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

Birth weight is the most important factor affecting lamb survival, but even when birth weight is appropriate, some lambs are lost to 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 improves the reproductive performance of the flock. The structure of the placenta in ruminant animals prevents the transfer of immunoglobulins from maternal circulation to the fetus. Therefore, newborn ruminants are completely dependent on the 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, and 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 the 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 parturition affect the quantity and quality of colostrum in ruminant animals. Nutrition status in late pregnancy is the most important factor affecting the quantity and quality of colostrum produced in these animals. Therefore, an insufficient supply of vitamins in pregnant ewes is one of the reasons for reducing the survival and mortality of newborn lambs. Much research has been conducted regarding the effect of dietary or injectable vitamin A, D3, and E supplements in late pregnancy on the maternal immune system and the survival of newborn ruminants, although, they have mainly focused on vitamin E and selenium supplements. To our knowledge, there is no information on how the timing of the use of these vitamins in late pregnancy affects the metabolic responses of ruminants. 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. Forty Afshari mature ewes with an average of 45 kg and 2-3 years of age were used. One month before the expected lambing, animals were divided into four 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 four weeks before the expected lambing, 3. Injection of 10 mL of vitamin AD3E two weeks before the expected lambing, and 4. Injection of five mL of vitamin AD3E four weeks and five mL two weeks before the expected lambing. Blood samples of ewes and lambs were collected four and one week before the expected lambing and three days after colostrum consumption, respectively. Plasma was 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 showed that the greatest plasma concentrations of glucose and malondialdehyde (MDA) on day 7 before lambing were observed in ewes of the C groups (P<0.05). Experimental treatments did not affect plasma total cholesterol (TCh), triglyceride (TG), and magnesium (Mg) concentrations of ewes on day 7 before lambing (P>0.05). Plasma concentration of total protein (TP), calcium (Ca), and BRIX index on day 7 before lambing were higher in ewes who received vitamin AD3E compared to the C group (P<0.05). Ewes received 10 mL of vitamin AD3E two weeks before the expected lambing had the highest plasma glutathione peroxidase (GPX), superoxide dismutase (SOD), and total antioxidant activities on day 7 before lambing (P<0.05). Colostrum fat and lactose percentage were not influenced 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 the 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 did not affect plasma TCh, TG, Ca, and Mg concentrations of lambs (P>0.05). Lambs born from ewes received 10 mL of vitamin AD3E two weeks before lambing had the highest plasma GPX, SOD, and total antioxidant activities compared to other groups (P<0.05). Vitamin AD3E injection increased the plasma BRIX index of lambs compared to the group without injection (P<0.05). The results showed that injection of vitamin AD3E two weeks before lambing increased plasma TP concentration and antioxidant activity of ewes, as well as colostrum TP content, and consequently increased plasma TP concentration and antioxidant activity of lambs. Therefore, this can be an effective strategy to improve lamb survival and performance.