Enzyme activity and organ development in newly hatched chicks selected for high or low eight-week body weight

Cockerels from lines of White Plymouth Rock chickens selected for 33 generations for high (HW) or low (LW) 8-wk BW were used in this experiment. Either Diet A (a diet similar to that under which selection had been conducted) or Diet B (containing 20% more CP and 20% more ME) were consumed ad libitum for the entire experiment (hatch to 6 wk of age). Body weights, organ weights, and enzymes present in the gastrointestinal tract (GIT) contents and pancreas were measured. There were differences between lines and between diets for BW and relative breast weight. Several organs (heart, lung, liver, and pancreas) generally remained a constant proportion of BW in both lines. Relative weight of the GIT was greater in HW cockerels from hatch to 10 d of age, after which relative GIT weight was greater in LW cockerels. Relative weight of the GIT was also affected after 10 d of age by density of feed. Interactions between line and diet were present for many digestive enzyme measurements, necessitating analyses within each main effect. All pancreatic enzymes except relative trypsin were higher in HW than LW cockerels. Although small intestine enzyme activities were higher in Line HW than LW, Cockerels on a relative basis the difference was present only for trypsin activity. Cockerels fed Diet B had higher levels of pancreatic chymotrypsin activity and of total and relative lipase activities than those fed Diet A.

Inhibition of adrenal steroidogenesis, neonatal feed restriction, and pituitary-adrenal axis response to subsequent fasting in chickens

White Plymouth Rock chickens placed under 60% feed restriction or ad libitum feeding, with or without metyrapone (adrenal blocking agent) treatment, from 4 to 6 days of age were subjected to either 8 or 24 hr feed deprivation at 36 days of age. Chicks subjected to the neonatal 60% feed restriction (60R) but not those provided metyrapone during the procedure (60M) had elevated heterophil/lymphocyte (H/L) ratios. However, there was no difference in plasma corticosterone and ACTH responses between 60R and 60M chicks. Except for increases in H/L and plasma corticosterone concentrations among ad libitum fed (AL) and 60M chickens, respectively, there was no indication of stress response attributable to the subsequent 8 hr fast. Feed withdrawal for 24 h did not cause rises in H/L ratios and plasma levels of corticosterone of chicks that had been subjected to early 60% feed restriction with nonmetyrapone-treated feed. In contrast, chicks of other regimens had elevated H/L and plasma corticosterone responses when exposed to a similar procedure. Except for those fed ad libitum during the neonatal stage, circulating levels of ACTH declined following the 24-hr fast. These results demonstrate that stress early in life without concurrent rises in circulating corticosteroid levels may not help the biological system in coping with subsequent stressors.

Responses to long-term divergent selection for eight-week body weight in chickens

Thirty-six generations of divergent selection for body weight at 8 wk of age resulted in approximately an eightfold difference between the high (HWS) and low (LWS) lines for this trait. In both White Plymouth Rock lines, selection intensities declined over generations, with responses about five times greater during the first 18 than the last 18 generations of selection in Line HWS and about two times greater in Line LWS. Also, responses to selection were more irregular in the later than in earlier generations. Sexual dimorphism of body weight (male:female) was greater for Line LWS than HWS. A randombred control line (AC) maintained concurrently with the selected lines did not exhibit environmental trends across generations. Relaxed lines, established at different generations of selection, were used to evaluate effectiveness of selection and monitor environmental changes over short periods.

Long-term comparisons of eight-week body weight for a randombred line of chickens reared at two locations

For 36 generations, 8-wk body weight was measured in Athens-Canadian Randombred males and females reared at the Southern Regional Poultry Genetics Laboratory (SRPGL) and at Virginia Polytechnic Institute and State University. Regressions of this trait on generations ranged from -.7 g for females reared in Virginia to -2.6 g for males reared at the SRPGL. Chickens were consistently heavier at the SRPGL, where a broiler diet was fed, than at Virginia, where the diet was considerably lower in protein and energy. Highly significant (P < or = .01) location by generation interactions reflected fluctuations at one location that were independent of those at the other location. Correlations between body weight at the two locations increased when chicks were vaccinated for Marek's disease.

