GnRH analogs induce a LH peak and increase pregnancy per timed-AI in ewes.

To date, there have been no studies testing the capacity of GnRH analogs and respective doses to induce a LH peak in sheep. In this sense, the present study aimed to evaluate the capacity of different synthetic forms and doses of GnRH in inducing LH release in sheep, and the effect of GnRH administration at timed artificial insemination (TAI) on pregnancy per timed-AI. In experiment 1, ewes (n = 40) received an intravaginal device (IVD) of medroxyprogesterone acetate (MPA; 60 mg) for 7 d and prostaglandin F2α analog on Day 5. On Day 7, the ewes were allocated randomly into one of eight groups (n = 5/group), which received a GnRH analog at a specific dose, as follows: lecirelin (12.5 or 25 µg), gonadorelin (50 or 100 µg), buserelin acetate (4.2 or 8.4 µg), or deslorelin (375 or 750 µg). Blood samples for LH determination were obtained at 0, 2, 4, and 6 h after GnRH and the IVDs were removed after the last blood collection. The maximal LH concentration induced by gonadorelin at doses of 50 µg and 100 µg (12.0 ± 2.4 ng/mL and 28.6 ± 7.1 ng/mL, respectively) was lower (P < 0.05) than serum LH induced by 8.4 µg of buserelin (78.9 ± 12.9 ng/mL), 375 µg and 750 µg of deslorelin (75.6 ± 7.4 ng/mL and 72.1 ± 10.6 ng/mL, respectively) and 12.5 µg and 25 µg of lecirelin (73.3 ± 17.8 ng/mL and 61.6 ± 5.9 ng/mL, respectively). However, the maximal LH concentration induced by 4.2 µg of buserelin (49.4 ± 5.9 ng/mL) was similar (P > 0.05) to the 100 µg of gonadorelin. The total release of LH (area under the curve - AUC) after treatment with 50 µg of gonadorelin (31.7 ± 5.9 ng h/mL) was lower (P < 0.05) than after other agonists. In a second experiment, 330 ewes were treated with IVD containing MPA for 7 d. Simultaneously with IVD removal, 250 µg of cloprostenol and 200 IU of eCG were administered. Then, ewes were assigned randomly to either no further treatment (control); or to receive 4.2 µg of buserelin acetate (GnRH group) at cervical TAI, which was performed with fresh semen 54 h after IVD withdrawal in all the animals. Higher pregnancy per timed-AI was observed for GnRH (50.3 %) compared to control (40.7 %). We conclude that buserelin acetate (8.4 µg), lecirelin (12.5 and 25 µg) and deslorelin (375 and 750 µg) induced a greater stimulatory effect on LH secretion than gonadorelin treatment. Furthermore, buserelin acetate treatment at TAI increased pregnancy per timed-AI in ewes previously treated with MPA and eCG.

Increased ß-hydroxybutyrate (BHBA) concentration affect follicular growth in cattle.

Metabolic stress conditions caused by negative energy balance (NEB) have been associated with reduced fertility in cows. ß-hydroxybutyrate (BHBA) is the main circulating ketone body, which accumulates within follicular fluid. The aim of this study was to evaluate the effects of BHBA on follicle growth and on ovulatory mechanisms in cattle. At 72 h after intrafollicular injection, there was a decrease in follicular diameter in BHBA group compared to control (P = 0.02). Furthermore, follicle growth rate was reduced post-treatment with BHBA in comparison to the control group (P < 0.03). The BHBA intrafollicular injection in follicles ≥ 12 mm, however, did not affect E2 and P4 concentrations in the follicular fluid. In addition, the relative abundance of genes involved in the ovulatory cascade (ADAM 17, AREG, EREG, PTGS2), steroidogenesis (CYP19A1, 3BHSD, STAR), cellular stress (SOD1, CAT, GPX1, HSPA5, XBP1s, XBP1u, ATF4, ATF6), monocarboxylic acid transporters (SLC16A1, SLC16A7) and apoptosis (XIAP) was similar between groups. In conclusion, the results of this study indicate that the increase in intrafollicular concentrations of BHBA affects follicular growth, but it does not compromise the ovulatory cascade and cellular homeostasis in bovine granulosa cells.

Immune response of a commercial vaccine against Leptospira interrogans: Antibodies and cytokine levels.

