Two apparently unrelated groups of symbiotic annelids, Nautiliniellidae and Calamyzidae (Phyllodocida, Annelida), are a clade of derived chrysopetalid polychaetes.

Nautiliniellidae Miura and Laubier, 1989 is a small family of marine polychaetes with 20 currently described species in 11 genera, most of which are known to live symbiotically in the mantle cavity of bivalves, mainly from cold seeps and hydrothermal vents, while Calamyzidae (Hartmann-Schröder, 1971) including only one described species, Calamyzas amphictenicola Arwidsson 1932 lives as an ectoparasite on ampharetid polychaetes in Swedish waters. Nautiliniellidae and Calamyzidae have both been considered to belong to Phyllodocida, but the few phylogenetic studies including these taxa have found their positions unstable. The internal relationships within Nautiliniellidae are also poorly understood. Using molecular information from both nuclear and mitochondrial genes and morphological data we assessed the systematic placement of Nautiliniellidae (seven species; collected from Pacific hydrothermal vents and cold seeps and one from Atlantic waters) and Calamyzas amphictenicola. Our results show that C. amphictenicola and Nautiliniellidae formed a well-supported clade that is nested within Chrysopetalidae, a free-living group of polychaetes. The chrysopetalid genus Vigtorniella Kiseleva 1992; a bacterial mat grazer found at methane seeps, anoxic basins and whalefalls, formed a paraphyletic grade with respect to the Nautiliniellidae-Calamyzas clade. The internal relationships within the Nautiliniellidae-Calamyzas clade as well as the relationships with their hosts are also examined. As a result we synonymize Calamyzidae and Nautiliniellidae with Chrysopetalidae, with the last as the oldest available family-group name. Within Chrysopetalidae we refer to the subfamilies Chrysopetalinae Ehlers 1864; Dysponetinae Aguado, Nygren & Rouse, herein; and Calamyzinae Hartmann-Schröder, 1971. Calamyzinae contains C. amphictenicola, all taxa formerly in Nautiliniellidae, and the chrysopetalid genus Vigtorniella.

The genome of the natural genetic engineer Agrobacterium tumefaciens C58.

The 5.67-megabase genome of the plant pathogen Agrobacterium tumefaciens C58 consists of a circular chromosome, a linear chromosome, and two plasmids. Extensive orthology and nucleotide colinearity between the genomes of A. tumefaciens and the plant symbiont Sinorhizobium meliloti suggest a recent evolutionary divergence. Their similarities include metabolic, transport, and regulatory systems that promote survival in the highly competitive rhizosphere; differences are apparent in their genome structure and virulence gene complement. Availability of the A. tumefaciens sequence will facilitate investigations into the molecular basis of pathogenesis and the evolutionary divergence of pathogenic and symbiotic lifestyles.

Bone-eating Osedax females and their 'harems' of dwarf males are recruited from a common larval pool.

Extreme male dwarfism occurs in Osedax (Annelida: Siboglinidae), marine worms with sessile females that bore into submerged bones. Osedax are hypothesized to use environmental sex determination, in which undifferentiated larvae that settle on bones develop as females, and subsequent larvae that settle on females transform into dwarf males. This study addresses several hypotheses regarding possible recruitment sources for the males: (i) common larval pool--males and females are sampled from a common pool of larvae; (ii) neighbourhood--males are supplied by a limited number of neighbouring females; and (iii) arrhenotoky--males are primarily the sons of host females. Osedax rubiplumus were sampled from submerged whalebones located at 1820-m and 2893-m depths in Monterey Bay, California. Immature females typically did not host males, but mature females maintained male 'harems' that grew exponentially in the number of males as female size increased. Allozyme analysis of the females revealed binomial proportions of nuclear genotypes, an indication of random sexual mating. Analysis of mitochondrial DNA sequences from the male harems and their host females allowed us to reject the arrhenotoky and neighbourhood hypotheses for male recruitment. No significant partitioning of mitochondrial diversity existed between the male and female sexes, or between subsamples of worms collected at different depths or during different years (2002-2007). Mitochondrial sequence diversity was very high in these worms, suggesting that as many as 10(6) females contributed to a common larval pool from which the two sexes were randomly drawn.

