Mast cell density during initiation and progression of the local Shwartzman reaction.

OBJECTIVE AND DESIGN: To quantify the number of mast cells in the skin of rabbits during initiation and progression of the local Shwartzman reaction. MATERIALS: Thirty New Zealand rabbits were divided in two groups (n = 15/group). One group was subjected to the Shwartzman reaction and the other group served as control. Subsequently, animals were further subdivided in six groups of five animals each according to time of euthanasia. TREATMENTS: The local Shwartzman reaction was induced by two inoculations of Salmonella typhimurium lipopolysaccharide. Preparatory inoculation was given intradermally and, 24 h later, the provocative injection was administered intravenously. Controls were subjected to the same procedure but received saline. After provocative injection animals were killed at 1, 8, and 15 days. METHODS: Skin samples were fixed in Carnoy's solution and mast cells were identified employing a low pH toluidine blue stain. Numbers of mast cells were determined per square millimetre and, subsequently, those cells degranulated were identified and quantified to obtain absolute values. A Student's t test was initially used to compare Shwartzman versus controls at each time point. Subsequently, an ANOVA test employing a factorial experiment was used to assess a possible interaction between time of euthanasia and treatments. RESULTS: The values were transformed (natural logarithms) for appropriate statistical comparisons. Independent comparisons at each time point showed that Shwartzman groups had higher numbers of mast cells than controls at 1 and 8 days, but not at 15 days (5.71 +/- 1.00 Vs. 2.40 +/- 0.58, P < 0.005; 3.77 +/- 0.90 Vs. 2.33 +/- 0.56, P < 0. 025, and 2.61 +/- 0.25 Vs. 2.39 +/- 0.39, P > 0.05, respectively). Degranulated cells were numerous in Shwartzman groups, particularly at day 1 (3.48 +/- 0.78) and less obvious at day 8 (0.72 +/- 0.50), but were scarce by day 15 (-0.67 +/- 0.99) as well as controls (-0.68 +/- 0.91). The factorial experiment demonstrated that the Shwartzman reaction and time of euthanasia were independently significant (P < 0.005) but their interaction at day 1 was the major contributor (P < 0.005). Tukey's w pairwise comparisons of means confirmed that the Shwartzman group killed at day 1 was significantly different from the others (P < 0.05). CONCLUSIONS: Mast cells significantly increase in the early stages of the local Shwartzman reaction. Thus, mast cells are a highly dynamic cell population, which have a prominent role during the acute phase of this lipopolysaccharide-induced inflammatory reaction but not during healing.

Alfalfa and escape protein supplements for grazed corn residues.

Two calf corn-residue grazing trials were conducted to evaluate the effect of supplementing with two alfalfa hays (Medicago sativa), varying in their amount of CP and ADF, with and without escape protein (EP). In Trial 1, heifers (204 kg) grazed (1.36 heifers/ha) non-irrigated fields for 92 d. No difference (P > .05) in ADG was found when medium-protein (16.3% CP) and high-protein (18.0% CP) alfalfa hays were provided at 2.7 kg of DM.heifer-1.d-1. In Trial 2, 60 steers (257 kg) were supplemented individually with medium-protein (17.6% CP) alfalfa hay, 1.86 (MPL) and 2.27 kg DM (MPH), and one level of high-protein (18.7% CP) alfalfa hay, 1.86 kg DM (HPL). In a 2 x 3 factorial arrangement of treatments, steers were fed with or without EP (113 g.steer-1.d-1 from blood meal and corn gluten meal). Steers grazed a non-irrigated corn residue field (2.58 steers/ha) for 57 d and were watered and individually supplemented overnight. Diet quality and composition was estimated by collecting extrusa samples twice each week using four esophageally fistulated steers. No effects of alfalfa protein content or level (P > .05) were reflected in gain: 357, 309, and 326 g.steer-1.d-1 for steers receiving MPL, MPH, or HPL alfalfa treatments, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Diet composition and gains of escape protein-supplemented growing cattle grazing corn residues.

Effect of level and method of escape protein (EP) supplementation on weekly steer performance and their diet composition were evaluated in two corn residue grazing trials. In Trial 1, 60 steers (average weight 239 kg) received .8 kg.animal-1.d-1 of a 50% CP supplement to provide one of six levels of EP (60, 88, 116, 144, 172, or 200 g.animal-1.d-1). Steers grazed (2.2 animals/ha) nonirrigated fields (NIF) for 63 d. In Trial 2, 59 steers (average weight 219 kg) grazed either NIF (1.97 animals/ha) or irrigated fields (IF, 3.96 animals/ha) and were supplemented with 60, 95, 130, 165, or 200 g of EP.animal-1.d-1. In a 2 X 5 X 2 factorial arrangement, treatments were IF vs NIF, level of protein, and two supplementation methods: 1) feeding the lowest level of EP (60 g) for 21 d then for the remaining 42 d feeding one of the five EP levels or 2) feeding each EP level continuously. Weekly diet composition was evaluated using four esophageally fistulated steers. In Trial 1, no EP effect (P greater than .05) was found up to 20 d, but EP affected (P less than .05) ADG from d 20 to 34, resulting in 3.35 g of ADG/g of EP. In Trial 2, steers grazing NIF had higher (P less than .01) ADG than those grazing IF (644 vs 414 g/animal). Steer daily gains were increased (P less than .05) by level of EP but were not affected (P greater than .05) by the method of supplementation, indicating that EP supplementation was not needed during the first 21 d.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in availability and nutritive value of different corn residue parts as affected by early and late grazing seasons.

Two early- (EG) and two late-season (LG) corn-residue grazing trials were conducted either from October to December or from December to March (1987 and 1988) using both nonirrigated and irrigated fields. Initial availability, disappearance, and nutritive value of different corn residue components were estimated. Stocking rates were 1.97, 2.20, 1.36, and 2.58 animals/ha for the two EG and LG nonirrigated fields (NIF), respectively, and 3.96 animals/ha for EG irrigated fields (IF). Samples were collected three times throughout the grazing period. In one of the LG trials, samples were collected 30 d before the grazing season began for measurement of weathering damage. Composite samples were analyzed for CP, ADF, ADIN, and in vitro DM (IVDMD) and OM (IVOMD) disappearance. Ruminal escape protein (EP) content was assessed using a Dacron bag technique. Weathering reduced (P less than .02) the amount of leaf blade available by 42% during a period of 30 d before the LG season in Trial 2. Grain, husks, and leaf blades disappeared to the greatest degree (P less than .05) during either grazing season. More than 90% of the grain disappeared during the first 30 d, regardless of grazing season. Overall IVDMD for NIF grain, husks, leaf blades, stems, and cobs across the EG and LG trials were 98.6, 68.4, 42.0, 41.0, and 48.1%, respectively. Corn residue fractions from IF had a lower (P less than .05) IVDMD than did NIF fractions. Grain from NIF was 20% higher (DM basis) in EP than grain from IF (Trial 2). Grain left in the field was the most important source of CP and EP for calves grazing corn residues. Husks and leaf blades were selected by calves; husks were the roughage fraction with the highest nutritive value.