Effect of climate factors on conception rate of lactating dairy cows in Mexico

The purpose of this study was to investigate the relationship between conception rate (CR) and climate variables. Data consisted of 24,380 inseminations of Holstein dairy herd in Hidalgo, Mexico. Weather records, including daily temperature (T), relative humidity (RH), rainfall, wind speed, and solar radiation, were obtained from a nearby weather station. Means for each climatic variable from 2 days before artificial insemination (AI) to the AI day were calculated for each conception date represented in the study. A significant negative correlation was observed between the CR and mean and minimum T, mean and minimum RH, mean and minimum temperature–humidity index (THI), and rainfall. The overall mean CR was 34.3%. The CR in lactating dairy cows followed a seasonal pattern, lower CRs were observed in summer months than during winter (32.1% vs. 36.9%; P < 0.01). The variables that had the greatest influence on CR were minimum and maximum T, minimum RH, minimum THI, wind speed, and rainfall.     

热应激下奶牛体温、呼吸频率与环境温湿指数的相关性研究

选择4头中国荷斯坦泌乳奶牛,采用全混合日粮进行饲喂,研究热应激条件下泌乳奶牛体温、呼吸频率与环境温湿指数的相关性。结果表明:热应激条件下泌乳奶牛体温、呼吸频率与环境温湿指数呈正相关,环境温湿指数对奶牛的体温、呼吸频率的影响显著(P0.01)。     

Onset and duration of luteal activity postpartum and their effect on first insemination conception rate in lactating dairy cows

The incidence of different types of luteal activity postpartum and their effect on reproductive performance were studied in 21 postpartum dairy cows. Progesterone concentrations in defatted milk collected 3 times a week were determined by EIA. Reproductive tract examination was undertaken every other week postpartum. Body weight and body condition score (BCS) were measured before and after calving and the average 100-day milk yield was calculated. Nine (42.9%) cows had normal ovarian activity (first luteal activity < or = 50 days postpartum followed by regular cycles), 5 (23.8%) had prolonged luteal phase (PLP; ovarian cycle with luteal activity > or = 20 days pre-service) and in 7 (33.3%) cows the first luteal activity was shown later than 50 days postpartum (DOV). When compared with normal cows, both PLP and DOV had longer interval to first insemination (63.1 +/- 22.0 days versus 77.6 +/- 21.6 and 93.0 +/- 22.3 days, P<0.05 and P<0.01, respectively), lower first insemination conception rate (88.9% versus 0.0% and 57.1%, P<0.01 and P<0.05, respectively) and greater BCS loss (0.81 +/- 0.2 versus 1.05 +/- 0.21 and 1.04 +/- 0.10, respectively, P<0.01). Cows with PLP showed longer interval to uterine involution than normal and DOV groups (54.0 +/- 8.3 days versus 42.4 +/- 5.5 and 43.3 +/- 8.3 days, respectively, P<0.01) and higher 100-day milk yield (38.8 +/- 2.7 kg versus 33.6 +/- 4.7 and 29.9 +/- 6.1 kg, respectively, P<0.01). In conclusion, more than half of the cows had abnormal luteal activity postpartum, which adversely affected reproductive performance.     

四川奶牛温湿指数研究

本文通过收集宣汉、金堂和洪雅县的气象资料,研究分析了四川奶牛主要养殖区域的温湿指数.结果表明,四川奶牛热应激大多属于温和应激,中等程度的热应激仅在6、7、8三个月间断性出现,没有严重和致死程度的热应激.热应激从5月份开始出现,至少到9月底才结束.总体来看,4月和9月的热应激不具有连续性,而6、7、8三个月的热应激有连续性.     

