Effect of feed allowance during rearing and breeding on female broiler breeders. 1. Growth and carcass characteristics.

The influence of feed allowance on growth and carcass characteristics was investigated with female Indian River broiler breeders. Four feeding programs were imposed: FF, provided ad libitum access to feed throughout; FR, provided ad libitum access to feed from 0 to 18 wk of age and restricted thereafter; RF, provided ad libitum access to feed from 0 to 4 wk, restricted from 4 to 18 wk, and consumed feed ad libitum thereafter; RR, provided ad libitum access to feed from 0 to 4 wk of age and restricted thereafter. All birds received a starter diet (2,739 kcal ME/kg, 19.1% CP) from 0 to 3 wk of age, a grower diet (2,729 kcal ME/kg, 15.5% CP) from 3 to 22 wk of age, and a layer diet (2,889 kcal ME/kg, 14.6% CP) from 22 to 62 wk of age. Restricted feeding (limited amount, fed daily) was based on commercial BW guidelines. Feed restriction (37.2% of ad libitum intake) during rearing (4 to 18 wk) slowed growth. At 18 wk of age, restricted birds (RF, RR) had an average BW of 1.9 kg and a shank length of 9.2 cm compared with ad libitum-fed birds (FF, FR), which had an average BW of 4.2 kg and a shank length of 10.8 cm. Despite the large difference in BW, percentage carcass protein did not differ significantly between the two rearing treatments; however, percentage carcass fat was almost four times greater in ad libitum-fed than in feed-restricted birds. The growth deficit remained significant to 62 wk of age in RF birds compared with FF birds. During the prebreeding period (18 to 23 wk), feed intake of RF birds was 209% that of RR birds and 133% that of FF birds. At sexual maturity, the BW of RF birds was 3.6 kg, compared with 4.6, 4.5, and 2.6 kg for FF, FR, and RR birds, respectively. Stepwise regression indicated that BW was the most important (R2 = .363, P = .0001) among 11 variables in determining the number of large (greater than 10 mm) follicles in the ovaries of breeders at sexual maturity.

Effect of kernel density on the apparent and true metabolizable energy value of corn for chickens.

Five samples of corn selected to vary widely in kernel density (test weight per unit volume) were assayed for AMEn with male broiler chickens at 4 wk of age by regression analysis of a multilevel assay and for TMEn with adult White Leghorn roosters. The kernel densities (kilograms per hectoliter), AMEn, and TMEn (kilocalories per gram of DM) values of the corn were, respectively, 72, 3.68, and 3.96; 71, 3.72, and 3.95; 68, 3.66, and 3.90; 62, 3.64, and 3.88; 60, 3.54, and 3.68. Positive relationships were established between AMEn and TMEn (r = .974, P less than .01) or kernel density (r = .875, P less than .05). The assay for TMEn provided a simple, rapid and sensitive method for estimating the AMEn content of corn for chickens. The small (4%) variation in AMEn relative to a large (20%) variation in kernel density precludes the use of kernel density for estimating the AMEn content of corn.

Reproductive senescence in domestic fowl: effects on egg production, sequence length and inter-sequence pause length.

1. Age-related changes in egg production, oviposition sequence length and inter-sequence pause length were studied by analysis of oviposition records of 50 individually-caged broiler breeders from 24 to 62 weeks of age. 2. The 44 surviving hens exhibited a production profile characteristic of broiler breeders (184 eggs per hen), with a peak mean sequence length of 19 eggs at 32 weeks of age. Inter-sequence pause length was maximum (1.6 d) at 54 weeks of age. Overall, the hens averaged 48 sequences, with a mean sequence length of 4.1 d. 3. Most hens had a single characteristically long sequence about the time of peak egg production (average: 24.3 d). The term 'prime' is suggested to denote this sequence. 4. Sorting the hens into groups on the basis of total egg output (upper and lower 50% and upper and lower 25%) indicated that high producing hens (upper 50% and 25%) had a very long prime sequence early in lay, and had few inter-sequence pauses of greater than 1 d duration. The converse was true for low producers (lower 50% and 25%). 5. The length of the prime sequence may be a good indicator of reproductive efficiency of hens later in life.

Cholesterogenesis from propionate: facts and speculations.

Cholesterogenesis from [1-14C]acetate and [2-14C]propionate by the liver and adipose tissue has been studied in vitro. In all species tested including the rat, mouse, chicken, cow and pig, labelled propionate was recovered in cholesterol following the same trend as acetate, but at lower incorporation rates. Chicken liver was the most active in incorporating both substrates into cholesterol. In the cow and pig, the rates of cholesterol synthesis were higher in the adipose tissue than in the liver. Three alternative mechanisms are proposed to explain the recovery of propionate in cholesterol.

Rates of entry of alanine and glycerol and their contribution to glucose synthesis in fasted chickens.

