In early lactation dairy cattle suffer metabolic alterations caused by negative energy balance, which predisposes to fatty liver and ketosis. The aim of this study was to evaluate the metabolic condition of high yielding dairy cows subjected to three treatments for preventing severe lipomobilization and ketosis in early lactation. Fifty four multiparous Holstein cows yielding >30 L/day were divided into four groups: control (CN= no treatment), glucose precursor (PG= propylene-glycol), hepatic protector (Mp= Mercepton®), and energy supplement with salts of linolenic and linoleic faty acids (Mg-E= Megalac-E®). Treatments were administrated randomly at moment of calving until 8 weeks postpartum. Blood samples were collected on days 1, 7, 14, 21, 28, 35, 42 and 49 postpartum. Body condition score (BCS) was evaluated at the same periods and milk yield was recorded at 2 nd , 4 th , 5 th , 6 th , 7 th , and 8 th weeks of lactation. Concentrations of non-esteriϐied fatty acids (NEFA), albumin, AST, ß-hydroxybutyrate (BHBA), cholesterol, glucose, total protein, urea and triglycerides were analyzed in blood samples. Cut-off points for subclinical ketosis were deϐined when BHBA ≥1.4 mmol/L and NEFA ≥0.7 mmol/L. General occurrence of subclinical ketosis was 24% during the period. An ascendant curve of cholesterol and glucose was observed from the 1 st to the 8 th week of lactation, while any tendency was observed with BHBA and NEFA, although differences among treatments were detected (p≤0.05). BCS decreased from a mean of 3.85 at 1 st week to 2.53 at 8 th week of lactation (p=0.001). Milk yield was higher in the Mg-E group compared with the other treatment groups (p≤0.05) Compared with the CN group, the treatments with Mp and PG did not show signiϐicant differences in blood biochemistry and milk yield. Cows receiving PG and Mg-E showed higher values of BHBA and NEFA (P<0.05), indicating accentuated lipomobilization. Supplementation with Mg-E also resulted in signiϐicant higher concentrations of cholesterol, BHBA, urea, AST and lower values of glycemia. This performance may be explained by the highest milk yield observed with this treatment. Treatments with PG and Mp did not improve milk yield, compared with control cows, but did not show metabolic evidence of ketosis, fat mobilization or fatty liver. These results suggest that treatment with Mg-E improves milk production but induces a higher negative energy balance leading to moderated lipomobilization and ketone bodies production, increasing the risk of fatty liver.

Background:The pregnancy rate in fixed-time insemination (FTAI) programs in beef cattle is affected by several factors, including the size of ovulatory follicle (OF). Induced ovulation of small OF (≤11 mm) reduces the chance of pregnancy after FTAI when compared to ovulation of larger follicles (≥12 mm). Hormonal treatments to enhance the follicle growth have been widely used in comercial beef cattle systems, aiming to improve the development of a dominant follicle. The objective of this experiment was to evaluate the effect of treatment with eCG or FSH at the time of progesterone implant removal on the diameter of OF, final follicle growth and pregnancy rate in beef cows. Materials, Methods & Results: Three hundred and seven suckled beef cows with body condition score 2.80 ± 0.24 (1 to 5 scale) and 45 to 70 days postpartum were synchronized to FTAI. On day 0, intravaginal implants containing 1 g of progesterone, were inserted and administered 2 mg of estradiol benzoate (EB), i.m. On day 7, intravaginal implants were

