Treatment with a tissue-selective oestrogen complex does not affect disease pathology but reduces pre-BI cells in lupus-prone mice.

OBJECTIVE: Systemic lupus erythematosus (SLE or lupus) is an autoimmune disease characterized by B-cell dysfunction, production of autoantibodies, and immune complex formation. Lupus is overrepresented in females, indicating that sex hormones play a role in the pathophysiology. Treatment with a tissue-selective oestrogen complex (TSEC) containing conjugated oestrogens and the selective oestrogen receptor modulator bazedoxifene (BZA) protects against postmenopausal vasomotor symptoms and osteoporosis, but its impact on organ damage in lupus is not fully understood. METHOD: We used ovariectomized MRL/lpr mice, treated with two different physiological doses of 17ß-oestradiol-3-benzoate (E2), BZA, or TSEC (E2 plus BZA), to assess early and late B-cell development and to determine histological disease manifestations in the kidneys and salivary glands. RESULTS: TSEC treatment reduced the frequency of the pre-BI population in bone marrow to levels equivalent to treatment with physiological doses of E2 alone but did not affect any of the other examined B-cell populations. Our earlier studies indicated that TSEC treatment did not aggravate disease development in ovariectomized MRL/lpr mice, while protecting against trabecular bone loss. Here, we follow up on our previous study and show that neither ovariectomy alone nor TSEC treatment of ovariectomized MRL/lpr mice influenced perivascular lymphocyte infiltration to the kidneys or salivary glands. CONCLUSION: TSEC does not aggravate a mouse model of lupus, when given in doses that protect against postmenopausal lupus-associated bone loss. This indicates that further investigations into TSEC as a treatment for osteoporosis or vasomotor symptoms in postmenopausal women with SLE are warranted.

Fiber hypertrophy and increased oxidative capacity can occur simultaneously in pig glycolytic skeletal muscle.

An inverse relationship between skeletal muscle fiber cross-sectional area (CSA) and oxidative capacity suggests that muscle fibers hypertrophy at the expense of oxidative capacity. Therefore, our objective was to utilize pigs possessing mutations associated with increased oxidative capacity [AMP-activated protein kinase (AMPKγ3(R200Q))] or fiber hypertrophy [ryanodine receptor 1 (RyR1(R615C))] to determine if these events occur in parallel. Longissimus muscle was collected from wild-type (control), AMPKγ3(R200Q), RyR1(R615C), and AMPKγ3(R200Q)-RyR1(R615C) pigs. Regardless of AMPK genotype, RyR(R615C) increased fiber CSA by 35%. In contrast, AMPKγ3(R200Q) pig muscle exhibited greater citrate synthase and ß-hydroxyacyl CoA dehydrogenase activity. Isolated mitochondria from AMPKγ3(R200Q) muscle had greater maximal, ADP-stimulated oxygen consumption rate. Additionally, AMPKγ3(R200Q) muscle contained more (∼50%) of the mitochondrial proteins succinate dehydrogenase and cytochrome c oxidase and more mitochondrial DNA. Surprisingly, RyR1(R615C) increased mitochondrial proteins and DNA, but this was not associated with improved oxidative capacity, suggesting that altered energy metabolism in RyR1(R615C) muscle influences mitochondrial proliferation and protein turnover. Thus pigs that possess both AMPKγ3(R200Q) and RyR(R615C) exhibit increased muscle fiber CSA as well as greater oxidative capacity. Together, our findings support the notion that hypertrophy and enhanced oxidative capacity can occur simultaneously in skeletal muscle and suggest that the signaling mechanisms controlling these events are independently regulated.

Exploring the impact of fatty acid composition on carcass and meat quality in Bos taurus indicus influenced cattle.

