褐藻寡糖是一种功能性海洋寡糖，由褐藻胶经酶解得到，由β-1，4-甘露糖醛酸（M）和α-1，4-古洛糖醛酸（G）链接起来的不规则低分子聚合物。褐藻寡糖粘度较低、水溶性强；此外，它还具有抗氧化、免疫调节、抗细菌和炎症等多种生物学活性，在医学科学、功能食品、绿色农业等领域有着广泛的应用。虽然我们对褐藻寡糖的研究相对缺乏，但它作为一种新型生物饲料添加剂应用于畜牧业生产中，前景广阔。本文综述了褐藻胶的来源、褐藻寡糖的化学组成、制备方法与生物学活性，以及在畜禽上的应用，为后续褐藻寡糖的深入研究和未来在产业上的应用奠定基础。

   Farm animals are sources of meat, milk and eggs for the humans, and animal health ensures the quality and security of these agricultural and sideline products. The animal raising conditions in livestock stations and poultry houses play vital roles in both animal health and production. One of the major factors affecting raising conditions, relative humidity, has not received much attention even though it is important for animal husbandry. In this review, we summarize the impacts of relative humidity on animal health and welfare to draw attention for its importance in the improvement of animal raising conditions in the future.

    Here, we investigated the effect of dietary arginine (Arg) supplementation on innate immunity and the antioxidant ability of broiler chickens. The experiment was designed as a single-factorial arrangement (n=8 cages/treatment, six birds/cage), and we used four dietary Arg concentrations (10.0, 15.0, 20.0 or 25.0 g kg^–1). On day 21, the birds were killed to obtain spleen, cecal tonsil and liver samples to determine the gene expression and antioxidant characteristics. Increasing the Arg concentration linearly decreased (P<0.05) the mRNA expression of splenic interleukin-18 (IL-18) and tumor necrosis factor-α (TNF-α). Dietary Arg supplementation quadratically decreased (P<0.05) the expression of interleukin-1b (IL-1b) and interferon-γ (IFN-γ) mRNA in the spleen. Increasing Arg concentrations linearly and quadratically reduced the expression of IL-18 mRNA in the spleen. Meanwhile, increasing dietary Arg supplementation linearly and quadratically increased the lymphotactin mRNA (P<0.05) expression, and linearly increased the macrophage inflammatory protein-1β (MIP-1β) and toll-like receptor 15 (TLR15) mRNA expression in the cecal tonsils. Dietary Arg supplementation linearly (P<0.05) increased the glutathione peroxidase (GSH-Px), catalase (CAT), and lysozyme (LZM) activities in the liver. However, the malondialdehyde (MDA) activity in the liver was not influenced by the dietary Arg concentration (P>0.05). No significant (P>0.05) effect was found on the activity of superoxide dismutase (SOD) in the liver. Thus high levels of Arg supplementation (>20.0 g kg^–1) may potentially suppress the innate immunity of broiler chickens, and dietary Arg supplementation enhances the antioxidant activity in broiler chickens.

Two experiments were conducted to determine the effects of fiber level from alfalfa meal and sampling time on the apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of amino acids (AA) in growing pigs. A total of 24 ileal-cannulated pigs (Duroc×(Large White×Landrace) with body weight (21.4±1.5) kg) were randomly allotted to 4 treatments. The pigs were provided a corn-soybean meal diet or a diet containing 5, 10 or 20% of alfalfa meal during two 10-d experimental periods. The AID of AA was measured. Six ileal-cannulated pigs were fed a protein-free diet in order to estimate the endogenous protein losses and SID of AA. Ileal AA digestibility was not affected by inclusion of 5 or 10% alfalfa meal in the diet (P>0.05). The AID of His, Lys, Met, Phe, Thr, Val, Ala, Asp, Cys, Gly, Pro, Ser and Tyr reduced by 2.0–6.8% with the addition level of alfalfa meal (linear, P<0.05). The SID of His, Lys, Ser, Thr and Tyr decreased by 2.2–4.3% as the level of alfalfa meal in the diet increased (linear, P<0.05). The AID and SID of AA were not affected by the sampling time (P>0.05). A multiple linear regression analysis, taking into account both the soluble and insoluble fiber content in the diets, explained more than 36% of variation in SID of Ser and Thr (P<0.05). In conclusion, the corn-soybean meal diet containing 10% of alfalfa meal did not affect ileal AA digestion. The AID and SID of AA were similar between two sampling times. Increasing the concentration of total dietary fiber from 12.3 to 21.4% by adding graded levels of alfalfa meal (0–20%) to a corn-soybean meal control diet induced a linear reduction in AID and SID of most AA. Soluble and insoluble fibers from alfalfa meal have differential roles in the AA digestion, which may help explain the variation observed in the SID of partial AA. These findings would provide important information for dietary fiber level and composition related to AA digestion.

The fiber level and composition have an important effect on nutrient digestibility of swine diets. Little information is known about the effects of fiber level and composition from alfalfa meal on nutrient digestibility of fattening pigs fed a corn-soybean meal-based diet. The objective of this experiment was to determine the effects of alfalfa fiber on the growth performance, intestinal nutrient flow and apparent total tract digestibility (ATTD) of nutrients in fattening pigs. 24 barrows (Duroc×(Large White×Landrace), body weight=(60.6±0.7) kg) were randomly allotted to 4 treatments with 6 replicates of 1 pig per replicate. The pigs were provided a control diet or a diet containing 5, 10 or 20% of alfalfa meal during a 14-d experiment period. Average daily gain (ADG) and the ATTD of dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF) and gross energy (GE) reduced linearly as the level of alfalfa meal in the diet increased (P<0.01). The total tract flow of DM, OM, CP, NDF, ADF, and GE increased with the increase in dietary alfalfa (linear, P<0.05). Growth performance and nutrient digestion were not affected by inclusion of 5% alfalfa meal in the diet (P>0.05). A multiple linear regression analysis, taking into account both soluble and insoluble fiber intake, explained approximately 70% of the variation in the ATTD of DM, OM, NDF, and GE (P<0.01). In conclusion, alfalfa meal should be limited to less than 5% of the diet in fattening pigs to maximize growth performance and nutrient digestion. Soluble and insoluble fiber from alfalfa meal has the differential roles in nutrient digestion, which may help explain the main variation observed in nutrient digestibility. These findings suggest that knowledge of specific fiber components is necessary to accurately predict the effects of dietary fiber on nutrient digestibility.