Tenderness profiles of ten muscles from F1 Bos indicus x Bos taurus and Bos taurus cattle cooked as steaks and roasts.

Twenty Bos taurus (Hereford x Angus crosses) and 20 F1 Bos indicus x Bos taurus heifers of the same age, management and feeding regimen, were harvested and evaluated at 2 days postmortem for carcass and meat traits. Ten muscles were obtained from the right sides and aged until 10 days postmortem. Bos indicus carcasses were lighter, had less fat cover, smaller ribeyes, and less intramuscular lipid (all p≤0.05). Bos taurus longissimus lumborum, gluteus medius, triceps brachii, and semimembranosus muscles cooked as steaks and roasts had a lower Warner-Bratzler shear force (WBSF) (p≤0.05) than those from Bos indicus. Bos taurus deep pectoral and semitendinosus muscles cooked as roasts had a lower WBSF (p<0.05) than Bos indicus. Infraspinatus, longissimus lumborum, and semitendinosus muscles were more tender (p<0.05) as roasts than steaks, whereas the opposite was true for the deep pectoral and semimembranosus muscles. Seven of the 10 muscles had lower WBSF (p≤0.05) for Bos taurus when cooked as steaks, roasts or both.

Instrumental reflectance values of fresh pork are dependant on aperture size.

The effect of aperture size on instrumental pork color measurements was studied. Pork longissimus chops (n=30) were cut, aerobically packaged, and allowed to bloom overnight. Chops were measured once with each of four aperture ports (4.45, 2.54, 1.27, and 0.64cm diameter) on a HunterLab LabScan. Reflectance values measured with smaller aperture sizes were reduced (P<0.05) for most visual wavelengths (10nm intervals), and the percent reduction was greatest in the range of the longer, redder wavelengths. Values for L(∗), a(∗), b(∗), and saturation index were reduced (P<0.05) with decreasing aperture size under illuminants A, C, and D(65). Using illuminant A, hue angle increased (P<0.05) as aperture size decreased. For illuminants C and D(65), hue angles were similar (P>0.05) for the three largest aperture sizes, but negative a(∗) values found with the smallest aperture size skewed the hue angle data.

Effects of ascorbic and citric acid on beef lumbar vertebrae marrow colour.

Citric acid was evaluated as a way of improving ascorbic acid's ability to stabilize beef lumbar vertebrae colour in high-oxygen packaging (MAP; 80% O(2)/20% CO(2)). Vertebrae were treated with citric acid (1%, 3%, or 10%), ascorbic acid (1%, 3%, or 10%), or a combination of both. Citric acid demonstrated no positive effects (P>0.05), compared with ascorbic acid, which inhibited (P<0.05) discolouration throughout the 7d display. Although ascorbic acid inhibited discolouration (visual colour and a(∗); P<0.05), 3% and 10% ascorbic acid were most effective. However, if vertebrae are displayed for less than 7d, there may be no significant colour-stabilizing advantages associated with increasing ascorbic acid from 3 to 10%. The significant oxidizing effects of citric acid at 10% were reversed (P<0.05) by ascorbic acid. Combining citric and ascorbic acid had no synergistic affect (P>0.05) on vertebrae colour.

A comparison in the composition of recovered meat produced from beef neckbones processed using hand boning, a traditional Advanced Meat Recovery (AMR) system, and a Desinewated Minced Meat system.

Beef neckbones were processed through a traditional Advanced Meat Recovery system (TAMR), a Desinewated Minced Meat machine with/without prior use of Jarvis saw for removal of spinal cord (DMMJ/DMMNJ), or hand boned with/without Jarvis saw (HJ/HNJ). This study investigated the composition of meat recovered by these five methods. Ranking from the most to least total fat percentage was TAMR (22.02%), HNJ (18.37%), HJ (14.69%), DMMNJ (11.14%), and DMMJ (9.76%); higher fat was related to less moisture. Protein was most for HJ (18.32%) and least for TAMR (15.79%). TAMR and HJ were similar (P>0.05) in ash content. Calcium was most in DMMJ (79.81mg); the least was found in the hand boned (HJ, 20.86mg/100g and HNJ, 23.66mg) lean. All samples contained calcium below the required limits set by USDA-FSIS. Total iron was the highest in TAMR (5.28mg of iron/100g), followed by DMMJ (3.65mg), DMMNJ (3.46mg), HJ (2.77mg), and HNJ (2.18mg).

