Village poultry consumption and marketing in relation to gender, religious festivals and market access.

This study aimed to examine village poultry consumption and marketing in Ethiopia in relation to gender, socio-cultural events and market access. The main objects of the research were producers, poultry markets, producer-sellers, and intermediary sellers in three locations representing different levels of market access in Tigray. About 3000 farm records were collected over a period of 12 months from 131 producers to obtain quantitative data on sales and consumption. Ninety-three semi-structured interviews with 58 producer-sellers and 35 intermediaries and 12 group discussions with these market actors were conducted to explore organization, price dynamics and socio-cultural aspects of poultry marketing. In total, 928 producer-sellers and 225 intermediaries were monitored monthly to examine participation by gender in poultry marketing. Better market access was associated with a shorter market chain and higher prices for the producers. Female-headed households had smaller poultry sales and consumption per household but sale and consumption per family member were 25% and 66% higher, respectively, than in male-headed households. While women dominated in the producer-sellers group, intermediaries were mainly men. Religious festivals periodically shifted local demand and prices of poultry. To improve the benefit of poultry keeping, poverty-stricken households may profit from better market access through better market information, infrastructure, market group formation and careful planning to match the dynamics in demand.

Phagocytic activity of two lines of chickens divergently selected for antibody production.

Differences in phagocytic capacity of two chicken lines selected for high (H) or low (L) antibody response against sheep red blood cells (SRBC) were studied in 8 month old cocks of the seventh selection generation. The H line cocks had significantly higher agglutinin titers after immunization with SRBC than the L line. The total clearance capacity of the phagocytes, measured by the clearance of carbon particles from the blood, did not differ between the lines. The L line cocks had more circulating granulocytes. However, the granulocytes of the H line phagocytized more yeast cells than those of the L line. Neither in immunized nor in non-immunized cocks, were line differences found in the intracellular destruction of antigen by phagocytes, estimated as the superoxide production during phagocytosis and the plasma levels of lysozyme activity and acid phosphatase, before and after immunization. It was concluded that the line difference in antibody response was not due to measurable differences in phagocytic activity.

Mapping of susceptibility to Marek's disease within the major histocompatibility (B) complex by refined typing of White Leghorn chickens.

The major histocompatibility (B) complex of a distinct commercial pure White Leghorn chicken line was characterized using serological, biochemical and restriction fragment length polymorphism (RFLP) typing. Line B chickens displayed a high recombination frequency within the B complex. Three recombinant haplotypes were identified. The influence of these haplotypes was determined in relation to the haplotypes B19 and B21 on their resistance to Marek's disease (MD) in an experimental infection with the virus. Offspring of sires with a recombinant haplotype in combination with B19 or B21, and dams, which were homozygous B19/B19 or B21/B21 were infected. The B type of the offspring had a significant effect upon survival. Animals with B complex types B21/B21, B134/B21 and B234/B21 were relatively resistant to MD (24-32% mortality), whereas B19/B19 birds were highly susceptible (68% mortality). Animals with a recombinant haplotype B19r21 (B-G21, B-F19) were equally susceptible to MD as birds with the complete B19 haplotype. In contrast to earlier publications, resistance was not inherited as a dominant trait. Apparently, B19 was associated with a dominant susceptibility. The gene(s) associated with the B complex and involved in resistance to MD were localized within the B-F/B-L region. However, the association with a presumably non-coding subregion of B-G could not be excluded.

Effect of divergent selection for immune responsiveness and of major histocompatibility complex on resistance to Marek's disease in chickens.

Lines of chickens selected for nine generations for high (H) or low (L) antibody response to SRBC, a randombred control (C) line, and an F1 cross between H and L lines were challenged for resistance to Marek's disease (MD). Hens only were challenged at day-old by contact with virulent MD Strain K. Birds were serologically typed for MHC erythrocyte antigens. Chicks from the L and H lines died earlier and later, respectively, than the C chicks, whereas time of death did not differ between F1 birds and the L chicks. Mortality in the L line (70.1%) was higher than in the C line (42.8%), but mortality in the H line (40.9%) was not lower than in the C line or the F1 cross (47.5%). Effects of MHC genotypes and haplotypes on mortality from MD were estimated within lines with a logistic regression model. Effect of MHC was moderate in the H line (P < .10) and highly significant in the C line (P < .005). Effects of MHC genotypes were similar in the H and C line but differed in the L and F1. Heritability of mortality from MD estimated with a threshold model including relationships between individuals was .40 when all lines were grouped together, whereas heritability estimated for each line separately was .45, .51, and .78 in the H, C, and L lines, respectively. Correlations between estimated breeding values for antibody response to SRBC and mortality from MD varied between lines and sexes. Correlations also were affected by whether or not the MHC effect was taken into account.

