Animal science departments of the future.

Departments of animal science were established in agricultural colleges of public universities just over 100 yr ago, shortly before the founding of today's American Society of Animal Science. These departments and colleges have been remarkably resilient, changing little structurally. Yet, the future portends significant changes in these departments and colleges in response to shifts in how public higher education is financed and how society views the roles of animals in providing food and companionship. Funding for public higher education will continue to decline as a percentage of government appropriations. Public universities will garner more funding from gifts, endowments, grants, contracts, and tuition but will be held more accountable than today by public officials. Departments of animal science will retain strong constituencies and will be major units of most agricultural colleges; however, their students and faculty will be more diverse. Departments of animal science will focus on more species of animals and on a greater role of animals in society. Disciplines of faculty members in departments of animal science will become broader, and research projects will be more complex and have longer horizons, ultimately focused more on sustainability. Departments will share more resources across state and national boundaries, and there will be less duplication of effort regionally. Departments of animal science will continue to be important academic units of universities into the 22nd century.

Relationships among intramuscular collagen, serum hydroxyproline and serum testosterone in growing rams and wethers.

Concentration and maturation of collagen and serum concentrations of hydroxyproline and testosterone were determined in growing rams and wethers to characterize developmental changes in collagen associated with a representative testicular steroid. Groups of eight rams and eight wethers were slaughtered at 12, 18, 24 and 30 wk of age. Concentrations of collagen in longissimus, supraspinatus and infraspinatus muscles and serum hydroxyproline were greater (P less than .05) in rams than in wethers at all ages. Collagen stability, as measured by collagen solubility and thermal shrinkage temperature, was greater (P less than .05) in wethers than in rams. Differences in collagen stability and serum hydroxyproline concentration indicated that collagen synthesis and turnover were more rapid in rams than in wethers. Serum hydroxyproline decreased (P less than .05) and collagen solubility decreased (P less than .05) with age, indicating that collagen turnover was occurring most rapidly in 12-wk-old lambs and that collagen maturation was predominant in 24- to 30-wk old lambs. Testosterone parameters measured in rams were unrelated within groups to collagen characteristics, possibly reflecting the high variability in testosterone secretion and the slow development of collagen. However, rams as young as 12 wk of age were under the influence of testosterone, and differences in collagen between rams and wethers were apparent at that time.

Effects of early post-mortem ageing on intramuscular collagen stability, yield and composition.

Post-mortem changes in the composition and physical stability of bovine intramuscular collagen were evaluated during a 24 h ageing period. The yield of intramuscular connective tissue (IMCT) isolated from the infraspinatus muscle samples and the carbohydrate content of that material did not change significantly (P > 0·05) during the ageing period. The collagen content and total protein content of the isolated IMCT increased (P < 0·05) through 8 h post-mortem. Moisture content of the isolated material decreased numerically but not significantly (P > 0·05). Collagen thermal shrinkage temperature (T(s)) decreased (P < 0·01) and collagen solubility increased (P < 0·05) during the ageing period with most of the changes occurring in the first 8 h.

Collagen stability, testosterone secretion and meat tenderness in growing bulls and steers.

Interrelationships among concentrations and maturation of intramuscular collagen, serum concentration of hydroxyproline and testosterone and meat tenderness were determined in growing bulls and steers. Sixty-four Charolais X Angus bulls were assigned to sex treatment groups (intact or castrate) and slaughter groups (9, 12, 15 or 18 mo of age). Animals were bled at 30-min intervals via intrajugular catheters between 0600 and 1400 beginning 48 h before slaughter. Serum concentrations of testosterone were determined in each sample from bulls and from four samples from steers; serum hydroxyproline was determined in the last sample from both sexes. Testosterone mean values for the collection period were calculated. Samples of the longissimus, semitendinosus and infraspinatus muscles secured within 45 min postmortem were analyzed for intramuscular collagen concentration, percent soluble collagen and collagen thermal shrinkage temperature. Tenderness of loin steaks was determined by Warner-Bratzler shear test. Serum concentrations of hydroxyproline and testosterone were higher (P less than .01) in bulls than steers. Age effects were noted for both hydroxyproline (P less than .01) and testosterone (P less than .06). Total intramuscular collagen was greater (P less than .01) in bulls than steers and was different (P less than .01) among muscles, but the muscle differences were not uniform over all ages (P less than .05). Percent soluble collagen declined (P less than .01) with age and was different (P less than .01) among muscles. Interaction of age and muscle (P less than .01) and age and sex (P less than .05) also were noted for percent soluble collagen.(ABSTRACT TRUNCATED AT 250 WORDS)

Muscle protein turnover in sex-linked dwarf and normal broiler chickens.

