Free-range village chickens on the Accra Plains, Ghana: their contribution to households.

A cross-sectional survey investigating the contribution of free-range village chickens to household economies was carried out in four administrative districts within 60 km of Accra. Answers were provided by 101 men and 99 women. Nearly all respondents claimed to keep chickens for meat, with a far smaller percentage claiming to keep them for egg production. Over 80% of respondents kept chickens to supplement their incomes. The proportion of the flock eaten varied between administrative areas (p = 0.009 and p = 0.027), although this was possibly a consequence of differences in consumption patterns between occupation of the respondent, land area cultivated and flock size. The proportion of chickens sold varied as a result of differences in flock size (p = 0.013), the proportion sold increasing with number of birds in the flock. Respondents generally agreed that chickens could be sold without difficulty. A majority of chicken sales were from the farm gate, directly to consumers or traders. Sales were on demand or when the owner needed money. Money from the sale was kept by the owner of the chicken and the money was spent on personal needs. The proportion of the flock sold varied between administrative areas (p = 0.025) and occupation of the respondent (p = 0.040). Respondents describing animal production as their main occupation tended to have greater reliance on chicken sales for their income. Consideration is given to estimating the offtake from the flock and the financial contribution to the household.

Free-range village chickens on the Accra Plains, Ghana: their husbandry and productivity.

A cross-sectional[4pc] survey investigating husbandry and productivity of free-range village chickens was carried out in four administrative districts within 60 km of Accra. Responses were provided by 101 men and 99 women. The mean (SD) household flock size was 28.7 (25.97) and the median was 20. The factors included in the final model investigating variance in flock size were sex of the respondent (p = 0.011), administrative area (p = 0.004), the numbers of members in the household (p = 0.017) and the number of cattle, sheep and goats owned by the household (p = 0.031). Chickens were owned by individual members of the household, but women and children were the predominant providers of care for chickens. All respondents described their chickens as scavengers that were provided with supplementary feed, and over 80% of respondents named maize as a supplementary food source. Approximately 50% of respondents claimed difficulty in providing supplementary feed, with the degree of difficulty varying between administrative areas (p < 0.001). A majority of respondents (approximately 65%) claimed that their chickens laid 3-4 clutches of eggs per year. Over 70% of respondents estimated that each clutch contained 10-20 eggs, and approximately 70% of respondents estimated that 75% of the eggs hatched. Opinions on mortality varied, but 60% of men and 70% of women estimated that between 50% and 75% of both chicks and adult birds died each year. Approximately 80% of respondents named Newcastle disease as the most important health issue. The opportunities for and consequences of controlling Newcastle disease are discussed.

Poult performance as influenced by age of dam, genetic line, and dietary vitamin E.

An experiment was conducted to measure the effects of age of dam, genetic line, and dietary levels of vitamin E on growth and immunocompetence of poults. Age of dam was defined as younger (in early egg production) and older (past peak production); line consisted of a commercial sire and dam line; and dietary vitamin E was supplemented into the diet at 10 and 300 IU/kg of feed. Traits measured included body, liver, gizzard, and yolk sac weights at hatch; BW and feed conversion to 9, 28, and 42 d; response to SRBC, Phaseolus vulgaris agglutinin-P, and Escherichia coli administered at 28 d of age; and response to a cold stress on d 5 posthatch. Differences among genetic lines were evident with growth greater for poults from the sire than from the dam line. Performance of poults from older dams was generally superior to that of poults from younger dams. The higher level of vitamin E resulted in a greater than 7-fold increase in blood plasma vitamin E and reduced mortality. There were interactions among the main effects in which the fitness of poults from younger dams was enhanced by the higher level of vitamin E and the effect of breeder age differed among genetic lines.

Memory antibody responses of broiler and leghorn chickens as influenced by dietary vitamin E and route of sheep red blood cell administration.

