精料比例对皖南牛粗饲料采食量和日粮养分表观消化率的影响

本试验研究精料比例对皖南牛粗饲料采食量和营养物质表观消化率的影响。30头去势的体重相近的18月龄皖南牛,随机分成5组,各组根据体重的1.9%、1.6%、1.3%、1.0%和0.7%补充精料,通过饲养试验和消化试验测定粗饲料采食量和日粮养分表观消化率。结果表明:皖南牛的粗饲料采食量随着精料饲喂量的减少而增加,总的干物质采食量(DMI)随着精料饲喂量的减少而降低;日粮的干物质(DM)、有机物(OM)、粗蛋白(CP)、粗脂肪(EE)和总能(GE)的表观消化率随着精料饲喂量的减少而降低;日粮中性洗涤纤维(NDF)和酸性洗涤纤维(ADF)的表观消化率随着精料的减少先升后降,精料饲喂量占体重1.0%的组的NDF和ADF表观消化率最高,分别为60.48%和57.07%。     

Meta分析研究饲粮中性洗涤纤维和淀粉比对奶牛生产性能和乳成分组成的影响北大核心CSCD

本试验旨在采用Meta分析方法研究饲粮中性洗涤纤维(NDF)与淀粉比值对奶牛生产性能和乳成分合成的影响。试验整理了27篇有关奶牛碳水化合物营养的研究,共计123个处理,运用Meta分析方法研究饲粮NDF、淀粉含量以及NDF与淀粉比值与奶牛干物质采食量、产奶量和乳成分的相关性,并进行相应的回归分析。结果显示:相较于饲粮NDF和淀粉含量,饲粮NDF与淀粉比值与奶牛的干物质采食量(R2=-0.799,P<0.01)、产奶量(R2=-0.730,P<0.01)、乳脂率(R2=0.664,P<0.01)和乳蛋白率(R2=-0.788,P<0.01)的相关性更强;饲粮NDF与淀粉比值与奶牛的干物质采食量(P=0.02)、产奶量(P<0.01)、乳脂率(P<0.01)、乳蛋白率(P<0.01)、乳蛋白产量(P<0.01)和乳糖产量(P<0.01)存在显著的一元线性回归关系,饲粮NDF与淀粉比值每增加1,奶牛的干物质采食量、产奶量、乳蛋白产量和乳糖产量分别降低0.81、1.36、0.06和1.50 kg,乳脂率和乳蛋白率分别增加0.11%和0.07%。M eta分析结果表明,饲粮NDF与淀粉比值可作为反映奶牛饲粮碳水化合物组成的营养评价指标,用于指导奶牛的生产和调控乳成分的组成。     

一年生黑麦草青贮料和玉米青贮料中添加蒸汽压片玉米和破碎玉米对奶牛生产性能的影响

选用24头泌乳期荷斯坦奶牛进行为期6周的奶牛饲养试验,采用2×2因素随机区组试验设计,研究以一年生黑麦草青贮料(RS)或以50∶50混合的一年生黑麦草青贮料和玉米青贮料组成的混合料(BLEND)为基础日粮,添加饲喂破碎玉米(GC)或蒸汽压片玉米(SFC)对奶牛生产性能的影响。试验日粮包含49.6%的粗饲料,以全混合日粮的形式饲喂,1次/d,试验期4周,预饲期2周。处理之间没有发现交互作用。饲喂BLEND组比饲喂RS组的奶牛的干物质(DM)、有机物(OM)、中性洗涤纤维(NDF)和酸性洗涤纤维(ADF)的采食量高。但饲喂RS组的OM、NDF和ADF的总消化率高于饲喂BLEND组。测定第4周营养物质消化率,未发现各组间营养物质采食量有差异,但SFC组的DM和OM的消化率要高于GC组。饲喂BLEND的奶牛比饲喂RS的奶牛生产更多的能量校正乳,表现为提高了生产效率。当日粮中添加SFC时,奶牛干物质采食量减少,产奶量增多,但乳中乳脂率较低。与饲喂GC相比,饲喂SFC乳蛋白生成量和生成效率较高。各组间血糖和乳尿素氮生成量相似,但饲喂GC的奶牛比饲喂SFC的奶牛血尿素氮水平要高。本试验的结果表明,与只饲喂黑麦草青贮料相比,饲喂一年生黑麦草青贮料和玉米青贮料效果更好。日粮中添加SFC与GC相比,奶牛生产性能和效率均有一定的提高。     

