Two controlled tests were conducted in 1981 and 1982 in dairy calves on the University of Kentucky research farm to determine activity of the bolus formulation of levamisole given at the dose rate of 8 mg/kg against naturally occurring infections of Ostertagia ostertagi. Removal efficacies of mature O ostertagi were 98% in the 1981 test (3 treated and 3 nontreated calves) and 94% in the 1982 test (7 treated and 8 nontreated calves). Against immature Ostertagia spp, removal efficacies were 100% and 65% for the 1st and 2nd tests, respectively. The calves were grazed on the same pasture as dairy calves in previous controlled tests in 1979 and 1980 where activity of levamisole against mature O ostertagi (data recently published) was much less than in the present tests. It does not appear that the poor performance in the early tests can be attributed to the drug resistance phenomenon. Data on overwinter survival (119 days) of free-living stages of gastrointestinal parasites on pasture were derived from the nontreated calves in the 1982 controlled test. The calves, raised helminth-free, were placed on the pasture on Apr 5, 1982. Helminths recovered at necropsy of the calves, besides O ostertagi, included Trichostrongylus axei, Nematodirus helvetianus, Nematodirus spp, Cooperia oncophora, Trichuris spp, and Moniezia spp. The lung-worm, Dictyocaulus viviparus, previously found in cattle on the farm, was not found in these calves.

Levamisole bolus formulation was administered in single doses, at rates of 5.8 to 8.1 mg/kg body weight, in 3 controlled tests in male dairy calves (n = 22) in Kentucky. Removals of natural infections of adult Ostertagia ostertagi were 70% and 76% for calves from a hear with a history of regular treatments with levamisole and 85% for calves from a herd receiving levamisole occasionally. Activity against other abomasal nematodes and lungworms was also evaluated.

Seventeen dairy calves, raised lungworm-free, were used in an experiment to determine whether lungworm (Dictyocaulus viviparus) larvae survived on a pasture in central Kentucky during the winter of 1979/1980. On Apr 22, 1980, the calves were placed on pasture. Three calves were put on pasture A, on which no cattle had grazed for over 20 years. Fourteen calves were put on pasture B, which had been vacant since Dec 12, 1979 (132 days before beginning of experiment), when several lungworm-infected calves had been removed from the pasture. Fecal samples from the 17 calves were examined for lungworm larvae at weekly intervals for about 6 weeks; lungworm larvae were not found in any of the 3 calves on pasture A, but were found in 12 of 14 (86%) calves on pasture B. One calf from pasture A and 3 calves from pasture B were euthanatized 37 days after being placed on pasture; lungworms were recovered from 1 calf from pasture B.

Dairy calves (n = 18) were used in controlled tests to evaluate activity of levamisole against abomasal nematodes and lungworms. Two formulations of levamisole, injectable (experiment A) and bolus (experiment B), were given in single doses at rates of 6 mg/kg of body weight and 5.4 to 10.2 mg/kg (5.4, 7.6, 8.0, 8.8, or 10.2 mg/kg), respectively. Experiment A included 4 treated and 4 nontreated calves and experiment B consisted of 5 treated and 5 nontreated calves. Aggregate removals of Ostertagia spp (4th stage), Ostertagi (adult), Trichostrongylus spp (4th stage), and T axei (adult) were 0%, 54%, 86%, and 95%, respectively, for injectable treated calves and were 0%, 23%, no data, and 85%, respectively, for bolus-treated calves. Haemonchus spp, present in small numbers, were completely removed from treated calves in experiment A. Several possible explanations are discussed regarding poor removal activity of levamisole by both formulations against O ostertagi. Removal activity was 95% and 100% against Dictyocaulus viviparus for injectable-treated and bolus-treated calves, respectively.

A completely automated device for quantitatively measuring and sampling digesta entering the proximal duodenum of cattle is described. The system operates according to volume of flow from intestinal reentry cannulas. Size of subsample, frequency of sampling and rate of digesta return may be varied according to experimental objectives. The apparatus has the following features: (1) digesta temperature control, (2) a rotary sample collector to obtain individual subsamples, and (3) an event recorder to indicate flow cycle time parameters. The system described was constructed for cattle and may be used with animals standing or lying in the special holding crate. The apparatus has logged in excess of 1,900 hr of continuous collection (53 periods of 36 hr each) with only minor malfunction. Repetitive sampling of pooled digesta has produced coefficients of variation for volume, dry matter flow and percentage dry matter in digesta samples of 2.68, 2.81 and 1.81%, respectively. On the basis of incomplete recovery (range 71 to 97%) of chromic oxide from animals during collection periods (24 hr fed vs 24 hr recovery at duodenum), it is suspected that some inhibition to normal flow through the cannula occurs during sampling. Experiments have been conducted in which several parameters of interest were measured and total collection of digesta was compared via spot sampling (500 ml digesta at 6-hr intervals for 48 hr). When corrected to 100% chromic oxide recovery, differences between techniques for estimates of total digesta flow, organic matter and nitrogen entering the duodenum were small and not significant.

There are over 70 known mineral inten'elationships in which an additional dietary quantity of one mineral element wilt influence absowtion or utilization of another mineral element.As the animal ages, the readiness of availability of stored mineral dements in the bone decreases.Animals do adapt to reduced dietary intake of minerals as shown for Ca by reducing fecal excretion and increasing absorption.The adaptation, however, may occur simultaneously with a reduction in milk production.Borderline deficiency or insufficiency o£ mineral elements leads to decreased feed intake and milk production.Diagnosis is extremely difficult.A large proportion ok commonly used feedstuffs are below the required concentration of at least one mineral element for high milk production.Since few dairymen know how much of each mineral element is in their cows' diet, milk production may unwittingly suffer from mineral deficiency, insufficiency, or toxicity.Excessive rather than too little dietary Ca during the dry period prior to calving is likely contributing to an increased incidence of milk fever.Basically, blood P must be maintained by absorption from the gut as there is no known specific mechanism/or bone resorption.Therefore, it is important always to include adequate P in the diet.Too little Mg may be causing problems that are not well understood, or widely appreciated.Supplemental K is