头胎与经产奶牛围产期生产性能和血清生化指标的比较

为比较头胎奶牛与经产奶牛在围产阶段生产性能和血清生化指标的差异,本研究选取临床健康的头胎和经产奶牛各10头,在同等条件下饲喂全混合日粮,于预产期前7、4、2、1 d及产后0、1、2、4、7、14 d晨喂前尾静脉采血并分离血清,测定血糖、甘油三酯和血钙浓度,产后11~40 d记录产奶量,于产后第30天采集乳样,测定乳成分和体细胞数。结果显示,头胎奶牛与经产奶牛血清甘油三酯、乳脂、乳蛋白、乳糖和乳干物质等指标均无显著差异（P>0.05）;经产牛产后日均产奶量和乳体细胞数均显著高于头胎牛（P<0.05）;在分娩前第4天和分娩后第2、4天时,头胎牛血糖浓度显著高于经产牛（P<0.05）,但在分娩时,头胎牛血糖浓度显著低于经产牛（P<0.05）;头胎牛在产前第1、2天、分娩当天及产后第2天的血钙水平显著高于经产牛（P<0.05）。     

The change of dry matter intake, milk yield and bone turnover in primiparous cows compared to multiparous cows during early lactation

Data from six primiparous and nine multiparous Holstein cows were used to clarify the difference of Ca and P mobilization between primiparous and multiparous cows during early lactation. The dry matter intake (DMI) of primiparous cows was lower (P < 0.01) than those of multiparous cows. Milk yield was lower in primiparous cows at 7, 14, 21 (P < 0.01), and 28 days (P < 0.05) after parturition. There was no significant difference in milk Ca and P concentrations between primiparous and multiparous cows. There were no significant differences in plasma Ca and P concentrations between primiparous and multiparous cows. The plasma P level at 7 days postpartum in primiparous cows was lower (P < 0.05) than 28 days postpartum. The concentration of plasma osteocalcin (OC) measured as bone formation marker of primiparous cows was significantly higher than multiparous cows (P < 0.01) at 21 and 28 days postpartum. The urinary deoxypyridinoline (DPD) as bone resorption marker of primiparous cows tended to be higher (P < 0.10) than multiparous cows at 21 days after parturition and decreased to the same level as that of multiparae toward the peak lactation. These results show that Ca and P mobilization of primiparous cows are more active than multiparous cows.     

Effects of calcium intake and parity on plasma minerals and bone turnover around parturition

Eight pregnant heifers (primiparous cows) and seven pregnant cows in their second, third and forth pregnancies (multiparous cows) were assigned to two groups and fed either a low calcium (Ca) diet (Ca, 0.46%) or a high Ca diet (Ca, 0.86%) ad libitum from 3 weeks before the expected calving date to 3 days after parturition. All cows were examined for a change in dry matter intake (DMI), plasma minerals and bone turnover around parturition. The dietary Ca level did not affect the DMI in both primiparous and multiparous cows. The DMI of primiparous cows was significantly lower than that of multiparous cows (P < 0.05) in both the low and high dietary Ca groups. The dietary Ca level did not affect the concentrations of plasma Ca, phosphorus, magnesium and parathyroid hormone throughout the experimental period. Plasma phosphorus in primiparous cows was significantly higher (P < 0.05) than that of multiparous cows around parturition. Plasma Ca and magnesium tended to be higher (P < 0.10) in primiparous cows. The dietary Ca level did not affect the plasma osteocalcin (OC) level measured as bone formation or the urinary deoxypyridinoline (DPD) excretion measured as bone resorption before parturition in both primiparous and multiparous cows. After parturition, the plasma OC level was lower than it was before parturition in multiparous cows fed a low Ca diet, and in primiparous cows. There were no significant differences in urinary DPD excretion between each group before and after parturition. Both the plasma OC level and urinary DPD excretion of primiparous cows were significantly higher than those of multiparous cows in both the low and high dietary Ca groups.     

