Interrelationships among plasma metabolites, production, and ovarian follicular function in dairy cows

Associations of blood metabolites and production variables with ovarian function and parity, specifically, interval to first ovulation (IFO) and the incidence of ovarian cysts (OC) and multiple ovulation (MOV) at the first ovulation postpartum, were determined in lactating dairy cows. This retrospective study involved data on 169 Holstein cows from 3 studies on the same herd. Blood samples were taken weekly from wk -1 to 4, relative to calving, and transrectal ultrasonography was performed twice weekly from d 7 to 60 postpartum. The overall IFO was 32.6 Âą 1.9 d [mean Âą SEM] and did not differ among lactations. Primiparous cows were at a greater risk of failing to ovulate before d 60 postpartum and cows in the 3rd or greater lactation were at a higher risk for OC and MOV. Blood metabolites and production variables indicating a negative energy balance were associated with cows failing to ovulate before d 35 postpartum, but were not related with OC. Increased DMI and milk yield, particularly in 2nd lactation cows, were associated with a higher incidence of OC. While BHBA and IGF-1 were associated with MOV, the relationship was weak. Reducing negative energy balance is necessary to reduce IFO but may increase the incidence of MOVThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Morphology, membrane integrity, and mitochondrial function in sperm of crossbred beef bulls selected for residual feed intake

The objectives of this study were to compare morphology, plasma and acrosome membrane integrities, and mitochondrial function in sperm of bulls selected for low- vs. high- residual feed intake (RFI). Semen samples obtained from 10 low- and 8 high-RFI yearling crossbred beef bulls were evaluated. Assessment of sperm morphology was performed by microscopy, and sperm membrane integrity and mitochondrial membrane potential were evaluated by flow cytometry. Parameters of sperm morphology evaluated did not differ between low- and high-RFI bulls. Compared to high-RFI bulls, low-RFI bulls had an increased proportion (LSM ± SE) of sperm with actively respiring mitochondria (54.2 ± 2.9 vs. 43.6 ± 3.3%, P = 0.03). However, a greater proportion of sperm from low-RFI bulls had low mitochondrial membrane potential (34.4 ± 4.2 vs. 19.0 ± 4.7%, P = 0.03). Results indicate that selection for improved feed efficiency do not compromise bull sperm morphology and viability. However, despite greater mitochondrial activity, the increased proportion of mitochondria with low membrane potential in sperm of low-RFI bulls warrants further investigation to rule out any potential negative effects on fertility.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author