Diet-induced milk fat depression: Association with changes in milk fatty acid composition and fluidity of milk fat

This experiment was designed to examine changes in milk fatty acids during fish oil-induced milk fat depression (MFD) and to test the theory that these changes are related to milk fat fluidity. The experiment was divided into three periods: 1) Baseline: all cows (n = 12) received a high fiber diet without fish oil (FO) for 12 days; 2) Treatment: 4 cows/group received the following treatments for 21 days: a) Low fiber diet without FO (LF), b) High fiber diet + FO (HF + FO) and c) Low fiber diet + FO (LF + FO); 3) Post-treatment: cows returned to the baseline diet and were monitored for 12 days. FO was included at 1.6% DM and HF and LF diets had 40 and 26% NDF, respectively. Milk fat content and yield were unchanged by the LF diet, but were reduced by FO diets at both dietary fiber levels and recovered in the post-treatment period. FO diets caused a pronounced reduction in stearic and oleic acid concentrations in milk fat and an equally pronounced increase in trans-18:1 fatty acid concentrations. Milk fat mean melting point (MMP) was correlated with MFD (r = 0.73) and with milk oleic acid concentration (r = − 0.92). The ratio of oleic:stearic in milk fat increased gradually and consistently in response to FO. Trans-C18:1 isomers with double bounds at carbon ≤ 10 increased with greater MFD and those with double bonds at carbon ≥ 11 decreased with greater MFD. Trans-9 cis-11 CLA explained more than 80% of MFD and was strongly correlated with trans-10 C18:1. Maintenance of MMP below 39–40 °C suggests that the mammary gland was able to secrete only milk fat with adequate fluidity and that MFD could be an adaptation mechanism to prevent secretion of milk with higher MMP.     

Effects of feeding roasted safflower seeds (variety IL-111) and fish oil on dry matter intake, performance and milk fatty acid profiles in dairy cattle

Safflower seed has the highest concentration of linoleic acid among 80 oilseeds but little information exists on the effective use of SS for lactation cows. It was hypothesised that a diet supplemented with an Iranian SS variety (IL-111) in combination with fish oil (FO) would result in higher concentrations of trans-18:1 (including vaccenic acid) and conjugated linoleic acids in milk fat than feeding an unsupplemented control diet. Our objective was to determine the effects of feeding diets containing: (i) Control: (C); (ii) 25 g of roasted SS IL-111 (RSS); (iii) 20 g FO and (iv) 25 g RSS + 10 g FO (RSS + FO) per kilogram of dietary DM on feed intake, ruminal fermentation, milk production and fatty acid profile. Eight multiparous Holstein cows were used in a replicated 4 × 4 Latin square design study. The experiment had four periods of 21 days. Milk Fat percentage was lower (p < 0.01) with FO supplementation and averaged 19.0 and 21.5 g/kg milk with FO and RSS + FO compared with 30.3 and 32.5 g/kg with C and RSS. Feed intake also was lower (p < 0.01) with FO vs. C (23.1 vs. 24.5 kg/day) but feeding RSS resulted in greater feed intake compared with other treatments (26 kg/day). Despite lower feed intake with FO, milk production did not change from controls but feeding RSS + FO resulted in greater milk yield than controls (42.6 vs. 39.3 kg/day). Ruminal pH was greater (p < 0.01) in cows fed FO than other treatments. Supplemental FO alone or in combination with RSS resulted in dramatic increases (p < 0.01) in c9,t11-18:2 in milk fat (12.7 and 13.2 g/day vs. 5.8 and 7.02 with C and RSS). It was surprising to note that 25 g/kg RSS can improve feed intake.     

Biologic quality of colostrum and calves from dairy cows injected with zinc during pregnancy]