Relationship between parity and mineral status in dairy cows during the periparturient period

Data from 65 cows were collected to clarify the relationship between parity and mineral status in Holstein cows during the periparturient period. Milk fever occurred in a second‐ and a fourth‐lactation cow at parturition. Bodyweight of cows decreased immediately after parturition, and the decreased weights of cows from 1 to 6 days after parturition ranged from 11 to 27 kg. Milk yield of multiparous cows was higher than that of primiparous cows, but Ca and P concentrations in colostrum were not affected by the parity. Plasma glucose of primiparous cows was higher than that of multiparous cows, and plasma nonesterified fatty acids of fourth‐and‐more‐lactation cows at parturition was highest. Plasma Ca concentration of cows at parturition decreased with advancing parity, and plasma inorganic P concentration of third‐and‐more‐lactation cows was lowest at parturition. Plasma parathyroid hormone of fourth‐and‐more‐lactation cows at parturition was highest, but plasma hydroxyproline and alkaline phosphatase was lowest. These results suggest that the large transfer of Ca and P to colostrum is a factor in the development of milk fever in third‐and‐more‐lactation cows.     

甜菜碱对奶牛采食量、泌乳性能和血液指标的影响

选用20头体重(597±11.8)kg、泌乳天数(88±4.5)d、日产奶(26.3±0.5)kg的经产奶牛,随机分为4组,采用4×4拉丁方设计,研究甜菜碱(0、50、100和150g/d)对泌乳早期奶牛采食量、泌乳性能和血液指标的影响。结果表明:日粮添加甜菜碱对奶牛的采食量、乳蛋白率、乳糖率和血糖浓度无显著影响,100g/d组和150g/d组鲜奶产量显著高于对照组和50g/d组(P<0.05);100g/d组和150g/d组4%乳脂校正乳、能量校正乳和乳脂产量显著高于对照组(P<0.05);100g/d组乳脂率显著高于对照组(P<0.05);100g/d组和150g/d组血浆游离脂肪酸和β-羟丁酸浓度显著低于对照组(P<0.05)。根据以上结果推断,甜菜碱的适宜添加水平为100g/d。     

Relationship between the first ovulation within three weeks postpartum and subsequent ovarian cycles and fertility in high producing dairy cows

The aim of this study was to investigate the relationship between the first ovulation within 3 weeks postpartum and subsequent ovarian cycles and fertility in high producing dairy cattle in Hokkaido, Japan. In Experiment 1, 110 cows (44 primiparous and 66 multiparous) were used to determine the effects of the first ovulation within 3 weeks postpartum on subsequent ovarian cycles. Milk samples were collected twice weekly from 7 to 100 days postpartum. The first ovulation was identified by an increase in milk progesterone (P4) to more than 1 ng/ml within 3 weeks postpartum. The numbers of cows showing ovulation and anovulation within 3 weeks postpartum were 31 (70.5%) and 13 (29.5%) in the primiparous cows and 35 (53.0%) and 31 (47.0%) in the multiparous cows, respectively. The patterns of ovarian resumption after calving were classified into two types (normal ovarian cycles and abnormal ovarian cycles) on the basis of milk P4 concentrations. Initiation of normal ovarian function in cows ovulated within 3 weeks postpartum occurred earlier than in anovulated cows regardless of the number of calvings (primiparous, 27.8 days vs. 44.4 days; multiparous, 30.6 days vs. 55.7 days; P<0.01). Out of the multiparous cows that ovulated within 3 weeks postpartum, initiation of normal ovarian function followed by a normal luteal phase was earlier than when it was followed by an abnormal luteal phase (25.5 days vs. 40.4 days; P<0.05). Milk P4 concentrations after the first ovulation were lower than those after the second ovulation in both the primiparous and multiparous cows (P<0.05). In Experiment 2, 22 multiparous cows were used to determine the effects of the first ovulation within 3 weeks postpartum on subsequent fertility. Blood samples were collected once a week from 0 to 3 weeks postpartum. The interval from parturition to first service in ovulated cows was shorter than in anovulated cows (68.4 days vs. 94.8 days; P<0.05). The conception rate by 100 days after calving tended to be higher in ovulated cows than in anovulated cows (50.0% vs. 16.7%, P=0.09). In conclusion, our data strongly suggests that ovulation within 3 weeks postpartum is a crucial phenomenon for subsequent resumption of ovarian function and conception, and thus it can be used as an index of subsequent reproductive performance.     

