[18F]Sodium fluoride PET-MRI detects increased metabolic bone response to whole-joint loading stress in osteoarthritic knees.

OBJECTIVE: Altered joint function is a hallmark of osteoarthritis (OA). Imaging techniques for joint function are limited, but [18F]sodium fluoride (NaF) PET-MRI may assess the acute joint response to loading stresses. [18F]NaF PET-MRI was used to study the acute joint response to exercise in OA knees, and compare relationships between regions of increased uptake after loading and structural OA progression two years later. METHODS: In this prospective study, 10 participants with knee OA (59 ± 8 years; 8 female) were scanned twice consecutively using a PET-MR system and performed a one-legged squat exercise between scans. Changes in tracer uptake measures in 9 bone regions were compared between knees that did and did not exercise with a mixed-effects model. Areas of focally large changes in uptake between scans (ROIfocal, ΔSUVmax > 3) were identified and the presence of structural MRI features was noted. Five participants returned two years later to assess structural change on MRI. RESULTS: There was a significant increase in [18F]NaF uptake in OA exercised knees (SUV P < 0.001, KiP = 0.002, K1P < 0.001) that differed by bone region. CONCLUSION: There were regional differences in the acute bone metabolic response to exercise and areas of focally large changes in the metabolic bone response that might be representative of whole-joint dysfunction.

Effects of ractopamine, genotype, and growth phase on finishing performance and carcass value in swine: I. Growth performance and carcass merit.

A replicated factorial experiment using 183 individually fed crossbred barrows was conducted. Pigs were fed an 18.5% CP (.95% lysine) diet with 3,594 kcal of ME/kg. The effects of five genotypes (GT): 1) Hampshire (H) x (H x Duroc [D]), 2) synthetic terminal sire line, 3) (H x D) x (Landrace [L] x [Yorkshire (Y) x D]), 4) L x (Y x D), and 5) Y x L; two levels of ractopamine (RAC) treatment: 0 and 20 ppm; and three treatment weight periods (WT): 1) 59 to 100, 2) 73 to 114, and 3) 86 to 127 kg live weight on growth performance and carcass traits were evaluated. Ractopamine increased (P less than .0001) amount (FSL) and percentage (PFSL) of carcass lean standardized to 10% fat content, loin eye area (LEA), and dressing percentage (PDRES) and reduced (P less than .01) amount (DF) and percentage (PDF) of dissected fat. Magnitudes of RAC effects were smaller than those reported by other researchers. Effects of GT and WT on all growth and carcass traits were highly significant (P less than .001) except for those of WT on ADG (P less than .05) and GT on average feed intake (AFI) and backfat thickness at the last rib (BFLR; P less than .05). Genotype 3 performed better for most economically important traits than did GT 1 and 4, suggesting that heterosis existed in GT 3, which essentially was obtained by crossing GT 1 and 4. Among the three treatment periods, WT 2 had the highest ADG. As BW increased from WT 1 to 3, AFI and AFI/ADG ratio (FCR) increased and lean percentage decreased.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of ractopamine, genotype, and growth phase on finishing performance and carcass value in swine: II. Estimation of lean growth rate and lean feed efficiency.

A replicated factorial experiment using 183 individually fed crossbred barrows was conducted. The pigs were fed an 18.5% CP (.95% lysine) diet with 3.594 kcal of ME/kg. The effects of five genotypes (GT): 1) Hampshire (H) X (H X Duroc [D]), 2) synthetic terminal sire line, 3) (H X D) X (Landrace [L] X [Yorkshire (Y) X D]), 4) L X (Y X D), and 5) Y X L; two levels of ractopamine (RAC) treatment: 0 and 20 ppm; and three treatment weight periods (WT): 1) 59 to 100, 2) 73 to 114, and 3) 86 to 127 kg live weight on ADG of dissected lean (ADLG) and fat standardized lean adjusted to 10% fat content (ADSLG) and feed efficiency of ADLG (LFE) and ADSLG (SLFE) were evaluated. Initial carcass lean quantity of each individual animal was determined by a regression equation (R2 = .95) generated from 30 additional barrows (six per GT) slaughtered at 59 kg and 30 (six per GT) untreated pigs slaughtered at 100 kg average live weight. Logarithmic and reciprocal transformations of dependent variables were used to stabilize heterogeneous variances and to improve normality of the residuals. Ractopamine increased (P less than .0001) ADLG, ADSLG, LFE, and SLFE, respectively, by 19.5, 25.0, 19.6, and 25.5%. Differences (P less than .001) were observed among genotypes for all traits, showing that considerable variation existed in the data and indicating that genetic improvement can be realized through the identification and selection of superior genotypes.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of various levels of ractopamine hydrochloride on the performance and carcass characteristics of finishing swine.

