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Expression studies suggest that the incidence and severity of tibial dyschondroplasia (TD) in chickens, Gallus gallus, may be affected by the aggrecan gene, AGC 1. Here, results are described of a scan for single nucleotide polymorphisms (SNP) in AGC1 in genetic lines divergently selected for TD incidence in chickens. A total of 3,048 bp of DNA sequence obtained from amplicons produced by 4 primer-pairs designed from the GenBank AGC1 cDNA sequence were scanned for SNP. Among the 18 SNP detected and validated, only 2 were nonsynonymous. Allelic frequency differences between TD-affected and nonaffected birds were not statistically significant for all the SNP. The current results do not support an association of Gallus gallus AGC1 variation at the DNA level with the incidence of TD in chickens. The genomic resources described, however, including the SNP, could be useful in further evaluating AGC1 in other populations for association with TD or other skeletal abnormalities.

1. An experiment was conducted to determine the effect of selection for high (H) or low (L) incidence of tibial dyschondroplasia for 7 generations on processing performance of broilers. 2. Birds were obtained from diallel matings of the H and L lines (HH, HL, LH, and LL) and a randombred control (CC) line. Birds were reared to 7 weeks of age under standard management conditions. All birds were processed at 7 weeks of age. Body weight at 7 weeks, carcase weight, and carcase part weights were recorded on each bird. 3. An interaction between sire line and dam line was caused by lighter body and carcase weight at 7 weeks of age in HH birds than from the birds of the other crosses. 4. Birds by L line dams had heavier drumstick weights. The influences of sire line and dam line on weight of total breast muscle were not significant. Thigh weights and Pectoralis minor weights were lighter in HH line birds than those other matings. 5. Heterosis for body weight and for weights of carcases, drumstick and thigh was negative. Total breast muscle weight and P. major weight did not show significant heterosis. 6. It was concluded that selecting against TD does not reduce processing yield of broilers.

1. The effect of divergent selection for high (H) or low (L) incidence of tibial dyschondroplasia (TD) for 7 generations on blood calcium (Ca) and phosphorus (P) concentrations was studied. 2. The chicks used in this experiment were obtained from diallel crosses between H and L lines to obtain HH, HL, LH, and LL lines. A random-bred control (CC) line was also used. 3. The chicks were reared under standard management conditions. Body weight and plasma Ca and P concentrations were measured at 2, 4, and 7 weeks of age. Incidence of TD was recorded at 4 and 7 weeks. 4. Although HH birds had lower body weights than the other lines, there was no significant effect attributable to line selection for body weight at 2, 4, and 7 weeks of age. 5. The LL line birds had no incidence of TD at 4 weeks of age; however, the incidence of TD in LL line birds was 5.3% at 7 weeks of age. The incidence of TD was higher in HH line birds than the other line at 4 and 7 weeks of age. 6. Plasma Ca and P concentrations and Ca:P ratios increased with age. These results showed that HH line birds had higher plasma Ca, lower plasma P and higher Ca:P ratios than birds of the LL line.

Immunolocalization of transforming growth factor-beta1 (TGF-beta1) was determined in growth plates of two lines of broiler chickens with low and high incidences of tibial dyschondroplasia (TD). Ultrathin sections of growth plates from each line were treated with a polyclonal antibody specific for TGF-beta1, followed by colloidal gold-labeled protein A. Immunolocalization for TGF-beta1 was observed in chondrocytes of all zones of growth plates of low and high TD incidence lines. However, immunolocalization in extracellular matrix was restricted to the hypertrophic zones of both lines. In the hypertrophic zone of low TD incidence line, immunolocalization of TGF-beta1 in the extracellular matrix adjacent to collapsed cartilage canals (matrix streaks) was significantly greater than immunolocalization between patent cartilage canals. A similar increase was not observed in the high TD incidence line. Results indicate that chondrocytes of all zones of the growth plate contain TGF-beta1 but do not release it into extracellular matrix until hypertrophy has occurred. Greater concentrations of TGF-beta1 adjacent to collapsed cartilage canals may play a role in controlling angiogenesis and directing invasion of mineralized hypertrophic cartilage by metaphyseal blood vessels. A low concentration of TGF-beta1 in the extracellular matrix adjacent to collapsed cartilage canals of the high TD incidence line may be a factor in limiting vascular invasion of dyschondroplastic cartilage of TD lesions.

Continued genetic selection for improved BW gain has met an obstacle of skeletal disorders in broiler chickens. Two broiler chicken lines (HTD and LTD) were developed by 10 generations of divergent selection for tibial dyschondroplasia (TD) incidence originating from commercial primary breeders. The reference population was a randombred control line maintained along with the selected lines. Relationships of TD incidence with BW, egg production (EP), and hatchability were assessed using these lines. The response of TD to selection was asymmetric, favoring an increased TD incidence. Mean TD incidence increased 7.6 percentage points per generation during Generation 1 through 10 in males and 9.1 percentage points in females of the HTD line but did not change significantly in the LTD line at 4 wk of age. Responses of the HTD line in early (1 to 4) generations were greater than in later (6 to 10) generations, in contrast to nonsignificant responses for both durations in the LTD line. The 4-wk BW of the HTD line was slightly heavier than or similar to that of the LTD line within generations. The HTD line birds tended to decrease 7-wk BW with advancing generations. The trend of changes in BW was not as clear in the LTD lines as in the HTD line. The variability of 7-wk BW had an increased trend with advancing generations in the HTD line, accompanied by a decreased additive genetic variability of TD due to continued selection. The average EP in the LTD hens was 7.6 percentage points higher than in the HTD from Generations 1 through 10. Mean hatchability in the LTD line did not differ from that in the HTD line within generation. Responses of EP and hatchability, components associated with fitness, appeared slower towards increased fitness than towards decreased fitness.

