Evaluation of age, weaning weight, body condition score, and reproductive tract score in pre-selected beef heifers relative to reproductive potential.

BACKGROUND: Artificial insemination is a preferred breeding method for beef heifers as it advances the genetic background, produces a predictive and profitable calving season, and extends the heifer's reproductive life span. As reproductive efficiency in heifers is key for the success of beef cattle production systems, following artificial insemination, heifers are exposed to a bull for the remainder of the breeding season. Altogether, up to 95% of heifers might become pregnant in their first breeding season. Heifers that do not become pregnant at the end of the breeding season represent an irreparable economical loss. Additionally, heifers conceiving late in the breeding season to natural service, although acceptable, poses serious losses to producers. To minimize losses due to reproductive failure, different phenotypic parameters can be assessed and utilized as selection tools. Here, we tested the hypothesis that in a group of pre-selected heifers, records of weaning weight, age at weaning, age at artificial insemination, and age of dam differ among heifers of varied reproductive outcomes during the first breeding season. RESULTS: None of the parameters tested presented predictive ability to discriminate the heifers based on the response variable ('pregnant to artificial insemination', 'pregnant to natural service', 'not pregnant'). Heifers categorized with body condition score = 6 and reproductive tract score ≥ 4 had the greatest proportion of pregnancy to artificial insemination (49% and 44%, respectively). Furthermore, it was notable that heifers presenting body condition score = 6 and reproductive tract score = 5 presented the greatest pregnancy rate at end of the breeding season (89%). Heifers younger than 368 d at the start of the breeding season did not become pregnant to artificial insemination. Those young heifers had 12.5% chance to become pregnant in their first breeding season, compared to 87.5% if the heifers were older than 368 days. CONCLUSION: Our results suggest that beef heifers with body condition score = 6 and reproductive tract score ≥ 4 are more likely to become pregnant to artificial insemination. Careful assessment should be undertaken when developing replacement heifers that will not reach 12 months of age by the beginning of the breeding season.

Plasma metabolomic profiles differ at the time of artificial insemination based on pregnancy outcome, in Bos taurus beef heifers.

Infertility remains the most prevalent reason for cattle being removed from production environments. We utilized metabolomic profiling to identify metabolites in the blood plasma that may be useful in identifying infertile heifers at the time of artificial insemination (AI). Prior to AI, phenotypic parameters including body condition, weight, and reproductive organ measurements were collected. These were determined not effective at differentiating between fertile and infertile heifers. Analysis of the resulting metabolomic profiles revealed 15 metabolites at significantly different levels (T-test P ≤ 0.05), with seven metabolites having a greater than 2-fold difference (T-test P ≤ 0.05, fold change ≥2, ROC-AUC ≥ 0.80) between infertile and fertile heifers. We further characterized the utility of using the levels of these metabolites in the blood plasma to discriminate between fertile and infertile heifers. Finally, we investigated the potential role inflammation may play by comparing the expression of inflammatory cytokines in the white blood cells of infertile heifers to that of fertile heifers. We found significantly higher expression in infertile heifers of the proinflammatory markers tumor necrosis factor alpha (TNFα), interleukin 6 (IL6), and the C-X-C motif chemokine 5 (CXCL5). Our work offers potentially valuable information regarding the diagnosis of fertility problems in heifers undergoing AI.

Stockpiled "Tifton 85" bermudagrass for cow-calf production as influenced by nitrogen fertilization.

A 2-yr study was conducted to determine the effects of rate of N fertilization on productivity and nutritive value of stockpiled "Tifton 85" bermudagrass for lactating-cow and calf performance. On 31 October 2012 (year 1) and 11 November 2013 (year 2), 16 Angus × Simmental cows (mean initial BW for both years, 647 ± 23 kg) and their calves (mean age for both years, 16 ± 3 d) were assigned randomly to 0.76-ha paddocks (2 cow-calf pairs/paddock) of stockpiled "Tifton 85" bermudagrass pasture that had been cut to a 10-cm stubble height in early August and fertilized with either 56 (56N), 112 (112N), or 168 (168N) kg N/ha (2 paddocks/treatment), or to replicate 0.41-ha paddocks (2 cow-calf pairs/paddock) of dormant pasture with free-choice access to August-cut "Tifton 85" bermudagrass hay plus 2.7 kg whole cottonseed daily (HAY). Cows were allowed access to strips of ungrazed forage by moving polytape every 3 to 4 d to maintain a DM harvest efficiency of approximately 75%. In year 1, forage mass (6,113 kg DM/ha), IVDMD (60.9%), and grazing d/ha (314) were not different (P > 0.05) among the stockpile treatments over a 116-d grazing period; mean forage IVDMD (60.1%) and CP (12.7%) in the stockpiled treatments were greater (P < 0.05) than the HAY treatment. Stockpiled forage CP concentration was greater (P < 0.05) for the 168N than 56N and 112N treatments and was greater (P < 0.05) for the 56N than 112N treatment. In year 2, mean forage CP concentration was greater (P < 0.05) for the 168N (14.5%) than 56N (11.3%), 112N (12.0%), and HAY (9.0%) treatments; mean stockpiled forage IVDMD (59.5%) was greater (P < 0.05) than the HAY treatment (46.3%); and mean forage mass for the 168N treatment (5,017 kg DM/ha) was 378 kg and 298 kg DM/ha greater (P < 0.05) than the 112N and 56N treatments, respectively. Mean cow BW (611 ± 147 kg), body condition scores (5.5 ± 0.6), and milk production (9.0 ± 6.0 kg/d) were not different (P > 0.05) among treatments. Mean blood urea-N (BUN) concentrations (11.2 mg/mL) were not different among treatments, but mean BUN across treatments for the last sampling date was greater (P < 0.05) than the first and second sampling dates. Mean 205-d adjusted weaning weight (249 kg ± SD) was not different among treatments. Economic evaluation revealed that input costs/cow were 66%, 61%, and 56% greater for HAY than 56N, 112N, and 168N, respectively. Stockpiled forages were of sufficient nutritive quality to support lactation without supplementation.