Circadian and ultradian rhythms of body temperature and peripheral concentrations of insulin and nitrogen in lactating dairy cows

To investigate possible circadian and ultradian periodicities for peripheral insulin and urea in lactating dairy cows, integrated 15-min blood samples were taken sequentially over 48 hr from six cows. In addition, radiotelemetry measurements of body temperature were averaged over the same 15-min periods. Cows were housed in an environmental chamber at 19 degrees C with lights on 0700 to 2300 hr; fed daily at 0900 hr; and milked at 0800 and 2000 hr. For five of the six cows, body temperature showed a circadian rhythm peaking at 2323 hr with an amplitude of 0.34 degree C. For the sixth cow, body temperature was 180 degrees out-of-phase, peaking at 1230 hr with an amplitude of 0.12 degree C. Circadian rhythms for insulin and urea were consistent for all six cows peaking at 1743 hr with an amplitude of 0.74 ng/ml for insulin and at 1034 hr with an amplitude of 3.83 mM for urea. Body temperature and insulin also displayed episodic increases that often exceeded the amplitudes of circadian rhythms. For body temperature, a broad increase in spectral power was seen for periods between 100 and 175 min; time intervals between peaks averaged around 100 min. For insulin, power spectra for individual cows universally indicated rhythms with periods of approximately 45 and 80 min; time intervals between peaks averaged approximately 65 min. For urea, almost all spectral energy was confined to the 24-hr rhythm, although there was evidence of a low-amplitude, 60-min rhythm. In conclusion, when animals are acclimated to a rigidly controlled environment and frequent blood sampling is accomplished with minimal intervention, it is possible to detect rhythms inherent in the regulation of metabolic variables.     

Effect of carbohydrate source on ammonia utilization in lactating dairy cows

This study was conducted to investigate the effect of dextrose, starch, NDF, and a carbohydrate (CHO) mix on utilization of ruminal ammonia in dairy cows. Four ruminally and duodenally cannulated Holstein cows (BW = 788 +/- 31 kg; 217 +/- 35 d in milk) were allocated to four treatments in a 4 x 4 Latin square design trial. Cows were fed an all alfalfa diet at 12-h intervals (DMI = 22.2 +/- 0.25 kg/d). Treatments were control, white oat fiber (NDF); corn dextrose (GLU); cornstarch (STA); and a CHO mix (25% of each): apple pectin, GLU, STA, and NDF (MIX). Carbohydrates were introduced intraruminally during feeding at 20% of dietary DMI. Ruminal ammonia was labeled with (15)N. Ruminal pH was the highest for NDF followed by STA and MIX and GLU (P < 0.001). Ruminal ammonia concentration and pool size were decreased by GLU and STA compared with NDF (P < 0.001 and P = 0.03, respectively). Acetate, isobutyrate, isovalerate, and total VFA concentration in the rumen were decreased (P = 0.009 to 0.001), and butyrate was increased (P < 0.001) by GLU compared with the other CHO. Microbial N flow to the duodenum was decreased (P < 0.05) by NDF compared with the other CHO, and the flow of microbial N formed from ammonia was greater for STA compared with GLU and NDF (P = 0.04 and 0.03, respectively). Urinary N loss was decreased (P = 0.05) by GLU and STA, but overall (feces plus urine) N losses were not affected (P = 0.73) by treatment. Milk urea concentration was lowered by GLU and STA compared with NDF and MIX (P = 0.002). The proportion of bacterial N synthesized from ammonia in the rumen was greater with STA than with NDF and MIX and was least for GLU (P = 0.02). Irreversible ammonia loss and flux were lower (P = 0.09 and 0.02, respectively) for GLU than for STA and NDF. As a percentage of the dose given, cumulative secretion of (15)N ammonia in milk protein was greater for STA than for GLU or NDF (P = 0.01 and 0.001, respectively). This experiment demonstrated that provision of readily fermentable energy can decrease ammonia concentrations in the rumen through decreased ammonia production (GLU), or through enhanced uptake of ammonia for microbial protein synthesis (STA). Rapidly fermentable energy in the rumen decreased ammonia production and flux, but the overall efficiency of ammonia utilization for milk protein synthesis was only increased by enhancing ruminal microbial ammonia uptake.     

