Deoxyribonucleic acid fingerprint bands linked to loci coding for quantitative traits in chickens

Efficacy of DNA fingerprint (DFP) bands in marker-assisted selection programs for quantitative traits in chickens was evaluated. A cross between two populations of White Plymouth Rock chickens that had been selected for 31 generations for high (HW) or low (LW) 8-wk body weight served as the base population for the experiment. Full- and half-sib families were produced over four generations and 400 offspring were measured for body weight at 8 wk (BW8) and shank length at 12 wk of age (SL12). Distributions were constructed for each quantitative trait in offspring of one F1 sire. The DFP produced from mixed blood of the individuals within each tail of the distribution were compared. From a total of 13 DFP bands that were disparate in intensity between the tails, four bands were chosen for analysis. Matings were made between males and females based on the presence or absence of these bands, but were limited to individuals that were within .5 standard deviation of the mean for the distribution of a particular trait. Quantitative traits of the resulting progeny were analyzed to determine whether parental type (presence or absence of the DFP band) influenced expression of the trait in the offspring. One band out of the four tested was associated with SL12, was an effective predictor of phenotype for both SL12 and BW8, and appeared to be inherited in a dominant fashion.

Correlated responses in lines of chickens divergently selected for fifty-six-day body weight. 2. Organ growth, deoxyribonucleic acid, ribonucleic acid, and protein content

Growth of organs relative to body weight and cellular protein, RNA, DNA, and cell unit size of breast muscle, liver, and small intestinal tissue were measured in females from four lines of chickens. Two lines had undergone 32 generations of divergent selection for 56-day body weight, and the other two lines were derived by sampling the first two lines at Generation 28 and relaxing selection for the next five generations. The diet used in the present experiment was the same diet under which selection was practiced (20% crude protein and 2,685 kcal of ME/kg). Comparisons at common chronological ages and a common body weight revealed that supply organ weights, especially that of the small intestine, were associated with subsequent growth of demand organs. Although the upper gastrointestinal tract was also important in this respect, it was more susceptible to influences such as feed intake. Selection for juvenile body weight resulted in correlated changes in cell size of breast muscle but not liver and small intestine. Muscle increased posthatch as cells underwent hypertrophy but liver and small intestine grew chiefly by hyperplasia.

Correlated responses in lines of chickens divergently selected for fifty-six-day body weight. 3. Digestive enzymes

Levels of amylase, trypsin, chymotrypsin, and lipase in the pancreas and small intestinal chyme were measured in females from four lines of chickens. Two of the lines had undergone 32 generations of divergent selection for 56-day body weight, and in the other two lines selection for high or low weight had been relaxed for 5 generations. The diet used in the present experiment was that under which selection had been practiced (20% crude protein and 2,685 kcal of ME/kg). Comparisons between divergently selected lines at common ages revealed higher enzyme levels for high- than low-weight lines. When comparisons were made at a common body weight (80 +/- 5 g) there were no differences between lines. These results suggested that correlated responses in feed intake were mediating the regulation of digestive enzyme levels in the pancreas and in intestinal chyme of growth-selected lines of chickens. Chicks from high-weight lines had elevated enzyme levels after a mild feed restriction compared with those provided ad libitum access to feed. It was hypothesized that hyperphagia associated with the high-weight lines in combination with a mild feed restriction and the associated meal feeding stimulated synthesis and secretion of digestive enzymes.

Correlated responses in lines of chickens divergently selected for fifty-six-day body weight. 1. Growth, feed intake, and feed utilization

Correlated responses for growth, feed intake, and feed utilization were measured in female chickens from lines after 32 generations of divergent selection for 56-day body weight and in sublines in which selection had been relaxed for five generations. The diet used in the present experiment was that under which selection had been practiced (20% crude protein and 2,685 kcal of ME/kg). Feed intake between each selected line and its relaxed subline was equalized by paired-feeding. Ad libitum-fed controls were also maintained. At 21 days of age, differences between the selected lines for ad libitum-fed chickens were 404% for body weight, 279% for feed intake, and 138% for feed conversion ratio (FCR). Respective percentages for the high and low relaxed lines under ad libitum feeding were 267, 223, and 121%. When pair-fed, the growth of the line selected for high weight was unimpeded and FCR improved. When chicks of the low-weight relaxed line were pair-fed, FCR also improved, but growth was reduced and appetite development inhibited. Hyperphagic behavior was observed in the line selected for high weight. In the low-weight selected line, the chicks exhibited hypophagia. Although residual feed consumption was unchanged by selection for 56-day body weight, variation was present for this trait, with lower values under restricted than ad libitum feeding.

