Effects Of Dietary Supplementation Of Different Sources And Levels Of Iron On Semen Quality Of Boars

The semen quality of boar is an important factor affecting reproductive performance of mating sows.Ferrion(Fe),as the most abundant essential trace element in the body,is involved in regulating key biological pathways such as DNA synthesis and mitochondrial function during spermatogenesis and maturation,as well as affecting oxidative stress level and inflammation state in the body.Previous laboratory studies have found that the serum Fe content of boars with poor semen quality is significantly reduced.It is suggested that sufficient Fe content in the body is one of the important conditions to ensure the good quality of boar semen.NRC(2012)recommends a minimum Fe requirement of 80 mg/kg for boar diets.However,due to low absorption efficiency and low price of inorganic iron,iron supplementation in pig production is much higher than the minimum requirement.It is found that adding excessive inorganic iron not only does not meet the Fe requirement of the body,but also produces side effects such as the increase of free radicals.In piglets and sows,supplementation of amino acid chelated iron can better improve the anemia of piglets and iron nutrition status of sows,but there are few reports on the supplementation of iron source and iron level in boars.In addition,because young boars are not fully developed in sexual and physical maturity,their Fe nutritional requirements may be higher than those of adult boars,which may lead to differences in Fe requirements of boars at different physiological stages.Therefore,this experiments aims to investigate the effects of adding different sources and levels of iron to the diets of boars at different physiological stages on semen quality,in order to determine the appropriate iron sources and levels in the diets of boars.The main research contents and results are as follows:Experiment 1 Effects of different sources and levels of iron on semen quality of adult boarsFifty-six healthy adult boars aged 15 to 21 months were randomly divided into 5groups according to the principle of similar serum Fe content and conventional semen quality parameters.They respectively were control group supplemented with 96 mg/kg ferrous sulfate and 54 mg/kg glycine chelate iron(group 1),80 mg/kg glycine chelate group iron(group 2),115 mg/kg glycine chelate group iron(group 3),80 mg/kg hydroxyl methionine chelate iron group(group 4)and 115 mg/kg hydroxyl methionine chelate iron group(Group 5).There were 10 to 12 boars in each group with 1 replicate per boar.The experiment lasted for 16 weeks.Blood and semen samples were collected every 4 weeks during the trial to detect hemoglobin content,conventional semen quality parameters and sperm membrane integrity of male pigs at weeks 0,4,8,12 and 16.The parameters related to sperm motility and sperm morphology were systematically detected by a computer aided system at weeks 8,12 and 16.After the trial period,Fe content in serum,seminal plasma and spermatozoa and serum Fe metabolism indexes were detected at 16 weeks,and serum inflammatory factors and oxidative stress levels in serum,seminal plasma and sperm were analyzed.The main research results are as follows:1.Semen quality:(1)Conventional semen quality parameters: In conventional semen quality indexes,although different diets had no significant effects on semen volume,sperm concentration and sperm motility(P>0.05),but the sperm abnormal rate was significantly affected by the trial time and diet treatment,and there was a significant interaction between the two factors.Compared with 0 weeks and 4 weeks,the sperm abnormal rate of boars in group5 was significantly decreased at 12 and 16 weeks(P<0.05).On the effect of diet treatment,there were no significant changes in the sperm abnormal rate of boar in different diet groups at 0 weeks,4 weeks and 8 weeks(P>0.05),and the sperm abnormal rate in groups3,4 and 5 was significantly lower than that in group 1 at 12 and 16 weeks(P<0.01).In the interaction effect,compared with 0 weeks,the malformation rate of male sperm was significantly decreased at 12 weeks and 16 weeks in group 5 diet(P<0.01).In addition,statistical analysis of total sperm count and effective sperm count of boars showed that total sperm count was not affected by trial time and diet treatment,while effective sperm count was affected by trial time and diet treatment,but there was no interaction between the two factors.Compared with 0 weeks,the effective sperm count of boars in groups 2and 5 was significantly increased at 12 and 16 weeks(P<0.05).On the effect of diet treatment,the effective sperm count of boars in group 5 was significantly higher than that in other experimental groups at 16 weeks(P<0.05).(2)Sperm motility parameters: The ratio of progressive motile sperm was significantly affected by trial time and diet treatment,and there was an interaction between the two factors.In terms of trial time effect,the ratio of progressive motile sperm in boars in groups 3 and 5 increased significantly at 12 and 16 weeks compared with 8weeks(P<0.05).The proportion of progressive motile sperm in group 5 was significantly higher than that in group 1 at 12 and 16 weeks of diet treatment(P<0.05).In the interaction effect,the proportion of f of progressive motile sperm increased significantly at 12 and 16 weeks compared with 8 weeks in group 5 diet(P<0.01).In addition,the local oscillating sperm ratio of boars in group 5 was significantly lower than that in group 1 at12 and 16 weeks(P<0.05).Other markers such as fast motile sperm ratio,slow motile sperm ratio,and rotational motile sperm ratio were not affected by trial time and diet treatment(P>0.05).(3)Sperm morphological parameters: the ratio of proximal protoplasmic droplet and distal protoplasmic droplet were only significantly affected by diet treatment.Compared with group 1,the ratio of proximal protoplasmic drops of sperm in groups 4 and 5 was significantly decreased at 12 weeks of treatment(P<0.05);At 12 and 16 weeks,the ratio of distal protoplasmic drops of sperm in groups 3,4 and 5 was significantly decreased(P<0.05).In addition,the tail folding ratio of male sperm was not affected by trial time and diet treatment(P>0.05).