Strains Of Hens Research Articles

Changes in pituitary somatotrophs and lactotrophs associated with ovarian regression in the turkey hen ( Meleagris gallopavo)

Hyperprolactinemia has been associated with incubation behavior and ovarian regression in turkey hens. Preliminary data show that tamoxifen, a partial estradiol receptor antagonist, may effect ovarian regression. The objectives of the study were to induce ovarian regression in egg-laying turkey hens by administration of tamoxifen, to determine whether incubation behavior would be effected by tamoxifen treatment and to examine the distribution of lactotrophs and somatotrophs and their immunocytochemical changes in the adenohypophysis due to a change in reproductive state. Two commercial strains of turkey hens were administered tamoxifen (experimentals) or vehicle (controls) intramuscularly (40 mg/hen/d). Equal numbers of experimental and control hens were killed for sample collection after 5, 9 and 14 days ( n = 4 per strain) of treatment. Blood samples were collected for hormone assay and pituitaries prepared for immunocytochemistry. Tamoxifen treatment for 9 and 14 days induced ovarian regression but not incubation behavior. Plasma luteinizing hormone levels were significantly increased after 5 and 9 days of tamoxifen administration, whereas prolactin and growth hormone levels were unchanged. Somatotrophs were found predominantly in the caudal portion and lactotrophs occurred in the cephalic lobe of the pituitary. Relative to controls, the prolactin immunoreactive area was significantly greater in tamoxifen-treated hens, whereas the growth hormone immunoreactive area was reduced.

In vitro Studies of Campylobacter jejuni/coli Strains from Hens and Humans regarding Adherence, Invasiveness, and Toxigenicity

Campylobacter jejuni/coli strains from hens and humans were compared for their ability to adhere to and invade HEp-2-cells and for toxigenicity to CHO-cells. In both hen and human strains, invasiveness was higher among non-toxigenic strains than among toxigenic ones. The frequency of adherence, invasiveness, and toxigenicity was the same in hen and human strains.

Identification of Salmonella enteritidis from Experimentally Infected Hens Using a Colorimetric DNA Hybridization Method

Identification of Salmonella enteritidis from cloacally challenged commercial laying hens was studied by comparing bacterial isolations using conventional methods with detection by the use of the GENE-TRAK colorimetric DNA probe assay. More positive test results were obtained using the latter on days 14, 28, and 42 postchallenge, but the difference between the two methods was not statistically significant. Over the duration of the experiment, positive cloacal samples were statistically more frequent from a commercial strain of white leghorn hens when compared with a commercial brown egg-producing strain (28/60 vs. 9/57; chi-square 1 df = 12.9, P < 0.001). Eggs having various shell defects were produced by the infected hens only after Salmonella challenge. These defects included, in order of frequency, elongated shape, thin shells, off-white color (tints), small size, wrinkles, and pimples. No Salmonella could be recovered from 193 defective eggs, nor were positive isolates made from additional tests performed on 50 normal eggs. Proteus sp. was isolated from 10 eggs, however. Our observations demonstrate that the GENE-TRAK colorimetric method is comparable with conventional bacteriology for the identification of Salmonella in cloacal samples taken from laying hens. Moreover, the two methods demonstrate the existence of breed differences in susceptibility to S. enteritidis challenge.

Dietary .alpha.-Linolenic Acid and Laying Hen Strain: Fatty Acids of Liver, Adipose Tissue, White Meat, Dark Meat, and Egg Yolk

The effect of dietary 18 :3n-3 on fatty acids and total lipids of liver, adipose tissue (subdermal fat), egg yolk, and dark and white meat was studied in six strains (White Leghorn, Brown Leghorn, Light Sussex, New Hampshire, Barred Rock, and Rhode Island Red) of laying hens. Dietary 18 : 3n-3 resulted in an increase (P < 0.001) in n-3 fatty acid content of all tissues. Among the tissues, the adipose tissue incorporated the highest level of 18 :3n-3. The increase in tissue n-3 fatty acids resulted in a concomitant reduction (P < 0.05) in 18 :1 and 20 :4n-6. Among strains, light Sussex incorporated the lowest (P < 0.05) concentration of 18 :3n-3 in the hepatic tissue. A significant strain effect (P < 0.05) was observed in the total lipids of egg yolk, adipose tissue, and dark and white meat. The high 18 :3n-3 diet resulted in a reduction (P < 0.05) in the total lipid content of the liver tissue in all strains.