The study of fatty acid (FA) and mineral content in beef is crucial for bridging health and taste. Understanding these components is essential for catering to consumer preferences for nutritious and tasty food, in line with current dietary trends and health recommendations. This holistic view of beef quality is key to helping both producers and consumers make more knowledgeable and health-oriented decisions in meat consumption. The objectives of this study were to 1) characterize the FA composition and mineral concentration of beef from Brangus cattle; 2) estimate their heritability; and 3) calculate the genetic and phenotypic correlations of carcass and meat quality traits to FA composition and mineral concentrations. Brangus steers were evaluated for meat quality and sampled for nutritional content measurements. Brangus cattle had palmitic acid levels as low as 21%, and stearic acid levels as high as 26%, which is notable since stearic acid is considered to have a neutral or potentially beneficial impact on cholesterol levels, unlike other saturated fats. Additionally, Brangus cattle had oleic acid levels as high as 53%, a beneficial monounsaturated fat, and linoleic acid concentrations as high as 12%, an essential omega-6 FA. Saturated FA showed weak negative correlations (-0.06 to -0.15) with hot carcass weight, marbling, and fat over ribeye, similar to polyunsaturated FA which had moderate negative correlations (-0.19 to -0.37) with these traits. Conversely, monounsaturated FA was positively correlated (0.16 to 0.34) with these traits, suggesting that higher levels of monounsaturated FA, particularly oleic acid, are associated with improved meat quality and consumer-desirable traits such as increased marbling. This relationship where higher marbling is linked with increased monounsaturated FA and decreased saturated FA is unique in Brangus cattle, differing from other breeds where increased intramuscular fat typically raises FA saturation levels. The variation in FA observed in Brangus cattle highlights the breed's potential to provide nutritionally enriched beef. With selective breeding, it may be possible to improve both the nutritional value and marbling of the meat, meeting consumer demand for healthier, tastier options. Overall, the study underscores the intricate relationships between FA composition, mineral content, and meat quality, with implications for breeding and nutrition strategies aimed at improving meat quality and healthfulness.

Interleukin 17A: a Janus-faced regulator of osteoporosis.

Interleukin (IL)-17A is a well-described mediator of bone resorption in inflammatory diseases, and postmenopausal osteoporosis is associated with increased serum levels of IL-17A. Ovariectomy (OVX) can be used as a model to study bone loss induced by estrogen deficiency and the role of IL-17A in osteoporosis development has previously been investigated using various methods to inhibit IL-17A signaling in this model. However, the studies show opposing results. While some publications reported IL-17A as a mediator of OVX-induced osteoporosis, others found a bone-protective role for IL-17 receptor signaling. In this study, we provide an explanation for the discrepancies in previous literature and show for the first time that loss of IL-17A has differential effects on OVX-induced osteoporosis; with IL-17A being important for cortical but not trabecular bone loss. Interestingly, the decrease in trabecular bone after OVX in IL-17A knock-out mice, was accompanied by increased adipogenesis depicted by elevated leptin levels. Additionally, the bone marrow adipose tissue expanded, and the bone-turnover decreased in ovariectomized mice lacking IL-17A compared to ovariectomized WT mice. Our results increase the understanding of how IL-17A signaling influences bone remodeling in the different bone compartments, which is of importance for the development of new treatments of post-menopausal osteoporosis.

National Beef Quality Audit-2016: Transportation, mobility, and harvest-floor assessments of targeted characteristics that affect quality and value of cattle, carcasses, and by-products.

