饲粮全棉籽比例对奶牛泌乳性能及乳脂脂肪酸组成的影响

本试验旨在研究饲粮全棉籽比例对奶牛泌乳性能和乳脂脂肪酸组成的影响.试验采用4×4拉丁方试验设计,选择8头泌乳早期的经产中国荷斯坦奶牛(产奶量、胎次、产犊日期接近,健康无疾病),分为4组,每组2个重复,每个重复1头牛.A组饲喂基础饲粮,B、C和D组分别饲喂含5％、10％、15％全棉籽的试验饲粮.每期试验28 d,其中预试期为7d,正试期为21 d.结果表明:随着饲粮全棉籽比例的增加,奶牛产奶量有提高趋势(P＞0.05),校正乳产量极显著提高(P＜0.01).全棉籽极显著地提高了奶牛的乳脂率(P＜0.01),对乳蛋白率、乳糖率和乳非脂固形物率无显著影响(P＞0.05).全棉籽极显著降低了饱和脂肪酸( SFA)的含量(P＜0.01),不同程度地提高了乳中多不饱和脂肪酸( PUFA)和单不饱和脂肪酸(MUFA)的含量(P＜0.05或P＜0.01);短链脂肪酸和中链脂肪酸含量都显著降低(P＜0.05),长链脂肪酸含量有不同程度的提高(P＜0.05或P＜0.01).结果提示,饲粮中添加全棉籽可以提高奶牛产奶量,优化乳脂脂肪酸组成,改善乳脂品质,并以10％为泌乳早期奶牛最佳饲粮全棉籽比例.     

Effects of total replacement of corn silage with sorghum silage on milk yield,composition, and quality

Background: In the last years, difficulties occurring in corn cultivation(i.e., groundwater shortages, mycotoxin contamination) have been forcing dairy farmers to consider alternative silages. Some experiments conducted on lactating cows have proven that the total replacement of corn silage with sorghum silage did not reduce milk yield.However, this kind of substitution involves supplementing sorghum-based diets with grains, to compensate for the lower starch content of sorghum silage compared to corn silage. Change of silage type and inclusion of starch sources in the diet would influence rumen fermentations, with possible effects on milk composition(i.e., fatty acid profile) and coagulation properties. A worsening of milk coagulation properties would have a negative economic impact in Italy, where most of the milk produced is processed into cheese.This study was designed to compare milk composition and quality, with emphasis on fatty acid profile and coagulation properties, in dairy cows fed two diets based on corn or sorghum silage.Results: The sorghum diet reduced milk yield(P = 0.043) but not 4% fat corrected milk(P = 0.85). Feeding sorghum silage did not influence milk contents of protein(P = 0.07) and lactose(P = 0.65), and increased fat content(P = 0.024).No differences emerged for milk concentrations of saturated(P = 0.61) and monounsaturated fatty acids(P = 0.50),whereas polyunsaturated fatty acids were lower(P 0.001) for the sorghum diet. Concentrations of n-6(P 0.001) and n-3 fatty acids(P = 0.017) were lower in milk of cows fed the sorghum diet. Milk coagulation properties did not differ between the two diets, except the "a30"(the curd firmness, expressed in mm, 30 min after rennet addition), that was lower(P = 0.042) for the sorghum diet.Conclusions: Feeding a forage sorghum silage, properly supplemented with corn meal, as total replacement of corn silage maintained milk composition and did not influence negatively milk coagulation properties, which have a great economic relevance for the Italian dairy industry. Thus, silages obtained from forage sorghums could have a potential as substitute of corn silages in dairy cow diets.     

Effect of dietary fish oil on milk yield, fatty acids content and serum metabolic profile in dairy cows

