|Byrd, James - Allen|
|Nisbet, David - Dave|
Submitted to: Poultry Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/13/2004
Publication Date: 8/1/2004
Citation: Moore, R.W., Park, S.Y., Kubena, L.F., Byrd Ii, J.A., Mcreynolds, J.L., Burnham, M.R., Hume, M.E., Birkhold, S.G., Nisbet, D.J., Ricke, S.C. 2004. Comparison of zinc acetate and propionate addition on gastrointestinal tract fermentation and susceptibility of laying hens to salmonella enteritidis during forced molt. Poultry Science 83:1276-1286 Interpretive Summary: Forced molting of laying hens is a process by egg production is ceased and the reproductive tract is rejuvenated. After the molting period, reproductive function returns, allowing for multiple egg-laying cycles. The most common industrial means of inducing a molt is by the removal of feed from hens for a period of two weeks. However, this practice may increase Salmonella infections in the hens. This study sought to investigate the addition of Zinc acetate and Zinc proprionate to feeds as an alternative method to induce an effective molt in laying hens without increasing salmonella infection. Diets were introduced to hens over 50 wks of age and hens were dosed with Salmonella eneritidis after 4 days. The period of molt lasted 9 days, after which birds were killed and samples collected. All molting diets lead to decreased crop lactic acid content. Crop pH was higher in groups of low feed consumption. Liver, spleen, and ovary colonization of salmonella was lower in birds feed a normal ration and in birds feed zinc acetate as compared to non-fed molted hens. This study suggests that zinc acetate may be an acceptable alternative to feed deprivation that does not increase the risk of Salmonella infection.
Technical Abstract: The method most commonly used to induce molting and stimulate multiple egg-laying cycles in laying hens for commercial egg production is feed deprivation. Unfortunately, an increased risk of Salmonella enteritidis may result from the use of this method. Methods to stimulate multiple egg-laying cycles without increasing the risk of SE are needed. In each of three experiments, hens over 50 wk of age were divided into groups of 12 hens and placed in individual laying cages. One wk prior to dietary changes, hens were put on an 8-h light and 16 h-dark photoperiod that continued for the 9-day experiments. Individual hens in all treatments were challenged orally with 10,000 CFU of SE on the fourth day. Treatments were full fed hens (non-molted, NM), non-fed hens (molted, M), a zinc acetate diet (ZAC), and a zinc propionate diet (ZPR). The zinc diets contained 10,000 mg zinc per kg of diet. Body weight losses were significantly higher in the M, ZPR, and ZAC treatments than in the NM treatment. Ovary weights of ZAC or ZPR hens exhibited statistically (P > 0.05) the same level of reduction as those of NM hens (Trial 1 or Trial 2). Crop lactic acid decreased more in M, ZPR, and ZAC treatments than in NM hens. Crop pH was significantly (P < 0.05) lower in NM hens than M, ZAC, or ZPR hens (Trial 2) and crop pH tended to be inversely related to feed consumption. Although cecal individual or total VFA, and lactic acid were not significantly (P > 0.05) different between NM hens and M, ZAC or ZPR hens in Trial 1, cecal total VFA or lactic acid were significantly (P < 0.05) higher in NM hens than in M, ZAC or ZPR hens (Trials 2 and 3). Colonization of SE in the crop and the ceca was higher in the M and ZPR hens (Trials 1 and 2). Liver, spleen, or ovary invasion by SE was higher in the M and ZPR hens (Trials 1 and 2) for NM hens. At the zinc concentration used in these studies, the ZAC regimen may be effective for inducing molt and stimulating multiple laying cycles without increasing the risk of SE.