不同粗饲料组合对奶牛生产性能、表观消化率及乳品质的影响

文章旨在研究不同粗饲料组合对奶牛生产性能、表观消化率及乳品质的影响。试验选取36头体重、胎次、产奶量相近的荷斯坦奶牛,随机分为3组,每组4个重复,每个重复3头。各组均在全混合日粮（TMR）基础上调整粗饲料配比,其中对照组奶牛饲喂100%青贮玉米粗饲料,试验1组奶牛饲喂50%青贮玉米+50%苜蓿干草粗饲料,试验2组奶牛饲喂50%青贮玉米+25%苜蓿干草+25%羊草粗饲料,试验共计60?d。结果显示,（1）试验1、2组奶牛的平均日产奶量（ADMP）比对照组显著提高18.89%、23.13%(P <0.05),且试验1、2组奶牛的料奶比比对照组显著降低15.38%、15.38%(P <0.05)。（2）试验1组干物质（DM）、粗蛋白质（CP）、中性洗涤纤维（NDF）的消化率比对照组显著提高3.85%、4.03%、6.67%(P <0.05),试验2组干物质（DM）、粗蛋白质（CP）、中性洗涤纤维（NDF）的消化率比对照组显著提高5.22%、4.16%、6.71%(P <0.05)。（3）试验1组乳样中乳蛋白率（MPP）比对照组显著提高了3.53%(P <0.05...     

不同日粮对泌乳奶牛干物质采食量及消化率的影响

本试验旨在研究在不同日粮条件下对奶牛干物质采食量(DMI)及养分消化率的影响。用4头安装永久瘤胃瘘管和十二指肠瘘管的泌乳奶牛(体重为483±21kg,泌乳日龄为175±6天)通过4×4拉丁方试验设计,日粮包括30:70CW组(粗料仅由羊草组成)、30:70CCA组(粗料为玉米青贮+苜蓿+羊草)、50:50CCA组和65:35CCA组,共设4期试验,每期23天。30:70CCA组干物质采食量与有机物采食量极显著低于其它日粮组(P<0.01),30:70CCA组能量采食量显著低于其它日粮组,30:70CW组DM、OM在瘤胃消化率(P<0.05)及全肠道消化率(P<0.01)均显著低于其它日粮组;NDF、ADF瘤胃及全肠道消化率均无显著差异。65:35CCA组产奶量极显著高于其它组(P<0.01)。     

Meta分析研究饲粮中性洗涤纤维和淀粉比对奶牛生产性能和乳成分组成的影响

本试验旨在采用Meta分析方法研究饲粮中性洗涤纤维(NDF)与淀粉比值对奶牛生产性能和乳成分合成的影响。试验整理了27篇有关奶牛碳水化合物营养的研究,共计123个处理,运用Meta分析方法研究饲粮NDF、淀粉含量以及NDF与淀粉比值与奶牛干物质采食量、产奶量和乳成分的相关性,并进行相应的回归分析。结果显示:相较于饲粮NDF和淀粉含量,饲粮NDF与淀粉比值与奶牛的干物质采食量(R2=-0.799,P0.01)、产奶量(R2=-0.730,P0.01)、乳脂率(R2=0.664,P0.01)和乳蛋白率(R2=-0.788,P0.01)的相关性更强;饲粮NDF与淀粉比值与奶牛的干物质采食量(P=0.02)、产奶量(P0.01)、乳脂率(P0.01)、乳蛋白率(P0.01)、乳蛋白产量(P0.01)和乳糖产量(P0.01)存在显著的一元线性回归关系,饲粮NDF与淀粉比值每增加1,奶牛的干物质采食量、产奶量、乳蛋白产量和乳糖产量分别降低0.81、1.36、0.06和1.50 kg,乳脂率和乳蛋白率分别增加0.11%和0.07%。M eta分析结果表明,饲粮NDF与淀粉比值可作为反映奶牛饲粮碳水化合物组成的营养评价指标,用于指导奶牛的生产和调控乳成分的组成。     