The aim of the study was to evaluate the effects of dietary unprotected fish oil on milk yield, fatty acids content and serum metabolic profile in dairy cows. Forty lactating Polish Holstein-Friesian cows were assigned to two groups. The cows were fed a control basal diet (C group), or a basal diet containing 2% addition of fish oil on mineral carrier (FOM group) during a 8-week period. Supplementing FOM diet of dairy cows had no significant effect on milk fat, milk protein, milk lactose concentration and somatic cells count, but increased the milk yield (36.5 kg/d), (p < 0.05) compared with the control cows (34.28 kg/d). We observed an increase (p < 0.05) in body condition scoring between C and FOM groups. Additionally, higher levels of non-esterified fatty acids and β-hydroxybutyrate acid were noticed in FOM group after 8 weeks of the experiment; however, these serum parameters still were in the reference range. Concentration of insulin was higher (30.40 μU/ml; p < 0.01) in the FOM group compared with the control group (14.03 μU/ml). In the FOM group, significant increase (p < 0.01) in long-chain fatty acids, mainly cis-9, trans-11 CLA and n-3 fatty acids (eicosapentaenoic and docosahexaenoic acids) was observed. The obtained results demonstrated that addition of fish oil to cows' diet could profitably modify the fatty acids in cow's milk.     

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.     

Ingestion of medium chain fatty acids by lactating dairy cows increases concentrations of plasma ghrelin

The purpose of this study was to elucidate the effects of medium-chain fatty acids (MCFAs) on plasma ghrelin concentration in lactating dairy cows. Five early-lactating Holstein cows were randomly assigned to 2 dietary treatments in a crossover design with 2-wk periods. Treatments consisted of diets supplemented or not (control) with calcium salts of MCFAs (MCFA-Ca; 1.5% dry matter). Plasma hormone and metabolite concentrations in blood samples taken from the jugular vein were measured on the morning of feeding on day 14 of each period. Dry matter intake, milk protein, and lactose content of cows fed the MCFA-Ca diet were decreased compared with controls, but with no change in milk yield. Plasma ghrelin concentrations were higher in cows fed the MCFA-Ca diet; however, no significant effect was found on glucagon-like peptide-1 concentrations in plasma. Plasma insulin concentrations decreased, but plasma glucagon concentrations remained unchanged in cows fed the MCFA-Ca diet. The concentrations of nonesterified FAs, total cholesterol, and β-hydroxybutyrate in plasma increased in these cows. In conclusion, dietary MCFAs increase the plasma ghrelin concentrations in lactating dairy cows.     

Effects of Supplemental Carbohydrate Sources on Lactation Performance, Nitrogen Balance, and Ruminal Fermentation in Dairy Cows Fed Energy-Deficient Total Mixed Rations

The effects of supplemental carbohydrate (CHO) sources on milk yield and composition,nitrogen (N) balance,and ruminal fermentation were evaluated in lactating dairy cows fed energy-deficient total mixed rations (TMR).Fifty-six lactating Holstein cows (36.8 ±3.4 kg/d of milk yield; 152 ±26days in milk [ DIM ] ) were randomly assigned to one of four diets:( 1 ) basal TMR ( control ) ; ( 2 ) basal TMR + 1.25 kg/d sucrose (SUC) ; ( 3 ) basal TMR + 2.12 kg/d steam-flaked corn ( SFC ) ; ( 4 ) basal TMR + 2.23 kg/d wheat (WHE).The trial lasted 70 days,including the first 10 days of adaptation.Simultaneously,a 4 × 4 Latin square trial was conducted with four ruminally cannulated cows of similar DMI (Dry Matter Intake) fed on the above four diets.Each testing period lasted 18 days:15 days for adaptation and 3 days for sampling.Cows fed SUC-,SFC-,and WHE-supplemented diets produced 1.6,2.9,and 0.8 kg/d,respectively,more milk than those on the basal TMR control diet,but the difference was not significant (P =0.160).However,the production of energy-corrected milk of cows fed CHO-supplemented diets improved significantly (P =0.020),and the yield of 4％ fat-corrected milk tended to be higher (P =0.063 ) than in control animals.Percentages of milk protein,lactose and solidsnot-fat (SNF) increased significantly in cows fed CHO-supplemented diets ( P ＜ 0.05 ),and yields of milk protein and SNF were significantly higher (P＜0.05); yields of milk fat and lactose were somewhat higher ( P ＜ 0.10 ).Cows receiving supplementary CHO diets consumed more DM (Dry Matter) ( P =0.023 ) ; however,there was no significant difference in N retention,digestibility,or utilization efficiency among the treatments (P ＞ 0.10 ).The average ruminal pH was lowest in cows supplemented with SUC,while that in cows supplemented with SFC and WHE was only slightly reduced (P =0.025 ).Ruminal NH3-N concentration was highest with no supplementary CHO ( P =0.017 ),and changes in postfeeding time were similar across the diets.Total volatile fatty acid concentration was significantly lower in control animals than in those on SUC- and WHE-supplemented diets ( P =0.001 ) ; significant dietary responses were observed in the concentrations of acetate,butyrate,and branched-chain fatty acids and in the acetate-to-propionate ratio ( P ＜ 0.001 ).These results indicate that supplementation with different CHO sources in energy-deficient diets substantially improved the balance of energy and N in the rumen,altered ruminal fermentation,and improved lactation performance in dairy cows.     

