Effects of Fasting and Transportation on Pork Quality Development and Extent of Postmortem Metabolism

One hundred seventy-seven pigs were used to determine the interaction effects of fasting and length of transport prior to harvest on pork muscle quality. The study design was a 2 × 2 × 3 factorial, which involved two genetic sources, fasting (F) or no fasting (N) of pigs 48-h prior to harvest, and three transport times (0.5, 2.5, or 8.0 h) on a semitrailer to the packing plant. Genetic source was a significant source of variation (P \u3c 0.05) for most composition and muscle quality variables. Fasting reduced hot carcass weight 3.6% (P \u3c 0.05), but length of transport did not affect hot carcass weight (P \u3e 0.05). There were no differences (P \u3e 0.05) in percent lean among fasting and transport treatments. Fasted pigs had higher longissimus dorsi (LD) ultimate pH (pHu), darker lean color, higher marbling score and lower 7-d purge loss, 24-h drip loss, and cooking loss (P \u3c 0.05) than nonfasted pigs. Meat from pigs that were transported 8.0 h had lower glycolytic potential (GP), higher LD and semimembranosus (SM) pHu, darker lean color, and lower L*, 7-d purge loss, 24-h drip loss, cooking loss, and shear force values than meat from pigs transported 0.5 h (P \u3c 0.05). Meat from pigs transported 2.5 h had higher LD and SM pHu and lower L*, 7-d purge loss, 24-h drip loss, and cooking loss than meat from pigs transported 0.5 h (P \u3c 0.05). Meat from pigs transported 8.0 h had higher LD pHu and color scores and lower L* and cooking loss than meat from pigs transported 2.5 h (P \u3c 0.05). The fasting × transport interaction was significant for SM pHu, L*, color score, and drip loss. Fasting improved SM pHu, L*, color score, and drip loss for pigs that were transported 0.5 h (P \u3c 0.05), but when pigs were transported for 2.5 h or 8.0 h, fasting had little or no effect on these muscle quality traits. Fasting lowered GP and increased LD pHu for pigs from the genetic source with the higher initial pork quality (P \u3c 0.05), while fasting had no effect on pork quality for pigs from the genetic source with the lower initial pork quality (P \u3e 0.05). Longer transport times resulted in lower GP and higher LD pHu regardless of genetic source. Fasting and length of transport each had positive effects on pork quality, but length of transport effects was greater in magnitude. When pigs were transported for 0.5 h, fasting for 48 h prior to harvest improved pork quality, but when pigs were transported 2.5 or 8.0 h, fasting had little effect on pork quality

Relationships Among Glycolytic Potential, Dark Cutting (Dark, Firm, and Dry) Beef, and Cooked Beef Palatability

One hundred beef carcasses were selected at three packing plants and were used to determine the relationship between glycolytic potential (GP) and dark, firm, and dry (DFD) beef and to determine the effects of DFD status and GP on cooked beef palatability. Eight individual muscles were excised from one hindquarter of each carcass at d 7 postmortem: longissimus lumborum, psoas major, gluteus medius, tensor fasciae latae, rectus femoris, semimembranosus, biceps femoris, and semitendinosus. Ultimate pH, colorimeter readings, and Warner-Bratzler shear force were determined for all eight muscles at d 7 postmortem. A ninemember trained sensory panel evaluated cooked longissimus lumborum, gluteus medius, and semimembranosus steaks. Traits determined solely for the longissimus lumborum were GP (2 × [glycogen + glucose + glucose- 6-phosphate] + lactate) and ether-extractable fat. A curvilinear relationship existed between GP and ultimate pH within the longissimus muscle. There appeared to be a GP threshold at approximately 100 mol/g, below which lower GP was associated with higher ultimate pH and above which GP had no effect on ultimate pH. The greatest pH and muscle color differences between normal and DFD carcasses were observed in the longissimus lumborum, gluteus medius, semimembranosus, and semitendinosus muscles. Cooked longissimus from DFD carcasses had higher shear force values (46% greater) and more shear force variation (2.3 times greater variation) than those from normal carcasses. Dark cutting carcasses also had higher shear force values for gluteus medius (33% greater) and semimembranosus (36% greater) than normal carcasses. Sensory panel tenderness of longissimus, gluteus medius, and semimembranosus was lower for DFD carcasses than for normal carcasses. Longissimus and gluteus medius flavor desirability scores were lower for DFD than for normal carcasses. Steaks from DFD carcasses had more off-flavor comments than steaks from normal carcasses, specifically more “peanutty,” “sour,” and “bitter” flavors. The DFD effect of higher shear force values was approximately five times greater (+3.11 kg vs +0.63 kg) for carcasses with “slight” marbling scores than for carcasses with “small” marbling scores. In general, higher GP was associated with increased tenderness, even among normal carcasses. In conclusion, low GP was associated with DFD beef and resulted in substantially less-palatable cooked steaks