Influences of dietary levels of vitamin E fed to hens and their progeny, and routes of SRBC inoculation on antibody responses of diverse populations of chickens were studied. Populations were a commercial broiler sire line (C), 2 commercial broiler dam lines (A and B), and Leghorn lines selected for high (H) or low (L) antibody response to SRBC. Dams from lines A and B were fed diets supplemented with either 10 or 300 IU/kg of vitamin E, whereas dams from lines H and L received only the diet with 10 IU of vitamin E/kg. Progeny from matings of C males with A and B females as well as H and L females mated to males from their respective lines were hatched on the same day and fed diets supplemented with either 10 or 300 IU/kg of vitamin E. Breeders were the same age and eggs were incubated in the same machine. Chicks were inoculated on d 14 intravenously with 0.1 mL of a 0.5% suspension of SRBC or intramuscularly with 0.1 mL of a 25% suspension of SRBC. Antibody response was measured 6 and 14 d later. Chicks received a booster i.m. inoculation of 0.1 mL of 25% SRBC on d 28. Titers were again measured 6 and 14 d later. Level of vitamin E fed to dams did not affect progeny BW or plasma vitamin E levels. Although titers were higher following i.v. than i.m. inoculation, the degree of difference varied among stocks. Dietary vitamin E level interacted with inoculation route with a greater response to the higher than lower level of vitamin E for i.v., but there was no difference for i.m. There were stock x level of vitamin E and stock x route of inoculation interactions for secondary responses to SRBC inoculation. Stock rankings after the first inoculation were not predictive of the rankings after the second inoculation. The 30-fold increase in dietary level of vitamin E resulted in >12-fold differences in plasma levels of vitamin E. Overall, there was a stock-dependent influence of dietary vitamin E on growth and humoral antibody response.

Effect of route of inoculation on humoral immune response of White Leghorn chickens selected for high or low antibody response to sheep red blood cells.

Effects of route of SRBC inoculation and antigen dosage on primary and secondary antibody response of White Leghorn lines selected for high (HA) or low (LA) 5-d antibody response to a single i.v. inoculation with 0.1 mL of a 0.25% suspension of SRBC were studied in two trials. In the first trial, chicks from parents of generation S24 of each line were randomly assigned to one of four treatments. At 35 d of age, they were inoculated into the brachial vein with 0.1 mL of 0.25% suspension of SRBC or into the breast muscle with 0.1 mL of 0.25, 2.50, or 25.00% SRBC. Plasma SRBC antibody was measured 3, 6, 10, and 20 d later. In the second trial, chicks from parents of generation S25 of each line were randomly assigned to treatment groups. At 28 d of age they were inoculated with 0.1 mL of 0.25% SRBC into the brachial vein, 0.1 mL of 25.00% SRBC into the thigh (T-L) or breast muscle (B-L), or 0.5 mL of 25.00% SRBC into the thigh (T-H) or breast muscle (B-H). Twenty-one days later, chicks (except five per group) were given a booster inoculation of 0.1 mL of 25.00% SRBC into the thigh muscle. Six and 10 d after each inoculation, plasma SRBC antibody, IgG, and IgM titers were measured. The SRBC antibody titers after primary i.v. inoculation with SRBC were always higher for HA than LA chicks. When inoculations were i.m., differences between lines varied with dosage. Low dosages inoculated into the breast failed to induce line differences consistently, whereas at higher dosages, titers were greater for HA than LA chicks regardless of inoculation site. For Line LA, inoculation into the thigh elicited higher titers than inoculations into the breast. Antibody titers to the booster inoculation of SRBC were similar for the lines.

Antibody responses of hens fed vitamin E and passively acquired antibodies of their chicks.