The National Beef Quality Audit-2016 (NBQA-2016) was conducted to assess current transportation, mobility, and quality characteristics of U.S. fed steers and heifers. Data were collected at 17 beef processing facilities between March and November 2016. About 8,000 live cattle were evaluated for transportation and mobility, and about 25,000 carcasses were evaluated on the slaughter floor. Cattle were in transit to the slaughter facility for a mean duration of 2.7 h from a mean distance of 218.5 km using trailers with dimensions ranging from 17.84 m2 to 59.09 m2. Area allotted per animal averaged 1.13 m2 and ranged from 0.85 m2 to 2.28 m2. A total of 96.8% of cattle received a mobility score of 1 (walks easily, no apparent lameness). Identification types (35.1% had multiple) were lot visual tags (61.5%), individual tags (55.0%), electronic tags (16.9%), metal-clip tags (9.2%), bar-coded tags (0.05%), wattles (0.01%), and other (2.6%). Cattle were black-hided (57.8%), Holstein (20.4%), red-hided (10.5%), yellow-hided (4.8%), gray-hided (2.9%), brown-hided (1.3%), and white-hided (1.1%). Unbranded hides were observed on 74.3% of cattle; 18.6% had brands located on the butt, 6.3% on the side, and 1.3% on the shoulder (values exceed 100% due to multiple brands). For hide-on carcasses, 37.7% displayed no mud or manure; specific locations for mud or manure were legs (40.8%), belly (33.0%), tail region (15.5%), side (6.8%), and top-line (3.9%). Cattle without horns represented 83.3% of the sample, and cattle that did have horns measured: < 2.54 cm (5.5%), 2.54 to 12.7 cm (8.3%), and > 12.7 cm (2.9%). Carcasses without bruises represented 61.1% of those sampled, whereas 28.2% had 1, 8.2% had 2, 2.1% had 3, and 0.3% had 4 bruises. Of those carcasses with a bruise, the bruise was located on the loin (29.7%), round (27.8%), chuck (16.4%), rib (14.4%), and brisket/plate/flank (11.6%). Frequencies of offal condemnations were livers (30.8%), lungs (18.2%), viscera (16.3%), hearts (11.1%), heads (2.7%), and tongues (2.0%). Compared to NBQA-2011, fewer cattle were identified for traceability, fewer were black-hided, a greater number were Holstein cattle, more with no brand and no horns, fewer without bruises, more liver, lung, and viscera condemnations, and fewer heads and tongues were condemned. The NBQA remains an influential survey for the U.S. beef industry to provide benchmarks and strategic plans for continued improvement of beef quality and consistency.

National Beef Quality Audit-2016: Transportation, mobility, live cattle, and carcass assessments of targeted producer-related characteristics that affect value of market cows and bulls, their carcasses, and associated by-products.

The National Beef Quality Audit-2016 marks the fourth iteration in a series assessing the quality of live beef and dairy cows and bulls and their carcass counterparts. The objective was to determine the incidence of producer-related defects, and report cattle and carcass traits associated with producer management. Conducted from March through December of 2016, trailers (n = 154), live animals (n = 5,470), hide-on carcasses (n = 5,278), and hide-off hot carcasses (n = 5,510) were surveyed in 18 commercial packing facilities throughout the United States. Cattle were allowed 2.3 m2 of trailer space on average during transit indicating some haulers are adhering to industry handling guidelines for trailer space requirements. Of the mixed gender loads arriving at processing facilities, cows and bulls were not segregated on 64.4% of the trailers surveyed. When assessed for mobility, the greatest majority of cattle surveyed were sound. Since the inception of the quality audit series, beef cows have shown substantial improvements in muscle. Today over 90.0% of dairy cows are too light muscled. The mean body condition score for beef animals was 4.7 and for dairy cows and bulls was 2.6 and 3.3, respectively. Dairy cattle were lighter muscled, yet fatter than the dairy cattle surveyed in 2007. Of cattle surveyed, most did not have horns, nor any visible live animal defects. Unbranded hides were observed on 77.3% of cattle. Carcass bruising was seen on 64.1% of cow carcasses and 42.9% of bull carcasses. However, over half of all bruises were identified to only be minor in severity. Nearly all cattle (98.4%) were free of visible injection-site lesions. Current results suggest improvements have been made in cattle and meat quality in the cow and bull sector. Furthermore, the results provide guidance for continued educational and research efforts for improving market cow and bull beef quality.

National Beef Quality Audit - 2016: Survey of carcass characteristics through instrument grading assessments.

