几种酵母菌添加剂对奶牛产奶量及乳成分的影响

将54头高产中国荷斯坦奶牛随机分为6组，1组基础对照组，5组（A，B，C，D，E）试验组，试验组在基础日粮的水平上添加15g不同型号的酵母菌制剂，预试期2周，正试期为6周。结果表明：不同型号的酵母菌对奶牛产奶量和奶成分有不同程度的影响，其中C和E组奶牛的产奶量分别比对照组有所增加，B和D组的产奶量与对照组相比增加显著（P〈0．05），A组则有所下降；不同型号的酵母菌制剂对牛乳成分也有不同程度的影响，试验组B，D，E组乳脂日产量比对照组有增加，并且差异显著（P〈0．05）；E组乳脂率增加，差异显著；蛋白质日产量除A组无显著性差异（P〉0．05），B，C，D，E组相比对照组都有所增加，其中C和E组相比对照组，差异显著（P〈0．05）；试验组的乳糖、非脂固形物产量与对照组没有显著差异（P〉0．05）；各试验组的所生产牛奶的比重、冰点、酸度与对照组无显著差异，但试验组的酸度除D组外均比对照组有所提高，乳中体细胞数均比对照组低，其中酵母菌C和D能显著减少乳中体细胞数（P〈0．05）。     

果寡糖对泌乳早期奶牛瘤胃发酵及生产性能的影响

为研究果寡糖对泌乳早期奶牛瘤胃发酵及生产性能的影响,采用两阶段交叉设计,将4头泌乳天数20 d,产奶量30 kg/d,体质量(550±35)kg健康经产(二胎)中国荷斯坦泌乳奶牛随机分为两组,分别为试验组、对照组,试验组添加果寡糖。结果表明:日粮中添加60 g/(d·头)的果寡糖,对奶牛瘤胃中总挥发性脂肪酸、氨态氮影响极显著(P0.01),对丁酸影响差异显著(P0.05),但是对于乙酸、丙酸来说影响不显著(P0.05),与对照组相比,试验组的总挥发性脂肪酸量提高35.9%,氨态氮降低15.5%,丁酸提高33%。对奶牛生产性能进行分析,乳脂率影响差异显著(P0.05),体细胞影响差异极显著(P0.01),与对照组相比,试验组乳脂率提高4.7%,体细胞降低68.5%,而产奶量、乳蛋白、乳中尿素氮浓度均无显著影响(P0.05)。综上所述,日粮中添加果寡糖能够改变瘤胃发酵模式,提高奶牛的乳脂率。     

精料和饱和脂肪酸对奶牛生产性能和乳中脂肪酸组成的影响

为研究高精料和饱和脂肪酸对泌乳早期奶牛生产性能和乳中脂肪酸组成的影响。选择产后55 d左右的泌乳高峰期奶牛30头,根据随机区组设计原则,按照产奶量、胎次和泌乳天数将奶牛分为对照组(C)、高精料组(HC)和饱和脂肪酸组(FA),分别饲喂以干物质为基础含精料40%,60%和40%添加3%饱和脂肪酸的等蛋白日粮。结果 HC组产奶量(26.53±3.72)kg/d和FA组产奶量(26.98±3.36)kg/d显著高于C组(24.43±2.63)kg/d。FA组乳脂含量显著高于HC组(P≤0.05),HC组有低于C组的趋势(P=0.15)。FA组短链脂肪酸的含量显著低于C组(P≤0.05),HC组与C组差异不显著;HC组长链脂肪酸的含量显著低于FA组(P≤0.05),与C组差异不显著。HC组饱和脂肪酸含量显著高于FA组(P≤0.05)、FA组单不饱和脂肪酸含量显著高于C组和HC组(P≤0.05)、HC组多不饱和脂肪酸高于C组(P≤0.05)、各组间共轭亚油酸(10c12t CLA)含量差异不显著。结论为饲喂高精料日粮能够提高产奶量、降低乳脂率、增加乳脂中中链饱和脂肪酸和多不饱和脂肪酸含量。日粮添加饱和脂肪酸能够提高产奶量、增加乳脂率、增加单不饱和脂肪酸含量。     

