BackgroundA major, unresolved issue is how the uterine microenvironment determines pregnancy success in cattle. Before implantation, conceptus development depends on the uterine secretome (i.e., histotroph). Despite its pivotal role, little is known about the dynamics of histotroph synthesis and changes in composition throughout the early diestrus and the relevance to pregnancy establishment. We hypothesize that disturbances on histotroph composition affect the establishment of pregnancy. Aim was to disturb histotroph composition at early diestrus and verify the effects on: (Exp. 1) timing to restore its composition; and (Exp. 2) pregnancy rate after multiple-embryo transfer. Estrous cycle of multiparous Nelore cows were synchronized and estrus was considered d 0 (D0) of the experiments. Disturbance was through flushing each uterine horn with 30 mL of DMPBS and collecting the resulting uterine luminal flushing (ULF) on D1; D4; D7; D1 + D4 + D7. Control group remained not-collected. In Exp. 1, ULF was collected on D7.5 from all animals and used for quantification of total protein concentration and abundance of albumin. In Exp. 2, three in vitro-produced embryos were transferred to the uterine horn ipsilateral to the ovary containing the CL on D7.5 and pregnancy was checked on D25 by ultrasound.ResultsIn Exp. 1, ULF collection on D4 or D7 increased (1.5- to 2.2-folds) the total protein concentration and albumin abundance. ULF collection on D1 did not alter (P > 0.10) these endpoints. In Exp. 2, ULF collected on D4 or D7 decreased pregnancy rates to approximately half of that measured in the remaining groups.ConclusionsSubtle perturbations imposed to the native intrauterine milieu, such as those caused by a single, low-volume collection of ULF, profoundly disturbs intrauterine composition and pregnancy success. At least 4 d were necessary for the uterus to recover its composition and the functional capacity to carry post-implantation gestation.

BackgroundInsufficient production of anti-luteolytic signals by the pre-attachment embryo is considered a major cause of pregnancy failure in cattle. We tested the hypothesis that transfer of multiple blastocysts (n = 5/recipient) and progesterone (P4) supplementation amplify anti-luteolytic signaling and reduce embryonic losses in beef cattle. Cows detected in estrus (D0; n = 104) were assigned randomly to receive 150 mg of injectable long-acting P4 (iP4) or vehicle (non-iP4) on D4 and transcervical transfer of none or five, grade 1, not-frozen, in vitro-produced blastocysts, on D7. Luteal development and time of structural luteolysis were monitored by ultrasonography. Plasma P4 concentrations were determined on D4, D5 and D7, and daily between D14 and D20. Conceptus signaling was monitored by transcript abundance of interferon-stimulated gene 15 (ISG15) in peripheral blood mononuclear cells isolated on D14, D16, D18 and D20. Early embryonic mortality (EEM) was defined as the absence of ISG15 mRNA upregulation over time and/or luteal regression up to D20. Late embryonic mortality (LEM) was defined as the absence of a conceptus with a heartbeat on pregnancy diagnosis at D30 (PD30) after observing upregulation of ISG15 mRNA and extension of luteal lifespan. Pregnant cows presented conceptuses with heartbeat at PD30.ResultsOn D5, iP4-treated cows had P4 concentrations 2.07-fold greater than non-iP4 treated (P < 0.001). On D7, P4 concentrations were similar. Pregnant and LEM animals showed a progressive increase in the abundance of ISG15 from D14 to D20. iP4-treated cows detected pregnant at PD30 had 1.53-fold greater abundance of ISG15 mRNA between D14 and D20 than non-iP4 treated cows (P = 0.05). iP4 doubled the frequency of EEM while it did not affect LEM. At PD30, embryonic survival was 37.0% vs. 55.6% for iP4-treated vs. control cows. Majority of pregnant cows (71%) presented only a single viable embryo.ConclusionsA substantial proportion of cows had EEM (31%) and LEM (20%) even after transferring multiple blastocysts. This argues that mortality was due to poor uterine receptivity that could not be reversed by supplemental P4 or overcome by transferring multiple blastocysts. Further, a given uterine environment was not necessarily adequate to all embryos.

A hybrid stochastic model was developed including discrete events and agent-based simulations in order to identify the productive parameters and management criteria that most affect meat sheep production. A sheep herd on a pasture termination system, without weaning and with natural mating, was outlined. In order to devise this herd, a pre-existing database from between 1999 and 2013 was used. This conceptual model included the flushing, mating, gestation, lactation, termination and maintenance phases. Health, feeding and management criteria were also considered and recommended. Simulation scenarios were built which were later evaluated by regression analysis. The net operational margin was between R$ 11 741.80 and R$ 21 389.80, and an average of R$ 14 412.14 ± R$ 3 873.02 for different scenarios. Food costs had the greatest impact (25.4%) in relation to operating costs, while health costs were the lowest (1.3%). The abortion rate showed a higher linear response in contrast to the birth rate and the net operating margin, upon analysing ewe productivity parameters. However, neonatal mortality showed the greatest impact on net profit and on general lamb mortality. Carrying out economic analyses within the livestock sector can make a difference within such a competitive market, where prices are not controlled, only costs. The use of discrete event and agent-based simulation methodologies allowed for the assessment of different approaches to sheep production. The present study demonstrated the tool’s potential within the scope of meat sheep production, but this model can act as a guideline for other animal production systems.

Cash flows were developed to verify, over a 15-year period, the effect of anticipating puberty (using feedlot and nutritional supplementation) and pregnancy diagnosis (using conventional transrectal ultrasound or color Doppler) on the net present value (NPV) of farms dedicated to producing Nellore (Bos taurus indicus) or Nellore x Angus (Bos taurus taurus) crossbred calves. In addition, in order to determine the effect of input prices on the viability of the enterprise, an economic analysis was carried out with the historical prices paid and received by Brazilian farmers over a 10-year period. Multiple regression was the statistical technique used to construct models that adequately described the relationships between the various independent variables (genetic group, nutritional strategy, pregnancy diagnosis technique, and relative market prices) and the dependent variable, which was represented by the NPV economic indicator. The fact that Nellore x Angus females reached puberty earlier than Nellore females favored the number of weaned calves and therefore, the NPV of the enterprise. Conducting pregnancy diagnosis earlier increased the project’s NPV by R$ 2.7 million (≈ US$ 0.77 million). Although feedlot and supplementation represent 65% of production costs, obtaining reasonable growth rates by providing animals with proper feeding improved the NPV significantly. Finally, after analyzing the effect of historical prices of the main inputs in the system, we concluded that the cost of inputs affects the performance of the enterprise the most.

The objective of this study was to develop a simulation model to analyse the technical, economic, and financial performance of using different reproductive strategies in dairy herds. Strategies simulated were: artificial insemination (AI) using conventional semen after oestrus detection (AIC), AI using sex-sorted semen after oestrus detection (AIS), timed artificial insemination (TAI) using conventional semen (TAIC), and TAI using sex-sorted semen (TAIS). The total time horizon analysed corresponded to 25 years, divided into 425 periods of 21 days. The model simulates the biological cycle that takes place within the bovine herd, and uses input information (productive parameters, investments, and reproductive program) to calculate output information (animal inventory variance, incomes, costs, and cash flow analysis). Based on the obtained cash flow, the payback period, net present value, and internal rate of return were calculated.