The instrument grading assessment portion of the National Beef Quality Audit (NBQA) - 2016 allows the unique opportunity to evaluate beef carcass traits over the course of a year. One week of instrument grading data was collected each month from 5 beef processing corporations encompassing 18 facilities from January 2016 through December 2016 ( = 4,544,635 carcasses). Mean USDA yield grade (YG) was 3.1 with 1.37 cm fat thickness (FT), 88.9 cm LM area, 393.6 kg HCW, and 2.1% KPH. Frequency distribution of USDA YG was 9.5% YG 1, 34.6% YG 2, 38.8% YG 3, 14.6% YG 4, and 2.5% YG 5. Increases in HCW and FT since the NBQA-2011 were major contributors to differences in mean YG and the (numerically) increased frequency of YG 3, 4, and 5 carcasses found in the current audit. Mean marbling score was Small, and the distribution of USDA quality grades was 4.2% Prime, 71.4% Choice, 21.7% Select, and 2.7% other. Frequency of carcasses grading Prime on Monday (6.43%) was numerically higher than the average frequency of carcasses grading Prime overall (4.2%). Monthly HCW means were 397.6 kg in January, 397.2 kg in February, 396.5 kg in March, 389.3 kg in April, 384.8 kg in May, 385.0 kg in June, 386.1 kg in July, 394.1 kg in August, 399.1 kg in September, 403.9 kg in October, 406.5 kg in November, and 401.9 kg in December. Monthly mean marbling scores were Small in January, Small in February, Small in March, Small in April, Small in May, Small in June, Small in July, Small in August, Small in September, Small in October, Small in November, and Small in December. Both mean HCW and mean marbling score declined in the months of May and June. The month with the greatest numerical frequency of dark cutters was October (0.74%). Comparison of overall data from in-plant carcass and instrument grading assessments revealed close alignment of information, especially for YG (3.1 for in-plant assessment versus 3.1 for instrument grading) and marbling (Small for in-plant assessment versus Small for instrument grading). These findings allow the beef industry access to the greatest volume of beef value-determining characteristics for the U.S. fed steer and heifer population than ever reported, resulting in potentially more precise targeting of future quality and consistency efforts.

National Beef Quality Audit-2016: In-plant survey of carcass characteristics related to quality, quantity, and value of fed steers and heifers.

The National Beef Quality Audit (NBQA)-2016 used in-plant cooler assessments to benchmark the current status of the fed steer and heifer beef industry in the United States. In-plant cooler assessments ( = 9,106 carcasses) were conducted at 30 facilities, where approximately 10% of a single day's production were evaluated for USDA quality grade (QG) and yield grade (YG) factors. Frequencies of evaluated traits were 66.5% steer and 33.4% heifer sex classes and 82.9% native, 15.9% dairy-type, and 1.2% estimated breed types. Mean USDA YG factors were 1.42 cm for adjusted fat thickness, 89.5 cm for LM area, 390.3 kg for HCW, and 1.9% for KPH. Mean USDA YG was 3.1, with a frequency distribution of 9.6% YG 1, 36.7% YG 2, 39.2% YG 3, 12.0% YG 4, and 2.5% YG 5. Mean USDA QG traits were Small for marbling score, A for overall maturity, A55 for lean maturity, and A for skeletal maturity. Mean USDA QG was Select with a frequency distribution of QG of 3.8% Prime, 67.3% Choice, 23.2% Select, and 5.6% lower score. Lower score included dark cutter (1.9%), blood splash (0.1%), and hard bone, which are USDA overall maturity scores of C or older (1.8%). Marbling score distributions were 0.85% Slightly Abundant or greater, 7.63% Moderate, 23.54% Modest, 39.63% Small, 23.62% Slight, and 0.83% Traces or less. Carcasses that were Choice or Select and USDA YG 2 or 3 accounted for 70.7% of the carcasses evaluated. Compared with the previous NBQA, we found a numerical increase in mean USDA YG, USDA QG, adjusted fat thickness, HCW, LM area, and marbling score with an increase in dairy-type carcasses and percentage of carcasses grading USDA Prime and Choice as well as frequency of USDA YG 4 and 5. The findings from this study will be used by all segments of the industry to understand and improve the quality of fed steer and heifer beef that is being produced.

