Effect of delayed step-up lighting on plasma luteinizing hormone and reproductive function in broiler breeders

Changes in egg production rate induced by progesterone injection in broiler breeder hens

A polycystic ovarian follicle (PCOF) syndrome associated with high baseline concentrations of progesterone (P4) without preovulatory luteinizing hormone (LH) surges has been reported in turkey hens. The PCOF syndrome could be induced in turkey hens by injecting P4 (0.33 mg/kg per d) daily early in the reproductive period for 10 to 12 d and then waiting 3 wk for the syndrome to develop. It was hypothesized that an arrest in laying associated with the PCOF syndrome could be induced by daily injection of P4 in restricted-fed broiler breeder hens. Hens were divided into 5 treatment groups and were injected subcutaneously daily with P4 in canola oil at dosages of 0, 0.17, 0.33, 0.5, and 1.5 mg/kg per d for 13 d, at 14 wk of egg production when they were 41 wk of age. Blood samples were collected on d 7 and 13 immediately before P4 injection. Oviductal and ovarian morphologies were measured at necropsy 1 d after the last P4 injection. Egg production rate was reduced by injection of P4 at dosages < 0.17 mg/kg per d. At dosages of 0.5 and 1.5 mg/kg per d, ovarian hierarchical follicles had regressed. None of the broiler breeder hens had the PCOF syndrome at necropsy, but a high incidence of hens holding hard-shelled uterine eggs for several days was observed. Concentrations of LH decreased with P4 injection at > 0.17 mg/kg per d, and P4 concentrations were increased with P4 injection at > 0.5 mg/kg per d. Estradiol-17beta (E2) concentrations were decreased at all P4 dosages. It was concluded that egg production rate was reduced by daily injection of P4 at dosages > 0.17 mg/kg per d, and egg production ceased and ovarian follicles and the oviduct regressed at dosages > 0.50 mg/kg per d. The PCOF syndrome, however, was not induced in restricted-fed broiler breeder hens by P4 injection.

Preovulatory surge patterns of luteinizing hormone, progesterone, and estradiol-17β in broiler breeder hens fed ad libitum or restricted fed

Spontaneous ovulations are induced by preovulatory surges of luteinizing hormone (LH) and progesterone (P4) during ovulatory cycles in birds, but estradiol-17beta (E2) levels are relatively constant. Egg production is enhanced in restricted fed (RF) in comparison with ad libitum fed (FF) broiler breeder hens, but changes in concentrations and peripheral patterns of LH, P4, and E2 during ovulatory cycles in broiler breeder hens are poorly documented. The hypothesis of this study was that high resolution patterns of peripheral LH, P4, and E2 during preovulatory surges would not be different between FF and RF broiler breeder hens. Seven FF and 6 RF broiler breeder hens were photostimulated with 16 L:8 D at 22 wk of age. At 28 wk of age, the hens were cannulated for serial blood sampling and switched to a 24L:0D photoperiod to allow preovulatory surges of LH and P4 to run freely. Three days after cannulation, hens were serially bled every 12 min for 36 h. The FF hens were heavier than the RF hens (5.60 +/- 0.35 vs. 3.60 +/- 0.28 kg, respectively; P < 0.01). During the 10 d before cannulation, total egg production of the FF and RF hens (8.3 +/- 1.4 and 6.8 +/- 1.3 eggs, respectively; P = 0.08) and normal egg production (5.6 +/- 1.8 and 6.5 +/- 1.8 eggs, respectively; P = 0.37) were not different. The FF hens, however, had more abnormal eggs than the RF hens (2.7 +/- 1.7 and 0.3 +/- 0.8 eggs, respectively; P < 0.01). None of the hormonal measurements was different between the FF and RF hens (P > 0.05). The concentrations of hormones for the FF and RF hens, respectively, were as follows: baseline LH (2.79 +/- 0.45 vs. 2.94 +/- 0.60 ng/mL) and P4 (1.68 +/- 0.56 vs. 1.41 +/- 0.43 ng/mL), overall mean LH (3.18 +/- 0.45 vs. 3.10 +/- 0.46 ng/mL) and P4 (2.32 +/- 0.55 vs. 2.09 +/- 0.91 ng/ mL), preovulatory surge amplitude of LH (5.43 +/- 1.27 vs. 3.88 +/- 1.24 ng/mL) and P4 (6.08 +/- 2.09 vs. 6.71 +/- 3.91 ng/ mL), preovulatory surge duration of LH (7.52 +/- 1.80 vs. 5.74 +/- 3.18 h) and P4 (7.52 +/- 1.42 vs. 8.20 +/- 1.24 h), and overall mean E2 (0.25 +/- 0.05 vs. 0.23 +/- 0.05 ng/mL). In conclusion, there were no differences in total egg production or normal egg production between FF and RF broiler breeder hens, but the FF hens laid more abnormal eggs. Also, there were no differences in the concentrations or peripheral patterns of LH, P4, and E2 during preovulatory surges between the FF and RF broiler breeder hens.

