苜蓿干草切割长度对荷斯坦育成母牛日粮氮平衡和能量代谢的影响

本文旨在研究苜蓿干草切割长度对荷斯坦育成母牛日粮氮平衡和能量代谢的影响.试验以3头8～10月龄、平均体重(300±22)kg的荷斯坦育成母牛为试验动物,采用3×3拉丁方试验设计,以呼吸测热室为研究手段,分别测定了2、4 cm和自然全长3种理论苜蓿干草切割长度日粮的进食粗蛋白质、粪粗蛋白质、尿粗蛋白质和进食能、粪能、尿能、甲烷能、产热量,进而计算出氮平衡和能量平衡的各项主要参数.结果表明,苜蓿干草的切割长度对日粮的总能消化率、消化能代谢率和氮平衡没有显著影响(P>0.05);随着苜蓿干草长度的增加,日粮代谢能沉积率、消化能沉积率和总能沉积率显著(或极显著)降低(P<0.05或P<0.01),甲烷排出量有升高的趋势,但统计上差异不显著(P>0.05).本研究结果提示,荷斯坦8～10月龄育成母牛日粮粗饲料应经适当切短后饲喂.     

苜蓿干草长度对育肥湖羊生长性能和营养物质消化率的影响

文章旨在探讨苜蓿干草切割长度对湖羊增重性能和营养物质表观消化率的影响。试验选择60只体重和日龄相近的断奶湖羊,随机分为4组,对照组日粮中的苜蓿干草为自然长度,其余3组分别饲喂切割长度为5、15和25 mm的苜蓿干草,预饲期为10 d,正试期为90 d,在饲喂试验结束前的最后10 d开展消化试验。试验结果表明,苜蓿干草切割长度对育肥羔羊的干物质采食量具有显著影响,育肥羔羊的干物质采食量随苜蓿干草切割长度的增加而降低。苜蓿干草切割长度对育肥羔羊的平均日增重具有显著影响,以苜蓿切割长度为15 mm具有最大日增重。育肥羔羊的营养物质表观率受苜蓿干草长度的影响显著,日粮营养物质的表观消化率随苜蓿干草切割长度的增加而增加。因此,在育肥羔羊饲料配制过程中,应考虑苜蓿干草的切割长度,本试验中以苜蓿干草切割长度为15 mm具有最佳生长性能。     

小黑麦干草对羔羊生产性能及采食行为的影响

为探究小黑麦(×Triticale Wittmack)干草对舍饲羔羊生产性能和采食行为的影响,本研究选用18只舍饲湖羊公羔,随机分为对照组、试验Ⅰ组和Ⅱ组,每组6只;对照组饲喂基础日粮,试验Ⅰ组和Ⅱ组在基础日粮中分别用10%、20%的小黑麦干草等量替代粗料。结果表明:Ⅰ组试验羊的平均日增重为189.72 g,显著高于对照组和Ⅱ组(P<0.05);试验羊采食量随小黑麦干草添加比例的增加而降低,Ⅱ组采食量显著低于Ⅰ组和对照组(P<0.05),采食时长极显著高于Ⅰ组和对照组(P<0.01);Ⅰ组试验羊排泄次数显著高于对照组(P<0.05),与Ⅱ组无显著差异(P>0.05);Ⅰ组试验羊反刍周期、反刍时间、反刍食团数和食团咀嚼总次数都极显著高于Ⅱ组(P<0.01)。综上可知,小黑麦干草作为粗饲料在羔羊日粮中适宜添加比例为10%,这为小黑麦干草饲料化开发利用提供了理论基础。     

苜蓿制粒对准噶尔双峰驼采食行为的影响

试验旨在研究苜蓿制粒对准噶尔双峰驼采食行为的影响。选取6峰平均体重为（203.80±22.07）kg、健康的准噶尔双峰母驼,随机分成2组,分别饲喂苜蓿长干草（苜蓿组）和苜蓿颗粒（制粒组）。试验期共22 d,在第22 d连续24 h记录准噶尔双峰驼采食量、采食行为和反刍行为。结果表明：与苜蓿长干草组相比,苜蓿制粒可提高准噶尔双峰驼干物质采食量（P<0.05）,降低反刍时间（P<0.05）,降低咀嚼时间（P<0.05）;制粒可降低准噶尔双峰驼每千克干物质反刍时间和咀嚼时间（P<0.05）,但对干物质采食时间无显著影响。由此可见,苜蓿制粒能够提高准噶尔双峰驼干物质采食量,缩短反刍时间和咀嚼时间;制粒可能是提高准噶尔双峰驼生产性能的一种有效方法。     