Comparison of ascorbic acid and sodium erythorbate: Effects on the 24h display colour of beef lumbar vertebrae and longissimus lumborum packaged in high-oxygen modified atmospheres.

Sodium erythorbate and ascorbic acid were compared as a means to stabilize surface colour of bone-in beef steaks in high-oxygen modified atmosphere (80% oxygen and 20% carbon dioxide). Bone-in strip loins (n=8) were fabricated into 1.9-cm thick steaks, of which both the lumbar vertebrae and longissimus lumborum were topically treated with either ascorbic acid or sodium erythorbate (0, 0.05, 0.1, 0.5, 1.0, or 1.5%, wt/wt basis). Colour (L(∗)a(∗)b(∗)) was evaluated before treatment and 24h after packaging (display at 1°C). Sodium erythorbate was as effective as ascorbic acid for inhibiting vertebrae discolouration (P>0.05). Either reducing agent at 0.5, 1.0, or 1.5% improved (P<0.05) vertebrae redness (compared with 0%, 0.05% and 0.1%). No detrimental effects on muscle colour were observed. When selecting antioxidants intended for bone-in beef steaks displayed in high-oxygen packaging, sodium erythorbate may be a cost effective substitute for ascorbic acid.

Effects of polyvinyl chloride overwrap film, high-oxygen modified atmosphere packaging, or ultra-low-oxygen modified atmosphere packaging on bone marrow discoloration in beef humerus, rib, thoracic vertebra, and scapula.

Meat retailers have reported bone marrow discoloration to be a problem, especially in modified atmosphere packages (MAP). Therefore, it is important to determine the prevalence and cause(s) of bone marrow discoloration in different beef bones and packaging systems. Thirty-six beef humeri, ribs, scapulas, and thoracic vertebrae from USDA Select and Choice carcasses were obtained from a commercial abattoir, cut into 2.54-cm-thick sections at 4 d postmortem, and packaged into 1 of 3 systems: 1) polyvinyl chloride film (PVC) overwrap; 2) high-oxygen (80% O2, 20% CO2) MAP; and 3) ultra-low-oxygen (70% N2, 30% CO2) MAP. Instrumental reflectance and visual color scores were taken on d 0, 2, and 4, and on d 0 to 4 of display, respectively. Bone marrow was extracted from humeri, ribs, and thoracic vertebrae for analysis but not from scapulas. Ribs, scapulas, and thoracic vertebrae packaged in PVC and high-oxygen MAP developed undesirable gray or black discoloration. In ultra-low-oxygen MAP, mean visual color scores were acceptable throughout the entire display period. Discoloration (darkening) was more extensive for ribs, scapulas, and thoracic vertebrae than for humeri, especially for bones packaged in PVC and high-oxygen MAP. Humeri had lower (P < 0.05) a* values (larger positive a* values indicate a redder color) than the other bones. The a* values for ribs, scapulas, and thoracic vertebrae decreased (P < 0.05) over time. Chroma showed that bone marrow discolored during display, but graying was dramatically less for all bones packaged in ultra-low-oxygen MAP and for humeri in PVC and high-oxygen MAP. Humeri marrow had lower (P < 0.05) 2-thiobarbituric acid reactive substances (TBARS) than did ribs and thoracic vertebrae marrow. Ultra-low-oxygen MAP resulted in the least amount of change in TBARS from d 0 to 4, whereas thoracic vertebrae marrow had greater (P < 0.05) TBARS values at d 4 of display than at d 0 in PVC and high-oxygen MAP. Humeri marrow had dramatically less total Fe and hemoglobin than did that of ribs and thoracic vertebrae for all packaging systems. Myoglobin was undetectable in humeri marrow. The much larger amounts of Fe and hemoglobin in ribs and thoracic vertebrae likely contribute to marrow discoloration. Bone marrow discoloration was distinct in ribs, scapulas, and thoracic vertebrae packaged in PVC or high-oxygen MAP. Bones packaged in ultra-low-oxygen MAP had minimal discoloration.

Effects of ascorbic acid, rosemary, and Origanox™ in preventing bone marrow discoloration in beef lumbar vertebrae in aerobic and anaerobic packaging systems.

