Accurate ultrasonographic prediction of progesterone concentrations greater than 1 ng/ml in Holstein lactating dairy cows

Heat stress during critical windows of the estrous cycle and risk of pregnancy establishment in embryo-recipient dairy heifers

This study aimed to determine effects of exposure of recipient dairy heifers to heat stress (THI≥ 73) during the estrous cycle coinciding with embryo transfer (ET) on the risk of pregnancy establishment after transfer of in vivo produced embryos. Recipients exposed to THI values ≥ 73 during days zero (recipient estrus), 7 (day of ET), 14 (seven days after ET), 15 and 16 (maternal recognition of pregnancy) of the ET cycle were considered as heat stressed heifers (n=254), while heifers in the control group (n=470) were not exposed to THI≥ 73 at any of the previous days. Results revealed no significant effects of any of the investigated factors on the risk of pregnancy following ET. However, the mean THI above 77 was associated with a drastic numerical decrease in PR/ET (36.63%), when compared to a mean THI 72 (78.78%). In addition, PR/ET after transfer of second and third grade embryos were numerically lower in heat-stressed recipients, compared to first grade embryos (41.17 vs 56.36%, respectively). Our findings confirmed that transfer of blastocysts were associated with numerically higher PR/ET in heat stressed and control recipients, as compared to morula stage. Interestingly, PR/ET tended to be higher when sexed embryos were transferred to the control recipients compared to heat-stressed ones. In conclusion, PR/ET in dairy heifers was not significantly affected by heat stress during critical windows of their estrous cycle coinciding with ET, whereas transfer of sexed embryos gives lower results under conditions of heat stress.

Site of PGF2α injection does not alter effectiveness of the Select Synch + controlled internal drug release and timed artificial insemination protocol

Beef Quality Assurance programs have contributed to significant improvements in the wholesomeness of beef available for consumption. Injection site blemishes in the round have declined since the promotion of administering intramuscular injections in the neck. Unfortunately, many producers continue to administer estrus synchronization (ES) drugs in the rump. The objective of this study was to compare the effectiveness of injection site of PGF_2α, in ES protocols, on steroid hormone concentrations and pregnancy rates. A Select Synch + 7-day controlled internal drug release ES protocol was conducted with the site of PGF_2α injection alternated between neck and rump in beef cattle (n = 312) at the Ohio State University Agricultural Technical Institute and North Carolina State University. Blood samples (n = 75) were collected at controlled internal drug release insertion and at the time of artificial insemination (AI) to determine if progesterone (P4) and estrogen (E2) concentrations varied due to PGF_2α injection site. All cattle were confirmed pregnant by ultrasonography at approximately 30 and 90 days after insemination in North Carolina and approximately 70 days after insemination in Ohio. Data were analyzed as randomized complete block designs in PROC GLIMMIX with animal as the experimental unit. Differences were declared significant at P < 0.05. Site of PGF_2α injection, in either the neck or rump, did not affect (P > 0.05) overall conception rates in response to AI (58.4% and 55.6%, respectively). Altering PGF_2α injection site did not impact P4, E2 concentrations, or the P4:E2 ratio at AI (P > 0.05). However, cattle inseminated after displaying estrus had greater (P < 0.05) pregnancy rates than timed AI (67.8 vs. 47.5%, respectively). First service conception rates and pregnancy rates were consistent with previous reports. Overall, altering the location of the PGF_2α injection during ES did not change circulating hormone concentrations at AI or pregnancy rates; therefore, cattle producers should follow Beef Quality Assurance guidelines when administering ES protocols.