绵羊常用粗饲料纤维品质的评定及绵羊采食量的模型化研究

研究以绵羊粪作菌源 ,测定了 4类 (豆科、禾本科、秸秆及青贮 )、9种粗饲料及 3个混合粗饲料组中的中性洗涤纤维 (NeutralDetergentFiber,NDF)的体外消化率 (InVitroNDFDigestibility,IVNDFD) ,用可发酵纤维指数 (FermentableFiberIn dex,FFI)对这些粗饲料的纤维品质进行了评定。结果表明 :按FFI的大小对所测定的粗饲料纤维品质进行的排序为青干草 >玉米青贮 >玉米秸 >羊草 >草地早熟禾 >谷草 >混粗C2 >混粗C1 >混粗D >苜蓿 >沙打旺 >苏丹草 ;以不可消化的NDF(UndigestibleNDF ,unNDF)为预测因子 ,建立了预测绵羊干物质随意采食量 (DMI)的模型为DMI豆(g/d·w0 .75) =4 3.4 3/unNDF(%DM) ;DMI禾(g/d·w0 .75) =33.89/unNDF(%DM) ;DMI秸(g/d·w0 .75) =2 3.84 /unNDF(%DM) ;DMI贮(g/d·w0 .75) =2 2 .4 2 /unNDF(%DM)。对以上结果进行比较 ,发现以unNDF为预测因子的DMI模型较以NDF为预测因子的DMI模型更好。     

山东省羊常用粗饲料营养价值评定

试验旨在综合评价从山东省17个市采集的羊常用粗饲料原料的营养价值。试验测定了109个样本10种常用原料的常规营养成分及总能(GE),应用两级离体消化法测定干物质消化率(IVDMD),以计算消化能(DE)和代谢能(ME),并根据预测干物质随意采食量(DMI),进而计算出分级指数(GI)。结果表明,不同粗饲料间的常规养分的差异不能准确地评价饲料营养价值;以NDF、ADF所得GI综合评价粗饲料中营养价值得到苜蓿>冬牧70>地瓜秧>羊草>花生秧>青贮玉米秸>玉米秸>水稻秸>豆秸>麦秸;IVDMD与NDF、ADF均呈显著负相关,而与CP呈显著正相关;DE与NDF、ADF相关性较强,且均呈负相关。     

不同日粮对泌乳奶牛干物质采食量及消化率的影响

本试验旨在研究在不同日粮条件对奶牛干物质采食量(DMI)及养分消化率的影响。用4头安装永久瘤胃瘘管和十二指肠瘘管的泌乳奶牛(体重为483±21kg,泌乳日龄为175±6天)通过4×4拉丁方试验设计,日粮包括70CW组(粗料仅由羊草组成)、30：70CCA组(粗料为玉米青贮 苜蓿 羊草)、50：50CCA组和65：35CCA组,共设4期试验,每期23天。30：70CCA组干物质采食量与有机物采食量极显著低于其它日粮组(P＜0．01),30：70CCA组能量采食量显著低于其它30：70日粮组,CW组DM、OM在瘤胃消化率(P＜0．05)及全肠道消化率均(P＜0．01)显著低于其它日粮组;NDF、ADF瘤胃及全肠道消化率均无显著差异(P＜0．05)。65：35CCA组产奶量显著高于其它组(P＜0．01)。     