The effects of an administration of the Zindep inj. preparation (Biotika) were evaluated in pregnant dairy cows as exerted on specific weight, total protein (TP) content, total immunoglobulin (IgC) and albumin (ALB) contents in colostrum. These parameters were also followed: calf's health, live weight, leucocyte (Lc) counts, T-lymphocyte (T-Ly) counts, contents of TPs, IgCs and ALBs in the blood serum of calves. Zinc concentrations were determined in colostrum, milk and calf blood serum. Our observations included 16 dairy cows in the seventh month of pregnancy in the second lactation and their calves in the winter feeding season. Eight experimental dairy cows were treated with the Zindep preparation in form of an injection to the neck muscles at a dose of 3 mg Zn/kg live weight in the mid-seventh month of pregnancy. Blood samples were taken from v. jugularis from all calves before their first drinking, on days 5, 15 and 30 of age. Colostrum, and/or milk samples were obtained by drawing of the colostrum or milk from the udder quarters within 60 minutes after parturition, on days 5 and 15 of lactation. Zn levels at birth were 16.48 +/- 2.67 mumol/l in experimental calves and 13.84 +/- 3.19 mumol/l in control calves. Zincaemia decreased slightly in both groups on days 5 and 15 of age, but it was insignificantly higher in calves coming from Zindep-treated dairy cows. Zn levels in the blood serum on the 30th day of age were 18.45 +/- 2.44 mumol/l in experimental animals and 15.73 +/- 3.11 mumol/l in control animals. Zn content in the colostrum of experimental cows was 2.40 +/- 0.42 mg/l and in the control it was 1088 +/- 0.52 mg/l (P < 0.05). On day 5 of lactation, Zn amounts in the milk of experimental dairy cows decreased to 0.95 +/- 0.12 mg/l and to 0.76 +/- 0.10 mg/l in the control (P < 0.01). Zn levels in the milk of experimental cows on day 15 of lactation were 0.95 +/- 0.13 mg/l and in the milk of control group they were 0.82 +/- 0.14 mg/l. Colostrum specific weight from zinc-treated cows was 1,067.86 +/- 0.75 g/cm3 and 1,056.8 +/- 13.53 g/cm3 in the control. TP and IgC concentrations were 137.81 +/- 38.11 g/l and 110.13 +/- 29.91 U ZST, respectively, in the colostrum of experimental group, and 105.98 +/- 32.02 g/l and 85.53 +/- 25.42 U ZST, resp., in control animals.(ABSTRACT TRUNCATED AT 400 WORDS)     

Effects of postpartum dietary fat and body condition score at parturition on plasma, adipose tissue, and milk fatty acid composition of lactating beef cows

Two experiments were conducted with lactating Angus x Gelbvieh beef cows to determine the effects of postpartum lipid supplementation, BCS at parturition, and day of lactation on fatty acid profiles in plasma, adipose tissue, and milk. In Exp. 1, 36 pri-miparous cows (488 +/- 10 kg of initial BW; 5.5 +/- 0.02 initial BCS) were given ad libitum access to hay and assigned randomly to a low-fat (control) supplement or supplements with cracked, high-linoleate safflower seeds (linoleate) or cracked, high-oleate safflower seeds (oleate) from d 3 to 90 of lactation. Diets were formulated to be isonitrogenous and isocaloric; safflower seed diets provided 5% of DMI as fat. Plasma and milk samples were collected on d 30, 60, and 90 of lactation. Adipose tissue biopsies were collected near the tail-head region of cows on d 45 and 90 of lactation. In Exp. 2, 3-yr-old cows achieving a BCS of 4 +/- 0.07 (479 +/- 36 kg of BW) or 6 +/- 0.07 (580 +/- 53 kg of BW) at parturition were used in a 2-yr experiment (n = 36/yr). Beginning 3 d postpartum through d 61 of lactation, cows were fed diets similar to those of Exp. 1. Adipose tissue and milk samples were collected on d 30 and 60, and plasma was collected on d 31 and 61 of lactation. Responses to postpartum dietary treatment were comparable in both experiments. Cows fed linoleate and oleate had greater (P < 0.001) total fatty acid concentrations in plasma than cows fed control. Except for 15:1, milk fatty acids with <18 carbons were greatest (P < or = 0.01) for cows fed control, whereas milk from cows fed linoleate had the greatest (P < or = 0.02) 18:1trans-11, 18:2n-6, and cis-9, trans-11 CLA. Milk from cows fed oleate had the greatest (P < 0.001) 18:1cis-9. In Exp. 1, total fatty acid concentrations in adipose tissue samples decreased at d 90 compared with d 45 of lactation, but the fatty acid profile of cow adipose tissue was not affected (P = 0.14 to 0.80) by dietary treatment. In Exp. 2, the percentage of cis-9, trans-11 CLA in adipose tissue of cows with a BCS of 6 decreased (P = 0.001) from d 30 to 60 of lactation. Plasma and milk fatty acid composition reflected alterations in postpartum diet. Less medium-chain fatty acids and more 18-carbon fatty acids in milk were indicative of reduced de novo fatty acid synthesis in the mammary gland of beef cows fed lipid supplements; however, the metabolic demands of lactation prevented the deposition of exogenously derived fatty acids in adipose tissue through d 90 of lactation.     

