Use of amprolium for the control of coccidiosis in pheasants.

Amprolium administered in feed during the first 4 weeks of life at a level of 0.0175% protected pheasants against three major pathogenic species of coccidia (Eimeria colchici, E. duodenalis, and E. phasiani) when they were exposed at 2 weeks of age. The difference was significant when mortalities were compared between medicated infected (3%) and unmedicated infected (35%) pheasants. The manufacturer's proposed level (0.0175%) and twice the proposed level (0.0350%) of amprolium had no significant effect on weight gains or mortality in the safety trial. Amprolium residues found in the muscles and livers of pheasants that received either level of amprolium did not exceed the tolerance levels for chickens and turkeys permitted by the U.S. Food and Drug Administration.

The use of sodium taurodeoxycholate for excystation of Eimeria tenella sporozoites.

As an in vitro excystor, sodium taurodeoxycholate (TDC) released 80--90% Eimeria tenella sporozites, in contrast to 0--15% excystation by six other bile salts or bile extracts, and pooled chicken bile in 90 min at 37 C with continuous agitation. Pooled chicken bile required 4 to 4 1/2 hr to excyst similar percentages of sporozoites. Prolonged incubation with other bile salts and bile extracts excysted most sporozoites, but killed them. When the incubation temperature was raised to 44 C, TDC excysted 100% of the sporozoites in 60 min. In all other bile salts or bile extracts, the percentage of excystation increased greatly at 44 C, but none equalled that of TDC. The molecular similarity of TDC to a naturally occurring bile salt of chickens is presented as an explanation for the superior performance of TDC as an excystor. Data are examined to minimize the possibility that excysting activity of TDC can be attributed to other bile salts present at impurities.

Relationship of serum somatomedin-like activity and fibroblast proliferative activity with age and body weight gain in sheep.

The relationship between serum growth factors and body weight gain was examined in five Dorset lambs. The lambs were weighed and bled by jugular puncture at 2-week intervals between 2 and 18 weeks of age. Somatomedin-like activity (Sm) declined from initially high concentrations at 2 weeks to fairly constant concentrations between 6 and 18 weeks. Relative weight gain--i.e., gain expressed as a percentage of body weight--declined in a manner similar to that of Sm. Mean relative weight gain and mean Sm for the eight 2-week intervals were significantly related (r = .84). Absolute body weight gain--i.e., gain expressed in kilograms--remained fairly constant throughout the study and was not significantly correlated to Sm (r = .15). Serum fibroblast proliferative activity (FPA) was measured as a possible indicator of collective activities of serum growth factors. FPA initially followed a pattern similar to that of Sm, decreasing between 2 and 6 weeks and plateauing until 12 weeks. After 12 weeks, FPA increased to concentrations similar to those observed at 2 weeks. The increase in FPA after 12 weeks was apparently due to an increase in a non-Sm growth factor and had no obvious relationship to body weight changes. Results of the in vitro cell assay system might have been more meaningful if cell type(s) other than WI-38 fibroblasts (e.g., myogenic cells) had been used for estimating collective activities of serum mitogenic factors. The data suggest that serum Sm-like activity may be important in the regulation of growth in sheep.

Intramammary infusions of cytochalasin B and dimethyl sulfoxide do not suppress milk secretion in the goat.

Cytochalasin B, an intracellular microfilament antagonist, was evaluated for its capacity to inhibit milk secretion in the goat. Intramammary infusions of the drug via teat canal in amounts to 6 mg had no effects on yields or fat and protein contents and minor, if any, effects on somatic cell counts of consecutive 12-h milkings. Our results suggest that the apical plasma membrane of lactating cells is impermeable to cytochalasin B and that the reduced secretion of lactose and casein caused by the drug in vitro may arise from its interference with glucose uptake at the base of cells. Dimethylsulfoxide, which we used (2 ml) in infusates to solubilize cytochalasin B, also was without effect on the foregoing lactation characteristics.

Relationship of serum somatomedin-like activity and fibroblast proliferative activity with age and growth in the rat.

An assay for fibroblast proliferative activity (FPA) using human lung fibroblasts, WI-38, was described. The assay was responsive to varying rat serum levels and was not influenced by direct growth hormone (GH) addition. The relationship of serum growth factors to age and body weight was examined in the rat. In study 1, serum was obtained from lean Zucker rats at 3, 5, 7, 9, 11 and 30 wk of age. Six samples were taken at each age and serum samples were analyzed for somatomedin-like activity (Sm) and fibroblast proliferative activity (FPA). Serum Sm was not different at any of the sampling ages. FPA was low at 3 wk, but was higher and constant from 5 wk to 30 wk. In study 2, 73 lean Zucker rats (7 wk of age) were maintained on laboratory chow and water ad libitum for 4 wk, and then serum was obtained by decapitation. The rats were ranked according to each of four different criteria: average daily gain (ADG) for the duration of the study, ADG for the fourth week, total body protein and total body fat. Serum Sm, FPA and insulin concentrations on the top 10 and bottom 10 rats of each ranking were compared. Neither FPA nor insulin was significantly different for any ranking. Serum Sm was significantly higher in the top 10 rats ranked by ADG for the duration of the study. Sm was not significantly different in rats ranked by body weight, total body protein or total body fat. The data suggest that serum somatomedin-like activity (Sm) may be important in the earlier stages of growth in rats.