PSII-12 Influence of Dietary Methionine and Guanidinoacetic Acid on Estrous Cycles and Early Pregnancy in Beef Heifers
Bibliographic record
Abstract
Abstract Interest is growing in methods to apply precision nutritional supplements strategically during the peri-conceptual period to enhance progeny performance of beef females. Studies where supplemental methionine (MET) was provided to bovine females in the peri-conceptual period demonstrated epigenetic modifications in muscle of the progeny. Guanidinoacetic acid (GAA) has been fed directly to livestock to increase creatine synthesis, but has not been evaluated for use in fetal programming. We fed MET and GAA to cross-bred heifers during the peri-conceptual period as a 2 x 2 factorial design to influence carcass characteristics of their steer calves. It was, therefore, important to determine if the interactions of dietary MET and GAA in the peri-conceptual period would alter reproductive efficiency. The null hypothesis was that these supplements would not alter reproductive efficiency of beef heifers when fed in the peri-conceptual period. Heifers were divided into four breeding groups for management purposes. On day -63, heifers (n = 20/diet, age = 384.1 ± 1.1 d) were assigned HeatTime collars and individually fed MET (10 g/d), GAA (40 g/d), the combination (MET + GAA), or ground corn carrier (CON) for 126 days. On day -9, heifers received 100 mg of gonadotropin releasing hormone and a CIDR. On day -2, the CIDR was removed and luteolysis was initiated with 25 mg of prostaglandin F2a. All heifers were inseminated with male sexed semen from a single sire and administered a second 100 mg injection of gonadotropin releasing hormone on day 0. On day 63, a blood sample was collected from all pregnant heifers (CON n = 10; MET n = 8; GAA n = 7; MET + GAA n =10) to evaluate circulating progesterone concentrations. Reproductive tracts were collected to determine CL weight, gravid uterine weight, and placentome number. Data were analyzed using the MIXED procedure of SAS with group, MET, GAA, and the interaction of MET and GAA as fixed effects. Days to first estrus were greater and number of estrus events prior to synchronization were fewer in CON heifers compared with supplemented heifers (P < 0.05). Luteal weight tended to be greater in heifers supplemented with MET compared with CON and GAA heifers (P = 0.09), but peak intensity of estrus, concentration of progesterone at day 63 of pregnancy, gravid uterine weight, and placentome number did not differ due to diet (P > 0.10). Supplementation with MET or GAA may improve onset of puberty but does not negatively alter reproductive performance in cross-bred beef heifers. These supplements can be used for fetal programming of muscle development in steer progeny without negatively impacting reproductive performance in the breeding herd. USDA is an equal opportunity provider and employer. Funded in part by USDA-NIFA-AFRI # 2022-67015-36196.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".