Genetic diversity among commercial chicken populations estimated from DNA fingerprints

Blood samples were obtained from parental pure lines representing a large majority of commercial meat-type (broiler) and white egg layer lines presently available in the USA. From blood mixes of each line, DNA was extracted and a DNA fingerprint pattern characteristic of that line was produced. Additionally, DNA fingerprints representing wild jungle fowl and two randombred control populations were produced. Three analyses were conducted: 1) among broiler sire lines, jungle fowl, and one control line; 2) among broiler dam lines, jungle fowl, and one control line; and 3) among parental lines of white egg layers, jungle fowl, and the second control line. Bandsharing levels were calculated, providing an estimate of genetic diversity among lines. Conclusions were that, at present, broiler sire lines, broiler dam lines, and parental lines of white egg layers that make up the majority of commercial breeding populations available in the USA contain a considerable reservoir of genetic diversity.

Inhibition of adrenal steroidogenesis, food restriction and acclimation to high ambient temperatures in chickens

1. White Plymouth Rock chickens placed under 60% food restriction or ad libitum feeding, with or without metyrapone treatment, from either 4 to 6 (early) or 24 to 26 (late) d of age were exposed to high ambient temperatures (35 +/- 2 degrees C) from 36 to 43 d of age. 2. Stress attributable to fasting was not manifested through leucocytic alteration when food-restricted chicks were supplemented with an adrenal blocking chemical, metyrapone. 3. Provision of metyrapone during the fasting period resulted in inferior compensatory growth during refeeding. 4. Exposure to high temperatures from 36 to 43 d of age did not cause an elevation in the heterophil:lymphocyte (H/L) ratios of chicks that had eaten metyrapone-treated food ad libitum during the neonatal stage. 5. During heat exposure, chicks that had been subjected to early 60% restriction with non-metyrapone-treated food had lower H/L ratios and improved resistance to marble spleen disease infection.

Food restriction early or later in life and its effect on adaptability, disease resistance, and immunocompetence of heat-stressed dwarf and nondwarf chickens

1. Dwarf and nondwarf chickens placed under 60% food restriction from either 4 to 6 (early) or 24 to 26 (late) days of age were exposed to high ambient temperatures (35 +/- 2 degrees C) from 36 to 43 d of age. 2. As measured by heterophil/lymphocyte (H/L) ratios, stress response to food restriction was similar at both ages for dwarfs while less at the younger than the older age for nondwarfs, resulting in a significant food restriction interaction of genotype by age. 3. Nondwarf chickens food restricted at the younger age had smaller increases in H/L ratios, improved resistance to marble spleen disease infection and greater growth than those restricted at the older age or fed ad libitum in response to the high ambient temperatures. 4. For dwarf chickens feeding regimen had no influence on response to the environmental insults. 5. Antibody response to sheep erythrocyte antigen was not affected by genotype or feeding regimen.

Heterophil to lymphocyte ratios during perinatal and neonatal stages in chickens

1. Heterophils (H) and lymphocytes (L) were measured in embryos that had pipped into the air cell and through the shell, and in chicks from 0-d-old to 8 d of age. 2. Numbers of lymphocytes in the perinatal stages were very low with H:L ratios greater than 5.0. 3. Posthatching H:L ratios decreased in a quadratic manner from 1.76 at hatch to 0.39 on day 8.

Brucella abortus antibody response of white Leghorn chickens selected for high and low antibody responsiveness to sheep erythrocytes

Three experiments were conducted with lines of chickens selected for high (HA) and low (LA) antibody response to sheep erythrocytes to determine their antibody responses following primary immunization with Brucella abortus. In Experiment 1, HA chicks responded to immunization with a higher total titer than LA chicks at 7 d postimmunization. At both 5 and 7 d following immunization 2-mercaptoethanol-resistant (IgG) titers were higher in HA than LA chicks. There also was a significant sex effect at 7 d in the first experiment, with males having higher total titers than females. In the second experiment, HA chicks had higher total titers at 5 d postimmunization than LA chicks, but IgG titers were similar for both lines. Total and IgG titers of HA chicks used in Experiment 3 were significantly higher than those of LA chicks at 5 and 7 d postimmunization. Both HA and LA chicks exhibited divergent antibody responses to B. abortus although they had originally been selected for antibody responsiveness to sheep erythrocytes.