Transcriptome profiles in peripheral white blood cells at the time of artificial insemination discriminate beef heifers with different fertility potential.

BACKGROUND: Infertility is a longstanding limitation in livestock production with important economic impact for the cattle industry. Female reproductive traits are polygenic and lowly heritable in nature, thus selection for fertility is challenging. Beef cattle operations leverage estrous synchronization in combination with artificial insemination (AI) to breed heifers and benefit from an early and uniform calving season. A couple of weeks following AI, heifers are exposed to bulls for an opportunity to become pregnant by natural breeding (NB), but they may also not become pregnant during this time period. Focusing on beef heifers, in their first breeding season, we hypothesized that: a- at the time of AI, the transcriptome of peripheral white blood cells (PWBC) differs between heifers that become pregnant to AI and heifers that become pregnant late in the breeding season by NB or do not become pregnant during the breeding season; and b- the ratio of transcript abundance between genes in PWBC classifies heifers according to pregnancy by AI, NB, or failure to become pregnant. RESULTS: We generated RNA-sequencing data from 23 heifers from two locations (A: six AI-pregnant and five NB-pregnant; and B: six AI-pregnant and six non-pregnant). After filtering out lowly expressed genes, we quantified transcript abundance for 12,538 genes. The comparison of gene expression levels between AI-pregnant and NB-pregnant heifers yielded 18 differentially expressed genes (DEGs) (ADAM20, ALDH5A1, ANG, BOLA-DQB, DMBT1, FCER1A, GSTM3, KIR3DL1, LOC107131247, LOC618633, LYZ, MNS1, P2RY12, PPP1R1B, SIGLEC14, TPPP, TTLL1, UGT8, eFDR≤0.02). The comparison of gene expression levels between AI-pregnant and non-pregnant heifers yielded six DEGs (ALAS2, CNKSR3, LOC522763, SAXO2, TAC3, TFF2, eFDR≤0.05). We calculated the ratio of expression levels between all gene pairs and assessed their potential to classify samples according to experimental groups. Considering all samples, relative expression from two gene pairs correctly classified 10 out of 12 AI-pregnant heifers (P = 0.0028) separately from the other 11 heifers (NB-pregnant, or non-pregnant). CONCLUSION: The transcriptome profile in PWBC, at the time of AI, is associated with the fertility potential of beef heifers. Transcript levels of specific genes may be further explored as potential classifiers, and thus selection tools, of heifer fertility.

Effect of premedication and other factors on the occurrence of acute transfusion reactions in dogs.

OBJECTIVE: To evaluate the effect of premedication on transfusion reactions (TRs) within 24 hours after blood product transfusions in dogs. DESIGN: Retrospective study between 2008 and 2011. SETTING: Private veterinary referral hospital. ANIMALS: Nine hundred and thirty-five transfusion events in 558 dogs. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Medical records of dogs receiving blood product transfusions were reviewed. Information collected included signalment, weight, transfusion product type, reason for transfusion, first or subsequent transfusion, whether an acute reaction occurred, type of reaction, whether the reaction was treated, premedication prior to the transfusion and the premedication used, other medications the animal was given, whether the animal had an immune-mediated process, and whether the transfusion was administered in the perioperative period. A total of 144 (15%) acute TRs were documented in 136 dogs. The most common TRs were fever alone (77/144 [53%]) and vomiting alone (26/144 [18%]). Six dogs died due to the TR (4%). TR was not associated with age (P = 0.257), sex (P = 0.754), weight (P = 0.829), or premedication (P = 0.312). The type of blood product transfused (P < 0.001) was significantly associated with TRs, with packed RBCs most likely associated with a TR, and plasma least likely. Immune disease (P = 0.015) was significantly associated with occurrence of a TR. Significantly fewer reactions were documented following transfusions given in the perioperative period (P = 0.023). CONCLUSIONS: While most TRs were mild, there were some serious reactions observed including hemolysis, dyspnea, and 6 deaths. Immune-mediated disease was associated with development of a TR, while transfusion during the perioperative period was associated with lower likelihood of reaction. Packed RBC transfusions were associated with development of acute TRs. Overall occurrence of TR was not significantly altered with premedication; however, when evaluated alone, antihistamines decreased the incidence of acute allergic reactions.