乳酸菌制剂对奶牛泌乳量及乳成分的影响

选择27头经产,产犊30～45d,产奶量相近,胎次相近,体重相近,健康无病的高产奶牛。随机分为3组,1组为基础对照组,2组（A组和B组）为试验组,试验组在基础日粮的水平上添加10g不同型号的乳酸菌制剂,预试期2周,正试期为6周。结果表明,两种乳酸菌对奶牛产奶量和奶成分有不同程度的影响,其中A组奶牛的产奶量比对照组有所增加,且差异显著（P〈0．05）,B组则有所下降;不同型号的乳酸菌制剂对牛乳成分也有不同程度的影响。A组奶牛除乳糖率与对照组相比有所降低外,其他乳成分（乳脂率、蛋白率和非脂固形物）相比对照组均有显著增长（P〈0．05）;B组奶牛其乳脂率呈上升趋势,日蛋白产量及日乳糖产量较对照组有所下降,对其他乳成分无显著影响。乳酸菌A能显著减少乳体细胞数（p〈0.05）。两种乳酸菌所生产牛奶的比重、冰点、酸度与对照组无显著差异。     

油料籽实对奶牛生产性能及乳脂共轭亚油酸的影响

研究日粮中添加几种油料籽实对中国荷斯坦奶牛生产性能及乳脂脂肪酸组成的影响.选用48头高产中国荷斯坦奶牛,采用完全随机区组设计(对照组、大豆组、胡麻籽组、葵花籽组、花生组和棉籽组),试验组用7.5%不同油料籽实替换基础日粮中的部分豆粕.试验期6周,预试期2周,正式试验期4周.与对照组相比,各试验组奶牛的平均日采食量、产奶量、乳蛋白、乳糖及非脂固形物无显著差异,而乳脂率及日乳脂产量降低.其中,胡麻籽组降低最多,乳脂率和乳脂产量较对照组下降了0.34%和0.18 kg/d.大豆组的C18:1、tllC18:1及C18:2显著高于对照组和其它试验组,胡麻籽组的C18:3含量最高.各试验组CLA含量高于对照组,且差异极显著(P＜0.01).大豆组CLA含量最高,比对照组提高了60.38%.     

不同油料籽实对奶牛血液生化指标及其脂肪酸的影响

研究日粮中添加含有不同不饱和脂肪酸的油料籽实对中国荷斯坦奶牛血液生化指标及其脂肪酸组成的影响.试验组用10%不同油料籽实替换基础日粮中的部分豆粕,结果表明:与对照组相比,花生组(高油酸)和大豆组(高亚油酸)奶牛血液的胆固醇增加显著(P<0.05),而血糖、甘油三酯、非酯化脂肪酸和胰岛素的含量无显著差异(P>0.05).添加油料籽实增加了奶牛血浆长链不饱和脂肪酸的含量,其中大豆组(高亚油酸)的t11C18:1、C18:2和亚麻组(高亚麻酸)t11C18:1、C18:3的含量显著高于对照组(P<0.05),但并不影响血液中共轭亚油酸(CLA)的含量(P>0.05).说明添加油料籽实改变奶牛血液中部分生化指标,同时也会影响血液中部分脂肪酸成分的变化.     

日粮添加葵花籽油与豆油对奶牛生产性能及牛奶中共轭亚油酸含量的影响

研究通过日粮添加葵花籽油及葵花籽油与豆油混合油对牛奶中共轭亚油酸(CLA)含量及奶牛生产性能的影响。结果表明:在奶牛精料中添加葵花籽油及葵花籽油与豆油混合油,奶牛的采食量下降,产奶量上升。牛奶中CLA含量提高(P0.05),分别达到21.36与16.92 mg/(g乳脂);牛奶中乳脂率与乳蛋白含量下降显著,干物质含量略有下降(P0.05),对密度、pH值及乳糖的含量没有影响;乳脂中中短链脂肪酸含量下降,长链脂肪酸中的不饱和脂肪酸增加,而硬脂酸含量下降。     

