A farming systems study of abortion in dairy cattle on the Atherton Tableland: 4. Pasture composition and plasma progesterone concentrations of pregnant cows in affected herds

To provide more evidence for an apparent association between immature, high protein pasture diets and abortion in dairy cows on the Atherton Tableland in tropical north Queensland, pastures and cows on 4 farms were sampled on 5 occasions during a 7-month period. Pasture samples were analysed for dry matter (DM), protein, nitrate and fibre content. Plasma progesterone concentrations were determined in 18 to 20 pregnant cows. Fifty-four pasture samples (38 grass and 16 legume) were analysed and the distribution for 3 DM ranges was: 10% to 14.9% - 20 samples, 15% to 19.9% - 27 samples and 20% to 24.9% - 7 samples, while the distribution for 4 protein ranges was: 15% to 19% - 5 samples, 20% to 24% - 20 samples, 25% to 29% - 21 samples and 30% to 34% - 8 samples. Both pasture protein and DM content fluctuated with time. Pasture nitrate was low and insignificant while fibre (cell wall) levels appeared to be satisfactory for ruminant nutrition. Significant differences occurred between the mean plasma progesterone levels on 3 of the 4 farms. Raised levels in pregnant cows suggested the possibility of increased progesterone production in response to a previous low progesterone crisis or, alternatively, a decreased metabolic clearance rate of progesterone in pregnant cows on a declining plane of nutrition towards the end of the summer wet season. Progesterone data were not available from cows which previously aborted.(ABSTRACT TRUNCATED AT 250 WORDS)     

A farming systems study of abortion in dairy cattle on the Atherton Tableland: 3. Metabolic factors

An association with a rank correlation of 0.55 (p = 0.06) was obtained between monthly rainfall and monthly abortions for a group of 24 farms in tropical Australia where cows grazed predominantly summer rain-dependent pasture. A similar association was found among cows grazing nitrogen-fertilised, irrigated pasture in winter in the same area. On farms with irrigated pasture the first service conception and abortion rates in herds which grazed intensively during the night (abortion 8.9%; first service conception 42.9%) differed significantly from those which grazed during the day (abortion 6.4%; first service conception 52.9%), and this suggested that increased abortion rates and decreased first conception rates may be part of the one syndrome. An hypothesis was developed that the feeding of immature nitrogen-fertilised pasture, rich in protein and stimulated by rain or irrigation, is associated with an increased abortion rate and a depressed conception rate. Other evidence included an increased susceptibility of first lactation cows to abortion, a lower abortion rate in late pregnant dry cows fed more mature pasture, a 20% repeat abortion rate in the population sampled and the lack of conclusive evidence for infectious and selected non-infectious agents. There were no other observed clinical signs in most aborting cows.     

A farming systems study of abortion in dairy cattle on the Atherton Tableland: I. Reproductive performance

Herd health records from 1983 to 1985 were analysed for a sample of 19 dairy farms on the Atherton Tableland in tropical north Queensland. Abortion and first service conception rates were calculated for each farm for each year. The association between abortion rate and stage of gestation at pregnancy diagnosis was investigated as well as the association between abortion rate and lactation status. There was a significant linear increase in abortion rate over the 3-year period, during which the mean rate was 7.3 +/- 2.1% (range 4.5% to 10.9%). There was also a significant variation in first conception rates during the same period, when the mean first service conception rate was 51.8% +/- 6.6% (range 42.4% to 65.8%). A significantly higher abortion rate was recorded in first lactation cows. Of 178 abortions in all lactation groups (1984), 20.3% were repeat abortions by the same cows. Of 163 abortions, a majority (80.4%) occurred during months 3 to 7 of gestation. No significant association was found between the timing of pregnancy diagnosis and occurrence of abortion.     

