Assessment of semen quality and fertility in young growing beef bulls exposed to ergot alkaloids.

The objective of this study was to evaluate semen quality and fertility in beef bulls grazing the ergot alkaloid (EA) producing tall fescue cultivar, Kentucky 31 (KY31), compared to a novel endophyte (NE) cultivar lacking EA. Two studies were conducted over a 3-year period. In studies 1 (n = 10; ages ≥ 24 mo) and 2 (n = 53 over two years; ages 12-16 mo), Angus (AN) bulls were stratified by body weight (BW), body condition score (BCS), and scrotal circumference (SC), and then allotted to graze either KY31 or NE for 56 days. Semen samples were collected, and BW, BCS, and SC were evaluated at the start of treatment (TRT) on day (d) 0 and every 28 days to the end of each study. In addition, blood samples were collected on d 0 and every 28 days for assessment of circulating prolactin (PRL) levels in study 2. On d 56, for both studies, semen from bulls (n = 2 per treatment in study 1 and n = 4 per treatment in study 2) with similar and acceptable quality were extended, kept at 19° C, and used for timed artificial insemination (TAI) of primi- and multiparous AN and AN- crossbred females. Pregnancy was evaluated at 35 and 90 days post-TAI via transrectal ultrasonography to determine pregnancy rates. Serum PRL concentrations showed a TRT by d effect (P ≤ 0.05), with values for bulls grazing KY31 decreased on d 28 and d 56 of grazing compared to NE. In studies 1 and 2, bull BW and BCS were affected by d (P ≤ 0.05), but not by TRT. No TRT or TRT by d effect on semen quality was observed in either study; however, d impacted both velocity and concentration in study 2 (P ≤ 0.05). In study 1, TAI pregnancy rates at 35 days post-TAI were lower (P ≤ 0.05) in the group inseminated with semen from bulls grazing KY31; however, in study 2, pregnancy rates did not differ due to treatment 35 post-TAI (P > 0.05). Grazing KY31 negatively impacted serum PRL concentrations, supporting previous observations; however, consumption of KY31 had no effect on growth or semen quality of AN bulls ranging from 12 to ≥24 mo of age. Furthermore, fertility data is inconsistent between studies and requires further investigation.

The effect of supplementing rumen undegradable unsaturated fatty acids on marbling in early-weaned steers.

The objective of this study was to determine if supplementation with a rumen undegradable unsaturated fatty acids (FA) source improved marbling deposition in early-weaned steers. All steers (Angus, = 23; Angus × Hereford, = 24) were weaned at 150 ± 5 d of age. Steers were blocked by BW and breed and then randomly assigned to either control (CON; average 1.5 kg of corn gluten feed [CGF], = 23) or isocaloric supplementation containing a rumen undegradable fat source (RUF; 200 g of Megalac-R added to an average of 1.06 kg of CGF, = 24) offered 5 d/wk for 110 d. All steers had ad libitum access to pastures throughout treatment and received supplements individually. Steer BW and blood samples were collected at 0, 55, and 110 d of supplementation, and real-time ultrasound measurements were collected at d 110. Following treatment, steers were transported to Oklahoma State University for finishing and subsequent harvesting at a commercial plant. All data were analyzed using the PROC MIXED procedure of SAS either as repeated measures or ANOVA depending on parameters. There were no significant changes in BW from the beginning of treatment to harvest due to treatment. Ultrasound data showed that RUF steers tended ( = 0.08) to have more i.m. fat than CON at d 110. Serum concentrations of FA showed a treatment × day interaction ( < 0.02) for 16:0, 18:0, 18:1-9, 18:2, 20:4, and total FA. These specific FA concentrations slightly increased in CON steers, but there was a more pronounced increase in the concentration of these FA across the supplementation period in RUF steers. Serum triglyceride and cholesterol concentrations were increased ( < 0.01) on d 55 and 110 in RUF steers compared with those in CON steers. Serum leptin concentration in RUF steers was greater ( < 0.01) than CON steers at d 110. After harvest, RUF carcasses had greater ( = 0.01) marbling scores than those of CON carcasses. All other carcass measures were similar between treatments. The percentage of total lipids was increased ( = 0.011) in steaks from RUF compared to CON. There was a decrease ( < 0.05) in adipocyte diameter in i.m. fat depot of RUF steers compared to CON. There was also a tendency ( = 0.06) for RUF steers to have a greater percentage of 20 to 30 µm adipocytes in their i.m. depot than CON steers. This study indicates that supplementation of unsaturated FA can positively impact marbling deposition in early-weaned steers without impacting other carcass measures.