Further studies on theophylline-induced hypocalcaemia in sheep.

The effects of various doses of theophylline on the plasma levels of calcium, inorganic phosphorus and magnesium were studied in sheep. The dose of 0.25 mg/kg/min. during 40 min. produced a hypocalcaemia, which was abolished by thyroidectomy. At a higher dose, 1.0 mg/kg/min., thyroidectomy reduced, but did not block, the hypocalcaemic effect of theophylline. Young sheep showed a greater calcium response than did adult ewes. The decrease in plasma calcium was in no case accompanied by hypophosphataemia. Plasma magnesium decreased in all groups after 1.0 mg/kg/min. and was not influenced by thyroidectomy. Theophylline increased the urinary excretion of calcium and magnesium. It is concluded that theophylline-induced hypocalcaemia in sheep is in part a result of increased calcitonin secretion but that also other mechanisms must be involved, e. g. a direct effect of theophylline on bone.     

Protein expression in dairy cows with and without subclinical hypocalcaemia

AIM: To determine differences in plasma proteomic profiles between healthy cows and those with subclinical hypocalcaemia within 12 hours after calving, and thereby explore the underlying biological mechanism of subclinical hypocalcaemia in dairy cows.

METHODS: Plasma samples were collected within 6 hours of calving from Holstein cows on a farm in Heilongjiang, China; 32 with subclinical hypocalcaemia (plasma calcium concentration 1.38–2.00?mmol/L and no clinical signs) and 59 control cows (plasma calcium concentration 2.10–2.8?mmol/L). Plasma samples were applied to weak cationic exchange protein chips for protein profiling by surface-enhanced laser desorption/ionisation time-of-flight mass spectrometry (SELDI-TOF-MS), and the data were analysed using the PBS-IIC system. The amplitude of peaks for the two groups were compared using the Wilcoxon sum-rank test, and the mass-to-charge ratio of the peaks that differed was used to identify peptide fragments using the Swiss-Prot protein database.

RESULTS: Seven peaks were identified in the subclinical hypocalcaemia group that differed from those of the control group (p<0.001), that represented six unique proteins. Expression of serum albumin, fibrinogen alpha chain, amyloid beta A4 proteins and neurosecretory protein VGF were increased, and expression of apolipoprotein A-II and serum amyloid A proteins were decreased in the subclinical hypocalcaemic cows compared with control cows.

CONCLUSION: Use of SELDI-TOF-MS technology can effectively identify differences in plasma protein expression patterns in cows with subclinical hypocalcaemia. Neurosecretory protein VGF and amyloid beta A4 protein might represent useful biomarkers for diagnosis of subclinical hypocalcaemia.     

"特高"黑麦草饲喂泌乳牛试验

“特高”为四倍体一年生黑麦草，1998年从百绿集团引进。通过15d的奶牛饲喂试验，结果表明：在相同的精饲料供给条件下，日饲喂特高黑麦草(50kg／头)的奶牛日产奶2．4kg，比日饲喂青贮玉米(30kg／头) 野杂草(15kg／头)的奶牛高o．4kg，而每公斤牛奶的饲喂成本却降低了0．17元，效益显著。另外，试验中还发现，饲喂黑麦草特高能有效地减少奶牛乳房炎等病症。     

铜在奶牛生产中的应用及存在问题

本文就铜的生物学效应和生理功能,奶牛对铜的需要量、耐受量和中毒量等进行阐述。     

Effect of several doses of zeolite A on feed intake,energy metabolism and on mineral metabolism in dairy cows around calving

