Effect of rotation frequency and weaning date on forage measurements and growth performance by cows and calves grazing endophyte-infected tall fescue pastures overseeded with crabgrass and legumes.

A grazing study was initiated in April 2000 and continued through three calving and weaning cycles (ending July 2003) to investigate the effects of rotational grazing management (twice monthly [2M] vs. twice weekly [2W]) and weaning date (mid-April [EARLY] vs. early June [LATE]) on production of fall-calving cow-calf pairs (495 +/- 9.6 kg initial BW) grazing Neotyphodium coenophialum-infected tall fescue (Festuca arundinacea Schreb.) overseeded with legumes and crabgrass. Secondary objectives of the experiment were to monitor differences in quantity and quality of available forage and to evaluate changes in forage species composition. Pastures were dominated by tall fescue throughout the study, and the proportion of basal cover was greater (P < 0.05) in 2M than in 2W pastures. The percentage of legumes was very low across all treatment combinations, but the percentage of crabgrass continued to increase (P < 0.05) linearly and quadratically across years for both summer and fall sampling periods, regardless of rotation or weaning program. In vitro DM disappearance and mineral concentrations varied minimally because of rotation frequency or weaning date. Rotation frequency did not substantially affect (P = 0.11 to 0.97) cow BW, hay offered, milk production, calving interval, calf birth weight, or actual or adjusted weaning weights; however, 2M cows had 0.3 units higher (P < 0.05) BCS at the time of breeding than 2W cows. Calves weaned late had greater (P < 0.05) actual weaning weight and weighed more (P < 0.05) on the LATE weaning date than on the EARLY weaning date, but 205-d adjusted weaning weights did not differ (P = 0.74) across weaning dates. Therefore, rotation frequency and/or weaning date had little effect on forage species composition or forage quality. In addition, the rapid rotation program offered little advantage with respect to animal performance, and weaning fall-born calves grazing endophyte-infected tall fescue pastures at approximately 189 d of age seemed to be detrimental to calf performance compared with delaying weaning until 243 d of age.

Effect of dietary mannan oligosaccharides and(or) pharmacological additions of copper sulfate on growth performance and immunocompetence of weanling and growing/finishing pigs.

Two experiments were conducted to determine the efficacy of mannan oligosaccharides (MOS) fed at two levels of Cu on growth and feed efficiency of weanling and growing-finishing pigs, as well as the effect on the immunocompetence of weanling pigs. In Exp. 1, 216 barrows (6 kg of BW and 18 d of age) were penned in groups of six (9 pens/treatment). Dietary treatments were arranged as a 2 x 2 factorial consisting of two levels of Cu (basal level or 175 ppm supplemental Cu) with and without MOS (0.2%). Diets were fed from d 0 to 38 after weaning. Blood samples were obtained to determine lymphocyte proliferation in vitro. From d 0 to 10, ADG, ADFI, and gain:feed (G:F) increased when MOS was added to diets containing the basal level of Cu, but decreased when MOS was added to diets containing 175 ppm supplemental Cu (interaction, P < 0.01, P < 0.10, and P < 0.05, respectively). Pigs fed diets containing 175 ppm Cu from d 10 to 24 and d 24 to 38 had greater (P < 0.05) ADG and ADFI than those fed the basal level of Cu regardless of MOS addition. Pigs fed diets containing MOS from d 24 to 38 had greater ADG (P < 0.05) and G:F (P < 0.10) than those fed diets devoid of MOS. Lymphocyte proliferation was not altered by dietary treatment. In Exp. 2, 144 pigs were divided into six pigs/pen (six pens/treatment). Dietary treatments were fed throughout the starter (20 to 32 kg BW), grower (32 to 68 kg BW), and finisher (68 to 106 kg BW) phases. Diets consisted of two levels of Cu (basal level or basal diet + 175 ppm in starter and grower diets and 125 ppm in finisher diets) with and without MOS (0.2% in starter, 0.1% in grower, and 0.05% in finisher). Pigs fed supplemental Cu had greater (P < 0.05) ADG and G:F during the starter and grower phases compared to pigs fed the basal level of Cu. During the finisher phase, ADG increased when pigs were fed MOS in diets containing the basal level of Cu, but decreased when MOS was added to diets supplemented with 125 ppm Cu (interaction, P < 0.05). Results from this study indicate the response of weanling pigs fed MOS in phase 1 varied with level of dietary Cu. However, in phase 2 and phase 3, diets containing either MOS or 175 ppm Cu resulted in improved performance. Pharmacological Cu addition improved gain and efficiency during the starter and grower phases in growing-finishing pigs, while ADG response to the addition of MOS during the finisher phase seems to be dependent upon the level of Cu supplementation.

Effects of calendar date and summer management on the in situ dry matter and fiber degradation of stockpiled forage from bermudagrass pastures.