Postpartum supplemental fat, but not maternal body condition score at parturition, affects plasma and adipose tissue fatty acid profiles of suckling beef calves

Three-year-old Angus x Gelbvieh beef cows, which were nutritionally managed to achieve a BCS of 4 +/- 0.07 (479 +/- 36 kg of BW) or 6 +/- 0.07 (580 +/- 53 kg of BW) at parturition, were used in a 2-yr experiment (n = 36/yr) to determine the effects of maternal BCS at parturition and postpartum lipid supplementation on fatty acid profile of suckling calf plasma and adipose tissue. Beginning 3 d postpartum, cows within each BCS were assigned randomly to 1 of 3 treatments in which cows were all fed hay and either a low-fat (control) supplement or supplements with either high-linoleate cracked safflower seeds (linoleate) or high-oleate cracked safflower seeds (oleate) until d 61 of lactation. Diets were formulated to be isonitrogenous and isocaloric, and safflower seed supplements were provided to achieve 5% of DMI as fat. Total concentration of fatty acids in plasma did not differ (P = 0.48) due to maternal BCS at parturition. Percentage of 20:5n-3 in plasma tended (P = 0.06) to be greater for calves suckling cows with a BCS of 6 at parturition. No other differences (P = 0.12 to 0.99) were noted in calf plasma fatty acid profile due to maternal BCS at parturition. Likewise, no differences were detected for total fatty acid concentration (P = 0.88) in calf adipose tissue due to maternal BCS at parturition. Weight percentage of 14:1 (P = 0.001) was greatest in adipose tissue of calves suckling cows fed control and oleate; however, the percentages of 14:0, 15:0, 16:0, 16:1, 17:0, and 18:3n-3 were greater (P < 0.001) in adipose tissue from calves suckling cows fed control compared with calves suckling cows fed linoleate or oleate. Percentages of 18:0, 18:1trans-11, 18:2n-6, and cis-9, trans-11 CLA were greater (P < 0.001) in adipose tissue from calves suckling cows fed linoleate compared with calves suckling cows fed control and oleate. Calves suckling cows fed oleate had greater (P < 0.001) percentages of 18:1trans-9, 18:1trans-10, and 18:1cis-9 in adipose tissue than calves suckling cows fed control or linoleate. Calf plasma and adipose tissue fatty acid profiles were reflective of milk fatty acids. Because fatty acids play an important role in metabolic regulatory functions, changes in milk fatty acid profile should be considered when beef cows are fed lipid supplements.     

Effects of flaxseed supplementation on milk production, milk fatty acid composition and nutrient utilization by lactating dairy cows.

Twelve multiparous Holstein cows at 72 +/- 20 days in milk were used in a switch-back design with 14-d periods to determine the effect of replacing barley grain into a dairy total mixed ration with micronized or raw flaxseed on nutrient digestibility, milk yield, milk composition. Total mixed diets were (DM basis) 50% barley silage, 50% concentrate mix mainly rolled barley grain and canola meal. Diets were supplemented with 1 kg raw (RF) or micronized (MF) flaxseed to substitute 1 kg of rolled barley grain (C). Neutral detergent fibre, ADF and CP digestibility of the diets were not significantly affected by supplementation; however, calcium digestibility was reduced by 62% and 46% when raw and micronized flax were fed, respectively. Milk yield (38.3, 39.6, and 38.4 kg/d for diets C, RF and MF, respectively) was similar for all diets. Milk fat (3.50, 3.48, and 3.52%) and protein (3.31, 3.34, and 3.31%) for diets C, RF and MF, respectively, were not affected by treatment diets. Concentrations of c9, t11 conjugated linoleic acid (CLA; 0.51, 0.72 and 0.76 g/100 g fatty acids) in milk fat increased (P<0.05) similarly among the two flaxseed supplemented diets. The RF and MF diets significantly increased the C18:1, C18:1 trans-11, C18:2 cis-9, cis-12 and C18:3 in milk fat however, C12:0, C14:0 and C16:0 were significantly reduced compared with control. Replacing barley grain with flaxseed in the diet of lactating cows increased the beneficial fatty acids in milk without depressing nutrient digestibility. Micronization of flaxseed did not reveal any advantage over raw flaxseed.     