Ability to utilize dietary phytate P was evaluated in 1,387 broiler chicks of 45 sire and 180 dam families, by feeding a corn-soybean base diet supplemented with no inorganic P and a low level of Ca. These chicks were the progeny of high and low incidence of tibial dyschondroplasia (TD) selected divergently for 11 generations and a nonselected control line. Chicks from the control line utilized phytate P better than those from the high or low lines in terms of livability, mortality, and growth performance. Chicks did not differ in mortality and body weight between the high and low lines. Variation in livability and mortality was greater among lines than among families, whereas families accounted for a greater part of variation than lines in body weight. Dams accounted for a slightly larger proportion of variation than sires in traits studied. Genetic selection for improved utilization of dietary phytate P could be effective.

Normal physeal and dyschondroplastic cartilage of broiler chickens was examined for six enzymes by isoelectric focusing in thin-layer polyacrylamide slab gels. Acid phosphatase (ACP), esterase (EST), malate dehydrogenase (MDH), and peroxidase (PRX) were present in the normal physeal cartilage but not in the dyschondroplastic cartilage. Staining intensity of glucose-6-phosphate isomerase (GPI) and triose-phosphate isomerase (TPI) was reduced in the dyschondroplastic cartilage compared with that of the physeal cartilage. Differences in the presence of these enzymes possibly demonstrated their roles in processes of bone formation, cartilage resorption, and calcification. ACP could be involved in calcification. Lack of EST and PRX may be related to the failure of vascular invasion in dyschondroplastic cartilage of afflicted birds. A deficiency of MDH and reduced GPI and TPI in dyschondroplastic cartilage may reflect a reduction in the activity of energetic metabolism, causing the dissipation of energy and necrotic cells.

Genetic variances and covariances were estimated by multiple-trait, derivative-free restricted maximum likelihood (DFREML) using an animal model for tibial dyschondroplasia (TD) expression and body weight at 4 and 7 wk of age. Data were collected from 7,483 broiler progeny obtained from 421 sires and 977 dams as part of a seven-generation selection experiment for high, and low TD expression, along with a randomly selected control line. Heritability estimates for TD expression and body weight at 7 wk were 0.42 and 0.50, respectively, larger than the corresponding estimates of 0.37 and 0.42 at 4 wk of age. Genetic correlations of TD expression or body weight at 4 wk with the same trait at 7 wk were greater than 0.80. Corresponding phenotypic correlations were 0.54 and 0.75 for TD incidence and body weight, respectively. Genetic correlations, however, of TD expression at either age with body weight at either age ranged from -0.01 to 0.10. Phenotypic correlations between the TD and body weight traits were of similar magnitude. TD expression and body weight at 4 and 7 wk of age, based on these data, are genetically and phenotypically independent traits.

Type X collagen is produced exclusively in hypertrophic chondrocytes of the growth plate of the proximal tibiotarsus and is believed to play an important role during normal development from chondrogenesis to osteogenesis. Chondrocytes of chickens with tibial dyschondroplasia (TD) fail to attain full hypertrophy and the amount of type X collagen, being a marker of hypertrophy, is likely to be reduced. It is not clear whether transcriptional regulation is functional for expression of the type X collagen gene in TD birds. Nucleotide sequence of the type X collagen gene promoter was determined by sequencing PCR-based DNA clones. Nucleotide identity of this fragment between the normal and TD carriers was 97.6%. Both normal and TD birds were similar in a putative transcription start site, the site of TATAA box, and neither had a CCAAT box. However, there were two gaps in TD carriers, four gaps in normals, and five nucleotide substitution sites. By rapid amplification of cDNA ends by PCR (RACE-PCR), transcription of the gene was assessed using total RNA and mRNA from both normal chondrocytes and TD lesions at 3 and 4 wk of age. The RACE-PCR product for type X collagen mRNA was detectable in both normal and TD birds at two stages. No difference was found between them. This result does not support the hypothesis that transcriptional regulation of type X collagen gene is important in TD development of chickens. Variations in the promoter region did not affect transcription of type X collagen gene in TD carrier chickens.

The distribution of a chondroitin-6-sulfate (C6S) epitope, which is a biochemical marker of chondrocyte hypertrophy, was studied in the growth plates of two lines of 3-week-old broiler chickens with low and high genetic predispositions to tibial dyschondroplasia (TD). Ultrathin sections of growth plates from both groups were subjected to immunolocalization with monoclonal antibody 3-B-3(-), the epitope of which is increased on proteoglycans made by hypertrophic chondrocytes. Bound antibody was localized with colloidal gold-labeled protein A for observation with an electron microscope. The 3-B-3(-) epitope was localized in pericellular and interterritorial matrix of growth plates of both lines. In the low-TD-incidence birds, the concentration of 3-B-3(-) bound to C6S progressively increased from the proliferative zone to the hypertrophic zone. However, in the high-TD-incidence line, the epitope expression remained at a low level in all zones. The increase of the 3-B-3(-) epitope produced by maturing growth-plate chondrocytes is indicative of changes in the glycosaminoglycan chains of proteoglycans that may be important in the process of matrical calcification. Thus, failure of chondrocytes of the high-TD-incidence line to produce this change in post-translational modification of their proteoglycans could be important in the pathological process.

An experiment was conducted to determine the effect of divergent selection for tibial dyschondroplasia (TD) on live performance of broilers. Broilers used in the experiment were produced from the parental lines selected for high (H) and low (L) incidence of TD and a randombred control (C) line. Diallel crosses were made between H and L lines. The offspring produced were HH, HL, LH, LL, and CC, where the first letter refers to sire line and the second letter refers to dam line. Body weights, average daily body weight gains, and exponential growth rates were determined at weekly intervals. The incidence of TD was recorded at 4 and 7 wk of age. There was no difference among body weights of lines up to 5 wk of age. Sire lines influenced body weights of birds from 5 to 7 wk of age. A significant interaction between sire and dam lines for body weight was the result of decreased body weights of birds in the HH line from 5 to 6 wk of age. There was a similar interaction for body weight gain, which resulted in a slower growth rate of birds in the HH line from 3 to 5 wk of age. Tibial dyschondroplasia incidence was 84.1 and 92.0% in the HH line, 5.6 and 5.4% in the LL line, and 7.0 and 13.2% in the CC line at 4 and 7 wk of age, respectively. It was suggested that genetic predisposition for TD was independent of body weight.