A farming systems study of abortion in dairy cattle on the Atherton Tableland: 2. The pattern of infectious diseases

The role of infectious agents on dairy farms on the Atherton Tableland in tropical north Queensland was studied as part of a comprehensive investigation into the causes of bovine abortion. The prevalence of antibody in serums collected from 7 herds whose annual abortion rates ranged from 3% to 21% were as follows: Leptospira hardjo 49.9% (426/853), L. pomona 0.4% (3/851), bovine virus diarrhoea (BVD) 33.7% (35/104). Infectious bovine rhinotracheitis virus (IBR) 11.5% (12/105), Akabane virus 92.2% (95/103), Aino virus 62.1% (64/103), Chlamydia psittaci 3.1% (37/1004), Brucella abortus 0% (0/851), and Toxoplasma gondii 0% (0/105). Testing of serums against a wide range of leptospiral serotypes indicated that reactions occurring in the Hebdomadis and Sejroe serogroups were probably cross reactions with L. hardjo. Infection with L. hardjo and Akabane virus occurred prior to first mating and contact with Aino virus occurred during first pregnancy. Infection with BVD and IBR viruses was sporadic. The pathology and microbiology of 32 aborted foetuses from 24 Tableland herds (10 from the group of 19 farms under more intense study) were performed. Lesions associated with a Sarcocystis-like agent were present in 6, leptospires in 1, suspected toxic hepatosis in 2 and purulent bronchopneumonia (Staphylococcus aureus) in 1 foetus. No diagnoses were made in the remaining 22 foetuses (69%). Evidence for a common infectious cause of abortion in the population was inconclusive.     

The association between lameness and fertility in dairy cows

One thousand, four hundred and ninety-one lactations in 770 Friesian, Holstein and Ayrshire crossbred cows have been used to study the associations between lameness and fertility. Lameness was associated with a longer interval between calving and first service and a longer interval between calving and conception. The largest increases in these intervals, of 17 and 30 days, respectively, occurred in cows with either sole or white line lesions occurring between 36 and 70 days after calving. The conception rate during the 63 days before a diagnosis of lameness was made was lower (31 per cent) than at other times (40 per cent).     

Association between Chlamydia psittaci seropositivity and abortion in Italian dairy cows.

Although the seroprevalence of Chlamydia psittaci is widespread in Italian dairy herds, its role in inducing genital disorders has not been elucidated. We therefore set up a case-control study to compare seroprevalence to C. psittaci in an aborted-cow population and in a randomly selected control group in the province of Parma (the Po Valley of northern Italy). The true seroprevalence (45%) in aborted cows was significantly higher than that in the control group (24%) (adjusted odds ratio=2.53).     

Milk production and fatty acid profile of dairy cows grazing four grass species pastures during the rainy season in small-scale dairy systems in the highlands of Mexico

The study evaluated small-scale dairy systems with continuous grazing of pastures based on three temperate grasses festulolium (FL), tall fescue (TF), and perennial ryegrass (RG), compared with subtropical kikuyu grass (KG). All pastures were associated with white clover (Trifolium repens L.). Twelve multiparous Holstein cows were assigned to a 4?×?4 Latin square replicated three times with 14-day experimental periods. Sampling and analyses of pastures, concentrates, and animal variables followed standard procedures. FL showed a significantly (p?<?0.05) higher mean sward height, but there were no differences (p?>?0.05) in net herbage accumulation. There were significant differences (p?<?0.05) among pastures for CP, NDF, ADF, in vitro digestibility of OM (IVOMD), and estimated metabolizable energy (eME). There were no differences (p?>?0.05) between treatments for milk yield and composition, live weight, or body condition score. There were significant differences (p?<?0.05) in fatty acid values for pastures in C14:0, C16:1, and C18:3n3. There were significant differences between treatments (p?<?0.05) in milk contents for C18:0, C18:1t11, and C18:2c9t11. Grazing FL, TF, RG, or KY pastures showed no differences in milk yields. Higher values for C18:0, C18:1t11, and C18:2c9t11 were detected in KY, RG, and TF. RG had significantly higher MUFA than FL and higher PUFA than TF. A value under 65% of SFA, a ratio of n-6/n-3 lower than 4, and an atherogenic index of 1.7 are indicators of milk with beneficial effects for human health.     