棕榈酸与叶酸对荷斯坦育成公牛营养物质消化率、氮平衡和血液指标的影响

试验旨在研究棕榈酸(PA)与叶酸(FA)对荷斯坦育成公牛营养物质消化率、氮平衡和血液指标的影响。选用16头10月龄荷斯坦育成公牛,采用2×2因子的4×4拉丁方设计,分别在无PA日粮和含3%PA的日粮中以FA和过瘤胃叶酸(RPFA)的形式添加3.6 mg/kg FA,每期试验包括20 d预试和5 d正式试验。结果表明:PA和RPFA对营养物质消化率、氮平衡和血液指标无交互作用(P>0.05);日粮添加PA其干物质、有机物、中性洗涤纤维和酸性洗涤纤维消化率降低(P<0.05),消化氮和沉积氮降低(P<0.05),沉积氮/采食氮提高(P<0.05);日粮添加RPFA其干物质和有机物消化率提高(P<0.05),沉积氮、沉积氮/采食氮与沉积氮/消化氮增加(P<0.05);日粮添加PA或RPFA其血液葡萄糖浓度无显著影响(P>0.05),白蛋白与总蛋白含量提高(P<0.05),FA浓度增加(P<0.05),同型半胱氨酸浓度降低(P<0.05)。日粮添加PA其血液游离脂肪酸和β-羟丁酸浓度增加(P<0.05),添加RPFA则降低(P<0.05)。综上可知,育成牛日粮添加3%的PA或含FA 3.6 mg的RPFA可提高氮利用率。     

TMR中不同长度的苜蓿干草对泌乳奶牛生产性能的影响

试验旨在研究泌乳奶牛TMR中添加不同长度的苜蓿干草对奶牛采食及产奶性能的影响。采用3个3×3拉丁方试验研究了TMR中苜蓿干草长度分别为1、3、5 cm时对3头头胎及6头经产泌乳奶牛的采食及产奶性能的影响。结果表明:TMR中的苜蓿干草长度变化对奶牛的DM采食量无显著影响(P0.05);当苜蓿干草长度从1 cm增加到3 cm和5 cm时,奶牛的NDF、ADF及peNDF摄入量均显著增加(P0.05);3 cm和5 cm长度的苜蓿干草较1 cm的能显著提高奶牛4%FCM产奶量、产奶效率及乳脂率(P0.05)。结果提示,泌乳奶牛TMR中苜蓿干草以较长的5 cm为宜;较长的苜蓿干草不影响奶牛的干物质采食量,能增加其有效纤维的摄入量,提高其4%FCM产奶量、产奶效率及乳脂率。     

TMR中苜蓿干草长度对奶牛瘤胃发酵的影响

试验旨在研究奶牛TMR中苜蓿干草长度变化对奶牛瘤胃发酵参数的影响。将3头安装永久瘤胃瘘管的中国荷斯坦奶牛采用3×3拉丁方试验研究了TMR中苜蓿干草长度变化对奶牛的瘤胃pH、NH3-N浓度及挥发性脂肪酸含量的影响。结果表明:奶牛的瘤胃pH及NH3-N含量随TMR中的苜蓿干草长度增加有所升高,但均未达显著水平(P>0.05);增加TMR中苜蓿干草长度能改变奶牛的瘤胃发酵模式,TMR苜蓿干草长度为5 cm的奶牛瘤胃中乙酸平均含量显著高于1 cm的(P<0.05),其丙酸平均含量则显著低于1 cm的(P<0.05),乙酸/丙酸的比值显著高于1 cm的(P<0.05)。奶牛瘤胃中丁酸含量和总VFA含量各处理间没有明显变化。结果提示,泌乳奶牛TMR中苜蓿干草长度增加有利于奶牛维持较高的瘤胃pH,同时能改变瘤胃的发酵模式。     