The object of the present study was to determine the influence of different zeolite A doses on dry matter intake (DMI) and mineral metabolism, and to evaluate an optimum dosage for preventing hypocalcaemia. Eighty pregnant dry cows were assigned to four groups (I–IV). They were fed a total mixed ration (TMR) ad libitum. Groups II, III and IV received an average daily dose of 12, 23 and 43 g zeolite A/kg DM for the last 2 weeks prepartum. Individually DMI was recorded daily. Blood and urine samples were taken before, during and after zeolite A supplementation. Serum was analysed for Ca, Mg, P_i, K, non‐esterified fatty acids and β‐hydroxybutyrate (BHB). Urine was analysed for Ca, Mg, P_i, K and net acid‐base excretion (NABE). After calving, milk yield (fat corrected milk) and milk composition were determined. During zeolite A supplementation, mean DMI of Group IV (7.3 ± 1.3 kg/cow/day) was significantly lower compared to Groups I–III (10.1, 10.9, 9.5 kg/cow/day). The reduced feed intake of Group IV resulted in significantly increased BHB as well as decreased NABE after calving. Zeolite A supplementation in higher doses (III and IV) had a stabilizing effect on Ca metabolism around calving for older cows, whereas cows in Groups I and II showed a subclinical hypocalcaemia. The mean serum Mg concentration decreased significantly in older cows in Group IV at calving. The mean P_i concentration in cows of Group IV decreased into ranges of hypophosphataemia already 1 week after beginning of zeolite A feeding. The mean DMI postpartum as well as the milk yield was not affected by zeolite A supplementation. Feeding of 23 g zeolite A/kg DM TMR prepartum proved to be an adequate dosage for reducing subclinical hypocalcaemia frequency without significant effects on feed intake and P_i concentration in serum.     

Heat stress decreases plasma vitamin C concentration in lactating cows

Heat stress causes oxidative stress, which decreases plasma levels of vitamin C, an antioxidative vitamin in pigs and poultry. We investigated the plasma vitamin C concentration in lactating cows exposed to a hot environment temperature. In the first experiment, plasma vitamin C concentrations of 8 lactating cows were measured in summer and autumn. The concentration was found to be significantly lower in summer. The second experiment was performed using 4 lactating cows in a crossover design. The ambient temperature was set at 18 °C in the control treatment and at 28 °C in the heat-stressing treatment. Milk yields and feed intake tended to be lower in the stressing than control treatment. Rectal temperature and respiration rate were significantly (P < 0.05) higher in the heat-stressing treatment. The plasma vitamin C concentration was significantly (P < 0.05) lower in the heat-stressing period. These results indicate that heat stress decreases the plasma vitamin C concentration. Dietary supplementation with vitamin C may be beneficial for lactating cows in hot weather.     

Endocannabinoids as endometrial inflammatory markers in lactating Holstein cows

The objective of this study was to consider endocannabinoid system as inflammatory markers in bovine endometrium to better understand the role of this system in regulating many of the functions that are related to inflammatory condition. At day 26 post‐partum, fourteen cows were divided into two groups depending on the inflammatory condition: 1‐ subclinical endometritis (n = 7, with purulent or mucopurulent uterine discharge detectable in the vagina) and 2‐ healthy (n = 7, No (muco)) purulent discharge. Blood samples were collected at 26 and 30 days relative to calving to determine plasma tumour necrosis factor (TNF) and lipopolysaccharide‐binding protein (LBP) concentrations; moreover, uterine biopsy was carried out on day 26 post‐partum to measure mRNA abundance of TNF, interleukin‐1B (IL1B), interleukin‐6 (IL‐6), C‐X‐C motif chemokine ligand 8 (CXCL8), endocannabinoid receptor (CNR2), N‐acyl phosphatidylethanolamine phospholipase D (NAPEPLD), fatty acid amide hydrolase (FAAH), N‐acylethanolamine acid amidase (NAAA) and monoglyceride lipase (MGLL) by real‐time PCR. Results showed mean plasma concentrations of TNF and LBP were lower in healthy cows compared to subclinical endometritis cows (p < .05). Relative mRNA expression for NAAA and FAAH was decreased (p < .05), and relative mRNA expression for CNR2 and NAPEPLD increased in cows with subclinical endometritis compared to healthy cows. In conclusion, relative mRNA expression of TNF, IL1B and CXCL8 and plasma concentration of LBP increased during inflammatory condition along with decreased endocannabinoids hydrolyzing enzyme (NAAA and FAAH), increased enzymes that synthesize endocannabinoids (NAPEPLD) and relative gene expression of the endocannabinoid receptor; together, these contribute to increased endocannabinoids levels during inflammation. Overall, we provide evidence that endocannabinoid system is altered in endometrium tissue during inflammation through increased mRNA expression of CNR2 and synthesis enzyme and decreased mRNA expression of hydrolyzing enzymes interfere with pro‐cytokine production and signalling, which may interfere with the onset and progression of inflammation.     