泌乳早期奶牛瘤胃微生物与牛奶脂肪酸组成的变化

旨在研究泌乳早期奶牛瘤胃微生物与牛奶脂肪酸组成的变化。本试验选取江苏省某奶牛场胎次、泌乳天数及产奶量相近的50头荷斯坦奶牛,收集泌乳7和30 d的奶样和瘤胃液样品,测定采食量、产奶量、乳成分及乳脂肪酸含量,同时采用16S rRNA测序技术分析瘤胃微生物的组成。结果表明,泌乳7 d的干物质采食量（15.79 kg·d^-1）和产奶量（26.81 kg）均极显著低于泌乳30 d的干物质采食量（18.87 kg·d^-1）和产奶量（37.47 kg）（P<0.01）,而泌乳7 d的乳脂率、乳蛋白率和体细胞评分均极显著高于泌乳30 d （P<0.01）;泌乳7 d乳中的C6：0、C8：0、C10：0、C12：0、C14：0、C14：1trans9、C14：1cis9、C15：1trans10、中链脂肪酸（MCFA）和饱和脂肪酸（SFA）的含量显著低于泌乳30 d （P<0.05）,相反地,C17：0、C17：1cis10、C18：1trans6、C18：1trans11、C18：1cis9、C18：1cis11、C19：1trans10、C22：5cis4,7,10,13,16、长链脂肪酸（LCFA）、单不饱和脂肪酸（MUFA）和反式脂肪酸（TRANS）的比例显著高于泌乳30 d （P<0.05）。16S rRNA测序结果表明,泌乳7和30 d奶牛瘤胃细菌的丰富度与多样性未发生显著变化（P>0.05）。在属水平上,泌乳7 d奶牛瘤胃内的瘤胃梭菌属（Ruminiclostridium_1）、瘤胃球菌属（Ruminococcaceae_UCG_014和Ruminococcaceae_UCG_005）、梭菌属（Clostridium_sensu_stricto_1）、小杆菌属（Dialister）丰度显著低于泌乳30 d （P<0.05）,而球藻菌属（Sphaerochaeta）、弯曲菌属（Campylobacter）和真细菌（Eubacterium_saphenum_group）属的丰度显著高于泌乳30 d （P<0.05）。此外,牛奶脂肪酸与瘤胃微生物组数据关联分析显示,瘤胃微生物对乳中MCFA含量影响较小,纤维素降解细菌（Ruminiclostridium_1、Ruminococcaceae_UCG_005）与乳中C17：0、C18：1trans6、C18：1trans11和C19：1trans10的含量显著负相关（P<0.05）。综上所述,奶牛泌乳早期在生理和采食量上发生了变化,导致瘤胃微生物组成发生改变,进而引起微生物代谢产物和代谢路径发生变化,最终引起产奶量和乳成分的变化,本研究为解析瘤胃微生物调控乳脂代谢机制提供了科学依据,也为产后奶牛营养调控和提高原料乳品质提供了理论基础。     

Effect of restricted suckling on milk yield,composition and flow,udder health,and postpartum anoestrus in grazing Holstein cows

The effect of restricted suckling on milk yield and composition, udder health, and postpartum anoestrus in dairy cows in pasture-based systems, was studied in 32 Holstein multiparous cows and their calves. At calving, each cow–calf pair was randomly assigned to one of two treatments: restricted suckling (RS) of the cows by her own or another calf, twice daily for 30 min or artificial rearing (AR) of the calves with milk obtained from the bulk tank, offered twice a day in buckets. Treatments were applied until week 8 after calving. The diet of the cows consisted of direct grazing in improved pastures, corn silage and a commercial concentrate which was offered at milking. Milk production and composition, udder health, body condition score of the cows, body weight and milk intake of the calves were measured weekly, and the first postpartum ovulation was determined three times a week by ovarian ultrasonography. Cows with RS management had a lower machine-milked milk yield (17.9 vs. 24.8 kg/d), a lower fat percentage (3.21 vs. 4.11%) and 4% fat-corrected milk yield (16.2 vs. 25.7 kg/d), and also a lower average milk flow (1.35 vs. 1.76 kg/min) than cows in the AR treatment. There was no effect of treatment on milk protein percentage or udder health as measured by milk electrical conductivity. The interval from calving to first postpartum ovulation was shorter in the AR cows than in the RS cows (18.5 vs. 21.8 days). The RS calves consumed more milk (7.2 vs. 5.4 kg/d), gained more body weight (0.813 vs. 0.656 kg/d), and had a higher body weight at weaning (84.3 vs. 73.3 kg) than AR calves. Restricted suckling of grazing dairy cows had a negative effect on machine-milked milk yield, fat percentage and 4% fat-corrected milk yield, but had no effect on udder health or on improved weight gain and body weight at weaning of the calves.     