Lines selected for high (H) and low (L) incidence of tibial dyschondroplasia (TD) for eight generations and a randombred control (C) line of broiler chickens were fingerprinted by random amplification of genomic DNA mixed from 20 individuals of each line with 20 oligonucleotide primers. Among these 20 primers, 15 could distinguish the H from the L line, 14 the H from the C line, and 13 the L from the C line. Band sharing (BS), on the average over 20 primers, was .7 for the H vs L comparison and .8 for both H vs C and L vs C comparisons. The levels of BS calculated from individuals was .6 between the H and L line, .7 between the H and C line, and .7 between the L and C line. The ranking of BS values obtained from individual DNA samples was consistent with that obtained from the mixed DNA samples. Genomic distance between divergently selected lines (H vs L) was larger than that between the divergently selected lines and randombred line (H vs C and L vs C). Individual variation within lines was detected in spite of eight generations of selection. Results showed that eight generations of divergent selection for TD incidence in broiler chickens had resulted in genetic variation among lines. The procedure of random amplified polymorphic DNA assay using mixed DNA samples could be used to evaluate genetic distance among lines of chickens.

Relationships among the incidence of tibial dyschondroplasia (TD) with 7-wk live BW, carcass component weights (CCW), and abdominal fat weight (AFW) were assessed using high and low incidence of TD lines developed by a seven-generation divergent selection experiment, along with a randombred control line. The incidence of TD exhibited negative genetic correlations with both BW (-.65 and -.46 estimated from sire's and dam's components of variance and covariance, respectively) and with CCW (< -.28). The incidence of TD and AFW was not correlated based on sire's components of variance and covariance. The correlation of TD incidence with AFW was not as high as with the other traits under consideration based on dam's components of variance and covariance. Correlations of AFW with CCW were negative based on sire's components of variance and covariance, but positive based on dam's components of variance and covariance. Heritabilities of TD, BW, AFW, and CCW estimated by sire's variance components were lower than those estimated by dam's variance component. Dams might have a greater influence on TD incidence than sires. Selection for decreasing TD incidence should be feasible while simultaneously increasing BW and CCW in broilers.

The advent of molecular genetic markers has stimulated interest in detecting linkage between a marker locus and a quantitative trait locus (QTL) because the marker locus, even without direct effect on the quantitative trait, could be useful in increasing the response to selection. A correlation method for detecting and estimating linkage between a marker locus and a QTL is described using selfing and sib-mating populations. Computer simulations were performed to estimate the power of the method, the sample size (N) needed to detect linkage, and the recombination value (r). The power of this method was a function of the expected recombination value E(r), the standardized difference (d) between the QTL genotypic means, and N. The power was highest at complete linkage, decreased with an increase in E(r), and then increased at E(r)=0.5. A larger d and N led to a higher power. The sample size needed to detect linkage was dependent upon E(r) and d. The sample size had a minimum value at E(r)=0, increased with an increase in E(r) and a decrease in d. In general, the r was overestimated. With an increase in d, the r was closer to its expectation. Detection of linkage by the proposed method under incomplete linkage was more efficient than estimation of recombination values. The correlation method and the method of comparison of marker-genotype means have a similar power when there is linkage, but the former has a slightly higher power than the latter when there is no linkage.

Growth plates from the proximal tibiotarsal bones of growing broiler chickens from lines exhibiting high and low incidences of tibial dyschondroplasia (TD) were compared for ultrastructural differences. Samples of growth plates were collected from five chickens of each line at 2, 7, 14, and 21 d of age. Each sample was prepared for ultrastructural evaluation after initial fixation in 2.5% glutaraldehyde and secondary fixation in 1% osmium tetroxide, each containing .7% ruthenium hexamine trichloride. No gross TD lesions were observed. The ultrastructure of growth plates of birds at 2, 7, and 14 d of age was similar between the groups. However, at 21 d of age, chondrocytes in the prehypertrophic zone of the high incidence group contained large lipid inclusions and vesiculated and disarranged stacks of rough endoplasmic reticulum with greatly dilated cisternae. Apoptotic and necrotic chondrocytes were present in the hypertrophic zone. Nuclei of apoptotic chondrocytes contained crescentic caps of condensed chromatin. The cytoplasm contained short segments of dilated granular endoplasmic reticulum, lipid droplets, and vacuoles. Necrotic chondrocytes appeared as amorphous masses with pyknotic and karyorrhectic nuclei. These changes were not observed in chondrocytes of the low TD incidence group and have not been previously reported in nonthickened growth plate cartilage.

Broiler breeder pullets were subjected to photostimulation (PS) at either 14, 17, or 20 wk of age after attaining greater than recommended BW during rearing in order to determine effects on age at onset of lay, egg weight, and egg production. During rearing, feed was consumed ad libitum (AL) or provided in allotments resulting in growth to projected BW of 2.8 (heavy, HV) or 2.3 kg (light, LT) at 20 wk. Rearing period feeding and age at PS treatments made up a 3 x 3 factorial arrangement. A single restricted feeding program was provided during lay. Although age at first egg in the AL treatment was earlier than in HV and LT treatments, total production by HV and LT birds was greater because peak and postpeak production by AL birds were depressed. Relative to PS at 20 wk, PS at 14 and 17 wk advanced age at first egg and increased cumulative production to 30 wk. However, early PS decreased peak production and, therefore, did not affect total production. Mean egg weight and settable egg production (egg weight > 50 g) were increased in HV and LT treatments. Egg weight and settable egg production were not affected by age at PS. These results indicate that the onset of lay by broiler breeders can be advanced by early PS and that increased BW facilitates this. However, allowing greater BW during rearing does not compensate for reduced early egg weights and results in decreased total production and mean egg weights when feed is provided at recommended levels during lay.