Acquisition of dwarf male "harems" by recently settled females of Osedax roseus n. sp. (Siboglinidae; Annelida).

After the deployment of several whale carcasses in Monterey Bay, California, a time-series analysis revealed the presence of a new species of Osedax, a genus of bone-eating siboglinid annelids. That species is described here as Osedax roseus n. sp. It is the fifth species described since the erection of this genus and, like its congeners, uses a ramifying network of "roots" to house symbiotic bacteria. In less than 2 months, Osedax roseus n. sp. colonized the exposed bones of a whale carcass deposited at 1018-m depth, and many of the females were fecund in about 3 months post-deployment. As with other Osedax spp., the females have dwarf males in their tube lumens. The males accrue over time until the sex ratio is markedly male-biased. This pattern of initial female settlement followed by gradual male accumulation is consistent with the hypothesis that male sex may be environmentally determined in Osedax. Of the previously described species in this genus, Osedax roseus n. sp. is most similar to O. rubiplumus, but it has several anatomical differences, as well as much smaller females, dwarf males, and eggs. Osedax roseus n. sp. is markedly divergent (minimally 16.6%) for mitochondrial cytochrome oxidase subunit I (mtCOI) sequences from any other Osedax species.

Phylogenetic placement of Cibicidoides wuellerstorfi (Schwager, 1866) from methane seeps and non-seep habitats on the Pacific margin.

Benthic foraminifera are among the most abundant groups found in deep-sea habitats, including methane seep environments. Unlike many groups, no endemic foraminiferal species have been reported from methane seeps, and to our knowledge, genetic data are currently sparse for Pacific deep-sea foraminifera. In an effort to understand the relationships between seep and non-seep populations of the deep-sea foraminifera Cibicidoides wuellerstorfi, a common paleo-indicator species, specimens from methane seeps in the Pacific were analyzed and compared to one another for genetic similarities of small subunit rDNA (SSU rDNA) sequences. Pacific Ocean C. wuellerstorfi were also compared to those collected from other localities around the world (based on 18S gene available on Genbank, e.g., Schweizer et al., 2009). Results from this study revealed that C. wuellerstorfi living in seeps near Costa Rica and Hydrate Ridge are genetically similar to one another at the species level. Individuals collected from the same location that display opposite coiling directions (dextral and sinstral) had no species level genetic differences. Comparisons of specimens with genetic information available from Genbank (SSU rDNA) showed that Pacific individuals, collected for this study, are genetically similar to those previously analyzed from the North Atlantic and Antarctic. These observations provide strong evidence for the true cosmopolitan nature of C. wuellerstorfi and highlight the importance of understanding how these microscopic organisms are able to maintain sufficient genetic exchange to remain within the same species between seep and non-seep habitats and over global distances.

Least-inclusive taxonomic unit: a new taxonomic concept for biology.

Phylogenetic taxonomy has been introduced as a replacement for the Linnaean system. It differs from traditional nomenclature in defining taxon names with reference to phylogenetic trees and in not employing ranks for supraspecific taxa. However, 'species' are currently kept distinct. Within a system of phylogenetic taxonomy we believe that taxon names should refer to monophyletic groups only and that species should not be recognized as taxa. To distinguish the smallest identified taxa, we here introduce the least-inclusive taxonomic unit (LITU), which are differentiated from more inclusive taxa by initial lower-case letters. LITUs imply nothing absolute about inclusiveness, only that subdivisions are not presently recognized.

Paired development of hair cells in neuromasts of the teleost lateral line.

Lateral line neuromasts of the bullseye Parapriacanthus ransonetti and the cardinal fish Apogon cyanosoma were examined by scanning electron microscopy. Neuromasts showed large numbers of degenerating hair cells and immature hair cells, suggesting a high degree of hair cell turnover. New hair cells were mainly produced in pairs (fewer than 5% appear singly), the two cells of a pair having opposite but parallel orientations of their mechanosensitive axes. It is suggested that each pair results, directly or indirectly, from a single mitosis. The results further suggest that the axis of mitosis is one of the factors which determine the direction of the hair cell axis of mechanosensitivity.