Sainfoin (Onobrychis viciifolia) silage in dairy cow rations reduces ruminal biohydrogenation and increases transfer efficiencies of unsaturated fatty acids from feed to milk

The effects of replacing grass silage by sainfoin silage in a total mixed ration (TMR) based diet on fatty acid (FA) reticular inflow and milk FA profile of dairy cows was investigated. The experiment followed a crossover design with 2 dietary treatments. The control diet consisted of grass silage, corn silage, concentrate and linseed. In the sainfoin diet, half of the grass silage was replaced by a sainfoin silage. Six rumen cannulated lactating multiparous dairy cows with a metabolic body weight of 132.5 ± 3.6 kg BW^0.75, 214 ± 72 d in milk and an average milk production of 23.1 ± 2.8 kg/d were used in the experiment. Cows were paired based on parity and milk production. Within pairs, cows were randomly assigned to either the control diet or the sainfoin diet for 2 experimental periods (29 d per period). In each period, the first 21 d, cows were housed individually in tie-stalls for adaptation, then next 4 d cows were housed individually in climate-controlled respiration chambers to measure CH₄. During the last 4 d, cows were housed individually in tie stalls to measure milk FA profile and determine FA reticular inflow using the reticular sampling technique with Cr-ethylenediaminetetraacetic acid disodium salt dihydrate (EDTA) and Yb-acetate used as digesta flow markers. Although the dietary C18:3n-3 intake was lower (P = 0.025) in the sainfoin diet group, the mono-unsaturated FA reticular inflow was greater (P = 0.042) in cows fed the sainfoin diet. The reticular inflow of trans-9, trans-12-C18:2 and cis-12, trans-10 C18:2 was greater (P ≤ 0.024) in the sainfoin diet group. The cows fed sainfoin diet had a lower (P ≤ 0.038) apparent ruminal biohydrogenation of cis-9-C18:1 and C18:3n-3, compared to the cows fed the control diet. The sainfoin diet group had greater (P ≤ 0.018) C18:3n-3 and cis-9, cis-12-C18:2 proportions in the milk FA profile compared to the control diet group. Transfer efficiencies from feed to milk of C18:2, C18:3n-3 and unsaturated FA were greater (P ≤ 0.0179) for the sainfoin diet. Based on the results, it could be concluded that replacing grass silage by sainfoin silage in dairy cow rations reduces ruminal C18:3n-3 biohydrogenation and improves milk FA profile.     

奶牛泌乳盛期补饲碘的效果

选用１５头泌乳盛期荷斯坦牛，采用对比试验研究日粮中添加碘对奶牛产奶量的影响，结果是：补饲Ｋ１１５和２５ｍｇ／头．日组的日平均奶量分别比对照组高３．４９千克（Ｐ＜０．０５）和２．７６千克（Ｐ＜０．０５）。两个试验组之间日平均奶量无显著差异（Ｐ＞０．０５）。三个组牛血清中Ｔ４和Ｔ３浓度无明显差异。     

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.     

华北地区规模化奶牛场用水及粪污处理情况调查报告

本次调研共收集了华北地区99家奶牛场的用水及粪污处理情况数据进行了分析总结。结果表明,①85.9%的牛场以深井水作为水源,其中61.2%的牛场对用水进行消毒处理,43.5%的牛场安装有水表并记录用水情况。②在牛场用水中,牛的饮水量所占比例最高,达60%以上;其次为挤奶厅用水,约占20%。③夏季牛场头均饮水量、挤奶厅用水量、喷淋用水量均显著高于春秋冬季(P<0.05),夏季的头均总用水量比春秋冬季增加了33%(P<0.01)。随着牛场存栏量的增大,奶牛头均总用水量显著减少(P<0.05)。④年产奶量较高的牛场每产1kg牛奶饮水量、挤奶厅用水量显著降低(P<0.01),致使每千克产奶量的总用水量减少52%(P<0.01),用水效率提高。⑤随着养殖规模的增大,牛场雨污分离设施与干湿分离设施配备率分别显著增至62%、72%(P<0.05,P<0.01)。由此可得,存栏量越大、年产奶量越高,牛场每产1kg牛奶用水量越低,用水效率越高,而且配备的雨污分离设施、干湿分离设施比例越高,这些均有利于减少单位产奶量的粪污产生量及其处理压力。     