Dietary infusion of L-[U-14C]tyrosine was used to estimate the fractional protein synthesis rates (FSR) in normal and dwarf female broiler chicks. Five 2-week-old and five 3-week-old birds of each genotype were placed in individual metabolism cages and given a purified diet in agar-gel containing 2 mu Ci L-[U-14C]tyrosine for 6 hr. Birds were killed and the pectoralis major (PM) and combined gastrocnemius and peroneous longus muscles (LM) were removed for analyses. Additional groups of 4 to 5 chickens were killed 3 days before and 3 days after each infusion to determine fractional protein accretion rate (FAR) over the 6-day period. Fractional degradation rate (FDR) was obtained by difference (FDR = FSR - FAR). Protein, ribonucleic acid (RNA), and deoxyribonucleic acid (DNA) concentrations were determined to observe possible relationships between these cellular constituents and FSR. Activities of RNA and DNA were determined as units of protein synthesized per unit RNA or DNA per day. Two-week-old chicks, dwarf chicks, and the PM muscles had higher (P less than .05) FSR than 3-week-old chicks, normal chicks, and the LM, respectively. Two-week-old chicks and dwarf chicks had higher FDR than 3-week-old chicks, respectively. There was a significant decrease in RNA concentration and RNA activity from 2 to 3 weeks. The RNA activity tended to be higher in dwarf than normal birds. Concentration of RNA was higher (P less than .05) in the PM than LM. However, DNA concentration was higher (P less than .05) in the LM than PM.(ABSTRACT TRUNCATED AT 250 WORDS)

Estimation of the fractional breakdown rates of myofibrillar proteins in chickens from quantitation of 3-methylhistidine excretion.

The objective of this study was to estimate the fractional breakdown rate (FBR) of muscle protein in the chicken from measurements of 3-methylhistidine (3-Mehis) excretion and the amount of 3-Mehis bound in the skeletal muscle pool. Excreta were collected for a 24-hr period from six 2-week-old broiler chicks that were fed a purified diet, and 3-Mehis was quantified. The concentration of 3-Mehis was determined in the dissected tissues of skeletal muscle, heart, gizzard, intestine, crop, stomach, brain, lung, kidney, liver, skin, feathers, and skeleton. Detectable amounts of 3-Mehis were not found within serum either before or after acid hydrolysis. Heart, gizzard, intestine, crop, and stomach contained considerable amounts of 3-Mehis, but because of their small contribution to body weight, they contributed only 11% of the total body 3-Mehis. Muscle contributed 84% of the 3-Mehis in the body. Muscle protein FBR determined from 3-Mehis excretion was 5.3%/day, about half that estimated using continuous infusion methods. The difference between the two quantification methods was attributed to the slow turnover rate of actin, which contains most of the 3-Mehis.

Skeletal muscle protein turnover in broiler and layer chicks.

Dietary infusion of L-[U-14C]tyrosine was used to estimate the fractional protein synthesis rates (FSR) in broiler and layer chickens. Six 2-wk-old birds of each strain were placed in individual metabolism cages and given a purified diet in agar-gel containing 2 microCi L-[U-14C]tyrosine for 6 h. The birds were sacrificed and the pectoralis major (PM) and two combined leg (LM) muscles (gastrocnemius and peroneous longus) were removed for analysis. Subgroups of chickens were sacrificed 3 d before and 3 d after infusion to observe changes in muscle composition to calculate fractional protein accretion rates (FAR). Fractional protein breakdown rates (FBR) were calculated by difference (FBR = FSR-FAR). Protein, ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) concentrations were determined to observe relationships between these cellular constituents and FSR. Fractional whole body growth rate and FSR in PM was greater (P less than .05) in broiler than layer birds. The FSR in LM of the layer was not different (P greater than .05) from that of broilers, and from the FSR of the PM in each bird-type. The calculated FBR in the layer PM was at least 17% higher than that of the other muscles. Ratios of FSR to FBR indicated that 16% of the protein synthesized in the layer PM was retained, compared with 45% in the broiler PM. The RNA activity of the layer PM was less (P less than .05) than that of the other muscles investigated. Deoxyribonucleic acid activity was lower (P less than .05) in the PM than LM of either bird-type.(ABSTRACT TRUNCATED AT 250 WORDS)

Antioxidative activity of α-tocopherol in cooked and uncooked ground pork.