Development of a cannulation procedure for broiler breeder hens

A cannulation and serial bleeding procedure has been developed to monitor the peripheral patterns of hormones associated with reproduction for up to 10 d in broiler breeder hens. Hens were cannulated via the jugular vein and returned to individual cages. The unrestrained cannulated hens were connected to a tether and swivel system that permitted constant infusion for maintenance of the cannula prior to serial bleeding and unrestrained long-term serial bleeding for up to 10 d. In a short-term experiment hens were bled every 12 min for 36 h, and in a long-term experiment hens were bled hourly for 10 d. In these experiments, 1.5-mL blood samples were collected at each time point with sodium citrate as the anticoagulant. To avoid hemodilution, after removal of plasma the red blood cells were reconstituted with saline to the original volume and returned to the hen of origin. Collection of serial blood samples was successful from 94% of hens in the short-term experiment and 79% of hens in the long-term experiment. Egg production was not affected (P > 0.05) during the 6 wk following serial bleeding in the short-term experiment. For hens that continued laying, egg production for 10 d prior to cannulation was not different (P > 0.05) from egg production for the 10 d during serial bleeding in the long-term experiment. However, late in the reproductive cycle many hens (25%) stopped laying when serially bled. It is concluded that this cannulation procedure can be used to study short-term or long-term peripheral patterns of hormones associated with oviposition and ovulation in laying broiler breeder hens.

Preovulatory luteinizing hormone surge interval in old and young laying turkey hens early in the egg production period

Egg production rate normally declines with duration of the reproductive period, but hen age and duration of the reproductive period are usually confounded. Initiation of egg production can be delayed in turkey hens with short-day lighting, allowing hen age to be separated from duration of the reproductive period. The objective of the present report is to determine if the interval between luteinizing hormone (LH) surges is different between old and young laying turkey hens during the peak of egg production. Turkey hens were given short-day lighting [6 h light (L):18 h darkness (D)] at 16 wk of age, and were photostimulated with 24L:OD (constant light) at 30 (young hens) or at 70 (old hens) wk of age. Egg production in the young hens started about 2 wk after they were photostimulated, but some of the old hens had started laying at 64 wk of age while under short-day lighting, and all old hens were laying after 1 wk of photostimulation. To monitor the interval between plasma LH surges at peak of production, hens were serially bled hourly for 240 h, starting about 6 wk after photostimulation. The interval of LH surges was not different between young (n = 5) and old (n = 10) laying hens. Not all LH surges were coincident with oviposition of eggs 1 to 2 d later (blind LH surges), and the percentage of young hens with at least one blind LH surge was higher than for old hens (60% of young hens and 10% of old hens). The baseline concentration of LH was not different between the young and old laying hens. In conclusion, the interval between LH surges, baseline concentration of LH, and amplitude of LH surges were not related to age of the hens during the peak rate of lay.