Selection for a high or a low incidence of tibial dyschondroplasia (TD) at 7 wk of age was practiced for four generations in broiler breeders keeping an unselected control (C) line and using low intensity X-ray imaging for TD diagnosis. The incidence of TD, BW at 4 and 7 wk of age, age at first egg, and egg production for the first 12 wk of production were determined in the four generations. Age at initial semen production and semen volume and concentration of males were determined only in Generations 3 and 4. The TD scores and BW at 7 wk were collected on 1,366, 1,301, and 1,389 broilers from the C, high (H), and low (L) incidence of TD lines. Incidence of TD at 7 wk in the fourth generation was 16.1, 61.9, and 3.5% for the C, H, and L lines, respectively. There were no significant differences in BW between the H and L lines in Generations 1, 3, or 4. However, in Generation 2, the H line was heavier (P < .01) than the L line. Second generation H line broilers with TD were heavier than those without TD at 4 and 7 wk of age (P < .01). There were no significant differences in age at first egg, age at semen production, or in semen volume between the H and the L lines. Egg production in the L line was greater (P < .01) than that of the H line in all four generations, and semen concentration was also greater (P < .01) in Generations 3 and 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Selection for a high (H) or low (L) incidence of tibial dyschondroplasia (TD) at 7 wk of age was practiced for four generations in broiler breeders using low intensity x-ray imaging (Lixiscope) for TD diagnosis. As a result, broiler lines with H or L incidence of TD at 7 wk of age were developed keeping a randomly selected control (C) broiler line. A total of 4,232 chicks were hatched representing 172 sires and 612 dams over four generations for the H, L, and C lines. The TD scores at 7 wk were collected on 4,056 broilers. Incidence of TD at 4 and 7 wk of age were studied in the C, H, and L lines of broilers. Direct response to selection in the H and L lines were estimated per generation and per weighted cumulative selection differential (WCSD). Total WCSD deviation from the C line for incidence of TD at 7 wk of age was 1.496 and -.42 units for the H and the L lines, respectively. The response per generation for incidence of TD at 7 wk of age for the H line was .153 +/- .028 units. The realized heritability for the H line for incidence of TD at 7 wk of age was .437 +/- .065. The incidence of TD was not significantly decreased in the L line at 7 wk of age.

One hundred and eight 24-wk-old broiler breeder males were arranged into 18 groups of six birds of equal average BW. Six groups were killed for carcass evaluation at 24 wk of age; the other 12 groups were divided between two dietary treatments. One treatment was a typical breeder-recommended male broiler breeder ration (standard, or ST; 12% CP, 3,160 kcal ME/kg), whereas the other was a low-protein, corn-based diet (all corn, or AC; 8% CP, 3,220 kcal ME/kg) formulated to approximate minimum amino acid requirements for positive nitrogen balance. All birds were fed at a rate of 325 kcal ME/day per bird to 68 wk of age. Body weight, semen volume, and sperm concentration were evaluated weekly. All birds remaining at 68 wk were killed for carcass evaluation. Feed and age effects on BW were highly significant (P less than .001). However, birds did not respond similarly to treatments with increasing age. Birds fed ST were heavier and surpassed breeder-recommended BW by 38 wk of age, whereas birds given AC were lighter and remained below breeder-recommended weights throughout the study. Semen production was measured by semen volume, sperm concentration, total sperm yield, and proportion of males producing semen; values were similar for treatments at all ages. Birds given the AC feed had more carcass fat than ST-fed birds at 68 wk of age, but ST-fed birds had the same proportion of fat at 68 wk as birds killed at 24 wk. Results suggest that the amino acid levels provided by the AC diet were less than adequate for optimal BW gain, but adequate for semen production.

Plasma inorganic phosphorous, glucose, uric acid, total cholesterol, total protein, albumin, alkaline phosphatase, lactic dehydrogenase (LDH), and serum glutamic oxaloacetic transaminase (SGOT) were determined in 14-week old turkeys from lines genetically determined for high and low blood pressure. The turkeys received a commercial grower diet (control), control + 10% animal fat, or control + 10% animal fat and 1% cholesterol. Concentrations of uric acid in plasma were higher (P less than or equal to .05) in the control-diet group than in the other dietary groups, and the high blood pressure line had significantly higher (P less than or equal to .05) concentrations of uric acid in plasma than the low blood pressure line. Turkeys fed the diet containing added cholesterol had higher levels (P less than or equal to .05) of total plasma cholesterol than those receiving the other diets. Alkaline phosphatase levels of plasma were significantly lower (P less than or equal to .05) in the control-diet group than the other dietary groups. There were no other effects within either of the genetic blood pressure lines that indicated blood pressure had any influence on blood plasma constituents other than uric acid, nor was there any indication that dietary treatment had any effect within either blood pressure group. Blood pressure and plasma constituents were not correlated.

Eggs from Single Comb White Leghorn chickens were divided into two approximately equal groups with the range of specific gravities being present in each group. One group was incubated in a darkened Humidaire Hatchett while the other was incubated in an identical machine equipped with two 20 Watt fluorescent tubes which produced 8.3 X 10(3) ergs/cm.2-sec. at the surface of the eggs. The recommended temperature and humidity settings were used in both machines. After 7 days of incubation embryos from the lighted incubator were significantly (P less than .01) larger than those incubated in the dark. There were significantly more live embryos from low and high specific gravity eggs in the light than in the dark. There was no difference in embryonic mortality between groups for the eggs with intermediate specific gravities. Embryos from White Leghorn eggs incubated in the presence of light were significantly (P less than .01) larger on each day of incubation from day 2 through hatch. Eggs incubated in the lighted incubator hatched at 18 and 19 days and produced larger chicks than those hatched at 20 and 21 days in the dark.

