夏季补饲对放牧条件下泌乳牦牛生产性能及血液生理、生化、抗氧化指标的影响

本试验旨在研究夏季补饲对放牧条件下泌乳牦牛生产性能及血液生理、生化、抗氧化指标的影响。试验采用2×2双因子设计,选用24头体重[(218.0±19.5) kg]相近的健康带犊泌乳牦牛,随机分为4个组(每组6头),即自然放牧组(NG组)、氨基酸补饲组[SA组,补饲15 g/(d·头)过瘤胃赖氨酸+5 g/(d·头)过瘤胃蛋氨酸]、精料补饲组[SC组,补饲1.2 kg/(d·头)精料]和氨基酸+精料补饲组[SAC组,补饲15 g/(d·头)过瘤胃赖氨酸+5 g/(d·头)过瘤胃蛋氨酸+1.2 kg/(d·头)精料]。预试期9 d,正试期23 d。结果表明:1)补饲氨基酸、精料及两者交互作用对泌乳牦牛的总产奶量和平均日产奶量无显著影响(P0.10)。与NG组相比,补饲精料显著提高了泌乳牦牛的平均日增重(P0.05),而补饲氨基酸对泌乳牦牛的平均日增重无显著影响(P0.10)。与NG组相比,补饲氨基酸具有提高犊牛的平均日增重的趋势(P=0.098),补饲精料及氨基酸和精料交互作用显著提高了犊牛的平均日增重(P 0.05)。2)与NG组相比,补饲氨基酸具有增加泌乳牦牛血液平均红细胞蛋白量(P=0.089)和降低平均血小板体积(P=0.084)的趋势。补饲氨基酸、精料及两者交互作用对泌乳牦牛其余血液生理指标无显著影响(P0.10)。3)补饲氨基酸、精料及两者交互作用对泌乳牦牛血清生化和抗氧化指标无显著影响(P0.10)。由此可见,夏季补饲精料+氨基酸能够同时促进放牧条件下泌乳母牦牛和犊牛的平均日增重。     

泌乳期云南半细毛羊的蛋白质需要量

本试验旨在研究泌乳期云南半细毛羊的蛋白质需要量。选择50只预产期接近、体重接近的泌乳期云南半细毛羊,随机分为5组(每组10只),分别饲喂蛋白质水平为8.85%、10.55%、12.49%、14.50%和15.95%的试验饲粮。饲养试验共104 d,其中预试期14 d,每组选择实际产羔日期接近、产后体重接近的8只试验羊进入为期90 d的正试期。分别在正试期的第20、50、80天从每组选择5只母羊进行为期5 d的消化代谢试验。结果显示：1)云南半细毛羊泌乳期蛋白质沉积量[RP,g/(kg W^0.75·d)]与蛋白质摄入量[PI,g/(kg W^0.75·d)]间的回归方程为：泌乳第20天,RP=0.425PI-1.916(R²=0.978);泌乳第50天,RP=0.434PI-2.101 (R²=0.984);泌乳第80天,RP=0.446PI-2.147(R²=0.998)。方程的截距即母羊每天的内源尿蛋白质和代谢粪蛋白质的损失量,也就是维持净蛋白质需要量,因此云南半细毛羊泌乳第2...     

环颈雉幼雏期饲粮适宜的能量浓度与蛋白质水平的研究

为探讨环颈雉幼雏期饲粮适宜的能量浓度与蛋白质水平,本研究选用240只1日龄环颈雉进行3(ME:2650,2900和3100kcal/kg)×5(CP:21.5,24.0,26.5,29.0和31.5%)二因子交叉饲养试验和代谢试验。试验结果表明,环颈雉幼雉期饲粮添加赖氨酸和蛋氨酸时,适宜 CP/ME 应为90.3～93.3克/兆卡,且适宜 ME 浓度与CP 水平分别不应低于2900kcal/kg 和26.5%。不论饲粮 ME 浓度与 CP 水平如何,环颈雉的增重率模式均相同,即1～14日龄其增重率迅速提高,并在8～14日龄达到最高,此后15～24日龄则逐渐降低。饲粮 ME 浓度与 CP 水平对环颈雉氮沉积量(克/日、只)与代谢能值(千卡/日、只)的互作效应均显著(P<0.05)。氮沉积率随着饲粮 ME 浓度与 CP 水平的提高而分别显著提高与降低(P<0.05)。能量代谢率随着饲粮 CP 水平的提高而降低。     

