Girard M, Dohme-Meier F, Wechsler D, Goy D, Kreuzer M, Bee G
Institute for Livestock Sciences ILS, Agroscope, Tioleyre 4, 1725 Posieux, Switzerland; Institute of Agricultural Science, ETH Zurich, Universitaetstrasse 2, 8092 Zurich, Switzerland.
Institute for Livestock Sciences ILS, Agroscope, Tioleyre 4, 1725 Posieux, Switzerland.
J Dairy Sci. 2016 Jan;99(1):205-20. doi: 10.3168/jds.2015-9952. Epub 2015 Nov 18.
Condensed tannins (CT) may affect ruminal biohydrogenation of dietary polyunsaturated fatty acids. A feeding experiment was conducted with 24 Holstein cows to evaluate whether diets containing CT from different forage legumes can increase polyunsaturated fatty acids, especially n-3 fatty acid content in milk and cheese, without affecting negatively their physicochemical and sensorial properties. Cows were assigned to 4 treatment groups (n=6) for 52 d, divided into 2 periods: a control period (CoP) and an experimental period (ExP). During the CoP, cows received a basal diet composed of hay, corn silage, ExtruLin (Trinova Handel & Marketing AG, Wangen, Switzerland), concentrate, and alfalfa (AF) in a ratio of 45:25:5:7:18. In the ExP, in 3 of the 4 groups AF was replaced by either sainfoin (SF; 19% CT in dry matter) or 1 of 2 cultivars of birdsfoot trefoil [Polom (BP), 3% CT; Bull (BB), 5% CT]. At the end of each period, milk was collected on 3 consecutive days and analyzed for milk gross composition and fatty acid profile and was processed to Gruyère-type cheese. A trained panel assessed the sensory quality of raw milk and cheese using discriminative and descriptive tests. This experimental design consisting of AF in both the CoP and ExP allowed us to quantify effects due to lactation stage and experimental diets. In both the CoP and ExP, dry matter intake and milk yield did not differ among treatment groups. From the CoP to the ExP, milk urea content was reduced by 23% with SF, remained unchanged with BP, and tended to increase with AF and BB. The odor of the raw BB milk was judged to be different from AF milk. With SF, switching from the CoP to the ExP resulted in a 17% increase of the 18:3n-3 proportion in milk and cheese lipids. In BP cheese, the increase was 3%, whereas it tended to decrease in BB cheese. Additionally, the 20:5n-3 and 22:5n-3 proportions tended to increase in SF cheese from the CoP to the ExP. Compared with the AF cheeses, cheeses from cows fed CT-containing legumes were judged harder and tended to be less adhesive to the palate. In addition, SF and BP cheeses had less rind. In conclusion, feeding SF compared with BB and BP increased the content of 18:3n-3 in the milk and the cheese without a negative effect on flavor of the cheese. Despite a similar CT content, the 2 birdsfoot trefoil cultivars had opposite effects on milk urea and 18:3n-3 deposition, suggesting that, besides the content, the chemical structure may have had an important effect on the CT efficacy.
缩合单宁（CT）可能会影响日粮中多不饱和脂肪酸的瘤胃生物氢化作用。用24头荷斯坦奶牛进行了一项饲养试验，以评估含有来自不同豆科牧草的CT的日粮是否能增加多不饱和脂肪酸，尤其是牛奶和奶酪中n-3脂肪酸的含量，同时又不会对其理化性质和感官特性产生负面影响。将奶牛分为4个处理组（每组n = 6），试验期为52天，分为两个阶段：对照期（CoP）和试验期（ExP）。在CoP期间，奶牛采食由干草、玉米青贮、ExtruLin（Trinova Handel & Marketing AG，瑞士旺根）、精料和苜蓿（AF）按45:25:5:7:18比例组成的基础日粮。在ExP期间，4个组中的3个组用红豆草（SF；干物质中CT含量为19%）或两种三叶草品种之一[Polom（BP），CT含量为3%；Bull（BB），CT含量为5%]替代AF。在每个阶段结束时，连续3天采集牛奶，分析牛奶的总成分和脂肪酸谱，并加工成格律耶尔型奶酪。一个经过培训的小组使用鉴别性和描述性测试评估生牛奶和奶酪的感官质量。这种在CoP和ExP中都包含AF的实验设计使我们能够量化泌乳阶段和试验日粮的影响。在CoP和ExP期间，各处理组之间的干物质摄入量和产奶量没有差异。从CoP到ExP，SF组的牛奶尿素含量降低了23%，BP组保持不变，AF组和BB组有升高的趋势。BB组生牛奶的气味被判定与AF组牛奶不同。对于SF组，从CoP转换到ExP导致牛奶和奶酪脂质中18:3n-3比例增加了17%。BP组奶酪中增加了3%，而BB组奶酪中有下降的趋势。此外，从CoP到ExP，SF组奶酪中二十碳五烯酸（20:5n-3）和二十二碳五烯酸（22:5n-3）的比例有增加趋势。与AF组奶酪相比，采食含CT豆科牧草的奶牛所产奶酪被判定更硬，并且对 palate 的粘附性往往更小。此外，SF组和BP组奶酪的外皮更少。总之，与BB组和BP组相比，饲喂SF组增加了牛奶和奶酪中18:3n-3的含量，且对奶酪风味没有负面影响。尽管CT含量相似，但两种三叶草品种对牛奶尿素和18:3n-3沉积有相反的影响，这表明除了含量外，化学结构可能对CT的功效有重要影响。
