Efficient Association between PGF2α and Methyl 4‐hydroxybenzoate Sex Pheromone Prior to Electroejaculation in Dogs

Electroejaculation is a technique that can be used to collect semen from canines, but its use with this group of animals is restricted by low success rate and low semen quality. Here, we evaluated whether pharmacological and sexual sensory stimuli, which may affect ejaculation, can increase electroejaculation efficiency and improve ejaculate quality. We worked with 20 dogs of mixed breed weighing between 5.3 and 22.2 kg, divided into two groups. Both groups were exposed to a spayed female for 10 min, but in the second group, the same spayed female had her vagina impregnated with methyl 4‐hydroxybenzoate synthetic pheromone for 10 min and after receiving dinoprost tromethamine IM, 0.1 mg /kg. After stimulation, all dogs were chemically restrained with ketamine, 8 mg/kg, IM; and xylazine, 1 mg /kg, IM, and subjected to electroejaculation protocol. We obtained 100% of antegrade ejaculate in treatments when the spayed female had her vagina impregnated with pheromone and 80% when she did not. Sperm motility was significantly different (p < 0.05) between controls and the test group (10.1 ± 4.5 and 43.0 ± 8.3, respectively). We concluded that the adopted electroejaculation protocol was efficient and that the PGF2α associated with sexual sensory stimulation can improve semen quality in dogs undergoing the procedure.     

Efficacy of a single application of a 12.5% pyriprole topical solution against laboratory infestations with ticks (Ixodes ricinus, Dermacentor reticulatus, and Rhipicephalus sanguineus) on dogs

In three separate studies, the efficacy of a single treatment with a 12.5% pyriprole spot-on solution was investigated against induced infestation with Ixodes ricinus, Dermacentor reticulatus and Rhipicephalus sanguineus on dogs (both sexes; Beagles in Studies 1 and 2, mixed-breed in Study 3). For each tick species, one group of 8 dogs left untreated (Studies 1 and 2) or treated with a placebo solution (Study 3) was compared with another group treated once with the spot-on solution at a dose rate of at least 12.5mg/kg. The dogs were infested with 50 unfed adult ticks of the respective species at various time-points before and after treatment and the surviving attached and unattached ticks were recorded 48 h after re-infestation. For each tick species, efficacy was assessed for each time-point and cumulatively for the whole evaluation period. The dogs were submitted to general health observations and clinical assessments during the study. Efficacy against I. ricinus and R. sanguineus was 100% during the whole evaluation period of 30 days. For D. reticulatus cumulative efficacy for the 30 days after treatment was 98.9%. The product was well tolerated by all the animals.     

Noradrenergic Control of GnRH Release from the Ewe Hypothalamus In Vitro: Sensitivity to Oestradiol

The present study investigates the influence of α₁‐adrenoreceptors in GnRH release in vitro and determines whether oestradiol modulates α₁‐adrenoreceptor‐GnRH interaction. Within 10 min after ewe sacrifice, saggital midline hypothalamic slices were dissected, placed in oxygenated Minimum Essential Media‐α (MEM‐α) at 4°C and within 2 h were singly perifused at 37°C with oxygenated MEM‐α (pH 7.4; flow rate 0.15 ml/min), either with or without oestradiol (24 pg/ml). After 4‐h equilibration, 10‐min fractions were collected for 4 h interposed with a 10‐min exposure at 60 min to specific α₁‐adrenoreceptor agonist (methoxamine) or antagonist (thymoxamine) at various doses (0.1–10 mm ). The α₁‐adrenoreceptor agonist (10 mm ) increased (p < 0.05) GnRH release at 90 min both in presence and absence of oestradiol. However, in presence of oestradiol, α₁‐adrenoreceptor agonist (10 mm )‐induced GnRH release remained elevated (p < 0.05) for at least 60 min. The bioactivity of the released GnRH was studied using a hypothalamus–pituitary sequential double‐chamber perifusion. Only after exposure of hypothalamic slices to α₁‐adrenoreceptor agonist (10 mm ), did the hypothalamic eluate stimulate LH release from pituitary fragments (n = 9, 7.8 ± 12.3–36.2 ± 21.6 ng/ml) confirming that the α₁‐adrenoreceptor agonist stimulated release of biologically active GnRH. In summary, GnRH release from the hypothalamus is under stimulatory noradrenergic control and this is potentiated in the presence of oestradiol.     

Effect of supplemental nutrient source on heifer growth and reproductive performance,and on utilization of corn silage-based diets by beef steers

Two experiments were conducted to determine effects of oilseeds or soybean hulls on growth and reproductive performance of heifers and utilization of corn silage diets by growing beef cattle. In Exp. 1, 96 beef heifers (249 kg of BW) were used in a randomized complete block design. Treatments were as follows: 1) corn and soybean meal (CON) at 56% of the DMI; 2) whole linted cottonseed at 15% of the DMI (COT); 3) whole raw soybeans at 15% of the DMI (SB); or 4) pelleted soyhulls at 30% of the DMI (SH). Diets were formulated to be isonitrogenous (13.8% CP) and fed to achieve target weights equal to 65% of expected mature BW at the time of AI. Estrus was synchronized and heifers were inseminated by AI in response to detected estrus. Because the energy value for SH was underestimated, cumulative ADG for SH (1.03 kg/d) was greater (P < or = 0.03) than for CON (0.89 kg/d), COT (0.87 kg/d), or SB (0.86 kg/d). Treatment did not affect (P > 0.10) the proportion of pubertal heifers at the beginning of the breeding season: CON (60%), COT (53%), SB (69%), SH (71%), or first-service conception rates: CON (37%); COT (38%); SB (57%); SH (42%). In Exp. 2, crossbred steers (387 kg) were used in a 6 x 6 Latin square design to evaluate the effects of supplemental nutrient source on utilization of corn silage diets. Treatments included diets used in Exp. 1, plus a negative control (soybean meal at 10% of the DMI; SIL) and whole raw soybeans at 25% of the DMI (SB25). Diets were formulated to be isonitrogenous (13.8% CP) except SB25 (17% CP), and were fed twice daily at 1.8 x NEm. Oilseed inclusion decreased (P < 0.10) acetate:propionate ratios and (P < 0.10) apparent ruminal OM and ruminal and total tract NDF digestibilities. The CON and SH diets had the greatest (P < 0.10) total-tract OM digestibilities. Microbial efficiencies were greatest (P < 0.10), and long chain fatty acid flow to the duodenum increased (P < 0.10) with oilseeds. Biohydrogenation averaged 90.4% and increased slightly (P < 0.10) when oilseeds were added to the diet. Adding oilseeds or soybean hulls to corn silage-based diets did not affect reproductive performance of heifers. Although oilseed additions increased total fatty acid flow to the duodenum, a high degree of biohydrogenation occurred, greatly increasing C18:0, with only marginal increases in unsaturated fatty acid flow. Depending on diet and feeding conditions, inclusion of whole oilseeds may not be an effective means of increasing linoleic acid supply for ruminant animals.