Effect of fasting on plasma metabolites and hormones in lactating dairy cows

Metabolic and pathophysiologic changes of secondary ketosis were studied. Plasma samples were obtained from a group of 8 mature, lactating dairy cows before, during, and after a 48-hour fast. These samples were analyzed for glucose, free fatty acids (FFA), lactic acid, ketone bodies, glucocorticoids, insulin, and growth hormone concentrations. In the prefasting period, metabolites and hormones remained constant. Lactic acid and glucocorticoids also remained stable during the entire experiment, except on the 1st day after termination of the fast, when glucocorticoids increased significantly (P less than 0.05). Glucose values decreased significantly (P less than 0.01) with the onset of fasting, began to rise halfway through the fast, and were elevated following termination of the fast. Plasma glucose concentration returned to normal by the end of the experiment. Plasma FFA concentrations increased during the early portions of the fast and decreased thereafter. Plasma ketone body concentration responded similarly, but the change occurred approximately 12 hours after the plasma FFA changes. A value determined as ketotic was reached during the fast (14.6 +/- 1.3 mg/dl). Insulin concentrations remained low during the fast and increased after fasting. Plasma growth hormone concentration increased to a new plateau in response to fasting and then decreased somewhate after fasting was ended.     

注射国产LRH-A对产后母牛卵巢活动、发情和受胎的作用

<正> 引言 促性腺激素释放激素(GnRH)是下丘脑神经内分泌细胞分泌的一种释放激素。由于本身结构和功能上的特点,自七十年代初人工合成后,GnRH及其类似物被广泛用于牛繁殖的研究和生产中。国外有报道认为GnRH有促进产后母牛发情周期恢复,缩短产后空怀天数等作用。国内用LRH-A提早牦牛产后发情和受胎收到良好效果。     

Relationships between the conception rate of estrus synchronization using estradiol benzoate and CIDR (progesterone) and other parameters in holstein lactating dairy cows

The purpose of this study was to determine the relationships between conception rate and other parameters before estrus synchronization with a Controlled Internal Drug Release Device (CIDR) and estradiol benzoate (EB). In the estrus synchronization program, animals were injected with 2 mg EB and then received a CIDR. Seven days later, the CIDR was removed and the animals were given an injection of Prostaglandin F(2alpha). Twenty-four hours later, they received an injection of 1 mg EB, and they were artificially inseminated 24 h after that. This program was applied to 258 Holstein cows in Tohoku-machi (Aomori, Japan). Blood was collected at the beginning of the program, and the conception rate was determined about 40 days after insemination. The relationships among conception rate, blood biochemical values, age, body condition score and days in milk were statistically analyzed to determine better conditions for cow conception. The conception rate of the cows in the high progesterone group (more than 1 ng/ml, P(4)+) was significantly higher than that of the low progesterone group (less than 1 ng/ml, P(4)-; 47.9% vs. 28.6% P<0.01). In the P(4)- groups, the serum phospholipid level was significantly higher in the conception group than in the non-conception group, and the same tendency was seen in the P(4)+ groups. Blood urea nitrogen (BUN), albumin (Alb), and total cholesterol (TChol) were significantly higher in the conception group compared with the non-conception group, but no with P(4) was observed. We concluded that 1) the conception rate of the P(4)- group was remarkably low, that 2) the low conception rate and low P(4) level was related to a low PL level and that 3) BUN, Alb and TChol were higher in the conception group, although no relation with P(4) was found.     

Pharmacokinetics of sulphadiazine-trimethoprim in lactating dairy cows

Five Finnish Ayrshire cows in mid or end-lactation were treated with 40 mg sulphadiazine/kg and 8 mg trimethoprim/kg using intravenous (i.v.), intramuscular (i.m.) and subcutaneous (s.c.) routes. Elimination of sulphadiazine was not affected by the route of administration (median t1/2 4.4-5.0 h) while elimination of trimethoprim was strongly limited by slow absorption from the injection site after s.c. and i.m. administration (median for apparent t1/2 21-25 h) compared to that after i.v. administration (median t1/2 1.2 h; p < 0.05). The median bioavailability of trimethoprim was also decreased, being 37% and 55% after s.c. and i.m. administration, respectively. When i.v. administration was used, trimethoprim concentration exceeded 0.1 mg/l in milk between 0.15-8 h while sulphadiazine concentrations above 2 mg/l were maintained from 0.5-2 h to 8 h. After s.c. and i.m. administration sulphadiazine in milk behaved similar to that after i.v. administration, while trimethoprim time-concentration curves were flat and trimethoprim concentrations were around 0.1 mg/l for an extended period of time (8-12 h). Median Cmax values in milk were only 0.07 mg/l and 0.10 mg/l for s.c. and i.m. administrations, respectively. After s.c. administration, 4 out of 5 cows showed signs of pain. After i.m. administration, 2 of the cows showed clear signs of pain and one had some local tenderness at the site of injection.     