Effects of Dietary α-Linolenic Acid and Strain of Hen on the Fatty Acid Composition, Storage Stability, and Flavor Characteristics of Chicken Eggs

A study was conducted to determine the effect of dietary α-linolenic acid on the fatty acid compositions of egg yolk lipids, to copherols, and internal quality of raw eggs during storage and the sensory characteristics of hard-boiled eggs from six different laying hen strains. Laying hens (total 300 birds, 72 wk old) from six strains (Rhode Island Red, Barred Plymouth Rock, New Hampshire, Light Sussex, Brown Leghorn, and White Leghorn) were distributed in 12 floor pens (2 pens per strain, 25 birds per pen) with male roosters. One of the pens for each strain was fed with tallow-based control diet and another was assigned with 3% α -linolenic acid (LNA) enriched diet with 120 U of mixed to copherol/kg diet for 3 mo. Ten eggs from each pen were collected every day after 2 wk with the experimental diets, and stored in a cold room at 4 C up to 4 wk. Total lipids, fatty acid compositions, Haugh units, and tocopherols of egg yolk were determined once a week during the 4-wk storage periods. Sensory studies were also conducted using the eggs stored for 2 wk at 4 C.Dietary LNA increased the amount of n-3 fatty acids (6.5%) in total lipid, and over 70% was C18:3n3, and the rest was C22:6n3 (20 to 25%) and C22:5n3 (5 to 10%). Only minor differences in fatty acids among strains were observed. The differences and the changes in tocopherols during storage periods by strain and diet appeared randomly and lacked consistency. The amount of tocopherols in yolk and the internal quality of raw eggs were not changed during storage periods. The flavor scores of eggs from control diet were more favorable than those of eggs from LNA diet, but their differences were minor. This result indicates that laying hen strains is not an important consideration in the dietary modification of fatty acid of shell eggs.

Turkey Breeder Hen Performance by Strain During Consecutive Lay Periods

The results of this study provide information about reproductive performance among commercially available strains of Large White Turkey breeder hens, Nicholas (N), British United (B), and Hybrid (H). The hens were managed identically through two consecutive lay periods, summer-fall (1st-yr) followed by winter-spring (recycled). Effects of the intensity (351 vs 24 lx) of supplemental light were evaluated during the 1st-yr lay period. Data were collected for onset of oviposition, egg production, BW, feed consumption, livability, egg weight, and egg components.Light intensity had similar effects on all variables measured. There were neither strain differences nor genetic interactions with light intensity treatment. There was no difference in livability among strains (P = .20) or between year of lay (P = .08), and there was no strain by year interaction. Body weight differed by strains and year and there was a significant strain by year interaction. In general, N were heavier than H or B in the 1st-yr and early recycle lay period, whereas H and B were similar in BW in both lay periods. Recycled hens of all strains were heavier than 1st-yr hens. The onset of lay was earlier in H than B or N in both lay periods and all three strains had a delay in onset of lay after recycling. Through 23 wk photostimulation the B hens produced more eggs per hen than N or H hens (B > N > H) and recycled hens produced more eggs per hen than 1st-yr hens. Strain, year, and strain by year interaction effects were significant for egg weight. The first eggs laid, as well as subsequent eggs in both lay periods, were heaviest in N hens. In all strains, percentage yolk increased and albumen decreased with time in lay. However, N hens had a smaller percentage yolk and greater albumen than H or B hens. The mean percentage shell was greatest in H hens.

Incidence of Prelay Squatting Behavior is not Related to Subsequent Egg Laying in Turkey Breeder Hens

Sexual receptivity of turkey hens as indicated by squatting (sexual crouch) was evaluated in three strains of breeder hens, Nicholas (N), Hybrid (H), and British United (B). The incidence of squatting was compared among strains through 84 d of photostimulation and related to egg production characteristics. Significant strain, time, and strain by time interaction effects occurred for the incidence of squatting. In all three strains, squatting started within the 1st wk of photostimulation, rapidly peaked (75.0, 65.6, and 43.0% for H, B, and N hens, respectively) at 14 d of photostimulation, then returned to lower, basal levels at or before attainment of 50% hen-day egg production. Squatting incidence was highly variable within and between strains but was generally lower in N hens than H and B hens, which showed similar squatting expression. The incidence of prelay squatting was not correlated to onset or rate of egg production. However, there was a negative correlation between squatting behavior and percentage floor eggs in H (P = .03) hens. It was concluded that squatting incidence varies within and between strains of hens and is not related to subsequent egg laying performance.

