The effects of broiler chicken growth rate on valgus, varus, and tibial dyschondroplasia.

An experiment was conducted to test the hypothesis that the growth rate of broilers influences their susceptibilities to bone abnormalities, causing major leg problems. Leg angulations, described in the twisted legs syndrome as valgus and bilateral or unilateral varus, were investigated in 2 subpopulations of mixed-sex Arkansas randombred broilers. Valgus angulation was classified as mild (tibia-metatarsus angle between 10 and 25°), intermediate (25-45°), or severe (> 45°). Body weight was measured at hatch and weekly until 6 wk of age. There were 8 different settings of approximately 450 eggs each. Two subpopulations, slow growing (bottom quarter, n = 581) and fast growing (top quarter, n = 585), were created from a randombred population based on their growth rate from hatch until 6 wk of age. At 6 wk of age, tibial dyschondroplasia incidences were determined by making a longitudinal cut across the right tibia. The tibial dyschondroplasia bone lesion is characterized by an abnormal white, opaque, unmineralized, and unvascularized mass of cartilage occurring in the proximal end of the tibia. It was scored from 1 (mild) to 3 (severe) depending on the cartilage plug abnormality size. Mean lesion scores of left and right valgus and tibial dyschondroplasia (0.40, 0.38, and 0.06) of fast-growing broilers were higher than those (0.26, 0.28, and 0.02) of slow-growing broilers (P = 0.0002, 0.0037, and 0.0269), respectively. Growth rate was negatively associated with the twisted legs syndrome and a bone abnormality (tibial dyschondroplasia) in this randombred population.

Divergent selection for body weight and yolk precursor in Coturnix coturnix japonica. 12. Heterosis in reciprocal crosses between divergently selected lines.

A selection experiment was started using Japanese quail to study the genetics of BW and plasma yolk precursor (measured by total plasma phosphorus; TPP). Lines were divergently selected for 4-wk BW (HW and LW) or plasma TPP (HP and LP). Sublines of HW were developed by continuing to select the males for increased 4-wk BW while selecting the females for increased (HW-HP line) or decreased (HW-LP line) TPP. The purpose of the present study was to determine the inheritance of traits associated with growth and reproduction in reciprocal crosses between the divergently selected lines and sublines. Reciprocal crosses were made between the HW and LW, HP and LP, and HW-HP and HW-LP lines. Traits measured included BW at various ages, age at sexual maturity, egg production, ovarian follicular development, egg weight, TPP, wet and dry liver weights, and occurrence of smooth muscle tumors in the ligaments of the oviduct. The HW line differed from the LW line in all traits measured except TPP and weight of smooth muscle tumors. No offspring were obtained from the HW x LW matings (male listed first). In the LW x HW cross, heterosis was negative for BW through sexual maturity and age at sexual maturity. Positive heterosis was observed for egg production, egg weight, and occurrence of smooth muscle tumors. Differences between the HP and LP lines were observed in the selected trait (TPP) and some correlated traits (BW at some ages, age at sexual maturity in females, egg production, and number and total weight of ovarian follicles). Positive heterosis in the HP and LP crosses was observed for BW, egg production, egg weight, and number of ovarian follicles whereas negative heterosis was observed for TPP and age at sexual maturity in females. The HW-HP and HW-LP lines differed in the selected traits and some correlated traits (egg weight and weights of the liver and smooth muscle tumors). Positive heterosis in the crosses was observed for BW, egg production, and liver weights whereas negative heterosis was evident for age at sexual maturity and TPP.

Effect of intermittent activity on broiler production parameters.

The use of intermittent lighting in broiler production has been shown to result in spurts of activity that appear to reduce lameness. Because intermittent lighting is difficult to achieve in curtain-sided houses, the objective of this study was to determine whether simple equipment used to increase activity in broilers would improve production variables. At 1 d of age, 840 male broiler chicks were placed in 24 floor pens. The four treatments (six replicates of 35 chicks each) were as follows: 1) Control-standard feeders, 2) Ramps and Toys-birds had to climb a slight incline ramp to reach feeder and had a hanging mobile, 3) Ramps only, and 4) Toys only-standard feeders. Two trials were conducted. Weekly group weights and feed consumption were recorded. Mortality was recorded daily. At 6 wk of age, birds were bled, euthanatized, weighted, and scored for ascites and tibial dyschondroplasia (TD), and relative heart, liver, and spleen weights were obtained. Blood samples were analyzed for blood gases, hemoglobin, red blood cell count, and clinical chemistries were performed. In Trial 1, during Weeks 2, 3, and 4, treatments with ramps had significantly heavier average bird weight and significantly lower feed:gain ratios. In Trial 2, treatments with ramps had no difference in average BW; however, these groups consumed less feed, resulting in significantly lower feed:gain ratios. Cumulative mortality was decreased by ramp treatment in Trial 2. Toys decreased the incidence and severity of TD in Trial 2. In general, organ weights, blood gases, hematologies, and clinical chemistries were not affected by treatments. However, birds in treatments with ramps had significantly lower serum calcium and smaller hearts in Trial 1, and significantly lower serum cholesterol and smaller hearts in Trial 2.

