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Postnatal development of the skin follicle population in the chinese alashan left banner white cashmere goat
Small Ruminant Research 185 (2020) 106087
Contents lists available at ScienceDirect
Small Ruminant Research journal homepage: www.elsevier.com/locate/smallrumres
Short communication
Postnatal development of the skin follicle population in the chinese alashan left banner white cashmere goat
T
Stefano Pallottia,*, Alessandro Valbonesia, Lou Yujieb, Yao Jiyuanb, Tang Peirongc, Marco Antoninid a
School of Bioscience and Veterinary Medicine, University of Camerino, Via Gentile III Da Varano, 62032 Camerino, Italy College of Animal Science and Technology of Jilin Agricultural Universty, Jilin, China c Station of Animal Breed and Improve of Alashan Left Banner, Inner Mongolia, China d Italian National Agency for New Technology, Energy and Sustainable Economic Development, ENEA Centro Ricerche Casaccia, Via Anguillarese, 301 00123 S.M. di Galeria, RM, Italy b
A R T I C LE I N FO
A B S T R A C T
Keywords: Hair Cycle Hair follicle Baby cashmere
The most precious textile fibre produced by the Chinese Alashan Left Banner White Cashmere goat is known as Baby Cashmere which is the hair produced during their first 6 months of life. This fleece is 1 μm finer than regular cashmere and nowadays is harvested by shearing the kids at 6 months of age. Seasonal variation in follicle activity was studied in the skin of eleven female goat kids born on January 2010 in the Station for Livestock Improvement of Alashan, Left Banner, Inner Mongolia (P.R. China) (latitude 38° 24′ N and longitude 104° 42′ E). Nine consecutive monthly skin biopsies (from March until November) were used to monitoring the number of active primary and secondary follicle and the number of inactive secondary follicles. The recorded data were used to calculate the percentage of inactive secondary follicles and the ratio of secondary to primary follicles. The number of active primary follicles showed low variability across the sampling period. On the contrary, the number of active secondary follicles decreased from March until June and then sharp increased until its maximum value in August when the kids were 7 months old. The percentage of inactive secondary follicles progressively increased from April to its maximum values in June when the goats were 5–6 months old. Then, the percentage was strongly reduced from July until October and finally has risen in the last observation in November. The ratio of secondary to primary follicle started to decrease from March and remained to its lower values until July when the kids were 6 months old. From July the ratio dramatically increased and gained its maximum values in August when the goats are 7 months old and finally slowly decreased until the last observation in November. The study suggests that goats born in January could shed the baby fiber between July and August, however, trials of combing are needed to assess whether or not the fleeces are actually shed.
1. Introduction Cashmere goat (Capra hircus) presents a double coat composed by two type of hair: the guard hair consisting in long, medullated and coarse hair, which provide mechanical protection, and the down hair, the cashmere fiber, consisting in short and fine hairs which provide thermal protection to the animal (Ibraheem et al., 1994). Primary hair follicles bear guard hair while the down coat hairs emerge from the secondary hair follicles which are more numerous than the first ones (Rogers, 2006). The hair follicle undergoes regular cycle of involution and regeneration throughout life, which follows a seasonal pattern controlled by changes in day length (Ryder, 1966; Dicks et al., 1994; ⁎
Ibraheem et al., 1994). This activity is characterized by three main stages: anagen (active growth), catagen (regression) and telogen (quiescence) (Nixon et al., 1991). In Inner Mongolia Cashmere goat breed, secondary hair follicles take approximately one year to complete a growth cycle. In fact, the anagen phase begins from April until November, the catagen phase goes from December until January, and the telogen phase starts from February until March (Li et al., 2008; Su et al., 2018). Many subpopulations are described for this breed (Di et al., 2011), one of which is the Chinese Alashan Left Banner White Cashmere goat, which produced a very fine cashmere (Bai et al., 2006; Pallotti et al., 2018). From 2009, this subpopulation is subjected to genetic improvement program
Corresponding author. E-mail address: [email protected] (S. Pallotti).
https://doi.org/10.1016/j.smallrumres.2020.106087 Received 15 October 2019; Received in revised form 2 March 2020; Accepted 5 March 2020 Available online 06 March 2020 0921-4488/ © 2020 Elsevier B.V. All rights reserved.
Small Ruminant Research 185 (2020) 106087
S. Pallotti, et al.
through a project coordinated by the Station for Livestock Improvement and supported by the Chinese Agricultural University of Jilin, the Italian University of Camerino, the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA) and the Loro Piana S.p.A. textile industry. The most precious textile fibre produced by the Chinese Alashan Left Banner White Cashmere goats during their first 6 months of life is known as Baby Cashmere. This is the hair from the first brushings of the kids so it can only be taken once. It only gives up about 30 g of fiber but is 1 μm finer than regular cashmere (Pallotti et al., 2020). Nowadays due to the lack of knowledge on the postnatal hair follicles physiology of this breed, baby cashmere is harvested by shearing the kids at 6 months of age, therefore the fiber is shorter and more contaminated with guard hair respect the combed cashmere. In order to standardize and correctly carry out the collection of this particular fibre, it will be necessary to understand the physiology of the fibre production in the Chinese Alashan Left Banner White Cashmere goat in consideration of the seasonality of the fibre production and the characteristics of fleece structure from birth until the first fall of the down. As one problem associated with the combing of the baby fleece is to detect the appropriate time of the year to achieve maximum production, the main objective of the study was to understand the cycle of the baby fibre production, the characteristics and the evolution of the skin/ follicular structure in yearling Chinese Alashan Left Banner White Cashmere goat.
