Beck P A, Hutchison S, Stewart C B, Shockey J D, Gunter S A
University of Arkansas, Division of Agriculture, Southwest Research and Extension Center, Hope, AR 71801, USA.
J Anim Sci. 2007 Feb;85(2):527-35. doi: 10.2527/jas.2006-358. Epub 2006 Oct 23.
Twelve 0.81-ha crabgrass (Digitaria ciliaris [Retz.] Koel.) hay fields were harvested at 21, 35, and 49 d of regrowth (average phonological growth stage of 30, 51, and 56, respectively). Increased harvest interval exhibited a linear decrease (P < 0.01) in CP (14.1, 13.7, and 10.6% of DM, respectively) and increase (P < 0.01) in NDF (65.3, 70.6, and 70.2% of DM, respectively) and ADF (35.7, 38.9, and 42.7% of DM, respectively). Hays were incorporated into 3 diets that contained 20% (DM basis) crabgrass hay, ground corn (33%), and soybean hulls (32%). Diets contained 14.4, 14.4, and 13.6% CP; 1.83, 1.72, and 1.81 Mcal of NE(m)/kg; and 1.21, 1.10, and 1.17 Mcal of NE(g)/kg; respectively. Diets were fed to beef calves in 12 pens at a rate of 2.3% (DM basis) of BW in 1 experiment (n = 120, initial BW 210 +/- 4.4 kg) and ad libitum in another experiment (n = 60, initial BW 207 +/- 4.4 kg). To measure passage rate of the hay and concentrate portions of the diets, 12 heifer calves (BW = 145 +/- 4.5 kg) were individually fed at 2.3% of BW for 14 d and dosed with Dy-labeled soybean hulls and Yb-labeled hay. In situ DM digestibility of the hays and diets were determined using 3 ruminally cannulated steers (BW = 584 +/- 10.4 kg). Harvest interval did not affect (P > or = 0.11) ADG of limit-fed calves during the diet acclimation or growing phases (average 0.32 and 0.80 kg, respectively) or ADG of calves fed ad libitum (average 1.21 kg). Dry matter intake of calves fed ad libitum averaged 7.9 kg/d (3.28% of BW) and was not affected (P > or = 0.22) by harvest interval. Gain:feed was not affected (P > or = 0.20) by harvest interval (0.13 and 0.15 for limit-fed and ad libitum-fed calves, respectively). Increased harvest interval linearly increased (P < 0.01) ruminal retention time of the hay and tended (P = 0.06) to linearly increase ruminal retention time of the concentrate portions of the diet. Harvest interval linearly decreased (P < or = 0.05) the extent of degradability and effective degradability of DM and NDF of hays, but DM disappearance of the total diet did not differ (P > or = 0.35). In the conditions of this study, increasing harvest interval of crabgrass hay from 21 to 49 d had no deleterious impact on animal performance or efficiency of gain when fed to growing calves in a high-concentrate mixture.
在12块面积为0.81公顷的马唐（Digitaria ciliaris [Retz.] Koel.）干草田，分别在再生21、35和49天（平均物候生长阶段分别为30、51和56）时进行收割。随着收割间隔增加，粗蛋白（分别占干物质的14.1%、13.7%和10.6%）呈线性下降（P < 0.01），中性洗涤纤维（分别占干物质的65.3%、70.6%和70.2%）和酸性洗涤纤维（分别占干物质的35.7%、38.9%和42.7%）呈线性增加（P < 0.01）。将干草配制成3种日粮，每种日粮含有20%（干物质基础）的马唐干草、粉碎玉米（33%）和大豆皮（32%）。日粮的粗蛋白含量分别为14.4%、14.4%和13.6%；净能（维持）分别为1.83、1.72和1.81兆卡/千克；净能（生长）分别为1.21、1.10和1.17兆卡/千克。在1项试验中，将日粮以体重2.3%（干物质基础）的比例饲喂给12个栏中的肉牛犊（n = 120，初始体重210±4.4千克），在另一项试验中自由采食（n = 60，初始体重207±4.4千克）。为测定日粮中干草和精料部分的通过速率，给12头小母牛犊（体重 = 145±4.5千克）个体饲喂占体重2.3%的日粮，持续14天，并分别用镝标记的大豆皮和镱标记的干草进行灌服。使用3头装有瘤胃瘘管的阉牛（体重 = 584±10.4千克）测定干草和日粮的干物质原位消化率。收割间隔对限饲犊牛在日粮适应期或生长阶段的平均日增重（分别平均为0.32和0.80千克）或自由采食犊牛的平均日增重（平均为1.21千克）没有影响（P≥0.11）。自由采食犊牛的干物质采食量平均为7.9千克/天（占体重的3.28%），不受收割间隔的影响（P≥0.22）。料重比不受收割间隔的影响（P≥0.20）（限饲和自由采食犊牛分别为0.13和0.15）。收割间隔延长使干草在瘤胃中的滞留时间呈线性增加（P < 0.01），日粮精料部分在瘤胃中的滞留时间有线性增加的趋势（P = 0.06）。收割间隔使干草干物质和中性洗涤纤维的降解程度及有效降解率呈线性下降（P≤0.05），但日粮总干物质消失率没有差异（P≥0.35）。在本研究条件下，将马唐干草的收割间隔从21天延长至49天，在高浓度混合料中饲喂生长犊牛时，对动物生产性能或增重效率没有不利影响。