禾王草与奶牛常用粗饲料瘤胃降解特性的对比研究

本试验旨在研究2种刈割高度的禾王草干草和青贮、羊草干草、苜蓿干草以及全株玉米青贮共7种粗饲料的瘤胃降解特性。选用4头装有永久性瘤胃瘘管的荷斯坦奶牛为试验动物,采用尼龙袋法评定其干物质(DM)、粗蛋白质(CP)、中性洗涤纤维(NDF)和酸性洗涤纤维(ADF)的72 h瘤胃降解率。结果表明:1)禾王草干草CP含量显著高于羊草干草(P0.05),NDF含量显著低于羊草干草(P0.05);禾王草青贮CP和NDF含量显著高于全株玉米青贮(P0.05)。2)苜蓿干草DM有效降解率最高,与依次降低的全株玉米青贮、2.0 m禾王草青贮、2.5 m禾王草青贮、2.0 m禾王草干草、2.5 m禾王草干草和羊草干草差异显著(P0.05),羊草干草的DM有效降解率显著低于其他粗饲料(P0.05);CP有效降解率以苜蓿干草最高,与2.0 m禾王草青贮差异不显著(P0.05),显著高于依次降低的2.5 m禾王草青贮、2.0 m禾王草干草、全株玉米青贮、2.5 m禾王草干草和羊草干草(P0.05);全株玉米青贮与禾王草青贮的NDF有效降解率差异不显著(P0.05),而显著高于其他粗饲料(P0.05);禾王草青贮72 h时ADF有效降解率显著高于其他粗饲料(P0.05)。由此可知,禾王草有作为奶牛粗饲料的潜力,禾王草经青贮后可以保存营养成分,并可以提高营养成分的瘤胃利用效率。     

The effect of monensin Na on the protein content of cow's milk and further performance criteria

In two feeding experiments with 10 dairy cows each the effect of 200 mg monensin Na per animal and day in rations either rich in roughage or in concentrate was studied. In principle, the reactions caused by monensin supplement did not differ between the two types of rations. Monensin supplements resulted in a slight reduction of feed intake, a significantly lower milk fat content and, as a tendency, also a lower milk protein, particularly casein, content and a diminished amount of fat corrected milk (FCM). The pattern of fatty acids in the rumen was shifted in favour of propionic acid and the live weight gain of the cows was higher in the monensin group. There were no improvements with regard to the expenditure of feed and energy per kg FCM.     

Effect of rumen-protected nutrients on feed intake,body weights,milk yield,and composition in Murrah buffaloes during early lactation

The effect of rumen-protected nutrients (bypass fat, BPF; bypass protein, BPP; or their combination, BPPF) was investigated in Murrah buffaloes during the early stage of lactation. Forty Murrah buffaloes (BW 531.92?±?10.85 kg) just after parturition were randomly distributed into four groups according to parity and milk production. Buffaloes individually fed ration from day 0 to 90 postpartum according to feeding group and nutrient requirement. Control and BPF fed groups received a concentrate mixture, CM1 with 25% rumen-protected protein (using barley, wheat bran, and mustard oil cake), BPP and BPPF groups received a second concentrate mixture, CM2 with 40% rumen-protected protein (using barley, de-oiled rice bran, and cottonseed cake). Bypass fat fed groups (BPF and BPPF) additionally were supplemented with 15 g BPF (Ca salt of long-chain fatty acids) per kg milk yield in their respective concentrate mixtures. Dry matter intake, body weights, body condition score, and total milk yield were similar between groups (P?>?0.05). Fat-corrected milk (FCM) production was improved (14.5%, P?>?0.05) in groups fed BPP and BPPF, while significant (19.45%, P?<?0.05) improvement was observed in BPF-fed group. Overall mean values of milk fat, solid not fat, protein, lactose, and total solids were found to be high (P?<?0.05) in treatment groups as compared with control values. It may be concluded that supplementation with BPP or BPF either alone or in combination positively influences the quality of milk produced in Murrah buffaloes during early lactation and BPF additionally had improvement on the quantitative trait of milk as well.