Six trials involving 888 pigs (Study 1) and three trials involving 360 pigs (Study 2) were conducted at various geographical locations in the U.S. and Canada to evaluate the effect of ractopamine hydrochloride on the performance and carcass characteristics of finishing swine. All trials were conducted using a randomized complete block design. Trial data were pooled within study for statistical analysis. Pigs averaged approximately 64.5 kg (Study 1) and 65.9 kg (Study 2) initially and had ad libitum access to a 16% crude protein corn-soybean meal or barley-soybean meal diet. Ractopamine was included in the diet at 0, 2.5, 5, 10, 20 or 30 ppm (Study 1), or at 0, 5, 10, 15 or 20 ppm (Study 2); diets were fed for an average of 45 d (Study 1) and 50 d (Study 2) to a final weight of about 104.3 kg (Study 1) and 106.6 kg (Study 2). Carcass dissection data were collected in three of the six trials in Study 1 (0, 5 and 20 ppm ractopamine) and in all three trials in Study 2 (0, 5, 10, 15 and 20 ppm ractopamine). All ractopamine levels improved (P less than .05) ADG and feed: gain (Studies 1 and 2) above those of control pigs. Ractopamine levels of 10 to 30 ppm (Studies 1 and 2) improved (P less than .05) dressing percentage over controls. Pigs fed ractopamine at 5 and 20 ppm (Study 1) and 10, 15 and 20 ppm (Study 2) had increased (P less than .05) dissected leanness compared with controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Genotype and treatment biases in estimation of carcass lean of swine.

Carcasses of 181 barrows, representing five genotypes, 1) H x HD, 2) SYN, 3) HD x L[YD], 4) L x YD, and 5) Y x L (H = Hampshire, D = Duroc, SYN = synthetic terminal sire line, L = Landrace, and Y = Yorkshire), and two levels of ractopamine (RAC) treatment (0 and 20 ppm) were completely dissected and the data were used to examine genotype and treatment (RAC) biases in estimation of fat-standardized lean weight and to evaluate accuracies and precisions realized by use of equations based on variables derived from different technologies. Independent variables used to establish regression equations represented technologies of direct carcass measurements, optical probe data, TOBEC (total body electrical conductivity) readings, and dissected (DHMLN) and fat-standardized (FSHMLN) ham lean. Genotype bias existed when any equation from a single technology was used and was minimized by combining FSHMLN with one TOBEC reading, carcass length, and the probe measurement of 10th rib fat depth. Large RAC biases appeared when equations from direct carcass measurements or optical probe data were used and were minimized by an equation using either DHMLN or FSHMLN. A practical equation with relatively high R2 value and small genotype and RAC biases were developed by combining TOBEC readings with direct carcass measurements of 10th rib fat depth and warm carcass weight.

The effect of feeding ractopamine (Paylean) on muscle quality and sensory characteristics in three diverse genetic lines of swine.

The present experiment utilized Berkshire (n = 76), Duroc (n = 81), and high-lean commercial crossbred (n = 75) barrows and gilts with an initial BW of approximately 85.1 kg. Pigs were fed a standard commercial diet (17.6% CP, 1.02% lysine) supplemented with ractopamine hydrochloride at a level of 0 or 10 ppm for 28 d. The experiment was conducted in a randomized complete block design, with animals blocked within genetic line according to litter, gender, and weight, for a total of four blocks per genetic line for each treatment. Pigs were harvested at a commercial abattoir and chilled for 24 h at 1 to 4 degrees C. At 24 h postmortem, wetness and firmness scores and ultimate muscle pH were measured in the center of the longissimus muscle (LM) at the 10th to 11th rib interface. Visual and instrumental color and marbling score were measured at 48 h postmortem on a fresh cut LM surface. Percentage of chemically extracted intramuscular fat (IMF) was measured, and a trained sensory panel evaluated cooked LM chops for juiciness, tenderness, and chewiness. Cooking loss (%) and instrumental measurement of tenderness also were measured on cooked LM chops. Ractopamine treatment increased ADG (P < 0.01) and LM area (P < 0.05), but had no effect (P > 0.05) on LM quality, sensory attributes, or instrumental measures of palatability. Berkshire LM received higher tenderness and juiciness (P < 0.05) scores and had lower cooking losses (P < 0.05) and instrumental tenderness (P < 0.05) than LM from the Duroc and high-lean lines. Loins from barrows were firmer (P < 0.05), had lower drip loss percentages (P < 0.05), and received greater tenderness scores (P < 0.05) than the LM from gilts. Genetic line x treatment and gender x treatment interactions were detected for IMF. The LM of Berkshire pigs fed ractopamine had lower (P < 0.05) IMF than Berkshires fed the control diet, with no interaction in the other lines. Purebred barrows (Berkshire and Duroc) had greater (P < 0.001 and P < 0.05, respectively) IMF than their respective purebred gilts, with no gender difference in IMF in the high-lean line. Results from the present study indicate that feeding ractopamine does not affect most muscle quality and palatability characteristics. However, the genetic line x treatment interaction for loin IMF suggests that feeding ractopamine might reduce IMF within the loin muscle of genetic lines that have a propensity to produce greater levels of IMF.

Tilmicosin as a single injection treatment for respiratory disease of feedlot cattle.

Tilmicosin, a new semi-synthetic macrolide antibiotic, was evaluated in eight field trials as a single subcutaneous injection at dosages of 0 (placebo), 5, 10 and 20 mg/kg for the treatment of naturally occurring respiratory disease in feedlot cattle. Animals for these trials were selected from large groups of recently-shipped feeder cattle at the time clinical signs of respiratory disease and body temperature of 40.6 degrees C or higher were observed. Treated animals were evaluated daily for 10 days and finally at day 28. Each animal was weighed on the first day and again on day 28. Animals that died were necropsied. All treatment dosages were effective in significantly lowering mortality, improving weight gains, lowering body temperature, and reducing the severity of clinical signs when compared to the placebo-treated controls. Body temperature was the only variable with statistically significant differences among the dose levels.