Antibody responses of hens and their progeny were studied in commercial broiler nuclear lines. Starting at 168 days of age, individually housed pullets from lines A and B were fed a 16% crude protein and 2752 kcal metabolizable energy/kg mash diet supplemented with either 10 or 300 IU/kg of vitamin E fed as dl-alpha-tocopherol acetate. Fifty-eight days later (226 days of age), 12 hens per line-vitamin E subclass were inoculated i.v. with 0.1 ml of a 2.5% suspension of sheep red blood cells (SRBC). Plasma antibody titers were measured 6, 20, 40, 54, 70, and 88 days after inoculation. Hens from both lines were artificially mated to males from line C, and progeny from eggs collected 9-15, 25-30, and 65-70 days after inoculation were tested for antibodies to SRBC. Hens were reinoculated i.v. with 0.1 ml of 0.25% SRBC 88 days after the first inoculation, and their antibody levels were measured 3, 6, and 20 days later. Eggs laid 10-13 days after reinoculation were incubated, and antibody titers of chicks were measured at hatch. Antibody response of hens to an initial inoculation of SRBC was line-diet-time after inoculation specific. In line A, titers were greater for hens fed the lower than the higher vitamin E diet, whereas diet had no effect on the antibody levels in line B. Line effects (A > B) were observed on days 6 and 20 after inoculation but not thereafter. After the second inoculation, dietary vitamin E level had no effect on antibody levels of hens within lines, whereas a between-line difference (A > B) was observed for the lower but not the higher level of dietary vitamin E. Although there was no difference between diets for antibody transferred to progeny by line B, there was a difference (lower > higher) for line A. After reinoculation of their dams, antibody titers of chicks from line A, but not line B, reached levels similar to those after the first inoculation. Antibody levels were higher for chicks at hatch than in 16-day embryos or 10 days posthatch. The results of this research suggest genetic variation in response to immune stimulation by dietary vitamin E.

Vitamin E and immune responses of broiler pureline chickens.

Immunological responses of cockerels fed diets containing either 10 or 300 mg/kg of vitamin E were measured in three commercial broiler nuclear lines designated as A, B, and C. All cockerels were fed the 10 mg/kg diet to 91 d of age, at which time half were continued on that diet and the other half were fed a diet supplemented to contain 300 mg/kg of vitamin E. Sixteen days after feeding the diets, cutaneous basophil hypersensitivity (CBH), which is an in vivo, cell-mediated immune response, was determined as the increase in toe-web skin thickness 24 h after an injection with phytohemagglutinin-P (PHA-P). Twenty-two days after feeding the diets, heterophils and lymphocytes were enumerated. At this time cockerels were also inoculated intravenously with 0.1 mL of 0.25% SRBC. The injection with SRBC was repeated 27 d later. Six and 20 d after each injection, antibody titers were determined. Mercaptoethanol-resistant (IgG) and mercaptoethanol-sensitive (IgM) antibodies were also measured in the secondary titers. The ratio of heterophils to lymphocytes increased, and CBH response was depressed by feeding the higher vitamin E diet. For cockerels of Lines A and B, the higher level of vitamin E maintained primary and secondary SRBC antibody levels, whereas for Line C, levels were depressed. The effect of the higher vitamin E diet on IgG and IgM was also stock-dependent. The enhanced heterophil:lymphocyte ratio from feeding vitamin E suggests an improved phagocytic ability of the immune system. Relative asymmetries for toe-web skin thickness and shank length were similar for the three lines.

Antibody responses to different dosages of sheep red blood cells in lines of chickens selected for high and low antibody response to sheep red blood cells.

Temporal patterns of SRBC antibody response after primary and secondary inoculations were measured in White Leghorn males from lines selected 24 generations for high (HA) or low (LA) 5-d antibody titers to an i.v. inoculation with 0.1 mL of a 0.25% suspension of SRBC. Primary i.v. inoculations were administered at 50 d of age as 0.1 mL of either 0.025 or 0.25% suspension of SRBC. Antibody levels of SRBC were measured 3, 5, 7, 9, 11, 13, and 20 d after inoculation. Also, IgG levels were measured on samples obtained 3, 7, 13, and 20 d after inoculation. At 70 d of age, half of the cockerels in each line-dosage subclass were given a booster inoculation of 0.1 mL of 0.25% SRBC. The SRBC antibody was measured 3, 6, 9, and 13 d later in chicks both receiving and not receiving the second inoculation. Patterns of antibody response to SRBC dosage differed according to line, resulting in interactions of line by dosage by day. Concentrations of IgG were greater for Line HA than for LA at 7 and 11 d after inoculation with SRBC but not at 3 and 20 d. Antibody responses to the booster inoculation differed between lines with a dosage effect present for LA but not for HA chicks. The greater anamnestic response observed in LA than in HA chicks is explained in the context of the resource allocation paradigm.