Restricted feeding and broiler performance: age at initiation and length of restriction

Broiler cockerels were provided either ad libitum access or restricted to alternate-day access to feed initiated at different ages and lasting for different durations. Regimens consisted of ad libitum feeding; alternate-day feeding; alternate-day feeding from 0 to 6, 6 to 12, or 12 to 18 days of age (DOA); alternate-day feeding from 0 to 12, 0 to 6, and 12 to 18, or 6 to 18 DOA; and alternate-day feeding from 0 to 18 DOA. By 39 DOA, chicks restricted for only one 6-day period reached body weights equivalent to those of chicks eating ad libitum. Body weights of chicks restricted for more than 6 days during the first 18 days after hatch were lower than those of chicks eating ad libitum at 39 DOA. Restriction for more than 6 days improved feed efficiency. Chicks restricted for the whole experiment had superior feed efficiency but low body weights. Antibody responses to sheep erythrocyte antigen were similar among feeding regimens. Response to Escherichia coli inoculation was generally less severe in chicks provided restricted access to feed, and overall mortality was highest in chicks eating ad libitum. Feeding regimens had little effect on organ weights relative to body weight, amount of abdominal fat (either on an absolute basis or relative to body weight), or percentage lipid in the abdominal fat pad.

Inheritance of antibody response to sheep erythrocytes in lines of chickens divergently selected for fifty-six-day body weight and their crosses

Experiments were conducted to determine the principal mode of inheritance for antibody response to SRBC in selected populations of chickens and their crosses. Additive genetic variation was important in the inheritance of both primary and secondary responses to this antigen. Reciprocal differences and heterosis also influenced the secondary response. Kinetics of primary and secondary antibody responses were evaluated in pairs of lines divergently selected for high (HW) or low (LW) juvenile body weight and high (HA) or low (LA) response to SRBC antigen. Different groups of chickens were sampled on Days 3 to 7, 10, 14, 24, 26, 28, and 31 postprimary inoculation (PPI). Half of the chickens sampled after Day 14 received an additional injection of SRBC antigen. Plasma from each individual was examined for total, mercaptoethanol-resistant, and mercaptoethanol-sensitive titers. Antibody titers PPI to SRBC were consistently highest in Line HA and lowest in Line LA. Lines HW and LW reacted similarly to Line LA early in response, but showed higher levels later. In both primary and secondary responses, the weight lines peaked at similar levels. Thereafter, Line LW maintained a higher antibody titer level to SRBC antigen than Line HW.

Response to Eimeria tenella of chickens selected for high or low antibody response and differing in haplotypes at the major histocompatibility complex

Sublines of chickens selected for high antibody (HA) or low antibody (LA) response that differed at the major histocompatibility complex (MHC) were tested for response to Eimeria tenella. In Expt. 1, the first exposure to E. tenella was natural (in floor pens), and chicks were challenged orally 21 days later with 0, 928, or 1855 oocysts. In Expt. 2, chicks were reared in wire-floored batteries, vaccinated orally with 928 oocysts, and challenged orally 12 days later with 15,844 oocysts. Corticosterone (20 mg/kg) was mixed with feed from 24 hr before vaccination to 120 hr after vaccination in Expt. 2. In Expt. 1, LA chicks had more-severe cecal lesions but gained relatively more body weight after challenge than did HA chicks. In Expt. 2, cecal lesions were least severe in HA chicks that had been fed corticosterone, most severe in LA chicks fed corticosterone, and intermediate in chicks that were not fed corticosterone. No differences in response to E. tenella occurred as a result of haplotypes at the MHC.

Reaction of the avian respiratory system to intratracheally administered avirulent Salmonella typhimurium

Chickens were inoculated intratracheally (IT) with the SR-11 Salmonella typhimurium deletion mutant x4062 strain. Data collected for 8 days postinoculation (PI) were: signs of respiratory and gastrointestinal disease; histological lesions; the influx, phagocytic proportion, and phagocytic capacity of avian respiratory phagocytes (ARPs); and the proportion of granulocytes vs. macrophages in the lung tissues and lavage fluids of the lungs and air sacs. S. typhimurium-inoculated chickens had no clinical signs of gastrointestinal or respiratory disease but had various degrees of inflammatory changes in the lungs. At 5 hr PI, S. typhimurium-inoculated chickens had approximately 53-fold more ARPs than mock-inoculated controls. Between 26 hr and 8 days PI, the number of ARPs from S. typhimurium-inoculated birds was not significantly higher than the number from the mock-inoculated controls. Flow cytometric analysis of ARPs demonstrated that the proportion of phagocytic ARPs and the phagocytic capacity of ARPs from S. typhimurium-inoculated chickens were significantly higher between 5 and 26 hr PI than those of the ARPs from mock-inoculated chickens. Kinetic changes over 8 days in the granulocyte/macrophage ratios in the lavage fluids, as compared with kinetic changes in the lung tissues, suggested that the granulocytes generally represent a much higher proportion of the ARPs, and egress earlier and in much larger numbers from the tissues to the lumen of lungs and air sacs than do macrophages.