The influence of an increased cobalt supply to dairy cows on the vitamin B status of their calves

In the experiment the influence of an elevated oral cobalt supply (Co content in the ration 0.27 mg Co/kg DM; supplement of 0.14 mg Co/kg DM as CoSO(4)) to pregnant dairy cows on the vitamin B(12) concentration in milk, colostrum and vitamin B(12) status of their calves was tested in comparison with unsupplemented controls (0.13 mg Co/kg DM). While there was no significant difference in vitamin B(12) concentration in the at 70th day of lactation (start of the experiment; 3.77 +/- 1.41 vs. 3.66 +/- 1.03 ng/ml) and 290th day of lactation (almost drying off; 4.75 +/- 3.05 vs. 4.44 +/- 0.96 ng/ml), cobalamin concentration in the milk colostrum showed a tendency towards a higher cobalt content in the ration of the supplemented cows in comparison with the controls (21.0 +/- 8.4 vs. 16.7 +/- 11.9 ng/ml). Differences in the vitamin B(12) concentration in the serum of the newborn calves before and after ingestion of colostrum were not detected. From these results it can be concluded that cobalt content of 0.13 mg Co/kg DM in the ration based on wilted grass silage seems to be sufficient for pregnant dairy cows.     

奶牛碘缺乏症及其防治试验

对４２ 份奶牛饲料碘、６ 份饮水碘和１３８ 份血清蛋白结合碘（ＰＢＩ） 进行测试。临床检查８２３ 头奶牛, 选取２３２ 头, 每天日粮添加０－４１ ｍｇ／ｋｇ碘, 连续饲喂３００ ｄ , 探讨奶牛碘缺乏及添加效应。结果表明： 奶牛日粮碘０－１４ ｍｇ／ｋｇ, 饮水碘７－７３ μｇ／Ｌ, 含碘量严重缺乏。奶牛血清ＰＢＩ测值有４２－９９ ％ 低于正常范围的下限２－４ μｇ／１００ｍＬ。进一步分析, 颌下水肿奶牛ＰＢＩ为２－１３８ μｇ／１００ ｍＬ（ ｎ ＝ ２１） , 肉垂肿大奶牛ＰＢＩ为２－７９８ μｇ／１００ ｍＬ（ ｎ＝ １４） , 流产奶牛ＰＢＩ为２－２１６ μｇ／１００ ｍＬ （ｎ ＝ １１） , 产死胎、弱犊占１９－５６ ％ （６３／３１７） 的ＰＢＩ为１－６２６ μｇ／１００ ｍＬ （ ｎ ＝ ３１） , 尿酮阳性奶牛ＰＢＩ为１－４７７ μｇ／１００ ｍＬ （ ｎ ＝ ３４） , 尿酮阴性奶牛ＰＢＩ为２－１８ μｇ／１００ ｍＬ（ ｎ ＝ ２９） , 两者差异极显著（ Ｐ＜ ０－０１） 。日粮添加碘使奶牛血清ＰＢＩ上升至５－５４４μｇ／１００ ｍＬ, 死胎率下降到６－７８ ％ （１２／１７７） , 咽喉周围及垂肉粘液性水肿消失, 生产性能和繁殖性能均得到改善。     