Management of antenatally diagnosed fetal ovarian cysts.

1. Fetal ovarian cysts are usually unilateral, diagnosed in the third trimester and are uncommon. 2. Average ovarian cyst size is 5 x 5 cm at diagnosis and size does not change throughout the pregnancy. 3. Most cysts are functional in origin and histologically benign, simple cysts. 4. Polyhydramnios is a common finding but associated anomalies are rare. 5. Although large cysts can compress other viscera and torsion or rupture can occur, in utero aspiration has limited value in prenatal management. 6. Vaginal delivery with confirmed fetal pulmonary maturity or at term is appropriate. 7. Soft tissue dystocia is rare. Cesarean delivery should be reserved for obstetrical indications only. 8. The best predictor of neonatal cyst torsion risk is length of the cyst pedicle rather than cyst size. 9. When surgery is indicated a cystectomy, with preservation of maximal ovarian tissue is to be preferred over oophorectomy. 10. Ultrasound-guided aspiration of neonatal ovarian cysts may be an alternative to surgical management.

Effects of streptomycin on development of the apical structures of hair cells in the chick basilar papilla.

A single dose of streptomycin (166 mg/kg egg weight) was given to chick embryos 7-15 days after the beginning of incubation. Embryos were fixed 4-12 days later, and the hair cells examined by scanning and transmission electron microscopy. The highest proportion of abnormalities was produced by injections on or before the 11th day of incubation, later injections affecting a substantially smaller proportion of embryos. This suggests the possibility of a critical period for streptomycin ototoxicity in the chick. In addition to the normal signs of cellular degeneration, the most striking abnormality was a massive expansion in the apical surface, sometimes by a factor of 20, in area. The organisation of stereocilia was also commonly affected. The stereocilia could be broken up into multiple small separate bundles, and often there was a wide separation between the kinocilium and the stereocilia. Stereocilia tended to be reduced in number, fused, and either of abnormally large, small, or irregular diameters. Structures with the appearance of stereociliar cores often lay horizontally within the surface of the cuticular plate, sometimes running for 15 microns or more. Sometimes abnormal 'stereocilia' were expressed around the extreme margins of the cuticular plate. In addition, adjacent hair cells could show very different developmental stages, as though the development of some cells had been arrested. With all these changes, the short hair cells in the centre of a papillar cross-section tended to be the most affected, with the tall hair cells and the short hair cells on the extreme inferior (i.e. abneural) edge being least affected. It is suggested that the streptomycin alters the balance of the different aspects of development of the hair cells. It might therefore be possible to use ototoxicity as a way of analysing hair-cell development.

The development of links between stereocilia in hair cells of the chick basilar papilla.

Auditory papillae of chicks (embryonic age 6-21 days) were examined by scanning and transmission electron microscopy, in order to trace the development of the tip links between the stereocilia, and in order to trace the development of the spatial organisation of the tip links. In the most immature bundles, stereocilia were not graded in height, while strands of tenuous material interconnected adjacent stereocilia, this material being concentrated in a band near the tips of the stereocilia. The material joined the stereocilia in all directions, with no preferential direction for the interconnecting material being visible. Similarly, no columnar organisation of the stereocilia was visible. As soon as a gradation in height of the stereocilia began to appear, material could be seen running upwards from the shorter stereocilia to the adjacent lengthening stereocilia. There was a continuum in appearance between (i) the material running laterally between short immature stereocilia, (ii) the material running upwards between stereocilia which were developing a gradation in height, and (iii) the tip links seen in more mature bundles. It is suggested that tip links are a specialisation of the links which join immature stereocilia laterally near their tips. It is also suggested that the orientation of tip links, parallel to the hair cell axis of bilateral symmetry, is produced by the gradient in growth of the stereocilia.

The incorporation and turnover of radiolabelled amino acids in developing stereocilia of the chick cochlea.

