The flow structure in the separation zone of a DAF pilot plant and the relation with bubble concentration.

Fluid dynamics is believed to be of crucial importance for the removal mechanism in Dissolved Air Flotation. The paper is a presentation of experimental studies on velocity and air-content profiles in a DAF pilot plant. The correlation between air content and flow patterns is discussed. Two flow structures are detected. A stratified flow structure is defined by a horizontal transport of the water in a upper, less-dense layer, and a lower, downwards-vertical transport in the lower, dense layer. Between the layers a return flow is found. The short-circuiting flow is defined as an immediate downward deviation towards the outlet arrangement at the bottom of the tank, probably causing decreasing effluent quality. Density gradients, caused by differences in air content in the tank, are believed to generate a stratification of the water body, thus causing the water to be transported in layers. Measurements of air-content profiles correlate to the measured flow structures, also indicating a separation of the water body in two layers with a distinct boundary.

An integrated approach to dissolved air flotation.

DAFRapide techniques utilising reduced flocculation times, of the order of 5 minutes, together with flotation loading rates of up to 40 m/h, can be incorporated with conventional filtration systems operating at up to 20 m/h. Product quality of typically < 1 NTU and < 0.1 NTU after flotation and filtration respectively can be achieved.

The effects of corn milling coproducts on growth performance and diet digestibility by beef cattle.

Simmental x Angus weanling heifers (n = 96; 239 +/- 2.3 kg) were used in four replications to evaluate three dietary treatments in Trial 1. Treatments were cracked corn-hay diets supplemented with one of three corn milling industry coproducts: dry corn gluten feed (DCGF), dried distillers grains (DDG), and a new modified corn fiber (MCF). In Trial 2, ruminally cannulated mature crossbred beef steers (n = 4; 606 +/-60 kg) were used in a 4 x 4 Latin square with 11-d periods to determine digestibility and ruminal metabolism of limit-fed cracked corn-alfalfa haylage diets supplemented with cornstarch (CON), DCGF, DDG, or MCF. During Periods 3 and 4, an in situ study was conducted to compare the rate and extent of CP degradation of DCGF, DDG, and MCF. In Trial 1, there were no differences (P > .10) in initial weights or DM intake. Average daily gain and feed efficiency (G/F) were improved (P < .01) for heifers fed DCGF or DDG vs heifers fed MCF. In Trial 2, no differences (P > . 10) in digestibilities of any nutrients or in ruminal VFA concentrations were observed for steers fed coproducts. The CON supplementation decreased (P < .05) total dietary fiber (TDF) digestibility, improved (P < .10) digestibilities of DM and OM, increased (P < .05) total VFA concentrations and concentrations of propionate and valerate, and decreased (P < .05) concentrations of butyrate, isobutyrate, and isovalerate when compared with the coproducts. Dry corn gluten feed increased (P < .05) and DDG tended (P < .10) to increase percentages of the immediately soluble fraction of CP, and both had increased (P < .05) rates (Kd) and greater (P < .05) extent of ruminal CP degradation than MCF. These data suggest that DCGF and DDG may be utilized in limit-fed high-energy diets without sacrificing performance. Feeding of MCF resulted in poorer performance of heifers, suggesting a limited feeding value that results from high ADIN content and slow in situ protein digestion.

Shade and wind barrier effects on summertime feedlot cattle performance.