Performance of early and late feathering broiler breeder females with different feeding regimens

1. Growth, reproductive characteristics and immunocompetence were evaluated in a line of broiler breeder females segregating at the sex-linked feathering locus when maintained on three feeding regimens with two forms of food in a factorial design. 2. Long-term obesity but not short-term weight gain had deleterious consequences for reproductive characteristics, response to sheep red blood cell antigen, resistance to Escherichia coli and livability. 3. Reproductive performance of early feathering females was superior to that of late feathering ones. Differences were attributed to an association between the allele for late feathering and an endogenous viral locus ev21, which encodes for avian leucosis virus. 4. Reproductive performance of breeders fed crumbles was superior to that of breeders fed a combination of crumbles and fines.

Organ growth and digestive enzyme levels to fifteen days of age in lines of chickens differing in body weight

Weights of internal organs and levels of digestive enzymes were obtained through the first 15 days posthatch for cockerels from three lines of chickens known to differ greatly in body weight. On Day 15 body weights from the fastest growing line were eight times greater than those from the slowest growing line. Differences among lines were found for weights at hatching and for growth patterns (both absolute and relative to body weight) of the vitelline residue, heart, lungs, liver, pancreas, crop, proventriculus, gizzard, and segments of the small intestine. Line differences were also evident for levels of trypsin, chymotrypsin, and amylase in the pancreas and contents of the small intestine. Ranking of lines for these traits varied with age. In all lines weights of the small intestine, liver, and pancreas increased relatively more than did total body weight during the 1st wk posthatch, after which the relationship reversed.

Relationships among age of dam, egg components, embryo lipid transfer, and hatchability of broiler breeder eggs

Fertility, hatchability, and their relationships to age of dam, egg components, embryo growth, and embryo lipid transfer were studied in a broiler breeder line segregating at the sex-linked feathering locus. Early-season increases in hatchability of eggs were due to a reduction in embryo deaths between Day 1 and 7 of incubation. No late seasonal declines in either fertility or hatchability were observed. Although less proficient in young dams, embryo lipid transfer was not directly associated with the lower hatchability of their eggs. Egg weight, weights of 18-day embryos, and embryo:egg ratios increased with parental age. Also with age, there were increases in shell, albumen, and yolk weights. Heavier albumen weight was due to increased moisture content, and those for shell and yolk were due to dry matter accumulation. Changes in yolk:albumen ratios reflected large increases in relative yolk weight, on a wet and dry weight basis, that were associated with age of dam. Eggs from late-feathering dams were heavier than those from early-feathering ones. Heavier embryos by 18 days of incubation were attributed to the transfer of albumen from the egg to the embryo.

Escherichia coli challenge in chickens selected for high or low antibody response and differing in haplotypes at the major histocompatibility complex

Relative sensitivity to Escherichia coli challenge was evaluated in white leg-horn chickens that had been selected for high antibody (HA) or low antibody (LA) response and that differed in haplotypes at the major histocompatibility complex (MHC). Assessments were made of relative body-weight change and of heart and air-sac lesions after inoculation of 10(6), 10(5), or 10(4) E. coli via the posterior thoracic air sac. As has previously been reported, chicks from line HA were more sensitive to E. coli than those from line LA. Lesion scores were 1.58 +/- 0.12 in line HA and 1.02 +/- 0.12 in line LA (mean +/- S.E.), and ranged from 0.99 +/- 0.14 with the lowest dose of E. coli to 1.79 +/- 0.15 for the highest dose. Relative body-weight change to 72 hours after inoculation was greater in line LA (7.5 +/- 0.5) than in line HA (4.4 +/- 0.8). There was no apparent resistance or susceptibility conferred to chickens in either the HA or LA genetic background as a result of haplotypes present at the MHC.

Hepatic 5'-deiodination in chickens from lines selected for high and low body weight and their F1 cross

1. Assay conditions for measuring hepatic 5'-deiodinase (5'D) activity at initial velocity, using reverse T3 as substrate, have been validated for adult chicken liver. 2. The characteristics of hepatic 5'D activity in adult chickens from lines selected for high (HW) and low (LW) juvenile body weight are similar to those in mammals and in the other birds that have been investigated. 3. Chickens from the HW line have significantly higher specific activity of hepatic 5'D, and thus potentially higher T3 production, than those from either the LW line or the F1 cross (HL) between the HW and LW lines.