Milking frequency affects the circadian body temperature rhythm in dairy cows

The objective of this study was to investigate milking frequency as a potential stressor in Holstein–Friesian dairy cows managed in a pastoral farming system. The circadian body (vaginal) temperature rhythm was measured in cows milked twice-a-day (2x) or once-a-day (1x) in two experiments. The first experiment was conducted at peak lactation (50 ± 11 days in milk, DIM) and the second in response to a transition from 2x to 1x milking at mid-lactation (153 ± 21 DIM). At peak lactation, body temperature was continuously recorded for seven days in 40 dairy cows, milked either 2x (two groups, n = 10 per group) or 1x (two groups, n = 10 per group) from the time of calving. At mid-lactation, 60 dairy cows were milked either 2x (four groups, n = 5 per group), 1x (four groups, n = 5 per group) or switched from 2x to 1x on the afternoon of 156 DIM (2x:1x, four groups, n = 5 per group). Body temperature was measured in three of the five cows per group (36 cows in total) for 10 days from 153 to 162 DIM. Milk yield and total grazing time (Experiment 2 only) were recorded in all cows. At peak lactation cows milked 2x had a higher (P ≤ 0.051) mean body temperature between 1600 and 0000 h than 1x cows (38.6 vs. 38.4 °C; SED = 0.03 °C). At mid-lactation, mean body temperature was also elevated between 1600 and 2000 h in 2x cows compared to 1x cows (2x: 38.6 °C, 1x:38.4 °C, SED = 0.04 °C; P < 0.001) and tended (P = 0.083) to be higher in 2x cows between 2000 and 0000 h. On the day the milking frequency was switched from 2x to 1x (156 DIM), mean body temperature still tended to be higher (P = 0.087) between 1600 and 2000 h in cows continuing on 2x compared with 2x:1x and 1x cows. Body temperature in 2x:1x cows on 157 DIM was lower than 2x cows and similar to that of 1x cows, but there was no consistent effect of milking frequency on body temperature from 158 to 162 DIM. Cows milked 2x had a higher daily milk yield than 1x cows at peak lactation and at mid-lactation (peak lactation 2x: 28.1 ± 5.1, 1x: 24.5 ± 4.7 kg milk per day). Time spent grazing between 1600 and 2000 h was initially at least 22 min higher (P = 0.031) in 1x cows than in 2x:1x and 2x cows on 153 DIM but there were no differences (P ≥ 0.107) in the remaining days of the trial. Milk yield in 2x:1x cows declined rapidly on 156 DIM to be lower (P < 0.001) than both 2x and 1x cows but from 157 DIM began to follow the same pattern as 1x cows. In conclusion, milking frequency had an effect on the circadian body temperature rhythm, particularly in the late afternoon and evening. There was a decline in body temperature from 1600 h if milking frequency was reduced, but this change was not explained by treatment differences in time spent grazing during the same period. The alterations in the circadian body temperature rhythm with milking frequency were likely due to differences in metabolic activity and internal heat production associated with locomotor activity and relative milk production rather than physiological stress per se.     

饲粮中添加莫能菌素对奶牛瘤胃发酵参数的影响

选取泌乳期奶牛12头,采用重复4×4拉丁方试验设计,对照组饲喂基础饲粮(A组),试验组分别在基础饲粮的基础上添加300(B组)、400(C组)、500(D组)mg/(头·d)莫能菌素,探讨饲粮中添加不同水平的莫能菌素对奶牛瘤胃发酵相关参数的影响。结果表明,饲粮中添加莫能菌素可提高瘤胃液pH值,显著降低瘤胃液微生物蛋白(MCP)、总挥发性脂肪酸(T-VFA)、乙酸含量以及乙酸/丙酸的值,增加丙酸含量(P0.05),对氨态氮(NH3-N)和丁酸没有显著性影响(P0.05);C组较对照组T-VFA和乙酸的降低程度最大,分别降低了22.71%和28.59%(P0.05);D组的MCP和乙酸/丙酸值较对照组降低程度最大,分别降低了33.99%和31.15%(P0.05;D组中丙酸的含量增加最多为9.63%(P0.05)。综上所述,奶牛饲喂400~500mg/(头·d)的莫能菌素更有利于促进瘤胃内丙酸型发酵。     