series and embedded in paraffin. Transverse sections of 7 μm were cut with a rotary microtome and stained by using the Sacpic staining procedure, modify by Nixon (1993). This dyeing method reveals the follicular Inner Root Sheath (IRS) and the cellular layer of the Other Root Sheath (ORS), which are the main histological structure for defining skin follicular activity. The basic criteria for distinguishing an active from an inactive follicle is the presence of fibre and IRS. The level immediately under the sebaceous gland was defined as the most suitable depth for carrying out microscopic observations, because it contains the greatest number of detectable skin follicles and thus maximized the possibility of seeing the IRS. For each animals 16 hair follicle groups (defined as primary follicle trio with associated secondary follicles) were evaluated through the use of a calibrated ocular micrometer mounted on an optical microscope. This was the lowest number of hair follicle groups found in each biopsy which were observed in different transverse sections. The following parameters were recorded for each area: i) number of active primary follicles (P), ii) number of active secondary follicles (S), iii) the number of inactive secondary follicles (SI). The recorded data were used to calculate:
2. Materials and methods
2.3. Statistical analysis
2.1. Animals and sampling
Analyses of variance (ANOVA) were performed on the number of active primary follicles, number of active secondary follicle, the number of inactive secondary follicles, the total number of secondary follicle, the percentage of inactive secondary follicles, and the ratio of secondary to primary follicles data. A nested ANOVA was utilized, with the animal considered as random effect nested within the age. Differences between means were tested using the Benjamini-Hochberg Procedure (P < 0.05). All the statistical analyses were performed using SPSS version 12.0 statistical software.
• the percentage of inactive secondary follicles (Si%) • the ratio of secondary to primary follicles (S/P), which has been determined including both inactive and active S follicles.
Eleven female cashmere goat kids born on January 2009 were selected for the study. Since our observations have been carried out under extreme environmental and socio-economic situation it has not been possible to carry out the study on a larger sample. As previous observations suggest that there are no difference between mean S:P ratio of male and female yearling goats (Henderson and Sabine, 1991; Merchant and Riach, 1996), our sample was composed exclusively of female animals. Kids remained with their mothers until weaning at three months of age. The herd was located in the Station for Livestock Improvement of Alashan (latitude 38° 24′ N and longitude 104° 42′ E), Left Banner, a semi-desert steppe area of the Inner Mongolia (P.R. China). The original sampling herd at the Station counted 350 animals. Sampling started at March 2009, when the animals were two months old, and was repeated monthly till November 2009, when the animals were 11 months of age in order to monitor the skin follicular structure development over the 9 months. For collection of skin biopsies, trichotomy was performed using disposable stainless-steel blades. Skin biopsies were obtained after antisepsis, and local anesthesia with 2 % lidocaine was injected at the border of the sampling site. Using a disposable biopsy punch (8 mm diameter) one skin sample were taken from each animal from the right mid-side of the body (behind the scapula) as that specific area resulted representative of the individual fleece quality for sheep (Ryder and Stephenson, 1968). A final number of nine skin biopsies were extracted from each animal. To avoid the overlapping of any biopsies to the preceding one, we proceed the sampling starting from a common point behind the scapula and proceeding in anticlockwise direction for all the animals. The wound was treated with antiseptic to prevent infection. Skin samples were fixed in Bouin solution for 24 h and stored in 80° alcohol for shipping to Italy. Results from fleece samples analysis carried out for different yearling goats from the same herd were published by Pallotti et al. (2020).
3. Results 3.1. Active primary and secondary follicle and inactive secondary follicles ANOVA showed that number of active primary follicles was not significantly influenced by the age (P = 0.20). (data not shown). As showed in the Table 1, low variability was found across the sampling period in fact the number of active primary follicles ranged from 2.85 (June) to 3.26 (September). On the contrary, the number of active secondary follicles was significantly influenced by the age of the animals (P < 0.05). Furthermore, the parameter showed high degree of variation in fact at the first month of the experiment (March) the number of active secondary follicles recorded was 33,30 and decrease progressively until June (16,94) when the animals were 5 months old. After June the value increased rapidly until August in which the number of secondary active follicles reached its maximum value of 42.38 and then, decrease again until November (26.76) when the goats were 10 months old Table.1). Similarly, to the number of active secondary follicles, the number of inactive secondary follicles also was significantly influenced by the age of the animals (P < 0.05). The parameter showed high degree of fluctuation during the experiment in fact the value ranged from 10.02 to 0.13 recorded in March and September respectively. The highest values have been reached in March, June and November (10.2, 7.38 and 9.83 respectively). August, September and October were the months in which the goats showed the lowest number of inactive secondary follicles (1.03, 0.13 and 0.17 respectively) (Table 1).
