Effect of intramuscular injection of vitamin B12 on lactation performance of Lori-Bakhtiari ewes and some blood parameters of their lambs

Introduction: In ruminants, vitamin B12 is a cofactor for two enzyme systems that are involved in many metabolic processes, such as the metabolism of carbohydrates, lipids, some amino acids, and DNA. Vitamin B12 in ruminants is synthesized by rumen bacteria or provided by dietary sources. Vitamin B12 deficiency may result in poor growth, anemia, and reduced milk production in lactating animals. In young ruminants such as newborn lambs and calves, the rumen is not fully developed for vitamin B12 synthesis until six to eight weeks of age. This means that during this period, a dietary source of vitamin B12 is necessary. Colostrum, milk, or milk replacers may be used as a source of vitamin B12 in these young ruminants. However, different factors, including nutritional deficiencies, may affect the vitamin B12 content in milk. This study aimed to investigate the effects of vitamin B12 intramuscular injection on the lactation performance of ewes and on certain blood parameters in their lambs. Materials and methods: The current research was conducted at the animal husbandry station of Lorestan University.  Twenty early lactating ewes (60±0.50 kg) were selected and allocated to one of the two groups (10 ewes per group). Treatments included 1. Ewes without vitamin B12 injection (control group) and 2. Ewes with a weekly injection of vitamin B12. The first injection of vitamin B12 was given immediately after the ewes were lambed and three further injections were given per week (four injections in total). The amount of vitamin B12 injection was 1 mg intramuscularly in each injection. Milk production was recorded during the 10th, 20th, and 30th days of lactation, and the lambs were separated from their mothers for 12 hours, at which time they were weighed using a digital scale for 10 minutes. The lambs were allowed to use their mother's milk. Immediately after separation from their mother, lambs were weighed again and the difference in weight before and after milk consumption was recorded. The milk composition (including milk protein, milk fat, fat-free solids, palmitic acid, stearic acid, oleic acid, polyunsaturated fatty acids, monounsaturated fatty acids, and total unsaturated and unsaturated fatty acids) was measured with DA 7250 NIR Auto-analysis. To check the blood parameters of lambs, blood samples were taken from the jugular vein of newborn lambs at 10, 20 and 30 days of age, and from two separate tubes, one for the count of cells and one for the measurement of serum concentrations of vitamin B12 and other metabolites in the blood. Vitamin B12 concentrations were measured using the Pars Azmoun kit and the ELISA device. The data analysis was carried out with SAS statistical software (version 9.4). The comparison of the means was done using a t-test with a significance level of 0.05. Results and discussion: Results showed that milk yield in the vitamin B12 group were significantly higher than that in the control group during the four weeks of the experimental period (P<0.05). This increase in milk production can be considered a response to the increased availability of plasma glucose for milk lactose production by increasing plasma vitamin B12 concentration and its vital role, such as participating in many metabolic pathways in the body and acting as an intermediary in the catabolism of some amino acids. However, the percentage of milk compounds, including milk fat, protein, solids not fat, palmitic acid, stearic acid, oleic acid, mono- and polyunsaturated fats, and saturated fats, was unaffected by the administration of vitamin B12 (P˃0.05). Blood vitamin B12 concentration was significantly higher in vitamin B12 injected ewes compared with the control group (P<0.05). There was no significant difference in growth performance, average wean weight, average birth weight, or daily weight gain of lambs born to vitamin B12-treated ewes compared to control lambs (P>0.05). Injection of vitamin B12 into pregnant ewes had no significant effect on the blood glucose, white blood cells, hemoglobin concentration, red blood cells, or hematocrit percentage of the newborn lambs (P>0.05). Vitamin B12 status in suckling lambs can be related to the rate of transfer of this vitamin through milk during lactation and through the placenta during pregnancy. Conclusions: Consequent intramuscular administration of vitamin B12 to ewes at the beginning of lactation may increase milk production and thereby increase the lambs' performance and vitamin B12 concentration in the blood.