不同豆粕添加量的日粮对奶牛产奶性能的影响

将40头荷斯坦产奶牛随机分为4个试验组,每组10头。4种试验日粮均配制成蛋白质(CP)含量15.2%、产奶净能(NEL)6.90~7.06 MJ/kg。日粮通过调节豆粕和棉籽粕的用量改变日粮赖氨酸(Lys)含量,这样试验1组日粮赖氨酸含量为0.65%、试验2组0.62%、试验3组0.59%和试验4组0.56%。所有试验奶牛先饲喂10 d试验日粮作为预试期,然后开始70 d正试期。试验1组产奶量最高,平均为(27.13±1.53)kg/d;试验4组产奶量最低,平均为(24.40±1.56)kg/d;试验2组和3组依次为(26.18±1.37)和(25.27±1.58)kg/d;其中试验1组产奶量明显高于试验3组(P<0.01)和试验4组(P<0.01),试验2组明显高于试验4组(P<0.05)。因此,在日粮蛋白质含量保持相同和产奶净能相近的条件下,提高日粮赖氨酸含量则提高了奶牛产奶量,降低日粮赖氨酸含量则降低了奶牛产奶量;大量使用棉籽粕替代豆粕降低日粮赖氨酸含量,导致产奶量降低;尽管日粮赖氨酸含量容易提高奶牛日粮成本,由于提高产奶量,增加了产奶纯收入。使用日粮赖氨酸含量这一指标有利于评价奶牛产奶量、乳成分和经济效益。     

Effect of extruded linseed on productive and reproductive performance of lactating dairy cows

A total of 356 early lactation multiparous Holstein cows were used in a randomized complete block design to determine the effects of feeding extruded linseed on milk production and composition, and reproductive performance. Forty of these cows were randomly selected to study the effects of extruded linseed on milk fatty acid (FA) profile, individual feed intake and prostaglandin secretion. Cows were fed a 40:60 forage to concentrate ratio diet (17.9% CP, 27.7% NDF and 6.0% EE) ad libitum that was similar in composition between treatments except for the protein supplements that differed and were control (CTR: 4.9% extruded soybean) and linseed (LIN: 5.5% extruded linseed). Individual DM intake measured at 40 (23.0 kg/d) and 90 (24.2 kg/d) days in milk, and milk yield (45.0 kg/d) were not affected by treatment, but the lower (P < 0.05) milk fat percentage in cows fed LIN (2.65%) compared with CTR (2.86%) resulted in lower (P < 0.05) 4.0% fat-corrected milk yield for cows fed LIN (35.4 kg/d) compared with CTR (37.7 kg/d). Milk protein content was higher (P < 0.05) in LIN (3.04%) than in CTR (3.00%). The concentration of saturated FA was lower (P < 0.05) in milk fat from LIN (56.2%) compared with CTR (60.2%). Monounsaturated FA (35.7 vs. 32.7%) and polyunsaturated FA (8.0 vs. 6.9%) were higher in LIN (P < 0.05) than in CTR. Supplementation with LIN also increased (P < 0.05) the proportion of vaccenic acid (2.21 vs. 1.55%), total conjugated linoleic acid (0.91 vs. 0.72%) and n-3 FA (1.21 vs. 0.54%) in milk compared with CTR. Plasma concentrations of prostaglandin metabolite were numerically lower in LIN (106 pg/ml) compared with CTR (120 pg/ml) (P = 0.16) but reproductive performance was similar between treatments. In summary, extruded linseed reduced milk fat percentage and 4.0% fat-corrected milk yield and increased milk protein percentage and the content of healthy FA in milk without modifying DM intake, milk yield and reproductive performance.     