中国荷斯坦奶牛不同地区、泌乳天数及胎次的产奶量校正系数研究

本研究通过对规模化牧场测定日数据进行分析,旨在估计不同地区305 d校正产奶量对应泌乳天数(DIM)的校正系数与胎次校正系数。利用Wood(不完全伽玛)模型对来自不同温度带9个参考群11 749头荷斯坦奶牛2010－2020年间的683 160条测定日产奶量拟合泌乳曲线,估计泌乳曲线参数,计算头胎牛和经产牛1~305 d泌乳天数对应的校正系数,分别分析参考群和验证群305 d校正产奶量和305 d实际累积奶量的差异;利用SAS 9.2中混合线性模型对1~6胎至少有前5个胎记录的牛估计305 d奶量的胎次效应值,并计算1~6胎各胎次的乘法校正系数;比较传统系数和新系数校正结果的差异。结果表明:①参考群头胎牛和经产牛中,泌乳曲线方程的拟合度R²范围分别为0.4593~0.4913和0.5796~0.6341,泌乳高峰日分别为79~85和53 d,泌乳高峰奶量分别为33.1~34.4和46.0~48.6 kg;②对于参考群,头胎牛和经产牛校正系数分别在泌乳≥90 d和泌乳≥30 d基本趋于一致,头胎牛和经产牛泌乳≥60 d的305 d校正产奶量均趋近于305 d实际累积奶量,奶量差值分别在100和200 kg以内;③对于验证群的305 d校正产奶量,头胎牛泌乳≥150 d和经产牛泌乳≥180 d的泌乳天数校正系数适用性更佳,305 d校正产奶量与305 d实际累积奶量比值高于79%;④1~6胎的胎次校正系数分别为1.2121、1.0380、1.0063、1.0000、1.0220和1.0290;⑤与传统系数相比,新泌乳天数校正系数校正效果更好,头胎牛和经产牛新系数校正的305 d奶量较305 d实际累积奶量相差分别在900和700 kg以内;利用新胎次校正系数,2~4胎产奶量可较为准确地校正到5胎成年当量。本研究结果表明,定期更新305 d校正产奶量的泌乳天数与胎次校正系数,便于准确地将不同泌乳天数、不同胎次状态下泌乳牛的产奶量调整到同一基准上,从而更好地比较奶牛个体泌乳性能的高低,为牧场管理提供参考依据。     

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.     

