B-mode, real-time ultrasound for estimating carcass measures in live sheep: accuracy of ultrasound measures and their relationships with carcass yield and value.

Accuracy and repeatability of live-animal ultrasound measures, and the relationships of these measures with subprimal yields and carcass value, were investigated using data from 172 wethers. Wethers were F(1) progeny from the mating of 4 terminal sire breeds to Rambouillet ewes and were finished in a feedlot to a mean BW of 62.9 kg (SD = 9.5 kg). Before transport to slaughter, LM area, LM depth, and backfat thickness were measured from transverse ultrasound images taken between the 12th and 13th ribs. After slaughter, these measures were taken on each carcass. Carcasses were fabricated into subprimal cuts, and weights were recorded. Ultrasound accuracy and repeatability were assessed using bias, SE of prediction, SE of repeatability, and simple correlations. Relationships among ultrasound and carcass measures, and between these measures and carcass yield and value, were evaluated using residual correlations and linear prediction models. Ultrasound bias approached 0 for LM area, and backfat thickness was overestimated by only 0.69 mm. The SE of prediction and r were 1.55 cm(2) and 0.75 for LM area, and 1.4 mm and 0.81 for backfat thickness, respectively. The SE of repeatability was 1.31 cm(2) and 0.75 mm for LM area and backfat thickness, respectively. At a standardized BW and backfat thickness, wethers with larger LM area and LM depth yielded larger and more valuable carcasses, and these relationships were detectable with ultrasound. For each SD increase in carcass LM area, dressing percentage increased 1.57 percentage points, gross carcass value increased US$5.12, and boxed carcass value increased US$6.84 (P < 0.001). For each SD increase in ultrasound LM area, dressing percentage increased 0.95 percentage points, gross carcass value increased US$3.15, and boxed carcass value increased US$3.86 (P < 0.001). When LM area effects were adjusted for carcass weight, the response in boxed carcass value attributed to disproportionate increases in high-value subprimal cut weights was small. Associations of dressing percentage and carcass value with ultrasound and carcass LM depth were significant (P < 0.01) but smaller than corresponding associations with LM area. These data indicate biological and economical incentives for increasing LM area in wethers, and live-animal ultrasound can provide reliable estimates of carcass measures. These results are applicable to terminal sire breeders and producers who market sheep using carcass-merit pricing systems.

Evaluation of three-ram cohort serving capacity tests as a substitute for individual serving capacity tests.

Alternatives to time-consuming, laborious individual serving capacity tests (ISCT) are needed to classify ram sexual behavior. The objective of study 1 was to evaluate the relationship between the first 3-ram cohort test (COSCT) scores and the mean of 5 ISCT scores. The objective of study 2 was to determine whether 1 or 2 additional COSCT improved the ability to predict ISCT scores. For study 1, rams (n = 69) were assigned to either a COSCT given before or after 9 ISCT. For study 2, rams (n = 127) were given 3 COSCT before or after 6 ISCT. For repeated COSCT, rams were initially grouped at random and subsequently rerandomized so that each ram was grouped with at least 1 different ram for each test. For both studies, the number of ejaculations from COSCT was compared with the mean number of ejaculations across the second through sixth ISCT. A threshold between high- and low-performing rams was defined in each analysis as the mean ISCT scores of sexually active rams. Rams with a mean number of ejaculations in ISCT greater than the threshold were classified as having high sexual activity, whereas rams below the threshold were classified as having low sexual activity. Rams with no ejaculations in ISCT were classified as sexually inactive. Data from studies 1 and 2 were used to evaluate the relationship between the first COSCT and the mean of 5 ISCT scores. Data from multiple COSCT were fit to various models to determine whether the ability to predict ISCT scores was improved with 1 or 2 additional COSCT. The best model for ISCT and COSCT was a piecewise linear regression model. The first COSCT correctly identified all sexually inactive rams in both studies. The first COSCT, however, also classified 56% of low sexually active rams and 18% of high sexually active rams as inactive. Rams had a 71% probability of high sexual activity in ISCT if they were classified as sexually active in the first COSCT. We conclude that a single COSCT is a reliable, albeit more conservative, and efficient alternative to a series of ISCT for characterizing sexual activity of rams. Multiple COSCT can provide some protection against culling rams with high sexual activity (i.e., approximately 50% less with 2 additional COSCT) and still retain most of the efficiency compared with ISCT. It is important to use high-performance rams for breeding because they will approximately double the number of ewes bred and lambs sired compared with low-performance rams if a large number of ewes need to be serviced daily.

Surface biosolids application: effects on infiltration, erosion, and soil organic carbon in Chihuahuan Desert grasslands and shrublands.

Land application of biosolids is a beneficial-use practice whose ecological effects depend in part on hydrological effects. Biosolids were surface-applied to square 0.5-m2 plots at four rates (0, 7, 34, and 90 dry Mg ha(-1)) on each of three soil-cover combinations in Chihuahuan Desert grassland and shrubland. Infiltration and erosion were measured during two seasons for three biosolids post-application ages. Infiltration was measured during eight periods of a 30-min simulated rain. Biosolids application affected infiltration rate, cumulative infiltration, and erosion. Infiltration increased with increasing biosolids application rate. Application of biosolids at 90 dry Mg ha(-1) increased steady-state infiltration rate by 1.9 to 7.9 cm h(-1). Most of the measured differences in runoff among biosolids application rates were too large to be the result of interception losses and/or increased hydraulic gradient due to increased roughness. Soil erosion was reduced by the application of biosolids; however, the extent of reduction in erosion depended on the initial erodibility of the site. Typically, the greatest marginal reductions in erosion were achieved at the lower biosolids application rates (7 and 34 dry Mg ha(-1)); the difference in erosion between 34 and 90 dry Mg ha(-1) biosolids application rates was not significant. Surface application of biosolids has important hydrological consequences on runoff and soil erosion in desert grasslands that depend on the rate of biosolids applied, and the site and biosolids characteristics.