Abstract
The study aimed to examine the effects of 25-hydroxycholecalciferol (25-OH-D3) on reproductive performance and livability in broiler breeder hens. Hens at age of 26 wk were continued on restricted rations (R) or allowed ad libitum feeding (Ad) to 60 wk of age. Ad-feed intake greatly impaired egg production and hens' livability. The survival rate in both R- and Ad-hens was improved (86.7vs.78.9% and 48.2vs.29.1%, respectively) as was egg production in R-hens (P < 0.05) by inclusion of 69 μg 25-OH-D3/kg feedin the basal diet. Sudden death (SD) was the cause of hen mortality; hens died earlier with heavier BW and greater absolute and relative abdominal fat weights than surviving hens. Interestingly, feed intake of SD hens became less than that of surviving hens after 37 and 42 wk in Ad- and R-groups, respectively, and led to a progressive decline in SD hen BW with a ratio (relative to surviving hens of the same age) equaled 1 around 34 to 38 wk in Ad-groups and 52 to 53 wk in R-groups. Supplementation of 25-OH-D3 ameliorated untoward changes of heart and respiratory rate of Ad-survivors after 29 wk (P < 0.05), but had no significant effects on SD AD-hens. In contrast to the surviving counterparts, all SD hens experienced persistently higher respiratory rates in conjunction with declining heart rates (P < 0.05), suggesting compromised cardiac function as the cause of SD, in which hens increased heart and respiratory rate for more blood and oxygen supply to meet the need for rapid BW gain and/or adiposity in response to Ad-feed intake or due to genetically better feed efficiency even under R-feed intake. As the cardiorespiratory derangements advanced, compromised cardiac function ultimately led to heart failure and sudden death despite spontaneous reductions in feed intake and BW loss in all SD hens. Provision of 69 μg 25-OH-D3/kg feed is an effective and practical method to improve livability in broiler breeder hens.
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