青年荷斯坦奶牛初次超数排卵试验

对影响荷斯坦青年奶牛超数排卵的因素进行了对比分析,并探索了青年奶牛超排的可行性方案.卵巢上有黄体存在的供体牛可以用于超排.青年奶牛在不同性周期阶段进行超排的结果不同,但差异不显著.用FSH联合氯前列烯醇,采用常规逐日递减法肌肉注射进行超排,平均获得胚胎7.07枚,可用胚胎5.98枚;在人工授精的同时注射促排卵素3号(LRH A3),平均回收胚胎8.64枚,可用胚胎为5.5枚.促排卵素3号能提高胚胎的回收率,但可用胚胎率急剧下降.     

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)。     

Ruminal,cardiorespiratory and adrenocortical sequelae of Na2EDTA-induced hypocalcaemia in calves

A study was undertaken to provide further information on the ruminal, cardiorespiratory and hypothalamo-pituitary-adrenocortical (HPAC) physiological sequelae of hypocalcaemia in dairy calves.The functional picture observed in standing calves experiencing Na₂EDTA-induced progressive hypocalcaemia showed a biphasic pattern. During the first phase (Ca²⁺ varying between 1.20±0.09 and 0.64±0.15 mmol/L, mean±SD), the animals became dull and lethargic, shifting their weight from one hind limb to the other, with cool extremities and hypersalivation. Their ventilation was slightly increased but their heart rate, thoracoabdominal pressure, pulmonary mechanics, haemoglobin and temperature remained constant. Conversely, their systemic arterial pressure (SAP) and the amplitude of their ruminal contractions (RCA) were severely decreased. During the second phase (Ca²⁺ <0.64±0.15 mmol/L), there was restlessness, tachycardia, hypertension, polycythaemia and, finally, inability to stay upright. It is suggested that the diminished Ca²⁺ availability caused smooth-muscle and myocardial dysfunctions which could explain the RCA and SAP changes recorded during the first phase, whereas neural and/or humoral sympathetic discharge probably accounted for the reversal in SAP and heart rate when Ca²⁺ was decreased further. Serum cortisol increased regularly and remained significantly correlated with Ca²⁺ in each animal. Moreover, regression of cortisol/Ca²⁺ on Ca²⁺/ Na₂EDTA was significant (p0.001).It was concluded that mild asymptomatic hypocalcaemia severely impairs ruminal function, which will progressively worsen the Ca²⁺ deficit; that the inability to maintain posture in hypocalcaemia is not due to hypotension; and that the higher the HPAC response to hypocalcaemia, the higher the resistance to its effects. An asymptomatic periparturient cow with barely detectable ruminal activity may merit preventive calcium borogluconate therapy. Also, the physiological role of hypotension in explaining the clinical picture may be less important than other processes, such as neuromuscular failure. Finally, the present results imply a possible HPAC exhaustion in cows with periparturient paretic hypocalcaemia.Abbreviations A-aDO₂ alveolar-arterial O₂ difference - AVP arginin vasopressin - C _Ldyn dynamic lung compliance - ECG electrocardiogram - EEZF end expiratory zero flow - Hb_TOT total haemoglobin content - HPAC hypothalamo-pituitary-adrenocortical - HR heart rate - Na₂EDTA disodium ethylenediaminetetraacetate - O_2CT total O₂ content - P _aCO₂ arterial CO₂ tension - P _aO₂ arterial O₂ tension - PH periparturient hypocalcaemia - P _pl pleural pressure - P _ru intraruminal pressure - PTH parathyroid hormone - P_TOT plasma total protein - RCA amplitude of ruminal contraction - RCD duration of ruminal contraction - RCF frequency of ruminal contraction - R _L total pulmonary resistance - RR respiratory rate - SAP systemic arterial pressure - T _E expiratory time - T _I inspiratory time - T _p core temperature - V respiratory airflow - V _E minute volume - V _T tidal volume     