过瘤胃蛋氨酸在不同蛋白水平泌乳牛日粮中应用研究

为应对泌乳早期产生的蛋白负平衡现象，向泌乳牛日粮中补饲过瘤胃蛋氨酸是一种常用的策略，但过瘤胃蛋氨酸的实际使用效果存在差异。近年的氨基酸平衡理论中，认为奶牛代谢氨基酸若过量供给，会抑制其乳蛋白的产生，但该理念目前尚存争议。本试验通过在生产实践环境下，对大样本泌乳牛开展过瘤胃蛋氨酸的补饲试验。试验发现每头牛每天补饲12g过瘤胃蛋氨酸，新产期（产后1～30d）的泌乳牛产奶量会出现显著的下降（P=0.011），而同一牛群在高产期时，补饲过瘤胃蛋氨酸对产奶量无显著影响。本试验结果与近年奶牛氨基酸营养研究中总结的代谢蛋白供给-乳蛋白产量模型的设想相符合。基于新理念，奶牛的蛋白营养调控可根据实际情况逐渐添加过瘤胃氨基酸，寻找最适合的添加量。同时，旧模型中保持一定赖蛋比的理念依然是奶牛氨基酸平衡的重要参考。若需要进一步验证新奶牛氨基酸平衡模型，应设计自身对比的饲养试验继续开展研究。     

过瘤胃蛋氨酸对奶牛产奶量以及乳成分的影响

选用16头泌乳中期奶牛,每头牛饲喂过瘤胃蛋氨酸(SmartamineTM)0、8、12和16g/d,研究其对泌乳中期奶牛产奶量以及乳成分的影响。结果表明,与对照组相比,补饲12和16g/d过瘤胃蛋氨酸能提高泌乳中期奶牛产奶量,补饲8g/d过瘤胃蛋氨酸奶牛产奶量下降5.73%;12g/d组产奶量提高0.62%,但差异均不显著;16g/d组产奶量提高10.84%,差异显著。补饲过瘤胃蛋氨酸能提高乳蛋白率和乳脂率水平,但差异不显著。补饲16g/d过瘤胃蛋氨酸牛奶乳蛋白量提高11.49%,乳脂肪量提高了13.11%。     

补饲女贞子对泌乳奶牛生产性能及血液生化指标的影响

试验旨在研究补饲女贞子对泌乳奶牛生产性能及血液生化指标的影响。选择48头健康的泌乳中期中国荷斯坦奶牛,随机分成4组,每个处理组12头奶牛,对照组饲喂全混合日粮(TMR),N1、N2、N3组分别在饲喂TMR日粮的基础上补饲150、300、450 g/d女贞子。预试期1周,正试期7周。结果表明,与对照组相比,补饲450 g/d女贞子可显著提高泌乳奶牛4%校正乳产量(P<0.05),补饲150 g/d女贞子可显著提高泌乳奶牛乳脂含量(P<0.05),而对泌乳奶牛干物质采食量、产奶量及乳蛋白、总固形物含量和体细胞数均无显著影响(P>0.05);与对照组相比,补饲女贞子可显著降低泌乳奶牛血液中甘油三酯含量(P<0.05),而对其他血液生化指标均无显著影响(P>0.05)。综上所述,补饲女贞子具有提高泌乳中期奶牛生产性能、改善机体脂类代谢的作用。     

