Supplementary Feeding of Grazing Inner Mongolian Cashmere Goats during Pregnancy—Based on “Nutrient Requirements of Cashmere Goats”

Simple Summary In the fall and winter, nutrient supplies of forage cannot meet the needs of pregnant cashmere goats, and there lacks clear precise supplemental feeding for them under grazing. This study first applied “Nutrient Requirements of Cashmere Goats” to supplementary feeding for pregnant Inner Mongolian cashmere goats under grazing. Supplementation increased pregnant goat cashmere length, cashmere yield, body weight after shearing, single born kid weight, twin-birth kid weight and kids’ mature secondary hair follicle density. The results demonstrated that the supplementary feeding based on the standard could enhance pregnant goats’ production performance. Abstract This study aimed to conduct precise supplementation for pregnant cashmere goats under grazing based on the feeding standard. Eight Inner Mongolian pregnant cashmere goats of near-average body weight were selected at early gestation (44.41 ± 4.03 kg) and late gestation (46.54 ± 4.02 kg) to measure their nutrient intake. Then, two pregnant cashmere goat flocks, No. 10 (control group, on-farm supplement) and No. 11 (supplemented group, supplement based on standard), with the same goat herd structure and grassland type, were chosen to conduct the supplemental feeding experiment. The results showed that pregnant cashmere goats lacked daily the intake of dry matter, digestive energy, crude protein and most essential mineral elements under grazing. After supplemental feeding, the supplementation based on the feeding standard increased the cashmere length and cashmere length growth volume and decreased the cashmere fineness, with no statistical significance. The goat cashmere yield, goat weight after shearing, single and twin-birth kid weight and kids’ mature secondary hair follicle density were significantly higher in the supplemented group (p < 0.05). In conclusion, supplementation in accordance with “Nutrient Requirements of Cashmere Goats” can enhance pregnant cashmere goats’ fiber production, growth performance, fertility and kids’ secondary hair follicles development, which is of great importance for the healthy and precise nutrition and management of cashmere goats.


Introduction
Cashmere goats are mainly distributed in Central Asia and Mongolia, especially in Western China [1]. Inner Mongolia cashmere goats are known worldwide for their highquality cashmere fiber; moreover, they are also raised locally for meat and milk products [2]. In traditional management, Inner Mongolia cashmere goats usually graze on a full grazing system with only forage as feed. It has been reported that the crude protein (CP) content of nature grasses decreases from 9.57%-21.26% to 2.58%-10.03% and neutral washing fiber (NDF) and acid detergent fiber (ADF) contents increase gradually from summer to the winter in the YiWei White Cashmere Goat Farm located in the Inner Mongolia Autonomous Region [3]. Moreover, the mineral element level in the soil-grazing-livestock ecosystem of the Stipa breviflora steppe located in the Inner Mongolia Siziwangqi Region is high in Fe, Mn and Ca, Stipa breviflora Griseb, Peganum harmala L and Oxytropis aciphylla Ledeb were the dominant plant species in natural pastures.
First, eight Inner Mongolian alba cashmere goats close to an average body weight were selected at early gestation (44.41 ± 4.03 kg, gestation 60 days) and late gestation (46.54 ± 4.02 kg, gestation 90 days). Moreover, the saturated alkanes were used as indicators to determine the forage nutrition intake [22,23]. Every experiment period was ten days. All goats were given one C 32 n-alkane capsule (48.5 mg, TARU, early gestation; 37.5 mg, CAU, late gestation) every morning before grazing. Moreover, 0.3 kg DM corn per goat was supplied after grazing at early gestation, with no supplementary feed at late gestation.
Then, two goat flocks, No. 10 (control group, on-farm supplementary feeding management) and No. 11 (supplemented group, supplementation based on standard, on-farm management), with the same goat herd structure and grassland type, were chosen to conduct the supplemental feeding experiment at early and late gestation. The composition and nutritional levels of the supplementation for the two groups are shown in Tables 1 and 2. Goats in the two experiments above were herded from 8:00 to 18:00.