Effect of recombinant bovine tumor necrosis factor-α on hormone release in lactating cows

Tumor necrosis factor (TNF)‐α is a powerful macrophage cytokine released during infection, circulating in the blood to produce diverse effects in the organism. We examined the effect of recombinant bovine TNF‐α (rbTNF‐α) administration on hormone release in dairy cows during early lactation. Twelve non‐pregnant Holstein cows were treated subcutaneously with rbTNF‐α (2.5 µg/kg) or saline twice (at 11.00 and 23.00 hours). At 11.00 hours the next day, the cows were given growth hormone‐releasing hormone (GHRH, 0.25 µg/kg), thyrotrophin‐releasing hormone (TRH, 1.0 µg/kg), thyroid‐stimulating hormone (TSH, 10 µg/kg) or adrenocorticotropic hormone (500 µg/head) via the jugular vein. In the growth hormone‐releasing hormone challenge, the plasma growth hormone concentration was lower in the rbTNF‐α group than in the control (saline) group. The growth hormone and TSH responses to TRH were also smaller in the rbTNF‐α group than in the control. The plasma prolactin response to TRH was not affected by the rbTNF‐α treatment. In the TSH challenge, the rbTNF‐α‐treated cows had lower responses, as measured by plasma triiodothyronine and thyroxine, than the control cows. The rbTNF‐α treatment produced an increase in the basal plasma cortisol level, but the cortisol response to adrenocorticotropic hormone was the same level in both groups. The plasma concentrations of TNF‐α and interleukin‐1β in the cows were elevated by the rbTNF‐α treatment. The milk yield was reduced by the rbTNF‐α administration during 4 days. These data demonstrate that TNF‐α alters the secretion of pituitary and thyroid hormones in lactating cows. This effect may contribute to the suppression of the lactogenic function of the mammary gland observed in cases of coliform mastitis with high circulating TNF‐α levels.     

The concentration of ionized magnesium in serum during the periparturient period of non-paretic dairy cows

Ion-selective electrodes have recently been designed for determining the ionized concentration of magnesium (Mg²⁺) in serum. This development may allow new insights into some metabolic diseases of cattle. For this report, the concentrations of Mg²⁺, total magnesium (Mg_tot), ionized calcium (Ca²⁺), total calcium (Ca_tot), and inorganic phosphate (P_i) were determined in sera from seventeen 3-to 16-year-old Brown Swiss and crossed Simmental/Red Holstein cows during the periparturient period. In each animal, a transient increase of Mg²⁺ and Mg_tot serum concentrations was observed in association with the transient decrease in serum concentrations of Ca²⁺, Ca_tot and P_i after parturition. On average, throughout the study, the serum Mg²⁺ concentrations were 68.5% of those of Mg_tot, whereas the serum Ca²⁺ concentrations were 52% of those of Ca_tot. The possible mechanisms involved in the transient increase of Mg²⁺ and Mg_tot serum concentrations are discussed.Abbreviations Ca²⁺ ionized calcium - Ca_tot total calcium - Mg²⁺ ionized magnesium - Mg_tot total magnesium - P_i inorganic phosphate - PTH parathyroid hormone - PTHrP parathyroid homrone related protein     

Transport of fatty acids within plasma lipoproteins in lactating and non‐lactating cows fed on fish oil and hydrogenated palm oil