Effect of vitamin A deficiency and Newcastle disease virus infection on IgA and IgM secretion in chickens.

The effect of vitamin A deficiency or the lentogenic La Sota strain of Newcastle disease virus (NDV) infection, or both, on immunoglobulin (IgA and IgM) levels in bile and plasma were investigated. In addition, tissue distribution of IgA-, IgG- and IgM-containing cells was studied to establish the source of these Ig. Chickens (1-d-old) with limited vitamin A reserves were fed ad lib. on diets containing either marginal or adequate levels of vitamin A. At 4 weeks of age, half the chickens in each group were infected with NDV. The number of IgA- and IgM-containing cells was not significantly affected by vitamin A deficiency, demonstrating that neither class-switching nor homing of Ig-containing cells is influenced by vitamin A deficiency. Although bile IgM levels were not significantly different in vitamin A-deficient chickens compared with normal chickens, IgA levels were significantly lower. This decrease was even more pronounced in deficient NDV-infected chickens, despite the higher number of IgA-containing cells found in these birds. These results, together with the slightly increased levels of IgA in plasma of vitamin A-deficient chickens, suggest that the hepatobiliary transport of IgA is impaired by vitamin A deficiency and possibly also by NDV infection, although disturbed secretion by IgA-containing cells cannot be excluded.

Divergent selection for immune responsiveness in chickens: estimation of realized heritability with an animal model.

With the aim of improving general disease resistance, chickens were divergently selected for their antibody titers 5 d after immunization with sheep red blood cells for nine generations. Selected and control lines differed significantly for primary and secondary responses after three generations. Heritability of the antibody titer was estimated by REML fitting an animal model using a derivative-free algorithm. The heritability estimate using data on all lines simultaneously was .31. Realized heritability of the antibody titer in the selected lines was estimated by using either the phenotypic cumulative response as the deviation from the control line or the mean breeding values obtained with an animal model. Values from the two methods were consistent, giving a realized heritability of .21 and .25 in the high and low lines, respectively. The genetic trend was not linear and the response to selection tended to accelerate over generations.

Production of chickens with marginal vitamin A deficiency.

Marginally vitamin A-deficient 1-d-old chickens capable of remaining healthy for at least 6 weeks were produced using a two-generation model. In this model, hens fed on diets with a limited vitamin A content were used to obtain 1-d-old chickens which were marginally deficient in vitamin A. Only hens with a narrow range of plasma retinol values (0.60-0.85 mumol/l) were satisfactory for this purpose. Above this range the 1-d-old chickens were not marginally vitamin A deficient. Below this range egg production and hatchability were affected to some extent depending on the degree of vitamin A deficiency. Even when egg production and hatchability remained at a high level in such birds, the 1-d-old chickens produced were not sufficiently strong to survive the first weeks of life. The advantages of the two-generation model for producing marginally vitamin A-deficient chickens are the increased uniformity and predictability of the chickens with respect to body-weight, general health and vitamin A status. However, it does take about 3 months to produce such chickens.

Effects of route of immunization, adjuvant and unrelated antigens on the humoral immune response in lines of chickens selected for antibody production against sheep erythrocytes.

Effects of intramuscular (i.m.), intravenous (i.v.) and intraperitoneal (i.p.) primary immunization with the T-dependent antigen, sheep red blood cells (SRBC), was studied in two chicken lines selected for either high (H) or low (L) antibody response after i.m. immunization with SRBC. The primary route of immunization affected the line differences in the primary response and in the secondary response after i.m. reimmunization. Intravenous immunization with the T-dependent antigen bovine serum albumin (BSA) showed line differences similar to those found after i.m. or i.v. immunization with SRBC. Immunization with both the partially T-independent antigens Brucella abortus (BA) or Salmonella H-antigen (SHA) revealed no line effect. Immunization with SRBC in incomplete Freund's adjuvant (IFA) did not change the difference between lines, whereas immunization with complete Freund's adjuvant (CFA) diminished the difference between lines. It is postulated that differences in antibody production between the selected lines might be attributed to differences in T-cell activity.