玉米粉碎粒度对产后奶牛瘤胃发酵及生产性能的影响

旨在研究玉米粉碎粒度对泌乳早期奶牛瘤胃发酵、产奶量及乳成分的影响。试验选择4头泌乳天数为14 d,日产奶量25 kg左右,体重550 kg左右的经产(二胎)中国荷斯坦泌乳奶牛,随机分为两组,对照组奶牛日粮添加10%的破碎玉米,将对该比例破碎玉米由细粉碎玉米代替,作为试验组。试验采用2×2交叉试验设计,每期21 d。结果表明:试验组奶牛瘤胃液pH值显著低于对照组(P0.05);与对照组相比,试验组奶牛瘤胃液乙酸、丙酸与对照组相比有所增加,乙丙比例降低,丁酸具有增高的趋势,与对照组相比提高了17.77%,但差异均不显著(P0.05)。试验组奶牛瘤胃液微生物蛋白与对照组比较有增加的趋势,合成效率与对照组比较无显著性差异(P0.05);试验组奶牛瘤胃液氨态氮的含量显著低于对照组(P0.05)。试验组奶牛产奶量高于对照组,乳脂率与对照组相比有所降低,但差异均不显著(P0.05);随着玉米粉碎粒度的降低,奶牛乳中乳蛋白率有增高趋势,与对照组相比提高了7%;试验组奶牛乳中尿素氮显著低于对照组(P0.05)。说明在本试验条件下,细粉碎玉米替代日粮中部分破碎玉米,可以提高奶牛瘤胃的发酵功能,使奶牛乳中乳蛋白率有增高趋势。     

两种杂交水牛乳脂肪酸组成的对比

对摩拉×本地、尼里-拉菲×本地两种杂交水牛乳的乳脂肪酸组成进行测定,以分析二者脂肪酸组成的差异。结果表明,摩拉×本地水牛乳脂中,短链和中链的脂肪酸、丁酸(C_(4∶0))、十四酸(C_(14∶0))和9-十六烯酸(C_(16∶1,c9))显著低于尼里-拉菲×本地水牛乳(p0.05),而长链的脂肪酸、十八酸(C_(18∶0))、二十酸(C_(20∶0))和二十二酸(C_(22∶0))含量显著高于尼里-拉菲×本地水牛乳(p0.05),其中总长链脂肪酸(LCFA)显著高于尼里-拉菲×本地水牛乳(p0.05)。两个品种乳脂中饱和脂肪酸(SFA)、单不饱和脂肪酸(MUFA)和多不饱和脂肪(PUFA)含量无显著差异(p0.05)。     

麦蓝菜对奶牛产奶量及乳成分的影响

选用15头体质量、胎次、产奶量均相近中国荷斯坦奶牛,随机分为A、B、C三组(n=5)∶A组(对照组)饲喂基础日粮;B组(试验组1)饲喂基础日粮+50 g麦蓝菜种子;C组(试验组2)饲喂基础日粮+150 g麦蓝菜植株.试验周期24 d,每天测定各组奶牛产奶量及乳成分,研究麦蓝菜对奶牛产奶量及乳成分的影响.结果表明:B组较A组产奶量提高了15.56％ (P＜0.01),牛奶乳蛋白和干物质分别提高了11.9％和5.1％(P＜0.01),乳脂率提高了9.4％(P＜0.05),A、B两组间乳糖含量差异不显著;C组较A组产奶量提高了3.48％(P＜0.01),牛奶乳蛋白和干物质体分别提高了6.3％和4.9％(P＜0.01),乳脂率和乳糖分别提高了9.1％和6.6％(P＜0.05).研究表明,基础日粮中添加麦蓝菜植株和种子均可以显著提高奶牛产奶量和乳品质.     

Variation in fatty acid contents of milk and milk fat within and across breeds

The aim of this research was to study the potential for selection of cows with a higher nutritional quality of milk fat by studying the differences in fatty acid profiles within and across the following breeds: Dual Purpose Belgian Blue, Holstein-Friesian, Jersey, Montbeliarde, and non-Holstein Meuse-Rhine-Yssel type Red and White. Six hundred milk samples from 275 animals were taken from 7 herds. Several types of fatty acids in milk and milk fat were quantified using mid-infrared spectrometry and previously obtained calibration equations. Statistical analyses were made using a mixed linear model with a random animal effect. The variance components were estimated by using REML. Results showed breed differences for the fatty acid profile. The repeatability estimate obtained in the present study may suggest the existence of moderate additive genetic variance for the fatty acid profile within each breed. Results also indicated variation for each analyzed milk component in the whole cow population studied. Genetic improvement of the nutritional quality of milk fat based on fatty acid profiles might be possible, and further research and development are warranted.     

