High Feeding Level Research Articles

Effects of two different medium-chain triglycerides (tri C8:O and tri C12:O) on liver lipids in the growing rat.

Results presented in this study emphasize the long-term effects of dietary fatty acid chain length on some biochemical parameters of the liver in the growing rat. High levels of medium-chain fatty acids feeding (C8:O and C12:O) from 40 to 340 g of body weight induced liver growth and lipid contents intermediary between values recorded with a lipid-free diet and with a diet containing long-chain fatty acids. No steatosis was recorded but neutral lipid contents appeared to be correlated with the dietary fatty acid chain length while phospholipid contents remained much more stable. In the four tested nutritional conditions, only dodecanoïc or lauric acid (C12:O) feeding induced important alterations in the fatty acid pattern of liver neutral lipids. Medium-chain fatty acids, and even lauric acid which was intensely esterified in adipose tissue triglycerides, did not appreciably modify the fatty acid composition of liver phospholipids and were not esterified in it.

Ascorbic acid and l-gulonolactone oxidase in lagomorphs

1. 1. The activity of l-gulonolactone oxidase (EC 1.1.3.8) in the liver of eastern cottontail rabbits ( Sylvilagus floridanus) is about 10-fold greater in winter than in summer. 2. 2. l-gulonolactone oxidase activity is low and tissue ascorbate high during all seasons in snowshoe hares ( Lepus americanus). 3. 3. Liver contents of ascorbate fall to low levels in L. americanus fed on rabbit chow in the laboratory. 4. 4. The activity of l-gulonolactone oxidase in liver of Sylvilagus and Oryctolagus is depressed by feeding high levels of l-ascorbic acid. 5. 5. The New Zealand White breed of domestic rabbit ( Oryctolagus cuniculus) has considerably higher levels of l-gulonolactone oxidase and liver ascorbate than does the Dutch breed. 6. 6. In a wild population of Oryctolagus sampled in Australia l-gulonolactone oxidase levels were intermediate between those of the two domestic breeds and more variable than either.

The effect of protein content on the response of lactating cows to level of concentrate feeding

SUMMARYSeventy-two lactating dairy cows were used in a 4x 3 factorial experiment to assess the effects of the protein content of concentrates on the response to concentrate feeding level. Concentrates containing 12,18 and 24% crude protein in the dry matter were given at each of four levels of feeding: 0·25, 0·36, 0·47 and 0·58 kg/kg milk for a 7-week experimental period. Milk yield, milk energy output, liveweight change and the percentage solids-not-fat and protein in the milk were significantly affected by both the level of concentrate feeding and the protein content of the concentrate. Response curves for the effect of level of concentrate feeding on milk output and liveweight change were computed for each of the three protein levels, and although there was no significant interaction between these two main factors the benefit from increased protein in the concentrate was shown to depend partly on the level of feeding at which the concentrate was used. At low feeding levels the response to an increase in protein content of the concentrate tended to be smaller than that obtained at high feeding levels. At no stage was there any marked response to protein content in the concentrate above 18%. The response curves have been used to demonstrate the interchangeability of level of concentrate feeding and protein content of the concentrate as means of supporting a given level of milk production.

Growth of Capitella capitata cultured on various levels of detritus derived from different sources1

Capitella capitata was cultured on three levels of five organic sources of detritus (Spartina alterniflora, Zostera marina, mixed cereal, Fucus, and Gracilaria sp.). Standing crops increased with increasing food levels of all types of detritus, with a general gradation in the nutritional value of marsh grass < eelgrass < mixed cereal < rockweed < Gracilaria.The best index of nutritional value was the amount of nitrogen supplied to the polychaetes. The biomass obtained at the highest feeding level of nitrogen‐poor eelgrass was about the same as that at the medium feeding level of rockweed. Once a given level of nitrogen (50 mg m−2 d−1) was available, caloric value apparently affected the nutritive quality of the detritus: the high feeding levels of rockweed resulted in greater standing crop of the polychaete than diets of Gracilaria containing similar levels of nitrogen but fewer calories.