Diet and immunological memory of lines of White Leghorn chickens divergently selected for antibody response to sheep red blood cells.

Antibody responses to a first, second, and third injection with SRBC, and growth were studied in lines of White Leghorn chickens selected for high (HA) or low (LA) 5-d antibody titers to an i.v. inoculation with 0.1 mL of a 0.25% suspension of SRBC. The experiment involved parallel studies on two groups of chicks hatched from the same matings of parental lines HA and LA at a 14-d interval. Chicks of each age-line subclass were fed either a high or low nutrient density diet from hatch onwards. When chicks of Hatches 1 and 2 were 28 and 14 d of age (doa) respectively, they were injected with 0.1 mL of 0.25% suspension of SRBC, and antibody titers measured 3 and 6 d later. A second and a third injection of the same concentration of SRBC was given to chicks of each age-line-diet subclass at 10-d intervals and antibody titers measured 3 and 6 d after each injection in different chicks randomly sampled from each age-line-diet subclass. After the first injection, antibody (primary) responses of HA chicks were higher than those of LA chicks regardless of age and diet. This difference (HA > LA) observed for the primary response was seldom evident in the responses to the second (secondary) and third (tertiary) injections. Antibody responses of LA chicks after the second and third injections were anamnestic. For HA chicks given the first injection at 28 doa, neither the secondary nor tertiary responses suggested anamnestic capacities, whereas there was apparent memory exhibited by the secondary and tertiary responses of HA chicks initially injected at 14 doa. The LA chicks were significantly heavier than HA chicks at all ages. Even though the higher nutrient density diet increased BW of chicks of both lines, its effect on memory responses was sporadic. The results of this experiment show that, even though divergent selection has been successful in the primary responses, correlated responses in immunological memory were not always observed, suggesting that the two types of responses might be under different genetic control.

Immunocompetence and resistance to marble spleen disease of broiler- and layer-type pure lines of chickens.

The intent of this study was to evaluate, under concurrent conditions, certain responses that may be important in chicken breeding and growing. Three commercial broiler pure lines (A, B, and C) and two experimental White Leghorn lines selected for high (HAS) and low (LAS) antibody response to sheep red blood cells were evaluated concurrently for humoral and cell-mediated immunocompetence, resistance to marble spleen disease virus (MSDV), relative asymmetry (RA), and comb weight. Chicks were injected with 0.1 ml of 0.25% SRBC at 21 days of age. Antibody response 6 days after injection was highest in line HAS. Titres for the commercial lines were similar to those in line LAS. The cutaneous basophil hypersensitivity test, an in vivo cell-mediated immune response, was measured as the increase in toe-web thickness 24 h after an injection with T-cell mitogen phytohaemagglutinin (PHA)-P or -M into a sample of chicks at 9 days of age and a different sample of chicks at 20 days of age. PHA-P elicited greater responses than PHA-M at both ages. The pattern among stocks, however, differed depending upon age. Responses at 9 days were greater for the Leghorn than broiler lines, while at 20 days, responses were greater in lines A and LAS than in lines B, C, and HAS. Resistance to MSDV challenge differed among stocks, with the ranking for resistance being C>(A=B=LAS)>HAS. Rankings of RA for normal thickness of the toe web between the third and fourth digits at 9 days of age were (HAS=LAS)>(A=B=C). There were no differences in RA among stocks at 20 days of age. There was a significant line by sex interaction for relative comb weight, due to differences between lines for males but not females. Data from this study suggest that competence in one arm of the immune system is not a reliable measure of general immunocompetence, nor is it a measure of resistance in general.

