W. A. Phillips

Determination of Forage Chemical Composition Using Remote Sensing

Abstract Traditional forage nutrient analysis from bench-top near-infrared spectroscopy (NIRS) or common laboratory chemical procedures provides accurate, point-based information, but often does not provide it in a timely way to allow changes in forage or animal management. The objective of this study is to determine the feasibility of estimating concentrations of nitrogen, neutral detergent fiber (NDF), and acid detergent fiber (ADF) of live, standing forages using a hand-held hyperspectral spectroradiometer (radiometer), and to compare these estimates to values determined via NIRS and laboratory chemical methods. Calibration equations were developed from canopy reflectance measurements from monocultures of Bermuda grass and then applied to a test data set to predict N, NDF, and ADF. Statistical analyses showed that forage composition estimates from the radiometer were equivalent to those from the NIRS. Such a remote-sensing approach would enable real-time assessment of forage quality, would allow mapping of the nutritional landscape, could be used as a tool to better manage pastures and supplements, and would assist in making harvesting decisions.

Analysis of ruminal fluids with the ammonia electrode

The ammonia concentration of samples collected from the rumen of beef steers was determined by both the Conway and ammonia electrode procedures. Rumen fluid had to be centrifuged and diluted for the electrode procedure to function properly. When only one animal was used as a source of rumen fluid and multiple determinations were made on each sample, the mean ammonia concentration was significantly lower for the electrode procedure than the Conway procedure. The correlation between the two procedures was greater than 0.8 in 78% of the comparisons. In 44% of the comparisons with a concentration range of 3–117 mg/100 ml, the electrode procedure yielded a higher concentration value than the Conway procedure. Two methods of employing the electrode were also compared. Although the known addition method yielded significantly lower ammonia concentration than the direct method, these differences were less than 5% of the mean and probably reflect the sensitivity of the electrode to generate a low standard error.

The influence of tropical adaptation on plasma concentrations of insulin-like growth factor-I in purebred and crossbred beef cattle

In an effort to determine whether tropical adaptation influences circulating concentrations of the growth-related hormone IGF-I, 3-breed diallel matings were conducted using temperate Bos taurus (Angus), tropical Bos indicus (Brahman), and tropical Bos taurus (Romosinuano). Purebred Angus, Braham, and Romosinuano and crossbred Angus-Braham, Angus-Romosinuano, and Braham-Romosinuano heifers and steers were evaluated in 2 separate calf crops from 2003 and 2004. Blood samples were obtained from 10 heifers of each breed group (n = 90) for each year at weaning and on d 0 and 84 of postweaning trials. Samples were also taken from 10 steers of each breed group (n = 90) at weaning and on d 0 and 60 of individual finishing phase feeding trials for each year. Concentrations of IGF-I were determined by RIA. Analyses included effects of sire breed, dam breed, year of record, the age of the dam of the calf in years, and interactions. Age of calf in days was investigated as a linear and quadratic covariate. Separate analyses were conducted for steers and heifers. The direct effect of Angus was to reduce (P < 0.03) heifer concentrations of IGF-I at d 84 and in the repeated measures analysis. In the repeated measures analysis, the direct effect of Romosinuano was to increase concentrations of IGF-I (P = 0.01). Relative to the temperate Bos taurus breed, plasma concentrations of IGF-I were numerically greater in male and female tropically adapted breed groups.

Feed efficiency of tropically adapted cattle when fed in winter or spring in a temperate location1

Earlier work has shown that young tropically adapted cattle do not gain weight as rapidly as temperately adapted cattle during the winter in Oklahoma. The objective for this study was to determine whether efficiency of gains was also affected in tropically adapted cattle and whether efficiency was consistent over different seasons. Over 3 yr, 240 straightbred and crossbred steers (F1 and 3-way crosses) of Angus, Brahman, or Romosinuano breeding, born in Brooksville, FL, were transported to El Reno, OK in October and fed in 2 phases to determine performance, individual intake, and efficiency. Phase 1 (WIN) began in November after a 28-d recovery from shipping stress and phase 2 (SS) began in March, 28 d following completion of WIN each year. The diet for WIN was a grower diet (14% CP, 1.10 Mcal NEg/kg) and that for the SS was a feedlot diet (12.8% CP; 1.33 Mcal NEg/kg). After a 14-d adjustment to diet and facilities, intake trials were conducted over a period of 56 to 162 d for determination of intake and gain for efficiency. Body weights were recorded at approximately 14-d intervals, and initial BW, median BW, and ADG were determined from individual animal regressions of BW on days on feed. Individual daily DMI was then regressed by phase on median BW and ADG, and residuals of regression were recorded as residual feed intake (RFI). Similarly, daily gain was regressed by phase on median BW and DMI, and errors of regression were recorded as residual gain (RADG). Gain to feed (G:F) was also calculated. The statistical model to evaluate ADG, DMI, and efficiency included fixed effects of dam age (3 to 4, 5, 6 to 10, and >10 yr), harvest group (3 per year), age on test, and a nested term DT (ST × XB), where DT is the proportion tropical breeding of dam (0, 0.5, or 1), ST is the proportion tropical breeding of sire (1 or 0), and XB whether the calf was straightbred or crossbred. Year of record, sire (ST × XB), and pen were random effects. Preweaning ADG and BW increased (P < 0.05) with level of genetic tropical influence, but during the WIN, ADG and efficiency estimated by G:F and RADG declined (P < 0.05). Tropical influence had little effect on RFI during the WIN, or on most traits during SS. In general, during SS, crossbred steers gained faster and were more efficient by G:F and RADG (P < 0.05) than straightbred steers. Simple correlations, both Pearson and Spearman, between RFI in WIN and RFI in SS were 0.51 (P < 0.001), whereas that for RADG was 0.17 (P < 0.01).