Removal of residual yolk at hatch influences food choice and feeding activity in lines of chickens selected for high or low juvenile body weight

The effect of residual yolk removal at hatch on growth and feeding behavior was assessed in lines of chickens divergently selected for low (LW) or high (HW) 56-day body weight. At hatch chicks were assigned to 1 treatment: removal of the residual yolk (R) or no surgery (I). Twenty-four chicks per line (12 I and 12 R) were assigned to an all-mash regimen (M) and 48 per line (24 I and 24 R) to a choice (C) between mash and dietary residual yolk. HW were heavier than LW chicks regardless of treatment. On day 5 and thereafter, chicks given a choice were heavier than those eating mash. HW chicks ate more than LW ones. The percentage of yolk eaten increased during the 2-3 d after hatch, remained constant for 2 d, then decreased. Results are discussed in term of yolk need and development of the gastrointestinal tract in the divergent lines.

Self-selection among diets differing in methionine content by chickens of different lines

Two trials were conducted to compare the ability of chickens from different genetic lines to select among diets differing in methionine. In Trial 1, chicks from White Plymouth Rock (HW) and White Leghorn (HA) lines were offered a choice of diets containing .85, .58, or .44% methionine from 1 through 7 days of age. In Trial 2, a slow-growing line of White Plymouth Rocks (LW) was used in addition to the same lines used in Trial 1. A choice of the three diets was offered from 1 through 13 and from 20 through 23 days of age. During the period from 14 through 19 days of age, all chicks were fed the .44% methionine diet. In both trials, Line HW chicks first exhibited a dietary preference at 5 days of age. Line HA chicks did not discriminate among diets in either trial when given a choice from 1 day posthatch. They did, however, exhibit a preference starting on Day 20 in Trial 2 (after being fed the deficient diet). No dietary preferences were exhibited by chicks from Line LW. Results of these trials showed that selection among diets varying in methionine content was influenced by genotype, age, nutritional state of the chick, and their interactions.

Feed intake adjustments by hens to feeding regimens in which dietary methionine is varied

At 20 wk of age, 315 ISA Brown pullets were individually caged and randomly assigned to one of seven feeding regimens for the next 20 wk. In Regimen 1 Diet A was fed, in Regimen 2 Diet B was fed, Regimens 3 and 4 alternated Diets A and B weekly (the week Diet A was fed in Regimen 3, Diet B was fed in Regimen 4), Regimens 5 and 6 alternated Diets A and B monthly (reversing as with 3 and 4), and in Regimen 7 pullets were given a choice of Diets A and B. Diet A was methionine-deficient (.23%) and Diet B was balanced for methionine (.33%). Feed and nutrient consumption, egg production, egg weight, and egg mass were lower in Regimen 1 than 2. Pullets in Regimen 1 lost body weight and those in Regimen 2 gained weight. Overall feed consumption for Regimens 3 through 7 was similar to that for Regimen 2. For Regimens 3 through 6, however, consumption increased when the balanced diet was fed and decreased when the deficient diet was fed. Concomitant with these oscillations in feed consumption were changes in egg mass, so that means for these traits were intermediate and different from those for Regimens 1 and 2. For Regimen 7, in which Diets A and B were continuously available, no preference of diet was observed during the first 4 wk.(ABSTRACT TRUNCATED AT 250 WORDS)

Intestinal 5'deiodinase activity of developing and adult chickens selected for high and low body weight

Intestinal 5'deiodinase activity (5'D) in adults from lines of chickens selected for high (HW) and low (LW) juvenile body weight was studied in vitro using reverse T3 substrate. This avian intestinal 5'D activity is similar in its biochemical characteristics to the hepatic 5'D activity of mammals and birds. Adult 5'D activity was higher in line HW than LW; a pattern opposite to that prior to hatching. Previous studies have shown that thyroid hormones are important in triggering differentiation of the intestine during the latter part of embryonic life. Our studies indicate that the intestinal tissue is capable of producing T3 that may be important in stimulating differentiation of the intestine itself, in preparation for posthatching food assimilation. The intestines of LW embryos, which hatch earlier than HW embryos, show both more rapid maturation, as indicated by intestinal alkaline phosphatase activity (a marker of differentiation), and higher 5'D activity. Increases in intestinal 5'D in the HW line at hatch may be important in the differential intestinal growth that leads to higher relative intestinal weights in HW than LW chicks after hatch. The magnitude of 5'D activity and the relative size of the intestine suggest that this organ could be an important contributor to plasma T3.