2.2. Laboratory analysis After storing, skin samples were dehydrated in a graded ethanol 2
Small Ruminant Research 185 (2020) 106087
S. Pallotti, et al.
Table 1 Means for skin follicle parameters recorded at different ages (mean ± SD). SAMPLING DATE
March 2009
April 2009
May 2009
June 2009
July 2009
August 2009
September 2009
October 2009
November 2009
AGE (MONTHS) PARAMETER P S Si Si% S/P
2
3
4
5
6
7
8
9
10
a
2.95 ± 0.79 33.30a ± 10 10.02a ± 7.4 17.35a ± 12.91 14.72a ± 5.19
a
3.19 ± 0.6 26.58b ± 7.9 2.86b ± 3.13 8.69b ± 10.55 9.29b ± 2.5
a
3.14 ± 0.65 20.13c ± 9.6 5.82b ± 3.6 24.31c ± 15.74 8.32b ± 2.85
a
a
2.85 ± 0.77 16.94c ± 6.95 7.38c ± 5.48 29.10c ± 16.11 8.66b ± 2.53
3.05 ± 0.86 19.41c ± 8.3 6.84b,c ± 7.13 25.21c ± 12.91 8.72b ± 2.2
a
3.15 ± 0.66 42.38d ± 11.9 1.03d ± 1.06 2.28d ± 3.57 13.82a,c ± 2.8
a
3.26 ± 0.84 41.85d ± 15.24 0.13d ± 0.44 0.32d ± 1.2 12.78c,d ± 2.12
a
3.19 ± 0.63 39.63d ± 11.45 0.17d ± 0.62 0.49d ± 1.83 12.51d ± 2.56
3.10 a ± 0.55 26.76a,b ± 11 9.83a ± 6.56 28.00c ± 19.48 11.80d ± 2.81
The results were analyzed by post hoc comparisons between group means. Means with different superscripts are significantly different at P≤0.05. P = number of active primary follicles; S = number of active secondary follicles; Si = number of inactive secondary follicles; Si%= percentage of inactive secondary follicles; S/P = the ratio of secondary to primary follicles.
The ratio of secondary to primary follicle (S/P) started to decrease from March (2 months of age) and remained to its lower values until July when the kids were 6 months old. The high S/P ratio at the age of two months and its following lowering, together with the reduction in the number of active secondary follicles recorded during the first fourfive months of observation, are evidences that the baby fleece is borne by kids since their birth (in January). In fact, the high value recorded in March may reflect a secondary follicles activity which starts during the fetal development and continues for several weeks after birth in response to low environmental temperature. As January is the coldest month in Alashan, with the mean temperature of −9 °C to −14 °C, we can assume that the fetal development of the undercoat is a specific trait for cold tolerance selected in this population. With the rising temperatures in April, a step-wise reduction of the S/P ratio was observed as a consequence of the decrease in secondary follicles activity. From July (6 months of age), changes in the secondary follicle population occurred again, in fact, the S/P ratio dramatically increased and gained its maximum values in August when the goats are 7 months old suggesting the growth of the new cashmere fiber. Finally, the S/P ratio slowly decreased until the last observation in November. This result is in agreement with previous studies on Scottish cashmere goat. In this breed the maximum mitotic activity occurs around the summer solstice, continues throughout July and August, and declining thereafter (Ibraheem et al., 1994). In the Chinese Alashan Left Banner White Cashmere goat, the strongly increase of the S/P ratio until August, indicates the growth of the new cashmere fiber at the age of 7 months. Similar to our observations, studies on Angora goats showed that the secondary hair follicles continue to maturate during the first six month of life (Dreyer and Marincowitz, 1967; Wentzel and Vosloo, 1975). Anyway, in this breed the kids show the greatest increase in S/P ratio within the first three months after birth, while we found the higher S/P ratio value at two months and thereafter from the 7 until the 9 months of age. The age for the complete development of secondary hair follicles recorded in our study is also different from that recorded for sheep breeds such as the Herdwick breed in which the secondary follicles are fully developed at one month after birth (Burns, 1954). Likewise, all the secondary follicles are fully developed at three months in both the Scottish Blackface (Burns, 1953) and at 4–5 months in Australian Merinos (Schinckel, 1955). It must be considered, however, that difference between studies may only reflect the infrequent nature of the sampling regimes.
