Application of glycyrrhetinic acid in reducing reproductive toxicity of zearalenone to replacement gilts

Abstract

The invention discloses application of glycyrrhetinic acid in reducing reproductive toxicity of zearalenone to replacement gilts, and belongs to the technical field of animal breeding. Zearalenone can promote advanced development of internal and external reproductive organs such as uterus, ovary, vagina and the like, cause pathological changes of the reproductive organs, disturb the estrus cycle and the like to exert reproductive toxicity on the replacement gilts, so that the reproductive potential of the replacement gilts is influenced. By adding glycyrrhetinic acid into the replacement gilt feed, the development of the uterus, ovary and follicle of the replacement gilt can be promoted, the harm of ZEA to the ovary and uterus of the replacement gilt is reduced, and the estrus initiation of the replacement gilt is improved, so that the breeding potential of the gilt is improved, and the annual productivity of the replacement gilt is improved.

Description

Technical Field

[0001] The invention relates to the technical field of animal breeding, and in particular to an application of glycyrrhetinic acid in reducing the reproductive toxicity of zearalenone to gilts. Background Art

[0002] The annual productivity of gilts (PSY) is the ultimate goal pursued by the modern pig farming industry, and the high annual replacement rate of gilts and the cultivation of healthy gilts are important prerequisites for improving the PSY of gilts. In production, due to improper nutrition and feeding management of gilts, the health of gilts declines, resulting in an increase in the proportion of gilts that are not in estrus or delayed in estrus, increasing the annual replacement rate of gilts, thereby reducing the annual productivity of gilts.

[0003] Zearalenone (ZEA) is a non-steroidal mycotoxin with estrogenic activity produced by the genus Fusarium. It has a special affinity for estradiol receptors in the body and has been proven to be the most harmful to animal pig reproduction. ZEA is the most serious toxin that harms the reproductive performance of sows, especially gilts. ZEA in feed is biotransformed into more toxic metabolites through hydroxylation by hydroxysteroid dehydrogenase (HSD) in the animal body. ZEA and its metabolites can cause hormone secretion disorders in gilts, leading to abnormal development of internal and external reproductive organs such as the uterus, ovaries, and vagina, affecting the estrus cycle of gilts, thereby harming the reproduction of gilts.

[0004] At present, the main methods for mycotoxin detoxification include physical methods, chemical methods and biological methods. Physical detoxification includes the use of methods such as adding mildew inhibitors and mycotoxin adsorbents, radiation, heating and pressurization, microwave treatment and cleaning of raw materials to prevent or reduce mycotoxins. However, when adsorbents are used, excessive addition can easily adsorb vitamins and other nutrients in feed, reduce the nutritional value of feed, and cause secondary pollution problems such as heavy metals and other harmful substances due to rough production and processing methods; γ irradiation has high penetration and good treatment effect, but its radioactivity greatly limits the application of mycotoxin degradation in food. Ultraviolet irradiation has limited penetration and mainly acts on the surface of materials. The treatment time is long and the production capacity is low. The toxicity of degradation products is difficult to evaluate, and there are certain safety hazards in operation; although chemical detoxification is very effective and the mycotoxin removal rate is very high, its implementation conditions are relatively harsh, and the removal effect of trace and difficult-to-separate toxins is not obvious. Moreover, these methods, especially when using organic reagents, will introduce new pollutants and cause secondary pollution; the degradation efficiency and actual effect of biological methods have not been particularly investigated, and there is still the problem of unclear degradation products. Therefore, it is urgent to develop a simple and efficient method for detoxification of zearalenone.

[0005] Glycyrrhetinic acid (GA), a Chinese herbal extract, has estrogen-like effects and is an inhibitor of steroid dehydrogenase (HSD), a key enzyme in the production and metabolism of steroid hormones in the body. In addition, GA has multiple functions such as detoxification, liver protection, immunity enhancement, and anti-oxidation. So far, there are few reports on the effects of GA on the reproductive performance of gilts and the mechanism of estrus initiation. Summary of the invention

[0006] In order to solve the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide an application of glycyrrhetinic acid in reducing the reproductive toxicity of zearalenone to gilts, so as to provide a simple and efficient method for detoxification of zearalenone.

[0007] The technical solution of the present invention to solve the above technical problems is as follows: provide an application of glycyrrhetinic acid in reducing the reproductive toxicity of zearalenone to gilts, wherein the reproductive toxicity refers to the fact that zearalenone can cause abnormal development of reproductive organs and estrus disorders in gilts.