The aim of this study was to elucidate the effect of dietary fish oil (FO) and a blend of FO and hydrogenated palm oil (FOPO) on transport of fatty acids (FA) within plasma lipoproteins in lactating and non‐lactating cows. Two trials were conducted (one with lactating and another with non‐lactating dairy cows) in two 3 × 3 Latin squares that included three periods of 21 days. Dietary treatments for lactating cows consisted of a basal diet (Control; no fat supplement), and fat‐supplemented diets containing FO (500 g/day/cow) and FOPO (250 FO + 250 g/day/cow hydrogenated palm oil). For non‐lactating cows, dietary treatments consisted of a basal diet (Control; no fat supplement), and fat‐supplemented diets containing FO (170 g/day/cow) and FOPO (85 FO + 85 hydrogenated palm oil g/day/cow). In lactating cows, compared with control and FOPO, FO increased C16:0, C18:3 cis‐9, 12, 15, C18:2 cis‐9, trans‐11 and total saturated and polyunsaturated FA in plasma and increased C16:0, C18:2 cis‐9, trans‐11, total polyunsaturated and total polyunsaturated n‐6 in high‐density lipoprotein (HDL), whereas in non‐lactating cows, compared with control and FOPO, FO increased C16:0, C18:1 trans‐11, C18:2 trans‐9, 12, C18:2 cis‐9, trans‐11, C20:5 n‐3 and total saturated and polyunsaturated FA in plasma; C16:0, C18:1 trans‐11, C18:1 cis‐9, C18:2 trans‐9, 12, C20:5 n‐3 and total monounsaturated FA in HDL; and C18:1 trans‐6‐8, C18:1 trans‐9, C18:1 trans‐10, C18:1 trans‐11, C18:3 cis‐9, 12, 15 and C20:5 n‐3 in low‐density lipoprotein (LDL). FO increased C20:5 n‐3 in plasma and lipoproteins in non‐lactating cows and increased C18:3 cis‐9, 12, 15 in plasma (in lactating cows) and LDL (in non‐lactating cows). We concluded from results of this study that in bovine plasma, the LDL fraction appears to be the main lipoprotein transporting C18:1 trans isomers and is more responsive than other lipoprotein fractions to variation in supply of dietary lipids.     

Effects of chelated Zn/Cu/Mn on redox status,immune responses and hoof health in lactating Holstein cows

To evaluate the effects of chelated Zn/Cu/Mn on redox status, immune responses and hoof health in lactating Holstein cows, 48 head in early lactation were divided into healthy or lame groups according to their gait score. Cows were fed the same amount of Zn/Cu/Mn as sulfate salts or in chelated forms for 180 days, and foot-and-mouth disease (FMD) vaccine was injected at day 90. The results showed that lame cows had lower antioxidant function, serum Zn/Mn levels, hair Cu levels, and hoof hardness. Moreover, increased antioxidant status, FMD antibody titers, serum and hair levels of Zn/Cu/Mn, and hoof hardness and decreased milk fat percent and arthritis biomarkers were observed in cows fed chelated Zn/Cu/Mn. In summary, supplementation with chelated Zn/Cu/Mn improved antioxidant status and immune responses, reduced arthritis biomarkers, and increased accumulation of Zn/Cu/Mn in the body and hoof hardness in dairy cows.     

Use of monosodium glutamate by‐product in cow diet on performance of lactating dairy cows

Eight multiparous lactating Holstein cows were randomly assigned in a 4 × 4 replicated Latin square design to receive four dietary treatments. The dietary treatments were monosodium glutamate by‐product (MSGB) replacement for soybean meal in concentrate at four levels: MSGB replacement at 0, 20, 40 and 60%, respectively. Pangola hay was given on an ad libitum basis. It was found that total dry matter intake, concentrate intake, pangola hay intake and all apparent digestibilities were not different among treatments. Ammonia nitrogen concentration in the rumen at 4 h post‐feeding was significantly different, in which the 0% treatment had the highest (P < 0.05) while the 20% treatment had the lowest. Milk fat percentage was the highest (P < 0.05) in the 0% treatment. MSGB replacement at 40% and 60% were shown to be the lowest (P < 0.05) feed cost for milk production, and profitability of milk production was the highest (P < 0.05) for the 60% treatment. Based on this experiment, it could be concluded that MSGB replacement for soybean meal at 20‐60% in the feed for dairy cows presented no negative effects on their performances. In addition, it could decrease feed cost 2.9‐17.3% and increase milk production profit up to 33.3% in the 60% treatment.     