Diet and humoral responsiveness of lines of chickens divergently selected for antibody response to sheep red blood cells.

Growth and humoral immune response were studied in lines of white leghorn chickens selected for high (HA) or low (LA) 5-day antibody titers to an i.v. inoculation with 0.1 ml of a 0.25% suspension of sheep red blood cells (SRBC) antigen(s). Chicks were fed either a high (E) or low (A) nutrient density diet from hatch onward. Chicks from each line-diet subclass were inoculated i.v. with 0.1 ml of either 0.25% or 2.50% suspension of SRBC at either 7, 14, 21, or 28 days of age. Antibody titers were measured 5, 10, and 20 days after inoculation. LA chicks were heavier than HA chicks at 7 days of age and thereafter. Chicks fed diet E were heavier than those fed diet A. Feed efficiency was influenced by diet (E > A) at 21 and 28 days of age and line (LA > HA) at 28 days of age. In all but one case, antibody titers to SRBC were higher in HA than LA chicks. Also, the frequency of nonresponders of chicks inoculated with SRBC at 7 days of age was higher for LA than HA chicks. The higher dosage elicited greater 5-day antibody responses in LA but not in HA chicks inoculated at 28 days of age. Dietary effects on SRBC antibody were generally unimportant except for occasional interactions of dosage and line.

Mode of inheritance of unselected traits in lines of chickens selected for high or low antibody response to sheep red blood cells. 1. Resistance to marble spleen disease virus and juvenile body weight.

Two lines of White Leghorns that had undergone long-term selection for high (HH) or low (LL) antibody response to sheep red blood cell antigen(s) formed the nuclear lines for this experiment. Matings were made in a full diallel cross to produce in a single hatch from age-contemporary breeders the parental lines, reciprocal F1 and F2 crosses, and backcrosses for 16 progeny types. For males and females, there were parental line differences in BW to 42 d of age, after which there was decline between lines for males. Differences in BW between reciprocal F1 crosses and maternal heterosis declined with age, primarily reflecting dissipation of effects of egg weight. Heterosis of BW was dependent on the particular F1 cross and recombination effects were not important. At 50 d of age chicks were inoculated with either a 1 or 10% suspension of spleen extract from chickens infected with marble spleen disease virus (MSDV). A third group served as uninjected controls. Response to MSDV was evaluated by spleen weight 6 d after inoculation. Spleen weights relative to BW of control chicks were heavier for the HH than LL line with evidence from the crosses of sexlinkage and negative heterosis. Line LL chicks were more resistant to MSDV than Line HH chicks was F1 crosses intermediate to and different from either parental line with no evidence of heterosis.

Mode of inheritance of unselected traits in lines of chickens selected for high or low antibody response to sheep red blood cells. 2. Heterophils, lymphocytes, and hematocrits.

The nuclear lines for this experiment were White Leghorns that had undergone long-term selection for high (HH) or low (LL) antibody response to sheep red blood cell antigen(s). Sixteen progeny types consisting of parental lines, reciprocal F1 and F2 crosses, and backcrosses were produced in a single hatch from age-contemporary parents. At 30 d of age, blood was obtained from a random sample of 10 males per progeny type (n = 160) and slides prepared for subsequent determination of number of heterophils and lymphocytes. Twelve days later, blood was collected from random samples of 10 males and 10 females per progeny type (n = 320) for measuring hematocrits. There were no differences between parental lines for heterophils, lymphocytes, or the heterophil:lymphocyte ratio. Reciprocal effects were evident in the F1 crosses and directional heterosis was present in one cross but not the other. Neither maternal heterosis nor recombination effects were significant for either heterophils or lymphocytes. Although hematocrits were similar for males and females and parental lines, sex-linked and recombination effects appeared to be important.