Some features of the aortic intima were examined with the scanning electron microscope (SEM) and found to contribute to the etiology of dissecting aneurysm. The endothelium over intimal plaques was not as pendulous as endothelium surrounding plaques. The pendulous appearance of aortic endothelial cells could be associated with the contractile nature of these cells. Some undescribable factor, which has been termed stress or atherosclerosis, seemed to reduce the contractile nature of endothelial cells on the plaque areas. Analyses with SEM revealed a probable cause of a dissecting aneurysm. The effect of pulsating blood pressure on an inelastic endothelium could create a separation between endothelial cells and the fluid pressure of blood could then separate the tissue until the vessel ruptured into the body cavity or back into the aorta. Because all abdominal aortic segments examined had atherosclerosis, it was not possible to show the amount of intimal alteration between normal and atherosclerotic aortas. Each blood pressure line showed a similar change which was 4.52 and 4.95% for the high and low blood pressure lines, respectively. There were no demonstrable correlations in this study between either high or low blood pressure lines of turkeys and atherosclerosis.

Effects of caponization and blood pressure selection on serum lipids, severity of atherosclerosis, body weight, hematocrit, and relative ventricular weight in hypertensive and hypotensive lines of turkeys were evaluated in two trials. At 8 weeks of age, half the turkeys from each line were caponized. Body weights, blood pressure, and blood samples were obtained from each treatment at 8, 20, and 30 weeks of age. A total of 56 and 72 birds were used in Trials 1 and 2, respectively. Birds were necropsied at 30 weeks of age. Hypertensive turkeys had significantly greater serum cholesterol and total lipid than hypotensive turkeys only at 30 weeks of age in Trial 1. Lower relative ventricular weights were observed in hypotensive turkeys within both trials. Hypertensive birds exhibited a more severe degree of atherosclerosis and higher relative heart weight than hypotensive turkeys. Caponization significantly increased total serum lipid only at 20 weeks of age in Trial 2. Average body weight of caponized turkeys was significantly lower (1.2) than the control turkeys at 30 weeks of age. Caponized turkeys exhibited lower relative ventricular weight in Trial 1 but not Trial 2 and an increase in blood pressure only in Trial 2. Caponization suppressed body weight, decreased hematocrit values, and had no significant effect upon plaque severity. The presence or absence of male sex hormones had virtually no effect on proposed atherogenic stimuli thereby suggesting another mechanism by which the female is afforded a higher degree of protection.

Hypertensive and hypotensive strains of turkeys were observed for the possibility of a synergistic response between hypertension and temperature stress. The birds in four experiments were placed in chambers with temperature settings of 15.6, 26.7, and 37.8 C (humidity approximately 60%) and an ambient control. The temperature effect was measured by comparing the responses in body weight-gain, systolic blood pressure, and hematocrit and hemoglobin values. In each experiment both hypertensive and hypotensive strains in the 37.8 C chamber had a significantly lower (P less than or equal to .05) weight gain than those in the other chambers. The 26.7 C chamber had the next lowest weight gain. Considerably more variability in weight gain was observed in the hypertensive strain. Systolic blood pressure data were similar for all experiments. The lowest average blood pressures were recorded in the 37.8 C chamber. The high and low blood pressure strains showed overall average decreases in blood pressure of 28% and 14%, respectively. There was no consistent response in hematocrit and hemoglobin values due to temperature stress. Overall average hematocrit values were 39.1 and 38.0% for the hypertensive and hypotensive strains, respectively, while average hemoglobin values were 11.8 and 12.2 g/dl. The hypertensive strain showed more variation in weight gain, a greater percentage drop in blood pressure, and a 19% mortality rate in the high temperature chambers. These factors indicate that hypertension is an added factor in the overall stress of these birds.

A study was conducted of the reliability and the efficiency of four methods to estimate concentration of spermatozoa in chicken semen. The methods used were hemocytometer, Coulter counter, optical density, and spermatocrit. Twenty-four samples of pooled semen (5 males per sample) were used in this experiment. Sperm concentration estimates were determined on each of three subsamples: pure semen, semen diluted 1:1, and semen diluted 1:3. The average time to prepare and evaluate 6 replications of each subsample with the hemocytometer, Coulter counter, optical density, and spermatocrit methods was 9.0, 2.6, 2.3, and 4.4 min, respectively. Correlation coefficients ranged from .78 to .93 between the hemocytometer and either optical density or Coulter counter in both pure and diluted 1:1 and 1:3 samples. However, no significant correlation was observed between the hemocytometer and spermatocrit in the 1:3 dilution. The reliability expressed as coefficient of variation for each technique was: hemocytometer 17.9%, Coulter counter 1.57%, optical density 2.24%, and spermatocrit 9.95%. It is concluded from these results that the optical density and Coulter counter methods are more reliable and more efficient (less time consuming) than either hemocytometer or spermatocrit methods in estimating semen concentrations in chickens.

White Leghorn eggs were incubated in the dark or under two 20-Watt cool white flourescent tubes. The embryos were collected and staged according to somite number and other anatomical observations. Embryos from lighted eggs were significantly more advanced in embryonic age within 24 hours than embryos from the dark. By the end of 10 days no further acceleration of development by light was significant.

Blood pressures and heart rates were recorded from two groups of turkeys in two trials. In trial one 20 turkeys, 36 weeks of age and in trial two 24 turkeys, 14 weeks of age, were used. Immediately after blood pressures and heart rates had been determined, the turkeys were killed and vascular tissues were excised. Equal numbers from hypertensive and hypotensive lines of turkeys were used in each trial to determine the rupture pressure of both the elastic and muscular segments of the aorta. When values for the two trials were combined, mean hydrostatic pressures of 1478, 1804, and 794 mm Hg respectively were required to rupture the most caudal abdominal aortic segment, the adjacent cranial abdominal segment, and the thoracic aortic segment. There was a significant difference between the two lines for blood pressure in both trials and for heart rate in trial 2. There were no statistically significant correlations between blood pressure, atherosclerotic plaque score and rupture pressure. Birds fed on a diet containing added fat and cholesterol had significantly lower blood pressures than the birds fed on the other two diets. Birds receiving added dietary cholesterol and fat had lower heart rates than birds fed on the diet with added fat only. Lower plaques scores were evident in the caudal abdominal aorta of the birds fed on the control diet compared to birds fed on the other two diets.