利用体外模拟瘤胃发酵技术预测奶牛生产性能的研究

本试验旨在利用全混合日粮（TMR）体外发酵参数预测奶牛的生产性能,采集2头体重550 kg、安装永久瘤胃瘘管的健康荷斯坦奶牛瘤胃液,并取40种不同的TMR进行体外发酵试验,测定体外发酵24 h的乙酸、丙酸、丁酸、氨态氮（NH₃-N）含量,以及甲烷（CH₄）排放量、微生物蛋白质（MCP）、体外干物质消失率（IVDMD）、体外蛋白质消失率（IVCPD）和体外有机物消失率（IVOMD）等指标。记录饲喂不同TMR的奶牛对应的生产性能（产奶量、乳蛋白率、乳脂率）,并与奶牛生产性能之间建立预测模型。结果显示：①产奶量与丙酸含量（r=0.37,P<0.05）、MCP（r=0.40,P<0.05）均呈显著正相关,但与IVCPD（r=-0.44,P<0.01）呈极显著负相关;乳脂率与乙酸含量（r=0.55,P<0.01）、甲烷排放量（r=0.36,P<0.05）、MCP（r=0.40,P<0.05）呈极显著或显著正相关;乳蛋白率与MCP（r=0.91,P<0.01）、IVDMD（r=0.44,P<0.01）、IVCPD（r=0.45,P<0.01）呈极显著正相关,但是与IVOMD（r=-0.56,P<0.01）呈极显著负相关。②奶牛的生产性能可用体外发酵参数作为预测因子进行预测。产奶量（kg/d）=29.72-0.86IVCPD（R²=0.73,RSD²=47.26,P<0.001）;乳脂率（%）=0.40+0.06AA（R²=0.91,RSD²=0.15,P<0.001）;乳蛋白率（%）=1.52+0.06MCP（R²=0.78,RSD²=0.01,P<0.001）。奶牛的生产性能预测值与实际值的误差在允许的范围内,表明预测方程是可行的。     

日粮大豆磷脂对奶牛生产性能和血液生化指标的影响

为研究日粮大豆磷脂水平对泌乳早期奶牛生产性能、消化代谢和血液生化指标的影响,本试验选取8头初产泌乳早期中国荷斯坦奶牛,随机分成4组,每组2头,采用4×4重复拉丁方试验设计进行研究。4种日粮处理中大豆磷脂的添加量分别为日粮干物质基础的0,1%,2%和3%。结果显示:大豆磷脂对奶牛干物质采食量无显著影响(P>0.05),但提高了饲料转化率,尤其是2%添加组饲料转化率显著提高(P<0.05);与对照组相比,2%大豆磷脂组奶牛的产奶量、4%标准乳、日产乳脂量和乳蛋白量显著提高(P<0.05);各组间乳成分和乳体细胞数无显著差异(P>0.05);3%大豆磷脂水平显著降低了酸性洗涤纤维的表观消化率(P<0.05),极显著提高了血清甘油三酯含量(P<0.01),但对粗蛋白、粗脂肪及中性洗涤纤维的表观消化率无显著影响(P>0.05)。结果表明:日粮大豆磷脂能够提高奶牛产奶量,提高奶牛的健康状况和免疫机能,经济效益显著。在奶牛日粮中最佳添加量为2%(干物质基础)。     

益康XP对奶牛血浆内毒素含量及其他指标的影响

选取泌乳天数<40 d的健康奶牛 12头,按胎次、泌乳天数和产奶量相同或相似的原则,分为试验组和对照组。两组日粮组成相同,试验组牛每天添加益康XP的剂量为试验第1天至第7天500 g/(头·d),从第 8 天后减少到120 g/(头·d),分两次饲喂。试验期为60 d。于试验前 1 天,试验第 20 天,40天和第 60 天分别采血,用鲎试剂法测定血浆内毒素含量;定期测定日均产奶量、乳脂率、乳蛋白率和体细胞数;记录情期受胎率及疾病发生情况。结果表明,试验组奶牛在试验后第20天,第 40 天和第 60 天血浆内毒素均极显著低于对照组(P<0.01);产奶量在第20天,第60天显著高于对照组(P<0.05);两组奶牛乳脂率、乳蛋白率、体细胞数差异均不显著(P>0.05);试验组情期受胎率极显著高于对照组(P<0.01);在疾病发生率方面,试验组极显著低于对照组(P<0.01)。     