Supplementation of High Protein and High Fat Concentrates Affects Milk Yield and Milk Composition of Donkeys (Equus asinus)

本试验旨在研究补饲高蛋白质、高脂肪精饲料对驴产乳量和乳成分的影响.选择3-7岁的健康泌乳母驴34头,设A(12头)、B(10头)和C(12头)3个区,共5个处理.所有驴饲喂基础饲粮.每个区均设对照组,各试验组驴分别补饲粗蛋白质水平为31.44％(试验1组,A区,4头)、粗脂肪水平为25.77％ [20％棉籽油(试验2组,A区,4头)、20％葵花籽油(试验3组,B区,5头)、20％菜籽油(试验4组,C区,6头)]的试验精饲料1.5 kg/d.预试期14 d,正试期14 d.结果表明:1)除含20％葵花籽油的试验精饲料外,其余试验精饲料采食量(＞1300 g/d)均达到预期的采食量,且未出现消化异常,表明所用精饲料适口性较好,驴对它们有较好的适应性;2)补饲含20％棉籽油和含20％菜籽油的试验精饲料均显著提高了驴日均产乳量(P＜0.05),驴日均产乳量可达1.5 kg/d,而日均总泌乳量可达4 kg/d;3)补饲不同试验精饲料对乳成分无显著影响(P＞0.05),驴乳中乳蛋白、乳糖、粗灰分含量较稳定,而乳脂含量变化非常大.总之,补饲高蛋白质、高脂肪的精饲料可提高驴产乳量,但对乳成分的影响不明显.     

叶酸和维生素B_(12)在补充蛋氨酸的情况下对奶牛泌乳性能的影响

本试验旨在研究补饲叶酸是否能通过提高甲基的形成从而影响泌乳奶牛的生产性能和VB12对此代谢过程的影响。给予这种假设,补充提供甲基供体的蛋氨酸应能减少叶酸和VB12的需要。试验选用60头经产的荷斯坦奶牛,根据泌乳量平均分配到10个处理组。在每个处理组中,3头奶牛饲喂基础日粮（蛋氨酸量,1.83%的代谢蛋白）,另外3头在基础日粮的基础上添加18g瘤胃保护性蛋氨酸（蛋氨酸量,2.23%的代谢蛋白）。试验期为产犊前3周至产后16周,各蛋氨酸水平组奶牛或不补饲维生素,或周肌肉注射160g叶酸,或周肌肉注射160mg叶酸和补饲VB1210mg。结果表明,各处理组对干物质采食量没有影响（13.4kg/d&#177;0.4kg/d（产前）,21.8kg/d&#177;0.4kg/d（产后））。补饲瘤胃保护性蛋氨酸不影响产奶量。叶酸和VB12一起补充有增加产奶量的趋势。这种效应在泌乳的前4周效果更加明显。各处理组对乳脂产量没有影响。在泌乳早期,叶酸和VB12提高了乳糖、粗蛋白质和总固形物产量,但这种效应随着泌乳期的延长逐渐消失。与不补饲维生素组相比,单独补充叶酸或与VB12一起补充降低了血浆中的高半胱氨酸含量。本试验结果表明,叶酸和VB12不能通过提高甲基集团的供给影响泌乳奶牛的生产性能。     

