered at 125 mg/kg before 3-h transportation (T3+C). The liveweight loss and rectal temperature were similar, while there were significant differences among groups for some biochemical parameters in both lambs and kids. Glucose concentrations significantly increased after transportation in lambs (P = 0.005) and kids (P &lt; 0.001). Ascorbic acid had significant effects on serum glucose of lambs. T3 lambs had higher glucose concentrations than did T0 lambs (P &lt; 0.001), while T0 and T3+C lambs were found to have similar concentrations. Oxidative status in lambs and kids, as determined by serum malondialdehyde concentration, did not differ among groups. However, some meat quality traits were negatively influenced by transportation. T3 lambs had a significantly lower muscle glycogen concentration than did T0 and T3+C lambs (P = 0.018), while ultimate pH was similar among groups. Muscle glycogen concentration was significantly lower (P = 0.008) and ultimate pH was higher in T3 and T3+C kids (P = 0.028). T3 and T3+C groups had darker meat (L*) than did T0 groups both in lambs and kids, whereas a*, cooking loss and water-holding capacity were similar among groups. The effect of ascorbic acid on meat toughness was significant and shear force value in T0 lambs was lower than that in T3 lambs (P = 0.009), while T0 and T3+C lambs were found to have similar shear force values. Overall, the administration of ascorbic acid to lambs before transportation could partly reduce the adverse effects of road transportation stress, whereas its effects on kids were found to be insignificant.

PO-074 Acute effects of lactate administration prior to endurance exercise on intramuscular signaling

Objective High-intensity exercise, which increases blood lactate concentration, is known as an effective method to induce mitochondrial biogenesis compared to traditional endurance exercise. In addition, it has been reported that lactate acts as a signaling molecule inducing mitochondrial biogenesis. Therefore, we hypothesized that efficacy of high-intensity exercise is partly induced by lactate. The purpose of this study was to investigate the effects of lactate administration on signaling related to mitochondrial biogenesis. Methods 8-week-old male ICR mice were used in this study. Mice were intraperitoneally administrated phosphate buffered saline (PBS) or 1 g/kg of body weight of sodium lactate. Immediately after the administration, mice were kept sedentary or performed treadmill exercise (20 m/min) for 60 min. Hence, there are the following four groups in this study: the PBS-sedentary, the Lactate-sedentary, the PBS-exercised and the Lactate-exercised. The blood, and the soleus and the plantaris muscles were harvested immediately after the rest or exercise. Nucleus and mitochondria were isolated to assess the localization of p53. Two-way ANOVA (Lactate x Exercise) was performed for statistical analysis. Results We first measured blood substrates and muscle glycogen concentrations. Lactate administration significantly increased blood lactate and plasma free fatty acid concentrations. Exercise significantly decreased glycogen concentration both in the soleus and the plantaris muscles. Furthermore, lactate administration significantly decreased muscle glycogen concentration only in the soleus muscle. To clarify the effects of lactate administration on intramuscular signaling, we assessed kinases related to mitochondrial biogenesis. Main effect of exercise was observed in phosphorylation state of AMPK, ACC, p38 MAPK, and CaMKII in the soleus and the plantaris muscles. There was a trend of negative effect of lactate in CaMKII phosphorylation in the soleus muscle. However, there was no effect of lactate administration on the other kinases. We also investigated phosphorylation and localization of p53. As a result, lactate administration tended to increase p53 phosphorylation in the plantaris muscle. However, p53 was not translocated to nucleus or mitochondria. Conclusions Lactate administration affected plasma FFA concentration and muscle glycogen concentration. However, acute lactate administration did not dramatically change intracellular signaling assessed in this study.