Effect of early grain feeding of beef steers on postabsorptive metabolism.

The objective of this study was to determine the effect of early weaning followed by a period of high-grain feeding on plasma acetate kinetics and signaling protein phosphorylation in LM tissue of growing steers. We hypothesized that early grain feeding would result in altered cell signaling and acetate use to support observed improvements in carcass gain and marbling. Fall-born Angus × Simmental steers were weaned at 106 ± 4 d of age (early weaned [EW]; n = 6) and fed a high-grain diet for 148 d or remained with their dams (normal weaned [NW]; n = 6) on pasture until weaning at 251 ± 5 d of age. Both treatments were subsequently combined and grazed on mixed summer pasture to 394 ± 5 d of age followed by a feedlot ration until harvest at 513 ± 5 d of age. Longissimus muscle tissue biopsies were collected at 253 ± 5 and 394 ± 5 d of age and at harvest. Total and phosphorylated forms of 5' adenosine monophosphate-activated protein kinase (AMPK) and downstream proteins of the mammalian target of rapamycin signaling pathway were determined by western blotting. Eight steers were used to assess acetate clearance at different age points via a bolus infusion of acetate (4 mmol/kg of BW). Early weaned steers had greater (P < 0.05) ADG than NW steers during the early grain feeding period. Phosphorylated to total ratios of ribosomal protein S6 (rpS6) and ribosomal protein S6 kinase 1 (S6K1) were significantly different during the early grain feeding period. Phosphorylated to total ratios of S6K1, rpS6, acetyl-CoA carboxylase, and 4E binding protein 1 and the absolute amount of phosphorylated AMPK were correlated with ADG, explaining 46% of the variance. Acetate clearance rates were less (P < 0.05) and synthesis rates were greater (P = 0.06) in EW steers during early grain feeding. Acetate synthesis rates were also greater (P < 0.05) in NW steers at harvest, suggesting a permanent shift in the gut microflora or gut function in response to the treatment. Neither treatment nor acetate infusion significantly affected plasma glucose or insulin concentrations. Plasma ß-hydroxybutyric acid concentrations increased with acetate infusion (P < 0.05). Based on these results, altered cell signaling during the early grain feeding period likely mediated increased protein deposition, leading to increased carcass weights, but observed changes in acetate appearance and clearance rates do not appear to explain the observed differences in intramuscular fat deposition during the terminal feeding period.

Effect of repeated administration of combination trenbolone acetate and estradiol implants on growth, carcass traits, and beef quality of long-fed Holstein steers.

Our objective was to determine the effect of repeated use of implants on feedlot performance and carcass characteristics of Holstein cattle. Holstein steers (n = 128) weighing an average of 211 kg were blocked by weight and randomly assigned to 16 pens. At the start of the trial (d 0), pens were assigned to one of four treatments: 1) nonimplanted control (C); 2) implant on d 0, 112, and 224 (T3); 3) implant on d 112 and 224 (T2); and 4) implant on d 224 (T1). Component TE-S implants (120 mg of trenbolone acetate and 24 mg of estradiol per implant) were used for all treatments during the 291-d feeding period. Over the course of the study, T2 and T3 cattle had greater ADG and final weights than C and T1 cattle (P < 0.05). Steers were harvested at a commercial abattoir on d 291. Hot carcass weights of T3 steers were greater than those of C and T1 steers (P < 0.05). Dressing percentage, adjusted 12th-rib fat, percentage of kidney, pelvic, and heart fat, yield grade, and longissimus color were not different among treatments (P > or = 0.26). Longissimus muscle areas (LMA) of T2 and T3 carcasses were larger than LMA of C (P < 0.01). No USDA Select carcasses were produced from C cattle, whereas the percentage of Select carcasses from implanted cattle ranged from 10 to 18%. Skeletal maturity advanced (P < 0.05) progressively with each additional implant. Steaks from T3 carcasses had a higher percentage of protein than controls (P < 0.05) and were less tender than all other treatments (P < 0.05). Repeated administration of combination trenbolone acetate and estradiol implants increased ADG and resulted in heavier carcasses with larger LMA. Administration of three successive implants decreased tenderness of Holstein beef, and resulted in more advanced skeletal maturity scores.