苜蓿鲜草部分替代苜蓿青干草对奶牛生产性能和血清生化指标的影响北大核心CSCD

本试验旨在研究苜蓿鲜草替代不同比例苜蓿青干草对奶牛生产性能、消化代谢和血清生化指标的影响。选用18头体重、胎次、产奶量相近,处于泌乳中期的健康荷斯坦奶牛,随机分成3组,每组6头。对照组饲喂基础饲粮,试验Ⅰ组和试验Ⅱ组分别饲喂以苜蓿鲜草替代基础饲粮中50%和75%苜蓿青干草的试验饲粮。预试期15 d,正试期30 d。结果表明:1)苜蓿鲜草替代不同比例苜蓿青干草对奶牛干物质采食量和产奶量均无显著影响(P>0.05),但各试验组乳体细胞数均显著低于对照组(P<0.05)。2)苜蓿鲜草替代不同比例苜蓿青干草对奶牛营养物质表观消化率无显著影响(P>0.05)。3)苜蓿鲜草替代不同比例苜蓿青干草对奶牛血清中总蛋白、白蛋白、球蛋白、胆固醇、葡萄糖、甘油三酯、高密度脂蛋白、低密度脂蛋白含量及谷丙转氨酶、谷草转氨酶、碱性磷酸酶活性均无显著影响(P>0.05)。试验Ⅰ组奶牛的血清尿素氮含量显著高于对照组和试验Ⅱ组(P<0.05),对照组和试验Ⅱ组之间无显著差异(P>0.05)。4)与对照组相比,试验Ⅰ组和试验Ⅱ组的经济效益均有所增加,其中试验Ⅱ组净增收益最高,为9.06元/(头·d)。综合得出,苜蓿鲜草可以部分替代奶牛饲粮中苜蓿青干草而不影响生产性能、消化代谢和血清生化指标,且能增加经济效益。     

甘蔗渣作为粗饲料对奶牛生产性能、养分消化和采食行为的影响

文章旨在评价甘蔗渣作为粗饲料对泌乳奶牛采食量、消化率、采食行为、泌乳量、乳成分及微生物蛋白合成等方面的影响。试验选择10头初始体重为(450±25.6)kg,泌乳天数为(143.7±30.7)d的杂交奶牛为研究对象,试验采用5×5拉丁方设计,饲喂周期为5个21 d(1~14 d为适应期,15~21 d为数据采集期)。试验日粮分为对照日粮、45%、50%、55%和60%甘蔗渣日粮。结果:对照组与45%和50%甘蔗渣组干物质、有机物、总可消化养分摄入量、干物质和有机物消化率无显著差异(P>0.05),而55%和60%甘蔗渣组干物质和有机物消化率最低(P<0.05)。甘蔗渣组与对照组对中性洗涤纤维摄入量和表观消化率的影响具有显著差异(P<0.05),其中45%甘蔗渣组奶牛的非纤维碳水化合物摄入量和消化率与对照组相似(P>0.05)。日粮甘蔗渣添加水平对营养物质的摄入量和消化率呈显著线性降低(P<0.05)。60%甘蔗渣组较对照组显著降低了奶牛反刍时间,显著提高空闲时间(P<0.05)。奶牛的反刍时间、反刍和采食效率随日粮甘蔗渣添加水平的升高显著线性降低(P<0.05),而空闲时间随饲粮中甘蔗渣含量的增加线性增加(P<0.05)。结论:日粮添加甘蔗渣降低了奶牛日产奶量,但添加水平为45%~50%时可以使奶牛泌乳量达到12 kg/d。     

TMR日粮不同颗粒大小对奶牛采食行为的影响

试验选择6头体况良好,产奶天数(DIM)接近的荷斯坦奶牛,采用3×3重复拉丁方设计,通过给奶牛饲喂由不同颗粒片段大小(长切割L,短切割S,中等水平M)的玉米青贮组成的TMR日粮来研究其对奶牛采食、反刍行为等的影响。结果表明:降低日粮颗粒片段大小,奶牛的干物质采食量(DMI)、中性洗涤纤维采食量(NDFI)及酸性洗涤纤维采食量(ADFI)均下降,但各处理组间差异不显著(P>0.05);物理有效中性洗涤纤维采食量(peNDFI)也下降,L组与S组间差异显著(P<0.05);降低日粮颗粒大小,奶牛的采食时间、反刍时间及总咀嚼时间下降,L组与S组间奶牛的采食和反刍时间差异显著(P<0.05);奶牛的总咀嚼时间L组与M组、M组与S组间差异显著(P<0.05),而L组和S组间差异极显著(P<0.01)。试验表明,改变日粮颗粒大小对奶牛的DMI等影响不显著,对奶牛的咀嚼活动则有显著的影响。     