     

大豆皮替代产奶牛日粮精料中玉米与小麦麸对产奶性能的影响

本试验选用 4 2头荷斯坦产奶牛分为 3组 ,每组 1 4头。采用完全随机化区组设计进行试验。处理为 3种大豆皮替代水平 ,即 :大豆皮分别替代精料中 0 % (对照 )、2 5%和 50 %的玉米与小麦麸 ;区组 ( 4个 )为产奶牛的不同胎次和泌乳月。正式试验期 1 2周。结果表明 ,用大豆皮替代产奶牛精料中 0 %、2 5%和 50 %的玉米和小麦麸 ,日粮干物质、蛋白质进食量、日产奶量、4 %乳脂率校正奶产量、产奶的饲料转化效率、乳蛋白、乳糖、无脂固形物含量均没有明显变化 (P >0 .2 0 ) ,乳脂率随大豆皮替代水平的提高呈直线上升趋势 (P =0 .0 8)。以大豆皮替代精料中 2 5%和 50 %玉米与小麦麸饲粮喂奶牛 ,每千克产奶的饲料成本平均分别降低 0 .0 4 5和 0 .0 57元     

Impact of fat and selected profiles of fatty acids contained in the colostrum and milk of sows of native breeds on piglet rearing

The aim of this study was to evaluate the effect of the level of fat and selected fatty acids found in the milk of sows on the rearing of native breed piglets. Simultaneously, in order to improve the accuracy of the performed analyses, atomic absorption spectrometry was employed in the applied analytic methodology. The experimental animal material comprised 60 sows of the indigenous White Z?otnicka breed. Colostrum and milk were collected on the first and 14th days of lactation. In all, 240 samples were collected. The following parameters were determined in the course of the experiment: number and weight of piglets, body weight gains as well as deaths of piglets. A total of 1270 born piglets was subjected to investigations. The performed experiments demonstrated that, with the progress of the lactation period, the content of fat and saturated fatty acids (SFA) turned out to be statistically significant and showed a growing tendency. Fat increased by about 2% and palmitic acid (C16:0) increased most, that is by 5%. Linolic (C18:2) and linolenic (C18:3) acids revealed decreasing trends. Irrespective of the day of lactation, the level of unsaturated fatty acids (UFA) determined in sows' colostrum and milk was higher in comparison with that of SFA, and the UFA to SFA ratio ranged from 1.84% to 1.33%. Proportions of n‐6 to n‐3 fatty acids were determined at the level of about 1.6:1.0 in the colostrum and 1.3:10 in milk. The highest daily body weight gains were recorded in the case of piglets derived from sows with the highest fat level – 294 g, while in the case of stearic acid (C18:0), the smaller its concentration in the colostrum and milk of the experimental sows, the better body weight gains of piglets – 262 g. At the same time, stearic acid (C18:0) was found to exert a statistically significant effect on piglet mortality at the level of P ≤ 0.05. Its highest concentration caused the highest proportion of deaths among piglets ‐ 16.23%. The performed analysis of correlations that occurred between fat, fatty acids and traits associated with piglet rearing confirmed that linolic acid (C18:2; n‐6) was highly significantly correlated with piglets' body weights (r = 0.456**) and was negatively correlated with piglets' deaths (r = ?0.312). On the other hand, fat revealed correlation with body weight gains of piglets (r = 0.333*_ and a negative correlation with deaths of piglets (r = ?0344*). Recapitulating, the results of the performed experiments revealed that differences in the levels of fat and fatty acids found in sows' colostrum and milk influenced results of piglet rearing. Together with the increase in the content of fat and UFA in sows' colostrum and milk, piglets were characterized by the best body weight, growth rate, as well as by small mortality.     