13～18周龄笼养蛋鸭适宜蛋白质和蛋氨酸水平的研究

用 32 4羽满 1 2周龄的金定鸭 ,通过饲养试验、代谢试验、屠宰试验和对试鸭产蛋期 (1 9～ 2 8周龄 )产蛋性能的观察 ,研究了在等能条件下(ME :1 1 51MJ/kg) ,不同蛋白质水平 (CP :1 3 %、 1 5 %、 1 7% )和蛋氨酸水平 (Met/CP :0 0 1 7、 0 0 2 2、 0 0 2 7)组成的 9种饲粮对 1 3～ 1 8周龄笼养蛋鸭的生长性能、养分利用、体成分沉积和产蛋期产蛋性能的影响。结果表明 :该阶段饲粮粗蛋白、蛋氨酸水平对体增重影响不显著 (P >0 0 5) ;体增重与蛋氨酸 (% )呈一定的正相关 (r=0 4574) ;CP为 1 3%、Met/CP为 0 0 2 7组采食量一直较稳定、较高 ,且饲料效率又好。代谢试验 :不同粗蛋白、蛋氨酸水平饲粮对试鸭氮存留率和能量的利用率影响显著(P <0 0 5或P<0 0 1 ) ,且它们随饲粮CP水平的升高而降低 ,随蛋氨酸水平升高而升高 ;磷的利用率也分别以CP为 1 3%的水平和Met/CP为 0 0 2 7的水平极显著地高于其他水平对磷利用率 (P <0 0 1 )。屠宰试验 :当Met/CP为 0 0 2 7时 ,体氮沉积量和体磷沉积量最佳。产蛋性能 :开产日龄和高峰日龄与 1 3～ 1 8周龄CP食入量呈弱的负相关 (r=- 0 1 83 3和r=- 0 0 984) ,与蛋氨酸食入量呈正相关 (r =0 5780和r =0 435 0 )。饲粮粗蛋白、蛋氨酸水平对 1 9～ 2 8周龄     

利用饲料原料中的营养成分和可消化营养成分含量建立肉羊常用蛋白质饲料原料代谢能的预测模型

本试验应用套算法分析肉羊常用蛋白质饲料原料中的营养成分含量和可消化营养成分对有效能值的影响,基于饲料原料中的营养成分含量和可消化营养成分建立蛋白质饲料原料代谢能(ME)的预测模型。选取36只22月龄、体重为(52.6±1.4)kg的杜泊×小尾寒羊F1代杂交去势肉羊,采用完全随机区组设计分为6个处理,包括1个基础饲粮处理和5个试验饲粮处理,每个处理6只羊。利用消化代谢试验和呼吸代谢试验并结合套算法计算5种蛋白质饲料原料的消化能(DE)和ME,并分析蛋白质饲料原料DE、ME与该原料中营养成分[干物质(DM)、有机物(OM)、总能(GE)、粗蛋白质(CP)、粗脂肪(EE)、中性洗涤纤维(NDF)、酸性洗涤纤维(ADF)]和可消化营养成分[可消化干物质(DDM)、可消化有机物(DOM)、可消化粗蛋白质(DCP)、可消化粗脂肪(DEE)、可消化中性洗涤纤维(DNDF)、可消化酸性洗涤纤维(DADF)]含量之间的相关关系。结果表明:饲料原料中的OM、DDM、DOM、DCP含量与DE和ME均存在极显著正相关(P0.01);另外,DADF与DE存在极显著负相关(P0.01),与ME存在显著负相关(P0.05)。通过饲料原料中的营养成分含量预测ME的方程为:ME(MJ/kg)=-82.855+2.391OM(%)+1.802EE(%)-6.21GE(MJ/kg)-0.121ADF(%)(R2=0.910,n=30,P0.01);通过饲料原料中的可消化营养成分含量预测ME的方程为:ME(MJ/kg)=-5.564+30.526DOM(%)+55.402DEE(%)(R2=0.841,n=30,P0.01);通过饲料原料中的可消化营养成分含量与DE共同预测ME的方程为:ME=-5.787+1.126DE(MJ/kg)+20.769DEE(%)(R2=0.879,n=30,P0.01)。综上所述,在本试验中,蛋白质饲料原料中的部分营养成分和可消化营养成分含量与ME之间存在显著相关,可通过饲料原料中的营养成分和可消化营养成分含量对肉羊蛋白质饲料原料的ME进行有效预测。     