清热解暑中药验方对热应激奶牛采食行为及产奶性能的影响

本试验探讨3种清热解暑中药验方对热应激奶牛采食行为及产奶性能的影响.40头泌乳末期的中国荷斯坦奶牛随机分为4组,分别接受4种处理,即对照组、清热健胃组、清暑组和加减白虎汤组.所有试验牛饲喂相同的全混合日粮,3个处理组分别补饲清热健胃散、清暑散和加减白虎汤散剂,用量为每日每头150 g.结果发现,全天采食量和牛舍各时点的温度和温湿指数极显著负相关.在奶牛处于轻度热应激时添加清热解暑中药对采食行为影响不显著,仅在第1天早饲时略影响采食速度.清暑组干物质采食量较高,产奶量下降较少,表明清暑散具有缓解热应激、促进食欲的作用.     

Wheat grain as a prepartal cereal choice to ease metabolic transition from gestation into lactation in Holstein cows

Wheat grain (WG) is a unique cereal rich in easily fermentable starch and low in cation–anion difference (e.g. 5.3 mEq/100 g). The controlled prepartal dietary inclusion of WG, thus, has the potential to ease adapting the rumen microbes and papillae to the high‐starch lactation diets, stimulate feed intake, reduce hypocalcaemia by reducing extracellular alkalinity and a moderate induction of bone resorption, and improve milk yield in periparturient cows. The primary objective was to determine the effects of prepartal feeding of WG compared to barley grain plus wheat bran on metabolic and productive criteria in periparturient Holstein cows. Twenty‐four dry cows and 16 pregnant heifers were blocked based on parity and projected calving date and fed a prepartal diet containing either (i) ground WG (18% on a dry matter basis) or (ii) a conventional diet with ground barley grain and wheat bran or control diet, from 28‐day prepartum until parturition. All cows were fed the control diet during 21‐day postpartum. Prepartal dietary inclusion of WG increased prepartum feed intake, elevated blood glucose and attenuated hypocalcaemia at 7‐day prepartum and 1‐day postpartum, reduced urine pH, and increased milk fat percent and yield. Blood proteins at 7‐day prepartum were higher and placenta tended to be expelled sooner in WG‐fed cows than in other cows. Treatments did not affect milk protein, changes in body condition score; total time spent eating, ruminating and chewing; blood levels of urea nitrogen, cholesterol, and phosphorous, fecal pH, and calving difficulty. Therefore, the prepartal dietary use of WG proved effective in the simultaneous improvement of calcium and energy states, and thereby, in easing the metabolic transition from gestation into lactation in Holstein cows.     

Effect of types of breeding on embryo survival following first AI in lactating Holstein cows

The main objective was to investigate the effects of timed-AI protocols versus AI following oestrus detection on circulating progesterone (P4) and embryo survival after first service in Holstein cows. Cycling status was determined by ultrasonography and by plasma P4 concentrations 14 and 26 days after calving, and only cows with a corpus luteum and/or P4 ≥ 1 ng/ml were used. Cows were randomly allocated to one of three types of breeding: DO (n = 80), received GnRH-7d-PGF2α-3d-GnRH and Ovsynch56 was initiated 7 days later; G7G (n = 70), received PGF2α-2d-GnRH and Ovsynch56 (GnRH-7d-PGF2α-56h-GnRH-16h-AI) was initiated 7 days later; or AI based on oestrus detection, EDAI (n = 60). Progesterone was also determined at AI and 8, 16, 18 and 20 days after AI; ISG15 and MX2 mRNA abundance were determined 16 days after AI. Mean plasma P4 at AI was greater in the EDAI group compared with DO and G7G groups, while after AI, P4 was greater in DO and G7G groups compared with EDAI group. However, the percentage of cows with a concentration of P4 < 0.8 ng/ml at AI did not differ among groups. Relative mRNA abundance of ISG15 and MX2 was greater in the DO and G7G groups compared to those in EDAI group. Pregnancy per AI 16, 32 and 60 days after AI was greater (p < .05) in cows in the DO group compared with those in EDAI group (47.5%, 38.8% and 36.3% vs. 30.0%, 21.7% and 15.0%). Pregnancy losses between 16 and 60 days after AI were greater (p < .05) in cows in the EDAI (50.0%) group compared to those subjected to DO (23.7%) or G7G (24.1%). In conclusion, the use of timed-AI synchronization protocols resulted in greater circulating P4 concentrations post-AI and greater embryo survival following first service in lactating Holstein cows.