COMPETITIVE DISPLACEMENT OF PANONYCHUS ULMI (ACARINA: TETRANYCHIDAE) BY ACULUS SCHLECHTENDALI (ACARINA: ERIOPHYIDAE) IN APPLE ORCHARDS

AbstractEvidence for competitive deplacement of Panonychus ulmi (ERM) from apple trees via Aculus schlechtendali (ARM) by what is thought to be a foliage conditioning mechanism is presented. Previous feeding of ARMs at high and moderate density levels near or below the economic threshold for this phytophagous mite on apple reduced the build-up of the ERM in 3 years of field experiments on Red Delicious trees and during a single season on McIntosh apple foliage. Comparative tests measuring oviposition rates of the ERM on excised apple leaves which had sustained high and low levels of previous rust mite feeding gave results similar to field experiments. The applied aspect of how this interspecific relationship can be managed in the context of an integrated mite management program for apples is discussed.

The effect of two feeding levels of diets containing field-cured or frozen Rhodes grass (Chloris gayana), on digestibility and rumen metabolites in sheep

SummaryA digestibility and metabolism experiment was carried out to study the effect of two levels of feeding Rhodes grass-concentrate mixed diets when the grass had been preserved as hay or as frozen grass. Twenty Awassi lambs were used.The method of preserving the Rhodes grass did not affect the digestibility of dry matter, crude protein or nitrogen-free extract. However, the digestibility of energy and crude fibre was lower with the hay treatments.A consistent trend towards higher digestibility of the diets' constituents was observed with the high level of feeding.Acetic acid concentration in the rumen was lower with the hay than with frozen grass. Feeding the high level resulted in higher concentrations of volatile fatty acids in the rumen.A highly significant effect of the level of feeding on the C2/C3 ratio was observed; the high level of feeding resulted in a lower C2/C3 ratio

Toxicity studies with methyl N-[[(methylamino)carbonyl]oxy]-ethanimidothioate

Methomyl exhibited a low order of chronic oral toxicity even though it exhibited high acute oral toxicity. When applied dermally to rabbits, aqueous suspensions of methomyl exhibited low acute toxicity. Subacute oral tests in rats indicated no cumulative oral toxicity, and plasma cholinesterase activity for test rats was similar to that of the controls. Also, when methomyl was applied to intact skin of rabbits, 15 daily treatments produced no cumulative effects. Fish residue studies showed no build-up of methomyl in the tissues and no signs of a compound-related effect were noted in a 30-day feeding study in Japanese quail. Methomyl fed to pregnant New Zealand white rabbits on Days 8–16 of gestation at dietary levels of 0, 50, and 100 ppm was not teratogenic. In a 3-generation, 6-litter reproduction study with rats, at the same dietary levels, methomyl had no adverse effects upon reproduction and lactation performance; no pathologic changes were observed in weanling pups of the F3b generation. The oral administration of 28 mg/kg to adult hens did not result in demyelination of the sciatic nerve. Rats of both sexes were fed nutritionally complete diets containing 0, 10, 50, 125–500, and 250 ppm of methomyl in a 90-day feeding study and 0, 50, 100, 200, and 400 ppm of methomyl in a 22-month feeding study. The weight gain for the high-level males was significantly lower than that of the controls. No clinical, hematological, biochemical, urinary, or pathologic evidence of toxicity was observed at 90 days. However, in the 22-month study, decreased hemoglobin values were noted in the two higher level female test groups. A significantly higher testis/body weight ratio was observed in the high-level males. Histopathologic alterations were observed in the kidneys of male and female rats receiving 400 ppm and the spleens of the female rats receiving 200 and 400 ppm of methomyl. Beagle dogs of both sexes, fed nutritionally complete diets containing 0, 50, 100, and 400 ppm of methomyl in 90-day and 2-year feeding studies, showed no nutritional, clinical, urinary, or biochemical evidence of toxicity; in the latter study, an additional dietary level of 1000 ppm caused some clinical signs of toxicity and mortality. Similar to the findings in the 22-month feeding study in rats, histopathologic changes were observed after 2 years in the kidney and spleen as well as in the liver at the two higher feeding levels. In addition, dogs receiving the high-level diet showed a compound-related anemia. There was no evidence of carcinogenicity at any levels in either rats or dogs. Based on the results of the long-term studies, the “no-effect” level was determined for rats and dogs to be 100 ppm.