3.2. Percentage of inactive secondary follicles (Si %)(Telogen) The parameter was significantly influenced by the age (P < 0.05). Histological observation showed that the secondary follicles inactivity was reduced from March (17.35 %) to April (8.69 %), then strongly increased until June to its maximum value (29.10 %) when the animals were 5–6 months old. Starting from June, the percentage of inactive secondary follicle in the 6 month old goats decreased to its minimum values recorded in August, September and October (2.28 %, 0.32 % and 0.49 %, respectively). Finally, the percentage heavily rose again to 28 % recorded in the last observation in November (Table 1). 3.3. Ratio of secondary to primary follicles (S/P) Assessment of production potential from secondary follicles may be expressed as a ratio of secondary to primary follicles (S: P ratio) as the parameter is not affected by the skin expansion due to the growing of the animal (when measuring in kids) (Henderson and Sabine, 1991). The S/P, determined including both inactive and active S follicles was significantly influenced by the age (P < 0.05). In March, the 2 months old goats showed high S/P value (14.72) which progressively decreased to its minimum values recorded in May, June and July (8.32, 8.66 and 8.72 respectively). The ratio strongly increased again from August (13.82) when the animals where 7 months old and remained high until the last observation in November, when it started to decrease (Table 1). 4. Discussion From our analysis, ANOVA showed that all the parameters were significantly influenced by the age. However, the number of active primary follicles is the only parameter not significantly influenced by the age. In fact, during the nine months of observation the number of active primary follicles showed low variability. Conversely, the number of active secondary follicle decreased from March until June when the kids were 5 months old and then sharp increased until its maximum value in August (7 months of age). As expected, this results clearly showed that the primary follicles number was established during fetal life (Han et al., 2018). The percentage of inactive secondary follicles (telogen) progressively increased from April to its maximum values in June when the goats were 5–6 months old. Then, the percentage was strongly reduced from July until October as the secondary hair follicles remained in anagen throughout the summer. Finally, the parameter has risen in the last observation in November due to the secondary follicles which have become quiescent and entered a new telogen phase. As the shedding process in the Cashmere goat occurs after the follicles enter the resting phase (Ryder and Stephenson, 1968), this result suggests that a first baby fibre shedding may occur from June to August when the kids are 5–7 months. Therefore, breeders could harvest the baby cashmere by combing the animals at that time.
5. Conclusion The study provides information on follicle characteristics and development in yearling Chinese Alashan Left Banner White Cashmere goat that can be used as a scientific base for the development of the baby cashmere industry. S/P ratio data suggest that goats born in January could shed the baby fiber between July and August. Trials of early combing between July and August are needed to 3
Small Ruminant Research 185 (2020) 106087
S. Pallotti, et al.
assess whether or not the fleeces are actually shed. The baby fleece harvested by combing could be longer and less contaminated with guard hair respect the sheared cashmere. Furthermore, it would be interesting to determine whether or not animals born at other times of the year, follow the developmental pattern of the skin follicle populations observed in our study.
Inner Mongolia cashmere goat. Asian-australas. J. Anim. Sci. 31 (3), 316. https://doi. org/10.5713/ajas.17.0115. Henderson, M., Sabine, J.R., 1991. Secondary follicle development in Australian cashmere goats. Small Rumin. Res. 4, 349–363. https://doi.org/10.1016/0921-4488(91) 90081-Z. Ibraheem, M., Galbraith, H., Scaife, J., Ewen, S., 1994. Growth of secondary hair follicles of the Cashmere goat in vitro and their response to prolactin and melatonin. J. Anat. 185 (Pt 1), 135. Li, Y.R., Fan, W.B., Li, C.Q., Yin, J., Zhang, Y.J., Li, J.Q., 2008. Histomorphology research of the secondary follicle cycling of Inner Mongolia cashmere goat. Sci. Agric. Sin. 41, 3920–3926. Merchant, M., Riach, D.J., 1996. Changes in the coat of cashmere goat kids of two different genotypes from birth to 13 months of age. Anim. Sci. 62 (2), 317–323. https:// doi.org/10.1017/S1357729800014636. Nixon, A.J., 1993. A method for determining the activity state of hair follicle. Biotech. Histochem. 60 (6), 316–325. https://doi.org/10.3109/10520299309105637. Nixon, A.J., Gurns, M.P., Betterid, K., 1991. Seasonal hair follicle activity and fibre growth in some New Zealand cashmere- bearing goats (Caprus hircus). J. Zool. 1991 (224), 589–598. https://doi.org/10.1111/j.1469-7998.1991.tb03787.x. Pallotti, S., Wang, J., Tang, P., Antonini, M., Lou, Y., Pieramati, C., Valbonesi, A., Renieri, R., 2018. Variability of fibre quality on chinese alashan left banner white cashmere goat. Ital. J. Anim. Sci. 17 (1), 53–56. https://doi.org/10.1080/1828051X.2017. 1350121. Pallotti, S., Valbonesi, A., Yujie, L., Peirong, T., Sarti, F.M., Mancinelli, A.C., Antonini, M., 2020. Changes in fleece characteristics of yearling Chinese alashan left banner white cashmere goat. Small Rumin. Res. 182, 1–4. https://doi.org/10.1016/j.smallrumres. 2019.10.015. Rogers, G.E., 2006. Biology of the wool follicle: an excursion into a unique tissue interaction system waiting to be re- discovered. Exp. Dermatol. 15 (12), 931–949. https:// doi.org/10.1111/j.1600-0625.2006.00512.x. Ryder, M.L., 1966. Coat structure and seasonal shedding in goats. Anim. Sci. 8 (2), 289–302. https://doi.org/10.1017/S000335610003467X. Ryder, M.L., Stephenson, S.K., 1968. Wool Growth. Academic Press, London. Schinckel, P.G., 1955. The post-natal development of the skin follicle population in a strain of Merino sheep. Aust. J. Agric. Res. 6, 68–76. https://doi.org/10.1071/ AR9550068. Su, R., Fan, Y., Qiao, X., Li, X., Zhang, L., Li, C., Li, J., 2018. Transcriptomic analysis reveals critical genes for the hair follicle of Inner Mongolia cashmere goat from catagen to telogen. PLoS One 13 (10), e0204404. https://doi.org/10.1371/journal. pone.0204404. Wentzel, D., Vosloo, L.P., 1975. Dimensional changes of follicles and fibres during preand postnatal development in the Angora Goat. Agroanimalia 7, 61–64.