Food intake adjustments of chicks: short term reactions to deficiencies in lysine, methionine and tryptophan

1. Two experiments were conducted to compare food intake responses of broiler chicks fed diets varying in lysine, methionine, and tryptophan. Diet D was formulated to create simultaneous deficiencies of lysine, methionine, and tryptophan. Diet A matched National Research Council (1984) recommendations for broilers, and diets B and C were, respectively, 2:1 and 1:2 mixes of diets A and D. 2. Short-term food intake can provide information on the sequences of adaptation of chicks to a diet deficient in essential amino acids. 3. Chicks consumed 26% less of diet D than A during the first 24 h posthatch. When chicks fed diet A or D to 7 d of age were then fed one of 4 diets singly, within 24 h intake was lowest for chicks fed diet D. Within 48 h, food intake of diet C was more than that of diet D and less than that of diet A, while for diet B intake was more than of diet D but not different from diet A. 4. In the second experiment, chicks were fed diet A to 8 d and then diets A or D alone or given a choice of diets A and D from 8 to 20 d of age. Within 4 to 8 h, food intake of chicks fed diet D alone decreased markedly followed by partial recovery within 24 h. In a choice setting, consistent preference of Diet A over Diet D was observed within 7 h followed by stabilisation at about 65% diet A to 35% diet D. 5. Chicks fed diet D alone from 8 to 20 d of age, then placed in the same choice situation preferred diet A to D with a delay of less than one h and stabilisation at about 85%. Chicks provided a choice of diets A and D from 8 to 20 d, and then diet D alone reduced their food intake more quickly than those not given a choice initially. 6. Broiler chicks appear to react to amino acid deficiencies within a short period (hours) by adjusting their feed intake and/or selection. The response is influenced by age and prior experience.

Responses of dwarf and normal chickens to feed restriction, Eimeria tenella infection, and sheep red blood cell antigen

Relationships among stress responses, habituation to feed restriction, resistance to Eimeria tenella, and antibody response to SRBC were studied in dwarf and normal White Plymouth Rocks. Transfer of chicks at 22 days of age from starter to developer batteries resulted in an increase within 24 h of heterophil:lymphocyte (H:L) ratios of chicks of both genotypes. Restriction of feed intake from ad libitum (AL) to 60% of ad libitum reduced body weight and increased size of the crop-esophagus. As measured by H:L ratios, the effect of adapting to the 60% feed restriction dissipated between 12 and 16 days after initiation. Release of 60% restricted chicks to 80% of ad libitum also elicited a stress response as measured by H:L. These effects were noted in both dwarf and normal chicks. Time required for chicks on restriction to consume their daily allotment was curvilinear with a plateau occurring at a smaller value for dwarf than for normal chicks. Neither feeding regimen nor genotype had an effect on antibody response to SRBC. Resistance to E. tenella was greater in normal than dwarf chicks and greater for restricted than ad libitum chicks.

Food intake adjustments of chicks: short term reactions of genetic stocks to deficiencies in lysine, methionine or tryptophan

1. Growth, food intake, and food preference were measured in two experimental lines (White Rocks and White Leghorns) of chickens fed diets varying in content of lysine, methionine, or tryptophan. Diet A was balanced in all amino acids, while the remaining 6 diets were moderately (approximately 30%) or slightly (approximately 15%) deficient in either lysine, methionine, or tryptophan relative to NRC recommendations for broiler diets. 2. Body weight and food utilisation efficiency of White Leghorns at 10 d of age were not affected by diet, whereas the lower concentrations of lysine and methionine depressed these traits in White Rocks. 3. Tryptophan deficiency reduced food intake of White Leghorns, but not White Rocks. 4. With choice feeding of balanced and deficient diets from day 10 to 16, preferences between the diets were minimal for White Leghorns, whereas for White Rocks there was an almost immediate preference for the balanced diet, followed by lack of preference or preference for the deficient diet. 5. Apparently for some genetic stocks there is rapid adjustment to deficiencies in these amino acids with overconsumption, followed by compensation for preference of the balanced diet. The response, however, will vary depending on the deficient amino acid.