Rates of entry of alanine and glycerol and their contribution to glucose synthesis were studied in 48-h fasted White Leghorn cockerels using primed constant intravenous infusions of L-[U-14C]alanine and [U-14C]glycerol. Entry rates of alanine and glycerol were 112 and 401 mumol/h per kg body weight, respectively. Of the total glucose irreversible loss (entry rate), 1.5 and 6.6% were derived from alanine and glycerol, respectively. The possibilities of the operation of a glyoxylate cycle and omega-oxidation of fatty acids in the fasted chicken are discussed.

Rates of entry and oxidation of D(-)-3-hydroxybutyrate and glucose in fed and fasted chickens.

Rates of entry and oxidation of D(-)-3-hydroxybutyrate (DBHB) and glucose and their contribution to the total metabolic production of CO2 were studied in fed and 48-hr fasted Leghorn roosters using primed constant intravenous infusions of NaH14CO3, D(-)-3-[3-14C]-hydroxybutyrate, and D-[U-14C] glucose. Fasting increased plasma DBHB concentrations sixfold but did not change plasma glucose levels. In both states of nutrition, rates of CO2 production were identical (P greater than .05). Mean fractions of the total CO2 derived from DBHB and glucose in fed and fasted chickens, respectively, were: DBHB, 1.7 and 9.9% (P less than .001); glucose, 29 and 10% (P less than .001). Entry rates of DBHB and glucose in fed chickens were 276 and 5936 mumoles/hr per kg (P less than .001), respectively, and in starved birds were 1703 and 2204 mumoles/hr per kg (P less than .001), respectively. Fasting increased the oxidation rate of DBHB from 124 to 737 mumoles/hr per kg (P less than .001) and decreased the oxidation rate of glucose from 1491 to 525 mumoles/hr per kg (P less than .001). During fasting, glucose homeostasis is maintained in part by concomitant decreases in glucose entry and oxidation rates. The results are discussed with reference to the sparing effect of DBHB on glucose oxidation.

Effect of the previous diet, body weight, and duration of starvation of the assay bird on the true metabolizable energy value of corn.

Two experiments were conducted with 36 adult White Leghorn roosters to determine the effect of previous intake of protein (Experiment 1) or purified cellulose (Experiment 2), body weight, and duration of starvation of the assay bird on the true metabolizable energy (TME) value of ground yellow corn. The mean TME value (+/- SE) of the corn was 4.06 +/- .03 and 4.06 +/- .04 kcal/g of dry matter in Experiment 1 and 2, respectively. Dietary levels of 10, 20, and 30% protein or 0, 7.5, and 15.0% supplementary cellulose, and body weight distribution had no significant (P greater than .05) effect on the TME value of the corn. Starvation for 12 hr before force feeding resulted in a significant (P less than .05) decrease of 4% in the TME value of the corn, whereas fasting periods of 24 or 48 hr had no significant effect. It is suggested that the assay birds be paired on the basis of body weight and starved for a minimum period of 24 hr prior to force feeding to reduce the variation associated with the estimate of TME.

The use of growth and liver aspartate aminotransferase to assess the effect of source of non-essential nitrogen on pyridoxine depletion, repletion and requirements of chicks.

1. Two experiments were carried out to study the relationship between growth, liver aspartate aminotransferase (Asp AT) and dietary pyridoxine to determine the pyridoxine requirement of chicks fed on diets containing crystalline essential amino acids with glutamic acid (GA) or diammonium citrate (DAHC) as the non-essential nitrogen source. 2. In one experiment purified diets containing isolated soy-protein with 0 or 3 mg pyridoxine/kg were used. The deficient chicks were significantly lighter, coverted food less efficiently and liver Asp AT activity was decreased. When deficient chicks were offered an adequate diet performance improved and Asp AT activity rapidly increased. 3. In the second experiment diets containing crystalline amino acids GA or DAHC combined with 0, 1 or 3 mg pyridoxine/kg (GA: 0, GA: 1, GA: 3, DAHC: 1, DAHC:3) were used. Growth rates of chicks fed on GA: 1 and GA: 3 were similar, whereas chicks fed on DAHC: 1 were significantly lighter than those given DAHC: 3. The growth data indicated a pyridoxine requirement for chicks fed on the GA diets of not more than 1mg/kg and of more than 1 mg/kg in those fed on diets containing DAHC. Asp AT activity varied significantly with dietary content of pyridoxine but not with the nitrogen source. When Asp AT activity was used to assess pyridoxine requirements, there was nof difference between chicks fed on GA or DAHC diets.

Carbon-13 and oxygen-18 in dinosaur, crocodile, and bird eggshells indicate environmental conditions.

We have gathered, from the nests of dinosaurs, and living and fossil birds, some evidence of the environment in which these creatures lived. However, our isotope determinations suggest it will be impossible to resolve the problem as to whether the dinosaurs were warm-or cold-blooded from the oxygen and carbon isotopes content of their shells.