Effects of physically effective fiber on chewing activity, ruminal fermentation, and digestibility in goats

The objective of this study was to evaluate the effects of physically effective NDF (peNDF) in goat diets containing alfalfa hay as the sole forage source on feed intake, chewing activity, ruminal fermentation, and nutrient digestibility. Four rumen-fistulated goats were fed different proportions of chopped and ground alfalfa hay in a 4 × 4 Latin square design. Diets were chemically similar but varied in peNDF content: low, moderate low, moderate high, and high. Dietary peNDF content was determined using the Penn State Particle Separator with 2 sieves (8 and 19 mm) or 3 sieves (1.18, 8, and 19 mm). The dietary peNDF content ranged from 1.9 to 11.7% using the 2 sieves and from 15.2 to 20.0% using the 3 sieves. Increasing forage particle length increased intake of peNDF, but decreased DMI linearly (P = 0.05). Ruminating and total chewing time (min/d) were increased linearly (P = 0.001 and 0.007, respectively) with increased dietary peNDF, resulting in a linear reduction (P < 0.001) in the duration of time that ruminal pH was less than 5.8 (10.9, 9.0, 1.2, and 0.3 h/d, respectively). Increasing dietary peNDF tended to increase the molar proportion of propionate linearly (P = 0.08) and decrease the molar proportion of butyrate (P = 0.09), but did not affect total VFA concentration. Increasing dietary peNDF linearly decreased the apparent digestibility of OM, NDF, and ADF in the total tract (P = 0.009, 0.003, and 0.008, respectively). This study demonstrated that increasing the dietary peNDF contained in alfalfa hay forage stimulated chewing activity and improved ruminal pH status, but reduced nutrient intake and efficiency of feed use.     

Effect of exogenous fibrolytic enzyme on ruminal fermentation and digestibility of alfalfa and rye-grass hay fed to lambs

This experiment was carried out to study the effect of a directly fed exogenous fibrolytic enzyme on intake and digestion of DM, OM, protein, NDF, ADF, and hemicellulose of alfalfa and ryegrass hay by sheep. Four diets were randomly assigned to four ruminally cannulated lambs using a 4 x 4 Latin square design, repeated in time, with a factorial arrangement (2 x 2) of diets: 1) alfalfa hay; 2) alfalfa hay + exogenous fibrolytic enzymes (enzyme); 3) ryegrass hay; and 4) ryegrass hay + enzyme. Lambs consumed more DM and OM from alfalfa than from ryegrass hay (P < 0.001). The ADF intake was not different between the hays, but NDF intake was lower for alfalfa (P < 0.001). For both hays, the enzyme increased intake of DM (P < 0.01), as well as OM and CP (P < 0.05); however, NDF and ADF intake were not changed. Alfalfa hay had higher apparent digestibility of DM, OM, and CP (P < 0.001), but lower digestibility for NDF, ADF, and hemicellulose. The enzyme increased apparent digestibility of CP, hemicellulose (P < 0.05), and NDF (P < 0.10) for alfalfa. Also, for both hays, the enzyme improved N balance because lambs retained more N (P < 0.05). The enzyme increased (P < 0.05) total VFA concentration (3 and 6 h) for both hays. Results from this trial indicate that directly fed exogenous fibrolytic enzymes may change ruminal fermentation, intake, and digestibility of forages with different nutritive value.     