Research note: T-cell activity of White Leghorn chickens selected for high and low antibody responses to sheep erythrocytes

Mitogen responses of peripheral blood lymphocytes (PBL) and the cell cycle analysis of T-cells were examined for lines of chickens selected for high (HA) and low (LA) antibody response to SRBC. At 6 wk of age, within each line, blood samples and thymic tissue were collected from chicks representing the B13B13, B13B21, B21B13, and B21B21 genotypes. Although no influence of Ea-B haplotype on T-cell activity was detected in either line, there were line differences in phytohemagglutin-M (PHA-M) and concanavalin A (Con A) mitogen responses and the percentage G0/G1 and S phase T-cells. The HA PBL had greater in vitro PHA-M and Con A responses, and the cell cycle analysis of T-cells revealed a greater percentage of cells in S phase for Line HA chicks than for LA chicks. There were significantly more resting cells in the G0/G1 phase of LA than HA chicks. Although there was no Ea-B haplotype effect observed on T-cells from either line, generalized selection for high or low antibody response did result in divergent T-cell activity.

Genotype, feeding regimen, and diet interactions in meat chickens. 1. Growth, organ size, and feed utilization

Allomorphic growth of organs and feed utilization were measured in cockerels from two meat lines known to differ in growth potential under alternate-day and daily feeding of diets differing in nutrient density. The faster growing line consumed more feed and utilized feed more efficiently than the slower growing line. Relative weights of heart and all segments of the gastrointestinal tract except the esophagus were smaller in the faster than in the slower growing line whereas breast, thigh, and drumstick were greater for the faster than the slower growing line. These patterns existed regardless of diet. In contrast, line by feeding regimen interactions were noted for most traits; the faster growing line was influenced more by restricted feeding than the slower growing line. Thus, the practice of selecting individuals in a restricted-feeding environment when commercial stocks have feed available to them at all times may be faulty. Although the alternate-day feeding regimen improved feed efficiency, results indicated that full benefit of feed restriction would be realized by feeding a diet higher in nutrient density.

Genotype, feeding regimen, and diet interactions in meat chickens. 2. Feeding behavior

Feeding behaviors were compared for males from two lines of meat chickens differing in growth potential fed lower and higher density diets ad libitum either daily or on alternate days. Males from the faster growing line ate and drank more often but stood and rested less often than those from the slower growing line. Rate of feed intake per unit BW was, however, similar for both lines. Greater crop and lower intestinal contents of the faster growing line suggested a higher feed intake and storage ability. Even though males fed the lower energy diet initially consumed similar amounts of ME on days of food restoration, by 24 h they lagged behind those fed the higher energy diet, suggesting capacity of the gastrointestinal tract (GIT) to be a limiting factor in energy consumption. At older ages, chicks fed the different diets had similar GIT contents, suggesting that excessive eating and less resting observed for males fed the lower density diet contributed to their poorer energy utilization. On the day of feed restoration, males fed on alternate days ate and stood more often and had poorer GIT clearance than those with feed continuously made accessible to them.

Genotype, feeding regimen, and diet interactions in meat chickens. 3. General fitness

Several fitness traits were measured in males from two meat lines fed diets differing in nutrient density ad libitum daily or on alternate days. Criteria of evaluation were antibody response to SRBC, blood heterophil:lymphocyte ratios, incidence of leg deformities, and resistance to Escherichia coli inoculation. Males from the heavier line had lower antibody titers to SRBC inoculation than those of the lighter line. Diets, feeding regimens, and interactions among them did not influence response to SRBC. Lines, diets, feeding regimens, and interactions among them were not significant for heterophil:lymphocyte ratios. Chicks fed daily had a higher incidence of leg deformities than those fed on alternate days. There were no differences between lines or diets, nor were interactions significant. Interactions were present between main variables for response to E. coli inoculation whether the measure was initial weight loss, recovery, or lesion scores, demonstrating the complexity of genotype-environmental relationships in resistance to this infectious agent.

Deoxyribonucleic acid fingerprint comparisons between selected populations of chickens

A pair of lines of White Plymouth Rock chickens selected for high or low juvenile body weight, a pair of White Leghorn chickens selected for high or low antibody response to sheep erythrocytes, and an F1 cross between each pair of lines, were used to produce DNA fingerprints (DFP). These DFP were prepared by mixing equal amounts of DNA from several individuals of a particular population, resulting in a DFP characteristic of the population. The populations provided individuals of known genetic relationships and inbreeding levels to evaluate the sensitivity of the DFP technique with DNA mixing. Levels of band sharing between breeds were lowest, those between selected lines within a breed were intermediate, and those between the selected lines and their F1 crosses were highest. These results show that DFP analysis is sensitive to several levels of genetic relationship.