Twenty-one male Broad Breasted White turkeys which had been selected for high or low blood pressure were put on an exercise regimen to determine its effect on semen quality. Eleven were from the hypertensive line and 10 from the hypotensive line. Eleven (6 hypertensive and 5 hypotensive) turkeys were placed on an exercise regime of walking (herding) about 1 mile daily for 6 weeks before the experiment began, and then for a further 6 weeks during semen collection. Semen was collected from 11 turkeys on the exercise regime and 10 nonexercised control birds which were kept in their experimental pens during the trial. Both hypertensive and exercised groups showed an improved semen colour score at the first collection period (P less than or equal to 0.09). Only the exercised group showed a significantly (P less than or equal to 0.05) better score than the control group during periods 2 and 3. The hypertensive line showed significantly higher spermatozoa count than the hypotensive line during the first collection period. There was no effect of either exercise or selection for high or low blood pressure on semen volume.

1. Seventy Hubbard hens, 75 weeks of age, were divided into groups containing equal numbers of hens on the basis of duration of fertility. Average fertile periods were 14.5 d (long, L) and 6.9 d (short, S). Each hen was artificially inseminated (AI) on three consecutive days with an average of 1.61 X 10(9)/0.05 ml spermatozoa per insemination. Seven hens from each group were killed 1, 3, 6, 9, and 13 d after insemination. 2. Three longitudinal sections of uterovaginal junction were evaluated microscopically for spermatozoal storage capacity by assigning each sperm host gland (SHG) to one of 5 categories: unscorable, empty, one to 5 spermatozoa, 6 to 20 spermatozoa and greater than 20 spermatozoa. 3. The only significant difference in sperm storage at any time between the L and S duration groups occurred at day 1 after AI, when L duration hens possessed significantly more glands with more than 20 spermatozoa. 4. One day after AI the proportion of SHG containing sperm were 28.8% (L group) and 18.6% (S group). There was a significant decrease in the number of glands containing 1 to 5, 6 to 20 and greater than 20 spermatozoa between days 1 to 3 in both groups. 5. Numbers of glands in all categories containing sperm decreased throughout the 13-d period. The L duration group possessed 18.5% more glands with 1 to 5, 6 to 20 and greater than 20 spermatozoa than the S duration group. 6. There were no significant differences between groups in the proportion of unscorable or empty glands throughout, which ranged from 35.9 to 56.8% and 36.3 to 47.1%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Egg characteristics, feed efficiency (egg mass/daily feed intake), and performance efficiency (egg mass/body weight) were studied in dwarf White Leghorns after four generations of selection for divergent body weight at 20 weeks of age. Sexual maturity and livability were not significantly different among high (H), low (L), or control (C) lines. Mean 20-week body weights for H, L, and C lines were 1.50 kg, .76 kg, and 1.02 kg, respectively. Daily feed intake, egg mass, egg weight, and yolk, albumen, and shell weights were significantly (P less than .05) different between H and L hens and were directly related to body weight. Percent yolk was greatest and percent yolk mottling and percent albumen were lowest in eggs from L hens. Percent shell was not significantly different among the lines. Albumen quality (Haugh units) was significantly better in eggs from H and L hens than from C hens. Percent hen-day egg production was not significantly different among lines. Feed efficiency was greatest in C hens with both C and L hens significantly more efficient than H hens. Performance efficiencies of C and L hens were significantly better than H hens throughout the experiment, and L hens were significantly more efficient than C hens during peak egg production. These results suggest that there may be minimum body weight requirements for efficient egg production.

At 43 days of age, 246 broiler breeder males were randomly assigned to either a 9, 12, or 15% protein diet (isocaloric) fed on a restricted basis until birds were 50 wk of age. Birds fed the 15% protein diet served as the control group for maintaining body weight. All groups received equal quantities of feed. Semen production was monitored weekly from 17 through 49 wk of age. Semen was evaluated for volume, concentration, and number of spermatozoa per ejaculate during four periods: 25 through 30, 36 through 37, 42 through 43, and 48 through 49 wk of age. Carcass composition and testes weight were sampled at 22 and 28 wk; at 50 wk of age all remaining males were analyzed. The dietary protein effect on body weight was linear (P less than .05). Birds fed the 9% protein diet had the lowest weights, while birds fed 12 and 15% protein became similar in body weight with increasing age. Semen volume, concentration, number of spermatozoa per ejaculate, and testes weight were unaffected by dietary protein level. The percentage of males that produced semen when fed the 9% protein diet was greater (P less than or equal to .09) with males fed 12 and 15% dietary protein. Dietary protein had a significant negative linear effect (P less than or equal to .001) on percent carcass fat at 50 wk of age but no effect on percentage carcass protein. Reducing dietary protein to 9% decreased male body weight slightly, increased carcass fat, and had no adverse effects on semen production through 50 wk of age.

Two-hundred broiler-type chickens were reared under either normal lighting or darkness for 16 weeks. Each week, birds were subjected to applanation tonometry for measurement of intraocular pressures (IOP). The birds were then weighed, eye enucleated, and dimensions measured. All eyes were prepared for histological examination. Chickens reared in darkness for 4 to 6 weeks displayed an abnormal eye enlargement, accompanied by an increase in IOP in comparison to chickens reared under conventional management. From the 6th to the 16th week, the eyes of dark-reared chickens continued to enlarge while IOP decreased. The sclera, choroid, retina, and retinal layers of dark-reared chicks were not as thick as controls throughout the 16 weeks. Two principle retinal pathologies were induced by darkness. One appeared as darkened areas of the peripheral retina. In histological sections the darkened retinal areas had a thin choroid and thin retinal layers. The second retinal abnormality was one or more white, nonpigmented bands directed perpendicular to the pectin. Histologically, the depigmented bands were areas in which the vessels of the choroid, the pigmented epithelium, and the outer retinal layers were absent. The corneas of dark-reared chicks exhibited a reduction in their curvature and thickness compared to control corneas.