Sample Collection and Chemical Analyses
In the forage dry matter intake (DMI) determination experiment, every kind of forage sample was collected from day 1 to day 5. Fecal samples were collected before and after grazing from day 6 to day 10 [24]. In addition, the supplemental corn sample was collected in early gestation. The concentrations of alkanes [25], GE (gross energy), CP, Ca, P, NDF and ADF in feces samples, forage samples and supplemental corn samples were determined [26], the content of other mineral elements (K, Mg, Co, Cu, Fe, Mn, Se, Zn and S) in each kind of eaten forage was determined [27,28].
In the supplemental feeding experiment, fifteen pregnant goats close to an average weight in two groups were selected randomly and respectively, and cashmere was collected before and after the supplemental feeding experiment, and cashmere length and cashmere fineness were determined [2]. After kids were born, production data of the two groups were gathered, their birthweights were measured and the kidding rate, single birth rate and twinning rate were calculated [29]. In April, the cashmere fibers were combed out from skin, and the cashmere yields and body weights of goats were determined after shearing. In the newborn kid, 15-days-old, the skin was sampled and stained, and hair follicles numbers were determined [2].

Calculation
After the forage DMI determination experiment, the forage intake proportion for pregnant goats can be calculated based on feces and forage C 27 -C 31 odd-chain alkane concentrations [22], and the recoveries of C 27 -C 31 chain alkanes were C 27 : 0.47, C 29 : 0.71 and C 31 : 0.69, respectively [30]. Forage DMI for goats at early and late gestation was calculated with Equations (1) and (2), respectively [23]: and the digestive energy (DE) intake of forage for goats at early and late gestation was calculated using Equations (3) and (4), respectively: During forage DMI determination experiment, goats were supplemented with corn after grazing in early gestation and supplemented with nothing in late gestation; Equations (3) and (4) were derived from DE = GE − FE [31]. Between Equations (3) and (4), for GE Forage , the GE level of forage eate, was the sum of the products of each forage eaten ratio, forage DMI (kg) and corresponding GE (MJ/kg); for DE Corn , the DE level of supplemental corn was the estimated as DE = 18.653 − 8.751ADF − 6.667NDF − 4.255CP [32]; FE was the products of feces output (kg) and fecal GE (MJ/kg), and the feces output was indirectly estimated from DMI and dry matter digestibility (DMD); DMD was estimated based on C 31 as an endogenous indicator [24].
Nutrient deficit and surplus are the gap between each nutrient intake of goats and the corresponding feeding standard. Moreover, forage nutrient intake is the sum of the product of each forage intake proportion and the corresponding forage nutrient (CP, Ca, P, K, Mg, Co, Cu, Fe, Mn, Se, Zn and S) content and forage DMI.

Statistical Analysis
The data of this experiment were analyzed via t-test analysis using SPSS 25.0 (IBM, New York, NY, USA), and the significance level was p < 0.05.

Nutritional Surplus and Deficit of Inner Mongolian Goats during Pregnancy under Grazing Conditions
Based on the concentration of alkanes in the feces and forage in early and late gestation (Supplementary Table S1), we first calculated the forage intake proportion. The cashmere goats mainly ate Stipa breviflora Griseb in early gestation under grazing (Figure 1), while lategestation grazing cashmere goats mainly ate Stipa breviflora Griseb with small amounts of Oxytropis aciphylla Ledeb, and eating ratios were 76.93% and 23.07%, respectively ( Figure 2). The nutritional surplus and deficit of goats in early and late gestation were calculated based on the forage intake ratio, forage nutrient content (Supplementary Tables S2 and S3) and forage DMI. Compared with the "Nutrient Requirements of Cashmere Goats", only the daily intake of Ca, Fe, Mn and Co in early gestation met the goats' requirements; the goats lacked the daily intake of DMI, DE, CP, P, Cu, Zn, K, Mg, Se and S ( Table 3). The calcium-to-phosphorus intake ratio was 7.82:1. Only the daily intake of Fe, Mn and Co in late gestation met the goats' requirements; the goats lacked the daily intake of DMI, DE, CP, Ca, P, Cu, Zn, K, Mg, Se and S ( Table 3). The proportion of calcium and phosphorus intake was 7.29:1.