不同饲喂方式对南方奶牛产奶性能、养分消化和代谢的影响

研究了具有南方奶牛日粮类型特征的相同精粗比日粮的不同饲喂方式对奶牛的采食行为、产奶性能、全肠道养分表观消化率和血清代谢产物的影响。选用体重相近的12头荷斯坦奶牛,采用单因子设计,根据产奶量、胎次及泌乳天数随机分为2组（n=6）,分别为精粗分饲组（SI）和全混合日粮组（TMR）,精饲料：粗饲料均为50：50。试验结果表明：奶牛采食量无差异,在相同精粗比日粮下,TMR饲养技术极显著减少了奶牛的采食时间（P〈0.01）,显著增加了反刍时间（P〈0.05）,TMR组奶牛的乳脂率、4%标准奶产量、乳脂产量、乳糖产量和乳固形物产量分别比SI组显著提高11.20%、11.60%、17.50%、13.21%和9.86%（P〈0.05）,但对奶牛咀嚼行为、全肠道养分表观消化率和血清代谢产物影响不显著（P〉0.05）。在南方奶牛典型日粮采用TMR饲养技术时,与精粗分饲相比,可提高奶牛的产奶性能,但对奶牛的采食量、咀嚼行为、全肠道养分表观消化率和血清代谢产物没有显著影响。     

Negative effects of long-term feeding of high-grain diets to lactating goats on milk fat production and composition by regulating gene expression and DNA methylation in the mammary gland

Background: It is well known that feeding a high concentrate(HC) diet to lactating ruminants likely induces subacute ruminal acidosis(SARA) and leads to a decrease in milk fat production. However, the effects of feeding a HC diet for long periods on milk fatty acids composition and the mechanism behind the decline of milk fat still remains poorly understood. The aim of this study was to investigate the impact of feeding a HC diet to lactating dairy goats on milk fat yield and fatty acids composition with an emphasis on the mechanisms underlying the milk fat depression. Seventeen mid-lactating dairy goats were randomly allocated to three groups. The control treatment was fed a low-concentrate diet(35% concentrate, n = 5, LC) and there were two high-concentrate treatments(65% concentrate, HC), one fed a high concentrate diet for a long period(19 wks, n = 7, HL); one fed a high concentrate diet for a short period of time(4 wk, n = 5, HS). Milk fat production and fatty acids profiles were measured. In order to investigate the mechanisms underlying the changes in milk fat production and composition,the gene expression involved in lipid metabolism and DNA methylation in the mammary gland were also analyzed.Results: Milk production was increased by feeding the HC diet in the HS and HL groups compared with the LC diet(P 0.01), while the percentage of milk fat was lower in the HL(P 0.05) but not in the HS group. The total amount of saturated fatty acids(SFA) in the milk was not changed by feeding the HC diet, whereas the levels of unsaturated fatty acids(UFA) and monounsaturated fatty acids(MUFA) were markedly decreased in the HL group compared with the LC group(P 0.05). Among these fatty acids, the concentrations of C15:0(P 0.01), C17:0(P 0.01), C17:1(P 0.01), C18:1 n-9 c(P 0.05), C18:3 n-3 r(P 0.01) and C20:0(P 0.01) were markedly lower in the HL group, and the concentrations of C20:0(P 0.05) and C18:3 n-3 r(P 0.01) were lower in the HS group compared with the LC group. However, the concentrations of C18:2 n-6 c(P 0.05) and C20:4 n-6(P 0.05) in the milk fat were higher in the HS group. Real-time PCR results showed that the m RNA expression of the genes involved in milk fat production in the mammary gland was generally decreased in the HL and HS groups compared with the LC group. Among these genes, ACSL1, ACSS1 2, ACACA, FAS, SCD, FADS2, and SREBP1 were downregulated in the mammary gland of the HL group(P 0.05), and the expressions of ACSS2, ACACA, and FADS2 m RNA were markedly decreased in the HS goats compared with the LC group(P 0.05). In contrast to the gene expression, the level of DNA methylation in the promoter regions of the ACACA and SCD genes was increased in the HL group compared with the LC group(P 0.05). The levels of ACSL1 protein expression and FAS enzyme activity were also decreased in the mammary gland of the HL compared with the LC group(P 0.05).Conclusions: Long-term feeding of a HC diet to lactating goats induced milk fat depression and FAs profile shift with lower MUFAs but higher SFAs. A general down-regulation of the gene expression involved in the milk fat production and a higher DNA methylation in the mammary gland may contribute to the decrease in milk fat production in goats fed a HC diet for long time periods.     