Genetic architecture of antibody responses of chickens to sheep red blood cells.

SUMMARY: Two lines of White Leghorn chickens selected divergently for high (HH) or low (LL) antibody response 5 days after an injection with 0.1 ml of 0.25% suspension of sheep red blood cell (SRBC) antigen were used to produce parental, reciprocal F(1) , F(2) and backcross progeny. At 36 days of age males and females of the various progeny types were injected with SRBC suspension and antibody titres measured at 5 and 12 days later. Progeny of the high antibody line had higher titres at both 5 and 12 days after inoculation with SRBC than those of the low line. Reciprocal effects for SRBC titres were important only for female progeny suggesting sex-linked effects of the Z chromosome. Titres for F(1) progeny were intermediate and different from the parental lines at both 5 and 12 days after inoculation. Antibody titres 5 days after inoculation exhibited heterosis which emanated from the homogametic sex. Although maternal effects generally had no influence on antibody titres, maternal heterosis in the selected trait was due to sex-linkage. Recombination effects were negligible for both traits. ZUSAMMENFASSUNG: Genetische Architekture der Antikörperreaktion von Hühnern auf Schaferythrozyten Zwei Weiße Leghorn-Linien, gegensätzlich selektiert auf starke (HH) oder niedrige (LL) Antikörperreaktion 5 Tage nach Injektion von 0,1 ml einer 0,25% Schaferythrozytensuspension (SRBC), wurden zur Erzeugung von parentalen, reziproken F(1) , F(2) und Rückkreuzungsnachkommen herangezogen. In Alter von 36 Tagen wurde den Tieren eine SRBC Suspension injiziert und Antikörpertiter 5 und 12 Tage später bestimmt. Nachkommen der HH Linie hatten an beiden Tagen höhere Titer als LL Nachkommen. Reziproke Effekte für SRBC Titer waren nur bei weiblichen Nachkommen wichtig, bedingt wohl durch geschlechtsgekoppelte Z-Chromosom Einflüsse. Die Titer der F(1) Nachkommen waren zwischen denen der Elternlinien. Antikörpertiter 5 Tage nach Injektion zeigten Heterosis, die im homogametischen Geschlecht auftrat. Obwohl im allgemeinen maternale Wirkungen keinen Einfluß zeigten, war maternale Heterosis beim selektierten Merkmal auf Geschlechtskopplung zurückzuführen. Rekombinations-wirkungen waren vernachlässigbar.

Antibody transmitting ability of hens from lines of chickens differing in response to SRBC antigen.

1. Hens from White Leghorn lines selected for high (HA) or low (LA) antibody response to sheep red blood cells (SRBC) were inoculated with 0.1 ml of either 0.25% or 2.50% SRBC suspension. Eggs laid over the next 15 d were grouped into 5, 3-d collection periods and incubated. Maternal antibody titres were determined in chicks at hatch and 7 d after hatch. 2. In a subsequent experiment, hens of the 2 lines were inoculated with 0.1 ml of 2.50% suspension of SRBC, and eggs laid on days 10 to 13 after inoculation were incubated. Maternal antibody titres were determined in 15 and 18-d embryos as well as in chicks at 0, 5, 10, 15, 20, and 25 d after hatch. 3. Dosage of SRBC had no effect on the antibody titres in line HA; however, the higher dosage elicited greater antibody titres than the lower dosage in line LA. 4. Maternal antibodies were detected earlier in chicks of line HA (eggs laid on days 7 to 9) than those of line LA (eggs laid on days 10 to 12) regardless of dosage administered to the hens. 5. In both lines, antibodies specific to SRBC were observed on day 15 of incubation, with the frequency of responders greatest at hatch. The high frequency of HA responders was maintained for 15 d after hatch, whereas there was an immediate decline with age in LA responders. 6. It was concluded that lines HA and LA have diverged in the pattern of maternal antibody levels as a result of the divergent selection for antibody response to SRBC.

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.

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.