Effect of time and amount of vitamin AD3E injection in late pregnancy on colostrum quality and plasma parameters concentration and antioxidant status of Afshari ewes and their lambs

Introduction: Birth body weight is the most important factor influencing the survival of lambs but even if the birth weight is suitable, some of them will be lost until weaning. Infectious diseases are the most important factors affecting the mortality of lambs before weaning. Therefore, any factor that reduces the prevalence of these infections has a positive effect on the survival of lambs and improving the reproductive performance of the sheep flock. The structure of placenta in ruminant animals prevents the transfer of immunoglobulins from maternal circulation to the fetus. Therefore, newborn ruminants are completely dependent on absorption of immunoglobulins from the mother's colostrum after birth. Consuming a sufficient amount of high quality colostrum at the right time is the most important management factor affecting the survival and health of newborn ruminants. Colostrum also affects the survival of lambs by providing nutrients necessary for metabolism and heat production. Fat-soluble vitamins (A, D3, E) are among the important components of colostrum and their concentrations are higher in colostrum compared to milk. These vitamins play an important role in improving immune system of ruminant animals. Many genetic and non-genetic factors such as animal breed, mother's age, nutrition of dam in late pregnancy, herd vaccination program, colostrum volume and colostrum collection time after calving affect the quantity and quality of colostrum in ruminant animals. Nutrition status in late pregnancy is the most important factors affecting the quantity and quality of colostrum produced in these animals. Therefore, insufficient supply of vitamins in pregnant ewes is one of the reasons for reducing the survival and mortality of newborn lambs. Many researches have been conducted regarding the effect of dietary or injectable vitamin A, D3 and E supplement in late pregnancy on maternal immune system and the survival of newborn ruminant, although, they have mainly focused on vitamin E and selenium supplement. To our knowledge, there is no any information about the time of using these vitamins in late pregnancy on metabolic responses of ruminant animals. Therefore, this experiment aimed to investigate the effect of time and amount of vitamin AD3E injection in late pregnancy on colostrum quality and plasma metabolites of Afshari ewes and their lambs.
Materials and methods: Forty Afshari mature ewes with average 45 kg of BW and 2-3 years were used. One month before expected lambing, animals were divided into 4 groups and randomly assigned to experimental treatments. Experimental treatments were: 1- no injection of vitamin AD3E (Control; C), 2- injection of 10 mL of vitamin AD3E at 4 weeks before expected lambing, 3- injection of 10 mL of vitamin AD3E at 2 weeks before expected lambing and 4- injection of 5 mL of vitamin AD3E at 4 weeks and 5 mL at 2 weeks before expected lambing. Blood samples of ewes and lambs were collected at 4 and 1 week before expected lambing and 3 days after colostrum consumption, respectively. Plasma were separated and stored at -20◦C for metabolites measurement. Samples of colostrum from all animals were collected and stored at 3-5◦C for determining chemical composition and BRIX index.
Results and discussion: Results showed that the greatest plasma concentrations of glucose and malondialdehyde (MDA) at the day 7 before lambing were observed in ewes of the C groups (P<0.05). Experimental treatments had no effect on plasma total cholesterol (TCh), triglyceride (TG) and magnesium (Mg) concentrations of ewes at the day of 7 before lambing (P>0.05). Plasma concentration of total protein (TP), calcium (Ca), and BRIX index at the day of 7 before lambing were higher in ewes received vitamin AD3E compared to the C group (P<0.05). Ewes received 10 mL of vitamin AD3E at 2 weeks before expected lambing had the highest plasma glutathione peroxidase (GPX), superoxide dismutase (SOD) and total antioxidant activities at the day of 7 before lambing (P<0.05). Colostrum fat and lactose percentage did not influence by experimental treatments (P>0.05). Whereas, colostrum protein percentage tended to be lower for ewes in the C group (P=0.08). The lowest colostrum BRIX index was observed in ewes of the C group (P<0.05). The lowest plasma glucose concentration was observed in lambs born from ewes of the C group (P<0.05). Experimental treatments had no effect on plasma TCh, TG, Ca and Mg concentrations of lambs (P>0.05). Lambs born from ewes received 10 mL of vitamin AD3E at 2 weeks before lambing had the highest plasma GPX, SOD and total antioxidant activities compare to other groups (P<0.05). Vitamin AD3E injection increased plasma BRIX index of lambs compared to no injection (P<0.05).
Conclusions: These results showed that vitamin AD3E injection at 2 weeks before lambing increased plasma TP concentration and antioxidant activity of ewes, colostrum TP content and consequently plasma TP concentration and antioxidant activity of lams. Therefore, this may be an effective strategy to improve lamb survival and performance.