3种不同类型轻音乐对奶牛泌乳性能及能量代谢指标的影响

本研究旨在探讨3种不同类型的轻音乐对奶牛泌乳性能及能量代谢指标的影响。选用泌乳量、年龄、胎次、泌乳期相近的荷斯坦泌乳牛64头,随机分成4组,即轻音乐A(速度60 bmp的钢琴轻音乐《梁祝》,音色圆润)组、轻音乐B(速度70 bmp、小提琴演奏的泌乳牛情绪调控曲,音色明亮)组、轻音乐C(速度60 bmp、钢琴演奏的奶牛泌乳性能调控曲,音色圆润)组和对照组,每组16头。3个轻音乐组分别于早、中、晚3次挤奶前各播放音乐2 h,对照组无音乐播放。预试期7 d,正试期60 d。正试期每隔20 d测定泌乳量,并采集血样和乳样。结果表明:1)试验20、40 d及1~60 d,轻音乐A组、轻音乐B组和轻音乐C组奶牛干物质、有机物、中性洗涤纤维、酸性洗涤纤维、粗蛋白质和粗脂肪摄入量均高于对照组。2)试验1~60 d,轻音乐C组奶牛泌乳量、4%标准乳产量显著或极显著高于对照组(P0.05或P0.01)。3)试验1~60 d,轻音乐B组和轻音乐C组血液谷草转氨酶、丙氨酸转氨酶活性显著低于对照组(P0.05),轻音乐C组血液谷丙转氨酶、乳酸脱氢酶活性显著低于对照组(P0.05)。4)试验40、60 d,轻音乐C组奶牛血液甘油三酯含量显著高于对照组(P0.05);试验1~60 d,轻音乐C组奶牛血液葡萄糖含量显著高于对照组(P0.05);整个试验期,轻音乐A组、轻音乐B组和轻音乐C组奶牛血液游离脂肪酸含量均低于对照组,但差异不显著(P0.05)。综上所述,3种轻音乐均有提高奶牛营养物质摄入量、刺激泌乳及改善奶牛能量代谢指标的作用趋势;70 bmp的轻音乐较60 bmp的轻音乐对奶牛泌乳更为有利;与音色明亮的轻音乐相比,奶牛对音色圆润的轻音乐敏感性更高,音色圆润的轻音乐更能提高奶牛泌乳性能。     

Milk casein and fatty acid fractions in early lactation are affected by nutritional regulation of body condition score at the beginning of the transition period in primiparous and multiparous cows under grazing conditions

The objective was to evaluate the effect of body condition score (BCS) at 30 days before calving (−30 days) induced by a differential nutritional management, parity and week of lactation (WOL) on milk yield and composition, and milk casein and fatty acid composition. Primiparous and multiparous Holstein cows with high BCS (PH, n = 13; MH, n = 9) and low BCS (PL, n = 9; ML = 8) under grazing conditions were sampled at WOL 2 and 8 (before and after peak of lactation). Milk yield was greater in multiparous than in primiparous cows and tended to decrease from WOL 2 to 8 only in ML cows. Milk protein, fat and casein yields were greater in multiparous than in primiparous cows and decreased from WOL 2 to 8. Milk casein concentration in milk protein was greater in MH cows than in ML, PH and PL cows at WOL 2. Milk κ‐casein was greater, and β‐casein was less in multiparous than in primiparous cows. As lactation progressed, proportion of casein fractions were not altered. Only κ‐casein fraction was affected by BCS at −30 days as PL showed a higher concentration than PH. The de novo (4:0–15:1) and mixed‐origin fatty acids (16:0–16:1) in milk fat increased, whereas preformed fatty acids (≥17:0) decreased from WOL 2 to 8. Saturated (SAT) fatty acids tended to be greater and monounsaturated fatty acids (MUFA) were less in multiparous than in primiparous cows. High‐BCS cows had greater concentrations of polyunsaturated (PUFA), conjugated linoleic acid (CLA) as well as n‐6 and n‐3 fatty acids in milk fat than low‐BCS cows. The results indicate that casein and fatty acid fractions in milk were affected by parity and may be modified by a differential nutritional management during the pre‐calving period (BCS at −30 days) in cows under grazing conditions.     

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.     