Genetic aspects of the transition from traditional to modern fish farming

A theoretical model describing the genetic aspect of the transition from traditional to modern animal husbandry is presented. Traditional races are characterized by high tolerance to harsh environments but a low rate of response to increased management inputs. Modern, artificially-selected breeds are efficient convertors of management inputs to higher production but have a low resistance to harsh environments. Thus, under lowinput traditional husbandry, the traditional races are best adapted, while under modern, high-input husbandry, modern breeds are most productive, and in the intermediate zone, hybrids between the two races are capable of closing the 'profit gap' in the shift from traditional to modern husbandry. The domesticated European, and the Chinese Big-belly races of the common carp were tested under many environmental 'treatments' involving variation in density, polyculture, aeration, feeding and fertilization. The Big-belly showed, as expected, high resistance to the poor 'treatments' but low response to environmental improvement. The European breeds performed best in the higher half of the environmental range and their response rates were highest. The F1 hybrids between the two races excelled in the lower third of the range, exhibiting, there, a high heterosis but only an intermediate rate of response. It was concluded that successful changes from one aquaculture system to another, and particularly the change from traditional to modern husbandry, require a simultaneous search for the most efficient genotype × environment combination and, for each level of modernization of traditional fish farming, the most effective genotype must be identified and utilized. The transition from traditional to modern animal husbandry, including fish farming, is best quantified by the levels of invested inputs, other than labour, that induce higher production of the individual animals. The major management inputs of modern fresh water fish farming are expensive feeding, veterinary care, control of predators, organic and chemical fertilizers that enrich the production of natural fish food, water circulation and aeration. Since all these inputs are rather expensive, the fish have to pay for them by increased production, i.e., faster growth rate. Thus, the sina qua non of such a transition is the availability of animal stocks capable of converting increased inputs into economically attractive increased yields. We are all aware of the very great physiological plasticity of farm animals. In the case of the European carp, for example, the same genetic stocks, raised under high stocking density and low feeding level may gain an average weight of 10 to 20 g per fish in a whole year, while under low density and abundant feeding, they may gain over 2 kg in the same period. Such physiological responsiveness may give the wrong impression that all that is needed for the transition to more modern husbandry are improved environmental circumstances. The object of this paper is to point out that the proper choice and changeover of genotypes is equally important for the succesfull implementation of the usually gradual process of fish farming modernization. This demonstration will be based on results of experiments with the European and Chinese races of the common carp, and their F1 hybrids.

Milk production from diets of silage and dried forage. 2. Effect of ensiling ryegrass cut at two levels of digestibility and given ad libitum with supplements of dried grass pellets

SUMMARY1. Young adult and adult British Friesian female cattle (heifers and cows) which were lactating were individually fed ad libitum on ryegrass silage of high (HS) or low (LS) digestibility with one of two levels of a supplement of pellets of dried grass (H or L) in a 2 × 2 factorial experiment with three heifer and seven cow replicates.2. The percentages of digestible organic matters in the dry matter (DM) in vitro were respectively 64·4, 57·5 and 69·0 for forages HS, LS and and the dried grass. The HS crop, however, was significantly lower in DM content, and after ensiling with formic acid additive had a higher lactic and total acid content than the LS crop.3. The dry-matter intake of the less acid silage LS was greater than that of HS (P<0·05) although the dry-matter digestibility of the LS diets was on average 6 units lower than the HS diets. The intakes of digestible dry matter (DDM) and digestible organic matter were greater (P<0·05) in mid lactation when HS was fed. DM and DDM intakes were significantly increased by the higher level of feeding of the dried grass supplement.4. The yield, composition and energy content of milk did not differ between silages but the yield and protein content of the milk increased significantly at the higher level of supplement feeding. The milk yields were respectively 19·35, 17·54, 19·49 and 17·97 ± 0·505 kg/head per day for treatments HSH, HSL, LSH and LSL on these all-grass diets over lactation weeks 4 to 20. Live-weight loss was greater (P<0·01) on the LS diets. Blood composition was normal and did not differ markedly between treatments.

Effects of dietary protein and energy on the growth of Friesian hull calves

Abstract Results are reported from an experiment examining the effects on the growth of the pre-ruminant calf of diets containing a range of protein: energy ratios fed at two rates. Groups of three Friesian bull calves were allocated to each of six milk-based rations containing either 15.7, 18.1, 21.8, 25.4, 29.6, or 31.5% protein on a dry matter basis and fed adequate energy for growth rates of 830 gjday. The same diets, except the 29.6% protein ratio, were also fed to five groups of three calves receiving energy intakes sufficient for growth rates of 610 g/day, The comparative slaughter procedure was used to assess treatment effects after a 49-day trial period. Both protein and feeding levels markedly affected the gains of body weight, protein, and fat, but energy gains were affected by dietary protein content only at the low feeding level. Estimated digestible protein requirements for maximum body weight gains were 166 ± 13 gjday and 236 ± 19 gjday at the low and high feeding levels respectively and we...