Perinatal thyroid hormones and hepatic 5'deiodinase in relation to hatching time in weight-selected lines of chickens

Plasma thyroid hormone concentrations, liver weight, body weight, and hepatic capability for triiodothyronine (T3) production were measured at 8-h intervals on Days 19 through 21 in embryos and chicks from lines selected for high (HW) and low (LW) body weight at 8 wk of age. Embryos were categorized as not having entered the perinatal period (nonpipped, NP) or as being in one of three perinatal stages: embryos that had pipped into the air cell (AC), embryos pipped through the shell (TS), and chicks within 24 h of hatching (H). Both plasma thyroxine (T4) and T3 peaked at the TS stage in embryos of both lines. Embryos had higher concentrations of both hormones and hatched earlier in the LW than in the HW line. This association and evidence from other studies is suggestive that T3 may be playing a role in line differences in hatching time. Hepatic 5'deiodinase (5'D) activity was higher in LW than HW embryos and chicks at the AC, TS, and H stages although the opposite had been the case prior to the perinatal period (NP stage). Hepatic 5'D increased at each stage from AC to TS to H. When the patterns of liver growth and body weight were considered, this pattern and the differences between the lines were exaggerated further. Comparison of the plasma and 5'D patterns during the perinatal period suggests that substrate (T4) supply may be more important than 5'D capability of the liver in determining the pattern of T3 supply during some of these stages.

Differences between genetic stocks of chickens in response to acute and delayed effects of an organophosphorus compound

The influence of genotypes of the major histocompatibility complex (MHC) on susceptibility to acute and delayed effects of an organophosphorus ester was measured in adult White Leghorn chickens from lines differing in response to sheep red blood cell (SRBC) antigen. Chickens from lines selected for high (HA) or low (LA) antibody response to SRBC and homozygous for B13B13 or B21B21 genotypes at the MHC were administered a single subcutaneous injection of diisopropyl phosphorofluoridate (DFP) at dosages of 0, 0.25, 0.50, or 1.0 mg/kg body weight using corn oil as the carrier. Criteria for toxicological responses included clinical, biochemical, and pathological measures. Clinical signs of acute cholinergic poisoning and delayed neuropathy were dose related. Brain and blood cholinesterase and carboxylesterase activities were more sensitive to inhibition by DFP than were liver cholinesterase and carboxylesterase activities. Cholinergic signs 3 h after administration of DFP were more pronounced in line HA than in line LA chickens. Pathological evidence of delayed neuropathy 2 wk after DFP administration was also more evident in HA than LA chickens. Although less pronounced than that for lines, differences in neurotoxic manifestations following DFP administration were greater for chickens of B21B21 than B13B13 genotypes. Activity of A-esterases, which hydrolyze organophosphorus esters without being inhibited by them, was lower in plasma of line HA than line LA chickens. Differences among the genotypes in activity of other esterases were not found in chickens not receiving DFP. These results indicated that responses of chickens to the neurotoxicant DFP were influenced by the background genome of the chickens.

Cellular defense of the avian respiratory system: dose-response relationship and duration of response in intratracheal stimulation of avian respiratory phagocytes by a Pasteurella multocida bacterin

In experiments analyzing dose-response, intratracheal inoculation of chickens with 10(8) and 10(9) avirulent Pasteurella multocida organisms induced the migration within 24 hr of large numbers of respiratory lavage cells (RLC) with increased phagocytic proportions and phagocytic capacity. Doses from 10(4) to 10(7) organisms per bird resulted in elevated numbers of RLCs that were not significantly higher (P > 0.05) than values of uninoculated or mock-inoculated control chickens. When analyzing the duration of response, we found that inoculation with 10(9) organisms resulted in significantly higher (P < 0.05) numbers of RLCs for 63 to 89 hr without significant elevation in phagocytic proportion and capacity. The numbers of RLCs were elevated, although not significantly (P > 0.05), up to 11 days after inoculation. These results indicate that RLCs migrate to the respiratory tract only in response to a relatively high number of stimulating bacterial organisms and that the duration of response is relatively short. Although there were elevated numbers of RLCs beyond 89 hours after stimulation, the question remains as to whether these cells would enhance nonspecific defense of the respiratory system of chickens.

