Genetic analysis of the growth curve of Rous sarcoma virus-induced tumors in chickens.

White Leghorn chicks homozygous for B19 MHC haplotype were selected for 18 generations on tumor regression after inoculation in the wing web with an SR-D strain of Rous sarcoma virus (RSV) at 4 wk of age. Each chick was assigned a tumor profile index (TPI) based on age at death and size of the tumor. During 18 generations, 2,010 birds were divergently selected on TPI for either progression or regression of the tumor (P and R lines). A Brody growth curve was fitted for each bird. Brody function parameters included the asymptotic tumor volume (A), the factor for increased growth in progression phase (K1), the factor for decreased growth in regression phase (K2), age at maximum volume (Tmax), and maximum volume of the tumor (Vmax). Tumor growth curves were found to be different according to line, sex, and restriction fragment pattern Y complex Rfp-Y MHC haplotype (Yw*15, Yw*16, and Yw*17). Within the P line, birds from the Yw*16 haplotype reached Vmax at an earlier age than Yw*15 and Yw*17, but with a lower Vmax value. Within the R line, tumor growth curves of birds from Yw*16 and Yw*17 haplotypes were similar. Rank correlations between the different parameters and TPI were low (between -0.26 and 0.36). Heritability estimated by the sire component was high for Vmax (0.73). Heritabilities of Tmax and K2 were moderate (0.20 to 0.23 for Tmax and 0.18 to 0.21 for K2) allowing these traits to be used as selection criteria. Heritabilities of A and K1 were lower than 0.12. Modeling the growth curve should contribute to better distinction between progressors and regressors.

Interaction between genotype and dietary concentrations of methionine for immune function in commercial broilers.

1. Growth, antibody response to sheep red blood cells (SRBC) and resistance to Escherichia coli were measured in broiler female chicks received from 4 (n = 100 in each) commercial genotypes (A, B, C and D) and fed with maize-soybean-deoiled rice bran based diets containing 4 concentrations of methionine (3.91, 4.46, 5.00 and 5.54 g/kg). The diets were fed ad libitum from 1 to 49 d of age. 2. Body weight gain and weight gain/food intake at 2 week intervals, response of broilers to inoculation of 0.5 ml of SRBC (0.5 or 2.5%), 0.1 ml of E. coli (10(-4) dilutions) culture, and 100 microg phytohaemogglutinin-P (PHA-P) at 43 d of age were measured. The responses to SRBC and E. coli inoculation were recorded at 5 d post inoculation (PI), while the responses to PHA-P were recorded at 12 and 24 h PI. 3. Genotype by methionine interaction was not significant for body weight gain, but significant differences in weight gain were observed among different genotypes. Variation in methionine concentration did not influence body weight gain or weight gain/food intake at 1 to 14, or 42 d of age. At 28 d of age, chicks fed on the 3.91 g methionine/kg diet weighted significantly less than those on the other methionine concentrations. Genotype by methionine interaction was observed for food efficiency at 0 to 28 d of age but not at other ages. 4. Antibody titres against SRBC and heart and air sac lesion score to E. coli challenge were not influenced by genotype-methionine interaction. Chicks given higher concentrations of methionine had higher antibody titres and greater cutaneous basophilic hypersensitivity (CBH) response than those given low levels of methionine. Also, variation was observed in expression of CBH response to PHA-P among different genotypes. 5. It may be concluded that, although the commercial broiler chicks do not require more than 3.91 g methionine/kg for optimum growth and food efficiency, the immunity in terms of CBH response and antibody production to SRBC increased with the concentration of methionine in the diet in the majority of genotypes, indicating a higher methionine requirement for immunity than for weight gain.

Production performance, serum/yolk cholesterol and immune competence of white leghorn layers as influenced by dietary supplementation with probiotic.

An experiment was conducted to measure the influence of a dietary probiotic on the production performance, the concentrations of cholesterol in the serum and yolk and immune competence in White Leghorn layers from 25 to 72 weeks of age. One hundred and twenty commercial White Leghorn layers, aged 24 weeks, with an average of 62% hen-day egg production, were equally and randomly distributed into three groups, with eight replicates of 5 birds in each. The birds were reared in individual laying cages. They were placed on one of three dietary treatments: basal, or basal with probiotic supplementation at a rate of 100 or 200 mg/kg feed. The addition of probiotic significantly increased the egg production, shell weight, shell thickness and serum calcium, and reduced the concentrations of cholesterol in the serum and yolk. However, no differences in these traits was observed between the groups receiving 100 or 200 mg probiotic. Feed conversion, egg weight, serum phosphorus and serum alkaline phosphatase activity were not influenced by supplementation with probiotic. Antibody production in response to the inoculation of sheep red blood cells and the cutaneous basophilic hypersensitivity (CBH) responses to inoculation with phytohaemagglutinin did not differ significantly among the dietary groups at either 24 or 40 weeks of age. The antibody titre was significantly higher in the groups supplemented with probiotic at 64 weeks of age. The addition of 100 mg/kg of probiotic in the diet significantly increased the CBH response at 64 weeks of age.