The effect of α-tocopherol (0, 100, 200 ppm) on lipid oxidation either in cooked or uncooked ground pork was studied during aerobic storage at 4°C and -20°C. Lipid oxidation was measured using the 2-thiobarbituric acid (TBA) method and rancidity development was scored by a trained sensory panel. Alpha-tocopherol slowed the rate of oxidation in cooked ground pork stored at either 4°C or -20°C and uncooked samples refrigerated for extended periods of time (12 days). In cooked product stored at 4°C where oxidation development was intense and off-flavors were strong, panelists did not detect flavor differences due to treatments. But in cooked product stored at -20°C sensory results were consistent with TBA analysis. Pre-rigor grinding, known to induce a high pH and inhibit lipid oxidation in uncooked fresh pork, had no protective effect on lipid oxidation as measured by TBA values in cooked ground pork, regardless of storage condition. TBA numbers increased during storage of cooked product at 4°C with an increase in internal cooking temperature between 50°C and 80°C. Internal cooking temperatures of 70°C or higher induced a rapid rate of oxidation when stored at 4°C.

Genetic parameters and cellularity of adiposity in layer-type chickens.

Genetic parameters concerning weight of abdominal fat pads were determined for a randombred layer-type population. Progeny by the upper (U) and lower (L) 10% of the sires with respect to weights of fat pads were compared. Cellularity measures were made of the fat pads from random samples of the two groups of progeny. Progeny of U sires had fat pads numerically heavier than those of progeny by all sires. However, progeny of L sires had fat pad weights similar to those of all sires. Heritability estimates of abdominal fat pad weight, as calculated from half-sib correlation and regression of offspring on sires, were .29 +/- .36 and .27 +/- .06, respectively. Genetic estimates indicated fat pad weight to be highly correlated with growth but essentially uncorrelated with egg production. Progeny of the L and U sires had the same number of adipocytes, but progeny by U sires had larger adipocytes than progeny by L sires.

Shortening and tenderness of pre-rigor heated beef: Part 2 - Effect of heating rate on muscles of electrically stimulated carcasses.

This study was conducted to compare the effects of rapid and slow heating rates on muscles from electrically stimulated beef carcasses. Myofibrillar and cooking shortening and related changes were measured with physiograph recordings on pre-rigor M. triceps brachii strips suspended in paraffin oil during heating. Warner-Bratzler shear values were determined on pre-rigor and post-rigor M. triceps brachii samples heated at approximately the same rates at which muscle strips were heated (2°C/2 min and 2°C/12 min), on pre-rigor M. triceps brachii samples heated at 2°C/6 min, 2°C/9 min and 2°C/12 min and on pre-rigor and post-rigor M. triceps brachii and M. longissimus muscle heated similarly at 2°C/12 min. Rapid heating (2°C/2 min) of pre-rigor muscle produced more severe myofibrillar shortening that was complete at higher muscle temperature than slow heating (2°C/12 min). Slow heating, in contrast to rapid heating, resulted in a cooked product of lower shear value in both the pre-rigor and post-rigor states. The slower the heating rate of the pre-rigor M. triceps brachii, the more tender was the product. Heating at a rate of 2°C/12 min produced acceptable tenderness in both the pre-rigor M. longissimus and M. triceps brachii muscles but even greater tenderness when both muscles were heated in the post-rigor state. The tenderizing action of severe muscle shortening could not be induced in electrically stimulated muscle.

Myofiber differentiation in skeletal muscles of newborn runt and normal weight pigs.

Differentiation of myofiber types and proportions of secondary and primary myofibers were investigated in the deep semitendinosus and longissimus muscles of 12-h- and 3-d-old littermate runt and normal birth weight pigs. Runt pigs 12 h after birth had lower proportions of type I fibers in the deep semitendinosus than did normal size pigs, which indicates that in utero stunting delayed the normal differentiation of myofiber histochemical characteristics. More of the type I myofibers had centrally located nuclei in runt pigs than in normal birth weight pigs. Also, newborn runt pigs had lower ratios of secondary to primary myofibers in the deep semitendinosus. This result indicates that the restriction of prenatal myofiber hyperplasia probably had a greater effect on secondary than on primary myofiber formation. None of these differences were observed in the longissimus muscle.

Myofibrillar protein degradation after eccentric exercise.

Male rats were run downhill for 90 minutes (nonexhaustive). Following the exercise, muscle protein degradation was increased, as determined by urinary 3-methylhistidine. However, minimal changes were observed in the relative percentage of the minor myofibrillar proteins and in the protease calcium activated factor in the long head of the triceps brachii muscle (eccentrically exercised) following the exercise bout.

Growth of fiber types and apparent fiber number in skeletal muscle of broiler- and layer-type chickens.

