In order to estimate the possible contribution of heat increment of feeding (HIF) to thermoregulation in terms of enhancement of cold resistance, body surface (Ts) and rectal (Tr) temperatures, heart rate (HR) and shivering threshold were measured as diagnostic indices in fed and fasted growing broilers acutely exposed to the cold. Ts in fed and fasted birds decreased linearly with decreasing ambient temperature (Ta), but standard errors of Ts were, in most cases, greater in fed birds than in fasted birds. Tr in fed birds changed little, but that in fasted birds decreased with decreasing Ta ranging from 23 to 8°C. HR in fasted birds was much lower than that in fed birds at 26°C, changed little until 20°C and then increased steeply. On the other hand, HR in fed birds increased gradually with decreasing Ta. In fed birds, shivering was first observed at 17°C in all 4 birds while, in fasted birds, shivering was seen at 17°C in 2 out of 5 birds and at 14°C in the rest. Overall results indicated that feeding enhanced cold resistance, suggesting that HIF is used as a supplementary heat source for thermoregulation.

View full abstract

Effects of soybean protein isolate (SPI) and related nitrogen (N) sources on the serum and liver cholesterol concentrations were investigated in chicks. SPI was hydrolyzed by endo-and exo-type microbial proteases for 24h, and obtained hydrolysate (HYS) was further segmented to digested soluble fraction (DSF) and undigested fraction (UDF) by centrifugation. Seven-day-old chicks were fed experimental diets containing 0.5% cholesterol for 10 days. In the first experiment, various N sources including casein were added at the N level equivalent to 5% crude protein (CP) to the basal diet containing 20% CP. SPI and HYS were equally effective in lowering the serum and liver cholesterol concentrations as compared with casein. In contrast, DSF as well as amino acid mixture simulating SPI increased the serum and liver cholesterol concentrations. UDF had the strongest cholesterol-lowering action among the N sources tested in the first experiment. In the second experiment, 1.2% UDF added to the basal diet was as effective as 6.0% SPI in lowering the serum and liver cholesterol concentrations, but 0.6% UDF had little effect. Since the ratio of DSF and UDF was 9:1 on the weight basis, 6.0% SPI (5.1% as CP) contained 0.6% UDF (0.3% as CP). These results indicate that UDF is an important determinant in cholesterol-lowering effect of SPI, although UDF was not able to account entirely for the cholesterol-lowering effect of SPI.

View full abstract

To clarify the relationship between neuropeptide Y (NPY) and the α₂-adrenergic system on ingestive behavior of the young chick, NPY receptor and α₂-adrenoceptor were stimulated by intracerebroventricular injection of NPY and clonidine (CLON), α₂-receptor agonist, respectively. Central injection of NPY (1, 2.5 or 5μg) significantly increased food intake in a dose-dependent manner in Experiment 1. No additive or synergistic effect was observed when NPY (1μg) and CLON (50ng) were co-administered. However, a significant interaction between NPY (2.5μg) and CLON (50ng) was observed in food intake, implying that an enhanced food intake by NPY was attenuated by co-injection with CLON. These results indicate that α2-adrenoceptors and NPY may interact and regulate food intake within the central nervous system in the young chick, depending their concentrations.

View full abstract

By means of protein electrophoresis on 32 loci (22 enzymes), genetic variation and differentiation among 20 individual birds of 4 species of Gallus (Gallus gallus, G. lafayettei, G. sonneratii and G. varius), and the chicken were analyzed. A genealogic dendrogram was constructed by the UPGMA method, using the genetic distances among species. In the present study, G. varius and the chicken were shown to have genetic distance at the subspecies level, and genetic distance gradually increasing with the G. sonneratii, G. lafayettei and G. varius.

View full abstract

The laying performance and egg quality of layers, which received their the first duet during the period either from September, 1995 to February, 1996 (total 4 flocks, 17, 000 birds/flock; called 95 group for short) or from September, 1996 to February, 1997 (total 4 flocks, 17, 000 birds/flock; called 96 group for short), was analyzed in this paper, to explain the effect of body weight during rearing period on their following laying performance. Average body weight, at 17 weeks of age, was 60g heavier (about a gain of body weight for a week) in 95 group than in 96 group. Corresponding this, the age arrived at 50% egg production was earlier, rate of egg production was higher and average egg weight was heavier in 95 group than in 96 group, although there was no significant difference in feed intake. There was no significant difference in egg quality (Hough unit, yolk color fan score and shell thickness) between 95 and 96 groups. These results indicate that one of the points to achieve a higher performance in layer is to improve their growth during rearing period.

View full abstract