Effects of wheat protein in milk replacers on abomasal emptying rate in calves

Diarrhoea is a condition with tremendous impact on calf health. Infectious agents play a dominant role; however, non‐infective factors may also contribute to pathogenesis of diarrhoea. One factor, the abomasal emptying rate, is mainly influenced by the composition of feed. The aim of the study was to assess the influence of different protein sources in milk replacers on abomasal emptying rate and clinical parameters. The effect of increasing age of the calves on abomasal emptying was also evaluated. The study compared abomasal emptying rates and clinical parameters in calves, which were fed either milk replacer containing only whey protein or one which partially contained wheat protein. Abomasal emptying rate was estimated by ultrasonography. Ten calves were used in the study over 18 days, and each calf was fed 3 periods of 3 days length using different milk replacers in an alternating crossover design. The abomasum was emptied significantly faster when the wheat protein containing milk replacer was fed (half‐emptying time wheat protein 49.1 ± 4.1 min, half‐emptying time milk protein 59.1 ± 7.4 min); however, clinical parameters and weight gain did not differ between the feeding regimes. Age did not significantly influence abomasal emptying rate. As milk replacers containing wheat proteins increased abomasal emptying rate, they may have a higher potential to initiate diarrhoea, especially if high volumes are fed. Thus, the feeding regimes are likely to be even more important when such milk replacers are used.     

Influence of abomasal infusion of high levels of lysine or methionine, or both, on ruminal fermentation, eating behavior, and performance of lactating dairy cows

Four multiparous late-lactation Holstein cows were fed a basal ration designed to be co-limiting in intestinally absorbable supplies of methionine and lysine. Cows were supplemented with no amino acids, lysine by abomasal infusion to 140% of the calculated intestinally absorbable requirement, methionine by abomasal infusion to 140% of requirement, or both amino acids in a 4 x 4 Latin square design with 28-d periods. Unsupplemented cows consumed 23.8 kg/d of dry matter and produced 36.9 kg/d of milk containing 3.70% fat, 3.22% protein, and 4.82% lactose. Cows ate less dry matter and produced less milk and milk lactose, and tended (P = .06 or .08) to produce less milk protein when abomasally infused with methionine alone or together with lysine. Infusion of lysine alone resulted in production values numerically between those of unsupplemented cows and those cows supplemented with methionine alone or together with lysine. Evaluation of the results with two metabolic models of dairy cows indicated that performance of unsupplemented cows may have been limited by delivery of metabolizable or digestible protein, or intestinally absorbable lysine, isoleucine, or histidine, depending on the metabolic model used to evaluate animal performance. Regardless, results are consistent with those using nonruminant species, which have shown that imbalanced profiles of intestinally absorbable amino acids are associated with reduced dry matter intake and animal performance. Results also show that negative effects on performance of lactating dairy cows can occur if methionine is supplied at levels substantially in excess of calculated intestinally absorbable requirements, either alone or together with lysine.     

Assessment of feeding varying levels of Metabolizable energy and protein on performance of transition Murrah buffaloes

Fifteen close up pregnant Murrah buffaloes of mean body weight (668.3 ± 24.03) kg, lactation number (2.8 ± 0.17) and expected producing ability (EPA) (2125.7 ± 46.34) were randomly distributed into three groups each of five animals to investigate the performance at different levels of metabolizable energy and protein. Control group was fed as per ICAR Nutrient requirements of animals (2013) recommendation whereas treatment group (1) high metabolizable energy and high metabolizable protein (HMEMP) and group (2) low metabolizable energy and low metabolizable protein (LMEMP) were offered with ration containing 15% more and 15% less ME and MP, respectively. The feeding trial was carried out for the period of 40 days before parturition and continued for 120 days after parturition. Intake of dry matter (DM) (%BW) was similar among experimental groups. Metabolizable energy (ME) (MJ/100 kg BW) and metabolizable protein (MP) (g/100 kg BW) intake was highest in HMEMP followed by control and LMEMP group, respectively. Digestibility trial of 7 days was conducted at 60 days post-partum and it was observed that apparent digestibility coefficients (%) of DM, organic matter (OM), crude protein (CP), ether extracts (EE), neutral detergent fiber (NDF) and acid detergent fiber (ADF) were similar among the experimental groups. Milk yield (kg/kg DMI) was similar among treatment groups whereas 6% fat corrected milk (FCM) was lower in LMEMP group as compared to HMEMP and control. No significant effect of dietary MP and ME levels on milk composition was observed among experimental groups. There were no significant difference in non esterified fatty acid (NEFA), blood urea nitrogen(BUN), growth hormone (GH) and insulin like growth factor-1(IGF-1) concentration among different experimental groups whereas concentration of immunoglobulin G (IgG) (μg/ml) was found to be lower in LMEMP. The study results indicate that nutrient digestibility and lactation performance was not affected with 15% variation in intakes of ME and MP in lactating Murrah buffaloes.     