Limited information is available that describes the disappearance kinetics of bermudagrass (Cynodon dactylon L. Pers.) during fall and early winter. Five ruminally cannulated, crossbred steers (387 +/- 18.3 kg) were used to determine the effects of calendar date and previous summer management on the in situ degradation kinetics of DM and NDF for forage clipped from stockpiled 'Greenfield' bermudagrass pastures. Forage was stockpiled at two sites following summer hay or pasture management, and samples were taken outside (GRAZED) and under caged exclosures (UNGRAZED) at 4-wk intervals beginning October 17, 1997, and ending January 9, 1998. No effort was made to remove or avoid contaminate species. Concentrations of NDF increased (P < 0.001) to a maximum for UNGRAZED forages at the hay site between October 17 and December 12, but sampling date had no effect (P = 0.627) on concentrations of NDF at the pasture site. Concentrations of ADF and lignin increased (P < or = 0.023) during at least one sampling interval in UNGRAZED forages at both sites. At the hay site, degradation rates of DM decreased (P < 0.001) by 0.013/h for UNGRAZED forage between October 17 and January 9, whereas the effective ruminal degradability of DM decreased (P < 0.001) by 33.5% during the same time period. Fractional degradation rates of NDF for UNGRAZED forages at the hay site decreased (P < 0.001) by 0.014/h between October 17 and November 14 but did not change (P > or = 0.077) throughout the remainder of the study. The effective ruminal degradability of NDF decreased (P < 0.001) by 33.8% between the first and last sampling date. At the pasture site, sampling date did not affect (P = 0.458) rates of DM degradation, but the effective degradability of DM for UNGRAZED forages decreased (P = 0.001) by 19.0% from October 17 to December 12. Rates of NDF degradation for UNGRAZED forages did not differ (P > or = 0.113) on the first three sampling dates, but the rate on January 9 was slower than that observed on October 17 (P = 0.025) and November 14 (P = 0.044). The effective degradability of NDF decreased (P < 0.001) by 19.2% between October 17 and December 12. These data indicate that stockpiled bermudagrass should be used during a limited window during the late fall; after this time, the nutritive value becomes very poor.

Glycoconjugates as components of receptors for Bordetella avium on the tracheal mucosa of turkeys.

Bordetella avium is an important respiratory tract pathogen of turkeys. In common with other pathogenic bordetellae, B avium manifests a tissue tropism for cilia of the respiratory tract epithelium. To determine the molecular characteristics of the host cell receptors for B avium, we used hemagglutination and in vivo adherence assays. Carbohydrates, mucus, sialic acid-specific lectin, and other glycoconjugates were evaluated for their ability to competitively inhibit binding of B avium to host cells. The gangliosides, GD1a and GT1b, completely inhibited hemagglutination, whereas N-acetylneuraminic acid (sialic acid) partially inhibited hemagglutination. Adherence to turkey tracheal mucosa in vivo was significantly (P < 0.01) inhibited by GD1a and GT1b gangliosides, N-acetylneuraminic acid, bovine submaxillary mucin, and horseshoe crab (Limulus polyphemus) lectin. Treatment of the tracheal mucosa with neuraminidase also inhibited adherence of B avium. We conclude that N-acetylneuraminic acid and the gangliosides, GD1a and GT1b, may be important components of the tracheal mucosa receptor for B avium in turkeys.

Identification of Bordetella avium antigens recognized after experimental inoculation in turkeys.

Sera and tracheal washings (TW) were used to identify antigens of Bordetella avium recognized during experimentally induced bordetellosis in young turkeys. Pooled sera and TW were examined for antibody by a microtitration agglutination test and by western immunoblotting. In addition, comparable samples collected from 1-day-old turkeys and uninoculated control turkeys also were examined. At least 8 outer membrane proteins of B avium were recognized in immunoblots of sera and TW from infected turkeys. Reactivity of TW in immunoblots was qualitatively similar but less intense, compared with reactivity of corresponding sera collected on postinoculation (PI) weeks 2, 3, and 4. Molecular weights of the major outer membrane proteins of B avium recognized by sera and TW at PI week 4 were 100,000, 97,000, 36,000, 31,000, 21,000, 18,000, 14,000, and less than 14,000. A protein with a molecular weight of 55,000 reacted nonspecifically in all samples tested. Antibody, detectable by microtitration agglutination, was in sera of 1-day-old turkeys and in sera and TW of B avium-infected turkeys during PI weeks 2 to 4.

A comparison of outer membrane proteins and surface characteristics of adhesive and non-adhesive phenotypes of Bordetella avium.

The outer membrane protein profiles of four adherent and one reduced-adherence mutant phenotype of Bordetella avium were compared; a non-adherent B. avium-like organism isolated from turkeys was also examined. The organisms were grown on brain-heart infusion agar at 35 C for 36 hours. In addition, one of the adherent phenotypes was grown at 18 C and 40 C. The outer membrane proteins were isolated by sonication and detergent extraction with Triton X-100. Surface characteristics of intact bacteria were examined using negative stain and transmission electron microscopy. The adherent phenotypes had identical protein profiles by electrophoresis. The non-adherent B. avium-like organism lacked at least five of the proteins present on the adherent strains. The non-adherent mutant phenotype had a protein profile similar to that of the adherent organisms, although several proteins were present in much lower concentrations. Fimbriae were found on both adherent and non-adherent organisms. By comparing protein profiles of adherent and non-adherent B. avium we were able to make a preliminary determination of the membrane proteins that lack adhesive properties.

Passive immunization versus adhesion of Bordetella avium to the tracheal mucosa of turkeys.

Three-week-old turkeys were passively immunized with convalescent serum or treated with tracheal washings from turkeys infected with Bordetella avium. Western blot analysis of the convalescent serum and tracheal washings revealed at least two bands of interaction with outer membrane protein preparations of B. avium. Adherence of B. avium in vivo to tracheal mucosa was determined and compared in treated and untreated turkeys. Passive immunization with convalescent serum reduced adherence of B. avium to the tracheal mucosa in a dose- and time-dependent manner. Adherence was significantly inhibited (P less than 0.01) when turkeys were treated intravenously with 1 ml of undiluted serum either 1 or 6 hours previously. Incubation of the bacterial inoculum with convalescent tracheal washings or application of the washings to tracheal segments before adherence determination in vivo resulted in a significant (P less than 0.01) decrease in adherence. These results indicate that adherence of B. avium to tracheal mucosa is inhibited by substances (antibody) present in both serum and tracheal secretions of convalescent turkeys.