Liver and blood glutathione in male broiler chickens, turkeys, and quail.

The objective of the present study was to establish age relationships for hepatic and whole blood glutathione (GSH) in male broiler chickens, quail, and turkeys utilizing lines within each poultry species with different rates of growth. Liver and blood samples were obtained from three quail lines (light, medium, and heavy) at 3 and 6 wk of age, from two turkey lines (light and heavy) at 10 and 20 wk of age, and two broiler lines (medium and heavy) at 3, 5, and 7 wk of age. With the exception of the heavy turkey line, older birds generally exhibited higher hepatic GSH concentrations than younger birds. There was no apparent age-related difference in whole blood GSH, nor was whole blood GSH correlated with hepatic GSH in any poultry species.

The leukocyte response of Japanese quail to Rous sarcoma virus-induced tumors.

In male Japanese quail, different circulating leukocyte responses were observed for progressors (birds developing a massive tumor that persisted throughout the experiment) and regressors (birds developing a tumor that gradually disappeared) after initial challenge with Rous sarcoma virus (RSV). Blood was sampled before and at weekly intervals postinoculation. Blood smears were prepared and stained with Diff Quik, and a light microscope (1000 x) was used in a direct count of 50 fields. Leukocytes were classified as heterophils, lymphocytes, monocytes, or eosinophils. The significant increase (P < 0.05) in total leukocytes at 14 days in regressors and progressors was consistent with the increase in tumor growth. The regressors' individual percentage of leukocytes did not deviate from control values, whereas the progressors' percentages of heterophils and monocytes were significantly higher (P < 0.05) and of lymphocytes significantly lower (P < 0.05) than those of controls by 14 days postinoculation. Indicative of this was the progressors' heterophil to lymphocyte ratio, which was significantly higher (P < 0.05) than that of controls 14 days post RSV challenge and remained elevated throughout the experiment. These findings suggest that the progressors' immune response is suppressed by proliferation of malignant cells. Therefore, the heterophil to lymphocyte ratio may be used in addition to tumor size to identify those birds that will regress RSV-induced tumors.

Evaluation of the humoral immune response to different antigens in Arkansas Regressor and Progressor chickens.

Arkansas Regressor and Progressor chickens were re-evaluated for their immune response to different antigens. Chickens received i.v. injection of either SRBC (10 birds per line) or Salmonella pullorum (SP; 10 birds per line) at 7 wk of age, and sera were collected at 6, 13, and 20 d postimmunization. A third group of birds (10 birds per line) received and i.m. injection of GAT emulsion at 7 and 12 wk of age, and sera were collected at 10 and 14 wk of age. There were significant differences between the two lines in their humoral immunity to SRBC, SP, and GAT. Such results suggest genetic control of humoral immunity to these antigens in these lines. It is unknown whether humoral immunity to these antigens is correlated to regression of tumors induced by Rous sarcoma virus.

Research note: lack of an effect of high levels of menadione on tumor development in Japanese quail females.

The objective of the experiment was to study the influence of a high but nontoxic dietary level of menadione (vitamin K3) on the incidence of leiomyomas and leiomyosarcomas in the oviduct of females from various lines of Japanese quail. Analyzed values of vitamin K3 per 1,000 kg of feed were 7.37 g in the control diet, and 149.6, 1,722, and 3,722 g for the experimental diets from 0 to 4, 5 to 8, and after 8 wk of age, respectively. Females were killed after they had been in production for 158 days. Females from three large-bodied lines had a greater incidence of smooth muscle tumors than those from a smaller randombred control line. The high dietary level of vitamin K3 had no influence on tumor development.