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Title: EFFECTS OF BODY WEIGHT AND FEED ALLOCATION DURING SEXUAL MATURATION IN BROILER BREEDER HENS: 2. OVARIAN MORPHOLOGY AND PLASMA HORMONE PROFILES

Author
item RENEMA, R - UNIVERSITY OF ALBERTA
item ROBINSON, F - UNIVERSITY OF ALBERTA
item Proudman, John
item NEWCOMBE, M - SHAVER PLTRY BREEDNG FARM
item MCKAY, R - SHAVER PLTRY BREEDNG FARM

Submitted to: Journal Of Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Broiler breeder body weight is routinely controlled from an early age to reduce reproductive problems associated with genetic selection for growth. Overfeeding growth-selected poultry during reproductive development results in abnormal development of the ovary, which may cause an increase in the proportion of hatching eggs that will not produce chicks. This study examined the effects of body weight and nutrient intake on ovarian development and plasma reproductive hormones during the time when the ovary is most sensitive to overfeeding. Results showed that heavier hens had higher plasma levels of reproductive hormones than did lighter weight hens, suggesting more advanced ovary development. Results comparing hens fed freely with those restricted in feed consumption showed that energy balance may interact with body weight and age to establish a threshold for sexual maturation. Small birds on restricted feeding were found to have poorer ovary development than larger birds, likely resulting in poor egg production. These results provide evidence of a link between nutrition and reproduction. This information may be used by scientists and producers to design management practices which minimize the detrimental effects of small hens on egg production.

Technical Abstract: The effects of broiler breeder body weight (BW) and nutrient intake on ovary morphology and plasma reproductive hormone profiles were examined at photostimulation (PS) (21 wk) and at sexual maturity (SM) in Shaver Starbro pullets at target BW (STD) or either 20 percent heavier (HIGH) or lighter (LOW) in BW at PS. Birds were then either restricted-fed (RF) or ad libitum-fed (AL) between PS and SM. Blood samples were taken at 3 d intervals beginning at PS and profiles constructed for estradiol-17B, luteinizing hormone (LH), and follicle stimulating hormone (FSH) to examine the relationship between body size, feeding level, and reproduction. Reproductive traits were assessed following SM. The AL birds had more large yellow follicles at SM than did RF birds and a lower incidence of small follicle atresia (10.3 vs. 32.3). RF birds were slower to reach SM. Plasma estradiol-17B concentration was greater in HIGH than in STD or LOW birds at PS, suggesting more advanced ovary development in HIGH birds Following PS, plasma LH and FSH concentrations of AL birds increased to levels nearly double that of RF birds, indicating a role for nutrient intake with rate of reproductive development. Plasma LH and FSH concentrations remained elevated for a greater time period in RF birds, however, possibly due to factors limiting recruitment of large yellow follicles in these birds. This experiment demonstrated a modulation of reproductive hormone concentrations during sexual maturation by feeding level in conjunction with a sensitivity of the ovary to nutritional effects.