Hair cell stereocilia are composed of packed actin filaments, oriented such that the preferred end for the addition of actin monomers is at the tips of the sterocilia. It has therefore been suggested that when stereocilia grow, they do so from their tips (Tilney and DeRosier, 1986, Dev. Biol. 116, 119-129). In order to test the hypothesis, radiolabelled amino acids were applied to the air-sac of chicken eggs at day 17 of incubation, i.e., at the beginning of a phase in which the stereocilia have achieved their mature width, but are growing rapidly in length. Incorporation of radiolabel was studied autoradiographically, followed by image analysis and averaging grain counts over many hair cells. In contrast to the position expected from the above hypothesis, there was no sign of preferential incorporation of label in the upper part of the stereociliary bundle. The greatest density of labelling was found in the lower part of the bundle, while the upper part of the bundle was under-represented in the autoradiographic averages. The turnover time (to fail to 1/e) was significantly greater in the bundle (16 days) than in the cuticular plate or in the rest of the cell (9 days). The results (i) give no support for the hypothesis that stereocilia grow from the tips, and (ii) suggest that during development at least some components of the stereocilia turn over with a relatively short time course.

Estimation of genetic parameters for ultrasound-predicted percentage of intramuscular fat in Angus cattle using random regression models.

The present study included 3,358 observations of 675 bulls and heifers from the Iowa State University beef cattle breeding project. Data were collected over a 3-yr period between 1998 and 2000. Each year, cattle were scanned four to six times for ultrasound-predicted percentage of intramuscular fat (UPFAT) and other ultrasound traits, starting at a minimum age of 28 wk. The objective of the current study was to estimate variance components, heritability, and repeatability of UPFAT in young bulls and heifers. Data were subjected to random-regression animal models that included fixed effects of contemporary group, fixed Legendre polynomial of age at measurement, and random regression coefficients on Legendre polynomial of age at measurement for animals' direct genetic and direct permanent environmental effects. Phenotypic and genetic models involving different levels of polynomial fit for the animal component were considered. A model fitting a linear effect of Legendre polynomial of age at a measurement for animal direct genetic and direct permanent environmental effects and a homogeneous error variance described the present data adequately. Heritability of UPFAT ranged from 0.32 at 28 wk of age to a maximum of 0.53 at 63 wk. Repeatability of UPFAT increased from a minimum of 0.60 at ages of 28 to 39 wk to a maximum of 0.80 at ages 61 to 63 wk. Heritability and repeatability of yearling UPFAT were 0.50 and 0.71, respectively. With the exception of minor differences at earlier ages, fitting heterogeneous error variances did not have an effect on genetic parameter estimates for most ages of measurement. The present results showed an optimal heritability and repeatability of UPFAT measures around 52 wk and through at least 63 wk of age. This suggested that differences in UPFAT measures during this period also are good measures of differences in marbling genetic potential of Angus cattle.

Evaluation of carcass, live, and real-time ultrasound measures in feedlot cattle: I. Assessment of sex and breed effects.

Carcass and live-animal measures from 1,029 cattle were collected at the Iowa State University Rhodes and McNay research farms over a 6-yr period. Data were from bull, heifer, and steer progeny of composite, Angus, and Simmental sires mated to three composite lines of dams. The objectives of this study were to estimate genetic parameters for carcass traits, to evaluate effects of sex and breed of sire on growth models (curves), and to suggest a strategy to adjust serially measured data to a constant age end point. Estimation of genetic parameters using a three-trait mixed model showed differences between bulls and steers in estimates of h2 and genetic correlations. Heritability for carcass weight, percentage of retail product, retail product weight, fat thickness, and longissimus muscle area from bull data were .43, .04, .46, .05, and .21, respectively. The corresponding values for steer data were in order of .32, .24, .40, .42, and .07, respectively. Analysis of serially measured fat thickness, longissimus muscle area, body weight, hip height, and ultrasound percentage of intramuscular fat using a repeated measures model showed a limitation in the use of growth models based on pooled data. In further evaluation of regression parameters using a linear mixed model analysis, sex and breed of sire showed an important (P < .05) effect on intercept and slope values. Regression of serially measured traits on age within animal showed a relatively larger R2 (62 to 98%) and a smaller root mean square error (RMSE, .09 to 8.85) as compared with R2 (0 to 58%) and RMSE (.31 to 67.9) values when the same model was used on pooled data. We concluded that regression parameters from a within-animal regression of a serially measured trait on age, averaged by sex and breed, are the best choice in describing growth and adjusting data to a constant age end point.