Supplementation Based on the Standard can Enhance Pregant Cashmere Goat Production Performance
Supplemental feeding for 3 months according to the "Nutrient Requirements of Cashmere Goats" increased pregnant goats' cashmere length and cashmere length growth volume by 8.50% and 25.89% (p > 0.05) and decreased cashmere fineness by 4.12% (p > 0.05). In addition, supplementation according to the standard significantly increased cashmere yields in pregnant goats by 7.89% (p < 0.01) ( Table 4).

Supplementation Based on the Standard can Enhance Pregant Cashmere Goat Growth Performance
Supplemental feeding for 3 months according to the "Nutrient Requirements of Cashmere Goats" could significantly increase the body weights of cashmere goats after shearing (p < 0.01), with an increase of 5.71% compared to that in the control group (Table 5).

Supplementation Based on the Standard can Enhance Pregant Cashmere Goat Fertility
After supplemental feeding according to the "Nutrient Requirements of Cashmere Goats", the kidding rates of the supplemented and control groups were 112.10% and 114.29%, single birth rates were 88.31% and 85.71% and twinning rates were 11.29% and 14.29%, respectively (Table 6)The supplementation based on the standard significantly increased the kid birth weight, single-born kid weight (p < 0.01) and twin-birth kid weight (p > 0.05) by 3.99%, 4.29% and 0.38% (Table 7), respectively.

Supplementation Based on the Standard can Enhance Hair Follicle Development in Kids
After the supplemental feeding for 3 months according to the "Nutrient Requirements of Cashmere Goats", we sampled and stained the skin of newborn kids, and the transverse section showed that more mature secondary hair follicles (SF) were found in the supplemented group than in the control group (Figure 3). The longitudinal section showed that the SFs in the supplemented group were closer to the roots of the primary hair follicles (PF), indicating that the SFs in the supplemented group were in a better state of development than those in the control group (Figure 4). ments of Cashmere Goats", we sampled and stained the skin of newborn kids, and the transverse section showed that more mature secondary hair follicles (SF) were found in the supplemented group than in the control group (Figure 3). The longitudinal section showed that the SFs in the supplemented group were closer to the roots of the primary hair follicles (PF), indicating that the SFs in the supplemented group were in a better state of development than those in the control group (Figure 4).
We compared PF densities, SF densities and S:P values in kids 15-days-old at birth and found no significant differences in PF, SF and S:P values, but the supplementation based on the standard significantly increased the mature SF density (p < 0.05) by 12.21% (Table 8).

Discussion
This study indicated that, compared with that in the "Nutrient Requirements of Cashmere Goats", the daily intake of DMI, DE, CP, P, Cu, Zn, K, Mg, Se and S of goats in early gestation under grazing conditions was not enough, and the goats in late gestation lacked Ca on this basis. The forage DMI at early gestation, 0.85 kg, in this study was similar to 0.83 kg for Inner Mongolia cashmere goats during the fattening period determined by Wenqi; both studies were carried out using the saturated alkane method [3]. In late gestation, the decrease in forage DMI may be caused by the decrease in forage palatability and increase in the NDF content of the pasture [33]. Similarly, Xinjiang fine-wool sheep has been reported in which intakes of ME and CP were 5.15 MJ/day·ewe and 85.8 g/day·ewe lower than the nutrient requirements of sheep under winter grazing conditions, respectively [34]. As mentioned above, the mineral element level in the soil-grazing-livestock ecosystem of the Stipa breviflora steppe located in the Inner Mongolia Siziwangqi Region was high in Fe, Mn and Ca, low in P, Na, K and Se, and seasonally deficient in Cu, Zn and S. Moreover, the result of the mineral element surplus and deficit in this study was similar with that in [4,5], and the results in our study are similar, except that cashmere goats were deficient in Ca intake in late pregnancy. On the one hand, the experimental animals in the two studies were different, and on the other hand, the Ca We compared PF densities, SF densities and S:P values in kids 15-days-old at birth and found no significant differences in PF, SF and S:P values, but the supplementation based on the standard significantly increased the mature SF density (p < 0.05) by 12.21% (Table 8).

