نوع مقاله : مقاله پژوهشی
نویسندگان
گروه علوم دامی، دانشکده کشاورزی، دانشگاه زنجان، زنجان، ایران
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
The aim of this experiment was to evaluate the effect of dietary Mg on reproduction performance and expression of MMP-2, MMP-9 and TIMP-2 genes in the placenta. 50 cows in each treatments, from 3 weeks to calving were randomly assigned to four experimental treatments. Treatments included control treatment (magnesium at the level of NRC recommendations), magnesium sulfate, magnesium carbonate and magnesium oxide treatments (magnesium 0.6% of DM). Placenta samples were taken after calving and mRNA expression were investigated. Blood samples were collected pre and postpartum and plasma metabolites were measured. Relative mRNA expression of MMP-9 in magnesium oxide and magnesium sulfate treatments was higher and the percent of retained placenta in this treatments was lower than control group. Experimental treatments had no significant effect on the expression of MMP-2 and TIMP-2. Experimental diets had no effect on uterine involution score, first estrus and AI/conception. Treatments improved plasma Mg and insulin concentrations and reduced NEFA significantly. Magnesium oxide treatment improved pregnancy at first AI and pregnancy by 210 days postpartum. Cows in the experimental diets had fewer open days than the control group. The results showed that increasing dietary Mg compared to NRC (2001) recommendations could reduce retained placenta and improve fertility.
کلیدواژهها [English]
Extended Abstract
Introduction
Maintaining health and production during transition period is an important challenge in dairy herds. Reproduction and performance of dairy cows are influenced by several factors. Metabolic diseases such as ketosis and retained placenta can have a negative effect on reproduction and cause economic losses in dairy farms. Magnesium is an important mineral in the diet. Lack of magnesium in the diet can have negative consequences on animal reproduction and health. Several studies have shown that increasing plasma magnesium reduces retained placenta and reduces first ovulation time. Higher plasma magnesium can improved conception rate. The purpose of this study was to investigate the effect of dietary magnesium and plasma magnesium level on reproductive performance and the expression of genes related to retained placenta.
Materials and Methods
200 multiparous Holstein cows with body weight 726± 31.2, body condition score 3.35± 0.32 were enrolled in a completely randomized design at 21 d before expected calving. Dietary treatments were control diet (CO; Mg at the level of conventional diets), magnesium sulfate diet (MgS; Mg= 0.6% of DM), magnesium carbonate diet (MgC; Mg= 0.6% of DM), and magnesium oxide diet (MgO; Mg= 0.6% of DM). All cows received the same postpartum diet. Blood samples were collected 4 h after morning feeding from the on −21, −14, −7, −3, 1, 3, 7, 14 and 21 d relative to expected calving date. After calving, blood samples were taken weekly. Magnesium, insulin and NEFA of plasma were analyzed pre and postpartum. After calving, placenta samples were taken from cows and placed in liquid nitrogen to investigate MMP-2, MMP-9 and TIMP-2 genes expression. Uterine involution score, number of services per conception (AI/conception), first estrus time and days open were recorded for all of 200 cows.
Results and discussion
The results showed that pre and postpartum plasma magnesium and insulin were increased with supplementation of magnesium treatments. Magnesium oxide decreased plasma NEFA (P ≤ 0.05). Magnesium oxide decreased the percentage of retained placenta and increased the percentage of pregnancy at first AI and pregnancy up to 210 days after calving (P ≤ 0.05). Uterine involution score was not different between treatments. Experimental treatments had no significant effect on relative expression of genes MMP-2 and TIMP-2. Relative expression of MMP-9 was significantly higher in the magnesium oxide and sulfate diets than in the control group (P ≤ 0.05).
Conclusion
The results of this study showed that higher magnesium in diet and plasma increases magnesium and insulin of plasma and reduces blood NEFA. Also, magnesium treatments, especially magnesium oxide, reduce retained placenta and improve reproduction performance.
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