Campo Experimental N°2, Facultad de Veterinaria, Universidad de la República, Ruta 1 km 42, CP 80100 San José, Uruguay.
Departamento de Nutrición Animal, Instituto de Producción Animal, Facultad de Veterinaria, Universidad de la República, Ruta 1 km 42, CP 80100 San José, Uruguay.
J Dairy Sci. 2019 May;102(5):4118-4130. doi: 10.3168/jds.2018-15389. Epub 2019 Mar 1.
The purpose of this experiment was to determine the effects of feeding increasing levels of fresh forage (FF) as a proportion of total dry matter intake (DMI) on nutrient intake, rumen digestion, nutrient utilization, and productive performance of total mixed ration (TMR)-fed cows. Twelve dairy cows (90 ± 22 d in milk, 523 ± 88 kg of body weight, 7,908 ± 719 kg of milk production in the previous lactation) were housed in individual tiestalls and assigned to treatments according to a 3 × 3 Latin square design replicated 4 times. Treatments were 100% TMR (T100), 75% TMR plus 25% FF (T75), and 50% TMR plus 50% FF (T50). The experiment lasted 60 d, divided into 3 periods of 20 d each; the first 12 d of each period were used for diet adaptation and the last 8 d for data collection. The TMR (18.1% crude protein, 24.6% acid detergent fiber) and FF (Lolium multiflorum; 15.1% crude protein, 24.1% acid detergent fiber) were prepared and cut daily and offered to each cow individually. The highest DMI was reached in T100 and T75, which was reflected in greater intake of the different nutrients than T50. No differences were detected in the apparent total digestibility of the nutrients, mean ruminal pH, and total volatile fatty acid concentrations among treatments. Cows in T50 resulted in the lowest ruminal N-NH concentration and the lowest microbial N flow to the duodenum. Milk yield was 8.5% higher from cows in T100 and T75 compared with T50, but we observed no differences for milk fat or milk protein yield among treatments. Milk fat of cows fed T50 had 8% more unsaturated fatty acids (FA) than that of cows fed T100, mostly because of a higher content of monounsaturated FA. Additionally, cows in T50 had a higher concentration of linoleic acid, vaccenic acid, and rumenic acid than T100. Meanwhile, the concentration of linoleic acid and vaccenic acid in cows fed T75 was higher than T100. The milk fat of the cows fed T50 and T75 had a lower n-6:n-3 ratio than T100. We concluded that including up to 29% of FF in the total DMI in combination with a TMR did not affect the intake or digestion of nutrients or the productive response in dairy cows and resulted in a higher concentration of desirable FA from a consumer's perspective.
本实验旨在确定以不同比例的新鲜饲草（FF）作为总干物质采食量（DMI）的一部分来喂养奶牛对养分摄入、瘤胃消化、养分利用和全混合日粮（TMR）喂养奶牛生产性能的影响。12 头奶牛（泌乳 90±22 天，体重 523±88 千克，上一个泌乳期产奶 7908±719 千克）被安置在单独的牛栏中，并根据 3×3 拉丁方设计进行处理分配，重复 4 次。处理组为 100%TMR（T100）、75%TMR+25%FF（T75）和 50%TMR+50%FF（T50）。实验持续 60 天，分为 3 个 20 天的时期；每个时期的前 12 天用于适应饮食，最后 8 天用于收集数据。TMR（18.1%粗蛋白，24.6%酸性洗涤纤维）和 FF（多花黑麦草；15.1%粗蛋白，24.1%酸性洗涤纤维）每天制备和切割，并单独提供给每头奶牛。T100 和 T75 的 DMI 最高，这反映出它们对不同营养素的摄入量大于 T50。在养分的表观总消化率、平均瘤胃 pH 和总挥发性脂肪酸浓度方面，处理组之间没有差异。T50 组奶牛瘤胃 N-NH3 浓度最低，微生物氮向十二指肠的流量最低。与 T50 相比，T100 和 T75 组奶牛的产奶量分别高 8.5%，但处理组之间的乳脂或乳蛋白产量没有差异。T50 组奶牛的乳脂中不饱和脂肪酸（FA）比 T100 组多 8%，主要是因为单不饱和脂肪酸含量较高。此外，T50 组奶牛的亚油酸、瘤胃酸和亚麻酸浓度高于 T100。同时，T75 组奶牛的亚油酸和瘤胃酸浓度高于 T100。T50 和 T75 组奶牛的乳脂 n-6:n-3 比值低于 T100。我们得出结论，在总 DMI 中包含高达 29%的 FF 与 TMR 结合使用不会影响奶牛对养分的摄入或消化或生产性能，并且从消费者的角度来看，会产生更高浓度的理想 FA。