[0008] Furthermore, abnormal development of the reproductive organs includes enlarged and shortened uterine horns, a reduced number of uterine loops, and a thickened and chondrogenic cervix in gilts.

[0009] Furthermore, abnormal development of reproductive organs also includes atrophy of the ovaries of gilts; reduced ovarian weight; and a decrease in the number of large follicles, medium follicles, and healthy mature follicles in the ovaries.

[0010] Furthermore, estrus disorders include early onset of estrus and prolonged estrus cycles in gilts.

[0011] Furthermore, adding glycyrrhetinic acid to gilt feed can reduce the gilt's weight at first estrus, advance the initial age, and reduce the back fat thickness at first estrus, which can promote the timely estrus of sows.

[0012] Furthermore, adding glycyrrhizic acid to the gilt diet can promote the development of the gilt's uterus, significantly increase the weight of the uterus, increase the number of uterine loops, and significantly grow the left and right uterine horns.

[0013] Furthermore, adding glycyrrhizic acid to the gilt diet can significantly increase the ovarian weight and the number of follicles of gilts, and improve the quality of their ovaries and follicles.

[0014] The present invention also provides a method for reducing the reproductive toxicity of zearalenone to gilts, comprising adding 100-600 mg / kg of glycyrrhetinic acid to the gilt feed.

[0015] The present invention has the following beneficial effects: (1) The present invention can reduce the weight of gilts at the first estrus stage, advance the age at the initial stage and the back fat thickness at the first estrus stage by adding GA to the gilt feed, thereby promoting the timely estrus of gilts; GA can reduce the effect of ZEA on the reproductive performance of gilts and improve the initiation of estrus in sows poisoned by ZEA.

[0016] (2) The present invention can improve the harm of ZEA to the uterine development of gilts by adding GA to the gilt diet, promote the development of the uterus of gilts, significantly reduce the weight of the uterus, increase the number of uterine loops, and significantly increase the left and right uterine horns; (3) The present invention can alleviate the harm of ZEA to the ovaries of gilts by adding GA to the gilt diet, significantly increase the ovarian weight of gilts and the number of follicles, and improve the quality of the ovaries and follicles of gilts. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The effect of GA on the uterus of gilts; Figure 2 This is the effect of GA on the ovary of gilts. DETAILED DESCRIPTION

[0018] The following examples are only used to explain the present invention and are not intended to limit the scope of the present invention. If no specific conditions are specified in the examples, the conditions are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0019] Example 1 Sample collection, determination index and method (1) Feeding method: A single-factor randomized experimental design was used. 80 healthy and well-conditioned long × long (LY) gilts of 165±7 days old and with an average body weight of 94.05±3.82 kg were selected and randomly divided into 4 groups with similar age and body weight, each with 20 gilts, including control group (CON group, basal diet), ZEA group (basal diet + 1 mg / kg ZEA), GA group (basal diet + 400 mg / kg GA), and ZEA+GA group (1 mg / kg ZEA + 400 mg / kg GA). Each group had 5 replicates, and each replicate had 4 gilts. The pre-test period was 5 days, and the experiment ended on the 19th day of the second estrus of the gilts. The basal diet for gilts was prepared according to the nutritional requirements of NRC (2012). Its composition and nutritional level are shown in Table 1. The feed was prepared once before the start of the experiment, and mildew inhibitors were added to the premix. The test feed was packed and stacked on wooden pallets and stored in a clean, cool, dry and ventilated place. The content of ZEA, vomitoxin (DON) and aflatoxin (AFB1) in each group of feed was detected by enzyme-linked immunosorbent assay (ELISA). The content of ZEA in each group of feed was 38.30, 1032.764, 31.41 and 1028.92 μg / kg, respectively. The content of DON and AFB1 in each group of feed met the limit requirements of the National Feed Hygiene Standard (GB 13078-2017).

[0020] Table 1 Basic diet composition and nutritional level (air-dried basis)

[0021] Note: ① The premix provides per kilogram of feed: VA 12000IU, VD3 2700, VE 48mg, VK3 2mg, VB12mg, VB2 5.4mg, VB6 2mg, VB12 0.02mg, folic acid 1.5mg, D-calcium pantothenate 13.5mg, niacin 20mg, biotin 0.3mg; Fe (ferrous sulfate) 150mg, Cu (copper sulfate) 35mg, Zn (zinc sulfate) 120mg, Mn 60mg, I 0.6mg, Se0.3mg. ② Digestible energy is calculated, and the others are measured values.