In each of three summertime trials conducted over consecutive years, approximately 110 predominantly black and black-white-face steers were blocked by weight and randomly allotted to one of 16 pens in a 2x2 factorial arrangement of treatments. Factors consisted of cattle being fed in facilities with or without wind barriers and with or without shade. Steers were fed dry-rolled corn-based diets (1.43 Mcal/ kg, NEg). Mean starting date and days on feed were June 26 and 79, respectively. In unshaded areas, temperature and humidity averaged 21.6 degrees C and 77.9%, and the blackglobe-humidity index (BGHI) at 1500 averaged between 84.0 and 89.1. Each of four 6.1-x6.1-m structures (mean height = 3.4 m) with white steel roofs provided shade (2.65 m2/steer) for two pens. In facilities with wind barriers provided, airflow was reduced from the north and northwest by a 25-m-wide shelterbelt containing six rows of trees. For cattle fed in pens with wind barriers, shade increased (P<.05) gain from 0 to 56 d and decreased (P<.05) DMI/ADG from 0 to 28 d. Differences (P<.05) in performance were not found between shaded and unshaded cattle in any portion of the feeding period for cattle fed in the pens without wind barriers and over the entire feeding period in either type of facility. The shade response in pens with wind barriers seemed to be greater the 1st yr than in subsequent years. Differences in weather patterns among years, especially air temperature, humidity, and solar radiation, may partially explain this interaction. Also, in yr 1, cattle tended to have greater fat thickness at finish than in yr 2 and 3. Correlations between BGHI and DMI tended to be greater during the early portion of the trial (0 to 28 d) than over the entire trial. Correlations between the difference in BGHI under shade vs no shade and percentage of shade use had the greatest magnitude and were significant only in the first 28 d vs over the entire feeding period. Although no heat-related cattle deaths occurred in this study, results suggest that shade improves cattle performance in the summer when they are fed in facilities with winter wind protection available and have not become acclimated to hot conditions. Once cattle are acclimated or hot conditions subside, compensation by unshaded cattle offsets much of the initial benefits of providing shade.

Wind protection effects and airflow patterns in outside feedlots.

Steers were finished in three different sets of outside lots: 1) pens with overhead shelter on the north side; 2) pens south and southeast of a shelterbelt; and 3) pens with no shelter or windbreak. In trials conducted over a 3-yr period with predominantly British and British x Continental crossbred yearlings, performance improvements due to providing shelter or wind protection in the winter were not detected; however, in the summer, providing wind protection or shelter resulted in decreased (P < .10) cattle gains. Cattle fed in the unprotected area had greater (P < .05) fat thickness in the winter and greater marbling scores in the winter (P < .05) and autumn (P < .10) than cattle fed in protected areas. When averaged across facilities, season effects were detected for DMI (autumn > summer > winter > spring; P < .05). Feed:gain ratios followed a similar trend among seasons (summer and autumn > winter > spring P < .05). As a percentage of BW, winter (2.21), spring (2.19), and summer (2.18) DMI were less (P < .05) than autumn (2.35) DMI. Wind velocity data indicated that greater air flows tends to be found on mounds and less at the feedbunk in pens protected by shelterbelts. In unprotected, unsheltered pens, the greater airflow tends to be at the highest point in the pen (bunks and mounds). In Nebraska, benefits realized from feeding cattle in sheltered or protected areas under average or slightly milder than average winter weather conditions may be offset by lower performance experienced by cattle fed in those same areas in the summer. In addition, fat deposition seems to be enhanced in cattle exposed to moderate cold stress.

Interaction of diet composition and a reduced nocturnal temperature regimen in weanling pigs.

A three-trial experiment using 3- to 4-wk-old newly weaned pigs was conducted to evaluate the possible interaction between a 16-h reduced nocturnal temperature regimen (RNT16) and a lowered nursery diet lysine regimen on weaned pig and subsequent growing-finishing performance. Nursery temperature treatments were 1) a control temperature (CT) regimen of 30 degrees C constant air temperature lowered 2 C degree/wk and 2) a regimen beginning 1 wk after weaning in which the temperature from 1600 to 0800 was lowered 6 C degree from CT. Within each temperature treatment, all pigs were offered a diet containing 1.20% lysine for the 1st wk after weaning followed by 1.20 or 1.10% lysine to 10.5 kg and 1.00 or .90% lysine to 20 kg. There was no interaction of temperature regimen and diet on overall nursery performance. The RNT16 pigs had improved (P = .1) ADG (.351 vs .342 kg/d) with no difference (P > .1) in ADFI (.693 vs .680 kg/d) or G:F (.508 vs .506) compared with CT. Pigs fed the lower lysine sequence had poorer (P < .0001) ADG (.333 vs .360 kg/d) and G:F (.487 vs .527) than controls. There was also no effect (P > .1) of RNT16 vs CT on subsequent performance to slaughter weight for ADG (.770 vs .755 kg/d) or G:F (.309 vs .311). There was also no effect (P > .1) of a lowered nursery lysine sequence compared to control on growing-finishing ADG (.768 vs .757 kg/d) or G:F (.312 vs .309).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of sequential implanting with Synovex on steer and heifer performance.