Declaration of Competing Interest The authors declare no conflicts of interest. Acknowledgements The authors would like to thank the Loro Piana S.p.A. for their financial support. References Bai, J., Zhang, Q., Li, J., Dao, E., Jia, X., 2006. Estimates of genetic parameters and genetic trends for production traits of Inner Mongolian White Cashmere goat. Asianaustralas. J. Anim. Sci. 19, 13. https://doi.org/10.5713/ajas.2006.13. Burns, M., 1953. Observation on the follicle population of Black-face sheep. J. Agric. Sci. Camb. 43, 422–431. https://doi.org/10.1017/S0021859600057907. Burns, M., 1954. The development of the fleece and follicle population in Herdwick sheep. J. Agric. Sci. Camb. 44, 443–464. https://doi.org/10.1017/ S0021859600045305. Di, R., Farhad Vahidi, S.M., Ma, Y.H., He, X.H., Zhao, Q.J., Han, J.L., Guan, W.J., Chu, M.X., Sun, W., Pu, Y.P., 2011. Microsatellite analysis revealed genetic diversity and population structure among Chinese cashmere goats. Anim. Genet. 42, 428–431. https://doi.org/10.1111/j.1365-2052.2010.02072.x. Dicks, P., Russel, A.J.F., Lincoln, G.A., 1994. The role of prolactin in the reactivation of hair follicles in relation to moulting in cashmere goats. J. Endocrinol. 143 (3), 441–448. https://doi.org/10.1677/joe.0.1430441. Dreyer, J.H., Marincowitz, G., 1967. Some observation on the skin histology and fibre characteristics of the Angora goat (Capra hircus angoraensisi). S. Afr. J. Agric. Sci. 10, 477–500. Han, W., Li, X., Wang, L., Wang, H., Yang, K., Wang, Z., Wang, R., Su, R., Liu, Z., Zhao, Y., Zhang, Y., Zhang, Y., 2018. Expression of fox-related genes in the skin follicles of
4
Contents lists available at ScienceDirect
Small Ruminant Research journal homepage: www.elsevier.com/locate/smallrumres
Short communication
Postnatal development of the skin follicle population in the chinese alashan left banner white cashmere goat
T
Stefano Pallottia,*, Alessandro Valbonesia, Lou Yujieb, Yao Jiyuanb, Tang Peirongc, Marco Antoninid a
School of Bioscience and Veterinary Medicine, University of Camerino, Via Gentile III Da Varano, 62032 Camerino, Italy College of Animal Science and Technology of Jilin Agricultural Universty, Jilin, China c Station of Animal Breed and Improve of Alashan Left Banner, Inner Mongolia, China d Italian National Agency for New Technology, Energy and Sustainable Economic Development, ENEA Centro Ricerche Casaccia, Via Anguillarese, 301 00123 S.M. di Galeria, RM, Italy b
A R T I C LE I N FO
A B S T R A C T
Keywords: Hair Cycle Hair follicle Baby cashmere
The most precious textile fibre produced by the Chinese Alashan Left Banner White Cashmere goat is known as Baby Cashmere which is the hair produced during their first 6 months of life. This fleece is 1 μm finer than regular cashmere and nowadays is harvested by shearing the kids at 6 months of age. Seasonal variation in follicle activity was studied in the skin of eleven female goat kids born on January 2010 in the Station for Livestock Improvement of Alashan, Left Banner, Inner Mongolia (P.R. China) (latitude 38° 24′ N and longitude 104° 42′ E). Nine consecutive monthly skin biopsies (from March until November) were used to monitoring the number of active primary and secondary follicle and the number of inactive secondary follicles. The recorded data were used to calculate the percentage of inactive secondary follicles and the ratio of secondary to primary follicles. The number of active primary follicles showed low variability across the sampling period. On the contrary, the number of active secondary follicles decreased from March until June and then sharp increased until its maximum value in August when the kids were 7 months old. The percentage of inactive secondary follicles progressively increased from April to its maximum values in June when the goats were 5–6 months old. Then, the percentage was strongly reduced from July until October and finally has risen in the last observation in November. The ratio of secondary to primary follicle started to decrease from March and remained to its lower values until July when the kids were 6 months old. From July the ratio dramatically increased and gained its maximum values in August when the goats are 7 months old and finally slowly decreased until the last observation in November. The study suggests that goats born in January could shed the baby fiber between July and August, however, trials of combing are needed to assess whether or not the fleeces are actually shed.