Effects of High Protein/low Carbohydrate Swine Diets During the Final Finishing Phase on Pork Muscle Quality

Pork color and water-holding capacity defects (pale, soft and exudative, or PSE pork) are functions of muscle pH and cost of the U.S. pork industry $60 million per year (Morgan et al., 1994). Pork with a low ultimate hP (pH\u3c5.5) has a paler color and lower water-holding capacity. Lactic acid build-up is responsible for lowering pH from 7.0, at the time of death, to 5.2-6.0 at 24h postmortem. Postmortem glycolysis produces lactic acid and can only occur in the presence of the substrate glycogen. Therefore, more glycogen in the muscle at slaughter will result in more lactic acid build up and a lower ultimate pH, which will result in a paler color and a lower water-holding capacity (Ellis et al, 1997) Consumption of carbohydrates is the main source of glucose in the blood (Guyton and Hall, 1996). In human studies conducted by Snitker et al., (1997) eight adult males were given one of two isoenergetic diets: a high-carbohydrate diet (75% of energy as carbohydrate, 15% as protein, and 10% as fat), or a low-carbohydrate diet (10% of energy as carbohydrate, 15% as protein, and 75% as fat) for three days. After the three day dietary maniuplation, glycogen content in the vastus lateralis muscle was significatnly lower for the low-carbohydrate subjects; 296 vs 426 mmol glucose/kg dry muscle, respectively (P\u3c0.001) (Snitker et al., 1997). Therefore, this study was conducted to determine if feeding ultra-high protein/low carbohydrate swine diets during the final finishing phase could reduce muscle glycogen and thereby imporve pork muscle quality

The Efficacy of Three Objective Systems for Identifying Beef Cuts That Can Be Guaranteed Tender

The objective of this study was to determine the accuracy of three objective systems (prototype BeefCam, colorimeter, and slice shear force) for identifying guaranteed tender beef. In Phase I, 308 carcasses (105 Top Choice, 101 Low Choice, and 102 Select) from two commercial plants were tested. In Phase II, 400 carcasses (200 rolled USDA Select and 200 rolled USDA Choice) from one commercial plant were tested. The three systems were evaluated based on progressive certification of the longissimus as “tender” in 10% increments (the best 10, 20, 30%, etc., certified as “tender” by each technology; 100% certification would mean no sorting for tenderness). In Phase I, the error (percentage of carcasses certified as tender that had Warner- Bratzler shear force of ≥ 5 kg at 14 d postmortem) for 100% certification using all carcasses was 14.1%. All certification levels up to 80% (slice shear force) and up to 70% (colorimeter) had less error (P \u3c 0.05) than 100% certification. Errors in all levels of certification by prototype BeefCam (13.8 to 9.7%) were not different (P \u3e 0.05) from 100% certification. In Phase I, the error for 100% certification for USDA Select carcasses was 30.7%. For Select carcasses, all slice shear force certification levels up to 60% (0 to 14.8%) had less error (P \u3c 0.05) than 100% certification. For Select carcasses, errors in all levels of certification by colorimeter (20.0 to 29.6%) and by BeefCam (27.5 to 31.4%) were not different (P \u3e 0.05) from 100% certification. In Phase II, the error for 100% certification for all carcasses was 9.3%. For all levels of slice shear force certification less than 90% (for all carcasses) or less than 80% (Select carcasses), errors in tenderness certification were less than (P \u3c 0.05) for 100% certification. In Phase II, for all carcasses or Select carcasses, colorimeter and prototype BeefCam certifications did not significantly reduce errors (P \u3e 0.05) compared to 100% certification. Thus, the direct measure of tenderness provided by slice shear force results in more accurate identification of “tender” beef carcasses than either of the indirect technologies, prototype BeefCam, or colorimeter, particularly for USDA Select carcasses. As tested in this study, slice shear force, but not the prototype BeefCam or colorimeter systems, accurately identified “tender” beef