Supplementing antioxidants to pigs fed diets high in oxidants: II. Effects on carcass characteristics, meat quality, and fatty acid profile.

The study was conducted to determine effects of dietary supplementation with a blend of antioxidants (ethoxyquin and propyl gallate) on carcass characteristics, meat quality, and fatty acid profile in finishing pigs fed a diet high in oxidants. A total of 100 crossbred barrows (10.9±1.4 kg BW, 36±2 d of age) were randomly allotted to 5 diet treatments (5 replicate pens per treatment, 4 pigs per pen). Treatments included: 1) HO: high oxidant diet containing 5% oxidized soy oil and 10% PUFA source which contributed 5.56% crude fat and 2.05% docosahexanoic acid (DHA) to the diet; 2) VE: the HO diet with 11 IU/kg of added vitamin E; 3) AOX: the HO diet with antioxidant blend (135 mg/kg); 4) VE+AOX: the HO diet with both vitamin E and antioxidant blend; and 5) SC: a standard corn-soy control diet with nonoxidized oil and no PUFA source. The trial lasted for 118 d; on d 83, the HO diet pigs were switched to the SC diet due to very poor health. From that point, the VE pigs displayed the poorest performance. On d 118, 2 pigs from each pen were harvested for sampling. Compared to pigs fed SC diet, the HO and VE pigs (P<0.05) showed lighter carcass weight, less back fat, less lean body mass, and smaller loin eye area. In addition, the VE pigs had decreased dressing percentage than the AOX and VE+AOX pigs (65.7 vs. 75.3 and 74.2%). Compared to the SC pigs, greater moisture percentage (74.7 vs. 77.4%) and less extractable lipid content (2.43 vs. 0.95%) were found in VE fed pigs (P<0.05). Drip loss of loin muscle in VE pigs was less than SC pigs (0.46 vs. 3.98%, P=0.02), which was associated with a trend for a greater 24-h muscle pH (5.74 vs. 5.54, P=0.07). The antioxidant blend addition in the high oxidant diet attenuated all of these effects to levels similar to SC (P>0.05), except a* value (redness) and belly firmness. Visible yellow coloration of backfat and lipofuscin in HO and VE pigs was observed at harvest at d 118. The high oxidant diet resulted in greater concentration of DHA in backfat (P<0.001); switching the diet on d 83 resulted in HO pigs having a similar fatty acid profile to SC at d 118 pigs. Vitamin E concentration in plasma and muscle was greater in HO and SC than VE, AOX, and VE+AOX on d 118. Feeding the high oxidant diet caused a series of changes in carcass characteristics and meat quality. Addition of antioxidant blend attenuated many of these, whereas the protective effects of supplemental vitamin E at 11 IU/kg were minimal during the finisher phase of the study.

Early metabolic imprinting events increase marbling scores in fed cattle.