Epithelia-damaging virus infections affect vitamin A status in chickens.

The effect of infection with infectious bronchitis virus (IBV) and reovirus (RV) on vitamin A status was investigated in chickens with a normal or marginal intake of vitamin A. At the age of 4 wk, chickens were infected with either IBV or RV, primarily affecting the respiratory or intestinal tract, respectively. Both viruses lowered plasma retinol levels significantly. The effect was more pronounced in chickens fed a diet marginally deficient in vitamin A than in those fed a diet adequate in vitamin A. Concentrations of retinol-binding protein, transthyretin and albumin in RV-infected chickens were also significantly lower than in noninfected chickens fed the same diets; in chickens infected with IBV, there was no effect. These results suggest that the reduced vitamin A status of IBV-infected chickens could be attributed to increased rate of utilization by tissues. In RV infection, this mechanism could be involved but impaired absorption of nutrients (including vitamin A) and direct loss of nutrients via the intestinal tract could also be important.

Effect of vitamin A deficiency on the activity of macrophages in Newcastle disease virus-infected chickens.

The effect of vitamin A deficiency on the activity of peritoneal macrophages (PM) was investigated in noninfected and Newcastle disease virus (NDV)-infected chickens. Day-old chickens with limited vitamin A reserves were fed diets containing either marginal (120 retinol equivalents (RE)/kg) or adequate (1200 RE/kg) levels of vitamin A. At 4 weeks of age, half of the chickens in each group were infected with the La Sota strain of NDV and PM were isolated 11 or 12 days later. These were used for counting the uptake of fluorescein isothiocyanate-labeled yeast cells as an indicator of phagocytic activity and for measuring the reduction of nitroblue tetrazolium (NBT), which provides an estimate of oxygen-dependent killing of microorganisms. Vitamin A deficiency impaired NBT reduction and, to a lesser extent, phagocytosis in both infected and noninfected chickens. NDV infection increased phagocytosis and NBT reduction in normal and, to a lesser extent, in vitamin A-deficient chickens.

Changes in lymphoid organs and blood lymphocytes induced by vitamin A deficiency and Newcastle disease virus infection in chickens.

The effect of vitamin A deficiency in the presence or absence of Newcastle disease virus infection (NDV, La Sota strain) on weight of lymphoid organs and on the number and type of circulating white blood cells (WBC) was investigated in chickens. Day-old chickens with limited vitamin A reserves were fed purified diets containing either marginal (ad libitum) or adequate (pair-fed) levels of vitamin A and at 21-28 days of age; half the chickens in each group were infected with NDV. Vitamin A deficiency resulted only in significantly lower absolute and relative weights of bursa of Fabricius and after infection both weights of bursa and thymus were significantly lower. Relative weight of spleen was significantly higher after infection irrespective of vitamin A status. Liver weights were not affected by vitamin A status and/or NDV infection. Both vitamin A deficiency and NDV infection resulted in lymphopenia, while the lowest number of WBC were observed in vitamin A-deficient chickens during the acute phase of NDV (5 days after infection). Subsequent to lymphopenia due to NDV infection, a marked lymphocytosis was observed in controls and to a lesser extent in vitamin A-deficient birds. These results indicate that vitamin A deficiency, which is aggravated by concomitant NDV infection, affects lymphoid cell systems.

Vitamin A deficiency impairs cytotoxic T lymphocyte activity in Newcastle disease virus-infected chickens.

The effect of vitamin A deficiency on cytotoxic T lymphocyte (CTL) activity was investigated during the acute phase of disease 7 days after primary inoculation and 1 day after secondary inoculation in chickens with or without Newcastle disease virus (NDV, La Sota strain) infection. Day-old chickens with limited vitamin A reserves were fed purified diets containing either marginal (ad libitum) or adequate (pair-fed) levels of vitamin A, and at 3 weeks of age half of the chickens in each group were infected with NDV. Cytotoxic activity was investigated during the acute phase of disease (7 days after primary inoculation) and 1 day after secondary inoculation, in an assay system with either peripheral blood lymphocytes (PBL) or nonadherent splenocytes as effector cells and adherent splenocytes from the same animal as target cells. After primary inoculation, cytotoxic activity could only be demonstrated in nonadherent splenocytes. Vitamin A deficiency resulted in significantly reduced CTL activity at all effector/target cell ratios tested. After reinfection CTL activity could also be demonstrated in PBL, but only from chickens fed the control diet, suggesting a diminished pool of CTL in vitamin A deficiency. The results of this study indicate that vitamin A deficiency impairs CTL activity - a part of the cell-mediated defense system - and this may have important implications for recovery from viral infection.