Reducing Muscle Glycogen in Swine Through Diet Manipulation and Transport to Improve Pork Muscle Quality

The objective of both studies contained in this thesis was to improve pork muscle quality by lowering muscle glycogen levels prior to harvest. The first study involved feeding an ultra-high protein/low carbohydrate (HIPRO) diet to lower the glycogen stores in pork muscle in order to improve pork muscle quality. Forty-eight crossbred barrows at a live weight of 92 ± 18 kg were assigned across five treatments and two reps (four or five pigs per treatment by rep combination). All barrows were fed a control diet (13.1 % CP; com-soybean meal diet) until their assigned treatment began. Treatment was defined as the number of days barrows were fed the HIPRO diet prior to harvest (0, 2, 4, 7, and 14 d). The HIPRO diet (35.9% CP) was 97% extruded soybeans. Daily feed disappearance and weekly body weights were recorded for all barrows. At-death blood glucose levels were determined. Muscle pH, temperature and electrical impedance were measured in the longissmus lumborum and semimembranosus muscles at 45 min, 3 h and 24 h postmortem. Glycolytic potential, Minolta L *a*b* values, visual scores for color, firmness and marbling, water-holding capacity traits (drip loss, purge loss and cooking loss) and Wamer-Bratzler shear force values were determined in the longissmus thoracis et lumborum. Weight gain per day decreased the longer the pigs were fed the HIPRO diet (P \u3c 0.05). Daily feed intake decreased during the first week on the HIPRO diet, but returned to near-control levels during the second week, which when coupled with the continued decreases in daily gain, resulted in substantial decreases in feed conversion during the second week on the HIPRO diet (P \u3c 0.05). Blood glucose levels and glycolytic potentials were not decreased by feeding the HIPRO diet (P \u3e 0.05); and therefore, no differences in rate of pH decline or ultimate pH among dietary treatments were found (P \u3e 0.05). Likewise, there were no differences among dietary treatments in any of the measured meat quality attributes (P \u3e 0.05). Feeding barrows the HIPRO diet for a time period prior to slaughter decreased feed disappearance, rate of gain, and feed efficiency, and was not effective at lowering glycolytic potential or improving pork muscle quality. The objective of this study was to determine the interaction effects of fasting and length of transport prior to harvest on pork muscle quality. Pigs (n = 177) from two different genetic sources were used in the study. The study design was a 2 x 2 x 3 factorial, which involved two genetic sources, fasting (F) or not fasting (N) of pigs 48-h prior to harvest, and three different transport times (0.5, 2.5 or 8.0 h) on the semi-trailer to the packing plant. Genetic source was a significant source of variation (P \u3c 0.05) for composition and muscle quality variables. Fasting reduced hot carcass weight by 3.6% (P \u3c 0.05), whereas length of transport did not affect hot carcass weight (P \u3e 0.05). There were no differences (P \u3e 0.05) in percent lean among treatments. Fasted pigs had higher longissmus dorsi (LD) ultimate pH (pHu), darker lean color, higher marbling scores, and increased water-holding capacity (WHC) (P \u3c 0.05) than non-fasted pigs. Length of transport had significant effects on GP, LD pHu, Semimembranosus (SM) pHu, L*, color score, and WHC (P \u3c 0.05). As transport time increased LD pHu increased and L * and cook loss decreased (P \u3c 0.05). Pigs that were transported for 8.0 h had lower (P \u3c 0.05) Warner-Bratzler Shear force (WBS) values than pigs transported for 0.5 h. Semimembranosus pHu, L*, color score and drip loss were the only traits where the fasting x transport interaction was significant (P \u3c 0.05). Fasting improved SM pHu, L *, color score and drip loss for pigs that were hauled 0.5 h, but when pigs were hauled for 2.5 h or 8.0 h fasting had little or no effect on these muscle quality traits. Both fasting and length of transport by themselves had positive effects on pork quality, but length of transport showed the greatest improvements in pork quality. When pigs were transported for 0.5 h, fasting for 48 h prior to harvest improved pork quality, but when pigs were transported 2.5 h or longer fasting did not improve pork quality. Fasting lowered GP and LD pHu in pigs from a genetic source that had high initial pork quality, while fasting had no effect on pigs from a genetic source with lower initial pork quality. Transport time lowered GP and increased LD pHu no matter which genetic source pigs were from