Short-chain fatty acids (SCFA), which are widely used as food preservatives and are also present in the gastrointestinal (GI) tract of animals at high concentrations, may play a role in the persistence of Salmonella typhimurium in the environment. To test the hypothesis, S. typhimurium was adapted to SCFA for 1 h and the % survivors against various stress conditions was determined. For adaptation, the SCFA mixtures at the concentrations found in small (SI) and large intestine (LI) were used. The % survivors against extreme acid (pH 3.0), high osmolarity (2.5 M NaCl), and reactive oxygen (20 mM H 2 O 2 ) was greatly increased by exposure to SCFA LI, but to a much less extent by SCFA SI. The results suggest that encountering SCFA by S. typhimurium in the large intestine of the host food animal or food materials treated with them may increase the persistence of S. typhimurium in food animal preand postharvest production by enhancing overall stress resistance.

Zinc is an important nutrient in animal metabolism. In poultry, zinc serves not only as a nutrient but can also be used as a dietary supplement to manipulate the reproductive system of the bird. This article summarizes the general biochemistry, physiology, and nutritional aspects of zinc metabolism to provide a brief overview on what is known regarding zinc. The potential role of zinc in poultry immune response, Salmonella infection, and molting are emphasized.

This study was conducted to determine the ability of an alternative salt form of 1% Zn, 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: a) molted conventionally by feed withdrawal, b) 1% Zn as Zn acetate, c) 1% Zn as Zn propionate, or d) nonmolted control for 9 d. Feed intake was (P < 0.05) depressed in Zn acetate and Zn propionate hens when compared with nonmolted control hens during the 9 d. Ovary weights of hens undergoing feed withdrawal, Zn acetate, or Zn propionate were not (P > 0.05) different from each other, but all were (P < 0.05) lighter than the ovary weights of nonmolted control hens. Zinc concentrations in the kidney and liver were (P < 0.05) increased in Zn acetate and Zn propionate molted hens when compared with nonmolted hens on the control diet or hens molted by feed withdrawal. Bone ash values were (P < 0.05) increased for Zn acetate and Zn propionate molted hens or nonmolted control hens as compared with molted hens on feed withdrawal. Over the entire 3-mo postmolt period, there were no significant differences in interior egg qualities, but egg weights from hens fed Zn propionate were (P < 0.05) heavier than those from hens on feed withdrawal. The data of the current study demonstrated that feeding a Zn propionate (1% zinc)-supplemented diet can induce molt.

Feed deprivation is the most common method used to induce molting and stimulate multiple egg-laying cycles in laying hens for commercial egg production. Unfortunately, an increased risk of Salmonella enteritidis (SE) colonization 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 3 experiments, hens over 50 wk of age were divided into groups of 12 and placed in individual laying cages. One week before dietary changes, hens were put on an 8L:16D photoperiod that continued for the 9-d experimental period. Hens in all treatments were challenged orally with 10(4) cfu of SE on the fourth day. Treatments were full fed hens (nonmolted, NM), nonfed hens (molted, M), a zinc acetate diet (ZAC), and a zinc propionate diet (ZPR). The zinc diets contained 10,000 mg of zinc per kilogram of diet. Body weight losses were significantly higher in the M, ZPR, and ZAC treatments than in the NM treatment. Crop lactic acid decreased more in M, ZPR, and ZAC treatments than in NM hens in trial 2. Crop pH was significantly (P < 0.05) lower in NM hens than in M, ZAC, and ZPR hens in trial 2. Although cecal individual or total volatile fatty acids (VFA), and lactic acid were not significantly (P > 0.05) different between NM hens and M, ZAC and ZPR hens in trial 1, lactic acid was significantly (P < 0.05) higher in NM hens than in M, ZAC and ZPR hens (trial 2), and cecal total VFA were lower in M hens than in NM, ZAC and ZPR hens (trial 3). Colonization of SE in the crop and 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) than in NM hens. At the zinc concentration used in these studies, the zinc dietary regimens may be effective for reducing the risk of SE during induced molt.

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