The effect of serologically defined major histocompatibility complex haplotypes on Marek's disease resistance in commercially bred White Leghorn chickens.

In commercial pure white leghorn lines, A, B, and C, the effects on resistance against a virulent strain of Marek's disease virus were assessed for B19 and B21 haplotypes of the chicken major histocompatibility complex. B haplotypes were identified by direct hemagglutination using alloantisera raised against erythrocyte antigens. In homozygous B21 female chicks from lines A and B, mortality upon challenge with virus was 16% and 9%, respectively; in B19 chicks, mortality was 42% and 60%, respectively. Intermediate mortality was observed in heterozygous B19/B21 birds. When line A and B hens were crossed with B15/B15 or B5/B19 cocks from line C, differences between B19 and B21 were significant only in the progeny from B5/B19 sires. Therefore, it was concluded that selection for major histocompatibility complex-associated disease resistance markers may be useful only when B haplotypes complement each other in commercial line crosses and when interactions with genetic background do not severely obscure the differential haplotype effects, as are observed within pure lines.

[Genetic manipulation in farm animals: how and why?]. / Genetische manipulatie bij landbouwhuisdieren: hoe en waartoe?

A review of the history of the knowledge of the development of DNA was presented on the symposium 'Biotechnology'. Entirely in agreement with expectations, genetic manipulation became suitable for use, also in farm animals, approximately thirty years after the discovery of the double helix. The technology available for transfection is limited and is only successful in a small number of cases: less than one per cent. In addition, gene constructions give rise to a large number of problems as they are not tissue-specific and fail to function at the correct time in the course of development. The knowledge of interesting genes (at DNA level) in farm animals is of vital importance. Detecting these genes will undoubtedly still require considerable effort. In view of the technical state of things, medical and physiological studies using transfection will obviously have to provide a new insight prior to use. This is in agreement with the memorandum on 'Ethics and Biotechnology in Animals'. A 'no, unless' procedure is recommended in this note, room being left for 'good' objectives of research following ethical consideration.

Heat-stress influences on antibody production in chicken lines selected for high and low immune responsiveness.

The effect of heat stress on antibody production to sheep red blood cells (SRBC) was investigated during three experiments using chicken lines selected over six generations for high (H) or low (L) plasma-antibody titer to SRBC after primary intramuscular immunization. The chickens were immunized 24 h after a heat-stress treatment (HS) of four periods of 30 min each at a temperature of 42 C with an intervening 30-min period at a temperature of 22 C. For the control treatment (CT), the chicks were handled the same, but at a temperature of 22 C. Antibody titers were measured on 3, 5, 7, 10, and 14 days postimmunization. The intramuscular immunizations, .25 mL of SRBC, were given in all three experiments; an additional intravenous immunization of .5 mL of 14% SRBC was given in Experiment 2 and of .5 mL of 5% SRBC in Experiment 3. A significant effect of the HS treatment on antibody titers (P less than .05 on Days 3, 5, 7, and 10 after immunization) was found only in Experiment 1. The titers decreased in the H line only. The differences between the H and L lines were significant (P less than .001) in all three experiments after both the intramuscular and the intravenous immunizations. Heat stress was found to have little or no effect on antibody production in the lines studied in the present experiments.

Effect of different doses of sheep erythrocytes on the humoral immune response of chicken lines selected for high or low antibody production.