1. Introduction Cashmere goat (Capra hircus) presents a double coat composed by two type of hair: the guard hair consisting in long, medullated and coarse hair, which provide mechanical protection, and the down hair, the cashmere fiber, consisting in short and fine hairs which provide thermal protection to the animal (Ibraheem et al., 1994). Primary hair follicles bear guard hair while the down coat hairs emerge from the secondary hair follicles which are more numerous than the first ones (Rogers, 2006). The hair follicle undergoes regular cycle of involution and regeneration throughout life, which follows a seasonal pattern controlled by changes in day length (Ryder, 1966; Dicks et al., 1994; ⁎
Ibraheem et al., 1994). This activity is characterized by three main stages: anagen (active growth), catagen (regression) and telogen (quiescence) (Nixon et al., 1991). In Inner Mongolia Cashmere goat breed, secondary hair follicles take approximately one year to complete a growth cycle. In fact, the anagen phase begins from April until November, the catagen phase goes from December until January, and the telogen phase starts from February until March (Li et al., 2008; Su et al., 2018). Many subpopulations are described for this breed (Di et al., 2011), one of which is the Chinese Alashan Left Banner White Cashmere goat, which produced a very fine cashmere (Bai et al., 2006; Pallotti et al., 2018). From 2009, this subpopulation is subjected to genetic improvement program
Corresponding author. E-mail address: [email protected] (S. Pallotti).
https://doi.org/10.1016/j.smallrumres.2020.106087 Received 15 October 2019; Received in revised form 2 March 2020; Accepted 5 March 2020 Available online 06 March 2020 0921-4488/ © 2020 Elsevier B.V. All rights reserved.
Small Ruminant Research 185 (2020) 106087
S. Pallotti, et al.
through a project coordinated by the Station for Livestock Improvement and supported by the Chinese Agricultural University of Jilin, the Italian University of Camerino, the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA) and the Loro Piana S.p.A. textile industry. The most precious textile fibre produced by the Chinese Alashan Left Banner White Cashmere goats during their first 6 months of life is known as Baby Cashmere. This is the hair from the first brushings of the kids so it can only be taken once. It only gives up about 30 g of fiber but is 1 μm finer than regular cashmere (Pallotti et al., 2020). Nowadays due to the lack of knowledge on the postnatal hair follicles physiology of this breed, baby cashmere is harvested by shearing the kids at 6 months of age, therefore the fiber is shorter and more contaminated with guard hair respect the combed cashmere. In order to standardize and correctly carry out the collection of this particular fibre, it will be necessary to understand the physiology of the fibre production in the Chinese Alashan Left Banner White Cashmere goat in consideration of the seasonality of the fibre production and the characteristics of fleece structure from birth until the first fall of the down. As one problem associated with the combing of the baby fleece is to detect the appropriate time of the year to achieve maximum production, the main objective of the study was to understand the cycle of the baby fibre production, the characteristics and the evolution of the skin/ follicular structure in yearling Chinese Alashan Left Banner White Cashmere goat.
series and embedded in paraffin. Transverse sections of 7 μm were cut with a rotary microtome and stained by using the Sacpic staining procedure, modify by Nixon (1993). This dyeing method reveals the follicular Inner Root Sheath (IRS) and the cellular layer of the Other Root Sheath (ORS), which are the main histological structure for defining skin follicular activity. The basic criteria for distinguishing an active from an inactive follicle is the presence of fibre and IRS. The level immediately under the sebaceous gland was defined as the most suitable depth for carrying out microscopic observations, because it contains the greatest number of detectable skin follicles and thus maximized the possibility of seeing the IRS. For each animals 16 hair follicle groups (defined as primary follicle trio with associated secondary follicles) were evaluated through the use of a calibrated ocular micrometer mounted on an optical microscope. This was the lowest number of hair follicle groups found in each biopsy which were observed in different transverse sections. The following parameters were recorded for each area: i) number of active primary follicles (P), ii) number of active secondary follicles (S), iii) the number of inactive secondary follicles (SI). The recorded data were used to calculate:
2. Materials and methods
2.3. Statistical analysis
2.1. Animals and sampling
Analyses of variance (ANOVA) were performed on the number of active primary follicles, number of active secondary follicle, the number of inactive secondary follicles, the total number of secondary follicle, the percentage of inactive secondary follicles, and the ratio of secondary to primary follicles data. A nested ANOVA was utilized, with the animal considered as random effect nested within the age. Differences between means were tested using the Benjamini-Hochberg Procedure (P < 0.05). All the statistical analyses were performed using SPSS version 12.0 statistical software.
• the percentage of inactive secondary follicles (Si%) • the ratio of secondary to primary follicles (S/P), which has been determined including both inactive and active S follicles.
