Phosphorus Requirement for Finishing Heifers

Sixty head of crossbred heifers (614 lb initial BW) were individually fed one of five levels of phosphorus of 0.10, 0.17, 0.24, 0.31, 0.38 % of diet DM with supplemental P from monosodium phosphate. Heifers were fed an energy-dense diet composed primarily of corn starch and corn fiber to minimize P from corn. When compared to the other four levels, heifers fed at the 0.10 % P level had lower DMI, ADG and final BW. Heifers fed 0.10%P had lower plasma P concentration. Breakpoint analysis of ADG suggests that the P requirement for finishing heifers is 0.115% P of diet DM within the range of 8.2 to 10.3g P/day (0.104 and 0.127% P on a DM basis)

Development of a Set of Forage Standard to Estimate \u3ci\u3eIn Vivo\u3c/i\u3e Digestibility of Forages and Prediction of Forage Quality of Diets Consumed by Cattle Grazing Nebraska Sandhills Range Pastures

In beef cattle productions systems, feed costs accounts for the majority of production costs. In year-round grazing systems, knowledge of diet quality is important for supplement formulation and predicting animal response in order to meet production goals without increasing feeding costs. The objectives of these two trials were: to develop a set of feed standards to use in in vitro laboratory procedures to estimate in vivo digestibility of forages, determine the effect of moisture, day, and grazing level on diet quality, and develop prediction equations to estimate diet quality using the variables moisture, day and grazing level. Trial 1 used 8 crossbred yearling steers to determine in vivo digestibility of 5 chopped hays (Malf, Ialf, Mbrome, Ibrome, and prairie). Feces, feed, and feed refusals were analyzed for DM, OM, CP, NDF, IVDMD and protein fractions. Feed samples were included in 21 separate IVDMD runs and regressed against the in vivo digestibilities. As hay digestibility increased DMI increased (P \u3c 0.01). Slopes of the 21 regression equations did not differ; however, there were differences between the individual IVDMD runs. In vivo and in vitro digestibilities were correlated and the average for all 21 runs was r = 0.831. In trial 2, diet samples were collected using esophageally-fistulated cows from pastures varying in grazing pressure from May 2003 through November of 2005 in the Nebraska Sandhills. Diet samples were analyzed for CP, IVOMD, NDF, and protein fraction. In Vitro OMD was adjusted to in vivo digestibility using the regression equations generated from the hay standards within each run. Diet digestibility and CP were used in a series of multiple regression equations to predicted diet quality using the variables moisture, day and grazing pressure. Diets were higher in CP and OMD during the growing season and remained constant during the dormant season. Predicted digestibility and protein were correlated to observed values

Development of a set of forage standard to estimate in vivo digestibility of forages and prediction of forage quality of diets consumed by cattle grazing Nebraska Sandhills range pastures

In beef cattle productions systems, feed costs accounts for the majority of production costs. In year-round grazing systems, knowledge of diet quality is important for supplement formulation and predicting animal response in order to meet production goals without increasing feeding costs. The objectives of these two trials were: to develop a set of feed standards to use in in vitro laboratory procedures to estimate in vivo digestibility of forages, determine the effect of moisture, day, and grazing level on diet quality, and develop prediction equations to estimate diet quality using the variables moisture, day and grazing level. Trial 1 used 8 crossbred yearling steers to determine in vivo digestibility of 5 chopped hays (Malf, Ialf, Mbrome, Ibrome, and prairie). Feces, feed, and feed refusals were analyzed for DM, OM, CP, NDF, IVDMD and protein fractions. Feed samples were included in 21 separate IVDMD runs and regressed against the in vivo digestibilities. As hay digestibility increased DMI increased (P\u3c0.01). Slopes of the 21 regression equations did not differ; however, there were differences between the individual IVDMD runs. In vivo and in vitro digestibilities were correlated and the average for all 21 runs was r = 0.831. In trial 2, diet samples were collected using esophageally-fistulated cows from pastures varying in grazing pressure from May 2003 through November of 2005 in the Nebraska Sandhills. Diet samples were analyzed for CP, IVOMD, NDF, and protein fraction. In Vitro OMD was adjusted to in vivo digestibility using the regression equations generated from the hay standards within each run. Diet digestibility and CP were used in a series of multiple regression equations to predicted diet quality using the variables moisture, day and grazing pressure. Diets were higher in CP and OMD during the growing season and remained constant during the dormant season. Predicted digestibility and protein were correlated to observed values

Comparison of \u3ci\u3eIn Vivo\u3c/i\u3e Digestibility to \u3ci\u3eIn Vitro\u3c/i\u3e Digestibility of Five Forages Fed to Steers

Eight crossbred yearling steers were used in a Latin rectangle design to determine the in vivo digestibility of five different forages. Feed intakes were higher when steers were fed forages with higher IVDMD. In vivo digestibility of the hay used in this trial was highly correlated to in vitro digestibility. On average, in vitro DMD was 5.4 percentage units higher than in vivo digestibility. Including these five hay samples as standards for in vitro analysis allows researchers to compare samples analyzed across in vitro runs. It also allows researchers to adjust the in vitro DMD to in vivo DMD, which allows for more accurate ration formulation and animal response prediction

Effects of Dietary Phosphorus Level in Beef Finishing Diets on Phosphorus Excretion Characteristics

Five ruminally fistulated steers were fed five finishing diets containing varying levels and sources of phosphorus (P). Diets consisted of 3 brewer’s grits-based diets consisting of one with no supplemental P (0.12) and two supplemented with mineral P (0.27%, and 0.42% P), one corn-based diet (0.30% P), and one diet containing dry distillers grains (0.36% P). As P intake increased, P excretion increased and was positively correlated (r = 0.67; P \u3c 0.01) to P intake. Most of the P excretion was fecal P averaging 88.7% of total excretion. With the exception of steers fed the 0.12% P diet with very little (0.50 g/day) urinary P, steers fed the other treatment diets excreted an average 2.1 g/day via the urine. These data suggest that P intake is positively correlated to P excretion and diet P concentration may impact route of excretion

Comparison of Crude Protein and Digestibility of Diets of Grazing Cattle at Different Sandhills Range Sites

Diet samples were collected May through September (2003) and May through November (2004) using esophageally fistulated cows at ranches in the Sandhills and southwest Nebraska. Differences in CP between the two locations were significant. Diets collected in May and June had higher CP (P = 0.04) than those collected in August through November. No interactions were detected between year and location in diet digestibility and diet digestibility was similar for southwest Nebraska and Sandhills diets

Determination of Diet Protein and Digestibility of Native Sandhills Upland Range

A significant year by grazing level effect was detected on CP content of diet samples collected from 2003 to 2005 at the Gudmundsen Sandhills Laboratory. During drought years (2003 and 2004) cows selected plants which were higher in CP and lower in digestibility. High levels of grazing pressure decreased diet IVOMD compared to diets from ungrazed and moderately grazed pastures. Prediction models generated from these data predict dietary CP and organic matter disappearance (OMD) of cattle grazing native Sandhills range pastures