柑橘渣对奶牛泌乳性能、养分消化率及乳成分的影响

试验评估不同水平柑橘渣对奶牛泌乳性能、养分消化及乳成分的影响.将32头泌乳性能一致的奶牛随机分为4个组,每组4个重复,每个重复2头.对照组饲喂粗脂肪水平为3％的日粮,处理组分别饲喂粗脂肪水平为5.5％的日粮同时添加0 (T1)、5％(T2)和10％ (T3)柑橘渣.结果 显示,与对照组相比,处理组奶牛的粗脂肪摄入量、干...     

丙酸钙对泌乳早期奶牛泌乳性能和代谢产物的影响

选用32头经产奶牛,根据泌乳期、上个泌乳期305 d产奶量和预产期,采用随机区组设计分为4组,对照组饲喂基础日粮,处理1、2、3组分别在基础日粮基础上添加丙酸钙100、200、300 g/d.结果显示,日粮添加丙酸钙对奶牛的采食量、乳脂率、乳蛋白率、乳糖率和乳干物质率无显著影响,200、300 g/d组产奶量和饲料转化效率显著高于对照组(P<0.05).200、300 g/d组血浆葡萄糖和胰岛素浓度显著高于对照组(P<0.05),而血浆游离脂肪酸和β-羟丁酸浓度显著低于对照组(P<0.05);200、300 g/d组尿酮浓度显著低于对照组和100 g/d组(P<0.05).试验结果表明,丙酸钙适宜添加量为200 g/d.     

阴外动脉灌注乳脂前体物对奶牛产奶量及乳腺内短链脂肪酸摄取规律的影响

本试验研究了阴外动脉灌注乳脂前体物对奶牛产奶量及乳腺内短链脂肪酸摄取规律的影响。选择8头健康荷斯坦奶牛分为2组,每组4头牛。采用2×2交叉试验设计,2组分别饲喂2种不同粗饲料[苜蓿(MF组)、玉米秸秆(CS组)]的饲粮,饲粮的精粗比为45∶55。试验分为2阶段,每阶段20 d,其中预试期14 d,载体灌注期3 d,乳脂前体物灌注期3 d。在载体灌注期,MF组与CS组均接受载体灌注,分别命名为MFC_1组和CSC组;在乳脂前体物灌注期,MF组继续接受载体灌注(MFC_2组),CS组灌注乳脂前体物(CSF组)。测定产奶量、干物质采食量及乳成分。采集尾动脉和乳静脉血浆测定短链脂肪酸浓度和脂肪酸比例。结果表明:1)在灌注乳脂前体物前,CSC组产奶量、4%乳脂校正乳产量、乳脂产量、乳蛋白产量和产乳脂效率显著低于MFC_1组(P0.05),CSC组尾动脉血浆中短链脂肪酸浓度及短链脂肪酸/长链脂肪酸有低于MFC_1组的趋势(0.05≤P0.10)。2)灌注乳脂前体物后,CSF组产乳脂效率和乳蛋白率显著高于CSC组(P0.05),CSF组产奶量、4%乳脂校正乳产量、乳脂率和乳蛋白率尽管在数值上仍然低于MFC_2组,但组间差异不显著(P0.05),而CSF组产乳脂效率显著高于MFC_2组(P0.05)。3)灌注乳脂前体物后,CSF组尾动脉血浆中乙酸、丙酸以及短链脂肪酸浓度显著高于CSC组(P0.05),且乙酸、丁酸及短链脂肪酸浓度显著高于MFC_2组(P0.05),短链脂肪酸/长链脂肪酸有低于MFC_2组的趋势(0.05≤P0.10)。4)除CSF组丁酸动静脉差有高于CSC组的趋势(0.05≤P0.10)外,CSC组与MFC_1组、CSC组与CSF组、CSF组与MFC_2组乳腺对乙酸、丙酸、丁酸、短链脂肪酸的摄取量、摄取率和动静脉差均无显著差异(P0.05)。结果提示,以玉米秸秆为粗饲料奶牛灌注乳脂前体物可显著增加奶牛的产奶量、乳脂率和乳脂产量,并达到与以苜蓿等为粗饲料相似的水平,且具有较高的产乳脂效率,但对乳腺内短链脂肪酸的摄取量和摄取率无显著的影响。     