An association between the level of oxidative stress and the concentrations of NEFA and BHBA in the plasma of ketotic dairy cows

The aim of this study was to evaluate the oxidative status in ketotic cows. We observed changes in the oxidative status and correlations between the oxidative and metabolic status in non‐ketotic (n = 10), subclinical ketotic (n = 10) and ketotic cows (n = 10). Plasma samples were analysed by standard biochemical techniques and ELISA to determine traditional metabolic parameters: triglyceride (TG), phosphonium (P), calcium (Ca), aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), total protein (TP), albumin (ALB), immune globulin (Ig), total cholesterol (TC), high‐density lipoprotein (HDL), very low‐density lipoprotein (VLDL) and lactate dehydrogenase (LDH); energy metabolism indices: glucose, β‐hydroxybutyrate (BHBA) and non‐esterified fatty acids (NEFA); and indices of oxidative status: malondialdehyde (MDA), hydrogen peroxide (H₂O₂), vitamin C, vitamin E, superoxide dismutase (SOD), glutathione peroxidase (GSH‐Px), catalase (CAT), xanthine oxidase (XOD) and total antioxidant capacity (TAOC). The results of this study showed that plasma glucose levels were lower in ketotic and subclinical ketotic cows than in non‐ketotic cows; however, the plasma NEFA and BHBA concentrations were higher. In addition, significant decreases in TC, HDL and VLDL and significant increases in AST, ALT and LDH were observed in the plasma of the ketotic cows. The ketotic cows showed decreased plasma SOD, CAT, vitamin C and vitamin E, inhibited hydroxyl radical capacity and increased plasma H₂O₂ and MDA. There were positive correlations between the plasma NEFA and ALT, AST, LDH and MDA and negative correlations between the plasma NEFA and TC, HDL, VLDL, SOD, vitamin C, vitamin E, 1542280 uric acid and inhibited hydroxyl radical capacity. In addition, there were positive correlations between BHBA concentrations and ALT, AST and LDH and negative correlations between plasma BHBA concentrations and TC, HDL, VLDL, vitamin E and inhibited hydroxyl radical capacity. Overall, ketotic dairy cows experience oxidative stress, which is presumably associated with hyperketonemia and higher NEFA.     

An association exists between bovine herpesvirus-4 seropositivity and abortion in cows

The prevalence of cattle seropositive to bovine herpesvirus-4 (BHV-4) is high in Belgium. In Belgian farms, clinical signs associated with BHV-4 infection essentially involve the genital tract and consist mainly of postpartum metritis or metroperitonitis. The role of BHV-4 in abortion has not been definitively demonstrated but epidemiological and experimental facts suggest its involvement. A seroepidemiological investigation was therefore conducted as a case-control study to compare the seroprevalences of BHV-4 infections in the aborted-cow population and in a randomly selected control group in the province of Liège (Belgium). The seroprevalence (17.2%) in aborted cows was significantly higher than that of the control group (10.0%). The odds ratio (OR) was 1.87 (1.06 < 3.30). BHV-4 infection is therefore considered as a risk factor for abortion in cows.     

奶牛衣原体性流产病原分离及血清学调查

应用实验室病原分离、血清学检测技术对宁夏某规模化奶牛场流产牛进行衣原体病原分离及血清学调查.结果表明,多年以来,在宁夏奶牛场中流行的以孕牛流产、早产、死产或产无活力弱犊的繁殖障碍性疾病与衣原体感染有关.采集四家规模化奶牛场380份血清,IHA试验结果牛群平均阳性率28.4%.     