苜蓿青贮料替代苜蓿青干草对奶牛生产性能及乳品质的影响

试验旨在探讨苜蓿青贮料替代不同比例苜蓿青干草对奶牛生产性能、乳品质、营养物质表观消化率、血液生化指标及经济效益的影响。选取体重、产奶量、胎次相近的健康泌乳中期中高产中国荷斯坦奶牛15头,随机分为3组,每组5个重复,每个重复1头牛。对照组饲喂4.0 kg苜蓿青干草,试验A、B组分别用4.4,8.8 kg苜蓿青贮料代替2.0和4.0 kg等干物质的苜蓿青干草,正试期64 d。结果表明,1)各组间干物质采食量差异不显著(P>0.05),B组产奶量显著低于对照组(P<0.05),A组与对照组、B组间差异不显著(P>0.05); 2)用50%,100%的苜蓿青贮料替代等干物质的苜蓿青干草,其乳蛋白、乳脂率、乳糖均有所改善,但只有B组的乳脂率显著高于对照组(P<0.05),其余指标各组间差异均不显著(P>0.05);3)A、B组与对照组的中性洗涤纤维表观消化率、钙表观消化率无显著性差异(P>0.05),A、B组间粗蛋白和磷表观消化率差异不显著(P>0.05),但是粗蛋白表观消化率均显著低于对照组、磷表观消化率均显著高于对照组(P<0.05);4)苜蓿青贮料替代苜蓿青干草其血清总蛋白、白蛋白、血尿素氮、血糖、二氧化碳结合力等指标没有显著性改变(P>0.05);5)试验A、B组经济效益均有所增加,其中A组的净增收益最高,为0.61元/(头·d)。综上,用4.4 kg苜蓿青贮料代替2.0 kg苜蓿青干草对中高产奶牛是适宜的,能提高其生产性能,改善乳品质,增加收益。     

Relationships between chewing behavior, digestibility, and digesta passage kinetics in steers fed oat hay at restricted and ad libitum intakes

The objective of this study was to evaluate the relationships between chewing behavior, digestibility, and digesta passage kinetics in steers fed oat hay at restricted and ad libitum intakes. Four Hereford steers, with an initial average BW of 136 kg, were used in an experiment conducted as a balanced 4 × 4 Latin square with 4 treatments (levels of intake) and 4 periods. Animals were fed lopsided oat hay (Avena strigosa Schreb.) at 4 levels of intake (as a percentage of BW): 1.5, 2.0, 2.5, and ad libitum. Digestibility, chewing behavior, and digesta passage kinetic measurements were recorded during the experimental period. Chewing rates during eating and ruminating [(chews?min(-1))/g of DMI?kg(-1) of BW?d(-1)] decreased (P = 0.018 and P = 0.032, respectively) with increased DMI (g?kg(-1) of BW?d(-1)), whereas total chewing and total time spent on each chewing activity increased. Calculated total energy expended by the chewing activity was 4.2, 4.4, 5.2, and 5.3% of ME intake for DMI of 1.5, 2.0, and 2.5% of BW and ad libitum, respectively, indicating that adjustments in animal chewing behavior may be a mechanism of reducing energy expenditure when forages are fed at restricted intake. Hay digestibility decreased (P < 0.001) with increased DMI (r = -0.865). Digesta mean retention time (h) was strongly correlated with DMI (r = -0.868) and OM digestibility (r = 0.844). At reduced intake, hay digestibility was enhanced (P < 0.001) by extending digesta retention time and by increasing chewing efficiency, highlighting the relationship between chewing behavior and the digestive process. Fractional outflow rate of particulate matter from the reticulorumen (k(1)) was positively correlated with total chews, emphasizing that the decrease in particle size caused by chewing facilitates particle flow through the digestive tract. Increased hay intake also increased (P < 0.001) k(1), whereas passage rate of the liquid phase, transit time, and rumen fill were not affected (P > 0.05). The latter was correlated with rumen volume (r = 0.803). In conclusion, the results of this study indicate that animals fed at restricted intake increased chewing rate when eating and ruminating, which, along with a longer digesta retention time, contributed to enhance feed digestibility.     

A comparison between the nutritive value of short-cutting cycle, high temperature-dried alfalfa and timothy hay for horses.