Technical note: Estimation of milk fatty acid yield from milk fat data

Most publications reporting milk fatty acid (FA) yields estimate these yields from milk fat yields and a coefficient estimating the proportion of FA in milk fat. The most widely used coefficient is, in fact, the proportion of fatty acyl radicals (i.e., FA from which the OH group has been removed) in milk triglycerides, equivalent to a mean proportion of 88% FA in milk fat. From a metabolic point of view, because the digestive flows and mammary FA uptake consist of nonesterified FA, it is more logical to estimate the FA proportion rather than the fatty acyl proportion in milk fat. From 588 milk FA profiles, we estimated a mean proportion of 94.4% FA in milk triglycerides. Moreover, when the other milk lipid classes (phospholipids, diglycerides, etc.) were taken into account, the proportion of FA in milk total lipids was estimated at 93.3%, almost independently of the milk FA profile. The use of this coefficient to estimate the secretion of milk FA on the basis of milk fat yield data is more physiologically relevant for milk FA secretion studies.     

Influence of pasture and concentrates in the diet of grazing dairy cows on the fatty acid composition of milk

In five short-term experiments conducted in Victoria in 1997 and 1998, grazing dairy cows were given either pasture alone or pasture supplemented with high-energy concentrates, and the fatty acid profiles of milk fat were measured. We established the effects of these feeds on some aspects of milk fat of importance for human nutrition, but we specifically focused on the hypothesis that conjugated linoleic acid (CLA) concentrations in milk fat increase as pasture intake increases, and decrease as more concentrates are fed. In agreement with previous research, feeding fresh pasture alone resulted in high concentrations (1.0-1.8 g/100 g milk fat) of CLA. When the effect of level of pasture consumption on CLA content was examined, a significant positive relationship (r2 = 0.35; P < 0.05) was obtained. When cereal grain concentrates were used to supplement pasture intake, the CLA content of milk fat generally declined (P < 0.05), except where the amount of concentrates given led to a marked reduction in total milk fat concentration. The use of cereal grain concentrates also generally resulted in significant (P < 0.05) increases in medium-chain saturated fatty acids, but always reduced the contribution of butyric acid to milk fat, from 4.5 to 3.9 g/100 g milk fat, on average.     

Effects of week of lactation and genetic selection for milk yield on milk fatty acid composition in Holstein cows

Control (CL) and select line (SL) dairy cows (n = 22) managed identically but differing in milk yield (>4100 kg/305 d) were used to determine differences in milk fatty acid profile as lactation progressed. Milk yield was recorded daily and milk samples were collected during wk 1, 4, 8, 12, and 16 postpartum for milk composition analysis. Milk samples from wk 1, 8, and 16 were also analyzed for fatty acid composition. Select-line cows produced more milk (44.4 vs. 31.2 kg/d) and milk components than CL cows during the 16-wk period. There was no difference in rate of milk yield increase, but peak milk yield for SL cows was greater and occurred later in lactation. There were no differences in milk SCC or milk fat, protein, or lactose content. Selection for milk yield did not affect the content of most individual milk fatty acids; however, compared with CL, SL cows had a reduced Delta(9)-desaturase system and tended to produce milk with lower monounsaturated fatty acid content. Selection for milk yield did not affect milk fatty acid origin but the percentage of de novo fatty acids increased and preformed fatty acids decreased as lactation progressed. Milk fat trans-11 18:1 and cis-9,trans-11 conjugated linoleic acid increased with progressing lactation (10.7 vs. 14.1 and 3.1 vs. 5.4 mg/g, or 31 and 76%, respectively) and were correlated strongly among wk 1, 8, and 16 of lactation. Temporal changes in the Delta(9)-desaturase system occurred during lactation but these changes were not correlated with milk fat cis-9,trans-11 conjugated linoleic acid content. Results indicate prolonged genetic selection for milk yield had little effect on milk fatty acid composition, but milk fatty acid profiles varied markedly by week of lactation.     