Nutritional properties of dried salmon silage for broiler feeding

The aim of this study was to evaluate the chemical composition, energy and amino acid profile of dried salmon silage (DSS) for broilers. The DSS was obtained by acid digestion of salmon mortalities and subsequently co‐dried with wheat bran in a 70:30 ratio (70 parts silage and 30 parts wheat bran). Samples of DSS were evaluated for chemical composition, gross energy, nitrogen‐corrected true metabolizable energy (TME_n), mineral content, total and digestible amino acids for broilers, and amino acid score. The chemical composition of DSS was (mean ± SD): moisture (12.3 ± 0.8%), crude protein (44.0 ± 1.1%), ether extract (5.0 ± 2.4%), crude fiber (3.3 ± 0.4%) and ash (9.4 ± 0.6%). The gross energy and TME_n for broilers were 4 069 kcal/kg and 2 613 kcal/kg, respectively. The DSS mineral composition showed a high content of calcium (1.01%) and phosphorus (1.08%). The DSS had high levels of digestible methionine (0.74%), lysine (2.27%), and threonine (1.16%), and did not present limiting amino acids for broilers. Nutritional composition of DSS showed high protein content with an amino acid profile considered to be suitable as a protein source for broiler feeding.     

Effect of level and source of nutrients in late gestation on subsequent milk yield and composition and fertility of dairy cows

The effect of level and source of nutrients in late gestation on food intake, milk yield, milk composition and fertility in the subsequent lactation were evaluated in a randomized block design experiment involving 76 cows. Four experimental diets, based on grass silage, were offered to provide two levels of metabolizable energy (ME) intake (80 and 125 MJ/cow/day) either from 100:0 or 40:60 forage:concentrate (F:C) ratios for the last 28 days of gestation. Post-calving all cows were offered the same grass silage supplemented with 7 kg/day concentrates. For treatments 80 ME, 125 ME and 100:0 F:C, 40:60 F:C total dry matter (DM) intakes were 6.8, 10.5, 9.0 and 8.4 kg DM/day and ME intakes were 80, 126, 102 and 104 MJ/day, respectively, during the last 4 weeks of gestation. For weeks 1-16 of the subsequent lactation, treatment 125 ME increased milk fat content and yield but had no effect on food intake, milk protein content or onset of cyclicity. Treatment 125 ME increased condition score and live weight at calving. Altering the F:C ratio of the diets in late gestation had no effect on food intake, milk yield, milk composition or on the onset of cyclicity in the subsequent lactation. Cow parity and level of nutrient intake in late gestation provided the best fit relationships for the yields of fat and fat plus protein (R² relationships=0.49 and 0.52, respectively) during weeks 1-16 of lactation. It is concluded that increasing nutrient intake in late gestation increased milk fat content and yield but had no effect on milk protein concentration. The improved milk fat content and yield observed in a previous study was due to increased nutrient intake rather than altering the F:C ratio. Furthermore there was no measurable benefit in food intake or animal performance in the subsequent lactation through feeding concentrates in late gestation.     