Early weaning of calves to a high concentrate diet results in greater fat deposition and suggests early postnatal metabolic imprinting events may be exploited as a management tool to improve cattle value. Our objective was to implement a short, high energy dietary intervention before a typical grazing period to manipulate intramuscular fat deposition in finishing cattle. Fall-born, Angus-sired steer calves (n = 24) were stratified by sire and randomly assigned to normal weaned (NW) or metabolic-imprinted (MIP) treatments. At 105 ± 6d (135kg), MIP calves were transitioned to a diet containing 20% CP and 1.26 Mcal/kg NEg. Metabolic-imprinted calves were fed ad libitum as a group. Normal weaned calves remained on their dam until 253 ± 6 d of age. At this time, treatment groups were combined and grazed for 156 d on a mixed summer pasture. Following the grazing phase, steers were adapted to a corn silage-based feedlot diet and performance was monitored on 28-d intervals. Calves were staged for harvest based on backfat endpoint (target 1.0 to 1.2 cm). Metabolic-imprinted calves were heavier (P < 0.05) than NW calves (341 vs. 265 ± 4.2 kg) at normal weaning age. During the grazing phase, NW steers gained more weight than (P < 0.05) MIP steers (0.69 vs. 0.35 ± 0.03 kg/d). Feedlot performance and USDA yield grade were similar (P > 0.20) between treatments. However, MIP steers produced heavier (P < 0.05) carcasses (564 vs. 524 ± 5.6 kg) with higher (P < 0.001) marbling scores (645 vs. 517 ± 23). Therefore, calves consuming a high concentrate diet for 148 d after early weaning produced higher quality carcasses. This suggests early weaning and feeding a high concentrate before grazing is a viable strategy to increase marbling deposition compared with a traditional production system.

Moisture absorption early postmortem predicts ultimate drip loss in fresh pork.

Water-holding capacity is the ability of meat to hold moisture and is subject to postmortem metabolism. The objective of this study was to characterize the loss of moisture from muscle postmortem and investigate whether these losses are useful in predicting the ultimate drip loss of fresh pork. Cotton-rayon absorptive-based devices were inserted in the longissimus dorsi muscles of pork carcasses (n = 51) postmortem and removed at various intervals for 24h. Greatest moisture absorption was observed at 105 min post exsanguination. Drip loss varied (0.6-15.3%) across carcasses. Individual absorption at 75 min correlated (r = 0.33) with final drip loss. Correlations improved using individual absorption values at 90 min (r = 0.48) and accumulated absorption values at 150 min (r = 0.41). Results show that significant moisture is lost from muscle tissue early postmortem and suggest that capture of this moisture may be useful in predicting final drip loss of fresh meat.

Porcine satellite cells are restricted to a phenotype resembling their muscle origin.

Muscles in most domestic animals differ in function and growth potential based largely on muscle fiber type composition. Though much is known about satellite cells (SC), information is limited regarding how populations of SC differ with muscle fiber type, especially in pigs. Therefore, the objective of this study was to isolate and culture SC from red (RST) and white (WST) portions of the semitendinosus muscle of neonatal and adult pigs and determine their capacity to proliferate, differentiate, and express various myosin heavy chain (MyHC) isoforms in vitro. Porcine satellite cells were isolated from RST and WST muscles of 6-wk-old and adult (>6-mo-old) pigs and cultured under standard conditions. Muscle from neonatal pigs yielded nearly 10 times more (P < 0.001) presumptive satellite cells as those from adult pigs, with fusion percentages close to 60% for the former. The RST yielded more (P < 0.001) SC per gram muscle compared to WST, 8.1 ± 0.2 × 10(4) cells versus 6.7 ± 0.1 × 10(4) cells/gram muscle in young pigs, and 9.7 ± 0.4 × 10(3) cells versus 5.5 ± 0.4 × 10(3) cells/gram muscle in adult pigs, respectively. Likewise, satellite cells from RST proliferated faster (P < 0.001) than those from WST across both ages, as indicated by a shorter cell doubling time, 18.6 ± 0.8 h versus 21.3 ± 0.9 h in young pigs, and 23.2 ± 0.7 h versus 26.7 ± 0.9 h in adult pigs, respectively. As a result of shorter times to confluence, satellite cells from RST also formed myotubes earlier than those SC originating from WST. Once induced, however, SC from WST differentiated and fused faster (P < 0.05) as evidenced by fusion percentage within the first 24 h, 41.6% versus 34.3%, respectively; but reached similar ultimate fusion percentages similar to WST by 48 h. Over 90% of MyHC expressed in maximally fused SC cultures from both RST and WST was restricted to the embryonic isoform. Type IIX MyHC mRNA was not detected in any culture. Myotube cultures from RST expressed more (P < 0.01) Type I MyHC isoform mRNA than those from WST, whereas those cultures from WST expressed more (P < 0.05) Type II (including Types IIA and IIB) MyHC transcripts. These data show SC cultures from porcine fast and slow muscles express MyHC profiles largely reflective of their muscle of origin and suggest satellite cells are partially restricted to a particular muscle phenotype in which they are juxtapositioned. Understanding the molecular nature of these intrinsic control mechanisms may lead to improved strategies for augmenting meat animal growth or muscle regeneration.