Effect of supplementary choline on the performance of broiler breeders fed on different energy sources.

1. Laying performance, egg quality, fertility and hatchability, and fat deposition in liver and abdomen were recorded in broiler breeders (29 to 48 weeks of age) fed on diets containing perarl millet (Pennisetum typhoides) (PM), broken rice (BR) or yellow maize (YM) (600 g/kg diet). Constant ratios of metabolisable energy (ME) to other nutrients were maintained in all the diets. Food grade choline chloride (50%) was added to the diets at 3 concentrations (0, 760 and 1,520 mg/kg). Each diet was offered to 3 replicate groups of 15 birds (12 hens and 3 cockerels), maintained in deep litter pens, to provide 1.46 MJ ME/bird/d. 2. Neither the source of energy nor dietary choline content had any influence on hen-d egg production, fertility or hatchability. Food efficiency and egg weight were significantly reduced in BR-fed groups compared to those fed on the other energy sources. 3. The efficiency of energy and protein utilisation increased and liver fat content was decreased significantly by dietary choline supplementation. 4. Haugh unit score, egg shell weight, liver weight and intestinal weight were not influenced by either supplementary choline or the source of energy. However, the yolk colour index was significantly reduced in PM- or BR-fed groups compared to those fed on the maize-based diet. 5. Deposition of abdominal fat was significantly greater in BR-fed birds compared to those fed on the YM-based diet, while liver fat content was significantly greater in the birds fed on the PM-or BR-based diets than those based on YM. Although supplementation of the diet with choline had no influence on abdominal fat deposition, liver fat content was significantly reduced in birds given diet containing 760 mg supplemental choline/kg diet. 6. The present study indicates that PM or BR can be used as principal energy sources in place of YM in broiler breeder diets without affecting egg production, fertility or hatchability. Liver fat content can be reduced by adding choline at 760 mg/kg to diets based on different energy sources.

Immune competence, resistance to Escherichia coli and growth in male broiler parent chicks fed different levels of crude protein.

Immune competence, resistance to Escherichia coli and growth were measured in female chicks of broiler male parent lines from four different commercial sources. These chicks were fed with three levels of dietary crude protein (CP) from day-old. The protein contents in the diets were 18%, 20.5% and 23%; these diets are referred to as the low-, medium- and high-protein diets, respectively. There was a significant genotype by dietary protein interaction for body weight at 35 days of age but not at 14 or 28 days of age. At 14 days of age, the chicks fed on the high-protein diet weighed significantly more than those fed on the low-protein diet, but there were no differences between the chicks fed on the medium-and low-protein diets. The influence of CP content on body weight had disappeared by 28 days of age. There were significant differences between the genotypes-in antibody production in response to sheep red blood cell (SRBC) inoculation, but no such differences were observed between the chicks fed the different levels of dietary protein. Chicks fed on the high-protein diet had lower lesion scores following E. coli inoculation than those fed on the low-protein diet. There were also significant differences in lesion scores among the genotypes. Genotypes with heavier body weights had significantly higher lesion scores and lower antibody titres than those with less body weight. Also, genotypes of lower body weight had a greater cutaneous basophilic hypersensitivity response to phytohaemaglutinin-P inoculation, and a better humoral response against SRBC and a lower heterophil to lymphocyte ratio.

Dietary effects on immune response of fast-growing chicks to inoculation of sheep erythrocytes and Escherichia coli.