Treatments of 1.25% or 2.5% ascorbic acid (AA); 0.1% or 0.2% rosemary; or a combination of 0.15% Origanox™+0.3% AA on beef lumbar vertebrae (n=72) were evaluated for their effectiveness in preventing bone discoloration in retail packages. Vertebrae were held either 6 or 14d postmortem; cut into 2.54-cm sections; and packaged into either polyvinyl chloride film overwrap (PVC), high-oxygen (80% O(2)/20% CO(2)) modified-atmosphere packages (MAP), or ultra-low-oxygen (70% N(2)/30% CO(2)) MAP. Controls and vertebrae treated with 0.1% or 0.2% rosemary discolored significantly, whereas 0.15% Origanox™+0.3% AA was effective through d 2 of display in PVC and high-oxygen MAP. In both high- and ultra-low-oxygen MAP, 1.25% AA was as effective as 2.5% AA in preventing bone discoloration. Vertebrae treated with AA or packaged in ultra-low-oxygen MAP had the largest a* values over display time. Bone discoloration was effectively prevented with AA, especially at the 2.5% concentration.

Beef quadriceps hot boning and modified-atmosphere packaging influence properties of injection-enhanced beef round muscles.

Two experiments were conducted to examine the effects of hot boning, modified atmosphere packaging, and injection enhancement on the oxidative and sensory properties of beef round muscles. The beef knuckle (quadriceps muscles) was partially hot boned within 1.5 h postmortem from one randomly selected side of each beef carcass (n = 14), whereas the quadriceps on the opposite side remained intact throughout a 48-h chilling period. At 5 d postmortem, biceps femoris, semimembranosus, vastus lateralis, and rectus femoris muscles from both hot- and cold-boned sides were injected with an enhancement solution consisting of water, salt, phosphate, and natural flavorings (rosemary) at either 6 (Exp. 1) or 10% (Exp. 2) of fresh muscle weight. Enhanced muscles were then processed into 2.54-cm-thick steaks, which were allotted randomly to high-oxygen (HiOx; 80% O2:20% CO2) or ultra-low oxygen (LoOx; 80% N2:20% CO2) modified atmosphere packaging. Regardless of hot boning or enhancement, steaks packaged in LoOx had lower thiobarbituric acid-reactive substances values (P < 0.05), more beef flavor intensity (P < 0.05), fewer off flavors (P < 0.05), and were more tender (P < 0.05) than steaks packaged in HiOx. Hot boning the knuckle had no effect on oxidative (P > or = 0.99) and sensory properties (P > or = 0.85). Increasing the level of injection enhancement from 6 to 10% introduced more rosemary and phosphate into the muscles, thereby decreasing the extent of oxidation, but also imparting a nontypical beef flavor. Packaging in LoOx atmosphere offered the optimal result of decreased oxidation and improved tenderness, without detriment to flavor. Injection enhancement (both 6 and 10%) created off-flavors attributable to the enhancement solution; however, the 10% injection seemed to offer more resistance to lipid oxidation.

Exclusion of oxygen from modified atmosphere packages limits beef rib and lumbar vertebrae marrow discoloration during display and storage.

Visual and instrumental color (L*a*b* and reflectance from 400 to 700 nm) were used to evaluate packaging atmosphere as a way of minimizing beef marrow discoloration. In experiment 1, rib ends (n=24) packaged in 80% O(2)/20% CO(2) discolored more than ribs packaged in 100% N(2), which resulted in a relatively stable purplish marrow color through a 7-day display at 1 °C. In experiment 2, lumbar vertebrae (n=10) packaged in 80% O(2)/20% CO(2) had a rapid and significant discoloration within 24 h after packaging, likely because of the formation of methemoglobin. Conversely, vertebrae packaged in 80% N(2)/20% CO(2) and 0.4% CO/30% CO(2)/69.6% N(2) remained color stable during 2 and 6 weeks of storage at 4 °C, respectively. Exclusion of oxygen from MAP packages and the addition of low concentrations of CO minimized beef rib and lumbar vertebrae discoloration compared with high-oxygen MAP.

Accelerated chilling and modified atmosphere packaging affect colour and colour stability of injection-enhanced beef round muscles.