Effects of high ambient temperature on urea‐nitrogen recycling in lactating dairy cows

Effects of exposure to hot environment on urea metabolism were studied in lactating Holstein cows. Four cows were fed ad libitum a total mixed ration and housed in a temperature‐controlled chamber at constant moderate (18°C) or high (28°C) ambient temperatures in a cross‐over design. Urea nitrogen (N) kinetics was measured by determining urea isotopomer in urine after single injection of [¹⁵N₂]urea into the jugular vein. Both dry matter intake and milk yield were decreased under high ambient temperature. Intakes of total N and digestible N were decreased under high ambient temperature but urinary urea‐N excretion was increased. The ratio of urea‐N production to digestible N was increased, whereas the proportion of gut urea‐N entry to urea‐N production tended to be decreased under high ambient temperature. Neither return to the ornithine cycle, anabolic use nor fecal excretion of urea‐N recycled to the gut was affected by ambient temperature. Under high ambient temperature, renal clearance of plasma urea was not affected but the gut clearance was decreased. Increase of urea‐N production and reduction of gut urea‐N entry, in relative terms, were associated with increased urinary urea‐N excretion of lactating dairy cows in higher thermal environments.     

Pharmacokinetics of sodium cephapirin in lactating dairy cows

Sodium cephapirin was administered (10 mg/kg of body weight, IM) at 8-hour intervals in 4 consecutive doses to each of 6 lactating dairy cows. Blood, normal milk, mastitic milk, urine, and endometrial tissue samples were collected serially. Mean peak cephapirin concentrations in serum were 13.3 micrograms/ml 10 minutes after the 1st injection and were 15.8 micrograms/ml 20 minutes after the 4th injection (post[initial]injection hour [PIH] 24.33). The overall elimination rate constant value was 0.66/h and plasma clearance was 760 ml/h/kg. Mean peak cephapirin concentration in normal milk was 0.11 microgram/ml at PIH 2 and mean peak cephapirin concentration in mastitic milk was 0.18 microgram/ml at PIH 4. Cephapirin was not detected in the endometrium. The highest concentration of cephapirin in urine was 452 micrograms/ml, 2 hours after the 4th dose (PIH 26).     

Effect of subluteal concentrations of progesterone on luteinizing hormone and ovulation in lactating dairy cows

Two experiments were conducted to determine if administration of progesterone within a low, subluteal range (0.1-1.0 ng/mL) blocks the luteinizing hormone (LH) surge (experiments 1 and 2) and ovulation (experiment 2) in lactating dairy cows. In experiment 1, progesterone was administered to cycling, lactating dairy cows during the luteal phase of the estrous cycle using a controlled internal drug release (CIDR) device. CIDRs were pre-incubated in other cows for either 0 (CIDR-0), 14 (CIDR-14) or 28 days (CIDR-28). One group of cows received no CIDRs and served as controls. One day after CIDR insertion, luteolysis was induced by two injections of prostaglandin (PG) F(2alpha) (25 mg) at 12 h intervals. Two days after the first injection, estradiol cypionate (ECP; 3 mg) was injected to induce a LH surge. Concentrations of progesterone after luteolysis were 0.11, 0.45, 0.78 and 1.20 ng/mL for cows treated with no CIDR, CIDR-28, CIDR-14, and CIDR-0, respectively. LH surges were detected in 4/4 controls, 4/5 CIDR-28, 2/5 CIDR-14 and 0/5 CIDR-0 cows following ECP. In experiment 2, progesterone was administered to cycling, lactating, Holstein cows during the luteal phase of the estrous cycle as in experiment 1. Luteolysis was induced as in experiment 1. The occurrence of an endogenous LH surge and ovulation were monitored for 7 days. Concentrations of progesterone after luteolysis were 0.13, 0.30, 0.70 and 1.20 ng/mL for cows treated with no CIDR, CIDR-28, CIDR-14 and CIDR-0, respectively. LH surges and ovulation were detected in 5/5 controls, 3/7 CIDR-28, 0/5 CIDR-14 and 0/5 CIDR-0 cows. It was concluded that low concentrations of progesterone can reduce the ability of either endogenous or exogenous estradiol to induce a preovulatory surge of LH and ovulation.