This study aimed to investigate the effects of cold drinking water on cellular and humoral immunity in heat-exposed laying hens. One hundred and eight laying hens at 19 weeks old were placed into three treatments with six replicates of six hens in each group as follows: (1) hens were provided with normal drinking water (NW) under the control of thermoneutral temperature (CT: 25 ± 1 °C; CT + NW), (2) hens were provided with NW under high ambient temperature (HT: 35 ± 1 °C; HT + NW) for 8 h/d for a month, and (3) hens were treated under HT with cold drinking water (CW: 15 ± 1 °C; HT + CW) for 8 h/d for a 4-weeks. Then, the feed consumption, egg production, egg weight, feed conversion ratio, and blood immune parameters were investigated. The results showed that cold drinking water (CW) caused a significant (p < 0.05) recovery in the reduction of food intake and egg production due to heat stress; however, there was no significant effect (p > 0.05) on egg weight and feed conversion ratio. Moreover, CW significantly (p < 0.05) restored the immune-suppressing effects of heat stress on the contents of peripheral blood mononuclear cells, including B-cell (BU-Ia), helper T cell (CD4), and the ratio of helper/cytotoxic T cell (CD4/CD8). In addition, CW significantly (p < 0.05) recovered the reduction on the level of mRNA expression of interleukin-2 (IL-2) and interferon-gamma (IFN-γ), as well as significantly (p < 0.05) restored the reduction of plasma concentration of IL-2, IFN-γ and immunoglobulin G in heat-stressed laying hens. These results prove that CW increased heat dissipation and enhanced feed intake, egg production, and cellular and humoral immunity in heat-exposed laying hens.

| The objective of this study was to investigate effects of dietary fermented garlic powder (FGP) on productive performance and blood biochemical parameters of layer breeders. A total of 360 layer breeders (312 females and 48 males) were randomly divided into four dietary groups: 1) CON, basal diet; 2) FGP0.5, basal diet with fermented garlic powder at 0.5 g/kg; 3) FGP1.0, basal diet with fermented garlic powder at 1.0 g/kg, and 4) FGP2.0, basal diet with fermented garlic powder at 2.0 g/kg. FGP addition had no significant effect on egg production (EP) or egg weight (EW). However, eggs from groups fed a diet supplemented with FGP showed linearly (P < 0.05) higher hatchability (HAT) than those from the CON group fed a basal diet. Regarding blood parameters, serum concentration of albumin (ALB) was significantly (P < 0.05) higher in the group fed diets supplemented with FGP than in the CON group fed a basal diet. FGP supplementation quadratically (P < 0.05) increased serum total protein (TP) level. Aspartate amino transferase (AST), cholesterol (CHOL), and triglyceride (TG) concentrations were significantly (P < 0.05) decreased in the FGP2.0 group than in the CON group. Serum IL-2 level was significantly (P < 0.05) higher in the FGP2.0 group than in the CON group, although IL-6 level showed no significant difference. These findings suggest that dietary supplementation of FGP as a feed additive might improve productive performance and health of layer breeder hens.