Effects of a Brown‐midrib corn hybrid on nutrient digestibility in wethers and on dry matter intake,performance, rumen and blood variables in dairy cows

The aim of the present trials was to determine the effect of an experimental Brown‐midrib (Bm) corn hybrid in relation to a commercial corn hybrid (Con) on digestibility in wethers and on dry matter intake (DMI), milk yield and milk composition in dairy cows. Digestibility of crude fibre (CF), neutral detergent fibre (NDFom) and acid detergent fibre (ADFom) were higher for Bm (CF Con: 57.8%; Bm: 67.2%; NDFom Con: 56.8%; Bm: 64.8%; ADFom Con: 52.0%; Bm: 63.9%), but concentration of net energy for lactation did not differ (Con: 6.4 MJ/kg DM; Bm: 6.3 MJ/kg DM). A total of 64 lactating German Holstein cows were assigned to one of the two dietary treatments Con or Bm according to milk yield, lactation number, days in milk and live weight. In Trial 1, cows were fed a total mixed ration consisting of 50% corn silage (Con or Bm) and 50% concentrate on dry matter (DM) basis. In Trial 2, the same animals were fed the respective silage for ad libitum intake and 5.3 kg of concentrate DM per animal per day. In Trial 1, DMI and milk‐fat content were decreased significantly for the Bm‐treatment (DMI Con: 22.5 kg/day; Bm: 21.5 kg/day; milk fat Con: 3.8%; Bm: 3.3%). In Trial 2, milk yield and fat‐corrected milk (FCM) were increased significantly, whereas milk‐fat% was decreased significantly (milk yield Con: 25.8 kg/day; Bm: 29.4 kg/day; FCM Con: 27.2 kg/day; Bm: 29.6 kg/day; fat Con: 4.4%; Bm: 4.0%). Diets did not influence ruminal pH or temperature. Diets, furthermore, did not influence rumination in either trial. Additional research on digestibility and rumen fermentation should, however, be carried out using dairy cows at respective intake levels as trials with wethers cannot be transferred to high‐yielding ad libitum fed cows.     

Ammonia and urea in corn silage-based complete mixed diets for dairy cows

Source of supplemental N was evaluated in three corn silage-based complete mixed diets (CMD) fed to lactating dairy cows. Diets were formulated to be isonitrogenous and contained 60% corn silage and 40% concentrate on a dry matter basis. Diets were: CMD-A, ammoniated corn silage (ammonia provided 16% of total N) plus concentrate; CMD-U, untreated corn silage and concentrate (16% of total N from urea) and CMD-S, untreated corn silage plus concentrate with soybean meal. Ammoniation at 1.0% of dry weight increased crude protein content of silage from 8.5 to 12.7%. Daily means for cows fed CMD-A, CMD-U and CMD-S were: 24.2, 24.3 and 24.5 kg of fat-corrected milk; 3.17, 3.10 and 3.15% milk protein; 3.41, 3.67 and 3.63% milk fat and 3.02, 2.99 and 3.02 kg intake of total dry matter/100 kg body weight. Differences were not significant except for reduced milk fat percentage for cows fed the ammoniated corn silage diet. Both anhydrous ammonia and urea at 16% of total dietary N were found to be practical and economical substitutes for part of the supplemental soy protein. When compared to CMD with all soybean protein, greater savings in feed costs resulted from inclusion of ammoniated corn silage than with inclusion of urea.     