Studies were conducted using 72 (Exp. 1) and 248 (Exp. 2) steer and heifer calves from 1 to 2 mo of age through slaughter to determine whether preweaning implants affect postweaning feed conversion of cattle that are rapidly grown and(or) finished in the feedlot. In Exp. 1, treatments were three Synovex (S) implants administered 0, 70, and 140 d postweaning (NSSS) or Synovex-C (C) administered preweaning and three implants administered postweaning (CSSS). In Exp. 2, treatments were no implants (NNNN), implants administered 0, 74, and 148 d postweaning to calves that had either received no preweaning implant (NSSS), or C (CSSS), and CSSS plus trenbolone acetate (TBA) administered with the last S implant (CSSS-TBA). Synovex-S or -H implants were administered postweaning to steers and heifers, respectively. Steer and heifer calves implanted with C in the preweaning phase were 9.0 and 13.0 kg (Exp. 1) and 7.5 and 15.0 kg (Exp. 2) heavier (P < .10), respectively, at weaning than nonimplanted steer and heifer calves. In Exp. 1, preweaning implant had no affect on postweaning performance or quality grade. In Exp. 2, preweaning implants (NSSS vs CSSS) decreased (P < .10) steer postweaning gains, whereas postweaning implants (NSSS vs NNNN) increased (P < .10) DM intake; however, feed:gain ratio was not affected by implant strategy. Heifers in Exp. 2 that received implants had greater postweaning (P < .10) DM intakes and daily gains than heifers not receiving implants (NNNN); however, feed:gain ratios among treatment groups were unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)

Type and mixtures of high-moisture corn in beef cattle finishing diets.

In three experiments consisting of three finishing trials each, five corn storage and(or) feeding treatments were evaluated: 1) dry whole (DWC); 2) whole high-moisture (WHMC); 3) mixture (MHMC) of ground (GHMC) or rolled (RHMC) high-moisture corn with WHMC; 4) GHMC stored in a bunker silo; and 5) RHMC, corn stored whole but fed in rolled form. In Exp. 1, gains and feed intakes of steers fed whole corn (DWC vs WHMC) were similar. Steers fed GHMC and RHMC had lower (P less than .05) gains and intakes than steers fed whole corn. However, feed to gain ratios were 9% better (P less than .10) for steers fed RHMC than for steers fed GHMC. In Exp. 1 and 2, gains of steers fed MHMC were intermediate to gains of steers fed whole (DWC and WHMC) or processed corn (GHMC and RHMC). Feed to gain ratios of steers fed whole or processed corn were similar to feed to gain ratios of steers fed MHMC. In Exp. 3, steers fed 28.6% moisture GHMC had lower (P less than .05) intakes and feed to gain ratios than steers fed 22.5% moisture GHMC. Intakes and feed to gain ratios decreased 1.2 and 1.4%, respectively, for each 1% increase in corn moisture. Data are interpreted to mean that the relative effect of corn moisture content on cattle performance depends on form of corn fed; positive associative effects of MHMC are negligible, but RHMC has a greater feed value than GHMC.

Roughage sources in beef cattle finishing diets.

In four feeding trials with beef steers, corn silage (CS), alfalfa hay (AH), and alfalfa silage (AS) were compared as roughage sources in dry-rolled (DRC); dry whole (DWC); ground, high-moisture (GHMC); and whole, high-moisture corn (WHMC) fattening diets. In processed corn diets (DRC and GHMC), steers fed CS had lower DMI (P less than .05) and feed:gain ratios (P less than .10) than steers fed AS as the roughage source. In a separate trial, greater gains (P less than .10) and lower feed:gain ratios (P less than .05) were found during the initial feeding period, which included the adaptation phase, for steers fed CS vs steers fed AH as the roughage source. Over the entire feeding period, lower (corn type x roughage source interaction, P less than .05) feed:gain ratios were found in GHMC diets when CS was fed as the roughage source; feed:gain ratios were similar in steers fed DRC diets containing either CS or AH. Over the entire feeding period, similar performance was found among steers fed the various roughage sources in DWC diets; however, with WHMC diets, steers fed AS as the roughage source had lower feed:gain ratios than did steers fed AH (P less than .05) or CS (P greater than .10). In the processed corn diets, high correlations were found between diet NDF digestibility and gain (r = .80), intake (r = .68), and feed:gain ratios (r = -.66); similar trends were found in WHMC diets but not in DWC diets. These results suggest that the ideal roughage source to complement finishing diets may depend on corn processing method and feeding period (adaptation vs finishing).