Genetic correlations of mid-infrared-predicted milk fatty acid groups with milk production traits

The objective of this research was to estimate the genetic correlations between milk mid-infrared-predicted fatty acid groups and production traits in first-parity Canadian Holsteins. Contents of short-chain, medium-chain, long-chain, saturated, and unsaturated fatty acid groupings in milk samples can be predicted using mid-infrared spectral data for cows enrolled in milk recording programs. Predicted fatty acid group contents were obtained for 49,127 test-day milk samples from 10,029 first-parity Holstein cows in 810 herds. Milk yield, fat and protein yield, fat and protein percentage, fat-to-protein ratio, and somatic cell score were also available for these test days. Genetic parameters were estimated for the fatty acid groups and production traits using multiple-trait random regression test day models by Bayesian methods via Gibbs sampling. Three separate 8- or 9-trait analyses were performed, including the 5 fatty acid groups with different combinations of the production traits. Posterior standard deviations ranged from <0.001 to 0.01. Average daily genetic correlations were negative and similar to each other for the fatty acid groups with milk yield (?0.62 to ?0.59) and with protein yield (?0.32 to ?0.25). Weak and positive average daily genetic correlations were found between somatic cell score and the fatty acid groups (from 0.25 to 0.36). Stronger genetic correlations with fat yield, fat and protein percentage, and fat-to-protein ratio were found with medium-chain and saturated fatty acid groups compared with those with long-chain and unsaturated fatty acid groups. Genetic correlations were very strong between the fatty acid groups and fat percentage, ranging between 0.88 for unsaturated and 0.99 for saturated fatty acids. Daily genetic correlations from 5 to 305 d in milk with milk, protein yield and percentage, and somatic cell score traits showed similar patterns for all fatty acid groups. The daily genetic correlations with fat yield at the beginning of lactation were decreasing for long-chain and unsaturated fatty acid groups and increasing for short-chain fatty acids. Genetic correlations between fat percentage and fatty acids were increasing at the beginning of lactation for short- and medium-chain and saturated fatty acids, but slightly decreasing for long-chain and unsaturated fatty acid groups. These results can be used in defining fatty acid traits and breeding objectives.     

Distribution and fatty acid content of phospholipids from bovine milk and bovine milk fat globule membranes

The phospholipid (PL) content was determined comparatively in the milk fat globule membrane (MFGM) and whole milk including their fatty acid profiles. The possible role of milk PLs in defence against pathogens was also addressed. The MFGM and whole milk showed a similar distribution of PL species; however, the fatty acid contents of the PL species were different. Total PL from MFGM showed a decrease in C18:0 content in parallel with an increase in C18:1 and C18:2 and very long-chain fatty acid (more than C20) content. No significant differences in the fatty acid content of phosphatidylcholine and sphingomyelin from either source were found. However, the phosphatidylethanolamine from MFGM had more C18:1 and C18:2 and less C14:0 and C16:0 than that from whole milk. A similar but less pronounced result was found for phosphatidylserine/phosphatidylinositol. Enterotoxigenic Escherichia coli strains failed to bind to PL, which had been previously separated by high-performance thin-layer chromatography.     

Feeding a concentrate rich in rapeseed oil improves fatty acid composition and flavor in Norwegian goat milk

Impaired quality due to a high content of free fatty acids (FFA) and off-flavors has caused challenges in the development of Norwegian goat milk products. The present study aimed to examine the effect of lipid-supplemented concentrates on milk fat content, fatty acid composition, FFA, lipoprotein lipase activity, sensory properties, and size of milk fat globules of goat milk. Thirty goats assigned to 3 experimental groups were fed different concentrates from 60 d in milk (DIM) until late lactation (230 DIM). The diets were (1) control concentrate (no added fat); (2) control concentrate with 8% (added on air-dry basis) hydrogenated palm oil enriched with palmitic acid (POFA); and (3) control concentrate with 8% (added on air-dry basis) rapeseed oil (RSO). The POFA group produced milk with the highest fat content, and fat content was positively correlated with the mean size of milk fat globules. Goats in the RSO group had a higher content of long-chain and unsaturated fatty acids, whereas milk from goats in the POFA group had a higher content of palmitic and palmitoleic acids (C16:0 and C16:1 cis). The control group produced milk with a higher content of short-, medium-, odd-, and branched-chain fatty acids compared with the 2 other groups. The content of FFA in milk was low in early and late lactation and peaked in mid lactation (90 DIM). A high content of FFA was correlated with poor sensory properties (tart/rancid flavor). The RSO group produced milk with lower content of FFA and off-flavors in mid lactation and a higher proportion of unsaturated fatty acids. Therefore, replacement of palm oil with rapeseed oil as a lipid source in dairy goat feed would be favorable.     