Estrous synchronization with prostaglandin in commercial MOET programs frequently results in insufficient numbers of recipients for embryo transfer. The aim of this trial was to compare the efficiency of 2 different methods of estrous synchronization in crossbred beef heifers. A total of 235 cycling heifers (Brangus and Braford), with a mean age of 24 months (range 22-26 months), body condition score of 3.5 ± 0.1 (1-5 scale), and mean weight of 340 ± 22 kg were assigned to 2 treatment groups stratified according to body weight and genotype. In Group 1 (n = 157), heifers received 2 injections of prostaglandin [Croniben, 150 μg of D(+) cloprostenol, i.m.; Biogenesis-Bágo, Buenos Aires, Argentina] with an interval of 14 days. After the second injection, detection of estrus was monitored for 5 days. In Group 2 (n = 78), heifers received an intravaginal device of progesterone (Day 0; 0.558 g; Cronipres Mono Dose M-24, Biogenesis-Bágo) and at the same time received an i.m. injection of estradiol benzoate (2 mg; Cronibest, Biogenesis-Bágo). On Day 7, devices were removed and heifers were injected with prostaglandin. Twenty-four hours later (Day 8), 1 mg of estradiol benzoate was injected i.m. All recipients had estrus detected for 72 h after the end of treatment to determine the estrous synchronization rate. Before embryo transfer 7 days after the detected estrus, heifers were examined by transrectal ultrasonography (Chison 600Vet, 5-MHz transducer, National Ultrasound, Duluth, GA, USA) to confirm the presence of a CL and its size or an unovulated follicle on the ovaries. Those with a CL of 1.7 cm2 or greater were selected to receive a frozen-thawed embryo. The frequencies of synchronous estrus, ovulation, unovulated follicles, and use of recipients were compared by chi-square test. Group 2 had a higher estrous synchronization rate (70%) and proportion of selected recipients (51.2%) compared with Group 1 (55% and 35.6%, respectively; P < 0.05). Ovulation rate (64% v. 72%) and incidence of unovulated follicles (20.6% v. 21.8%) for Groups 1 and 2, respectively, did not differ (P > 0.05). In summary, treatment with a 0.558-g progesterone intravaginal device, plus injections of estradiol benzoate and PGF, was more efficient than 2 PGF injections alone in synchronizing estrus and increased the use of crossbred beef heifer recipients in MOET programs. The ovulation rate and incidence of unovulated follicles were similar in both methods of estrous synchronization.

Successful establishment of pregnancy in the cow depends on early rise of progesterone (P4) to improve embryo development. The present study was carried out to determine the corpus luteum (CL) function and pregnancy rate following the administration of 1.500 IU of hCG in suckled beef cows on Day 4 after fixed-time AI (FTAI). Crossbred Angus cows (n = 429), 40 to 70 days postpartum, were synchronized using 2 mg of oestradiol benzoate (EB) i.m. and an intravaginal progesterone-releasing device containing 1 g of P4 for 7 days. At device removal, prostaglandin F2a (150 mg of D-cloprostenol) was injected i.m.; 24 h later, 1 mg of EB was given and the FTAI were done 30 to 36 h after EB using semen of just 1 bull. Cows were assigned alternatively to receive 1.500 IU of hCG i.m. (n = 200) or 1 mL of saline i.m. (n = 229) on Day 4 after FTAI. Ovaries were examined by transrectal ultrasonography (n = 71) on Days 4 and 7 to detect the presence and to measure the area of CL. Blood samples were collected on Days 4, 7, 10, 14, and 30 post-oestrus to determine P4 concentration by RIA. Pregnancy diagnoses were done 30 days after FTAI. The effects of treatments on CL area and serum P4 levels were analysed by ANOVA (Proc GLM, SAS Institute Inc., Cary, NC, USA) and pregnancy rates compared by chi-square (Proc CATMOT, SAS). The induction of accessory CL determined on Day 7 was 44% in cows treated with hCG and not observed in the control group. The area of the CL on Day 7 was significantly higher (P < 0.01; 3.37 ± 2.56 v. 2.56 ± 0.22 cm2) in the hCG group. Despite the increase in CL size, the mean levels of P4 on Days 4, 7, 10, 14, and 30 post-AI indicated no difference (P > 0.05) in CL function between control and hCG-treated cows. On Day 30, pregnancy rates were not different (P = 0.08), at 46.7 and 55% for control and hCG-treated cows, respectively. In conclusion, administration of 1.500 IU of hCG on Day 4 post-FTAI did not improve pregnancy rate in suckled beef cows.