Responses to SRBC and Escherichia coli inoculations were measured during the early posthatch period in broiler cockerels fed diets differing in nutrient density. Diet A consisted of 20% protein and 2,685 kcal ME/kg and Diet B consisted of 24% protein and 3,146 kcal ME/kg. There was no effect of diet on antibody response of chicks inoculated at 10 d of age with 0.25, 2.50, 5.00, or 25.00% suspensions of SRBC. A significantly larger proportion of chicks, however, produced antibody at the 25.00% than at the 0.25% dosage of SRBC. When inoculated at 15 d of age with 10(-6), 10(-4), or 10(-2) dosage of E. coli, there were no significant diet by dosage interactions for lesion scores, or relative change in BW 24, 48, and 120 h after inoculation. There were differences among E. coli dosages for severity of lesions and mortality, with rankings being 10(-2) > 10(-4) > 10(-6). Lesion scores and mortality were higher for the chicks fed Diet B than those fed Diet A. Also, deleterious effects of E. coli on BW 24, 48, and 120 h after inoculation were greater for chicks fed Diet B than for chicks fed Diet A. Responses to inoculations of SRBC and E. coli of broilers fed a diet with a lower nutrient density were equal or superior to those of broilers fed a diet with a higher nutrient density.

Immunoresponsiveness of fast-growing chickens as influenced by feeding regimen.

1. Immunoresponsiveness and disease resistance were measured in broiler males maintained on ad libitum feeding throughout or on alternate-day feeding. Alternate-day restrictions were started 1 and 2 d after hatch so that on any one day there were chicks fed and fasted. 2. Severity of response to E. coli challenge as measured by lesion scores, and mortality was greater for chicks fed ad libitum than those fed on alternate days. For chicks fed on alternate days, lesion scores were lower for those without access to feed for the 24-h period immediately after challenge. 3. Spleen weights, the indicator of response to marble spleen disease virus challenge, were higher for chicks fed ad libitum than those fed on alternate days. 4. Antibody response to sheep red blood cell antigen was not affected by feeding regimen. 5. Ratios of heterophils to lymphocytes were higher for chicks given access to feed for the previous 24-h period than for those fasted during the previous 24-h or those that had been fed ad libitum. 6. Results of this experiment suggest that for alternate-day feeding programs, vaccination be administered on the day that chicks are not fed.

Feeding regimen by sire family interactions on growth, immunocompetence, and disease resistance in chickens.

Progeny from matings of 12 sires from a White Plymouth Rock line selected for high juvenile BW and 96 dams from a White Leghorn line selected for low antibody production to SRBC were reared under alternate-day (AD) or ad libitum (AL) feeding regimens. Within a feeding regimen males were heavier than females, and within a sex, chicks fed AL were heavier than those fed AD. Feeding regimen by sire family interactions were significant for BW at 21 d of age for both male and female progeny. The interaction was due to differences among sires in the magnitude of the AD: AL relationship. Product moment correlation coefficients between feeding regimens for male and female progeny of sire families for 21-d BW were essentially zero, which was consistent with the sire family by feeding regimen interactions observed at this age. At 41 d of age, relative to BW, weights of empty esophagus plus crop and of crop contents were greater for AD than AL chicks. There were differences among sire families for crop content and breast weights relative to BW. Lesion scores to Escherichia coli challenge were lower and antibody titers to SRBC antigen were higher in AD than in AL chicks. Sire families differed in antibody titers to SRBC antigen. Feeding regimen by sire family interactions were significant for percentage change in BW 144 h after E. coli challenge and lesion scores were greater for AL than AD chicks.

Growth, immunoresponsiveness, and disease resistance of diverse stocks of chickens reared under two nutritional regimens.

Growth, immunocompetence, and disease resistance were measured in a commercial broiler stock (BC), a commercial white-egg-layer stock (LC), and a White Plymouth Rock line selected for high juvenile BW (HW) under dietary regimes differing in protein and energy content. Diet E had 20% more protein and 17% more ME than Diet A. Stock by sex interactions were significant for BW at 28 and 36 d of age because sexual dimorphism occurred at younger ages in the meat than in the layer stocks. When inoculated with .1 mL of a .25 or 2.50% suspension of SRBC, diet by stock interactions were significant for antibody titers 6 d postinoculation (PI) at the lower dosage. Interactions were not present at the higher dosage or for either dosage 13 d PI. Diet by stock interactions were significant at both dosages for change in SRBC titers from 6 to 13 d PI. The interactions resulted from a significantly smaller decline in BC than HW or LC chicks fed Diet A, whereas all stocks responded similarly when fed Diet E. A significant decline in rate of BW gain was observed in chicks inoculated with marble spleen disease virus (MSDV), with the increase in relative weight of spleen significantly greater for LC than HW or BC chicks 6 d PI. When heterophil to lymphocyte ratios were used as an assay of response to MSDV challenge, rations were significantly higher for HW chicks fed Diet A than for chicks fed Diet E and for LC chicks fed Diet E than for chicks fed Diet A, but not different for BC chicks on the two diets.