Dietary modification and hen strain dependence of egg yolk lipids

The effects of diet and strain on the chemical, cholesterol and fatty acid composition of egg yolk lipids were studied. Two hen strains (Single Comb White Leghorn and Brown Leghorn) and four experimental diets with different fatty acid composition were used. No significant differences ( P > 0.05) in the yolk chemical composition nor cholesterol concentration in the egg were observed. However, significant differences ( P ≤ 0.05) in the fatty acid composition of yolk lipids were observed. The C-18:1 and C-18:2 concentration in yolk was significantly affected by diet ( P ≤ 0.05) but no differences were observed for saturated fatty acids. Only the minor C-16:1, C-18:0 and C-20:4 fatty acids were influenced by hen strain. It was concluded that amount of unsaturated fatty acids in the egg yolk could be altered by dietary manipulation. This could be important in human nutrition.

Evaluation of Resistance of Four Strains of Commercial Laying Hens to Experimental Infection with Salmonella enteritidis Phage Type Eight

Four different strains of White Leghorn hens were orally infected with 1 × 108 cfu of Salmonella enteritidis phage Type 8 per bird. The birds were monitored for 10 wk postinfection for colonization of internal organs, fecal shedding of S. enteritidis, and the production of S. enteritidis- contaminated eggs. There was no difference among the four hen strains in regards to the probability of S. enteritidis isolation from liver and spleen, ovary, and cecal tissue within the first 30 d postinfection. However, during the first 14 d postinfection, S. enteritidis organisms were isolated in significantly higher rates from eggs and fecal samples of Strain A than from samples obtained from the other three hen strains. Results suggest that there may be inherent differences between strains of laying hens with regard to their response to infection with S. enteritidis.

Choosing a Commercial Laying Hen Strain Based on Multicriteria Decision Analysis

The amount of information contained in comparative performance reports for commercial strains of poultry can be overwhelming. The decision of which commercial strain of hen to choose involves production criteria which are measured in different units (e.g., percent, dollars, lbs per 100, etc.). Production values based on fuzzy set logic were used to overcome the problem of differing units. Fuzzy set logic is a recent mathematical idea for describing imprecise terms such as “desirability.” In terms of Management Science, a good decision is based on logic with consideration made of available data and possible alternatives. Although a good decision will occasionally yield unfavorable results, in the long run logical decision analysis will result in successful outcomes. Four decision methods, using fuzzy set memberships, were demonstrated for choosing a commercial strain of laying hen. The decisions were based on maximin, equally likely averaging, weighted averaging and ordered weighted averaging. In three of the four decision methods, the same strain of hen proved to be the choice.

The Importance of Timely Removal from the Incubator of Hatched Poults from Three Commercial Strains

Egg size and functional qualities differ among strains of commercial turkeys. Thus, energy budgets of egg contents and eggshell conductance constants may represent different strategies for hatching and more energy may be expended by some strains than others. The objective of the present study was to determine the effects on poult quality of holding hatchling poults in the incubator for 12 or 24 h posthatching. Eggs from three strains of commercial turkey breeder hens were obtained from a commercial turkey breeding company, numbered, randomly distributed, and set in incubators. The time of hatching of each egg was observed at 4-h intervals and a random sample of hatchlings emerging from the shell at 648 and 660 h of incubation was compared with poults kept in the incubator until 672 h of incubation. Holding poults in incubators 12 or 24 h posthatching reduced (P ≤ .05) total body weight of all strains examined but increased (P ≤ .05) relative heart and liver weights. Holding time interacted (P ≤ .05) with strain of turkey to increase blood plasma glucose and decrease heart glycogen. Holding decreased (P ≤ .001) liver glycogen precipitously in all three strains. It was concluded that holding poults in incubators 12 or 24 h posthatching has detrimental effects on carbohydrate metabolism and some strains of turkeys respond to the holding time better than others. Therefore, poult quality of commercial turkey strains may be affected differently by keeping them in the incubator posthatching.

