The present study was conducted to determine the adverse effects of high temperature and humidity not only on live performance and egg quality but also on immune function in commercial laying hens. One hundred eighty 31-wk-old laying hens at peak production were used in this study. Hens were housed in cages (15 cages of 4 birds/cage) in each of 3 environmental chambers and received 1 of 3 treatments. The 3 treatments were control (average temperature and relative humidity), cyclic (daily cyclic temperature and humidity), and heat stress (constant heat and humidity) for 5 wk. Different production and immune parameters were measured. Body weight and feed consumption were significantly reduced in hens in the heat stress group. Egg production, egg weight, shell weight, shell thickness, and specific gravity were significantly inhibited among hens in the heat stress group. Likewise, total white blood cell (WBC) counts and antibody production were significantly inhibited in hens in the heat stress group. In addition, mortality was higher in the heat stress group compared to the cyclic and control groups. Even though T- and B-lymphocyte activities were not significantly affected by any of the treatments, lymphocytes from hens in the heat stress group had the least activity at 1 wk following treatment. These results indicate that heat stress not only adversely affects production performance but also inhibits immune function.

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The livestock industries are a major contributor to the economy of the northeastern United States. Climate models predict increased average maximum temperatures, days with temperatures exceeding 25°C, and higher annual precipitation in the Northeast. These environmental changes combined with increased atmospheric CO 2 concentration are expected to either increase or decrease forage productivity depending on the crop, and may decrease protein content and forage digestibility. Winter damage to sensitive forage species may also increase. Predicted temperature increases are expected to reduce fertility in dairy cattle and heat stress-induced inflammation may limit energy available for productive functions.

Inhibition of microbial uricase in poultry manure is critical to reduce NH3 volatilization, because hydrolysis of uric acid by microbial uricase is the first step in the production of NH3 gas in poultry manure. Three experiments were conducted to evaluate the effects of minerals on uricase activity and NH3 volatilization from poultry manure. In Experiment 1, an in vitro enzyme assay was used to evaluate the effects of Zn, Cu, Mg, and Mn on the activity of microbial uricase. There were three treatments: uricase, uricase + minerals, and uricase preincubated with minerals. Uric acid concentration was measured at 293 nm with a spectrophotometer. The results indicated that Zn and Cu greatly blocked the activity of microbial uricase (>90% inhibition), whereas Mg and Mn were less inhibitory. Experiment 2 was designed to evaluate the effect of ZnSO4 on the growth of uric acid-utilizing microorganisms by an in vitro assay. There were three treatments: control, ZnSO4 (10 mM), and ZnSO4 (50 mM). The results indicated that ZnSO4 significantly reduced the number of uric acid-utilizing microorganisms compared to the control. In Experiment 3, an NH3-trapping system was used to evaluate the effect of different levels of ZnSO4 on NH3 volatilization and nitrogen retention in poultry manure. Poultry manure (300 g) was mixed with 0, 0.15, 0.3, 1.5, 3, or 6 g ZnSO4 to create manure concentrations of Zn at 0, 0.05, 0.1, 0.5, 1, or 2% (wt/wt), respectively. The 1 and 2% ZnSO4 treatments significantly increased manure uric acid and total nitrogen retention by reducing NH3 volatilization compared to the control during the 3-wk incubation.

This study was designed to evaluate the effect of chemical and enzymatic approaches to digest poultry feathers from dead birds for the purpose of recycling their nutrients as animal feeds. The experimental treatments were as follows: 1) control, 2) 24-h enzyme, 3) 24-h NaOH, 4) 2-h NaOH, and 5) 2-h NaOH and 24-h enzyme. The feather N solubilities of the control, 24-h enzyme, 24-h NaOH, 2-h NaOH, and 2-h NaOH and 24-h enzyme treatments were 0.91, 2.55, 78.83, 30.03, and 50.34%, respectively. The pepsin digestibilities of unsolubilized feather residues from the control, 24-h enzyme, 2-h NaOH, and 2-h NaOH and 24-h enzyme treatments were 4.67, 13.19, 55.83, and 59.08%, respectively. The in vitro amino acid digestibilities of the 2-h NaOH and 24-h enzyme treatment were significantly higher than the 24-h enzyme or 2-h NaOH (P < 0.05), except for alanine, whereas the 2-h NaOH treatment had significantly higher amino acid digestibility than the 24-h enzyme treatment (P < 0.05), except for methionine and histidine. Costs per kilogram of solubilized feather for the 24-h enzyme, 24-h NaOH, 2-h NaOH, and 2-h NaOH and 24-h enzyme treatments were $9.64, 4.72, 12.39, and 22.97, respectively. The results indicated that prolonged incubation with NaOH improved feather solubility, whereas further enzyme treatment after NaOH treatment increased feather solubility, pepsin digestibility, and in vitro amino acid digestibility.