Discussion
This study indicated that, compared with that in the "Nutrient Requirements of Cashmere Goats", the daily intake of DMI, DE, CP, P, Cu, Zn, K, Mg, Se and S of goats in early gestation under grazing conditions was not enough, and the goats in late gestation lacked Ca on this basis. The forage DMI at early gestation, 0.85 kg, in this study was similar to 0.83 kg for Inner Mongolia cashmere goats during the fattening period determined by Wenqi; both studies were carried out using the saturated alkane method [3]. In late gestation, the decrease in forage DMI may be caused by the decrease in forage palatability and increase in the NDF content of the pasture [33]. Similarly, Xinjiang fine-wool sheep has been reported in which intakes of ME and CP were 5.15 MJ/day·ewe and 85.8 g/day·ewe lower than the nutrient requirements of sheep under winter grazing conditions, respectively [34]. As mentioned above, the mineral element level in the soil-grazing-livestock ecosystem of the Stipa breviflora steppe located in the Inner Mongolia Siziwangqi Region was high in Fe, Mn and Ca, low in P, Na, K and Se, and seasonally deficient in Cu, Zn and S. Moreover, the result of the mineral element surplus and deficit in this study was similar with that in [4,5], and the results in our study are similar, except that cashmere goats were deficient in Ca intake in late pregnancy. On the one hand, the experimental animals in the two studies were different, and on the other hand, the Ca requirement of cashmere goats became greater into late gestation, and the Ca content in the pasture decreased. In addition, the goats' intake ratio of Ca and P in this study approached to 7:1, which reduced P absorption, further reducing the absorption of P and Ca [35]. The above results also show that it is necessary to supplement the cashmere goats in this study.
Cashmere or wool yield can be enhanced by supplementing with energy and protein [36][37][38]. Mineral elements are related to the cashmere yield, Zn showed a significant positive correlation with the cashmere percentage [39] and supplementation with 25 mg/kg DM Cu from copper sulfate or copper methionine can enhance cashmere production [40]. Cashmere length and cashmere fineness are relevant to energy, CP and mineral elements, while too much energy makes the cashmere get thicker and lose economic value [41]. Protein has no effect on cashmere fineness when protein levels meet the maintenance needs of goats [42]. Usually, cashmere fibers reached their finest at medium protein and low energy levels [43]. It was reported that supplementation with 20 mg/kg DM (total dietary Cu level of 25.6 mg/kg DM) can promote cashmere growth [44]. However, in this study, the cashmere length increased and the lower cashmere fineness were not statistically significant. A similar result has been reported; under grazing conditions, pregnant Inner Mongolia cashmere goats were supplemented with 9.73 MJ/kg DE + 9.9% CP in the early stage (1st December-1st February) and with 9.46 MJ/kg DE + 9.52% CP in the later period (1st February-31st March), which significantly increased the cashmere yield of goats, but had no statistical effect on cashmere length and cashmere fineness [45]. This is perhaps because the supplementary feeding experiment was performed in a non-increasing period and the secondary hair follicles of Inner Mongolian cashmere goats were in a state of relative 'rest' (telogen) during this period (December to March), when the hair shaft gradually stopped growing and shed [46]. These results indicate that cashmere production performance can be enhanced by the supplementary feeding of pregnant cashmere goats according to the feeding standard, and compared with on-farm supplementary, a supplementary feeding scheme is reasonable.
