Cold climates may be a risk to the health and welfare of lambs during winter because cold environments alter the physiological processes of lambs, and we used cold environments with three different temperature gradients—an indoor heating control group (IHC) using electric heating; an indoor temperature group (IT) with intermittent and slight degrees of stimulation of coldness; an outdoor temperature group (OT) exposed to cold environments in an external natural environment. The results showed that the lambs in the OT group had a greater decrease in the average daily gain (ADG) and increase in the average daily feed intake (ADFI) and the feed-to-gain ratio (F:G) compared to the other two groups. The decrease in immunoglobulin A (IgA) and interleukin 2 (IL-2) contents and IL-2 gene expression, and the increase in tumor necrosis factor α (TNF-α) content and TNF-α and nuclear factor kappa-B p65 (NF-κB p65) gene expressions in the OT group suggested that the lambs had a compromised immune status in cold environments. Moreover, the decrease in catalase (CAT), glutathione peroxidase (GPx), total superoxide dismutase (T-SOD), and total antioxidant capacity (T-AOC) levels, and CAT, GPx, SOD1, SOD2, and nuclear factor-erythroid 2-related factor 2 (Nrf2) gene expressions, and the increase in malondialdehyde (MDA) in the OT group suggested that the lambs had a lower antioxidant defense capacity in cold environments. Thus, in extreme cold, lambs kept outdoors could reduce growth, immune function and antioxidant status. However, shelter feeding in winter could relieve the stress of cold environments on lambs, and housing with heating equipment was more conducive to the improve growth, immune, and antioxidant function of the lambs.

The photoperiod affects animals’ secretion of hormones, especially melatonin (MLT), which is involved in the regulation of the immune function and antioxidant status. The present experiment was conducted to study the effects of the photoperiod on MLT secretion, immune function, antioxidant status and related gene expression in goats. Eighteen adult female cashmere goats were randomly divided into three photoperiod groups: the control group (CG: natural photoperiod); the short-day photoperiod group (SDPP group: 8 h light; 16 h dark) and the shortening-day photoperiod group (SIPP group: lighting time shortened gradually from 16 h/d to 8 h/d). The experiment lasted for 60 days. The results showed that SDPP increased MLT concentration in serum at day 30 of the experiment (p < 0.05), but SIPP increased it at day 60 (p < 0.05). The activity of total superoxide dismutase (T-SOD), glutathione peroxidase (GPx) and catalase (CAT) increased (p < 0.05), and malondialdehyde (MDA) concentration decreased (p < 0.05) at day 30 in SDPP; no significant effects of SIPP were observed at day 30. Both SDPP and SIPP goats had higher activities of T-SOD, GPx and CAT (p < 0.05) at day 60. The concentration of immunoglobulin G (IgG), interleukin 1β (IL-1β) and interleukin 2 (IL-2) increased in SDPP (p < 0.05) at day 30. Both SDPP and SIPP raised the concentration of IgG, IL-1β and IL-2 at day 60 (p < 0.05). For the relative gene expression, the SDPP improved the gene expression of SOD1, CAT, GPx4, nuclear factor erythroid-2-related factor 2(Nrf2), IL-1β, IL-2 and tumor necrosis factor-α (TNF-α) (p < 0.05) in blood leukocytes at day 30. In addition, at day 60, goats in the SDPP group had a higher gene expression of CAT, GPx4, IL-1β and IL-2 (p < 0.05). Goats in SIPP had significantly higher gene expression of SOD1, CAT, GPx4, Nrf2, TNFα, IL-1β and IL-2 (p < 0.05) than those in CG. These results indicated that SDPP and SIPP could secrete more MLT and then improve the immune function and antioxidant status of the goats.

The growth of cashmere in goats was primarily influenced by natural photoperiod. However, whether artificially altering the photoperiod modified the rhythm of cashmere growth still required verification. In this study, the effects of photoperiod change on hormone secretion, hair follicle development, gene expression and skin antioxidant status of goats were studied in non-growth period of cashmere. Eighteen goats were randomly divided into three groups: control group (CG, natural photoperiod), short-day photoperiod group (SDPP, light 8 h/d, dark 16 h/d) and shortening photoperiod group (SPP, illumination duration gradually shortened from 16 h/d to 8 h/d). Experiment lasted for 60 days. Blood samples were taken weekly in first 30 days and every other day in last 30 days to determine hormone concentration. Skin samples were collected on 30 d and 60 d to determine hair follicle morphology, gene expression and skin antioxidant index. The results showed that SDPP and SPP increased the melatonin concentration on 34 d (p < 0.05) and 44 d (p < 0.05), and the epidermal growth factor concentration on 46 d (p < 0.05) and 50 d (p < 0.05), and the T3 concentration on 48 d and 56 d (p < 0.05), but decreased the prolactin concentration on 44 d (p < 0.05) and 56 d (p < 0.05), respectively. Additionally, on the 60 d, SDPP and SPP increased the depth of secondary hair follicle and the width of primary hair bulb (p < 0.05) and SPP increased the width of secondary hair bulb (p < 0.05). Furthermore, on the 60 d, SDPP up-regulated the β-catenin expression; SPP up-regulated the β-catenin, BMP2 and PDGFA expression (p < 0.05). Besides, on the 30 d, SDPP increased the activity of catalase (CAT) (p < 0.05) and decreased the content of malonaldehyde (MDA) (p < 0.05). On the 60 d, SPP increased the activities of total superoxide dismutase, both SDPP and SPP increased the activities of CAT and glutathione peroxidase (GPx) (p < 0.05), and decreased content of MDA in skin (p < 0.05). In addition, at 60 d, both SDPP and SPP up-regulated the gene expression of SOD1, GPx4 and CAT (p < 0.05). It can be seen that shortened the photoperiod affected the hair follicle activity by altering the secretion of hormone and mediating the expression of key genes, made hair follicle morphological changes. Meanwhile, short photoperiod improved the antioxidant capacity, created favorable conditions for cashmere growth.