Effects of hexachlorophene in the rat and their reversibility

Treatment of albino rats once daily for 6 weeks with graded doses of hexachlorophene led to pathologic changes in the white tracts of the central nervous system. These changes were dose related with respect to both incidence and severity and consisted of focal vacuolization (status spongiosus) which was most severe in the cerebellum, less severe in the spinal cord, and least severe in the cerebrum. The effect was graded as severe for cerebellar tissue at dose levels of 40 mg/kg and higher, and a lower incidence of less severe changes was observed at 20 mg/kg. Dietary administration of hexachlorophene for 90 days at levels up to 200 ppm led to a moderate degree of vacuolization in only 2 of 20 rats at the highest level and no signs of central nervous system disorders were observed. Hexachlorophene blood concentrations were dose related but did not increase with duration of exposure beyond 30 days. These concentrations ranged from 1.5 to 3 μg/ml at the highest feeding level. Sequential sacrifice of rats following daily treatment for 42 days with 40 mg/kg by gavage produced evidence that the effects are reversible. Gross effects disappeared within 1 week, and histopathologic changes gradually and regularly diminished from severe changes for animals sacrificed 6 hr after the last dose to barely detectable changes after a recovery period of 84 days. No effect was detectable after 168 days. Examination of tissues stained with solochrome cyanine yielded no evidence of demyelination, and electron micrographs suggest that the changes consist of edema together with axonal swelling in instances of severe effects.

Influence of the oral contraceptive, menstranol, on drug-metabolizing enzymes of female rats in thiamin-supplemented and deficiency states.

The administration of a diet deficient in thiamin results in elevated hepatic microsomal activity of aniline hydroxylase, ethylmorphone demethylase, NADPH cytochrome c reductase and cytochrome P-450 when compared to similar female rats fed diets supplemented with thiamin. Accompanying these differences in enzyme activity are increased concentrations of microsomal docosahexaenoic acid and arachidonic acid. Binding of aniline to microsomes from rats fed high levels of thiamin is decreased due to a decrease in cytochrome P-450. On the other hand, the binding of ethylmorphine to P-450 is decreased by feeding high levels of thiamin. The daily administration of mestranol enhanced ethylmorphine and aniline metabolism to a greater extent in rats fed thiamin-rich diet than in rats fed thiamin-deficient diet or laboratory chow. This treatment did not increase cytochrome P-450 cytochrome c reductase or microsomal protein nor does it appear to affect the binding of aniline to cytochrome P-450. Ethylmorphine binding is generally decreased by this treatment. Alterations in the Michaelis constants for these reactions were limited to an increase in the Ks for aniline in pair-fed animals and in the Ks for ethylmorphine in thiamin-deficient rats receiving 1.0 mg mestranol per day.

The interaction of nutrition and body condition at mating on ovulation rate and early embryo mortality in Scottish Blackface ewes

SUMMARYOne hundred and fifty-six Scottish Blackface ewes were differentially group-fed over a 2-month period to achieve three distinct levels of body condition (good, moderate and very poor). Over 5 weeks prior to mating, one group of good-condition ewes was maintained in that condition, one group of good- and one of moderate-condition ewes were brought down in condition by restricted feeding and one group of moderate and the very poor condition ewes were raised in condition by a high level of feeding. Ewes were therefore in good, moderately good or poor condition at mating. After mating, ewes were killed either on return to service or at 25 ± 5 days for counts of corpora lutea and viable embryos.Poor body condition, irrespective of feeding level, was associated with a delay or suppression of oestrus and with a high return-to-service rate. Ovulation rate was positively related to body condition at mating but not to the level of pre-mating food intake at the condition levels studied.Embryo mortality decreased as body condition at mating increased and the interaction between condition and the level of pre-mating food intake had a differential effect on mortality of single- and multiple-shed ova. The lowest rate of embryo mortality was found in ewes in moderately good condition which had been well-fed before mating.