过瘤胃氨基酸高能复合物对奶牛产奶量及乳成分的影响

为研究不同过瘤胃氨基酸高能复合物对奶牛产奶量及乳成分的影响,试验选择胎次(3～5胎)、产奶量、产犊日期相近,体重(600±20)kg健康荷斯坦泌乳高峰期奶牛24头,随机分为4组,每组6头。1组为对照组,饲喂牛场常规日粮;2、3、4组为试验组,分别在常规日粮基础上添加过瘤胃氨基酸高能复合物Ⅰ、Ⅱ、Ⅲ500 g/(d.头)。正式期60 d。结果表明:奶牛日粮中添加过瘤胃氨基酸高能复合物后,均可明显提高奶牛产奶量、乳脂率、乳蛋白率及乳中总干物质含量。尤其是复合物Ⅲ,添加效果最为理想,平均日产奶量、乳脂率、乳蛋白率及总干物质含量分别比对照组提高21.19%(P<0.05)、21.31%(P<0.05)、9.72%(P<0.05)和10.34%(P<0.05),平均日校正乳产量提高35.70%(P<0.05)。     

不同饲粮模式对奶牛乳腺长链脂肪酸摄取的影响

本试验旨在研究不同饲粮模式对奶牛乳腺长链脂肪酸摄取的影响。选用健康且胎次、体重[(554±21)kg]、泌乳期[(120±4)d]和产奶量[(24.30±1.47)kg/d]相近的荷斯坦奶牛30头,采用随机区组设计,分为3组,每组10头。3组奶牛饲喂不同模式的饲粮,即以苜蓿、羊草和全株玉米青贮为粗饲料的饲粮(MF组)、营养水平约同MF组但以单一玉米秸秆为粗饲料的饲粮(CS1组)和粗饲料比例等同MF组但以单一玉米秸秆为粗饲料的饲粮(CS2组)。试验期90 d,分3期进行,每期30 d,在每期的最后2 d采集饲粮样、乳样和血样进行检测分析。结果表明:1)不同饲粮模式对奶牛的体重和干物质采食量均无显著影响(P0.05),但对奶牛的产奶量、乳脂率和日乳脂产量均有显著影响(P0.05)。MF组的产奶量和日乳脂产量均显著高于CS1组和CS2组(P0.05),而CS1组则显著高于CS2组(P0.05);MF组的乳脂率显著高于CS1组(P0.05)。2)不同饲粮模式对奶牛动、静脉血浆中C16∶0、C18∶0、C18∶2cis-6、C18∶1 cis-9和总长链脂肪酸的浓度均无显著影响(P0.05)。3)不同饲粮模式对奶牛的血流量造成了显著的影响(P0.05),呈现出CS1组MF组CS2组。不同饲粮模式影响了奶牛动脉对总长链脂肪酸的供给量,表现为MF组和CS1组显著大于CS2组(5 629.51、6 605.02 g/d vs.3 878.91 g/d)(P0.05)。4)不同饲粮模式影响了奶牛乳腺对总长链脂肪酸的摄取率,表现为MF组和CS2组显著高于CS1组(10.99%、10.84%vs.7.39%)(P0.05)。5)不同饲粮模式影响了奶牛乳腺对总长链脂肪酸的摄取量,表现为MF组(618.69 g/d)CS1组(487.87 g/d)CS2组(420.56 g/d),组间差异显著(P0.05)。本研究揭示了在低质粗饲料条件下,增加精料浓度并不能有效提高奶牛乳腺对长链脂肪酸的摄取。     

