نوع مقاله : مقاله پژوهشی
نویسندگان
گروه علوم دامی، دانشکده کشاورزی، دانشگاه زنجان، زنجان، ایران
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
The objective of this study was to investigate the effect of vitamin A injection on reproductive performance in repeat breeder cows. One hundred and sixty-two multiparous Holstein cows with at least three consecutive unsuccessful inseminations were randomly assigned to experimental treatments. Treatments included (1) control: twice intramuscular injection 10 ml placebo30 days apart: 0.9% sodium chloride (n=87) and (2) vitamin A: twice intramuscular injection 10 ml retinol palmitate 30 days apart (n=75). Animals submitted to double-ovsynch protocol and received their experimental treatments on the tenth day of the protocol (the day of the second injection of GnRH). The injection of retinol palmitate significantly increased the number of ovarian follicles larger than 10 mm compared to the control (P <0.05). Plasma concentration of superoxide dismutase enzyme tended to increase (P = 0.09) and malondialdehyde concentration tended to decrease (P = 0.08) under the influence of vitamin A injection. The conception rate at first artificial insemination was 25.29% and 34.66% for control and vitamin A treatments respectively, this difference was not significant (P = 0.19). The odds ratio of conception in the first service for vitamin A treatment was 1.57 times higher than the control treatment but was not statistically significant (P = 0.19). In conclusion, vitamin A injection improved antioxidant function and ovarian function. The reproductive performance improved, although not statistically significant.
کلیدواژهها [English]
Extended Abstract
Introduction
Repeat breeder cows (RBCs) are infertile cows that fail to conceive after three or more consecutive estrous cycles of normal during (17-25 days), without anatomical abnormalities or infections. This syndrome causes economic losses in dairy farms by increasing open days, the number of services per conception, the calving interval, and the culling rate. Embryonic mortality due to luteal deficiency is a major cause of returning to estrus in dairy cows. Researchers have suggested that oxidative stress affects the luteal function by inhibiting the activity P450 SCC enzyme, which is involved in the intracellular translocation of cholesterol to mitochondria, and by impairing hormone (LH) receptors, causes a decrease in progesterone levels and pregnancy disruption in repeat breeder cows. Some studies have shown that vitamin A can support antioxidant defense systems against oxidative stress. The purpose of this study was to investigate the effect of intramuscular injection of vitamin A on the reproductive performance in repeat breeder cows.
Material and method
One hundred and sixty-two repeat breeder Holstein cows were used in a completely randomized design. Treatments included (1) control: twice intramuscular injection 10 ml placebo30 days apart: 0.9% sodium chloride (n=87) and (2) vitamin A: twice intramuscular injection 10 ml retinol palmitate (100000 IU/ml, Nasr Pharmaceutical Company, Iran) 30 days apart (n=75). The Synchronization protocol and experimental activities (the time of injection of experimental treatments, blood sampling and ultrasound of the ovarian) are shown in Figure 1. Pregnancy diagnosis was performed by ultrasound between 32 and 35 d post-AI. Data were analyzed using the mixed and GLIMMIX procedure of SAS (version 9.3). Means were separated by the Tukey- Kramer multiple range test.
Result
Plasma concentration of superoxide dismutase enzyme tended to increase (P = 0.09, 120.39 vs 127.00) and malondialdehyde concentration tended to decrease (P = 0.08, 1.60 vs 1.39) under the influence of vitamin A injection, indicating vitamin A maybe enhance antioxidant defense systems against oxidative stress. Plasma concentration of progesterone was similar between treatments (p>0.05). The number of ovarian follicles larger than 10 mm was affected by treatment injection and was greatest in cows treated with vitamin A injection compared to control (1.59 vs 2.02 respectively, p=0.02). The conception rate and odd ratio of conception were not affected by experimental treatments (p>0.05).
Conclusion
The results of this experiment indicated an improvement in antioxidant function and a higher number of large follicles affected by vitamin A injection, but reproductive performance was not affected by treatment. Additional research with a higher number of animals is needed to further determine the best number and dosage best time for vitamin A injection.
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