The effect of feeding high levels of low-quality proteins to growing chickens.

1. Three growth trials were done using male broiler chicks. In the first two trials, groundnut meal was used, with and without supplementary methionine and lysine. In the third trial, soya-bean meal was used with and without supplementary methionine. Protein levels ranged in the first trial from 120 to 420 g/kg diet and in the third trial from 120 to 300 g/kg diet. Thus the assumed minimal amino acid requirements of the chick were supplied by high levels of low-quality dietary protein. 2. Diets based on cereals and groundnut meal did not support maximum live-weight gain or maximum efficiency of food utilization at any level of dietary protein. When the principal deficiencies of lysine and methionine were corrected, this protein mixture was capable of supporting the same growth rate as a control diet of cereals and herring meal. 3. Diets based on maize and soya-bean meal did not support quite the same growth rate as similar diets supplemented with methionine, even though the protein level in the unsupplemented diets was sufficient to meet the assumed methionine requirements. 4. These results are interpreted as examples of amino acid imbalance in diets composed of familiar feeding-stuffs. It is concluded that one cannot assume that the poor quality of a protein source can always be offset by increasing the concentration of dietary protein.

The rate of heat loss during fasting in the growing pig.

1. The heat loss for individual growing pigs, whose initial body-weight was 25-40 kg, was measured continuously for periods of 14 or 21 d when they were maintained at an environmental temperature of either 20 or 30 degrees. For each temperature the feeding level before and after a period of fasting was held at either 39 or 45g/kg body-weight per d. Four pigs were given each treatment; food was withheld from three animals for a 4 d period in each experiment, and the fourth pig (control) was fed for the whole experimental period. 2. After the withdrawal of food, the heat loss decreased rapidly and minimum values were recorded during the third and fourth days of fasting. Fasting heat loss was higher at 20 degrees than at 30 degrees and was not significantly dependent on the preceeding level of feeding. The mean values obtained at 20 and 30 degrees were 457 and 380 KJ/kg 0.75 per d respectively. 3. The heat loss during the periods of feeding was significantly higher (P less than 0.05) at 30 degrees than at 20 degrees, and was also higher at the higher level of feeding. 4. The apparent efficiency of utilization of metabolizable energy for maintenance was calculated as 0.80. 5. It was concluded that the critical temperature for a fasting pig weighing 25-40 kg is approximately 25 degrees.

Ammonia, pH and Volatile Fatty Acids in the Bovine Rumen after Feeding with Hay

The effect of feeding level and interval between feedings on the fermentation pattern in the bovine rumen have been investigated in experiments with hay. The animals were completely adapted heifers fitted with rumen cannulas, and the parameters measured were ammonia, pH, volatile fatty acids (VFA) and non-glucogenic/glucogenic ratio (NGGR) in the VFA mixture. Increasing feeding levels, ranging from 2/3 to 4/3 of maintenance level, resulted in higher average concentrations of VFA and lower pH in the rumen fluid. Further the highest level of intake caused a considerable diurnal variation in the pH and the concentration of total VFA, and increased the variation in the molar composition of the VFA mixture. Three feeding intervals ranging from 8 to 16 hrs., with hay administered at maintenance level, caused no changes in the fermentation pattern. Typical variations in the concentrations of ammonia and valeric acid as related to time after feeding were demonstrated, but the concentrations of the branched-chain fatty acids in the rumen fluid were found to be quite constant. It may be concluded that a representative mean value of the parameters measured, except for ammonia and valeric acid, may be based on relatively few samples when feed intake does not exceed maintenance level, whereas sampling every hour is required at higher feeding levels.

