Effects of photoperiod on nutrient digestibility, hair follicle activity and cashmere quality in Inner Mongolia white cashmere goats

Abstract

Objective: This study investigated the effects of photoperiod on nutrient digestibility, hair follicle (HF) activity and cashmere quality in Inner Mongolia white cashmere goats.

Methods: Twenty-four female (non-pregnant) Inner Mongolia white cashmere goats aged 1 to 1.5 years old with similar live weights (mean, 20.36±2.63 kg) were randomly allocated into two groups: a natural daily photoperiod group (NDPP group:10 to 16 h light, n = 12) and a short daily photoperiod group (SDPP group: 7 h light:17 h dark, n = 12). All the goats were housed in individual pens and fed the same diets from May 15 to October 15, 2015. The digestibility of crude protein (CP), dry matter (DM), and neutral detergent fiber (NDF) were measured in different months, along with secondary hair follicle (SHF) activity, concentration of melatonin (MEL), and cashmere quality.

Results: Although there was no significant difference in the live weights of goats between the SDPP and NDPP groups (p>0.05), the CP digestibility of goats in the SDPP group was significantly increased compared to the NDPP group in July, September, and October (p<0.05). For the DM and NDF digestibility of goats, a significant increase (p<0.05) was found during in September in the SDPP group. Furthermore, compared to the NDPP group, the SHF activity in July, the MEL concentration in July, and the cashmere fiber length and fiber weight in October were significantly increased in the SDPP group (p<0.05).

Conclusion: The cashmere production of Inner Mongolia white cashmere goats was increased without obvious deleterious effects on the cashmere fibers in the SDPP group (metabolizable energy, 8.34 MJ/kg; CP, 11.16%; short daily photoperiod, 7 h light:17 h dark).

Keywords: Cashmere Goat; Digestibility; Melatonin; Photoperiod; Secondary Hair Follicle.

Figure 1

Daylight lengths of different months in the NDPP and SDPP groups¹⁾. The goats in the SDPP group were housed in a dark shed (there was no light in the shed, and ventilators were used to circulate air) with less than 0.1 lux of opacity and good air conditions from 16:00 pm to 9:00 am daily (exposing the goats to 17 h of dark and 7 h of light (17 D:7 L). The goats in the NDPP group were housed outside the dark shed and were exposed to the natural photoperiod (exposing the goats to 10 to 16 h of light). The SDPP group’s shortened photoperiod treatment ran from May 15 to October 15, 2015. ¹⁾ Natural daily photoperiod group (NDPP group: 10 to 16 h light, n = 12), short daily photoperiod group (SDPP group: 7 h light:17 h dark, n = 12).

Figure 2

Effects of photoperiod on secondary hair follicle activity (magnification 100×) of goats in July, September, and October¹⁾. The horizontal axis means diferent months and the vertical axis means different groups. Skin samples from the edge of the scapula of all of the experimental goats were collected using a 1 cm diameter ring drill during July, September, and October. First, the skin tissue samples were rinsed with phosphate-buffered saline (pH = 7.4) and immediately placed in paraformaldehyde fixative solution (0.1 M, pH = 7.4). After 48 h, the skin tissue samples were dehydrated using an alcohol gradient, paraffin-embedded, and continuously sectioned at 6 μm. Then, the tissues were dyed by using the sapic method and subsequently examined using a Nikon microscope. Finally, each section had five images taken, and each specimen was observed under a Nikon microscope and an Instudio camera system. The total number of secondary hair follicles in 10 random fields was counted (magnification 100×), and the percentage of secondary hair follicle activity was calculated [7]. ¹⁾ Natural daily photoperiod group (NDPP group: 10 to 16 h light, n = 12), short daily photoperiod group (SDPP group: 7 h light:17 h dark, n = 12).