A Feather-Sexed Strain of Laying Hens Was More Responsive to Dietary Supplements of Choline and Methionine than a Vent-Sexed Strain

A response surface design was used to study Cho and Met interactions with corn and soybean diets, using two strains of hens. The strains were a feather-sexed line (FS strain), and a vent-sexed line (SS strain). The diets contained 3% meat and bone meal and, on chemical analysis, 15.1% crude protein, .29% Met, .225% Cys, and 1,041 ppm of Cho. Nine diets were fed from 20 to 68 wk of age, using added Met levels ranging from 0 to 500 ppm and added Cho levels ranging from 0 to 1,500 ppm, to fix the design points. The FS strain consumed significantly more feed per day (117 versus 108 g) than the SS strain, but there were no significant differences for the 24 to 68 wk period in egg production, egg weight, or feed per dozen eggs. Three and five combinations of Met and Cho were significant in improving egg production (P < .05) out of the eight combinations for the SS and FS strains, respectively.The best egg production for the FS strain for the period 24 to 68 wk was observed at 250 ppm Met and 1,500 ppm Cho, or 427 ppm Met and 220 ppm added Cho. The SS strain showed no significant (P > .05) dietary responses in egg production between 250 ppm Met and no Cho, or 427 ppm Met and either 220 or 1,280 ppm Cho. The SS strain showed no significant (P > .05) dietary response in egg weight to either Cho or Met. The combination of 427 and 220 ppm of Met and Cho, respectively, with the FS strain resulted in the largest egg weight. However, this was only significantly different (P < .05) from addition of a combination of 73 ppm of Met and 220 ppm Cho. These results indicate strain differences in responses of laying hens to Met and Cho supplementation, and also support the concept that Met and Cho can spare the requirements of each other.

The Effect of Dietary Iodine on the Hatchability of Eggs from Two Commercial Strains of Turkeys

Supplemental dietary iodine (3.5 mg/kg) was fed to two commercial strains [British United Turkeys (B) and Nicholas (N)] of turkey breeder hens. The basal diet contained .7 mg/kg of iodine. Observations were made on hen body weights, feed consumption, hatchability, egg weights, and egg functional characteristics to test the hypothesis that there are differences between commercial strains of turkey breeder hens in the dietary iodine requirement for reproductive success. Supplemental iodine decreased (P≤.05) functional egg characteristics of both strains. Egg production and hatchability were influenced by an interaction between strains and dietary iodine (P≤.05). In Strain B hens, egg production and hatchability declined (P≤.05) when hens were fed supplemental iodine but in Strain N hens no effects on hatchability were observed and egg production increased (P<.05) with iodine supplementation. The decline in hatchability of eggs from Strain B hens was due to significant (P≤.05) increases in embryonic mortality during the 1st wk of incubation and during pipping. The treatments resulting in depressed hatchability caused embryos to rely more (P≤.05) on glycogenolysis than gluconeogenesis during pipping and hatching. The Strain B embryos utilized gluconeogenesis more during pipping (P≤.05) than Strain N embryos and embryos from Strain B iodine-fed hens had a lower rate of gluconeogenesis than those from hens not fed iodine. It is concluded that there are differences among strains of turkey breeder hens in their dietary iodine requirement for optimal hatchability.

Response of Two Strains of Turkey Hens to Various Protein and Energy Feeding Programs

Two experiments were conducted to note the response of Nicholas and British United Turkey (BUT) strains of turkey hens to so-called North American and European feeding programs. The European program involved increased quantities of protein and essential amino acids relative to energy level of the diet. In Experiment 1, the two feeding programs were each tested with four replicate groups of 40 commercial hens of both strains. Each feed was allocated by weight and allotment continually adjusted for mortality. At 105 days of age, eight hens per replicate pen were sampled for various carcass characteristics. Nicholas hens were most often heavier (P<.01) to 56 days, although after this time the BUT strain showed increased growth. At 105 days, BUT hens fed the high-protein diet were the heaviest group, being significantly (P<.05) heavier than comparable birds fed low-protein diets. There was no difference (P<.05) in feed efficiency from 0 to 105 days or in any of the carcass traits measured.In Experiment 2, the two strains of hens were grown to broiler weight at 70 days, again with conventional versus high-protein diets. Each treatment was tested with six replicate floor pens each containing 50 poults. At 70 days of age both strains of hen were heavier when fed the high-protein diets (P<.05), although the Nicholas hens were heavier than the BUT birds (P<.05). The BUT hens ate less feed than Nicholas birds (P<.01) and also exhibited superior feed efficiency (P<.01). The mortality rate of BUT hens was greater than that of Nicholas hens when the high-protein diet was used (P<.05).There were obvious differences in growth rate of the two strains of turkey hen used in the present trials. Depending upon market age, the BUT hen seemed to respond favorably to diets of higher protein-amino acid content relative to energy concentration.