A study was conducted to determine the influence caused by the dose of sheep red blood cells (SRBC) on the humoral response of chicken lines selected for high (H) or low (L) antibody production to SRBC. The chicks were of the 5th selection generation. Both sexes were used. The primary doses of SRBC used were: 5 x 10(-4), 5 x 10(-3), 5 x 10(-2), 25 x 10(-2), and 5 x 10(-1) mL packed cells, suspended with phosphate-buffered saline (PBS) to 1 mL, and injected intramuscularly (im). All chicks were reimmunized im with 5 x 10(-1) mL packed cells in 1 mL of PBS. Throughout the experiment, H line chicks had higher titers than L line chicks. The level of primary total and 2-mercaptoethanol (2ME)-resistant titers followed the dose level. However, in total titers, the interactions between line and dose were seen at days 3 and 5 postimmunization. This was caused by a deviation in the ranking of the doses in the L line. Moreover, the kinetics of the primary response differed between the lines. Generally, in H line the peak number for the titers was reached earlier in the response period. The optimum response in terms of the total number of titers in the secondary response generally was inverse to the primary dose level. However, from Day 7 of the secondary response onward, the dose effects were influenced by line. For Line L, no effects for dose on the responding antibody level was seen. The 2ME-resistant titers followed the dose level in the secondary response.(ABSTRACT TRUNCATED AT 250 WORDS)

Interference with the humoral immune response in diverse genetic lines of chickens. II. The effect of colloidal carbon.

Two experiments were conducted to study the difference in humoral immune responses between lines of chickens selected for high (H) or low (L) antibody production to sheep red blood cells (SRBC). Prior to i.v. immunization with SRBC or Brucella abortus (BA), chicks of both lines were injected with either 2, 3 or 4 ml carbon suspension (59 mg carbon/ml) per kg body weight; controls were not injected. In both the H and L line, a higher dose of carbon showed a more progressive depression of the total antibody titer to SRBC during the initial stage of the primary response. The 2ME-resistant antibody titers to SRBC showed the same tendency during the latter phase of the primary response. However, chicks treated with 3 ml carbon had lower 2ME-resistant antibody titers than any other group. Following i.m. reimmunization with SRBC, the previous treatment with carbon doses enhanced total antibody titers throughout the secondary response, when compared to the controls. The 3 ml carbon-treated chicks had the highest total anti-SRBC titers in the secondary response. The secondary 2ME-resistant anti-SRBC titers were not affected by the carbon doses. Carbon treatment did not affect the antibody titers to BA. No differences between the H and L line were found in the effects of carbon on the humoral immune responses to SRBC or BA.

The interaction between vitamin A status and Newcastle disease virus infection in chickens.

Newcastle disease virus (NDV) infection in chickens differing in vitamin A status has been selected as a model to examine the interrelationship between marginal vitamin A deficiency and the severity of consequences of measles infection in humans. Day-old chickens with limited vitamin A reserves, the progeny of marginally vitamin A-deficient hens, were fed purified diets containing either marginal (120 retinol equivalents/kg diet, ad libitum) or adequate (1200 retinol equivalents/kg diet, ad libitum or pair-fed) levels of vitamin A for a period of 10 wk. At 4 wk of age, half of the chickens in each group were infected intraocularly with the lentogenic, i.e., mildly pathogenic, La Sota strain of NDV. Within 1 wk of infection, plasma retinol levels in the infected, marginally vitamin A-deficient chickens showed a significant and persistent decrease compared to their noninfected counterparts fed the same diet. Moreover, infection with NDV resulted in increased rates of morbidity in the marginally vitamin A-deficient chickens compared with nondeficient chickens. The results of this study indicate that pre-existing marginal vitamin A status increases the severity of disease following NDV infection, and that infection with NDV reduces marginal plasma vitamin A levels to levels which can be regarded as deficient.

Effect of Newcastle disease virus infection on vitamin A metabolism in chickens.

The effect of Newcastle disease virus (NDV, La Sota strain) infection on vitamin A metabolism was investigated in chickens maintained on normal or marginal vitamin A intake. NDV, a virus of the Paramyxoviridae family that primarily affects epithelial tissue, was administered at 4 wk of age. Plasma levels of retinol, retinol-binding protein and, to a lesser extent, transthyretin were found to be significantly lower during both the acute and postacute phases of infection in chickens fed a diet marginally deficient in vitamin A compared to noninfected birds fed the same diet, while vitamin A content in liver was unaffected. However, in chickens fed adequate vitamin A, NDV infection did not influence the parameters measured. Levels of retinol-binding protein in liver were significantly increased by inadequate vitamin A nutriture, but infection partly reduced this increase. The results suggest that the reduced vitamin A status in marginally vitamin A-deficient chickens infected with NDV can be attributed to a combination of a direct effect of the virus on retinol-binding protein metabolism in liver and an increased rate of utilization and catabolism of retinol and retinol-binding protein by extrahepatic tissues.