Dormant Season Grazing: Effect of Supplementation Strategies on Heifer Resource Utilization and Vegetation Use

Grazing dormant forage under low-input heifer development strategies typically exposes cattle to low-quality forage. Protein supplementation while grazing dormant range can enhance heifer growth and reproductive performance. We examined resource utilization of heifers and the effects of dormant season grazing on residual vegetation characteristics under two supplementation management strategies. Approximately 100 weaned composite heifer calves were randomly selected and placed into one of two supplementation treatments in each of 2 yr, one receiving a free access 62% crude protein self-fed concentrate and the other receiving a daily hand-fed 20% crude protein cake. Grazing occurred from December (2015 and 2016) through March (2016 and 2017). Thirty transects were randomly located within each pasture for measuring vegetation quality and structure before and after grazing. Daily space use and behavior was evaluated for 21 individuals within each treatment using global positioning system (GPS) collars and resource utilization functions. Heifers supplemented with concentrated protein spent more time grazing per day than heifers supplemented with cake (6.92 ± 0.18, 6.24 ± 0.17 h). Relative use by heifers in the cake treatment was negatively related to horizontal distance from the supplement delivery site early to midwinter ($\stackrel{?}{\overline{\beta }}$ = ? 0.41 ± 0.16, ? 0.53 ± 0.17). Both treatments selected grazing locations relative to standing biomass of perennial grasses ($\stackrel{?}{\overline{\beta }}$ = 0.0005 ± 0.00004) and crude protein ($\stackrel{?}{\overline{\beta }}$ = 0.12 ± 0.007). However, resource selection was highly variable among individuals for both supplementation treatments. We found no treatment effects on pre-post grazing differences in residual cover of litter, grass, forbs and shrubs (P > 0.24). However, the time period when grazing occurred had an effect on residual vegetation conditions (P < 0.01). Our results indicate high levels of variability in grazing site selection by heifers, suggesting future research should incorporate individual animal measurements in an attempt to account for individual animal variability.     

Influence of postruminal supplementation of methionine and lysine, isoleucine, or all three amino acids on intake and chewing behavior, ruminal fermentation, and milk and milk component production.

Four multiparous Holstein cows were fed a basal diet balanced with the Cornell Net Protein and Carbohydrate System (CNCPS). Diets were formulated to be co-limiting in intestinally absorbable supplies of methionine, lysine, and isoleucine. Cows were supplemented with no amino acids (control); lysine and methionine in a ruminally protected form; isoleucine by abomasal infusion; or lysine, methionine, and isoleucine in a 4x4 Latin square arrangement of treatments with 28-d periods. Performance of cows on all treatments was lower than expected due to low intake of DM that could have been caused by the high fiber level of the basal diet. This high fiber level was likely responsible for the high daily chewing times for cows fed all diets, which was consistent with the high ruminal pH values. Intake of DM and its components were not influenced by any treatment. Milk protein percentage tended to be higher when cows were fed diets supplemented with ruminally protected lysine and methionine; however, production of milk, milk fat, and milk lactose were not affected by any treatment. Cows tended to have a higher milk lactose proportion and tended to produce more milk and milk lactose when they were abomasally infused with isoleucine alone. However, when cows were supplemented with all three amino acids, milk production and composition did not differ from that of cows fed the unsupplemented diet. Use of the CNCPS to evaluate the performance of the cows fed the unsupplemented diet suggested that these cows may have been colimited by intestinally absorbable supplies of lysine, isoleucine, and methionine in addition to metabolizable protein. Evaluation of the unsupplemented diet with an alternate model, Shield, suggested that cows fed the unsupplemented diet may have been colimited by intestinally absorbable supplies of lysine, isoleucine, and arginine. Results suggest that enhanced delivery of intestinally absorbable isoleucine may stimulate milk lactose synthesis.     