Plasma corticosterone levels of hypertensive and hypostensive turkeys were 2.50 and 2.19 micrograms/dl, respectively. Male turkeys of both strains had a mean plasma levels of 2.47 micrograms/dl and female turkeys had a mean level of 2.21 micrograms/gl. The average plasma corticosterone level for all turkeys was 2.35 micrograms/dl. Although the plasma corticosterone levels were higher at 1200 hr than at either 0800 or 1600 hr, the differences were not statistically significant. It was condluded that blood pressure selection had no significant effect on plasma corticosterone levels.

Relationships among age, blood pressure, and atherosclerosis were studied in turkeys genetically selected for high and low systolic blood pressure ranging in age from 2 days to 104 weeks. Relationships between sex and atherosclerosis were studied only at 104 weeks of age. Abdominal aortas were examined in all birds in each age group. The left and right internal, external, and common carotid arteries, cranial and caudal thoracic aortas, area of coeliac orifice, sciatic junction, left and right sciatic arteries, left and right coronary arteries, and left and right deep branches of the coronary arteries were examined in the 104-week-old group. Mean abdominal aortic plaque scores for the different age groups increased linearly to the age of 12 weeks; after this time scores reached a plateau. Except for the first and last time period, the hypertensive group of males showed a significantly greater abdominal aortic plaque score than the hypotensive group. The right sciatic artery was the only other blood vessel in the 104-week-old group that had a significantly greater plaque score in the hypertensive line when compared with the hypotensive line. In the 104-week period, only the left and right sciatic arteries showed significantly higher plaque scores in the males than in the females. Also, only the male turkeys showed an increase in plaque scores with a concomitant rise in systolic pressure. In 104-week-old females there was no evidence of intimal change in either the left and right internal carotids, left and right common carotids, cranial thoracic aorta, or the right coronary artery. The hypertensive line had significantly greater blood pressure and greater ventricular weight, length, and sagittal width than the hypotensive line. The 104-week-old turkeys had more lipid staining material within the plaque than the younger birds, and calcification was evident in two of the older turkeys.

One hundred sixty-two dwarf broiler breeder females were each inseminated at 4-wk intervals with either 30, 60, or 120 million spermatozoa repeated on 2 consecutive days. The experiment was conducted at two age periods, i.e., 32 to 41 wk (Period I) and 55 to 63 wk (Period II). Females during Period II had a significantly shorter duration of fertility than during Period I (P less than .0001). Also, the mean duration of fertility but not maximum percent fertility was improved in females inseminated with the highest doses compared with the lower doses of spermatozoa. Individual fertility results confirmed that a large majority of the females (81 to 93% during Period I and 62 to 76% during Period II) are capable of laying 100% fertile eggs for at least 7 days. The mean duration of fertility during Period II was longer in females primarily classified as having the longest duration of fertility in Period I. This confirms that duration of fertility is consistent during the reproductive life.

Three preproduction feeding regimens were used to determine their effects on reproductive performance of broiler breeder females. Three hundred 16-week-old Arbor Acre females were divided into three treatment groups. Treatment 1 was placed on full feed at 17 weeks of age and remained on this schedule for 5 weeks. At 22 weeks of age they were placed on a diet consisting of 136 g of feed per bird per day and remained on this schedule until the experiment was terminated at 60 weeks of age. Treatments 2 and 3 reached peak feed intake at 26 and 30 weeks of age, respectively. Age at maturity, eggs per hen housed, and feed conversion were significantly affected by preproduction feeding regimens. Treatment 1 matured significantly earlier than Treatments 2 and 3; however, feed conversion was significantly higher (grams of feed per egg) than in Treatments 2 and 3. In general, shell quality; and egg weights were lower in Treatment 1 than in Treatments 2 and 3 throughout most of the experiment. There were no differences in shell quality or egg weights between Treatments 2 or 3. There was a significant difference in egg production among all treatments at the 60-week production period, Treatment 1 being the lowest and Treatment 3 being the highest.

Forty male and 240 female broiler breeders were placed in cages within environmental chambers (20 males or 40 females per chamber) at 14 weeks of age. Chamber temperatures were maintained at 21.3 +/- 2.5 C, and relative humidity (RH) ranged from 40 to 50%. Ventilation rate was approximately 47.2 liters/sec per chamber, and light was provided from 0600 to 1800 hr. Feed was restricted daily according to industry recommendations, and water was provided ad libitum. From 17 to 20 weeks of age, control (C) chambers were kept at constant 21.0 +/- 1.4 C with 45 +/- 5% RH, and heat-treated (HT) chambers were cycled from 24.4 +/- 5.5 C (45 +/- 5% RH) during 1800 to 0800 hr to 36.0 +/- 2.8 C (15 +/- 5% RH) during 0800 to 1800 hr. Body weights were recorded at biweekly intervals. At 18 and 20 weeks of age, blood samples and rectal body temperatures were obtained randomly from five fasted birds per chamber at 0800 and 1400 hr. From 20 to 60 weeks of age, all birds were kept in individual cages in a conventional fan-ventilated house. Maximum temperature never exceeded 30 C, and average RH was 65.0%. Reproductive parameters were monitored and body weights were obtained at 4-week intervals. There were no significant treatment effects for body weight, body temperature, or differential leukocyte counts. Hematocrits were significantly lower for HT females than controls, and heat treatment did not result in consistent changes in plasma glucose or total proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Because of the considerable variability in the oxygen dissociation curves for chickens reported in the literature, the respiratory physiologist studying avian gas exchange is faced with the dilemma of which curve is representative for the chicken. In order to arrive at a representative curve, data from eight reported curves were compiled and adjusted to the same set of standard conditions of temperature (T), pH, and partial pressure of carbon dioxide (PCO2): T = 42 C, pH = 7.5 PCO2 = 40 torr. The mean PO2 STD (mean +/- SD) versus percent saturation of hemoglobin curve was then determined. The mean data were fitted to an equation representing the oxygen dissociation curve so that for any selected partial pressure of oxygen (PO2) the percent saturation (%SAT) of oxyhemoglobin may be computed. The P50 values for the mean literature and equation curves, respectively, were 47.4 +/- 9.8 and 45.3 Torr. The mean curve with its standard deviations provides a chicken oxygen dissociation curve representative of the literature data to which experimental data may be compared. The equation for the curve enables rapid referral to the representative curve to compute the %SAT, given the PO2 adjusted to the standard conditions.