Evaluation of carcass, live, and real-time ultrasound measures in feedlot cattle: II. Effects of different age end points on the accuracy of predicting the percentage of retail product, retail product weight, and hot carcass weight.

Data from 970 feedlot steers and bulls were used to evaluate effects of different age end points on the accuracy of prediction models for percentage of retail product, retail product weight, and hot carcass weight. Cattle were ultrasonically scanned three to five times for fat thickness, longissimus muscle area, and percentage of intramuscular fat. Live animal measures of body weight and hip height were also taken during some of the scan sessions. Before development of prediction equations, live and ultrasound data were adjusted to four age end points using individual animal regressions. Age end points represented mean age at slaughter (448 d), mean age at the second-to-last scan before slaughter (414 d), mean age at the third-to-last scan before slaughter (382 d), and an age end point of 365 d. Ultrasound and live animal measures accounted for a large proportion of the variation in the dependent variables regardless of the age end point considered. For all three traits, final models based on independent variables adjusted to earlier ages of 365 and 382 d showed better or at least similar model R2 and root mean square errors than those based on independent variables adjusted to a mean slaughter age of 448 d. Validation of the models using independent data from 282 steers resulted in a mean across-age rank correlation coefficient of .78, .88, and .83 between actual and predicted values of the percentage of retail product, hot carcass weight, and retail product weight, respectively. Mean across-age rank correlation of breeding values for the corresponding traits were .92, .89, and .82. The results of this study suggest that live and ultrasound traits measured as early as 365 d could be used to predict end product traits as accurately as similar measures made before slaughter at age 448 d.

Repeatability of ultrasound-predicted percentage of intramuscular fat in feedlot cattle.

We used data from 144 bulls, heifers, and steers to determine the repeatability of ultrasound-predicted percentage of intramuscular fat and to study the effect of repeated measurements on the standard error of prediction. Animals were scanned at an average age of 433 d by a certified technician. Individual bulls, heifers, and steers were scanned five to six times each with two Aloka 500-V machines, and the percentage of intramuscular fat was predicted from two regions of interest within an image. Variance components and repeatability values were computed for the overall data and by machine, region of interest, and sex. Animals were broadly divided into two groups based on mean ultrasound-predicted percentage of intramuscular fat. Variance components and repeatability values were then estimated within each group. The overall repeatability of ultrasound-predicted percentage of intramuscular fat was .63 +/- .03. Differences in the repeatability values between machines and between regions of interest were not different from zero (P > .05). Bulls showed a lower within-animal SD of .82% as compared to .97 and 1.02% for steers and heifers, respectively. However, steer ultrasound-predicted percentage of intramuscular fat measures were more repeatable (P < .05) than those of bulls and heifers. The difference in repeatability between bull and heifer measures was not important (P > .05). Animals with mean ultrasound-predicted percentage of intramuscular fat less than 4.79% showed less repeatable measures (P < .05) than those with means above 4.79%. The image variance contributed to nearly 70% of the total variance of observations within an animal. Standard error of animal mean measures showed a 50% reduction when the number of images per animal increased to four. Therefore, we concluded that increasing the number of images per animal plays a more significant role in reducing the standard error of prediction than taking multiple measurements within a single image.

Effects of electrical stimulation and postmortem storage on changes in titin, nebulin, desmin, troponin-T, and muscle ultrastructure in Bos indicus crossbred cattle.

