Effects of a semiochemical on feed conversion index and related indicators on fast-growing broilers housed during forty-two days.

Consequences of stress in poultry may be assessed through a wide range of parameters. A semiochemical named mother hen uropygial secretion analogue (MHUSA) is known to decrease stress in broilers. Because stress influences their feeding behavior, this trial has been built so as to test the influence of MHUSA on feed conversion index and related indicators. Two hundred forty chicks were placed into 24 similar crates (10 chicks per crate) at 1 d of age. After 35 d, chickens under MHUSA presented similar feed conversion index compared with control. A treatment effect was observed on both heterophil:lymphocyte ratio and corticosterone (MHUSA

Influence of a preen gland secretion on growth and meat quality of heavy broilers.

Preen gland secretions were obtained from several hens that were rearing their chicks and the content of these secretions was analysed. From these results, a synthetic analogue of the secretions was created (given the title Mother Hen Uropygial Secretion Analogue, or MHUSA, in this study). According to a blinded, controlled experimental design, heavy broilers (strain SASSO T56N) were reared from 1 day of age in an environment treated with either MHUSA or control. At 80 days the birds were slaughtered. Post mortemcarcass weight, abdominal fat and fillet weights were then measured. Colour, pH and yield were also measured as indicators of meat quality. Broilers exposed to MHUSA had both higher carcass weights and higher fillet weights compared with control-treated birds (P < 0.05). Abdominal fat, pH, water loss and colorimetry results were similar between the treatment groups at all time points (24 h and 6 days post mortem) and also after a cooking procedure. The meat from the MHUSA birds was less yellow compared with control. It is concluded that constant exposure to MHUSA from rearing until slaughter improves growth rate in broilers without significantly affecting meat quality.

Influence of a semiochemical analogue on growing performances and meat quality of broilers.

Stress in broilers may have severe consequences on the final product quality. A synthetic analogue of uropygial secretion of mother hens was isolated from poultry. This mother hen uropygial secretion analogue (MHUSA) was tested in farm conditions on broilers during 12 wk. The purpose of this trial was to estimate the influence of MHUSA on growing performances, meat characteristics after processing, and stress indicators of broilers. After the 80-d period, birds under treatment were heavier at 3 different weighing ages (P

Glucose-insulin relationships and thyroid status of cockerels selected for high or low residual food consumption.

The plasma glucose-insulin relationships and thyroid status were investigated in two lines of adult cockerels divergently selected for high (R+) or low (R-) residual food consumption (RFC). For a given body weight, R+ birds had a 74% higher food intake than R- birds. Plasma glucose concentrations were significantly lower in the R+ line compared with the R- when fasted, whereas R+ birds exhibited a significantly lower plasma insulin concentration than R- birds either in fed or fasted state. After an overnight fast, R+ birds also exhibited a higher sensitivity to exogenous insulin in view of its more pronounced hypoglycaemic effect. After an oral glucose load, the glucose disposal of R+ cockerels was faster despite lower glucose-induced plasma insulin concentration. Whilst plasma triacylglycerol concentrations were lower in the R+ line when fed, plasma non-esterified fatty acid concentrations were higher in fasted R+ than R- cockerels (684 v. 522 mumol/l). Higher plasma triiodothyronine concentrations were observed in fed R+ compared with R- birds (3.0 v. 2.1 nmol/l respectively). The higher plasma concentrations of triiodothyronine associated with lower concentrations of insulin could account for the leanness and the elevated diet-induced thermogenesis previously observed in the R+ line.

Diet-induced thermogenesis in cockerels is modulated by genetic selection for high or low residual feed intake.