The objective was to evaluate the nutritive value of short-cutting cycle, high temperature-dried (SCCHTD) alfalfa compared to timothy hay. This was achieved by carrying out 4 x 4 Latin Square digestibility trial using 4 Thoroughbred (one three-quarter Thoroughbred) horses (mean liveweight, 531 kg). The four dietary treatments were 0AA (timothy hay only), 33AA (0.33 alfalfa: 0.67 timothy hay), 67AA (0.67 alfalfa: 0.33 timothy hay) and 100AA (alfalfa only). Digestibility data were obtained by using acid-insoluble ash to estimate apparent digestibility coefficients of nutrients. Rate of passage of the feedstuff was determined using chromium-mordanted hay. Plasma triglyceride and cholesterol concentrations were estimated. The digestibilities of organic matter (0.63), energy (0.57) and crude protein (0.74) of the alfalfa were significantly (P less than 0.001) higher than those for the hay (0.45, 0.43 and 0.36 respectively). The fibre components of alfalfa and hay were digested to the same extent but the ether extract of alfalfa was less well digested. Alfalfa saponins had no consistently significant effects on plasma cholesterol and triglyceride values but may contribute to the negative digestibility of alfalfa ether extract. We conclude that SCCHTD alfalfa is of much higher nutritive value than timothy hay when fed to Thoroughbred horses.     

不同加工方式苜蓿干草在肉羊瘤胃内的降解及对消化代谢的影响

选用12只安装有永久性瘤胃瘘管的1.5岁杂交一代(无角陶赛特×小尾寒羊)肉用羯羊,随机分成3组,研究日粮中不同加工方式(整株、颗粒、草粉)苜蓿干草在瘤胃内的降解及其对肉羊消化代谢的影响。试验结果表明:苜蓿干草经粉碎及颗粒处理后,DM、CP、NDF在瘤胃内的降解率较整株组有显著提高(P<0.05),但ADF降解率未有明显变化(P>0.05)。不同加工方式(整株、颗粒、草粉)苜蓿干草对DM、OM、NDF、ADF表观消化率没有影响(P>0.05),但加工成颗粒及粉料使氮的利用率显著提高(P<0.05)。3种不同加工方式下DM、OM、NDF、ADF表观消化率分别高达71.74%～72.18%、73.67%～74.22%、66.69%～68.48%、45.64%～52.41%。     

Digestibility and rate of passage by lambs of water-stressed alfalfa

Two lamb digestion experiments were conducted to evaluate the effect of alfalfa [Medicago sativa (L.)] grown under varying levels of water deficiency (stress) on the rate of passage and digestibility of various fibrous components. Experiment 1 consisted of a randomized complete block design in which 12 Suffolk X Hampshire crossbred wethers averaging 40 kg were fed alfalfa hay grown at three (10, 15 or 20 cm water/ha) levels of water per harvest. Experiment 2 consisted of a switchback design in which four Hampshire wethers averaging 45 kg were fed alfalfa hay grown at two (5 or 20 cm/ha) levels of water per harvest. Forage yields ranged from 1,420 (10 cm/ha in Exp. 1) to 4,200 (20 cm/ha in Exp. 2) kg/ha. In both experiments, water stress reduced cell wall constituents (neutral detergent fiber), acid detergent fiber, lignin and cellulose content of the alfalfa hay. Organic matter digestibility was decreased when the percentage of leaves fell below 60% at the highest yield. Digestibility of N and the rate of NDF digestibility were not affected by water stress. The second experiment additionally included nutrient balance and rate of passage measurements. Greater (P less than .10) amounts of N and P were absorbed from water-stressed than nonstressed hay. Ruminal retention time of particulate markers tended (P less than .10) to increase with greater water stress. The results of this study are interpreted to indicate that while moderate water stress may have little effect on in vivo digestibility of alfalfa, severe stress may reduce digestibility of fibrous fractions and total organic matter.     

Effects of forage offering method on performance,rumen fermentation,nutrient digestibility and nutritional behaviour in Holstein dairy calves