Proportions of myofiber types, radial growth (diameter) of myofibers and apparent myofiber number were measured at the midsection of the sartorius muscle of broiler- and layer-type chickens. Broiler birds grew mor rapidly than layer birds so that in comparisons at equal age, broilers had heavier body and muscle weights, larger diameter type I and II myofibers and greater apparent myofiber number. The proportion of type II red myofibers decreased and that of type II white myofibers increased during growth. These changes occurred at a younger age in broiler-type birds. At equal body weights, however, broiler- and layer-type birds had similar proportions of the various myofiber types, which indicates that development of myofiber types is affected by functional demands on skeletal muscle related to increasing body weight. At equal body weights, broilers had larger diameter type II myofibers than layers and had a more rapid rate of type II myofiber radial hypertrophy during growth. In contrast, layer-type birds had larger type I myofibers than did broilers and the rate of radial growth was similar between breeds. Apparent myofiber number per unit of body weight increased during growth at a similar rate in the two types of birds but broilers had greater numbers of myofibers. It was concluded that more rapid growth and greater muscularity of broiler-type birds are caused by more rapid myofiber hypertrophy and the presence of more myofibers. It is suggested that selection for growth and muscularity favors factors that promote selective radial hypertrophy of type II myofibers as seen in broiler-type chickens.

Bovine muscle shortening and protein degradation after electrical stimulation, excision and chilling.

Electrical stimulation-dependent improvement in beef tenderness resulted from mechanisms other than avoidance of cold shortening in excised muscle chilled at a normal rate (10°C at 10h post-stimulation). At normal chilling rate, electrical stimulation enhanced degradation of the myofibrillar proteins, alpha actinin and troponin-T, and increased the amount of a 30 000 dalton protein, as assessed by gel electrophoresis, whereas sarcomere lengths were not different from unstimulated muscle. Under slightly accelerated chilling conditions (10°C at 5 h post stimulation), electrical stimulation prevented cold shortening but the meat was more tender than, and had the same sarcomere length as, unstimulated muscle chilled to 10°C in 10 h. Electrical stimulation did not improve the tenderness of beef chilled at a rapid rate (10°C at 2 h post stimulation), nor did it prevent cold shortening when muscles were chilled rapidly.

Effect of electrical stimulation on thermal shrinkage temperature of bovine muscle collagen.

The effect of beef carcass electrical stimulation on the thermal stability of intramuscular collagen was determined. Differential scanning calorimetric determinations of thermal shrinkage temperature revealed that electrical stimulation lowered the shrinkage temperature of collagen by an average of .6 C in the population of cattle studied. No difference between Hereford x Angus crossbreds and Charolais crossbreds were found, but the extent of the reduction of collagen shrinkage temperature caused by electrical stimulation was greater in animals that did not receive high grain diets or received grain for only a short period than in those fed grain for up to 210 days. Furthermore, panel tenderness and Warner-Bratzler shear tests showed that stimulation-induced tenderization was also greater in animals fed no grain or fed grain for a short time. No evidence of stimulation effects on myofibrillar proteins was observed from data on sarcomere length or myofibrillar fragmentation index. The reduction of thermal stability of bovine intramuscular collagen by electrical stimulation may result from a decrease in the number or strength of the collagen cross-links.

Effects of cell size and animal age on glucose metabolism in pig adipose tissue.

Adipose tissue slices were prepared from middle subcutaneous or perirenal adipose tissue excised from pigs of different ages (and obesity) and incubated with [U-14C]glucose. After incubation, the slices were fixed with osmium tetroxide and separated into diameter ranges of 20--63, 63--102, and 102--153 microgram, respectively. Following determination of cell size and number, the fixed adipocytes were decolorized with H2O2 prior to quantification of glucose conversion to total lipid, glyceride fatty acids, glycerideglycerol, and CO2. Glucose conversion to total lipid or CO2 was unaffected by the presence of purified porcine insulin (0, 10, 100, 1000, and 100,000 microM/ml). Within animals, adipocytes of different sizes were not different with regard to insulin sensitivity. Within a weight (age) group, conversion of glucose to total lipid (insulin present) or to glyceride fatty acids and glyceride-glycerol (insulin absent) per cell was significantly greater in large adipocytes compared to small adipocytes, regardless of the group examined. With increasing weight or age, there was a markedly decreased conversion of glucose to total lipid and glyceride fatty acids among adipocytes of similar size within a cell-size fraction. The diminution in glucose metabolism was greater (as a percentage) in 20--63 microgram adipocytes than for 63--102 or 102--153 microgram adipocytes. However, for all cell-size fractions there was a marked decrease in glucose conversion to fatty acids. Glyceride-glycerol synthesis was impaired in adipocytes from older pigs, but the decrease was less than observed for glyceride fatty acid synthesis.