The therapeutic efficacy and prophylactic activity of doramectin against Dictyocaulus viviparus in cattle

SUMMARY Three groups of 8, 4-month-old male Jersey or Jersey-cross calves were infected with 2400 Dictyocaulus viviparus L₃ larvae and either left untreated or injected subcutaneously with 200 μg/kg doramectin 5 or 25 days after infection (DAI). Lungworms were found in all untreated cattle (geometric mean = 49) at necropsy 39 or 40 DAI. None was found in any of the treated cattle. In a second experiment, groups of 6, 8-month-old calves were untreated or injected with 200 μg/kg doramectin 28, 21 or 14 days before each calf was challenged with 2700 D viviparus larvae. Lungworms were recovered at necropsy 32 to 34 DAI. The geometric mean worm burden in the untreated cattle was 550. This was reduced by 100%, 99.5% and 94.1% in calves treated with doramectin 14, 21 or 28 days, respectively, before infection. It was concluded that doramectin is a highly effective anthelmintic against D viviparus adult or L₄ infections of cattle, and that reinfection of treated cattle will be significantly reduced for at least 28 days after treatment.     

Optimizing Prepared Feed Ration for Gonad Production of the Green Sea Urchin Strongylocentrotus droebachiensis

Adult green sea urchins Strongylocentrotus droebachiensis were fed three different quantities (0.25, 0.50, 1.00% body weight/d) of a prepared feed during a 12‐wk experiment to determine the effect of food ration on gonad quantity and quality. A diet of kelp, Laminaria longicruris and/or L. digitata, fed at satiation (3% body weight/d) and urchins taken from the wild at the beginning and end of the experiment served as controls. Urchins fed prepared feed or kelp increased their percent gonad yield significantly over the experimental period. Affer 12 wk, individuals fed the prepared diet at 0.50 or 1.00% body weighffd had significantly higher percent gonad yields (mean ± SEM: 23.5 ± 0.6% and 23.4 ± 0.7%, respectively) than urchins fed at 0.25% body weight/d (18.0 ± 1.0%) or control animals given kelp (18.3 ± 0.8%). There was no significant difference in gonad yield between the 0.50 and 1.00% feeding levels. All feeding treatments had significantly higher percent gonad yields than urchins sampled from the wild at the end of the experiment that had recently spawned (2.8 ± 0.5%). There was no significant difference in gonad taste among urchins fed the prepared diet at 0.25% body weight/d, those given kelp, or those collected from the wild at the end of the experiment (good to very good ratings), but all of these treatments had significantly better tasting gonads than urchins given the prepared feed at 0.50 or 1.00% body weight/d (satisfactory ratings). Gonad taste rating of urchins fed a prepared diet was dependent on ration with greater feed amounts leading to worse tasting gonads (linear regression: r²= 0.68, P < 0.01). Gonad color, texture, and firmness did not differ significantly among any of the feed ration treatments or kelp control. Results suggest that the best ration for prepared feed would be 0.50% body weightld since this would optimize gonad yield while minimizing feed costs. Further research on prepared feeds is required to optimize both gonad color and taste.     

Contact with a sow in oestrus or a mature boar stimulates the onset of oestrus in weaned sows.

Post weaning anoestrus can represent a significant source of reproductive inefficiency in pig production. Although many factors such as breed, parity, season and nutrition are known to influence the interval between weaning and remating, the effect of the sow's social environment after weaning is largely unknown. For this experiment six groups of Large White/Landrace cross-bred sows weaned between August 1989 and March 1990 at a mean of 29 days after farrowing were used to investigate the effect of social environment on the onset of oestrus after weaning in the sow. Groups two, three or four sows were exposed in six replicates to the following four treatments: (1) 18 were isolated as controls, (2) 16 were housed next to an anoestrous ovariectomised sow and allowed 10 minutes physical contact with it daily, (3) 15 were housed next to an ovariectomised sow, induced into oestrus by the injection of 1 mg oestradiol benzoate, and allowed 10 minutes physical contact with it daily, and (4) 16 were housed next to a mature boar and allowed 10 minutes physical contact with it daily. Significantly more sows in treatments 3 and 4 showed oestrus within 10 days of weaning (P less than 0.05), and the onset of oestrus was more synchronised in the sows in treatment 3 than in any other treatment (P less than 0.001). The exposure of the weaned sows to an oestrous sow or a boar overcame the extension of the weaning to remating interval which occurred over the summer and in primiparous animals in other treatments.     

First report of Eimeria leuckarti infection in a horse in New Zealand

The protozoan parasite, Eimeria leuckarti was present in the ileal mucosa of a 7-month-old Thoroughbred filly which was destroyed with acute peritonitis resulting from perforation of the rectum. The parasite was considered to be of no clinical significance and the signs of colic noted prior to the rectal rupture were related to the vascular lesions caused by infection with Delafondia vulgaris.     

Strategy-dependent encoding of planned arm movements in the dorsal premotor cortex

The kinematic strategy encoded in motor cortical areas for classic straight-line reaching is remarkably simple and consistent across subjects, despite the complicated musculoskeletal dynamics that are involved. As tasks become more challenging, however, different conscious strategies may be used to improve perceived behavioral performance. We identified additional spatial information that appeared both in single neurons and in the population code of monkey dorsal premotor cortex when obstacles impeded direct reach paths. The neural correlate of movement planning varied between subjects in a manner consistent with the use of different strategies to optimize task completion. These distinct planning strategies were manifested in the timing and strength of the information contained in the neural population code.     

Inheritance of photosynthesis in a diallel among eight maize inbred lines from Iowa Stiff Stalk Synthetic

Summary Photosynthesis is a trait that should be improved in a selection program for yield potential of maize (Zea mays L.). We measured leaf CO₂-exchange rate (CER), an estimate of photosynthetic efficiency, of a complete diallel (parents, F₁ crosses, and their reciprocals) among eight inbred lines (4 with low and 4 with high CER) from the Iowa Stiff Stalk Synthetic maize population. Measurements were made during vegetative (CER 1) and grain filling (CER 2) stages of growth, and the experiment was conducted two years at one location. We measured large differences among crosses and significant heterosis for high CER at CER 1 (0.0 to 25.1%) and CER 2 (0.0 to 53.8%). Several crosses exhibited overdominant phenotypes for high CER at both growth stages, and one cross showed significant overdominance for low CER at CER 1. General combining ability effects (gca) were the largest components of among-cross variation at both CER 1 and CER 2. Specific combining ability (sca) also was significant at both growth stages, but gca effects were 9.4 and 4.8 times larger than sca effects at CER 1 and CER 2, respectively. Furthermore, high CER lines showed positive gca effects, and low CER lines showed negative gca effects at each stage. Maternal and reciprocal effects were not significant; thus, CER in these crosses was controlled largely by additive effects of nuclear genes. A high positive genotypic correlation (r=0.74) between CER 1 and CER 2 suggested that selection at either growth stage would improve CER throughout the growing season.Journal Paper No. J-9023 of the Iowa Agriculture and Home Economics Exp. Stn., Ames, Iowa. Project No. 1990.