Lactation and reproductive performance of mares fed added dietary fat during late gestation and early lactation

Eighteen pregnant mares were randomly allotted to one of two treatment groups. The control group was fed a conventional concentrate and the fat group was fed a concentrate containing 5% feed-grade rendered fat. Both concentrates had the same nutrient:calorie ratio and were fed in amounts required to maintain zero change in percent body fat of the mares. During the study, which began 60 d prior to expected foaling date and ended 60 d postpartum, mares were monitored for feed intake, body weight, rump fat thickness, ration digestibility, plasma glucose and lipid concentrations, milk composition and reproductive efficiency. Birth weight, growth rate, and plasma glucose and lipid concentrations were also measured in foals. Mares fed fat consumed less concentrate (P<.09 during the last 60 d of gestation but consumed similar amounts of concentrate over 60 d of lactation. Protein and ether extract digestion was higher (P<.05 and P<.09, respectively) in the mares fed fat during the postpartum period. Dietary treatment had no influence on plasma glucose or lipid concentrations of the mares or plasma glucose concentrations of their foals, but foals whose dams were fed fat had higher plasma lipid concentrations at birth (P<.01), d 10 and d 30 (P<.05). Percent fat was higher in milk samples from mares fed fat at d 10 (P<.09, 1.23 vs .99%) and d 60 (P<.01, .72 vs .43%) of lactation. Reproductive performance was not significantly different between treatment groups, however there was a trend for a shorter postpartum interval and fewer cycles per pregnancy in the mares fed added fat. Foals from both groups were of similar size and weight at birth and had similar weight gains over 60 d, however, foals nursing mares fed fat tended to gain more weight in the first week of life (1.85 vs 1.56 kg/d) and have more rump fat at d 60 (.53 vs .44 cm) than foals nursing control mares.     

Digestion in steers and lactational performance of Jersey cows fed diets varying in natural protein level continuously or on alternate days

Five crossbred beef steers (515 kg) were used in a Latin square experiment and 36 lactating Jersey cows (12 primiparous, 310 kg; 24 multiparous, 365 kg) were used in a completely randomized design study to determine effects on characteristics of digestion and lactational performance of daily alternation of the dietary level of natural protein (NP). In Experiment 1, steers were fed diets of 50% bermudagrass hay and 50% concentrate. Concentrate was approximately 18% crude protein (CP), formulated to be 60, 80 or 100% NP (varying proportions of soybean meal, urea and ground corn), and was fed at 1.5% body weight (dry matter basis). These concentrates were fed daily or ones with 60 and 100% NP were fed on alternate days. Alternate day feeding did not markedly affect characteristics of digestion, including ruminal escape of feed protein, and NP level of concentrate fed continuously had no effects either. In Experiment 2, cows were subjected to treatments similar to those in Experiment 1, and performance on d 20-40 of lactation was measured. Concentrate was given at 1 kg (as fed)/2.15 kg milk produced, yielding a dietary concentrate level of approximately 40% (dry matter basis). Alternate feeding depressed (P less than 0.05) overall milk fat percentage. Alternate feeding increased production of milk and protein and body weight of primiparous cows but caused little change with multiparous cows. Besides increasing the dietary level of concentrate, perhaps alternate feeding regimes have utility to lower milk fat level without impairing milk production. Level of NP in concentrate fed continuously did not affect performance by multiparous cows though primiparous cow performance was generally enhanced, possibly because CP intake was adequate for multiparous cows but marginal for primiparous cows. However, overall, efficiency of production of solids-corrected milk rose slightly with increasing NP.