Wood Cellulose as an Energy Source in Lamb Fattening Rations

Two finishing studies were conducted to determine the value of wood cellulose as an energy source in lamb fattening rations and to evaluate the effect of feeding high levels of cellulose fiber on performance and carcass traits of finishing lambs. In Trial I, a 60% alfalfa — 40% concentrate ration was compared with two rations containing 66% fiber obtained by two different processes. No differences in average daily gains were observed among treatments, however, there was a reduction of daily feed intake by the lambs receiving the fiber rations as compared to the control group (1.33 kg/day and 1.78 kg/day, respectively). The reduced feed intake and lower body fat content resulted in a higher efficiency of utilization of the fiber rations. Control lambs exhibited higher dressing percentages and backfat thickness than the fiber-fed lambs. There were no differences in loin-eye area, kidney fat percent, conformation score or carcass grade among treatments. Calculated cutability grades were higher for the fiber treatments than for the control group. In Trial II, a 70% barley ration was compared to three rations containing sulfite fiber and different nitrogen sources. The lambs receiving the control ration had higher average daily gains than those fed the fiber rations. Daily feed intakes were similar to those in Trial I. Feed efficiency was highest for the fiber-SBM ration and lowest for the fiber-roughage ration. The control and fiber-CSM groups had similar efficiencies of feed utilization. The control lambs had higher dressing percentages, greater backfat thickness, larger loin-eye area, more kidney and pelvic fat, lower carcass grades and lower yield grades than the fiber-fed lambs. There were no differences in the carcass traits evaluated among the three fiber treatments.

THE USE OF PROPIONIC ACID AS AN ADDITIVE FOR MAIZE SILAGE

ABSTRACTTwo clamps of maize silage were prepared in mid‐October, one with 0·33% propionic acid applied during harvesting and one without additive. The treated silage had a peak temperature 3°C below that of the untreated silage. The estimated loss of DM during ensiling was 8% greater in the untreated silage. The stability and acceptability of the silages were tested after exposure to air. The treated silage was slightly more stable than the untreated milage and the intakes by heifers were sligbtly greater. The digestibilities of the two silages estimated in wether sheep were similar, averaging 68·6% digestible OM in the DM at maintenance level and 63·5% at a high level of feeding. The intakes and growth rates of calves and beifers oifered the two silages were also similar.

Experiments on the nutrition of the dairy heifer:IX. Food utilization in lactation

SUMMARYFood utilization by lactating dairy cows was studied in a randomized experiment covering the first 24 weeks of lactation, with further observations on performance over the remainder of the lactation under farm conditions. Over a 3-year period 90 firstcalf cows each took part in the experiment for one lactation, making six groups of 14–16 animals.For the experimental period a fixed basal diet was given of hay, concentrates, and wet brewer's grains. One group received only the basal ration. Four groups received in addition a fixed concentrates supplement for 4, 8, 12, 16 weeks from calving onwards respectively. The sixth group also had supplementary concentrates for 16 weeks but for weeks 5–12 inclusive the amount was doubled so that this group's diet simulated broadly ad libitum feeding in early lactation.Milk yield was increased by extra concentrates. The greater part of the effect was apparent in the first 2 weeks of different levels of intake, with a further build-up over the next 6–8 weeks. The size of the response fell as time from calving to initiation of different intakes increased. Additional food increased and delayed peak yield level. Persistency of milk yield was not affected by fixed differences in intake. Rate of liveweight change was improved by extra concentrates, less so in the third compared with the first month on treatment.A higher level of feeding in early lactation led to a greater partition of nutrients in mid-lactation to milk at the expense of gains in body reserves. This advantage to milk production extended to the end of lactation. In it the greatest response per unit concentrates was obtained from supplementation in the first 4 weeks of lactation but the total effect was increased by giving a double allowance of concentrates, and by extending the period of extra feeding to 8 weeks after calving.Solids-not-fat content and yield, and fat yield but not fat content, showed a similar response pattern to milk yield.Animal-to-animal variation in output on constant diets was characterized by negative regressions of live-weight change on milk yield. The regression coefficients were greater in early than in mid-lactation but they were constant in size at any one time for the various groups. A change in ration induced a change in output of the individual in which that production pathway favoured naturally by the animal was the more affected.

Short-term toxicity of isoamyl salicylate in rats

Isoamyl salicylate was given to groups of 15 male and 15 female rats at dietary concentrations of 0 (control), 50, 500 or 5000 ppm for 13 wk. There was a decrease in weight gain at the highest dietary level accompanied by a reduced food intake, but a paired-feeding study showed that this was due to the diet's unpalatability. The females given the highest dietary level drank more water than the controls and produced slightly greater volumes of more dilute urine. The relative kidney weight was increased in rats on the 500 and 5000 ppm levels without any histopathological changes. It is concluded that isoamyl salicylate was exerting a mildly nephrotoxic effect. The relative liver weight was increased at the highest level of feeding but there were no other effects attributable to treatment. The no-untoward-effect level from this study was 50 ppm of the diet, providing a mean intake of approximately 4·7 mg/kg/day.