Beef knuckles were partially hot-boned within 1.5 h postmortem. Biceps femoris (BF), semimembranosus (SM), vastus lateralis (VL), and rectus femoris (RF) muscles were injection enhanced at 6% (experiment 1) or 10% (experiment 2) of non-injected weight and packaged in a high- (HiOx; 80% oxygen and 20% carbon dioxide) or ultra-low oxygen (LoOx; 80% nitrogen and 20% carbon dioxide) modified atmosphere. Hot boning accelerated chilling in all beef round muscles investigated. This resulted in a darker initial beef colour and darker visual colour during display for the BF, RF, and VL, as well as more uniform BF and knuckle steak colour. RF and VL, in experiments 1 and 2, respectively, had the most improved colour and colour stability. Steaks in HiOx MAP had longer colour life in display than steaks that had been in LoOx. Partially removing the beef knuckle early postmortem is a practical process that will improve colour and colour stability of beef round muscles.

Ascorbic acid minimizes lumbar vertebrae discoloration.

Ascorbic acid was evaluated as a way of preventing bone discoloration. In experiment 1, beef bone-in t-bone steaks (lumbar vertebrae and longissimus) were treated with 0%, 0.05%, 0.1%, 0.5%, 1.0%, or 1.5% ascorbic acid (n=10). Vertebrae and muscle color (L(*)a(*)b(*)) were evaluated initially and after 24 h in 80% O(2)/20% CO(2). Vertebrae treated with 0%, 0.05%, or 0.1% ascorbic acid significantly discolored while the longissimus maintained a bright-red appearance. Ascorbic acid treatments 0.5%, 1.0%, and 1.5% significantly minimized vertebrae discoloration and neither induced nor prevented longissimus discoloration. In experiment 2, lumbar vertebrae were treated with 0%, 0.05%, 1.5%, or 2.5% ascorbic acid (n=15), packaged in 80% O(2)/20% CO(2), and displayed for five days (1 °C). Visual color was evaluated daily by a trained panel. Ascorbic acid treatment at 1.5% or 2.5% minimized lumbar vertebrae surface discoloration. Through a five-day display at 1 °C, lumbar vertebrae with 2.5% ascorbic acid had the least bone discoloration.

Reflectance at 610 nanometers estimates oxymyoglobin content on the surface of ground beef.

This research evaluated the utility of direct (K/S 610÷K/S 525) and indirect (100%-% deoxymyoglobin+% metmyoglobin) methods for estimation of oxymyoglobin (OMb) on the surface of ground beef. Direct estimation was highly correlated to visual color scores (r=-0.93), indirect determination of OMb (r=0.98), and % metmyoglobin (r=-0.98). Since indirect OMb was based partially on % deoxymyoglobin, which was poorly correlated to visual color scores, the accuracy of the subtraction method may be limited. Both direct and indirect methods produced similar variability when estimating OMb. All calculations for pigment forms produced outliers, which were adjusted to 0 and 100% to more precisely represent surface pigment concentrations. This work suggests that the K/S 610÷K/S 525 method is accurate and repeatable and can be used to quantify surface OMb concentration and discoloration of ground beef.

Effects of omitting vitamin and trace mineral premixes and(or) reducing inorganic phosphorus additions on growth performance, carcass characteristics, and muscle quality in finishing pigs.

Three experiments were conducted to determine the effects of omitting vitamin and trace mineral premixes and(or) reducing inorganic phosphorus additions to finishing diets on growth performance, carcass characteristics, and muscle quality in pigs. In Exp. 1, a corn-soybean meal-based diet (.70% lysine, .65% Ca, and .55% P) was used as the control. Pigs (n = 128; average initial BW of 85.7 kg) were fed the control diet or the control diet without 1) the vitamin premix, 2) the trace mineral premix, or 3) both premixes. Omitting the premixes had no effect on ADG (P>.39); gain/feed (P>.17); carcass backfat thickness (P>.42); and marbling, color, and firmness of the longissimus muscle (P>.11). In Exp. 2, pigs (n = 128; average initial BW of 86.2 kg) were fed the control diet (.65% Ca and .53% P) used in Exp. 1 and the control diet without 1/3 (.56% Ca and .46% P), 2/3 (.51% Ca and .40% P), or all (.47% Ca and .31% P) of the added monocalcium phosphate (MCP). Omitting up to 2/3 of the MCP increased ADG (quadratic effect, P<.02) and had no effect on meat quality (P>.12), but backfat thickness increased slightly (quadratic effect, P<.02). In Exp. 3, pigs (n = 160; average initial BW of 86.6 kg) were fed the control diet used in Exp. 1 or the control without 1) the vitamin and trace mineral premixes, 2) 2/3 of the MCP, or 3) the premixes and 2/3 of the MCP. Treatment had no effects on ADG (P>.23), gain/feed (P>.94), stomach lesions (P>.37), or serum gamma globulins (P>.08). In conclusion, vitamin and trace mineral premixes and up to 2/3 of the supplemental MCP can be omitted during late finishing (i.e., approximately the final 30 d) to reduce nutrient excesses that increase cost of feeding and nutrients excreted in waste material.

