1. The effect of rosemary extract added to the diet on the performance of dairy goats

Rosemary extract, as a natural feed additive, can be added to livestock and poultry diets to improve animal performance and enhance the quality of animal products. Researchers added rosemary distillate to lamb diets and increased the average daily weight gain and weight of functional organs (skin, liver, kidneys and testes) of lambs. The addition of rosemary extract to ewe rations increased milk production and improved goat milk quality. Addition of distilled rosemary leaves to goat gestation and lactation rations did not affect milk yield and milk composition of ewes, increased the content of polyphenols in milk, and had a positive effect on lamb growth. In this experiment, the addition of rosemary extract to the ration had no significant effect on milk production and dry matter intake of dairy goats. The results of this experiment differed from those of previous studies, probably because the structure of the polyphenolic compounds contained in rosemary extracts contains phenolic hydroxyl groups, which are unstable in the rumen environment and are prone to degradation and generation of other substances, leading to a decrease in the content of active ingredients, and probably because the extraction process of rosemary extracts is not mature enough, and the components and their contents vary greatly between different ways of extraction [9], the The specific reasons for this need to be further investigated.

2. Effect of rosemary extracts on the apparent digestibility of nutrients in dairy goats

The change of apparent digestibility of nutrients can reflect the digestion and utilization of nutrients in the ration by the animal body, and the increase of apparent digestibility can, to a certain extent, reduce the amount of nutrients excreted in the body and improve the utilization of the ration by the animal. At present, the results of studies on the apparent digestibility of nutrients by rosemary extract are mixed. The addition of rosemary essential oil to sheep rations had no significant effect on the apparent digestibility of dry matter, organic matter, crude protein and neutral detergent fiber in sheep. The addition of rosemary essential oil to beef cattle rations had no significant effect on dry matter intake and apparent digestibility of crude protein, and reduced the apparent digestibility of dry matter and neutral detergent fiber. The addition of rosemary leaves to lamb rations had no significant effect on the apparent digestibility of dry matter, crude protein, neutral detergent fiber and organic matter, and reduced the apparent digestibility of acid detergent fiber. The results of this experiment showed that the addition of rosemary extract to the ration had no significant effect on the apparent digestibility of dry matter, crude protein, crude fat, neutral detergent fiber and acid detergent fiber in dairy goats, probably because the rosemary extract was degraded in the rumen resulting in a decrease in the content of active ingredients, and probably because the effect of rosemary extract on the digestibility of nutrients in different physiological stages and different breeds of animals The specific reasons for this are to be further investigated.

3. Effect of rosemary extract in the diet on serum antioxidant index of dairy goats

GSH-Px and SOD are the main antioxidants in dairy goats, and MDA is the main product of lipid peroxidation by oxygen radicals combined with polyunsaturated fatty acids in biofilms. T-AOC is a comprehensive indicator of the antioxidant capacity of the organism. Studies have shown that the administration of rosemary extract to a mouse model of asthma inhibited the production of reactive oxygen species (ROS) in lung tissue and alveolar lavage fluid, significantly increased serum SOD and GSH-Px activities, and improved the pathological changes of lung tissue in oxidative lung injury in mice. It was found that the addition of rosemary extract to the ration increased serum SOD activity and T-AOC and decreased serum MDA levels in laying hens, thus improving their antioxidant capacity. In this experiment, the addition of rosemary extract to the diet significantly increased the serum GSH-Px activity and had a tendency to increase the serum T-AOC in dairy goats, which is basically consistent with the results of previous studies, indicating that the addition of rosemary extract to the diet under the present experimental conditions could improve the antioxidant capacity of dairy goats. The reason: on the one hand, it may be that rosemary extract can promote the expression of oxidation reducers and their proteins in the animal organism, thus increasing the activity of antioxidant enzymes in the animal body; on the other hand, it may be that the structure of phenolic acids in rosemary extract contains hydroxyl groups and the branched chains contain carbon-carbon double chains, which have obvious reducing properties and can effectively decompose the oxidation products produced by the animal organism due to oxidative stress and increase the antioxidant enzyme 4.