Effect of the addition of calcium soap to ewes’ diet on fatty acid composition of ewe milk and subcutaneous fat of suckling lambs reared on ewe milk

The aim of this work was to study the effect of the inclusion of calcium soap (CS) in ewes’ diet on the fatty acid profile of suckling lambs. Sixty suckling lambs of three breeds (Castellana, Churra and Assaf) were divided into two equal groups. One group was fed with a diet composed of beetroot pulp, alfalfa, barley, corn, soy, cotton and 4% of CS, and the other with a control diet without CS. The fatty acid profiles of the ewe’s milk samples collected on the day before slaughter and of the lamb subcutaneous fat collected from the back of the carcasses were analysed. The addition of calcium soap to the ewe’s diet did not change the milk fatty acid profile but significantly increased SFA and decreased both the PUFA and MUFA levels of suckling lamb fat. PCA analysis revealed a good separation of the lamb samples according to the diet of the mothers, showing that diet is more important than breed in explaining sample variability.     

Exploring polymorphisms and effects of candidate genes on milk fat quality in dairy sheep

The aim of the present study was to investigate the genetic control of the fatty acid (FA) composition in milk from 3 breeds of sheep: Altamurana, Gentile di Puglia, and Sarda. Single nucleotide polymorphisms within genes, encoding enzymes putatively involved in the synthesis and metabolism of milk fat, were selected for analysis, and the allele substitution effects were determined for 16 genes, which were polymorphic in the 3 sheep breeds, upon the milk fat composition. Four genes (α-1-antichymotrypsin-2; diacylglycerol O-acyltransferase homolog-2; propionyl Coenzyme A carboxylase, β polypeptide; and insulin-like growth factor-I) play a role in the desaturation of stearic FA into polyunsaturated fatty acids. Furthermore, 2 genes (growth hormone receptor and zona pellucida glycoprotein-2) affect the variability of the total fat content in addition to the butyric and stearic FA profile, and the fatty acid synthetase gene has an influence on the medium-chain FA. Milk FA profiles play an important role in dairy sheep farming because they have a large effect on cheese characteristics and also because sheep milk may be marketed as a source of nutraceuticals because it contains higher levels of conjugated linoleic acid than milk from other ruminants. The current study evaluated the global effects of a large number of single nucleotide polymorphisms and haplotypes on traits that are not commonly investigated in sheep but that are potentially very useful for improving milk quality.     

Comparison of gas chromatographic methods for analysis of butyric acid in milk fat and fats containing milk fat

 The analysis of butyric acid (C4) is of importance for the determination of the proportion of milk fat in mixed fats. Three gas chromatographic methods were compared with regard to their precision for the measurement of C4, i.e. analysis of butyric acid methyl ester after trans-esterification of fat by sodium methylate (method A) or trimethyl sulphonium hydroxide (method B), as well as analysis of free butyric acid (method C), using an internal standard with each method. The examination of 30 milk fats which varied greatly in terms of their C4 content, using methods A, B and C, resulted in mean values of C4 of 3.42 g/100 g fat, 3.71 g/100 g fat and 3.06 g/100 g fat, respectively. The value determined using method B seemed too high, and this may have been due to the presence of co-eluting artefacts, whereas the value determined using method C was clearly too low, and can probably be attributed to losses during sample preparation. The standard deviation (SD) of 0.015 obtained from repeated analyses using method A was quite good. Results obtained using methods B and C had SDs of 0.029 and 0.074, respectively. Different levels of free fatty acids did not affect the results obtained using method A. When method A was checked by analysis of the reference fat, CRM 164, the C4 level determined was found to deviate from the certified C4 content of 3.49 (± 0.06) g/100 g fat by only 0.05 g C4/fat 100 g. Thus method A proved the most suitable for the determination of the proportion of milk fat in mixed fats by analysis of butyric acid. Received: 1 October 1997