|Park, S - TX A&M UNIVERSITY|
|Birkhold, S - TX A&M UNIVERSITY|
|Ricke, S - TX A&M UNIVERSITY|
Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 30, 2003
Publication Date: January 30, 2004
Citation: Park, S.Y., Birkhold, S.G., Kubena, L.F., Nisbet, D.J., Ricke, S.C. 2004. Effects of high zinc diets using zinc propionate on molt induction, organs, and postmolt egg production and quality in laying hens. Poultry Science. 83:24-33. Interpretive Summary: In nature, chickens and other avian species undergo a natural process called molting, where feathers are lost, the reproductive tract shrinks, and the hens quit laying eggs; basically, the hens have a period of rest. This is followed by the growth of a new set of feathers, an increase in the size of the reproductive tract, and the beginning of a second cycle of egg production. In commercial egg production, older hens can be artificially induced to molt before the end of a first laying cycle, rested and enter into a second egg laying cycle. The most commonly practiced method of molt induction is by the withdrawal of feed for several days and a reduction in the length of time the hens receive light. This is an efficient method to induce a molt because it is management friendly, economically advantageous, and postmolt performance of the hens is satisfactory. However, the stress of induced molting has been shown to increase the risk of the hens becoming infected with Salmonella, a food borne bacteria that lives in the gut of chickens and other animals. It is estimated that up to 4 million people in the United States get sick from Salmonella each year, with about 25% of these illnesses caused by one particular group of bacteria called Salmonella enteritidis, which can get into the internal organs, including the ovaries, of laying hens and contaminate eggs that are consumed by humans. There is a need for alternative molting regimens that yield a second egg laying cycle with a high rate of production of high quality eggs without increasing the stress level of the laying hens and the risk of Salmonella enteritis contamination. Results of this study demonstrate that feeding a Zn propionate (1% zinc) supplemented diet can induce molt and a second laying cycle; however, additional research is needed to examine the effect of Zn propionate on Salmonella infection in laying hens.
Technical Abstract: This study was conducted to determine the ability of an alternative salt form of zinc (Zn propionate), to induce molt in 66 wk-old hens. The hens were randomly assigned to 4 treatment groups of 27 or 28 birds each, and either a) molted conventionally by feed withdrawal, b) 1% zinc as Zn acetate, c) 1% zinc as Zn propionate, or d) non-molted control for 9 days. Feed intake was significantly (P < 0.05) depressed in both zinc (Zn) acetate and Zn propionate hens when compared to non-molted control hens during the 9 days. Ovary weight of hens undergoing feed withdrawal, Zn acetate, or Zn propionate were not (P > 0.05) significantly different from each other, but all were significantly (P < 0.05) lighter than the ovary weight of non-molted control hens. Zinc concentrations in the kidney and liver were significantly (P < 0.05) increased in both Zn acetate and Zn propionate molted hens, when compared to either non-molted control fed hens or feed withdrawal molted hens. Bone ash was significantly (P < 0.05) increased in both Zn acetate and Zn propionate molted hens or non-molted control hens when compared to feed withdrawal molted hens. Over the entire 3-month postmolt period, there were no significant differences in interior egg qualities but egg weights from Zn propionate fed hens were significantly (P < 0.05) higher than egg weights from feed withdrawal treatment hens. The data of the current study demonstrated that feeding a Zn propionate (1% zinc) supplemented diet can induce molt.