The use of urea dilution for estimation of carcass composition of Holstein steers at 3, 6, 9, and 12 months of age.

Every 3 mo for a 2-yr period, two weaned Holstein steer calves (94.5 kg) were randomly assigned to each of four slaughter age groups (3, 6, 9, and 12 mo). Urea dilution was performed before slaughter, and urea space (US) was calculated as total volume and as a percentage of body weight (BW) and empty body weight (EBW). The relationships between US (kg, % EBW and % BW), BW, and EBW and carcass soft tissue composition (protein, fat, moisture, and ash) were studied. One- and two-pool models were fitted using the urea dilution data and the coefficients of those equations (zero time, A + B), and the intercepts of compartments A and B were used to estimate body volume. Body weight and EBW effectively predicted the amount of water, fat, and protein in the carcass soft tissue. Equations expressed in kilograms were more accurate than those expressed as percentages. Urea space overestimated body water, probably because of the fast rate of urea disappearance in plasma. Correlation coefficients between US and carcass soft tissue water (kg) based on the pooled data ranged from .74 at 6 min to .48 at 42 min after infusion. The biexponential models coefficients explained more of the variation of carcass soft tissue composition than US; correlation coefficients using volume B and the soft tissue composition (in kg) with pooled data were .78 (water), .68 (fat), .69 (ash), and .76 (protein). The relationships between A and soft tissue composition were weaker (water .59, fat .51, ash .58 and protein .59). The highest correlation coefficients were obtained when A + B was used for water, fat, ash, and protein (.83, .70, .74 and .81, respectively). Equations combining BW, EBW, and two-model coefficients (A, B, A + B) explained much of the variation of soft tissue composition. No significant benefit was found in using the urea space at various times after infusion over BW or EBW alone to estimate carcass soft tissue composition in Holstein steers.

Effects of high intensity ultrasound treatment, storage time and cooking method on shear, sensory, instrumental color and cooking properties of packaged and unpackaged beef pectoralis muscle.

Beef pectoralis muscles were removed at 24 h post mortem from nine steers, and samples were vacuum packaged and exposed to high-intensity ultrasound (20 kHz, 22 W/cm(2)) for 0, 5 or 10 min, then aged for 1, 6 or 10 days before evaluation of purge and cooking losses, instrumental shear and color and sensory traits (Experiment 1). For Experiment 2, unpackaged beef pectoralis muscle samples from eight steers were subjected to ultrasonic cooking, boiling, convection cooking or ultrasound treatment for 5 or 10 min followed by cooking in a convection oven. Neither duration of sonication nor storage of packaged pectoralis muscles affected (p > 0.05) storage purge or cooking losses, shear properties or sensory characteristics (Experiment 1). However, muscles receiving ultrasonic treatment showed tendencies for reduced peak force and total work to shear. Increased length of storage caused pectoralis muscles to become more vivid red-orange colored (p < 0.05), whereas ultrasonic treatment caused muscles to become less vivid, less red and more orange colored (p < 0.05). Ultrasonically cooked pectoralis muscles (Experiment 2) had lower (p < 0.05) cooking losses than muscles cooked by other methods. Both ultrasonic cooking and boiling were faster than convection cooking only and ultrasound exposure followed by convection cooking. Additional studies are needed to verify the ability of ultrasound to promote improved cooking, sensory and shear properties of muscle.

Microbiological Quality of Beef Subprimals as Affected by Lactic Acid Sprays Applied at Various Points during Vacuum Storage.