Plasma thiobarbituric acid reactive substances,vitamin A and vitamin E levels and resumption of postpartum ovarian activity in dairy cows

Vitamins with antioxidative functions are commonly used as supplements to improve fertility in dairy cows. However, according to field test results uncertainty exists about the effect of these vitamins, especially in vitamin A and vitamin E, on ovarian functional activity. This study was performed to reveal the physiological characteristics of cows receiving enough feed and the ovaries of which were activated in the early postpartum period. Six of 12 primiparous cows showing the corpus luteum on 25 to 27 days after parturition were classified as early responders (PER); the remaining six were classified as late responders (PLR). Among 11 multiparous cows, nine were early responders (MER), and the remaining two were late responders (MLR). Plasma concentration of thiobarbituric acid reactive substances (TBARS) in the PER were lower than those in the PLR (P < 0.01). The ratio of plasma all‐trans‐retinol to intake α‐tocopherol or β‐carotene were increased in the following order: MER < PER < PLR (P < 0.01). The milk lactose (P < 0.025) and plasma glucose (P < 0.01) of the early responders tended to be lower than those of the late responders. These may have been associated with the availability of vitamins or energy balance. Thus, we suggest the possibility that the cows which were able to utilize antioxidants and energy from the feed efficiently may have earlier resumption of ovaries postpartum.     

Phagocytic and bactericidal activity of blood and milk-resident neutrophils against Staphylococcus aureus in primiparous and multiparous cows during early lactation

To examine the effect of parity on polymorphonuclear neutrophils (PMN) function, phagocytic and bactericidal activity of the PMN isolated from blood and milk against Staphylococcus aureus was compared between groups of 6 primiparous and 6 multiparous healthy dairy cows during early lactation using bacteriological and PMN-pathogen interaction assays. Latex-stimulated luminol-amplified chemiluminescence (CL) and viability of these PMN were also investigated. The phagocytosis and killing of S. aureus by blood were remarkably higher than those of milk PMN. Similarly, the CL and viability in blood PMN were markedly higher than in milk PMN. Both in blood and in milk the phagocytosis of S. aureus by PMN in primiparous cows was substantially higher than in multiparous cows. The killing activity of blood PMN against S. aureus was 42.3+/-3.4% and 23.2+/-1.7% in primiparous and multiparous, respectively. Milk PMN killed only 20.7+/-2% S. aureus in primiparous and 10.2+/-1.3% in multiparous cows. Blood and milk PMN CL and milk PMN viability were significantly higher in primiparous cows. The pronounced reduction in phagocytic and bactericidal activity in blood and milk-resident PMN from multiparous cows, in part, resulted from the pronounced decrease of PMN viability and free radicals production capacity; this suggests that heifers' udders could be more protected against S. aureus, which remains to be tested in the field.     