Failure of Two Feed Additives (Shell-Developer and Ethacal) to Improve Eggshell Quality ,

Two feed additives were tested for their ability to improve eggshell quality. One was Shell-Developer, containing approximately 60% NaHCO3, and the other was Ethacal, a sodium aluminosilicate. Both feed additives were fed to three commercial strains of hens. The first trial began in early summer and lasted 28 days, the hens having been in production for 56 wk at the start of the trial. Ethacal was fed at a rate of .75% of the diet. Shell-Developer was fed at a rate of 1.25% of the diet for 7 days, .625% for the next 7 days, and .3125% for the last 14 days. The second trial ran for 56 days in autumn, utilizing the same hens after a forced rest and approximately 2 mo of production.The addition of Shell-Developer had no positive effects at any time on any of the characteristics measured. Ethacal had a negative effect on the rate of egg production and egg weight during the last 28 days of Trial 2. Ethacal also decreased feed consumption in three of the five data collection periods tested. In Trial 2 Ethacal significantly improved egg specific gravity and also improved the percentage of eggs with a specific gravity of at least 1.08. The negative effect of Ethacal on egg production and egg weight is postulated to be due to its negative effect on phosphorus nutrition.

A microassay method for neurotoxic esterase determinations

A microtiter plate reader with an associated computer to average triplicate samples and subtract blanks was used for reading and calculating neurotoxic esterase (NTE, also known as neuropathy target esterase) activities in spinal cord regions of hens 4 hr after administration of diisopropylphosphorofluoridate (DFP, 0.5 mg/kg sc). Although NTE inhibition is an early indicator of organophosphorus ester-induced delayed neuropathy, DFP-induced inhibition was not greater in regions of the spinal cord where pathological changes are most notable. Acetylcholinesterase (AChE) activities and protein determinations were also done on these tissues using microassay methods. DFP-induced AChE inhibition was similar to NTE inhibition. In addition to the capability to be used for small regional esterase activity measurements, the microassay was advantageous because the number of samples incorporated into a single assay was increased and the time needed for the NTE assay was reduced by 50%. Total volume of incubate in each well was 0.3 ml; the incubate contained 1 20 quantities of sample and reagents necessary in more conventional assays. Validation of the microassay was performed by comparison with more conventional assays when measuring inhibition of NTE and AChE in brains of control and experimental hens of two different genetic strains (B13B13 and B21B21 white leghorns). Experimental birds were given DFP, 0.5 mg/kg sc, 24 hr before samples were collected. NTE activities in brains of control hens were similar using both types of NTE analytical procedures. Percentage inhibition of NTE caused by DFP was within 4% using both assay procedures in both strains of hens. The microassay was sensitive enough to detect NTE activity in 42 μg of hen brain after 15 min of incubation. Hen lymphocytes could also be examined for effects of organophosphorus esters on NTE activity, with 14.1 ± 2.2 and 8.3 ± 2.2 μmol/15 min/mg protein in 1 × 10 6 cells measured in samples taken before and 4 hr after administration of 0.5 mg/kg sc DFP.

The Effect of Pyruvate or Dihydroxyacetone on Parenterally Induced Liver Lipid Accumulation in the Rat

Orally fed pyruvate (pyr) and dihydroxyacetone (DHA) have been shown to decrease liver lipid accumulation in animal models. These compounds lessen the degree of fatty liver in ethanol-fed rats and in a genetic strain of hens predisposed to fatty liver. Total parenteral nutrition can result in liver dysfunction, including fatty infiltration of the liver. In this study, rats were assigned to either control, pyr, or DHA groups. All rats were fitted with jugular vein catheters, and following a 3-day recovery, were infused continuously for 7 days. The infusate provided adequate nutrition (including 7% kcal as fat) with 5% pyr or 5% DHA (g/liter) substituted for dextrose in the experimental groups. Plasma triglycerides were lower in the pyr groups relative to controls: 62.2 +/- 34.7 (SE) vs 96.8 +/- 44.3 mg/dl, though this was significant only at P less than 0.10. Neither pyr nor DHA decreased liver lipids. Pyr and DHA were administered intravenously in this study, and therefore passed through the heart and to peripheral tissues first. These compounds may need to be fed orally, passing via the portal system, to produce the liver lipid-lowering effects seen in other studies.