饱和脂肪酸对泌乳中期热应激奶牛血液CO2、离子浓度和离子平衡的影响

选择产后150~210 d的中国荷斯坦奶牛48头,根据产奶量、分娩时间和胎次分为对照组(SFA0)、1.5%(SFA1.5)和3.0%(SFA3)饱和脂肪酸试验组,来研究饱和脂肪酸对高温环境条件下泌乳中期奶牛血液CO₂、离子浓度和离子平衡的影响,旨在为合理利用饱和脂肪酸及其缓解奶牛热应激提供理论依据。结果表明,日粮添加饱和脂肪酸,奶牛血清中CO₂的平均含量对照组、1.5%饱和脂肪酸组和3%饱和脂肪酸组分别为20.92,21.82和21.31 mmol/L,1.5%饱和脂肪酸组显著高于对照组(P<0.05),日粮添加饱和脂肪酸对热应激奶牛血液K、Na、Cl、Ca离子和离子平衡无显著影响,日粮添加饱和脂肪酸显著提高产奶量、乳脂和干物质含量(P<0.05)。说明饱和脂肪酸具有改善热应激奶牛生产性能,缓解热应激奶牛血液CO₂下降的作用。     

调控饲料对奶牛产奶量和乳成分的影响

为研究调控饲料对奶牛产奶量和乳成分的影响,试验选择10头年龄、胎次、泌乳天数、产奶量相近的泌乳牛,按照配对试验设计分为2组,一组为对照组(饲喂基础日粮),另一组为试验组(饲喂添加调控饲料的基础日粮)。结果表明,试验组每头奶牛日均增奶量比对照组多1.366kg(P<0.05),乳蛋白、乳脂率、乳糖、乳中干物质含量相比差异不显著。通过试验前后对比可知,调控饲料显著提高了奶牛的产奶量。     

过瘤胃葡萄糖对泌乳奶牛产奶量及乳成分的影响

研究过瘤胃葡萄糖对泌乳奶牛产奶量及乳成分的影响。试验选用20头中国荷斯坦奶牛,按照胎次、体况及产奶量随机分成A、B两组(n=10)。A组牛为对照组,饲喂奶牛场原有基础日粮+2%脂肪粉;B组为试验组,饲喂基础+2%过瘤胃葡萄糖。结果表明,与A对照组相比较,添加过瘤胃葡萄糖后显著增加了奶牛产奶量(P<0.01),平均提高8.71kg/d;过瘤胃葡萄糖对乳脂率、乳蛋白率及乳中干物质含量均无明显变化,差异不显著(P>0.05)。在试验条件下,过瘤胃葡萄糖可显著提高泌乳奶牛产奶量。     

Effect of monensin and vitamin E on milk production and composition of lactating dairy cows

Feeding unsaturated oils to lactating dairy cows impair ruminal biohydrogenation (BH) of unsaturated fatty acids (USFA) and increase ruminal outflow of BH intermediates such as trans‐10, cis‐12 CLA that are considered to be potent inhibitors of milk fat synthesis. Supplementing lactating dairy cow’s rations containing plant origin oils with monensin and/or vitamin E may minimise the formation of trans‐10 isomers in the rumen, thereby preventing milk fat depression. Therefore, this study was conducted to evaluate the effects of monensin and vitamin E supplementation in the diets of lactating dairy cows containing whole cottonseed, as the main source of FA on feed intake, milk production and composition, milk fatty acid profile, efficiency of nitrogen (N) utilisation, efficiency of net energy (NE) utilisation and nutrients digestibilities. Four multiparous Holstein lactating dairy cows (86 ± 41 days in milk) were assigned to a balanced 4 × 4 Latin square design. Each experimental period lasted 21 days with a 14 days of treatment adaptation and a 7 days of data collection. The control diet was a total mixed ration (TMR) consisted of 430 g/kg forage and 570 g/kg of a concentrate mixture on dry matter (DM) basis. Cows were randomly assigned to one of the four dietary treatments including control diet (C), control diet supplemented with 150 mg of vitamin E/kg of DM (E), control diet supplemented with 24 mg of monensin/kg of DM (M) and control diet supplemented with 150 mg of vitamin E and 24 mg of monensin/kg of DM (EM). Dry matter intake (DMI) ranged from 19.1 to 19.5 kg/d and was similar among the dietary treatments. Dietary supplementation with vitamin E or monensin had no effect on milk production, milk fat, protein and lactose concentrations, efficiency of utilisation of nitrogen and net energy for lactation (NE_L). Digestibility of DM, organic matter (OM), crude protein (CP) and ether extract (EE) was not affected by the dietary treatments. Digestibility of neutral detergent fibre (NDF) was higher in cows fed with the M and EM diets in relation to those fed the C and E diets. The concentrations of C4:0, C6:0, C8:0, C10:0, C12:0, C14:0, C15:0, trans‐10‐16:1, cis‐9‐16:1, 17:0, 18:0, trans‐11‐18:1, cis‐9‐18:1, cis‐9, trans‐11 conjugated linoleic acid (CLA), trans‐10, cis‐12 CLA, and 18:3n‐3 FA in milk fat were not affected by the dietary supplementations. While feeding the M diet tended to decrease milk fat concentration of C16:0, the milk fat concentration of C18:2n‐6 FA tended to be increased. Dietary supplementation with vitamin E or monensin had no effect on milk fat concentrations of saturated, unsaturated, monounsaturated, polyunsaturated, short chain and long chain FA, but feeding the M diet numerically decreased milk fat concentration of medium chain fatty acids (MCFA). The results showed that vitamin E and/or monensin supplementations did not improve milk fat content and did not minimise the formation of trans‐10 FA isomers in the rumen when whole cottonseed was included in the diet as the main source of fatty acids.     

饲粮中添加黄花蒿乙醇提取物对奶牛产奶性能及乳脂中共轭亚油酸含量的影响

本文旨在研究饲粮中添加黄花蒿乙醇提取物对奶牛产奶性能及乳脂中共轭亚油酸(CLA)含量的影响。试验选取体重(600±29)kg、胎次2~3胎、泌乳期(158±3)d及泌乳量(22.8±1.8)kg/d的泌乳期荷斯坦奶牛15头,采用完全随机区组设计分为3组,每组5头,进行为期40 d的饲养试验,其中1~9 d为预试期,10~40 d为正试期。对照组饲喂基础饲粮,试验1组和试验2组分别在基础饲粮中添加96和160 g/(d·头)的黄花蒿乙醇提取物。结果表明:整个试验期间,2个试验组的产奶量(第24、31和40天)、乳脂率、乳脂产量、乳蛋白率、乳蛋白产量、非脂固形物含量以及乳脂中的饱和脂肪酸、单不饱和脂肪酸、多不饱和脂肪酸、短链脂肪酸、中链脂肪酸和长链脂肪酸含量与对照组相比均无显著差异(P0.05);2个试验组的乳脂中CLA含量分别比对照组提高了30.7%和38.6%,其中试验2组与对照组差异显著(P0.05)。由此得出,饲粮中添加适量的黄花蒿乙醇提取物对奶牛产奶性能没有明显影响,但可以提高其乳脂中CLA含量,从而优化乳脂中脂肪酸的比例。     

Reproductive Performance of Broiler Breeder Hens Fed n-3 Fatty Acid-rich Fish Oil

Abstract

The objective of the study was to investigate the effects of oil sources in the diet on milk yield, milk composition, and fatty acid (FA) profiles in mid-lactating dairy cows. Forty-eight Chinese Holstein dairy cows averaging 150 days in milk (DIM) at the start of the experiment (body weight = 596±19 kg; milk yield = 29.7±3.00 kg/d) were used in a completely randomized block design. The animals were assigned into four dietary treatments according to DIM and milk yield, and supplemented with no oil (control), 2% flaxseed oil (FSO), 2% soybean oil (SBO), and 2% oil from extruded soybeans (ESB). The experiment lasted nine weeks including the first week for adaptation. Milk yields, milk compositions (fat, protein, and lactose), and milk FA profiles were measured. Daily milk yield from cows fed with FSO, SBO, and ESB were higher than milk yield of the control cows (27.0, 27.0, and 26.5 vs. 25.4 kg/d). Milk fat percentage of the control cows was greater than those cows fed with oil-supplemented diets. However, increasing dietary fat content resulted with no change in fat-corrected milk yield. The FA profile of milk was changed by fat supplementation. Feeding oil reduced the proportion of both short-chain (C_8:0 to C_12:0) and medium-chain (C_14:0 to C_16:1) FAs, and increased the proportion of long-chain (≥C_18:0) FAs in milk fat. Cis-9, trans-11 conjugated linoleic acid (CLA) in milk fat was increased from 0.38% for the control to 0.79, 1.51, and 1.56% of fat for the cows supplemented with FSO, SBO, and ESB, respectively. Feeding oils rich in linoleic acid (SBO and ESB) was more effective in enhancing cis-9, trans-11 CLA in milk fat than oils containing linolenic acid (FSO). There was a linear relationship between transvaccenic acid and cis-9, trans-11 CLA content in milk. Overall, feeding the FSO, SBO, and ESB diets increased monounsaturated and polyunsaturated fatty acids and decreased the saturated fatty acid in milk fat.     

全棉籽对奶牛生产性能及血清生化指标的影响

本试验旨在研究饲粮中添加全棉籽对奶牛生产性能及血清生化指标影响.试验采用4×4拉丁方设计,选择8头泌乳早期的经产中国荷斯坦奶牛,随机分为4组,每组2个重复,每个重复1头牛.A组为对照组,饲喂基础饲粮;B、C和D组分别饲喂含5％、10％和15％全棉籽的试验饲粮.共进行4期试验,每期试验28 d,其中预试期7d,正试期21 d.结果表明:1)随着全棉籽比例的增加,奶牛产奶量有提高趋势,奶牛的乳脂率和4％标准乳产量显著提高(P＜0.01),但全棉籽对乳蛋白率、乳糖率和乳非脂固形物率无显著影响(P＞0.05).2)全棉籽对粗蛋白质、粗脂肪、酸性洗涤纤维的表观消化率无显著影响(P＞0.05),但含有全棉籽饲粮的中性洗涤纤维的表观消化率均高于对照组(P＜0.05),其中C组比对照组提高了8.4％(P＜0.05).3)全棉籽对奶牛血清中白蛋白、血糖含量无显著影响(P＞0.05),对血清胆固醇和尿素氮含量影响显著(P＜0.05).C组奶牛血清中胆固醇含量显著低于其他各组(P＜0.01).B、C组的血清尿素氮含量显著低于对照组和D组.4)随着饲粮中全棉籽比例的提高,血清和乳中游离棉酚含量也显著提高(P＜0.01),乳中游离棉酚含量在各试验组间差异不显著(P＞0.05).结果提示,全棉籽在奶牛泌乳早期饲粮中的最适添加量为10％.     

饲喂高淀粉饲粮时不同瘤胃降解淀粉水平对奶牛泌乳性能、营养物质表观消化率和氮平衡的影响

本试验旨在研究饲喂高淀粉饲粮时不同瘤胃降解淀粉水平对奶牛泌乳性能、营养物质表观消化率和氮平衡的影响。选用10头荷斯坦经产奶牛[平均泌乳天数为(214±38)d,平均乳产量为(26.2±2.4)kg/d,平均体重为(727±65)kg]作为试验动物,随机分成2组,每组5头。试验设计2种不同瘤胃降解淀粉水平的试验饲粮,分别为瘤胃降解淀粉水平为62.3%(占总淀粉的百分比)的低瘤胃降解淀粉水平饲粮(L-RDS)和瘤胃降解淀粉水平为72.1%(占总淀粉的百分比)的高瘤胃降解淀粉水平饲粮(H-RDS)。采用交叉试验设计,试验分为2期,过渡期7 d,每期试验21 d,其中适应期14 d,采样期7 d。结果显示:1)相比L-RDS组,H-RDS组有机物和淀粉的表观消化率显著升高(P0.05),中性洗涤纤维和酸性洗涤纤维的表观消化率显著降低(P0.05),干物质表观消化率有升高趋势(P=0.07),蛋白质表观消化率无显著差异(P0.05)。2)相比L-RDS组,H-RDS组尿素氮及它们占摄入氮比例有降低趋势(P=0.09),摄入氮、乳氮、粪氮、尿氮和沉积氮及它们占摄入氮比例无显著变化(P0.05),尿中总嘌呤衍生物排出量和微生物蛋白产量亦无显著变化(P0.05)。3)饲粮瘤胃降解淀粉水平对奶牛干物质采食量、乳产量和乳成分均无显著影响(P0.05)。综合以上结果可知,饲喂高淀粉饲粮时不同瘤胃降解淀粉水平影响饲粮营养物质的表观消化率,对泌乳性能和氮平衡无显著影响。