[0022] The experimental gilts were housed in units of one unit per replication. Restricted feeding (2.5 kg / d / head) was adopted, and drinking water was free. Boars were used to induce estrus twice every day at 9:30 am and 4:00 pm, and each induction lasted no less than 15 minutes. After the gilts reached puberty (the first standing reflex was used as the basis), the age at puberty, weight at puberty, and back fat thickness at puberty were recorded. The start time of the puberty period was recorded, and after the end of the puberty period, the gilts were continued to be raised until the 19th day of the second puberty period, weighed, measured for back fat thickness, and slaughtered after blood was collected. Other feeding management and immunization procedures were uniformly implemented in accordance with the regulations of the breeding farm.

[0023] (2) Sample collection: After blood collection at the end of the experiment, one pig was randomly selected from each replicate for slaughter. After the pig was killed, the uterus (including the uterine horns and cervix) was quickly removed and weighed, and the lengths of the left and right uterine horns were measured. The ovaries were quickly removed from the ends of the fallopian tubes, then weighed, the lengths of the left and right fallopian tubes were measured, and the number of follicles on the left and right ovaries was calculated.

[0024] (3) Measurement indicators and methods ① Determination of reproductive performance: record the age at first estrus, body weight at first estrus and back fat thickness of gilts, and calculate the average daily weight gain (ADG), average daily feed intake (ADFI) and feed-to-meat ratio (F / G) during the whole period.

[0025] ② Determination of uterine and ovarian indicators: After the gilts are slaughtered, they are quickly dissected and the uterine and ovarian tissues are removed. The uterus is weighed, and the length of the uterine horns and fallopian tubes is measured. The left and right ovaries are removed, the ovaries are weighed, and the number of large ovarian follicles (diameter > 5mm), the number of medium follicles (diameter 1-5mm), and the number of healthy follicles are counted. The follicles are grouped according to their quality: A. Healthy follicles: The follicular wall structure is complete, uniform, and tight, slightly pink or yellow, the capillaries are evenly distributed and bright red, the follicular fluid is clear, and the cumulus ovum can generally be seen; B. Early atretic follicles: The follicular wall structure is relatively uniform, but the inner layer is slightly flocculent, or there are a small number of dark patches on the wall. The follicles are slightly grayish white with fewer blood vessels or larger blood vessels and lighter color. The follicular fluid is slightly turbid, and the cumulus ovum can be seen in a few cases; C. Late atretic follicles: The follicular wall structure is uneven, grayish in color, with fewer capillaries, severe internal flocculence, or dark clumps can be seen inside the follicles, and the cumulus ovum is generally not visible.

[0026] (3) Data processing and statistical analysis: The experimental data were statistically processed using SPSS 19.0 statistical software. The results were expressed as mean ± standard deviation, and the Duncan method was used for multiple comparisons among treatments.

[0027] Results and Analysis (1) Effect of GA on reproductive performance of gilts: The effect of GA on reproductive performance of gilts is shown in Table 2. As can be seen from Table 2, compared with the control group, the average daily weight gain of the GA group increased significantly, and the feed-to-meat ratio decreased, while the average daily weight gain of the ZEA group and the ZEA+GA group increased, and the feed-to-weight ratio was lower, but the difference was not significant compared with the control group. The average daily feed intake was not significantly different among the groups (P>0.05). Compared with the control group, the body weight on the 19th day of the second estrus was significantly reduced in the ZEA group (P<0.05), and extremely significantly reduced in the GA group and the ZEA+GA group (P<0.01). Compared with the control group, the body weight of gilts at the first estrus in the ZEA group, the GA group and the ZEA+GA group was extremely significantly reduced (P<0.01), the age of the first estrus in the ZEA group was significantly advanced (P<0.05), and the age of the first estrus in the GA group and the ZEA+GA group was extremely significantly advanced (P<0.01). The backfat thickness of gilts in the ZEA, GA and ZEA+GA groups at the first estrus was significantly lower than that in the control group (P<0.05), and there was no significant difference in backfat thickness among the ZEA, GA and ZEA+GA groups (P>0.05). The estrus cycle of the ZEA group was significantly higher than that of the CON, GA and ZEA+GA groups (P<0.05), and there was no significant difference in estrus cycle among the CON, GA and ZEA+GA groups (P>0.05). During the experiment, it was observed that some sows in the ZEA group ended estrus and returned to estrus, and the estrus cycle was disordered.

[0028] Table 2 Effects of GA on reproductive performance of gilts

[0029] The same data with different lowercase letters indicate significant differences (P<0.05), and different uppercase letters indicate extremely significant differences (P<0.01).

