Time-dependent changes in plasma concentrations of 3-methylindole and blood concentrations of 3-methyleneindolenine-adduct in feedlot cattle

OBJECTIVE: To describe time-dependent changes in plasma concentrations of 3-methylindole (3MI) and blood concentrations of 3-methyleneindolenine (3MEIN)-adduct in feedlot cattle. ANIMALS: 64 yearling steers. PROCEDURES: Steers were assigned to 2 groups (32 steers/group). During the first 8 weeks, blood samples were collected from group 1 before the morning ration was fed, whereas samples from group 2 were collected 2 to 3 hours after the ration was fed. Blood samples were collected from all steers approximately 4 times/wk for 3 weeks and 3 times/wk for the subsequent 5 weeks. Samples were collected at the same time for all steers for an additional 10 weeks. Plasma samples were analyzed for 3MI concentrations. Blood samples collected from cattle in group 2 during the first 8 weeks were analyzed for 3MEIN-adduct concentrations. RESULTS: Mean blood concentration of 3MEIN-adduct increased to a maximum value on day 33 (0.80 U/microg of protein) and then decreased to a minimum on day 54 0.40 U/microg of protein). Plasma 3MI concentrations initially decreased and remained low until after day 54. Group-1 cattle had lower plasma 3MI concentrations, compared with concentrations for group-2 cattle. Blood 3MEIN-adduct concentrations and plasma 3MI concentrations were not associated with deleterious effects on weight gains. CONCLUSIONS AND CLINICAL RELEVANCE: Blood 3MEIN-adduct concentrations peaked during the period of greatest risk for development of bovine respiratory disease complex. Conversely, plasma 3MI concentrations decreased during the same period. Animal-to-animal variation in metabolic capacity to convert 3MI to 3MEIN may be of more importance than differences in plasma 3MI concentration.     

Effect of ammonium sulfate fertilization on bahiagrass quality and copper metabolism in grazing beef cattle

To assess the impact of S fertilization on bahiagrass (Paspalum notatum) quality and Cu metabolism in cattle, two studies were conducted during the summer grazing season (1999 and 2000). Pasture replicates (16.2 ha; n = 2/treatment) received the same fertilizer treatment in each growing season, consisting of 1) 67 kg N/ha from ammonium sulfate (AS), 2) 67 kg N/ha from ammonium nitrate (AN), and 3) control (no fertilizer; C). Forage sampling was conducted at 28-d intervals following fertilization by the collection of whole plants (four samples/pasture) in randomly distributed 1-m2 grazing exclusion cages and analyzed for CP, in vitro organic matter digestibility, S, P, Ca, K, Mg, Na, Fe, Al, Mn, Cu, and Zn. To determine the effect of fertilizer treatment on liver trace mineral concentrations in grazing cattle, random liver tissue samples were collected (n = 12; four/treatment) at the start and end of the study period in 2000. Ammonium sulfate fertilization increased (P < 0.001) forage S concentration in both years. Plant tissue N concentrations were increased by N fertilization, regardless of source, in 2000, but not in 1999. Cows grazing AS pastures had lower (P < 0.05) liver Cu concentrations at the end of the study period in 2000 compared to AN and C. In Exp. 2, 37 Cu-deficient heifers grazing AS fertilized pastures were obtained from the same location and allocated to one of two treatments, consisting of supplements providing 123 mg/d of either inorganic (Cu sulfate; n = 12) or organic (Availa-Cu; n = 15) Cu. Treatments were delivered for 83 d. Liver Cu increased over time in all heifers regardless of treatment; however, heifers supplemented with Availa-Cu tended (P = 0.09) to have higher mean liver Cu concentrations than those receiving Cu sulfate. The results of these studies indicate that AS fertilization of bahiagrass increases forage S concentrations. When provided free-choice access to a complete salt-based trace mineral supplement, cows grazing AS-fertilized pastures had lower liver Cu concentrations than cows grazing pastures fertilized with AN; upon removal from high-S pastures, cattle were able to respond to Cu supplementation.     

Growth of four tree species managed as hedgerows in response to liming on an acid soil in West Sumatra,Indonesia

A hedgerow intercropping study was conducted for 7 years in West Sumatra, Indonesia on an acid and highly Al-saturated soil to determine growth and yield responses of tree hedgerows and upland rice and cowpea intercrops. Three tree species,Paraserianthes falcataria, Calliandra calothyrsus, andGliricidia sepium and a no-tree control were planted at three lime rates with low annual fertilizer inputs of 20 kg P and 50 kg K ha^–1.Paraserianthes andCalliandra grew vigorously, whileGliricidia grew poorly and was replaced after four years withFlemingia macrophylla. After four years,Paraserianthes yields declined due to tree mortality, probably due to intensive pruning.Calliandra andFlemingia were well adapted to intensive pruning (4 to 6 times per year). Gliricidia growth was especially limited by low soil Ca availability and high soil acid saturation.Calliandra andFlemingia yields increased with liming only in the last several years of the study whileParaserianthes did not respond to lime. The species can be tentatively ranked in response to lime as:Gliricidia > Calliandra > Flemingia > Paraserianthes.     

Using segmented regression models to fit soil nutrient and soybean grain yield changes due to liming

Frequently soil-plant relationships and responses are complex combinations of increases-level-decreases consisting of linear segments of differing slope. Segmented regression is very useful to express and quantify such relationships and responses. Fitting segmented regression models to such data, however, remains a challenge. The problem is in estimating the join points and coefficients. We use median functions to express segmented regression models, and estimate the join points by standard estimation routines such as Marquardt, Newton, and doesn’t use derivatives (DUD) methods that are available in statistical software such as SAS. Segmented straight-line models are fit to data reflecting soil Manganese (Mn), Calcium (Ca), Phosphorus (P), and soybean yield changes under different soil pH conditions due to liming. A systematic comparison of the slopes and join points suggests that different mechanisms are limiting soybean yield at different intervals as soil pH increased.