Beef strip loins were sprayed with 1.5% (vol/vol) lactic acid before and/or after 14, 28, 56, 84, and 126 days of vacuum-packaged storage at -1.1 or 2°C to assess the effects on bacteria. Five different treatment combinations including a control (no spray treatment) and one treatment with prestorage acid spray followed by poststorage water spray (A/W) were evaluated. Compared to the controls, 97% of all acid-treated loins had lower microbial counts throughout the storage period. Prestorage acid spray (A/0) was more effective than poststorage acid spray (0/A)with the greatest effects (P < 0.05) being observed on day 28, where the bacterial population was reduced by 1.9 and 1.5 log CFU/cm2 for loins stored at -1.1 and 2°C, respectively. Microbial counts for loins with A/A(acid spray both before and after vacuum storage) or A/W treatments were lower than but not significantly different from A/0 (P > 0.05). Poststorage washing resulted in a minimal decontaminating effect, irrespective of the washing agent used. In addition, single spray treatment immediately after fabrication seems more effective and practical than a double spray. Temperature main effects showed that colder temperature (-1.1 versus 2°C) reduced (P < 0.03) microbial growth throughout the storage period. Salmonella contamination was not detected in any samples; however, 28% of the control and 4% of the spray-treated loins were positive for Listeria spp. Appropriate time of acid application in combination with colder storage temperature improved the microbiological quality of meat for at least four weeks.

Effects of modified gas atmosphere packaging on pork loin colour, display life and drip loss.

Boneless loins from both sides of 20 pig carcasses were divided into five sections each and assigned equally to five packaging treatments: 100 % CO(2); 50 % CO(2)/50 % N(2); 25 % CO(2)/ 75 % N(2); 25 % CO(2)/65 % N(2)/10 % O(2) and vacuum. Loin sections were packaged in bags of low O(2) permeability, then stored in darkness at 1 °C for up to 22 days. Retail chops were cut from the sections and displayed in oxygen-permeable film under light at 3 °C for 3 additional days. The O(2) concentrations in packages with nominally anoxic atmospheres were 0.1-0.4 %. Sections stored in 25 % CO(2)/65 % N(2)/10 % O(2) had more surface greying and greening, stronger off-odour and psychrotropic counts after storage were more than one log(10) higher compared to sections from the other four treatments. Displayed chops from sections stored in 25 % CO(2)/65 % N(2)/10 % O(2) also had greying/greening at an outer layer of the chops. Off-odour of chops was most pronounced for treatments with 10 % O(2) and vacuum. Drip loss from loin sections was highest for those in 100 % CO(2) (4.2 %) and lowest for those in vacuum (3.2 %). In conclusion, storage in CO(2) or CO (2)N (2) atmospheres benefitted the overall shelf life of pork.

The effect of dietary lysine on growth, carcass composition, and lipid metabolism in high-lean growth gilts fed from 72 to 136 kilograms.

One hundred fourteen high-lean growth gilts (72.5 kg BW) were used to determine the apparent digestible lysine requirement for maximum growth performance and carcass protein deposition rate from 72.5 to 136 kg BW. The experiment was a randomized complete block design with initial BW used to establish blocks. Six dietary treatments were included, ranging from .44 to .94% (.10% increments) apparent digestible lysine (.62 to 1.13% total lysine) with six replicate pens per treatment and three pigs per pen. Pig weights and feed consumption were collected weekly to determine ADG, ADFI, and gain: feed ratio (G/F). Six gilts were slaughtered at 72.5 kg BW to determine initial carcass composition. When the mean weight of pigs in a pen reached 104 or 136 kg, one pig per pen was selected (closest to 104 or 136 kg, respectively) and slaughtered for determination of carcass measurements and composition. From 72.5 to 104 kg and from 104 to 136 kg, ADG and G/F increased (linear, P < .05; quadratic, P < .10, respectively) as apparent digestible lysine increased. From 72.5 to 136 kg, G/F increased (quadratic, P < .10) as apparent digestible lysine increased. Average backfat thickness and longissimus muscle area at 104 kg were not influenced (P > .10) by apparent digestible lysine. However, average backfat thickness increased (quadratic, P < .05) with increasing digestible lysine for gilts slaughtered at 136 kg. Carcass CP accretion was not influenced (P > .10) from 72.5 to 104 kg but tended to increase (linear, P < .10) from 72.5 to 136 kg as digestible lysine increased. Plasma and longissimus muscle cholesterol concentrations were unaffected (P > .10) by increasing digestible lysine. These results suggest that high-lean growth gilts require greater dietary lysine than current NRC (1988) estimates to maximize ADG, G/F, and carcass CP accretion from 72.5 to 104 and from 104 to 136 kg.

Influence of dietary lysine on growth and carcass composition of high-lean-growth gilts fed from 34 to 72 kilograms.

