عنوان مقاله [English]
Introduction: The main challenge of breeding broiler chicken breeders is to increase the production of fertile eggs. About 70% of the decline in production during different stages of incubation is due to infertile eggs and fetal mortality. The fertility reduction in male broiler breeders after 50 weeks has been reported as the major reason for production loss. This reduction can be attributed to different factors, such as age, weight, and low semen quality. The composition of seminal long chain fatty acids (FA) is affected by the diet. Thus, a diet enriched with n-3 and n-6 FAs can alter the proportion of fatty acids in the sperm and semen plasma. The amount of n-6 FAs in the sperm membrane phospholipid increased as a result of the consumption of a commercial diet.
The phospholipid of the bird sperm is identified with a very high amount of C20-22n-6 (PUFA). The increased amount of n-3 FAs in poultry sperm has a positive effect on the quality of sperm and fertility, which leads to increased sperm motility in the oviduct and fertilization. Flaxseed is the richest dietary source of n-3 FAs, i.e. α-linolenic acid, and lignan. Flaxseed dietary increases the amount of n-3 FAs (PUFA) in the phospholipid membrane of the sperm body, while it decreases n-6 FAs in the membrane of the sperm head and the ratio of n-3:n-6. In addition, the sperm motility has a positive correlation with the amount of phospholipid and a negative correlation with the amount of free cholesterol. The ability to synthesize C20-22 polyunsaturated FAs is decreased in phospholipids with age. Thus, the inclusion of α-linolenic acid in the diet of male birds results in an accurate balance of n-6/n-3 and a rise in the ratio of phospholipid/cholesterol, which would lead to a potential dramatic change in the fertility. The present study was aimed to investigate the effects of dietary flaxseed on the sperm quality and fertility of broiler breeder roosters.
Material and methods: This research was conducted on the broiler chicken farm of Kimiaparvar Company. Three experimental diets were tested on 1920 Ross 308 roosters which were located in six halls. Therefore, there were two halls for each experimental diet. The first phase were performed on the 33-41 weeks old birds, after their peak of production and the second phase was continued from 53 until 61 weeks of age. The experimental diets were as follows: control diet, which was formulated based on corn-soybean oil (n-6 FAs-rich), a diet with 0.2% omega-3 (n-3 FAs-rich (Pepin)), and a diet that contained 2% whole grain flaxseed. Five birds from each hall (n=30 in total) were randomly labeled for weighing, blood and sperm sampling. The blood tests, such as glucose, cholesterol, triglyceride and urea were performed using the spectrophotometry technique. The evaluation of sperm parameters and the analysis of fatty acids were conducted by the CASA system and the chromatography method, respectively. The labelled birds were trained for semen collection over three weeks using the method of abdominal message. The semen was collected once a week from week 57 to week 61. The collected samples from 5 birds were pooled before the analysis. In week 61th, the testicles of the birds were weighed after slaughter. In addition, the percentage of fertile and infertile eggs was calculated during the period. The birds were weighed from 33-61 weeks. The evaluation of sperm characteristics included: straight-liner velocity (VSL, µm/s), curvilinear velocity (VCL, µm/s), VAP: average path velocity (VAP, µm/s), linearity (LIN, %), wobble (WOB, %), straightness (STR, %), beat cross frequency (BCF, HZ), lateral head displacement (ALH, micron), mean angle degree (MAD, deg), progressive motility (PM, %), none progressive motility (NPM, %), immotile (IM, %), and concentration (M/ml).
Result and discussion: The dietary treatments had no significant effect on the blood parameters and the weight of testicles. Similarly, in a study adding 3% of fish oil in the diet of broiler breeder roosters did not change the testicular weight. The overall effect of dietary treatments in CASA data and motility parameters was non-significant. This is consistent with the previous studies, which showed that diets with different sources of fats have no effect on the sperm motility parameters. It has been reported that the flaxseed oil had no effect on the volume and concentration of semen.
According to our analysis, the dietary treatments increased the number of fertile eggs. The percentage of fertile eggs in the flaxseed group was significantly higher than the pepin and the control groups. However, there was no significant difference in the number of fertile eggs between the pepin and the control treatments. The researches confirmed that reducing the ratio of n-6/n-3 in rooster sperm by adding α-linolenic acid sources leads to increased fertility. The treatment and age had significant impacts on the body weight of the birds, where the lowest body weight was from the group that received the flaxseed diet. This could be beneficial for the producers as weight gain leads to reduced fertility in broiler breeders.
The biological studies on the fertility of birds have shown that the lipid composition is the main determinant of the required flexibility of the membrane for the flagellar movement and the penetration ability of the sperm, which would facilitate the acrosome activity and the fertilization.
Conclusion: Manipulation of the phospholipid fatty acids of the sperm membrane with the enriched n-3 fatty acids diet improves the fertility in roosters. Our weekly results indicate a significant improvement in the motion parameters and the quantity of sperms over some weeks during the study. This effect coincides with a significant increase in the number of fertile eggs in the flaxseed group. The flaxseed as an easy available and cheap source of n-3 FAs and lignans has more significant effects on the fertility compared with the fish oil, which is more expensive. Therefore, the whole flaxseed is an ideal dietary supplement for the broiler breeder roosters, especially for the old flocks.