Energy balance of adult cockerels genetically selected for high (R+) or low (R-) residual feed consumption was investigated by using indirect calorimetry. Although no between-line difference was found in digestion of ingested energy, the true metabolizable energy (ME) intake was 40% greater in R+ than in R- birds. Basal heat production (HP) did not significantly differ between genotypes. Diet-induced thermogenesis (DIT) was significantly enhanced in R+ compared with R- birds, i.e., +84% when expressed as the difference in kilojoules of heat production determined in feed-deprived and fed cockerels, +31% when calculated as a percentage of ME intake (P < 0.01). The difference in DIT calculated from the regression between HP and physical activity explained 75% of the difference in HP; the remaining 25% could be explained by activity-related HP. The results cannot be explained by differences in the plasma concentration of circulating thyroid hormones: plasma thyroxine concentration did not differ between genotypes, whereas plasma triiodothyronine concentration was lower in feed-deprived R+ than in R- birds and indistinguishable in fed birds of the two lines. Heat production, however, was higher in the R+ line. Propranolol decreased HP only in the R+ line, suggesting a beta-adrenergic control of DIT at least in cockerels of this line. Plasma triglyceride concentration was lower in the R+ than in the R- line in fed cockerels, and plasma nonesterified fatty acid concentration was higher in the R+ than in the R- line in feed-deprived cockerels. These results are consistent with the leanness of the R+ compared with the R- line. The R+ and R- lines constitute an original model of diet-induced thermogenesis (DIT), a process that is under genetic control of appetite and allows R+ birds to balance all of their excessive energy intake without any adipose tissue storage.

A role for thyroid hormones in the regulation of diet-induced thermogenesis in birds.

The possible involvement of thyroid hormones in avian diet-induced thermogenesis (DIT) was investigated in two lines of cockerels divergently selected for high (R-) or low (R+) food efficiency. For a given body weight, R+ cockerels exhibited a higher food intake than R- cockerels (+49 to +76%) and increased DIT (+25%). Plasma thyroxine (T4) level did not differ between lines whatever the feeding status of the birds. Plasma 3,5,3'-triiodothyronine (T3) level was lower in fasted R+ than in fasted R- cockerels while the opposite was observed after a meal. Iopanic acid injections reduced both plasma T3 concentrations and heat production to the same levels in both lines. Hepatic 5'-deiodinase activity measured with an exogenous sulfhydryl group (dithiothreitol) did not differ between lines, but when the sulfhydryl group was omitted, the activity was higher in R+ than in R- birds (90 v. 42 pmol T3/min per liver). T3-binding capacity of isolated hepatic nuclei was higher (+76%) in R+ than in R- birds. Long-term or acute pair-feeding of R+ cockerels to the level of R- controls did not alter these results. The present results suggest that T3, mainly originating from peripheral conversion of T4 to T3, is involved in DIT in the R+ line. Availability of endogenous sulfhydryl groups appears to play an important part in the modulation of hepatic deiodinase activity. The higher concentration of nuclear T3 receptors may further increase the effects of the hormone, suggesting a major role of thyroid hormones associated with catecholamines in the stimulation of avian DIT. The underlying thermogenic mechanisms remain to be elucidated.

Hybrid ducks overfed with boiled corn develop an acute hepatic steatosis with decreased choline and polyunsaturated fatty acid level in phospholipids.

Hepatic and plasma lipid changes were investigated in hybrid ducks after steatosis was induced by overfeeding. Fourteen hybrid ducks were force-fed (11 kg corn in 13 days). The liver of the overfed ducks weighed ten times more than that of controls (695 vs 69 g). The phospholipid, ash, water and protein content of the liver were only slightly higher (2.6-, 3.6-, 4.4- and 3.2-fold, respectively) but the liver lipid concentration was 16.5 times higher after than before overfeeding (56.1 vs 3.4 g/100 g liver, respectively). Liver phosphatidylcholine concentration was higher in the control group (32.4 vs 22.9 mol/100 mol phospholipid) revealing a choline deficiency that could contribute to the development of liver steatosis. In liver phospholipid, the level of linoleic and arachidonic acids were markedly decreased in the overfed ducks, from 5 and 18.1 to 3.7 and 7.1 mol/100 mol fatty acids, respectively, and were mainly replaced by oleic acid. Plasma triacylglycerols increased 5.9-fold, cholesterol 2.2-fold and phospholipid 1.6-fold. Heat-induced (50 min at 105 degrees C) fat release, an index of poor liver integrity, was particularly high for the large, fat livers which contained low levels of phospholipids and phosphatidylcholine.