One hundred eight high-lean-growth gilts (34.4 kg BW) were used to determine the dietary lysine requirement to maximize growth, carcass characteristics, and protein accretion from 34 to 72.5 kg BW. The experiment was a randomized complete block design; initial BW served as the blocking factor. Six dietary treatments were included, ranging from .54 to 1.04% (.10% increments) digestible lysine (.69 to 1.25% total lysine). Pigs were housed in pens of three, with six replicate pens per treatment. Pig weights and feed consumption were collected weekly to calculate ADG, ADFI, and gain:feed (G/F). Initially, five pigs were slaughtered to determine baseline carcass composition. When the mean weight for pigs in a pen reached 55 and 72.5 kg, one pig per pen was randomly selected and slaughtered for carcass measurements. The right side of each carcass was ground twice and sampled to determine carcass composition and tissue accretion rates. Average daily gain was increased by dietary lysine from 34 to 55 kg (linear, P < .01), from 55 to 72.5 kg (linear, P < .10), and from 34 to 72.5 kg (linear, P < .01). Although ADFI from 34 to 55 and from 55 to 72.5 kg was not influenced by dietary lysine, ADFI for the entire experiment tended to decrease (quadratic, P < .10) as digestible lysine increased. Increased dietary lysine resulted in improved G/F from 34 to 55 kg (linear, P < .01) and from 55 to 72.5 and 34 to 72.5 kg (quadratic, P < .01). Average backfat thickness was not influenced by dietary lysine at 55 kg but decreased (linear, P < .05) as dietary lysine increased at 72.5 kg. At 55 kg, longissimus muscle area was larger (linear, P < .05) for gilts fed increased digestible lysine. However, longissimus muscle area was similar for all treatments at 72.5 kg. Gilts fed increased digestible lysine had greater CP accretion from 34 to 55 kg (linear, P < .01), 55 to 72.5 kg (linear, P < .05; quadratic, P < .10), and from 34 to 72.5 kg (quadratic, P < .05). Based on the feed intake observed in this study, the high-lean-growth gilt requires at least 22 g/d total lysine intake from 34 to 72.5 kg to maximize CP accretion.

The effects of porcine somatotropin and dietary lysine on growth performance and carcass characteristics of finishing swine fed to 105 or 127 kilograms.

One hundred twenty barrows (initially 59 kg) were used to determine the effects of dietary lysine and porcine somatotropin (pST) on growth performance and carcass characteristics of finishing pigs fed to heavy market weights (127 kg). Pigs were injected daily with either 4 mg of pST or a placebo and fed diets containing either .8, 1.0, 1.2, or 1.4% lysine in a 2 x 4 factorial arrangement. Performance data were collected and evaluated for the weight ranges: 59 to 105, 105 to 127, and 59 to 127 kg. In addition, daily accretion rates of protein (DPA), lipid (DLA), moisture, and ash were determined by slaughtering six randomly selected pigs at the start of the experiment, then one pig per pen when pigs reached mean weights of 105 and 127 kg. Pigs injected with pST had greater (P < .05) ADG than control pigs at all weight ranges. Increased dietary lysine had no effect (P > .20) on ADG during the entire trial (59 to 127 kg). Although control pigs showed no increase in ADG with increasing lysine, ADG of pST-treated pigs tended to increase. This resulted in a pST x lysine interaction (P < .07) for ADG from 59 to 127 kg. Feed consumption decreased (P < .05) in pigs from 59 to 105 kg and 59 to 127 kg with pST treatment and with increasing dietary lysine. Feed conversion (G/F) was improved (P < .01) by pST administration and a tendency for a pST x lysine interaction (P < .12) was observed. At 105 kg, average backfat thickness, kidney fat, longissimus muscle area, and DPA were unaffected by dietary lysine but were improved by pST treatment (P < .01). At a slaughter weight of 127 kg, average backfat thickness decreased and DPA increased (linear, P < .05) with increasing dietary lysine and pST treatment (P < .01). Longissimus muscle area was increased and DLA was decreased (P < .01) by injections of pST but both were unchanged by dietary lysine. These data indicate that growth performance and carcass characteristics at 105 and 127 kg were improved by daily administration of 4 mg of pST. At both slaughter weights, increasing dietary lysine resulted in increased carcass leanness (increased carcass protein and decreased carcass lipid). Although increasing lysine did not improve overall (59 to 127 kg) ADG and feed efficiency, pST-treated pigs showed a greater response to increasing dietary lysine. The data indicate that pST-treated pigs (4 mg/d) require approximately 28 g/d of lysine.