Eleven female cashmere goat kids born on January 2009 were selected for the study. Since our observations have been carried out under extreme environmental and socio-economic situation it has not been possible to carry out the study on a larger sample. As previous observations suggest that there are no difference between mean S:P ratio of male and female yearling goats (Henderson and Sabine, 1991; Merchant and Riach, 1996), our sample was composed exclusively of female animals. Kids remained with their mothers until weaning at three months of age. The herd was located in the Station for Livestock Improvement of Alashan (latitude 38° 24′ N and longitude 104° 42′ E), Left Banner, a semi-desert steppe area of the Inner Mongolia (P.R. China). The original sampling herd at the Station counted 350 animals. Sampling started at March 2009, when the animals were two months old, and was repeated monthly till November 2009, when the animals were 11 months of age in order to monitor the skin follicular structure development over the 9 months. For collection of skin biopsies, trichotomy was performed using disposable stainless-steel blades. Skin biopsies were obtained after antisepsis, and local anesthesia with 2 % lidocaine was injected at the border of the sampling site. Using a disposable biopsy punch (8 mm diameter) one skin sample were taken from each animal from the right mid-side of the body (behind the scapula) as that specific area resulted representative of the individual fleece quality for sheep (Ryder and Stephenson, 1968). A final number of nine skin biopsies were extracted from each animal. To avoid the overlapping of any biopsies to the preceding one, we proceed the sampling starting from a common point behind the scapula and proceeding in anticlockwise direction for all the animals. The wound was treated with antiseptic to prevent infection. Skin samples were fixed in Bouin solution for 24 h and stored in 80° alcohol for shipping to Italy. Results from fleece samples analysis carried out for different yearling goats from the same herd were published by Pallotti et al. (2020).
3. Results 3.1. Active primary and secondary follicle and inactive secondary follicles ANOVA showed that number of active primary follicles was not significantly influenced by the age (P = 0.20). (data not shown). As showed in the Table 1, low variability was found across the sampling period in fact the number of active primary follicles ranged from 2.85 (June) to 3.26 (September). On the contrary, the number of active secondary follicles was significantly influenced by the age of the animals (P < 0.05). Furthermore, the parameter showed high degree of variation in fact at the first month of the experiment (March) the number of active secondary follicles recorded was 33,30 and decrease progressively until June (16,94) when the animals were 5 months old. After June the value increased rapidly until August in which the number of secondary active follicles reached its maximum value of 42.38 and then, decrease again until November (26.76) when the goats were 10 months old Table.1). Similarly, to the number of active secondary follicles, the number of inactive secondary follicles also was significantly influenced by the age of the animals (P < 0.05). The parameter showed high degree of fluctuation during the experiment in fact the value ranged from 10.02 to 0.13 recorded in March and September respectively. The highest values have been reached in March, June and November (10.2, 7.38 and 9.83 respectively). August, September and October were the months in which the goats showed the lowest number of inactive secondary follicles (1.03, 0.13 and 0.17 respectively) (Table 1).
2.2. Laboratory analysis After storing, skin samples were dehydrated in a graded ethanol 2
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Table 1 Means for skin follicle parameters recorded at different ages (mean ± SD). SAMPLING DATE
March 2009
April 2009
May 2009
June 2009
July 2009
August 2009
September 2009
October 2009
November 2009
AGE (MONTHS) PARAMETER P S Si Si% S/P
2
3
4
5
6
7
8
9
10
a
2.95 ± 0.79 33.30a ± 10 10.02a ± 7.4 17.35a ± 12.91 14.72a ± 5.19
a
3.19 ± 0.6 26.58b ± 7.9 2.86b ± 3.13 8.69b ± 10.55 9.29b ± 2.5
a
3.14 ± 0.65 20.13c ± 9.6 5.82b ± 3.6 24.31c ± 15.74 8.32b ± 2.85
a
a
2.85 ± 0.77 16.94c ± 6.95 7.38c ± 5.48 29.10c ± 16.11 8.66b ± 2.53
3.05 ± 0.86 19.41c ± 8.3 6.84b,c ± 7.13 25.21c ± 12.91 8.72b ± 2.2
a
3.15 ± 0.66 42.38d ± 11.9 1.03d ± 1.06 2.28d ± 3.57 13.82a,c ± 2.8
a
3.26 ± 0.84 41.85d ± 15.24 0.13d ± 0.44 0.32d ± 1.2 12.78c,d ± 2.12
a
3.19 ± 0.63 39.63d ± 11.45 0.17d ± 0.62 0.49d ± 1.83 12.51d ± 2.56
3.10 a ± 0.55 26.76a,b ± 11 9.83a ± 6.56 28.00c ± 19.48 11.80d ± 2.81
The results were analyzed by post hoc comparisons between group means. Means with different superscripts are significantly different at P≤0.05. P = number of active primary follicles; S = number of active secondary follicles; Si = number of inactive secondary follicles; Si%= percentage of inactive secondary follicles; S/P = the ratio of secondary to primary follicles.
