Force-feeding procedure and physiological indicators of stress in male mule ducks.

1. The effects of the force-feeding procedure and its different components on various physiological indicators of acute and chronic stress were investigated in male mule ducks before and during a 12-d cramming period. 2. The highest concentration of corticosterone were measured after injection of ACTH agonist, during the pre-experimental period when the ducks were still housed in collective floor pens and at the time of transfer. 3. During the cramming period, corticosterone measured before and after force-feeding did not differ significantly though there was a non-significant trend towards an increase in certain cases. 4. The different components of force-feeding, including manipulation, intubation, force-feeding with a standard or a large amount of food had no significant effect upon corticosterone concentrations. 5. There was no indication from ACTH agonist challenge either of a change in adrenal sensitivity or a change in its responsiveness. 6. The heterocyte-lymphocyte ratio measured before and at the end of the cramming period did not differ significantly. 7. In conclusion, we observed no significant indication that force-feeding is perceived as an acute or chronic stress by male mule ducks, in our experimental conditions. Nevertheless, it remains to be shown that their adrenocorticotropic axis is responsive to acute stressors.

Meat quality traits and muscle characteristics in high or low fear lines of Japanese quails (Coturnix japonica) subjected to acute stress.

1. The influence of acute stress before slaughter on muscle and meat quality was studied in adult male quail from lines divergently selected for long (LTI) or short (STI) duration of tonic immobility (TI) and from the unselected (C) control line. 2. When subjected to acute stress, birds from the long TI line responded differently to those of the control or the low fear lines. LTI birds exhibited: a higher plasma creatine kinase and a smaller increase in plasma corticosterone levels, a higher pHu and drip loss values for breast meat associated with no differences in L*a*b* colour values; a higher percentage of fast glycolytic myofibres (IIb) and correspondingly (correlate) higher glycolytic (activity) in the pectoralis major (PM) muscle, and consequently lower oxidative enzyme activity in the PM muscle. 3. It is concluded that acute stress affected muscle metabolism differently in the STI, C and LTI lines. Hence, selection for TI, which is correlated with underlying fearfulness, can indirectly lead to differences in meat quality.

Prevention of incubation behavior expression in turkey hens by active immunization against prolactin.

The consequences of active immunization against prolactin on expression of incubation, reproductive performance and hormonal profiles were evaluated in turkey hens. Hens were injected weekly for 4 wk starting 8 wk before being submitted to a stimulatory photoperiod and 3 times thereafter at intervals of 4 to 5 wk. The hens were injected i.d. with 0.5 mL of a mixture diluted half in Freund's adjuvant. The mixture was prediluted in .9% saline and contained 100 micrograms of a fusion protein (GST-tPRL), GST, oPRL or vehicle. The results indicate that active immunizations with GST-tPRL or oPRL both induce production of specific prolactin antibodies. The onset of egg production was unaffected but higher egg production was observed for the GST-tPRL immunized hens. No GST-tPRL immunized hens expressed incubation behavior, whereas 20 to 30% of hens in the other experimental groups did so. Apparent hyperprolactinemia was detected by RIA for the GST-tPRL immunized groups starting before photostimulation and lasting until Week 10 of egg production but not in other groups. No significant differences were observed in either plasma LH or estradiol concentrations of immunized and nonimmunized turkey hens. In conclusion, both GST-tPRL or oPRL induced the production of antibodies against prolactin in turkey hens. However, only active immunization using GST-tPRL induced higher antibody titers as well as full prevention of incubation behavior expression. Such a pharmacological approach is of great practical interest, although its uses need to be carefully evaluated under commercial conditions.

Prevention of the expression of incubation behaviour using passive immunisation against prolactin in turkey hens (Meleagris gallopavo).

The efficacy of injecting antibodies raised against turkey prolactin to prevent the expression of incubation behaviour has been investigated in turkey hens. Medium white turkey hens (n = 15 x 2) were injected three times weekly for 4 consecutive weeks starting on week 5 of egg production. The hens were injected im with a volume of 1 mL per injection for the 1st week and 0.5 mL thereafter, of normal rabbit serum or serum containing antibodies raised against turkey prolactin (Guémené et al, 1994a). None of the 15 passively immunised hens expressed incubation behaviour, whereas, more than half (53%) of the control hens did express it. Plasma prolactin concentrations observed in the two groups presented comparable profiles until week 9 and from week 19 of egg production onward. Differences were, therefore, observed from week 10 until week 17 with the non immunised hens showing higher plasma prolactin concentrations than the immunised ones. This difference was related to the presence of incubating hens in the control group. A higher percentage of non immunised hens disrupted egg production during the course of the study and consequently immunised hens laid more eggs than the control ones. No change in plasma LH and oestradiol concentrations can be related to the immunisation procedure. We conclude that prevention of incubation behaviour can be achieved using passive immunisation against prolactin, prevention which resulted in more egg production under our experimental protocol.

Development and validation of a homologous radioimmunoassay using a biologically active recombinant turkey prolactin.

1. A new homologous radioimmunoassay has been developed for the measurement of turkey prolactin. 2. A 25000 kDa purified recombinant derived turkey prolactin (rtPRL), the biological activity of which was tested using a crop sac assay, was used as immunogen for the production of rabbit antiserum. In this biological test, the rtPRL was as active as the ovinePRL. 3. The radioligand (rtPRL) was labelled with 125I and the assay allowed the detection of standard doses of rtPRL ranging from 400 pg/tube to 50 ng/tube. 4. No cross reaction with chicken luteinising hormone and recombinant chicken growth hormone was detected. 5. The within and between assay coefficients of variability were 5.0 +/- 2.7% and 16.3%, respectively. The overall mean recovery ratio was 1.01. 6. The dose-response curves obtained with serial dilution of plasma and pituitary from turkey hens at different physiological stages and from male turkeys were parallel to those obtained with standard rtPRL. 7. The measured concentration of prolactin was 5 times higher in plasma from incubating than laying turkey hens, and the pituitaries from incubating hens contained 2 and 4 times more prolactin than those of laying and out of lay hens or males, respectively. 8. To further assess the validity of the assay, we measured changes in plasma concentration of prolactin in turkeys following stimulation with chicken vasointestinal peptide (cVIP). A single injection of 1 or 10 micrograms/kg body weight of cVIP to laying hens produced a large and rapid increase in plasma prolactin. 9. This new radioimmunoassay appears to be high for the measurement of turkey prolactin.