Stressor-induced alteration of lymphocyte proliferation in mice: Evidence for enhancement of mitogenic responsiveness

The present study evaluated the immunomodulatory effect of the administration of different intensities of electric foot shock presentations to different strains of mice. The results showed an enhancement of the mitogenic responsiveness to concanavalin A (Con A), a T-lymphocyte mitogen, that was directly related to the intensity of the electric shock presentations. However, the electric shock induced no significant alteration of the mitogenic responsiveness to lipopolysaccharide (LPS), a B-lymphocyte mitogen. These findings were evident in HLA-SW/ICR, 57BL 6N , and C3H HEJ mice. In contrast, the C3H HEN mice did not show any alteration of mitogenic responsiveness. The number of splenic leukocytes was not altered by the electric shock presentations in the strains that showed enhanced mitogenic responsiveness, but the C3H HEN strain showed a leukopenia directly related to the shock intensity. In a subsequent experiment, it was demonstrated that repeated sessions of electric shock resulted in a reduction in the enhancement effect. Collectively, the results demonstrate that stressful stimulation can result in an enhancement of mitogenic responsiveness, but that such an effect is dependent on the intensity and frequency of the stressor, as well as on the strain of the subject.

A Method for Estimating Shell Weight and Correcting Specific Gravity for Egg Weight in Eggshell Quality Studies

Two formulas were derived from definitions of egg density (ED) or egg specific gravity (ESG) or both. The formulas can be used for estimating ESG or shell weight (SW) when the other was not measured. The ESG formula can also be used to correct ESG for differences in egg weight (EW). This correction in ESG can be used when analyzing data from any experiment where differences exist in EW among treatments. In many reports from the literature, treatment differences for shell quality were found to be minimal when adjusted for EW.The formulas developed were used for estimating SW plus membrane and ESG for seven strains of hens fed six levels of calcium. These values were then correlated with measured values. The strains times calcium interaction was not significant. For measured SW versus calculated SW, the respective correlation coefficients were .979, .954, .974, .959, .965, .969, and .932 for the HyLine W36, DeKalb XL, Shaver, DeKalb DK, HyLine W77, Babcock Brown, and Hisex Brown Strains and were .923, .946, .973, .968, .963, and .954 for the respective calcium levels of 1.75, 2.0, 2.5, 3.0, 3.5, and 4.0%. The calculated ESG and measured ESG were highly correlated. These data indicate that ESG and EW can be used to obtain an excellent estimate for SW.

Effect of beta-naphthoflavone on o-tolyl saligenin phosphate-induced delayed neuropathy in two lines of chickens.

The effect of the microsomal enzyme inducer beta-naphthoflavone (beta NF) on the development of organophosphorus-induced delayed neuropathy (OPIDN) was examined in two laboratories (VPI and MSU), utilizing two strains of White Leghorn hens. A single intraperitoneal injection of beta NF at 80 mg/kg body weight 48 h prior to administration of o-tolyl saligenin phosphate (TSP), the neuroactive metabolite of tri-o-tolyl phosphate (TOTP), caused a significant increase in hepatic microsomal cytochrome P-450 concentrations and aniline hydroxylase activities after 72 h in both strains. Hepatic carboxylesterase and cholinesterase activities were not affected by beta NF treatment in either strain. Administration of TSP in single subcutaneous doses of 20 and 25 mg/kg body weight (VPI) or 30 and 60 mg/kg body weight (MSU) caused significant inhibition of whole-brain neuropathy target esterase (NTE) activity 24 h postdosing, and hens subsequently developed clinical signs characteristics of OPIDN. beta NF had no significant effect on NTE inhibition or on initiation or severity of OPIDN clinical signs. However, OPIDN clinical signs were less severe in the strain of bird (MSU) with the higher intrinsic hepatic carboxylesterase activity and the higher beta NF-induced cytochrome P-450 concentration. The study indicates that microsomal enzyme induction, which has been shown to alleviate TOTP-induced delayed neuropathy, could not alleviate OPIDN resulting from exposure to TSP. This study also suggests that strain may affect susceptibility to TSP-induced delayed neuropathy.