Nelson W F, Satter L D
US Dairy Forage Research Center USDA, Agricultural Research Service, Madison.
J Dairy Sci. 1992 Jun;75(6):1571-80. doi: 10.3168/jds.S0022-0302(92)77914-4.
Four multiparous Holstein cows in midlactation were fed 60:40 forage:grain (dry basis) diets containing first-cutting alfalfa harvested at the early bud or early flower stage of maturity. Each of the two maturities was preserved as silage and hay. A 4 x 4 Latin square design experiment (28-d periods) was conducted to measure the impact of alfalfa maturity and method of preservation on milk production and composition, intake, digestion, digesta passage, and particle size of digesta. Milk production and composition were not affected by treatment. Increases in fiber intake resulted from increased maturity and preservation as hay, but this did not appear to limit DMI or milk production. Both increased maturity and preservation as hay resulted in the following effects in cows: more time spent ruminating, greater total chewing time, greater wet and dry rumen fill, and a greater volume of rumen contents. Rumen retention time of La applied to forage was 6 h less, and 0-h disappearance of DM from dacron bags was greater for silage than hay. In situ DM disappearance rates averaged 15%/h for silage and 9.5%/h for hay. Lag time was related inversely to 0-h disappearance. Masticates and mixed rumen samples from cows fed hay showed a greater percentage of DM as particles greater than or equal to 9.5 mm in length. Gross feed efficiency was greater for cows fed alfalfa silage than for those fed alfalfa hay, probably because of more rapid digestion and passage. The potential for rumen fill to limit intake in high producing cows appears to be greater for alfalfa preserved as hay than that preserved as silage.
四头处于泌乳中期的经产荷斯坦奶牛被饲喂了由60%粗饲料和40%谷物（干物质基础）组成的日粮，粗饲料为在初花期或初蕾期收获的头茬苜蓿。两种成熟度的苜蓿分别被制成青贮和干草。进行了一项4×4拉丁方设计试验（为期28天的试验期），以测定苜蓿成熟度和保存方式对牛奶产量和成分、采食量、消化率、食糜通过速度以及食糜颗粒大小的影响。处理对牛奶产量和成分没有影响。随着苜蓿成熟度增加以及制成干草保存，纤维采食量增加，但这似乎并未限制干物质采食量或牛奶产量。苜蓿成熟度增加以及制成干草保存均使奶牛出现以下情况：反刍时间增加、总咀嚼时间增加、瘤胃湿重和干重增加以及瘤胃内容物体积增大。施用于粗饲料的苜蓿在瘤胃中的停留时间减少6小时，青贮苜蓿在聚酯纤维袋中干物质的0小时消失率高于干草。青贮苜蓿的干物质原位消失率平均为每小时15%，干草为每小时9.5%。延迟时间与0小时消失率呈负相关。采食干草的奶牛的咀嚼物和混合瘤胃样本中，长度大于或等于9.5毫米的颗粒状干物质所占百分比更高。饲喂苜蓿青贮的奶牛的总饲料效率高于饲喂苜蓿干草的奶牛，这可能是因为消化和通过速度更快。对于高产奶牛而言，制成干草保存的苜蓿比青贮苜蓿更有可能因瘤胃充满而限制采食量。