不同品种牛乳营养成分含量及脂肪酸含量和组成测定比较研究

[目的] 比较中国荷斯坦奶牛、荷斯坦奶牛和西门塔尔牛乳中常规营养成分含量、矿物质元素含量及脂肪酸含量和组成的差异。[方法] 选取中国荷斯坦奶牛、荷斯坦奶牛和西门塔尔牛各6头,每头奶牛收集200 mL生鲜乳样品,利用乳成分分析仪测定乳中常规营养成分含量,通过原子吸收分光光度计测定乳中矿物质元素含量,应用气相色谱仪测定乳中脂肪酸含量和组成。采用统计学方法对不同品种牛乳中的营养成分含量及脂肪酸含量和组成进行比较。[结果] 中国荷斯坦奶牛生鲜乳中乳脂含量显著（P<0.05）高于荷斯坦奶牛,乳蛋白含量显著（P<0.05）高于荷斯坦奶牛和西门塔尔牛;中国荷斯坦奶牛生鲜乳中乳钙含量显著（P<0.05）高于荷斯坦奶牛,乳锌含量显著（P<0.05）高于荷斯坦奶牛和西门塔尔牛。中国荷斯坦奶牛生鲜乳中豆蔻酸含量显著（P<0.05）低于荷斯坦奶牛,油酸和亚油酸含量显著（P<0.05）高于西门塔尔牛;中国荷斯坦奶牛生鲜乳中饱和脂肪酸含量显著（P<0.05）低于西门塔尔牛,不饱和脂肪酸含量显著（P<0.05）高于西门塔尔牛。[结论] 中国荷斯坦奶牛乳中部分营养成分和矿物质元素含量接近或优于荷斯坦奶牛和西门塔尔牛,脂肪酸含量和组成与荷斯坦奶牛相近,脂肪酸组成优于西门塔尔牛。     

过瘤胃甜菜碱对隐性乳房炎奶牛生产性能的影响

选择15头体细胞数在100万个/mL以上奶牛,随机分为3组,每组5头,分别在日粮中添加0g/d、18g/d和24g/d过瘤胃甜菜碱,研究其对隐性乳房炎奶牛产奶性能和体细胞数的影响。结果发现:对照组奶牛产奶量与试验前相比,下降了1.04kg,而试验组分别提高了0.52kg和0.88kg;乳脂率、乳蛋白等乳成分略有提高,但差异均不显著。添加过瘤胃甜菜碱组牛奶中体细胞数显著降低,与对照组相比,差异显著(P<0.05)。表明隐性乳房炎奶牛补饲过瘤胃甜菜碱,能够降低牛奶中体细胞数,提高奶牛产奶性能。     

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.     

Appearance and disappearance of swainsonine in serum and milk of lactating ruminants with nursing young following a single dose exposure to swainsonine (locoweed; Oxytropis sericea)

A series of experiments were conducted to investigate the elimination of swainsonine in the milk of lactating ruminants following a single dose oral exposure to swainsonine (locoweed; Oxytropis sericea) and to assess subsequent subclinical effects on the mothers and their nursing young. In a preliminary experiment, lactating ewes were gavaged with locoweed providing 0.8 mg swainsonine/kg BW (n = 4; BW = 75.8 +/- 3.6 kg; lactation = d 45) and lactating cows were offered up to 2.0 mg swainsonine/kg BW free choice (n = 16; BW = 389.6 +/- 20.9 kg; lactation = d 90). Serum and milk were collected at h 0 (before treatment), 3, 6, 12, and 24 for ewes, and h 0 (before treatment), 6, 12, 18, and 24 for cows. Swainsonine was highest (P < 0.05) by h 6 in the serum and milk of ewes. Consumption of at least 0.61 mg swainsonine/kg BW induced consistent (> 0.025 microg/mL) appearance of swainsonine in cow serum and milk. In response to the results obtained in the preliminary experiment, a subsequent experiment utilizing lactating ewes (n = 13; BW = 74.8 +/- 6.4 kg; lactation = d 30) and cows (n = 13; BW = 460.8 +/- 51.9 kg; lactation = d 90) was conducted. Each lactating ruminant was gavaged with a locoweed extract to provide 0 (control), 0.2, or 0.8 mg swainsonine/kg BW and individually penned with her nursing young. Serum and milk from the mothers and serum from the nursing young were collected at h 0 (before treatment), 3, 6, 9, 12, 24 and 48 (an additional sample was obtained at h 72 for ewes and lambs). Serum and milk swainsonine was higher (P < 0.05) in the 0.8 mg treated groups and maximal (P < 0.05) concentrations occurred from h 3 to 6 for ewes and h 6 to 12 h for cows (P < 0.05). Rises in alkaline phosphatase activity indicated subclinical toxicity in the treated ewes (P < 0.05). Following a single dose oral exposure to 0.2 and 0.8 mg swainsonine/kg BW provided by a locoweed extract, swainsonine was detected in the serum and milk of lactating ewes and cows, and rises in serum alkaline phosphatase activity were observed in the ewes. Neither swainsonine nor changes in alkaline phosphatase activity was detected in the serum of the lambs and calves nursing the ewes and cows dosed with swainsonine.     

