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Crossbred Angus cow–calf pairs (n = 28 pairs) at the Central Grasslands Research Extension Center (Streeter, ND) were used to evaluate an electronic feeder to monitor individual mineral intake and feeding behavior and their relationship with growth performance and liver mineral concentrations. Cows and calves were fitted with radio frequency identification ear tags that allowed access to an electronic feeder (SmartFeed system; C-Lock Inc., Rapid City, SD) and were provided ad libitum minerals (Purina Wind and Rain Storm, Land O’Lakes, