饲喂高精料日粮对泌乳期山羊泌乳性能及抗氧化能力的影响

为了研究长期饲喂高精料日粮对泌乳期山羊泌乳性能和乳腺组织抗氧化能力的影响,实验选用12只健康经产泌乳中期关中奶山羊,随机分为两组,分别饲喂精粗比为35∶65(低精料组, LC, n=6)和65∶35(高精料组, HC, n=6)的日粮。实验期共10周,实验期间采集羊奶与血液;实验结束后采用静脉注射的方法对山羊进行安乐死,随后采集乳腺组织并迅速置于液氮中速冻后保存于-70 ℃待测。结果显示,HC组山羊乳产量显著高于LC组(P<0.01),同时乳中乳糖,乳蛋白的比例随着泌乳时间的增加而显著升高。与LC组山羊比较,HC组山羊乳腺组织中SREBP1和GLUT1 mRNA表达显著下降(P<0.05);磷酸化AKT1蛋白表达呈下降趋势(P=0.08);除此之外,HC组山羊乳腺组织的总抗氧化能力T-AOC(P=0.06)和GSH酶活均呈下降趋势(P=0.08)。这些结果表明,长期饲喂高精料日粮可降低乳腺组织的抗氧化能力,同时可降低乳中乳脂率以及乳腺组织中SREBP-1和P-AKT的表达。     

不同高精料耐受时间对泌乳期山羊肝脏糖脂代谢的影响

为了研究饲喂高精料日粮对泌乳期山羊肝脏糖脂代谢的影响,试验选用16只健康经产泌乳中期关中奶山羊,随机分为3组,低精料组(LC, n=5)、长期高精料组(HL, n=7)和短期高精料组(HS, n=4)。实验结束后采集血液和肝脏组织。结果显示,与LC组相比,HL和HS组奶山羊血糖和肝糖原水平显著升高(P<0.05),血液中甘油三酯(TG)水平显著降低(P<0.05),胆固醇(Tch)含量没有显著变化(P>0.05);HS组山羊肝脏TG和Tch水平显著增加(P<0.05),HL组无显著变化 (P>0.05)。HL组肝脏中丙酮酸羧化酶(PC)和葡萄糖转运蛋白2(GLUT2)mRNA表达水平显著上调;HS组肝脏PC、固醇调节元件结合蛋白1(SREBP1)、硬脂酰辅酶A去饱和酶(SCD)、二酰基甘油酰基转移酶(DGAT)和3-羟基-3-甲基戊二酰辅酶A还原酶(HMGCR) mRNA表达水平显著升高(P<0.05),SREBP-2有升高的趋势(P=0.76),肉碱棕榈酰转移酶-1(CPT-1)和胆固醇7α-羟化酶(CYP7α1)mRNA表达显著下降(P<0.05);线粒体型磷酸烯醇式丙酮酸羧激酶(PCK2)蛋白表达水平显著升高(P<0.05)。以上结果表明,短期饲喂高精料日粮能增强肝脏糖异生能力,促进肝脏胆固醇和脂肪合成;而长期饲喂高精料日粮能增强肝脏糖异生作用,但对胆固醇和脂肪代谢相关基因的表达没有影响。     

高精料对泌乳奶山羊瘤胃上皮氧化应激和胆固醇代谢的影响

为了研究长期或短期饲喂高精料日粮对泌乳期奶山羊瘤胃上皮组织氧化应激和胆固醇代谢的影响,实验选用17只健康的经产泌乳中期关中奶山羊,随机分为3组:饲喂低精料组(对照组,LC,n=5);长期饲喂高精料组(HL, n=7),19周饲喂期;短期饲喂高精料组(HS,n=5),4周饲喂期。实验结束后采集瘤胃组织,用PBS反复清洗,于液氮中速冻后置于-80 ℃冰箱保存。结果显示,与对照组相比,HL和HS组山羊瘤胃上皮组织中细胞周期相关基因CDK2和CDK4 mRNA表达水平显著升高(P<0.05),且HS组p-ERK1/2蛋白表达显著升高(P<0.05),但GPR41和GPR43蛋白表达无显著变化(P>0.05);HL和HS组山羊瘤胃上皮组织促细胞凋亡基因Casepase9 mRNA表达显著升高(P<0.05),HS组抗凋亡Bcl-2/Bax mRNA表达比例呈下降趋势(0.050.05);HS组瘤胃上皮组织中胆固醇含量下降达显著水平(P<0.05),且HL组呈下降趋势(0.05+ ATPase mRNA表达显著升高(P<0.05),NHE2蛋白表达升高但未达显著差异水平(P>0.05)。与HL组相比,HS组山羊瘤胃上皮组织中总抗氧化能力T-AOC显著升高(P<0.05);且胆固醇含量显著下降(P<0.05)。以上结果说明,短期饲喂高精料日粮可加快泌乳期奶山羊瘤胃上皮组织的更新,提高组织总抗氧化能力;而长期饲喂高精料日粮未引起细胞增殖相关蛋白和总抗氧化能力的显著变化;饲喂高精料日粮可以加快瘤胃上皮组织对VFA的转运。此外,饲喂高精料日粮引起瘤胃上皮组织内胆固醇含量降低,胆固醇酰基转移酶基因表达的显著上调,提示其对瘤胃上皮组织更新的潜在影响。     

长期饲喂高精料日粮对泌乳期山羊血液生化参数及组织中糖代谢相关基因表达的影响

为了研究长期饲喂高精料日粮对泌乳期山羊血液生化指标和糖代谢的影响,选择8只安装永久性瘤胃瘘管的健康经产泌乳中期山羊,分别饲喂精粗比为40∶60 (low concentrate, LC,n=4) 和60∶40 (high concentrate, HC,n=4)的日粮。实验期共8周,实验期间采集瘤胃液,血液;实验结束时采集肝脏,肌肉,脂肪组织置于液氮速冻后于-70℃保存待测。结果显示,饲喂高精料日粮2周后山羊瘤胃液pH显著降低,采食后瘤胃液pH持续低于5.8超过3 h,8周后瘤胃液pH升高维持在6.0以上,但仍低于LC组山羊。与LC组山羊相比较,HC组山羊血液中葡萄糖、游离脂肪酸含量均升高(P<0.05,P=0.071),谷草转氨酶含量有上升的趋势(0.05相似文献   

Influence of pasture on fatty acid profile of goat milk

The effect of pasture on the fatty acid profile of milk was evaluated using 30 pluriparous goats, which were divided into two homogeneous groups (H and P) of 15 goats each after kidding. Group H (control) goats were housed in a stall and received alfalfa hay, while group P was led to pasture. The goats of both the groups received the same concentrate. Average milk yield did not differ statistically between the groups. The goats of the P group had significantly higher fat content in milk than those of group H (53.7 vs. 61.5 g/day, p < 0.01), while lactose content was significantly higher for group H (66.2 and 61.4 g/day, for groups H and P, respectively, p < 0.05). Among milk fatty acids, pasture significantly affected the percentages of C18:1 cis9, C18:1 trans11, octadecadienoic acid, mono-unsaturated fatty acid and polyunsaturated fatty acid. Pasture highly influenced the c9 t11 conjugated linoleic acid (CLA) (0.778 and 0.513 g/100 g of fat, for group P and H, respectively, p < 0.01), t10 c12 CLA (0.046 vs. 0.029 g/100 g of fat: p < 0.01, for group P and H, respectively, p < 0.01) and SigmaCLA (0.84 vs. 0.56 g/100 g of fat for group P and H, respectively, p < 0.01) concentrations of milk.     

利用乳汁体细胞研究共轭亚油酸钙对奶牛乳腺基因表达的作用

8头泌乳中期的奶牛被随机分为2组，分别是对照组（每头牛：基础日粮＋棕榈酸钙200g／d）和试验组（每头牛：基础日粮＋共轭亚油酸钙200g／d），试验期14d，检测了奶产量、乳成分，分析奶牛的血液变化，并采用荧光定量PCR对乳汁体细胞中脂蛋白脂酶（LPL）、乙酰辅酶A羧化酶（ACACA）的基因表达进行检测。结果显示，与对照组相比，试验组奶牛的乳产量、乳蛋白、乳糖和乳汁体细胞含量没有显著影响，但是显著降低了乳脂肪含量（P〈0．05），对照组和试验组奶牛乳脂肪含量分别为0．0326g／mL和0．0244g／mL。检测血液指标发现，共轭亚油酸钙显著升高了奶牛血液中高密度脂蛋白的含量（P〈0．05）。基因分析发现，试验组奶牛乳汁体细胞中LPL、ACA—CA的基因表达显著下调，表明共轭亚油酸钙抑制了奶牛乳腺细胞脂肪酸合成酶的基因表达。     

Fatty acid composition of muscle and adipose tissues of indigenous Caribbean goats under varying nutritional densities

The effects of a concentrate diet on growth, carcass fat, and fatty acid (FA) composition of muscle (supraspinatus), perirenal, and intermuscular adipose tissues of Creole goats (n = 32) were evaluated. Goats were fed a tropical green forage Digitaria decumbens ad libitum with no concentrate (G0) or 1 of 3 levels of concentrate: 140 (G100), 240 (G200), and 340 g?d(-1) (G300), respectively. Goats were slaughtered according to the standard procedure at the commercial BW (22 to 24 kg of BW). Goats fed the concentrate diets (G100, G200, and G300) had greater ADG (P < 0.001), cold carcass weights (P < 0.001), and omental (P < 0.01), perirenal (P < 0.01), and intermuscular (P < 0.01) adipose tissues weights. Dietary intake of C18:0, C18:1n-9, C18:2n-6 increased as concentrate supplementation increased (P < 0.001), whereas C18:3n-3 intake was not affected (P > 0.05). Increased concentrate supplementation did not affect (P > 0.05) the proportion of MUFA in all tissues and had very little effect on SFA in perirenal tissue, but increased the PUFA proportion in muscle (P < 0.05). The major effect of feeding increased concentrate was an increase in n-6 PUFA proportions in all tissues (P < 0.001) and, surprisingly, a decrease in n-3 PUFA (P < 0.001). Focusing on FA, which are supposed to have a beneficial or an adverse effect on human health, feeding increased concentrate did not increase the content of any cholesterol-increasing SFA in meat, but increased the n-6/n-3 ratio above 4 when more than 240 g of concentrate was fed per day.     

Effects of dietary n-6:n-3 fatty acid ratio on feed intake, digestibility, and fatty acid profiles of the ruminal contents, liver, and muscle of growing lambs

This study investigated the effect of modifying the n-6:n-3 fatty acid ratio (FAR) of diets using linseed, soybean, and cottonseed oils on apparent digestibility, ruminal fermentation characteristics, growth performance, key circulating hormones, and the fatty acid profile of ruminal digesta, liver, and fore-shank muscle of growing lambs fed a high concentrate diet. Forty individually housed Katadhin Dorper lambs (average of 20.0 kg of BW) were fed Bermudagrass hay in ad libitum amounts and concentrates at 3.7% of BW daily. The concentrate contained 68.9% corn, 23.8% soybean meal, 3.3% limestone, and 4.0% oil supplements (DM basis). The treatments consisted of dietary n-6:n-3 FAR of 2.3:1, 8.8:1, 12.8:1, and 15.6:1. After feeding for 35 d in metabolism crates, lambs were slaughtered 15 h after feeding, and samples of ruminal digesta, blood, liver, and foreshank tissue were collected. Increasing dietary n-6:n-3 FAR did not affect the intake of DM nor the apparent digestibility of DM, ether extract, NDF, or ADF, but did increase apparent digestibility of CP (linear, P < 0.05). Concentrations of ruminal butyrate increased linearly (P < 0.05) with increasing dietary n-6:n-3 FAR, whereas the valerate concentration decreased linearly (P < 0.001). Concentrations of plasma insulin and IGF-I were not affected by dietary n-6:n-3 FAR. Concentrations of C18:3n-3 increased linearly (P < 0.001), whereas that of C18:2n-6 decreased linearly (P < 0.001) in ruminal digesta with decreasing dietary n-6:n-3 FAR. Concentrations of transisomers of fatty acids in ruminal digesta did not change. Proportions of C18:0 in liver and foreshank muscle were unchanged by diet. The proportion of trans11 C18:1 and cis-9 trans11 CLA decreased (P < 0.05) in liver but increased (P < 0.05) in foreshank muscle as dietary n-6:n-3 FAR decreased. Proportions of all measured n-3 fatty acids were greater in liver when diets contained more C18:3n-3 from linseed oil. By decreasing the dietary n-6:n-3 FAR, the proportions of n-6 fatty acids in foreshank muscle decreased dramatically; specifically, C18:2n-6 decreased linearly (P < 0.001) from 28.0 to 16.5% and C20:4n-6 decreased linearly (P < 0.001) from 14.7 to 8.6%. Although feeding a diet that contained more n-3 fatty acids increased the n-3 fatty acid concentration of muscle, the ratio of PUFA to SFA was decreased.     

复合缓冲剂对奶山羊乳成分、血浆生化指标及激素含量的影响

本试验旨在研究长期饲喂高精料饲粮下添加复合缓冲剂(碳酸氢钠20 g/d、氧化镁12 g/d、丁酸钠20 g/d)对奶山羊乳成分、血浆生化指标及激素含量的影响。选择8头安装门静脉及肝静脉瘘管处于泌乳中期的奶山羊随机分为2组,分别饲喂基础饲粮(高精料饲粮组,HG组)和基础饲粮+复合缓冲剂(高精料饲粮+复合缓冲剂组,BG组)。预试期为7 d,正试期为143 d。结果显示:与HG组相比,复合缓冲剂显著升高采食后010 h瘤胃液p H平均值(P0.05);复合缓冲剂显著降低肝静脉血浆中非酯化脂肪酸的含量(P0.05),对门静脉和肝静脉血浆中葡萄糖、β-羟丁酸含量无显著影响(P0.05),对肝脏组织中甘油三酯和总蛋白含量无显著影响(P0.05);复合缓冲剂显著降低门静脉血浆中胰岛素和胰高血糖素的含量(P0.05),对门静脉和肝静脉血浆中胰岛素样生长因子1和生长激素的含量无显著影响(P0.05);复合缓冲剂显著或极显著升高产奶量、乳脂率、乳蛋白率、乳非脂固形物率(P0.05或P0.01)。综合得出,在长期高精料饲粮饲喂条件下,由碳酸氢钠、氧化镁、丁酸钠组成的复合缓冲剂能通过影响奶山羊血浆生化指标及激素含量,影响体机营养物质代谢,最终有效提高产乳量与改善乳品质。     

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。     

Utilization of glucose and long-chain fatty acids in lactating dairy cows fed a fat-enriched diet

The fate of carbon from long-chain fatty acids and glucose in dairy cows which were fed with protected fat was studied using stable isotope technique. The experiment was carried out on two groups of dairy cows (n=16 in each group) during the first 15 weeks of the lactation period. The cows were fed isoenergetic and isoproteinogenous diets based on corn silage. About 1.8 kg of tapioca starch in the diet of the starch group was substituted by about 0.7 kg of rumen protected fat (Ca salts of palm oil and soybean oil) in the diet of the fat group. The carbon atoms of dietary fat were naturally depleted in 13C as compared to carbon atoms of starch. Daily milk performance and lactose output were significantly (P < 0.05) higher among the cows fed with fat diet. In comparison to the starch group, the enrichment of milk fat with 13C was significantly lower, while that of breath CO2 was significantly higher in the fat group (P < 0.05). This means the fatty acids were incorporated into milk fat in preference to metabolic oxidation. Further studies showed that blood glucose is oxidized to a lower extent and is used for the synthesis of lactose to a higher proportion if the cows were fed with the fat diet. The glucose entry rate into the body glucose pool was not different between the diets. In conclusion, the dietary fatty acids perform a glucose sparing effect and improve the glucose supply for the mammary gland.     

不同饲粮对泌乳奶牛乳脂前体物的摄取和利用的影响

本试验旨在研究不同饲粮条件下泌乳奶牛对乳脂前体物的摄取和利用规律。选取体重为(617±21)kg、泌乳天数为(120±20)d的9头健康泌乳荷斯坦奶牛为试验动物,采用3重复3×3拉丁方设计,随机分为3组,其中2组饲粮的精饲料配方不同,粗饲料相同均为秸秆,精粗比均为6∶4(分别称之为CSA和CSB组),余下1组以羊草、苜蓿干草、全株玉米青贮为混合粗饲料,精粗比为4∶6(MF组),每组3头;试验期84 d,分为3期,每期28 d,包括21 d的预试期及7 d的正试期。结果表明:1)各组产奶量及乳成分差异不显著(P0.05),但MF组的泌乳效率显著高于CSA和CSB组(P0.05)。2)各组饲粮C16∶0和C18∶0摄取量差异不显著(P0.05);MF组饲粮C18∶1 c9摄取量显著低于CSA和CSB组(P0.05)。3)MF组动脉血浆中长链脂肪酸和总脂肪酸含量均高于CSA和CSB组,特别是C18∶3 n3含量显著高于CSA和CSB组(P0.05)。4)MF和CSB组乳腺C18∶3 n3摄取量(日平均值)显著高于CSA组(P0.05);各组乳腺对其他长链脂肪酸的摄取量差异不显著(P0.05)。5)最终体现在乳中,表现为MF组的C18∶3 n3产量较CSA和CSB组有升高的趋势(0.05≤P0.10),而原本乳腺摄取量无显著差异的C18∶2 n6(P0.05),在乳中产量显著低于CSA和CSB组(P0.05)。由此可见,相同粗饲料、不同精饲料饲粮对泌乳奶牛生产性能无显著影响,而优质的粗饲料即使在精饲料比例降低的前提下,对乳中脂肪酸的组成及产量仍可以产生影响,使其更倾向于有利人体健康。     

Influence of percentage of concentrate in combination with rolled canola seeds on performance, rumen fermentation and milk fatty acid composition in dairy goats

The effect of rolled canola seeds (RCS, 0% or 20% of the dry matter (DM) of the concentrate) combined with percentage of concentrate (45% (L) vs. 65% (H) of the diet DM) on rumen fermentation characteristics, production parameters and fatty acid (FA) profile of milk fat was studied in 20 entire goats and 12 goats fitted with ruminal and duodenal cannula. Goats were fed TMR ad libitum for 15 weeks with the final 12 weeks as the test period. Individual milk samples were taken in weeks 5 and 11 to determine the FA profile of milk fat. Feeding the H diets increased NE_L intake, raw milk yield and yield of fat, protein and lactose. Feeding RCS increased fat corrected milk, milk fat content and fat yield. Combination of RCS and high percentage of concentrate increased fat corrected milk and fat yield. Milk protein content was not affected by dietary factors. Feeding the H diets increased the proportion of short-chain FA (C4:0–C8:0), each isomer of trans-C18:1 and c9,t11-C18:2 in milk at the expense of medium-chain FA with 11 to 17 C units. Feeding RCS decreased the proportion of medium-chain FA with 10 to 17 C units in milk and it increased that of C18:0, all isomers of trans-C18:1, c9-C18:1 and c9,t11-C18:2. Goats fed the H diets, and those fed the RCS had lower c9-C18:1/C18:0 and c9,t11-C18:2/t11-C18:1 ratios. Combination of RCS and high percentage of concentrate produced the highest proportion of all isomers of trans-C18:1 and c9,t11-C18:2 in milk, with the highest variability among the four diets for these FA. This was possibly related to between-goats differences in ruminal fermentation and to individual difference in desaturase activity in the mammary gland. It is concluded that feeding a high-concentrate diet combined with rolled canola seeds had a synergistic effect on the milk production and fat yield without alteration in milk protein content in dairy goats. This combination also resulted in changes in FA profile that may differently affect the nutritional value of goat milk for human health.     

Effects of Energy Level on Physical and Chemical Indicators,Composition and Content of Amino Acids and Fatty Acids in Muscle of House-fed Yaks

This experiment was conducted to investigate the effects of energy level on the physical and chemical indicators,the composition and content of amino acids and fatty acids in muscle of house-fed yaks.A complete randomized design was adopted in this study,and sixty healthy and 3-year-old Maiwa yaks with an average body weight of (192.66±3.64)kg were randomly divided into 3 groups with 20 replicates per group and 1 yak per replicate.Diets for all groups were of the same crude protein content (14.81%) and different net energy levels for gain (NE_g) with 4.17(LE),4.48(ME) and 4.79 MJ/kg (HE),respectively for 97 days (7-day pretrial period,and 90-day feeding trial).The results showed as follows:The level of energy had no effect on the value of pH,cooking yield,drip loss,moisture,crude protein (CP),crude fat (EE),calcium (Ca) and phosphorus (P) (P>0.05).Except for the content of proline and histidine in muscle of group ME were significantly higher than the other groups (P<0.05),the content of total amino acids and other kinds of amino acids had no significant difference (P>0.05).The content of monounsaturated fatty acids,polyunsaturated fatty acids and total unsaturated fatty acids in ME group were significantly higher than the LE and HE groups,and the content of total saturated fatty acids in HE group higher than the LE and ME groups.For all kinds of fatty acid,the content of C15:1 n-3,C16:1 n-2 and C18:1 n-8 three monounsaturated fatty acids in ME group significantly increased than the other two groups (P<0.05);And the content of C17:0 in HE group had a significat rise trend.In conclusion,we recommend 4.48 MJ/kg (DM basis) as a diet appropriate NE_g level for the barn feeding of fattening yak under this experimental condition,appropriate NE_g level of diet could improve the fatty acids content in muscle of the yaks.     

能量水平对舍饲育肥牦牛肌肉理化指标和氨基酸、脂肪酸组成及含量的影响

本研究旨在探讨能量水平对舍饲育肥牦牛肌肉理化指标和氨基酸、脂肪酸组成及含量的影响。选取60头体况良好、平均体重为（192.66±3.64）kg的3周岁左右的舍饲育肥麦洼公牦牛,采用完全随机试验设计,每组20个重复,每个重复1头牦牛。饲喂粗蛋白质（CP）水平为14.81%,增重净能（net energy for gain,NE_g）分别为4.17（低能量组,LE）、4.48（中能量组,ME）、4.79 MJ/kg（高能量组,HE）的3种日粮。试验期共97 d,其中预试期7 d,正试期90 d。结果显示,各处理组牦牛肌肉的pH、熟肉率和滴水损失3个理化指标均无显著差异（P>0.05）;各处理组牦牛肌肉常规营养成分的水分、粗蛋白质、粗脂肪、钙和磷含量无显著差异（P>0.05）;除ME组牦牛肌肉中的脯氨酸（Pro）和组氨酸（His）含量显著高于其余两组外（P<0.05）,总氨基酸和其他种类的氨基酸含量差异不显著（P>0.05）;ME组单不饱和脂肪酸、多不饱和脂肪酸及总不饱和脂肪酸相对含量显著高于LE、HE组（P<0.05）,HE组总饱和脂肪酸显著高于LE、ME组（P<0.05）。对于各种类脂肪酸,ME组的C15：1 n-3、C16：1 n-2和C18：1 n-8 3种单不饱和脂肪酸含量均显著大于其余两组（P<0.05）;而HE组的C17：0含量则有显著高于其余两组的趋势。在本试验条件下,舍饲育肥牦牛日粮中适宜的NE_g水平为4.48 MJ/kg（日粮DM）,适宜日粮NE_g水平能提高牦牛肌肉中脂肪酸的含量。     

Impact of bovine somatotropin administration beginning at day 70 of lactation on serum metabolites, milk constituents, and production in cows previously exposed to exogenous somatotropin.

Metabolic and production responses are reported for 72 cows treated with bovine somatotropin (BST) for 30 days starting at day 70 of lactation. Of these 72 cows, 48 had been exposed in the preceding lactation to long-term treatment with BST at 3 dosages and 24 (controls) had not been given BST. Approximately half of the cows in each group were parity-2 cows, the rest were older. Comparisons between groups were made separately for parity-2, and older cows. Analyses, using pretreatment values of each variable as a covariate, indicated that older cows, but not parity-2 cows, significantly (P less than 0.05) increased milk production during treatment. Parity-2 cows, however, had a significantly higher milk fat percentage than controls following treatment. Cows treated with 51.6 or 86 mg BST/d in both parity groups had significantly higher serum-free fatty acids than controls. Estimated net energy balances were significantly lower for older treated cows, but did not significantly differ from controls for parity-2 treated cows. Older cows in the 86 mg of BST/d group tended to have higher concentrations of blood glucose than did older control-group cows. Treatment with BST did not significantly increase serum ketone concentrations in any group of animals, and none of the cows developed clinical ketosis during this period. Estimated net energy balance (ENEB) during treatment was a significant (P less than 0.05) covariate for free fatty acid concentrations in older cows and for milk fat percentage in parity-2 cows. Covariate adjusted analyses, using ENEB during treatment as a covariate, indicated that lipolytic stimuli already acting may be enhanced by treatment with BST, but a negative energy balance was not a necessary precondition for free fatty acid concentrations to increase following somatotropin treatment. Similarly, milk fat percentages for parity-2 treated cows were significantly (P less than 0.05) higher during treatment than controls when ENEB during treatment was used as a covariate. Increased milk fat concentrations in parity-2 treated cows were not associated with significant increases in the ratio of C18:C4-10 milk fatty acids, indicating that increased milk fat resulted from either an increase in incorporation of C18 fatty acids into milk fat coupled with an increase in de novo mammary synthesis of C4-10 milk fatty acids or an increase in C12-16 fatty acids that may arise either from increased tissue mobilization, from diet, or from de novo mammary synthesis.     

Effects of supplementing with calcium salts of palm oil fatty acids or hydrogenated tallow on ewe milk production and twin lamb growth

Two experiments were conducted with Polypay ewes nursing twin lambs to evaluate the effects of supplementing fat (calcium salts of palm oil fatty acids or hydrogenated tallow) on ewe lactation. In Exp. 1, ewes were fed a 52% concentrate:48% hay-based diet (as-fed basis) consisting of alfalfa hay (n = 4), endophyte-free fescue hay (n = 4), or fescue hay with 3.7% fatty acids (n = 4) from d 4 to 56 of lactation. In Exp. 2, ewes were fed similar diets that had endophyte-free fescue hay (n = 6), fescue hay with 3.7% fatty acids (n = 5), or fescue hay with 3.1% tallow (n = 6) from d 14 before lambing until d 57 of lactation. Diet formulations with supplemental fat were more nutrient dense, and treatments were fed to meet ewe nutrient requirements; this caused diets with added fat to be offered at 10 and 17% lower rates than unsupplemented diets in Exp. 1 and 2, respectively. Lambs were maintained to consume only ewe milk. Ewe milk production and composition were determined using a portable milking machine following a 3-h separation from lambs. In Exp. 1, milk fat content was increased (P < 0.01) when ewes consumed fescue hay with fatty acids vs. the fescue hay diet (11.4 vs. 8.3%). Ewes fed fescue hay with fatty acids lost the most (P < 0.05) weight over lactation (-8.6 kg) compared with ewes fed the alfalfa hay (-2.4 kg) and fescue hay (-3.8 kg) diets. Other milk measures, lamb gain, and production efficiencies were not changed. In Exp. 2, ewes supplemented with fatty acids produced more (P < 0.05) milk fat than those fed tallow (290 vs. 210 g/d). The proportion of synthesized milk fat 14:0 was decreased (P < 0.01), but the percentage of incorporated 16:0 increased (P < 0.05) when fatty acids were fed. Dietary fat digestibility by ewes was increased (P < 0.01) by fatty acid supplementation but decreased (P < 0.01) when tallow was added. Although ewe weight measures were not changed in Exp. 2, twin lamb gain per ewe organic matter intake was most efficient (P < 0.05) when ewes were supplemented with fatty acids. Results suggest that feeding hydrogenated tallow decreased nutrient availability for ewe milk fat production. A complete diet based on endophyte-free fescue hay can replace a traditional alfalfa hay diet, whereas supplementing with the calcium salts of palm oil fatty acids may be more feasible when energy is limiting during ewe lactation.     

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...     

Quality and fatty acid profile of the milk of indigenous goats subjected to different local diets in Tunisian arid lands

The study tested the hypothesis that certain pastoral forages and olive by‐products, available in arid areas, may positively influence fatty acid composition and physicochemical properties of goat's milk. Thirty indigenous goats (body weight = 25.2 kg; age = 4.1 years) were allocated to three groups. During 60 days, the goats received ad libitum either dried olive leaves + Stipa tenacissima (group OL), khortane grass hay (group Ko) or oat hay (control diet, group OH). Milk samples were collected and analysed for total solids, fat, protein, lactose and ash content and fatty acid profile. Average milk yield did not statistically differ among groups. Milk total solids from OL group were higher in comparison with Ko and C groups (15.3, 14.7 and 14.5%, respectively; p < 0.05). Fat content was also higher for the OL group as compared to the other groups (5.44 vs. 5.01 and 4.66%, respectively, for Ko and OH). No significant differences were observed for the milk content of lactose, protein and ash. The percentage of saturated fatty acids of total milk fat was higher in OL and Ko groups compared to the C group (p < 0.001); the milk whereof was characterized by the highest percentage of monounsaturated (p < 0.01) and total unsaturated fatty acids. Milk fat of Ko and C groups showed significantly higher proportions of rumenic (CLA cis‐9 trans‐11) and vaccenic acids (C18:1 trans‐11) compared to OL milk. The feeding system based on Stipa tenacissima and dried olive leaves resulted in the milk lowest proportion of trans‐fatty acids and the highest proportion of polyunsaturated ω3‐fatty acids (p < 0.05).