The ratio of secondary to primary follicle (S/P) started to decrease from March (2 months of age) and remained to its lower values until July when the kids were 6 months old. The high S/P ratio at the age of two months and its following lowering, together with the reduction in the number of active secondary follicles recorded during the first fourfive months of observation, are evidences that the baby fleece is borne by kids since their birth (in January). In fact, the high value recorded in March may reflect a secondary follicles activity which starts during the fetal development and continues for several weeks after birth in response to low environmental temperature. As January is the coldest month in Alashan, with the mean temperature of −9 °C to −14 °C, we can assume that the fetal development of the undercoat is a specific trait for cold tolerance selected in this population. With the rising temperatures in April, a step-wise reduction of the S/P ratio was observed as a consequence of the decrease in secondary follicles activity. From July (6 months of age), changes in the secondary follicle population occurred again, in fact, the S/P ratio dramatically increased and gained its maximum values in August when the goats are 7 months old suggesting the growth of the new cashmere fiber. Finally, the S/P ratio slowly decreased until the last observation in November. This result is in agreement with previous studies on Scottish cashmere goat. In this breed the maximum mitotic activity occurs around the summer solstice, continues throughout July and August, and declining thereafter (Ibraheem et al., 1994). In the Chinese Alashan Left Banner White Cashmere goat, the strongly increase of the S/P ratio until August, indicates the growth of the new cashmere fiber at the age of 7 months. Similar to our observations, studies on Angora goats showed that the secondary hair follicles continue to maturate during the first six month of life (Dreyer and Marincowitz, 1967; Wentzel and Vosloo, 1975). Anyway, in this breed the kids show the greatest increase in S/P ratio within the first three months after birth, while we found the higher S/P ratio value at two months and thereafter from the 7 until the 9 months of age. The age for the complete development of secondary hair follicles recorded in our study is also different from that recorded for sheep breeds such as the Herdwick breed in which the secondary follicles are fully developed at one month after birth (Burns, 1954). Likewise, all the secondary follicles are fully developed at three months in both the Scottish Blackface (Burns, 1953) and at 4–5 months in Australian Merinos (Schinckel, 1955). It must be considered, however, that difference between studies may only reflect the infrequent nature of the sampling regimes.
3.2. Percentage of inactive secondary follicles (Si %)(Telogen) The parameter was significantly influenced by the age (P < 0.05). Histological observation showed that the secondary follicles inactivity was reduced from March (17.35 %) to April (8.69 %), then strongly increased until June to its maximum value (29.10 %) when the animals were 5–6 months old. Starting from June, the percentage of inactive secondary follicle in the 6 month old goats decreased to its minimum values recorded in August, September and October (2.28 %, 0.32 % and 0.49 %, respectively). Finally, the percentage heavily rose again to 28 % recorded in the last observation in November (Table 1). 3.3. Ratio of secondary to primary follicles (S/P) Assessment of production potential from secondary follicles may be expressed as a ratio of secondary to primary follicles (S: P ratio) as the parameter is not affected by the skin expansion due to the growing of the animal (when measuring in kids) (Henderson and Sabine, 1991). The S/P, determined including both inactive and active S follicles was significantly influenced by the age (P < 0.05). In March, the 2 months old goats showed high S/P value (14.72) which progressively decreased to its minimum values recorded in May, June and July (8.32, 8.66 and 8.72 respectively). The ratio strongly increased again from August (13.82) when the animals where 7 months old and remained high until the last observation in November, when it started to decrease (Table 1). 4. Discussion From our analysis, ANOVA showed that all the parameters were significantly influenced by the age. However, the number of active primary follicles is the only parameter not significantly influenced by the age. In fact, during the nine months of observation the number of active primary follicles showed low variability. Conversely, the number of active secondary follicle decreased from March until June when the kids were 5 months old and then sharp increased until its maximum value in August (7 months of age). As expected, this results clearly showed that the primary follicles number was established during fetal life (Han et al., 2018). The percentage of inactive secondary follicles (telogen) progressively increased from April to its maximum values in June when the goats were 5–6 months old. Then, the percentage was strongly reduced from July until October as the secondary hair follicles remained in anagen throughout the summer. Finally, the parameter has risen in the last observation in November due to the secondary follicles which have become quiescent and entered a new telogen phase. As the shedding process in the Cashmere goat occurs after the follicles enter the resting phase (Ryder and Stephenson, 1968), this result suggests that a first baby fibre shedding may occur from June to August when the kids are 5–7 months. Therefore, breeders could harvest the baby cashmere by combing the animals at that time.
5. Conclusion The study provides information on follicle characteristics and development in yearling Chinese Alashan Left Banner White Cashmere goat that can be used as a scientific base for the development of the baby cashmere industry. S/P ratio data suggest that goats born in January could shed the baby fiber between July and August. Trials of early combing between July and August are needed to 3
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assess whether or not the fleeces are actually shed. The baby fleece harvested by combing could be longer and less contaminated with guard hair respect the sheared cashmere. Furthermore, it would be interesting to determine whether or not animals born at other times of the year, follow the developmental pattern of the skin follicle populations observed in our study.
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