饲粮粗蛋白质水平对中国荷斯坦奶牛产奶性能、氮利用及血液激素的影响

本试验旨在研究饲粮粗蛋白质（ＣＰ）水平对中国荷斯坦奶牛产奶性能、氮利用及血液激素的影响。采用重复 ４×４拉丁方设计,８头经产中国荷斯坦奶牛随机分为 ４个处理。４个处理的饲粮 ＣＰ水平分别为 １２．５６％、１３．９６％、１５．５３％和 １６．９３％。试验分为 ４个周期,每个周期１８ｄ。在 ４ｄ收集期内,全量收集粪、尿,每天测量产奶量、乳成分和干物质摄入量（ＤＭＩ）,并在收集期最后 １ｄ采集血样。结果表明：４个饲粮处理的 ＤＭＩ基本相同（Ｐ＞０．０５）;饲粮 ＣＰ水平１２．５６％的产奶量和能量校正奶（ＥＣＭ）明显低于饲粮 ＣＰ水平 １３．９６％至 １６．９３％（Ｐ＜０．０５）,饲粮 ＣＰ水平 １３．９６％至 １６．９３％的产奶量和 ＥＣＭ 基本相同,其中饲粮 ＣＰ水平 １３．９６％和１６．９３％的产奶量分别为２８．１８和２８．７２ｋｇ／ｄ,ＥＣＭ分别为３２．６４和３２．０４ｋｇ／ｄ;乳成分中仅乳蛋白率随着饲粮 ＣＰ水平增加而提高（Ｐ＜０．０５）;饲粮 ＣＰ水平 １２．５６％和 １３．９６％的乳氮效率明显高于饲粮 ＣＰ水平 １５．５３％和 １６．９３％（Ｐ＜０．０５或 Ｐ＜０．０１）;随着饲粮 ＣＰ水平的提高,尿氮排出量不断增加,乳氮排出量也缓慢上涨,体内氮沉积显著增加（Ｐ＜０．０５或 Ｐ＜０．０１）,只有饲粮 ＣＰ水平 １６．９３％的粪氮排出量明显增加（Ｐ＜０．０５）;饲粮 ＣＰ水平 １２．５６％的血液瘦素浓度最高（Ｐ＜０．０５）,催乳素（ＰＲＬ）、生长激素（ＧＨ）、胰岛素样生长因子 １（ＩＧＦ １）、血糖、非酯化脂肪酸（ＮＥＦＡ）和 β－羟丁酸（ＢＨＢＡ）浓度较高;而饲粮 ＣＰ水平 １６．９３％的血浆尿素氮（ＰＵＮ）浓度最高（Ｐ＜０．０１）,胰岛素和 ＧＨ浓度较高,ＩＧＦ １浓度较低。由此可见,饲粮 ＣＰ水平１３．９６％适合中国荷斯坦奶牛产奶量２８ｋｇ／ｄ或 ＥＣＭ３２ｋｇ／ｄ的泌乳性能、氮利用和内分泌调节。     

酶制剂对泌乳前期奶牛产奶量和乳成分的影响

选择年龄、胎次、产奶量和泌乳时间相近的30头泌乳前期荷斯坦牛,随机分为3组(试验Ⅰ组、Ⅱ组和对照组),每组10头。在试验组精料补充料中添加300g/t和600g/t的非淀粉多糖酶制剂,研究其对奶牛产奶量和乳成分的影响。结果表明,与对照组相比,试验Ⅰ、Ⅱ组奶牛产奶量分别提高了1.18kg/d和1.23kg/d,乳脂率分别提高了0.03和0.39个百分点,乳蛋白率分别提高了0.01和0.05个百分点,体细胞数分别下降15.86万个/mL和14.63万个/mL,但差异均不显著(P>0.05);在泌乳前期的奶牛日粮中添加外源非淀粉多糖酶制剂具有促进奶牛泌乳、改善乳成分的趋势。     

酶菌复合制剂对奶牛生产性能和体细胞数的影响

本试验旨在研究酶菌复合制剂对奶牛生产性能和体细胞数的影响。选取年龄、胎次、泌乳天数及生理性状相近的荷斯坦奶牛240头,随机为成4组,每组6个重复,每个重复10头牛。对照组饲喂基础日粮,试验Ⅰ、Ⅱ和Ⅲ组分别在基础日粮中添加0.5、1.0和1.5 kg/t的酶菌复合制剂,预试期10 d,正试期40 d,分别于试验第10、20、30、40天采集牛粪便,利用粪便分析筛对牛粪便组成进行分析。分别在试验第1、20、40天采集乳样,采用乳汁分析仪测定各组乳样中乳脂率、乳蛋白率、非脂固形物和奶中体细胞数（SCC）,试验期间记录每头牛平均日产奶量（ADMY）及平均日采食量（ADFI）。试验结果表明,添加酶菌复合制剂能够显著增加奶牛平均日产奶量（P<0.05）,提高牛乳中乳蛋白和乳脂肪含量（P<0.05）,降低体细胞数（P<0.05）,改善粪便结构。综合试验结果,酶菌复合制剂应用于奶牛养殖的最优添加量为1.0 kg/t,可以提高奶牛产奶量,降低牛体细胞数。