Effect of dietary crude protein level and degradability on ruminal fermentation and nitrogen utilization in lactating dairy cows

The objectives of this experiment were to investigate the effects of two ruminally degradable protein (RDP) levels in diets containing similar ruminally undegradable protein (RUP) and metabolizable protein (MP) concentrations on ruminal fermentation, digestibility, and transfer of ruminal ammonia N into milk protein in dairy cows. Four ruminally and duodenally cannulated Holstein cows were allocated to two dietary treatments in a crossover design. The diets (adequate RDP [ARDP] and high RDP [HRDP]), had similar concentrations of RUP and MP, but differed in CP/RDP content. Ruminal ammonia was labeled with 15N and secretion of tracer in milk protein was determined for a period of 120 h. Ammonia concentration in the rumen tended to be greater (P = 0.06) with HRDP than with ARDP. Microbial N flow to the duodenum, ruminal digestibility of dietary nutrients, DMI, milk yield, fat content, and protein content and yield were not statistically different between diets. There was a tendency (P = 0.07) for increased urinary N excretion, and blood plasma and milk urea N concentrations were greater (P = 0.002 and P = 0.01, respectively) with HRDP compared with ARDP. Milk N efficiency was decreased (P = 0.01) by the HRDP diet. The cumulative secretion of ammonia 15N into milk protein, as a proportion of 15N dosed intraruminally, was greater (P = 0.003) with ARDP than with HRDP. The proportions of bacterial protein originating from ammonia N and milk protein originating from bacterial or ammonia N averaged 43, 61, and 26% and were not affected by diet. This experiment indicated that excess RDP in the diet of lactating dairy cows could not be efficiently utilized for microbial protein synthesis and was largely lost through urinary N excretion. At a similar MP supply, increased CP or RDP concentration of the diet would result in decreased efficiency of conversion of dietary N into milk protein and less efficient use of ruminal ammonia N for milk protein syntheses.     

利用全消化道灌注营养技术研究蛋氨酸水平与生长绵羊血浆总蛋白之间的关系

选用4只3~4月龄夏洛莱×无角陶赛特生长期公羊,分别安装瘤胃瘘管和真胃瘘管,利用全消化道灌注营养技术研究蛋氨酸(Met)水平对血浆总蛋白(TP)的影响。试验采用4×3不完全拉丁方设计,4个蛋氨酸水平0.00、1.76、3.52 g/16g N和7.04 g/16g N分别作为试验处理II、II、II和IV。试验进行3期,每期10 d。最后1 d采集血液样品。结果表明:不同处理间上午灌注前的血浆总蛋白没有显著差异(P>0.05)。而下午灌注过程中处理IV的血浆总蛋白显著高于处理I(P<0.05),处理II和处理III的血浆总蛋白与处理I相比有升高的趋势,但差异没有达到显著水平(P>0.05)。蛋氨酸水平(g/16gN)与灌注期间的血浆总蛋白(g/L)之间存在二次曲线关系(P=0.019)。由此得出,蛋氨酸供应水平对生长绵羊的血浆蛋白有重要影响。     

藏山羊乳主要营养成分及乳酶、乳清蛋白的研究

本文研究了分布于西藏和四川地区的藏山羊乳蛋白、乳糖和乳脂含量,并对乳中4种酶活力及乳清蛋白的组成进行了研究。结果表明:藏山羊乳中3种营养成分存在一定的地区差异,脱脂乳中乳酸脱氢酶,碱性磷酸酶,γ-谷氨酰转肽酶、乳过氧化物酶活力分别为81.9±37.8、7.7±3.5、437.4±93.0、532.7±202.6单位。乳过氧化物酶在体外可被10~(-5)M的硫氰酸根或乳酸根活化。用琼脂糖凝胶电泳可将乳LDH分出LDH_1、LDH_2和LDH_3三带,各带所占百分比例分别为50.6±4.5、31.6±4.2和17.8±3.3,提示乳LDH不是来源于血液。用SDS—PAGE可将乳清蛋白分出5条区带。