[0030] (2) Effects of GA on the development of uterine and ovarian follicles in gilts ① As shown in Table 3, compared with the CON group, the uterine weights of the ZEA, GA and ZEA+GA groups were significantly increased (P<0.01), while the uterine weights of the GA and ZEA+GA groups were significantly lower than those of the ZEA group (P<0.01). Figure 1 ;in, Figure 1 Middle A) The picture shows the uterus of a non-estrus gilt in the CON group; Figure 1 Middle B) The picture shows the uterus of a gilt in the CON group on the 19th day of the second estrus; Figure 1 Middle C)-D) pictures show the uterus of the ZEA group gilts on the 19th day of the second estrus; Figure 1 Middle E) The picture shows the uterus of a gilt in the GA group on the 19th day of the second estrus; Figure 1 Middle F) The picture shows the uterus of a gilt in the ZEA+GA group on the 19th day of the second estrus. Figure 1 It can be seen that compared with the CON group, the uterine horns of the gilts in the ZEA group were enlarged and shortened, the number of uterine loops decreased, and the cervix became thicker and cartilaginous; the uterine horns of the GA group became longer and the number of uterine loops increased; the uterine horns of the ZEA+GA group became longer and the number of uterine loops increased. The above results show that ZEA can cause abnormal development of the uterus of gilts, while GA can promote the development of the uterus of gilts and reduce the harm of ZEA on the development of the uterus of gilts.

[0031] ② As shown in Table 3, compared with the CON group, the ovarian weight of the ZEA group was significantly reduced (P<0.01), and the ovarian weight of the GA group was significantly increased (P<0.05). Compared with the CON group, the number of large follicles, medium follicles and healthy mature follicles in the ZEA group was significantly reduced (P<0.01), and there was no significant difference between the GA group, the ZEA+GA group and the control group (P>0.05). The effect of GA on the development of ovarian follicles in reserve gilts can be seen in Figure 2 ;in, Figure 2 Middle A) The picture shows the ovaries of gilts in the CON group without estrus; Figure 2 Middle B) The picture shows the ovary of a gilt in the CON group on the 19th day of the second estrus; Figure 2 Middle C)-D) pictures show the ovaries of gilts in the ZEA group on the 19th day of the second estrus; Figure 2 Middle E) is the ovary of the 19th day of the second estrus of the GA group; Figure 2 (F) is the ovary of a gilt in the second estrus of the ZEA+GA group on the 19th day. Figure 2 It can be seen that the ovaries and follicles of the reserve gilts in the CON group, GA group and ZEA+GA group developed normally. The ovaries in the ZEA group developed abnormally, with ovarian atrophy, blackening, whitening and yellowing of follicles, and unclear spaces between follicles. The weight of the ovaries was significantly reduced, and the number of large follicles, medium follicles and healthy mature follicles was also significantly reduced.

[0032] Table 3 Effects of GA on the development of uterine and ovarian follicles in gilts

[0033] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The use of glycyrrhetinic acid in reducing the reproductive toxicity of zearalenone to gilts, characterized in that: The reproductive toxicity refers to the fact that zearalenone can cause abnormal development of reproductive organs and estrus disorders in gilts.

2. The use according to claim 1, characterized in that: The abnormal development of the reproductive organs includes enlarged and shortened uterine horns, a reduced number of uterine loops, and a thickened and chondrogenic cervix in gilts.

3. The use according to claim 2, characterized in that: The abnormal development of the reproductive organs also includes atrophy of the ovaries of the gilts; reduced weight of the ovaries; and reduced numbers of large follicles, medium follicles, and healthy mature follicles in the ovaries.

4. The use according to claim 1, characterized in that: The estrus disorder includes early onset of estrus and prolonged estrus cycle in gilts.

5. The use according to claim 1, characterized in that: Adding glycyrrhizic acid to gilt feed can reduce the gilt's weight at first estrus, advance the initial age and increase the back fat thickness at first estrus, and can promote timely estrus in sows.

6. The use according to claim 1, characterized in that: Adding glycyrrhizic acid to the gilt diet can promote the development of the gilt's uterus, significantly increase the weight of the uterus, increase the number of uterine loops, and significantly grow the left and right uterine horns.

7. The use according to claim 1, characterized in that: Adding glycyrrhizic acid to the diet of gilts can significantly increase the ovarian weight and the number of follicles of gilts, and improve the quality of their ovaries and follicles.

8. A method for reducing the reproductive toxicity of zearalenone to gilts, characterized in that: Add 100-600 mg / kg glycyrrhizic acid to the gilt diet.

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