In Liaoning cashmere goats, studies showed that growth traits are closely related to the cashmere yield, and body weight had the greatest direct effect on the cashmere yield [47]. Similarly, Rayeni cashmere goat total fleece weight increased by 45 g and postweight after shearing was enhanced by 1.5 g after supplementation with a 10.12 MJ/kg diet during pregnancy and lactation periods [48]. It was reported that there is a significant effect of ewe weight on lamb weight [49], and the single and twin-birth kid weight was also increased due to supplementation in this study. Similarly, Ewes' liveweight gain significantly increased by 134 g/day and lamb birth weights were significantly enhanced by 1 kg, with a supplement of 150 g cottonseed meal + 50 g molasses daily for mediumwooled Peppin Merino ewes during late gestation (last 4 weeks) [50]. Palm kernel cake (PKC) provides a protein source in a supplement (comprising 35% crushed maize, 30% rice bran, 32% PKC, 2% vitamin mineral premix and 1% salt), and supplementation at 0.5% of the live weight significantly enhanced the weight by 0.93 kg after 82 days of the feeding trial for Boer × local female goats (12.4 ± 2.6 kg, 7-9 months) [51]. In addition, supplementation of ewes with Zn, Se and Co in late gestation improved the mineral status of ewes and their kids before weaning and increased lamb weights [52,53]. These results suggested that supplementation based on the standard can enhance pregnant goats' growth performance and fertility. Studies showed that there is a positive relationship between the lamb birth weight and lamb growth rate [54], and we speculate that supplementation may have a sustained impact on the growth performance of offspring kids, which requires continuous follow-up to verify.
Supplementation based on the standard for pregnant cashmere goats enhanced the mature SF density of kids in this study. Similarly, kids' SF density can be increased significantly at 12.30 and 28.09 n/mm 2 with supplements of 5 g urea + 7.5 g Na 2 SO 4 and 250 g corn in cashmere goats during mid and late gestation, respectively [55]. It was reported that supplementation with Nano-Selenium (declared Se content 0.5 mg/kg DM daily) for cashmere goats during pregnancy can to promote the development and growth of fetal hair follicles [56]. In Angora goats, supplements provided to goats in the middle gestation and lactation stage had a positive effect on the SF density and SF number in kids at all ages after birth, increasing the S:P at 4, 6 and 15 months of age [57]. We speculate that supplementation may improve the hair follicle development of offspring lambs for a long time in this study, which requires continuous follow-up to verify.

Conclusions
In conclusion, offering a supplemental diet according to the standard could improve the cashmere production performance, growth and fertility of pregnant cashmere goats and improve secondary hair follicle development in their kids. Thus, we concluded that the supplementary feeding based on the standard could enhance pregnant cashmere goats' production performance, and the supplementary feeding effect is good. In the future, we can continue to track the growth performance and cashmere performance of the kids in the supplemented group and further explore the sustainable impact of maternal supplementary feeding on the offspring lambs. In addition, we will evaluate the nutrient intake of cashmere goats in other physiological stages under grazing conditions and provide precise supplementary feeding based on the standard.

Supplementary Materials:
The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/ani13030473/s1, Table S1: Concentrations of alkanes of forage, feces and corn during gestation (mg/kg DM); Table S2: Forage nutrient levels during gestation (dry matter basis); Table S3: Contents of mineral elements of eating grass during pregnancy (mg/kg DM).

Institutional Review Board Statement:
The study was conducted in accordance with guidelines of the Animal Care and Use Committee of China Agricultural University (Beijing, China).

Informed Consent Statement: Not applicable.
Data Availability Statement: Publicly available datasets were analyzed in this study, and these have been referenced in the manuscript.