Good vaccines should confer protection against specific pathogens in experimental and field conditions. However, some commercial vaccines are not capable to confer protection to animals, being inefficient in a bovine vaccine program. In this sense, the aim of this study was to evaluate the antibody levels involved in the immune response in vaccinated cows against leptospirosis, as well as acute phase protein and the immunological markers in a vaccine program in beef cattle. Twenty non-lactating cows, negative for leptospirosis and without vaccination against this disease were evaluated during five months. The herd was divided into two groups named as A (the control group) and B (the vaccinated group). Ten cows from the group B received an initial dose (5 mL) of vaccine on day 0 and one booster dose (5 mL) on day 29. In order to evaluate humoral response (MAT - titration 1:25), cytokine levels (tumor necrosis factor (TNF) and interleukin-10 (IL-10)), and C-reactive protein levels (an acute phase protein), blood samples were evaluated on days 0, 29, 40, 83 and 144 after vaccination. In none of the evaluated periods it was observed specific antibodies to any of the six serovars presents in the vaccine, as well as no difference between groups regarding cytokine and C-reactive protein levels. Therefore, the vaccine used did not stimulate the immune response of cattle, inferring the absence of protection against infections by L. interrogans.

Benefits of a prepartum anionic diet on the health of dairy cows in the transition period: prevented subclinical hypocalcemia and minimizing oxidative stress

Background: There are many metabolic diseases that affect dairy cows during the transition period, among them, the postparturient hypocalcemia, also known as milk fever, puerperal paresis syndrome, or fallen cow. This disease may affect animals 72 h after calving due to a nutritional imbalance in the calcium metabolism, which occurs after a sudden demand of this mineral at the beginning of lactation. This problem is more common in animals with high milk production, and usually after the second lactation. Therefore, this study evaluated whether the anionic diet on the prepartum phase would be beneficial for dairy cows in the transition period. Materials, Methods & Results: Eight Holstein cows on their second and third pregnancy with body condition score between 3.5 and 4 were used. During the experiment, the animals remained in paddock with grazing Tifton 85 (Cynodon spp.) and water ad libitum. Two groups of four animals each were used: the group A (control) received a dietary cation-anion difference (DCAD) diet of 2.57 mEq kg-1, and the second group, called the group B (treatment), received a DCAD diet of -112.2 mEq kg-1. To evaluate animal health, we performed gynecological examinations, in addition to blood samplings on days 20, 10 and 5 prepartum and 3, 7, 12 and 20 postpartum to assess seric levels of calcium (Ca), total protein, albumin, globulin, cholesterol, triglyceride, urea, and hepatic function (AST, ALT and GGT). It was also measured the production of free radicals (ROS) and lipid peroxidation (TBARS) in the transition period of the cows. No statistical differences were observed between groups regarding body condition score, uterine tone, dominant follicle diameter, size and presence of the corpus luteum and the presence of genital discharge up to 30 days postpartum. However, the anionic diet prevented a dramatic reduction in calcium levels, unlike what occurred in the control cows (the group A) where a subclinical hypocalcemia was observed.[...]

Benefits of a prepartum anionic diet on the health of dairy cows in the transition period: prevented subclinical hypocalcemia and minimizing oxidative stress

Background: There are many metabolic diseases that affect dairy cows during the transition period, among them, the postparturient hypocalcemia, also known as milk fever, puerperal paresis syndrome, or fallen cow. This disease may affect animals 72 h after calving due to a nutritional imbalance in the calcium metabolism, which occurs after a sudden demand of this mineral at the beginning of lactation. This problem is more common in animals with high milk production, and usually after the second lactation. Therefore, this study evaluated whether the anionic diet on the prepartum phase would be beneficial for dairy cows in the transition period. Materials, Methods & Results: Eight Holstein cows on their second and third pregnancy with body condition score between 3.5 and 4 were used. During the experiment, the animals remained in paddock with grazing Tifton 85 (Cynodon spp.) and water ad libitum. Two groups of four animals each were used: the group A (control) received a dietary cation-anion difference (DCAD) diet of 2.57 mEq kg-1, and the second group, called the group B (treatment), received a DCAD diet of -112.2 mEq kg-1. To evaluate animal health, we performed gynecological examinations, in addition to blood samplings on days 20, 10 and 5 prepartum and 3, 7, 12 and 20 postpartum to assess seric levels of calcium (Ca), total protein, albumin, globulin, cholesterol, triglyceride, urea, and hepatic function (AST, ALT and GGT). It was also measured the production of free radicals (ROS) and lipid peroxidation (TBARS) in the transition period of the cows. No statistical differences were observed between groups regarding body condition score, uterine tone, dominant follicle diameter, size and presence of the corpus luteum and the presence of genital discharge up to 30 days postpartum. However, the anionic diet prevented a dramatic reduction in calcium levels, unlike what occurred in the control cows (the group A) where a subclinical hypocalcemia was observed.[...](AU)