(4)Sperm membrane integrity: The integrity of sperm membrane fluctuated with the test time(P<0.01),but there was no significant change among different treatment groups at each test time point(P>0.05).2.Hemoglobin content: The analysis of hemoglobin content of boars in different diet groups at each test time point showed that compared with group 1,the dietary Fe supplemental level of boars in groups 2,3,4 and 5 was lower than that in group 1,but the body hemoglobin content of boars in groups had no significant difference(P>0.05).3.Iron status of the body: Although serum iron hepcidin(P<0.01),transferrin saturation(P<0.01)and transferrin receptor content(P<0.05)were significantly lower than that in group 1,and serum ferritin content of boars in groups 2,3 and 4 was significantly lower than that in group 1(P<0.05),but there was no significant difference in serum Fe content among different diet groups,and Fe content in seminal plasma of boars in group 5 was significantly higher than that in group 1(P<0.05).4.Inflammatory state of the body: Serum levels of inflammatory cytokines interleukin-6 were found to be significantly lower in boars in groups 4 and 5 than in group 1(P<0.01),and serum interleukin-10 content of the anti-inflammatory cytokine was significantly increased in group 5(P<0.05).5.Antioxidant stress state of the body: Compared with group 1,serum superoxide dismutase content and total antioxidant enzyme content of serum and seminal plasma of boars in group 5 significantly increased(P<0.05),while total antioxidant enzyme content in serum and seminal plasma of boars in group 3 was significantly decreased(P<0.05).In addition,the contents of malondialdehyde in serum,seminal plasma and sperm of boars in group 5 were significantly lower than those in group 1.Experiment 2 Effects of different sources and levels of iron on semen quality of young boarsThirty-five healthy young boars aged 9-10 months were randomly divided into 5groups with 7 replicates per group and 1 replicate per pig according to the principle of similar hemoglobin content and conventional semen quality parameters.The experiment lasted for 16 weeks.Diet treatment,sample collection and index detection are the same as test 1.The main research results are as follows:1.Semen quality:(1)Conventional semen quality parameters: semen volume,sperm density and sperm motility were not significantly affected by diet treatment(P>0.05).The sperm abnormal rate was significantly affected by diet treatment and test time,but there was no interaction between the two factors.Compared with week 0,the sperm abnormal rate in group 5 was significantly decreased at week 12 and week 16(P<0.05).On the effect of diet treatment,the sperm abnormal rate of boars in groups 4 and 5 was significantly lower than that in group 1 at 16 weeks(P<0.05).In addition,the total sperm count and effective sperm count of boars were also respectively affected by trial time and diet treatment.Compared with 0 weeks,total sperm count and effective sperm count of boars in groups 2,4 and 5were significantly increased at 16 weeks(P<0.05).On the effect of diet treatment,the total sperm count of boars in group 5 at 16 weeks(P<0.01)and effective sperm count(P<0.05)were significantly higher than group 1.(2)Sperm motility parameters: Different trial time and diet treatments had no significant effects on the ratio of progressive motile sperm,fast motile sperm,slow motile sperm,rotational motile sperm and local oscillating sperm(P>0.05).(3)Sperm morphological parameters: The ratio of protoplasmic drops in the distal end of male sperm was significantly affected by diet treatment.At 16 weeks,compared with group 1,the ratio of distal protoplasmic drops of boars in groups 4 and 5 was significantly decreased(P<0.05).However,different trial time and diet treatment had no significant effects on sperm tail folding ratio and proximal protoplasmic drop ratio(P>0.05).(4)Sperm membrane integrity: The integrity of sperm membrane fluctuated with the test time,but there was no significant change between different diet groups at each test time point(P>0.05).2.Hemoglobin content: In terms of time effect,hemoglobin content in young boars in groups 4 and 5 was significantly increased at 12 and 16 weeks compared with 0 weeks(P<0.01).On the effect of diet treatment,the hemoglobin content of boars in group 5 was significantly higher than that in group 3 at 16 weeks(P<0.05),but there was no significant difference compared with other experimental groups(P>0.05).3.Body iron status of the body: Different diets had no significant effects on serum,seminal plasma and sperm Fe content and serum iron status indexes of boars(P>0.05).4.Inflammatory status of the body: Analysis of serum inflammatory cytokines in boars showed that serum pro-inflammatory cytokine interleukin-1β was significantly lower in groups 2 and 5 compared with group 1(P<0.05),and serum anti-inflammatory cytokine interleukin-10 content of boars in group 5 was significantly increased(P<0.05).5.Oxidative stress state of the body: Different diets had no significant effects on the contents of antioxidant enzymes superoxide dismutase,catalase and total antioxidant capacity in serum,seminal plasma and sperm,as well as the content of peroxide product malondialdehyde(P>0.05).In conclusion,dietary supplementation of methionine hydroxyl analogue chelate iron can better improve semen quality of adult and young boars,which may be related to improving Fe utilization,alleviating inflammation and reducing oxidative stress level.However,adding 115 mg/kg methionine hydroxyl analogue chelate iron to the diet of young boars can not effectively improve the body’s iron content and antioxidant capacity.Therefore,methionine hydroxyl analogue chelate iron is a more suitable iron source for boar,but the appropriate iron level for young boar needs to be further studied.