The effects of electrical stimulation (ES) on degradation of titin, nebulin, desmin, and troponin-T (TN-T) and on structural changes in the longissimus muscle (LM) from Brahman x Simmental (B x S) cattle (Bos indicus cross) were determined. The left side of seven B x S beef carcasses was stimulated (200 V, 20 Hz) within 1 h of death, and the right side was the nonstimulated (NS) control. Myofibrils for SDS-PAGE and samples for transmission electron microscopy were prepared from the LM at 0, 1, 3, 7, 14, and 28 d postmortem (PM). The SDS-PAGE results showed that the T1 band of titin was absent by 7 d in two animals, by 14 d in four animals, and by 28 d in one animal in both NS and ES samples. By SDS-PAGE, intact nebulin was gone by 7 d in two animals and by 14 d in five animals, but in blots, nebulin decreased by 7 d and was absent by 14 d in both NS and ES samples. The desmin band could still be seen as a light band at 28 d in Western blots of both NS and ES samples. A decrease in TN-T and a concomitant increase in the 30-kDa polypeptide were observed in both NS and ES samples. Western blots with a monoclonal antibody to TN-T confirmed that TN-T decreased at similar rates in NS and ES samples but showed that the 30-kDa polypeptide was more heavily labeled in ES samples from 7 to 28 d. Contraction nodes were present in O-d ES samples and were still observed in 28-d ES samples. Narrow, intermediate, and wide I-band fractures were seen earlier and at a greater frequency in ES than in NS samples. Overall, ES had no detectable effect on titin, nebulin, desmin, or TN-T degradation but accelerated the appearance and enhanced the frequency of three types of I-band fractures in the LM from Bos indicus crossbred cattle.

Partitioning variances of growth in ultrasound longissimus muscle area measures in Angus bulls and heifers.

The objective of the study was to estimate variance components, heritability, and repeatability of ultrasound longissimus muscle area (ULMA) measures. Data included 4,653 serial ULMA measures from 882 purebred Angus bulls and heifers. Animals were born over a 4-yr period from 1998 to 2001. Each year, bulls and heifers were ultrasonically scanned four to eight times, with a 4- to 6-wk interval between scans. Initially, data were subdivided by scan session across years and were analyzed in a multitrait model (MTM). Data pooled across years and scan session were then analyzed using random regression models (RRM) to estimate trends in genetic parameter estimates. Additive direct genetic variance increased with advancing scan session ranging from 8.67 cm4 at the first scan (mean age = 35 wk) to a maximum of 19.48 cm4 at the sixth scan (mean age = 56 wk). Heritability of ULMA increased from 0.35 at first scan to a maximum of 0.48 at the fourth scan (mean age = 50 wk). Additive direct genetic variance and heritability values at about 1 yr of age (fifth scan) were 18.24 cm4 and 0.45, respectively. Estimates from RRM also showed an increase in sigma(a)2 and h2 with age. Trends in sigma(pe)2 estimates, although tending to fluctuate, also increased with age. Additive direct genetic variance at 1 yr of age ranged from 15.8 cm4 to 17.0 cm4 for the different models. Heritability of yearling ULMA measures ranged from 0.40 to 0.42 and repeatabilities ranged from 0.80 to 0.84. For the range of ages used in the current study, both MTM and RRM showed close to maximum heritability values at around 1 yr of age. Therefore, phenotypic differences in yearling ULMA between Angus cattle are better indicators of genetic differences than earlier measurements. Angus breeders could, therefore, use ULMA measures made at around 1 yr of age to select next generation parents.

Predicting percentage of retail yield from carcass measurements, the yield grading equation, and closely trimmed, boxed beef weights.