Research note: resistance of chickens to an outbreak of necrotic enteritis as influenced by major histocompatibility genotype and background genome

An outbreak of necrotic enteritis occurred in chickens that were B13B13 or B21B21 at the MHC in sublines of lines selected for high (HA) and low (LA) antibody response to sheep erythrocytes. Percentage mortality and hen-day egg production, although similar for both background genomes, were different for MHC genotypes. Mortality was 6% for B21B21 and 15% for B13B13 types. Although hen-day egg production for both types declined from about 76 to 50%, the decrease occurred earlier but recovery of survivors was faster in B13B13 than in B21B21 pullets.

Evaluating linkage between DNA fingerprint bands and quantitative traits in chickens: interactions

This study assessed the influence of background genome on expression of genes linked to DNA fingerprint (DFP) bands in chickens. Two experimental lines of White Plymouth Rocks previously selected for high or low 8-wk body weight were crossed to produce two F1 males that served as heads of two sire families. Each of these sires was mated to three hens from an unrelated White Leghorn population to produce progeny in which quantitative traits of 4-, 8-, and 12-wk body weight and shank length at 12 wk were measured. The DFP patterns were produced for all individuals in the study. For the 12 sire-specific DFP bands (common to both F1 sires but not found in the dams), each offspring was classified as having or not having each band. Then, an analysis of variance was conducted for each DFP sire band with sex, hatch, dam family, and presence or absence of the sire band as main effects. Interactions between dam family and presence or absence of sire band were also tested. Of 48 possible analyses of variance (12 sire bands by 4 quantitative traits), 3 resulted in significant effects due to sire band, and 2 indicated significant interactions. Thus, associations of a DFP band and a gene coding for a quantitative trait were present, but, in some cases, the expression of the trait differed, depending on the dam family in which it occurred. These data suggest that associations between DFP bands and quantitative traits may not be consistent in different genetic backgrounds.

Antibody responses to combinations of antigens in white Leghorn chickens of different background genomes and major histocompatibility complex genotypes

Antibody responses in chickens to SRBC, Newcastle disease (NDV), and Brucella abortus (BA) were compared when given singly or in combination. Chickens used in the present experiment originated from a cross and then backcrossing of White Leghorn populations that had been selected for high (HA) or low (LA) antibody response to SRBC antigens. The populations used in the current study were segregating for MHC haplotypes B13 and B21. The experiment had a 2 x 3 x 6 factorial arrangement of treatments (two background genomes: HA and LA; three MHC haplotypes: B13B13, B13B21, and B21B21; and six antigen treatments: SRBC, NDV, or BA only, SRBC plus NDV, SRBC plus BA, and NDV plus BA). Antigens were administered either i.v. (SRBC) or i.m. (NDV and BA) when chicks were 42 days of age. Blood was obtained 27 days later (69 days of age) for antibody determinations. A significant background genome by MHC haplotype interaction for BA antibodies was due to relatively high titers in Line HA chickens of MHC genotypes B13B13 and B13B21. Background genome by MHC genotype interactions were not significant for SRBC or NDV antibodies. Antibody titers to SRBC were higher in background genome HA than LA, and similar among MHC genotypes. Antibodies to NDV were lower in chickens of MHC genotype B21B21, but there were no differences due to background genome. For each of the three antigens, antibody responses were highest when administered singly rather than in combination. Antibody titers were lower for SRBC when given with BA, and for BA titers when given with NDV.(ABSTRACT TRUNCATED AT 250 WORDS)

Selection for body weight at eight weeks of age. 20. Production traits and the B and C alloantigen systems

The current study evaluated influence of genotypes of the B and C alloantigen systems on production traits in lines of White Plymouth Rock chickens. Lines had been selected previously for high (HWS) or low (LWS) 8-wk BW and after 27 generations of selection, a random sample of each selected line was used to initiate subpopulations in which selection was relaxed. For the present study, blood typing was used to identify allelic frequencies for the B and C systems for five consecutive generations of selection (Generations 30 through 34) and three consecutive generations of relaxation (Generations 5 through 7). Haplotypes for the B complex were assigned designations B32, B33, B34, and B35 and alleles of the C system were assigned C8, C9, C10, and C11. Production traits for males were BW at 4 and 8 wk of age, and for females were BW at 4, 8, and 38 wk of age, age and BW at production of first egg, percentage of normal eggs, and percentage of normal hen-day egg production. There were no differences in production traits among B genotypes or among C genotypes, although some time trends in gene frequencies suggested that more subtle effects may be present.