奶牛血浆PGFM浓度变化与子宫内膜炎关系的研究

奶牛子宫内膜炎是奶牛产后多发性疾病之一，产后子宫感染是一种非特异性感染，主要的致病菌有分泌型化脓菌（Arcanobacterium pyogenes）、埃希氏大肠杆菌及其他多种革兰氏阴性厌氧菌。子宫内膜炎对奶牛业有重要的经济影响，若能早期识别出对子宫内膜炎易感性较高的奶牛，并提高对子宫内膜炎患牛的诊断率，将会明显的减少因产后子宫感染所带来的损失。     

Healing process of claw lesions in dairy cows in alpine mountain pastures

The field study investigated severity, localisation and incidence of claw lesions of dairy cows and their healing process during a period of three months on selected mountain pastures in the central part of Switzerland. In 60 cows, which were at least 120 days in their lactation, the healing process was compared with the biochemical profiles. In 141 cows 197 claw lesions were recorded. Diagnosed were only sole ulcers (38%) and white line lesions (62%). In the first and second half of the summer term, the number of claw lesions was equal, although more severe lesions occurred mainly during the second half (89%). The lesions were treated surgically and the affected claw was elevated on a wood block or a plastic shoe. Average time for formation of a close layer of horn was 14 days. A delayed healing process was observed in dairy cows with an milk yield over 5500 kg per lactation, as well as in the second half of the summer term. Cows with a delayed healing process had significantly higher concentrations of free fatty acids and beta-hydroxybutyrate, and higher plasma enzyme activities for AST than cows with adequate healing process. This indicates that cows with a relatively high milk production touch upon the limits of their physical capacity under harder conditions on alpine pastures, which may affect also the healing process of claw lesions.     

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 feeding non-fibrous carbohydrate before grazing on intake and nitrogen utilization in dairy cows throughout the grazing season

Ten lactating cows were used to determine the effect of feeding non-fibrous carbohydrate (NFC) supplement before grazing on feed intake and nitrogen (N) utilization throughout a grazing season. The experiment was conducted from June to September. Cows grazed twice a day (2.5 h × 2) under a set stocking system and were fed NFC supplement (1 kg/4 kg of milk yield) 2 h before grazing (PRE) or immediately after grazing (POST). Cows were also fed a grass and corn silage mixture ad libitum. Herbage dry matter intake (DMI) was greater for PRE than for POST throughout the experiment and decreased from June to September. Conversely, silage DMI was less for PRE than for POST throughout the experiment and increased over the grazing season. Consequently, total DMI for PRE did not differ from that for POST. Milk urea-N concentration and urinary urea-N excretion in June did not differ between the treatments, whereas that after July was higher for PRE than for POST. Proportion of urinary N excretion to absorbed N intake in June was lower for PRE than for POST, but that after July was higher for PRE than for POST. Feeding NFC supplement before grazing would improve N utilization when cows eat large amounts of herbage high in N.     

Relationship between blood selenium concentration or glutathione peroxidase activity, and milk selenium concentrations in New Zealand dairy cows

AIM: To determine the relationships between blood selenium (Se) concentrations or glutathione peroxidase activity (GSH-Px), and milk Se concentrations in dairy cows. METHODS: Seventy-two Friesian dairy cows were either untreated or injected with 0.5, 1.0 or 2.0 mg Se/kg liveweight as barium selenate (BaSeO4) formulations, resulting in 6 groups of animals with mean blood Se concentrations that varied from 212 to 2272 nmol/l. Milk samples were collected on Days 104 and 188, and blood samples were collected prior to treatment and on Days 41, 76, 104, 188, 244, and 292 after Se injection. RESULTS: Significant quadratic relationships between blood Se and milk Se concentrations, as well as blood GSH-Px activity and milk Se concentrations, were evident at Days 104 and 188. Using combined data, these were represented by the equations: milk Se = 27.3 + 0.073 blood Se -0.00001 (blood Se)2; R2=0.79, p<0.005, and; milk Se = 34.8 + 4.99 GSH-Px -0.068 (GSHPx)2; R2=0.79, p<0.005. CONCLUSIONS: The Se status of dairy cows can be assessed from milk Se concentrations. CLINICAL SIGNIFICANCE: Bulk-tank milk Se concentrations could be evaluated as a method to assess the Se status of dairy herds.     