Over the past 3 yr, 100 carcasses (64 steers, 24 bulls, and 12 heifers) were fabricated into closely trimmed (6 mm maximum fat cover), boxed beef and further evaluated for percentage of retail yield at the Iowa State University Meat Laboratory. Hot carcass weight ranged from 235 to 399 kg with a least squares mean (LSM) and standard error across all sex classes of 318 +/- 3 kg. Additionally, fat cover ranged from .30 to 1.78 cm with an average of .91 +/- .05 cm. The LSM for longissimus muscle area (LMA) across all sex classes was 81.6 +/- 1.0 cm2. Bulls had significantly less subcutaneous fat (P less than .01) and greater LMA (P less than .01) than did either steers or heifers. Retail yield from the boxed chuck, expressed as a percentage of cold carcass weight, was 19.2 for bulls and 14.8 for steers. This difference was due primarily to a reduction of intermuscular fat. Similarly, bulls had a greater yield (P less than .01) of the boxed round than did steers. When cattle of differing frame sizes were compared, only percentage of retail yield of the boxed round was significant (P less than .01): large-framed cattle yielded 14.3 +/- .2%, compared with 12.8 +/- .2% for the small-framed cattle. When all possible regression analyses were run, sex class differences accounted for 25.7% of the variation in retail yield. The current USDA retail yield equation accounted for only 37.2% of the variation. Percentage of closely trimmed, boneless round had an R2-value of .57.(ABSTRACT TRUNCATED AT 250 WORDS)

Optimal beef cattle diets formulated by nonlinear programming.

A beef diet model based on National Research Council recommendations is significantly nonlinear for feed ingredients, daily gain and weight of cattle. Solving a diet model has been difficult, but advances in nonlinear programming now allow solutions that are quick and easy. This study developed a nonlinear programming method for optimally planning a feeding program by choosing feeds, daily gains and selling weight. Two types of diets are important for this purpose:optimal-return diets and least-cost-gain diets. For a given weight of cattle, an optimal-return diet chooses feeds and daily gain to maximize returns above feed costs. A least-cost-gain diet chooses feeds and daily gain to minimize feed plus yardage costs per kilogram of gain. In an optimal feeding program, a sequence of optimal-return diets is fed to increasing weights of cattle. Feed costs plus yardage per kilogram of gain rise to equal the actual selling price at the optimal selling weight, and the cattle are sold. Cattle feeders and researchers with access to a microcomputer can maximize net returns from a feeding program.

Predicting percentage of intramuscular fat using two types of real-time ultrasound equipment.

In the present study, 500 steers were used to develop models for predicting the percentage of intramuscular fat (PIMF) in live beef cattle. Before slaughter, steers were scanned across the 11th and 13th ribs using Aloka 500V (AL-500) and Classic Scanner 200 (CS-200) machines. Four to five images were collected per individual steer using each machine. After slaughter, a cross-sectional slice of the longissimus muscle from the 12th rib facing was used for chemical extraction to determine actual carcass percentage of intramuscular fat (CPIMF). Texture analysis software was used by two interpreters to select a region for determination of image parameters, which included Fourier, gradient, histogram, and co-occurrence parameters. Four prediction models were developed separately for each of AL-500 and CS-200 based on images captured by the respective machines. These included models developed without transformation of CPIMF (Model I), models based on logarithmic transformation of CPIMF (Model II), ridge regression procedure (Model III), and principal component regression procedure (Model IV). Model R2 and root mean square error of AL-500 Models I, II, III, and IV were 0.72, 0.84%; 0.72, 0.85%; 0.69, 0.91%; and 0.71, 0.86%; respectively. The corresponding R2 and root mean square error values of CS-200 Models I, II, III, and IV were 0.68, 0.87%; 0.70, 0.85%; 0.64, 0.94%; and 0.65, 0.91%; respectively. Initially, AL-500 and CS-200 prediction models were validated separately on an independent data set from 71 feedlot steers. The overall mean bias, standard error of prediction, and rank correlation coefficient across the four AL-500 models were 0.42%, 0.84%, and 0.88, respectively. For the four CS-200 models, the corresponding overall mean values were 0.67%, 0.81%, and 0.91, respectively. In a second validation test, only Model II of AL-500 and CS-200 was evaluated separately based on data from 24 feedlot steers. The overall mean bias, absolute difference, and standard error of prediction of AL-500 Model II were 0.71, 0.92, and 0.98%. For CS-200 Model II, the corresponding values were 0.59, 0.97, and 1.03%. Both AL-500 and CS-200 equipment can be used to accurately predict PIMF in live cattle. Further improvement in the accuracy of prediction equations could be achieved through increasing the development data set and the variation in PIMF of cattle used.