4. Effect of rosemary extract in the diet on serum immune indexes and blood cell counts in dairy goats

TNF-α acts on the central nervous system and promotes the activation of the hypothalamic-pituitary-adrenal (HPA) axis, which helps to maintain the stability of the internal environment of the organism. It has also been shown that TNF-α is an important inflammation-associated cytokine that leads to increased inflammation when expressed at high levels. Interleukins (ILs) are a class of cytokines produced by and acting on a variety of cells and play an important role in the inflammatory response of the body. Common pro-inflammatory interleukins include IL-2, IL-6, IL-8, etc. Common anti-inflammatory interleukins include IL-4 and interleukin-10 (IL-10), etc. In this experiment, the addition of rosemary extract to the ration had no significant effect on serum IL-2, IL-4, IL-6, IL-8, and TNF-α levels in dairy goats, indicating that rosemary extract does not modulate the body's immune system by affecting cytokines in dairy goats.

Immunoglobulins are produced by the body after stimulation by antigens and are mainly composed of IgG, IgA and IgM. An increase in the level of immunoglobulins in the body indicates an increase in the body's immunity, while a decrease in the level of immunoglobulins in the body indicates a suppression of its immune function. IgM plays a very important role in the early stage of infection in the animal organism and is the first line of defense to prevent pathogens from invading the animal organism, as it is an immunoglobulin produced at the early stage of infection, with relatively high antibody efficacy and lysis and elimination of pathogens; IgA has the role of preventing microorganisms from attaching to the respiratory epithelium and inhibiting virus proliferation. In this experiment, the serum IgA and IgM levels of dairy goats in the rosemary extract group on day 21 were significantly higher than those of the control group, indicating that the addition of rosemary extract to the dairy goat diet up to day 21 improved the immune function of the dairy goat organism. This may be due to the fact that rosemary extract can inhibit the expression of inflammatory pathways and related inflammatory factors to activate the body's immune system, and may also be related to its ability to effectively scavenge or reduce the levels of superoxide and oxidized nitrite in the body. The serum IgA and IgM levels of dairy goats in the rosemary extract group on day 42 were significantly lower than those of the control group, indicating that there was a suppressive effect on the immune function of dairy goats as the feeding time of rosemary extract increased, which may be due to the fact that rosemary extract was metabolized by intestinal microorganisms to caffeic acid and its derivatives before absorption, and caffeic acid can inhibit the expression of transducin and transcriptional activator 3 in T cells ( STAT3) expression and inhibits the proliferation of lymphocytes and CD4+ T cells achieving induction of apoptosis, thus causing immunosuppression in the organism.

Blood plays an important role in the metabolism, internal and external environmental balance and physiological functions of the body, and blood cell counts reflect changes in the cells of the blood and are used to assess the level of health of the body and for disease surveillance. Leukocytes, lymphocytes, monocytes and neutrophils are important blood components involved in the body's inflammatory response and immune defense mechanisms, and have roles in phagocytosis of foreign substances and production of antibodies, repair of damage, and defense against pathogenic invasion. In this test, the blood cell counts of both control and rosemary extract groups were within the normal range, and the blood neutrophil count of dairy goats in the rosemary extract group on day 42 was significantly higher than that of the control group, while the blood lymphocyte count tended to be lower than that of the control group. Combined with the serum immune indexes of this test, it was found that with the prolongation of rosemary extract feeding time, the dairy goat organism would produce a certain immunosuppressive effect, which led to an increase in the number of blood neutrophils and a decrease in the number of lymphocytes in dairy goats.

Conclusion

In this experiment, the addition of rosemary extract to the diet improved the antioxidant capacity of dairy goats, and the short term (21 d) feeding improved their immune function, but the prolonged (42 d) feeding had a certain suppressive effect on their immune function.

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