Chickens raised from 2 to 14 weeks of age in continuous darkness (OL:24D) developed shallow anterior chambers and buphthalmos (megaloglobus). Chickens raised in continuous darkness developed ocular changes similar to that reported in chickens raised in continuous fluorescent and incandescent light and in dim light. Corneal diameters and axial globe lengths were an inconsistent means of documenting ocular enlargement. Iridocorneal angles were narrowed on scanning electron microscopy (SEM). Intraocular pressure (IOP) was not different from control chickens. The chicken is proposed as a model to study ocular development, the effects of lid suture on infants, axial myopia, preglaucomatous changes, and possibly pharmacologic effects of antiglaucoma preparations.

A technique for early detection of tibial dyschondroplasia (TD) in live broilers was developed using the Lixiscope, a hand-held, real-time skeletal imaging device. The Lixiscope utilizes 125I gamma energy (27 keV), which is converted to electrons and then to visible energy, for imaging by way of an output phosphor or electron-to-photon conversion. Image amplication is 45,000 to 50,000 times, and image resolution is 4.2 line pairs per millimeter. The left and right tibiotarsi of the parent stock of male broiler breeder chickens were examined at 3, 4, 6, and 8 weeks of age. The images readily allowed for the detection of TD. A scoring system was established to assess severity of TD and was confirmed accurate as correlated with direct radiography and macroscopic examination at necropsy. This technique offers a quick, non-invasive, early detection of TD in broilers. The equipment is portable and can be used in field selection procedures.

1. Uterovaginal junction (UVJ) tissues were collected 24 h after artificial insemination (AI) from 85- and 125-week-old broiler breeder hens in three physiological states: laying hard shell eggs (HS), laying shell-less eggs (SL) and non-laying (NL). This was confirmed by egg production records and visual appraisal of the oviduct at the time of necropsy. 2. Three longitudinal sections of each UVJ were evaluated microscopically and sperm host glands (SHG) were scored in 5 categories: glandular morphology evident but not lumen present, basophilic stained epithelium and no spermatoza present, glands that contained one to five spermatozoa; glands that contained 6 to 20 spermatozoa and glands that contained more than 20 spermatozoa. 3. Laying hens (HS and SL) at 85 weeks of age had significantly more sperm host glands (SHG) containing spermatozoa than NL hens. At 125 weeks of age HS and SL hens had significantly more unscorable glands. 4. The only category that showed no difference between age and physiological status group was the empty category. No significant differences were observed for any gland category in 82- and 125-week-old NL hens. 5. A greater proportion of the 85-week-old group of HS and SL hens had more SHG containing spermatozoa and fewer unscorable glands that the 125-week-old birds. The only category that showed any difference within the SL group was the low category.

Two trials were conducted to determine the relationship between percent body weight loss (% BWL) during an induced molt and postmolt performance. The molt was induced by fasting and photoperiod manipulation. Four groups with 24, 27, 31, or 35% BWL (Trial 1) or 20, 25, 30, or 35% BWL (Trial 2) were utilized in each trial. Performance was evaluated on the basis of 24 weeks of egg production and determinations of egg weight (EW), specific gravity (SG), and shell weight (SW) conducted during Weeks 8 (Trial 2 only), 18, and 24 following the removal of feed. The 27 and 31% BWL groups of Trial 1 and the 30 and 35% BWL groups of Trial 2 produced significantly more eggs per hen housed than the remaining treatments in their respective trial. Differences in SG and SW at the end of the trial were most pronounced in Trial 1 where the 27 and 21% BWL groups exhibited significantly greater SG and SW at Week 24 than did the 24 or 35% BWL groups. No significant differences occurred for SG at Week 24 of Trial 2, but the 35% BWL group exhibited significantly improved SW when compared to the 25% BWL group with the remaining groups intermediate. The EW was greatest for the 31% BWL and least for the 35% BWL group at 24 weeks in Trial 1 but did not differ in Trial 2. It was concluded that a body weight loss of approximately 27 to 31% produced optimum postmolt performance.

Fertility among hens artificially inseminated (AI) at different stages of the laying sequence were compared in two experiments with broiler breed (Experiment 1) and egg-type hens (Experiment 2). The different stages of the laying sequence were prepause (PP)-oviposition without ovulation, pause (P)-no oviposition with or without ovulation, and nonpause (NP)-oviposition with ovulation. There were no significant differences among PP, P, and NP groups for duration or percent fertility in Experiment 1. Fertility and duration were significantly lower in PP than NP in Experiment 2. However, these differences were most likely caused by 36% of the PP hens ovipositing during the time of AI. Time of AI seems to be a more important factor in determining subsequent fertility than the day of AI during the laying sequence.

Numerous investigations of light induced avian buphthalmia using incandescent light have not defined an etiology. Chickens raised from 2 weeks of age in continuous fluorescent light developed shallow anterior chambers and buphthalmos within the first month of treatment. Chickens raised in continuous fluorescent light developed ocular enlargement similar to that reported in chickens raised in continuous incandescent light. Corneal diameters and axial globe lengths were an inconsistent means of documenting ocular enlargement. Iridocorneal angles were narrowed on scanning electron microscopy.