高寒地区秋、冬季荷斯坦奶牛补饲优质饲料对采食量、泌乳性能和乳房炎发病率的影响

[目的]旨在研究高寒地区荷斯坦奶牛优化补饲方案的推广价值。[方法]实验选取A、B牧场无临床型乳房炎健康泌乳牛为研究对象,将两座实验牧场奶牛,分别各自分为实验组和对照组。实验组饲喂优质补饲日粮,对照组饲喂传统日粮,实验牛只每天放牧5 h。实验期为60 d,10 d为预饲期,50 d为实验期。[结果]A、B牧场实验组补饲的日粮干物质采食量分别为15.77、16.11 kg/d,明显高于对照组（14.02、14.47 kg/d）。A牧场实验组单产为16.89 kg/d,对照组单产为12.25 kg/d,差异显著（P〈0.05）;B牧场实验组单产为17.22 kg/d,对照组单产为13.21 kg/d,同样差异显著（P〈0.05）;同时A牧场与B牧场实验组的单产在与2014同期相比时同样差异显著（P〈0.05）。A牧场每千克奶饲料成本降低0.26元,与对照组相比差异显著（P〈0.05）,B牧场降低0.13元。A牧场实验组的牛奶乳脂率和乳蛋白含量明显高于对照组,分别为3.95%和3.28%,和2014年同期相比分别增长了0.29%和0.22%;B牧场实验组牛奶乳脂率和乳蛋白含量虽然低于对照组,但也达到了4.08%和3.15%。A牧场实验组牛奶体细胞数（39.14万个/m L）比对照组体细胞数（60.54万个/m L）低21.40万个/m L。临床型乳房炎患病牛的比例,实验组低于对照组近2.67%。[结论]高寒地区荷斯坦奶牛可实行优化补饲方案,且能够提高企业和养殖户的经济效益,具有较好的推广价值。     

Effects of conjugated linoleic acids (CLA) on tissue response to homeostatic signals and plasma variables associated with lipid metabolism in lactating dairy cows

We conducted a series of experiments to evaluate the effects of conjugated linoleic acids (CLA) on lipid metabolism and energy homeostasis in lactating dairy cows. In all experiments, multiparous Holstein cows in mid to late lactation were abomasally infused with CLA for 5 d. The initial study established that trans-10, cis-12 CLA markedly reduced milk fat yield whereas cis-9, trans-11 CLA, the predominant CLA isomer in milk fat, had no effect. Across the three investigations, infusions of the pure trans-10, cis-12 CLA isomer (3.5 to 14.0 g/d) resulted in a 25 to 50% decrease in milk fat yield and this was energetically equivalent to 6 to 11% of net energy intake. Effects were specific for milk fat as there were little or no changes in feed intake and the yield of milk or milk protein. In Exp. 1, infusing trans-10, cis-12 CLA had no effect on circulating plasma concentrations of glucose, insulin, or leptin. Basal NEFA concentrations were also unaffected, but lipolytic response to an epinephrine challenge was reduced (33%) when cows received trans-10, cis-12 CLA; this minor change in lipolytic response would be consistent with the slightly more positive net energy balance when cows received trans-10, cis-12 CLA. In Exp. 2, infusing differing amounts of trans-10, cis-12 CLA had only minor effects on basal NEFA concentrations, but again cows receiving trans-10, cis-12 CLA tended to have reduced (24%) lipolytic response to trans-10, cis-12 CLA compared to the control period. In Exp. 3, infusing trans-10, cis-12 CLA had no effect on basal glucose concentrations or glucose response to an insulin challenge. The fractional rate of glucose clearance in response to insulin was also not altered by treatment. In summary, the effects of trans-10, cis-12 CLA in lactating dairy cows appear to be specific for the mammary gland, resulting in reduced milk fat synthesis; adipose tissue response to a homeostatic signal regulating lipolysis (epinephrine), whole-body response to a homeostatic signal regulating glucose homeostasis (insulin), and plasma variables associated with lipid metabolism and energy homeostasis were relatively unaffected by treatment with trans-10, cis-12 CLA.