| چکیده انگلیسی مقاله |
Extended Abstract
Introduction and Objectives: Cows after calving, due to the production of milk with high fat content, which increases the energy output from the body; on the other hand, due to the less dry matter intake than what meets animal requirements, which is mainly due to metabolic and hormonal responses, cannot provide that amount of output energy from their body. All of these factors may can cause the activation of lipolysis messages for energy supply and as a result can cause metabolic disorders in this period. One of the solutions to deal with these disorders is the use of nutritional supplements, which can help prevent the occurrence of disorders during this period by reducing lipolysis messages or reducing the energy output from the body. Therefore, this study aimed to evaluate the effect of sodium acetate supplement as a lipogenic source and conjugated linoleic acid supplement as a lipolytic source on the performance of lactating cows in early lactation. Purpose of using sodium acetate supplement as a lipogenic source was to increase the animal's energy access to supply energy for intestinal tissue cells, peripheral cells, and increase de novo milk fatty acids production, which reduces the secretion of energy request messages by these tissues. On the other hand, conjugated linoleic acid supplement has a negative effect on the function of enzymes that produce milk de novo fatty acids, it causes a reduction of milk fatty acids and prevents releasing of energy through milk, which can help reduce the negative energy balance during early lactation. This study allows a comparative analysis of two distinct energy adjustment systems, each employing different mechanisms to enhance the management of negative energy balance.
Materials and Methods: Twenty-four multiparous cows with an average live body weight of 618 kg and a body condition score (BCS) of 3.73, which were examined in terms of health and without any fever, retention of fetal membranes, metritis, and milk fever, five days after calving were grouped into three treatments with eight replications. The duration of the experiment was 21 days (from the 5th to the 25th day after calving). Treatments include: (1) control, (2) 100 grams per day of conjugated linoleic acid (BASF Co) supplement with 20 percent purity content of 50 percent cis-9 trans-11, 50 percent trans-10 cis-12, and (3) 300 grams per day sodium acetate supplement. Dry matter intake was measured every day before feed delivery in the morning meal. Milk production was recorded in each meal and milk compositions were measured on 5, 8, 11, 14, 17, 20, and 25 days after calving. Blood parameters including glucose, total protein, and blood urea nitrogen were evaluated on 5, 7, 14, 20, and 25 days after calving. Statistical analysis of the parameters that were measured several times during the experiment was performed using the mixed procedure, and for other parameters that were measured once during the experiment, the GLM procedure was performed using the SAS statistical software (version 9/4).
Results: Dry matter intake was not affected among treatments (P = 0.31). However, dry matter intake on day 25 compared to day 5 in the control, conjugated linoleic acid and sodium acetate treatments increased by 1.64, 2.16, and 2.76 kg, respectively. Feeding sodium acetate supplement increased 19 percent daily milk production and 17 percent daily milk fat production (fat corrected milk based on 4 percent fat) compared to the control treatment (P = 0.03). Fat corrected milk based on 4 percent fat was not significantly different between conjugated linoleic acid treatment compared to other treatments (control and sodium acetate treatments; P = 0.23). Conjugated linoleic acid supplement tended to decrease milk fat percentage compared to the other two treatments (P = 0.09). There was a tended to be significant difference in the percentage of milk fat in sodium acetate treatment than in the control treatment. No significant difference was observed in the percentage and amount of daily production of other milk compounds including lactose and protein between treatments (P ˃ 0.10). In the blood parameters, only glucose index in conjugated linoleic acid treatment and sodium acetate treatment was significantly higher (P = 0.01) than control treatment. However, there was no significant difference in other blood parameters including total protein and blood urea nitrogen either in the whole period or at any measurement time.
Conclusion: According to the results of this study, it seems that the conjugated linoleic acid supplement improved energy storage in the body and balanced blood glucose by reducing the energy output by reducing the percentage of milk fat. On the other hand, sodium acetate supplement by supplying energy to the tissues and its role as a precursor of milk fat, which causes a decrease in fatty acid extraction from blood by the mammary glands, and a decrease in lipolysis messages caused an increase in milk fat and an increase in blood glucose.
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