Use of dietary supplementation with ß-guanidinopropionic acid to alter the muscle phosphagen system, postmortem metabolism, and pork quality.

Rate and extent of postmortem metabolism control pork quality development. Our objective was to evaluate the role of the phosphagen system (phosphocreatine, PCr; and creatine, Cr) on metabolism and pork quality. Muscle PCr and Cr were manipulated by feeding pigs the creatine analogue, ß-guanidinopropionic acid (ß-GPA). In experiment 1, pigs received standard (control) diet or ß-GPA supplemented (2%) diet (1 wk or 2 wk). Supplementation with ß-GPA (2 wk) decreased total Cr (PCr+Cr; P=0.02) and improved pork color (decreased reflectance, P=0.003); however, ß-GPA supplementation reduced growth performance (P=0.007). To separate effects of phosphagen system and growth, a second experiment was conducted with control, pair-fed, and 2 wk ß-GPA (1%) supplementation; pigs were also offered a control or ß-GPA supplemented flavored beverage. Neither treatment influenced pork quality. Immediately postmortem, ATP/ADP was higher in control compared to pair-fed (P<0.05); subsequently, ATP/ADP was similar among all groups. Loss of the phosphagen system may lead to adaptive changes that promote conservation of cellular ATP.

High glycolytic potential does not predict low ultimate pH in pork.

Extent of postmortem pH decline influences meat quality development. To better understand physiological determination of ultimate pH (pHu), we utilized female and castrated male pigs from a line whose selection index includes differentiated pHu. All genotypes of AMP-activated protein kinase γ3 subunit (AMPKγ3) V199I site were present. The mutant 199II genotype increased pHu, but only in castrated males. Genotype affected glycolytic potential (GP), but GP was weakly associated with pHu. A subset of animals was selected based on low (-Gly) and high (+Gly) residual glycogen content, and compared with AMPKγ3 200Q, which is associated with low pHu. Both +Gly and 200Q muscle contained glycolytic substrate at 24h; however, 200Q muscle generated low pHu and greater lactate compared to +Gly. Additionally,-Gly and +Gly groups exhibited similar pHu despite a large difference in GP. In conclusion, high GP does not appear to directly impact the extent of postmortem pH decline.

Molecular cloning and characterization of porcine calcineurin-alpha subunit expression in skeletal muscle.

The calmodulin/Ca2+-dependent serine/threonine phophatase, calcineurin (CaN), has been implicated in controlling muscle fiber phenotype. However, little information is available concerning the expression of CaN in porcine skeletal muscle. Therefore, the porcine CaN alpha (CaN-A) was cloned by reverse transcription-PCR and its expression characterized in selected porcine skeletal muscles. We successfully cloned porcine CaN gene using semitendinosus muscle (GenBank accession number AF193515). Sequence analysis showed both the full length and a 30-bp deletion splice variant in coding region of the gene reported in other species. The deduced AA sequence showed 99.4% homology with the rat CaN-A delta isoform gene. Real-time PCR analysis showed CaN is present in all tissues. However, using primers targeting the region containing the 30-bp deletion, the full length sequence is only found in skeletal muscle and brain tissues. Using a CaN-A monoclonal antibody, we localized CaN-A in porcine LM and soleus muscle and the red and white portions of the semitendinosus muscle. The CaN-A protein was abundant in fast fibers and primarily localized in the cytoplasm, whereas slow fibers expressed reduced abundance of CaN-A. Further studies are required to understand the functions of CaN-A isoform in skeletal muscle.