Oat silage for grazing dairy cows in small-scale dairy systems in the highlands of central Mexico

The objective was to evaluate the provision of oat silage (Avena sativa) to supplement grazing dairy cows on pastures of perennial ryegrass (Lolium perenne), festulolium (Lolium multiflorum × Festuca pratense) and white clover (Trifolium repens) during the dry season when pasture growth is limited. The experimental design was a 3 × 3 Latin square replicated three times, with nine milking Holstein cows (mean live weight 496.2 ± 33.6 kg and daily milk yield 14.8 ± 2.8 kg cow^?1) under on-farm participatory rural research. Experimental periods were 14 d. Simulated grazing samples of pasture herbage were analysed for chemical composition, sward height recorded and net herbage accumulation determined from exclusion cages. Treatments were the inclusion of oat silage at T0 = 0 kg DM cow^?1 d^?1 of oat silage, T3 = 3 kg DM cow^?1 d^?1 of oat silage, and T6 = 6 kg DM cow^?1 d^?1 of oat silage, plus 5.0 kg fresh weight commercial concentrate and 9 h of continuous grazing. Animal variables were milk yield and composition, live weight and body condition score. Feeding costs were calculated. Mean milk yield was 18.9 ± 0.27 kg cow^?1 d^?1 with no differences in animal variables (p > 0.05), but feeding costs per kilogram milk increased 25% for T3 and 50% for T6. Oat silage supplementation is only viable under difficult grazing conditions.     

Effectiveness of calcium chloride in increasing blood calcium concentrations of periparturient dairy cows.

Calcium chloride supplements such as gels and drench were studied to determine their effectiveness for increasing blood serum Ca concentrations in periparturient dairy cows. Multiparous, pregnant Holstein dairy cows (n = 36) were assigned to one of four treatments. After calving, cows in four treatments received basal diet and two doses of either control inert gel (CON), gel containing CaCl2 and vitamins (CVG), gel containing CaCl2 and minerals (CMG), or CaCl2 as drench containing vitamins (CVD). The first dose was given within 2 h after calving and the second dose 12 h after the first dose. Each dose provided .07, 54.5, 56.0, and 33.2 g of elemental Ca in CON, CVG, CMG, and CVD treatments, respectively. Blood samples were collected at 0, 15, 30, 60, 180, and 360 min after each oral dose. The blood serum Ca concentrations were 6.26, 7.56, 6.20, and 5.96 mg/dL during the pretreatment period and deviated -13.5, 7.1, 9.3, and 18.1% from pretreatment levels at 18 h after the first dose in CON, CVG, CMG, and CVD treatments, respectively. The average changes in serum P from pretreatment levels were not different among treatments. Serum Mg concentrations remained below the pretreatment levels in all four treatments. Blood serum beta-hydroxybutyrate during the first 2 wk and milk yields during the first 4 wk of lactation were the same in all treatments. Three cases of clinical milk fever were observed in CON treatment and one case in CVD treatment. The oral supplements of CaCl2 as gel or drench increased the blood Ca levels in periparturient dairy cows. Increased supply of Ca through oral supplements of CaCl2 may prevent milk fever in cows that are marginally hypocalcemic.     

乳牛衣原体性流产的病原鉴定及免疫原性研究

对采自甘肃、陕西和宁夏奶牛场的发生不明原因流产乳牛病料进行了间接血凝试验（IHA）、PCR、病原分离鉴定和MOMP基因检测，证实病原为鹦鹉热衣原体（Chlamydia psittaci）。对分离株Sx5和Nx进行毒力稳定性和免疫原性测定，用鸡胚连传20代，SX5和NX株的毒力比较稳定，毒力效价分别为10^-11ELD50和10^-10ELD50；用这2株菌对小鼠和牛做免疫效力试验，结果显示，免疫鼠5／5和5／5保护，对照鼠0／5保护；免疫牛3／3和3／3保护，对照牛0／3保护。表明，SX5和NX株具有良好的免疫原性，可以作为疫苗研制的候选菌株。