The potential effect of dietary forage supplementation on the performance and rumen development in dairy calves is well established. However, limited research has been directed to the comparative effects of forage offering methods on calf performance. The objective of the present study was to determine the effects of forage provision methods (total mixed ration or free choice) on the performance, nutrient digestibility, rumen fermentation and nutritional behaviour in newborn calves. Forty‐five Holstein dairy calves (3 days of age and 41 ± 2 kg of body weight) were assigned to the following three groups (n = 15): (i) starter without forage provision (CON), (ii) starter supplemented with 10% alfalfa hay (AH) as a total mixed ration (AH‐TMR) and (iii) starter and AH as a free‐choice provision (AH‐FC) for a period of 70 days. All the calves were offered 5 l of milk/day from day 3 to 50, and 2.5 l/day from day 50 until weaning on day 56. Dry matter intake (DMI) was greater (p < 0.01) in the AH‐TMR and AH‐FC treatments than in the CON during the pre‐ and post‐weaning periods. Calves fed the AH‐FC diet showed the highest post‐weaning DMI among the treatments. The calves receiving ad libitum forage tended (p = 0.08) to increase crude protein digestibility and overall volatile fatty acids (VFA) concentrations in the rumen. No differences were observed among the treatments at the time spent on standing, lying, eating and performing non‐nutritive oral behaviours. Compared to CON calves, animals in the AH‐TMR treatment spent more time (p < 0.05) ruminating. In conclusion, our data suggest that forage supplementation in both forage offering methods increased total DMI, ruminal pH and ruminating time in dairy calves. Hence, there is no benefit in the free‐choice provision of AH in dairy calves.     

Effects of forage source and particle size on chewing activity,ruminal pH,and saliva secretion in lactating Holstein cows

The present study investigated the effects of dietary forage source (quality) and particle size on chewing activity, saliva secretion, and ruminal pH. Twelve multiparous lactating Holstein cows, four of which were ruminally cannulated, were used in a replicated 4 × 4 Latin square experimental design with a 2 × 2 factorial arrangement of treatments. Cows fed wild‐rye hay diets had longer daily eating times than cows fed oaten hay diets. Treatments had no effect on ruminating time; therefore, resting time varied inversely to eating time. Neither the rate nor the amount of saliva secretion while eating, ruminating, or resting was affected by diet, resulting in similar total daily saliva secretions across treatments (231 L/day). Total volatile fatty acids (VFAs) in the ruminal fluid from animals fed oaten hay diets were higher than those from animals fed wild‐rye hay diets; further, VFAs increased with decreasing forage particle size (FPS). Consistent with elevated VFA concentrations, reducing FPS and including oaten hay in the diet decreased mean ruminal pH and increased the daily time of ruminal pH under 5.8. Results of this study suggest that forage source and particle size affect ruminal pH might be via variations in VFA production rather than increased salivary recycling of buffering substrates.     

Effects of supplemental alfalfa hay on the digestion of soybean hull-based diets by cattle

We evaluated the optimal level of alfalfa inclusion in soybean hull-based diets. In Exp. 1, 20 Holstein steers (319 kg of BW) were used in a complete block design. Treatments included a soybean hull mix (95.7% soybean hulls, 3% molasses, 0.5% urea, 0.8% mineral mix; DM basis) fed alone (100:0) or with 10.4, 20.7, or 30.9% (DM basis) coarsely chopped alfalfa hay (90:10, 80:20, and 70:30, respectively) or alfalfa alone (0:100). Diets were fed once daily at 1.75% (DM basis) of BW. In some cases, orts were present, which caused DM, OM, and NDF intakes to decrease (linear, P < 0.05) as alfalfa was added to the diets. Digestibilities of DM, OM, and NDF decreased linearly (P < 0.05) as alfalfa was added to the diets, but quadratic responses (P < 0.05) indicated that positive associative effects occurred between soybean hulls and alfalfa. Liquid dilution rates increased (linear, P < 0.05) with alfalfa additions to the diets and also demonstrated positive associative effects between soybean hulls and alfalfa (quadratic, P < 0.05). Solid passage rates were similar for 100:0 and 0:100 but were increased (quadratically and cubically, P < 0.05) when combinations of soybean hulls and alfalfa were fed. In Exp. 2, in vitro NDF digestibilities were measured for soybean hulls, alfalfa, and a blend of 85% soybean hulls and 15% alfalfa, each with no N source or supplemented with casein or urea to ascertain the effects of protein from alfalfa on digestibility. Disappearances were increased (P < 0.05) by addition of urea or casein, but no interactions between substrate and N supplement were observed. Addition of 30% alfalfa to diets consisting primarily of soybean hulls led to positive associative effects on diet digestibility, but alfalfa additions led to increased liquid and solid passage rates, suggesting that the benefit was not a result of slower passage of soybean hulls from the rumen.