Leiber Florian, Nigg Daniel, Kunz Carmen, Scheeder Martin R L, Wettstein Hans-Rudolf, Kreuzer Michael
Institute of Animal Science, Animal Nutrition, Swiss Federal Institute of Technology (ETH), ETH Centre/LFW, CH-8092 Zurich, Switzerland.
J Dairy Res. 2005 Feb;72(1):65-74. doi: 10.1017/s0022029904000615.
The influence of high altitude, alpine origin of the forage and roughage-only diets on milk protein content and composition, plasmin activity and cheesemaking properties was investigated. There were four treatment groups, each consisting of six dairy cows in early to mid-lactation. Two groups were fed only with hay ad libitum either at 2000 m or at 400 m a.s.l. One group, kept in the lowlands, was pair-fed to the alpine-site group and another group received a mixed diet of silages, hay and concentrates. Two hay types, harvested either at the alpine site or in the lowlands, were offered to all cows fed with hay alone, following a change-over design in three periods each of 3 weeks. In the respective third week, milk was sampled at every milking. Hay of alpine origin significantly reduced milk protein, in particular whey proteins, which is why the casein number increased. kappa-Casein proportion in total casein was reduced and its glycosylation was increased by the alpine hay. The apparent plasminogen-derived activity was reduced when alpine hay was given, but apparent plasmin activity and rennet coagulation properties of the milk were not affected by hay type. Independent of hay type, the high altitude group showed a significantly reduced milk protein content, lower glycosylation of kappa-casein and impaired rennet coagulation properties. For several of the traits, the trend was the same in the pair-fed group. There was no effect of altitude on apparent plasmin activity. Hay-alone v. the mixed diet resulted initially in marked declines in milk protein content but did not impair cheesemaking properties. Thus the extensive diet without concentrates, typical of high-alpine conditions, contributed less to the overall effect of extensive alpine v. intensive lowland feeding systems than hay quality and altitude did. In conclusion, certain positive influences of the alpine sojourn of cows on cheese processing quality are overruled by the major adverse impact of lower milk protein content.
研究了高海拔、牧草的高山产地以及仅以粗饲料为食的日粮对牛奶蛋白质含量和组成、纤溶酶活性及奶酪制作特性的影响。共有四个处理组，每组由六头处于泌乳早期至中期的奶牛组成。两组奶牛分别在海拔2000米或海拔400米处自由采食干草。一组饲养在低地，与高山地区的组进行配对饲养，另一组则采食青贮饲料、干草和精饲料的混合日粮。向所有仅采食干草的奶牛提供两种干草，分别是在高山地区或低地收获的，采用三阶段转换设计，每个阶段为期3周。在各自的第三周，每次挤奶时采集牛奶样本。高山产地的干草显著降低了牛奶蛋白质含量，尤其是乳清蛋白，这就是酪蛋白系数增加的原因。高山干草使总酪蛋白中的κ-酪蛋白比例降低，其糖基化增加。饲喂高山干草时，纤溶酶原衍生的表观活性降低，但牛奶的表观纤溶酶活性和凝乳酶凝固特性不受干草类型的影响。与干草类型无关，高海拔组的牛奶蛋白质含量显著降低，κ-酪蛋白糖基化程度较低，凝乳酶凝固特性受损。对于几个性状，配对饲养组的趋势相同。海拔对表观纤溶酶活性没有影响。仅采食干草与采食混合日粮相比，最初会导致牛奶蛋白质含量显著下降，但不会损害奶酪制作特性。因此，高海拔条件下典型的不添加精饲料的粗放型日粮，与干草质量和海拔相比，对粗放型高山饲养系统与集约型低地饲养系统总体效果的贡献较小。总之，奶牛在高山停留对奶酪加工质量的某些积极影响被牛奶蛋白质含量降低的主要不利影响所抵消。
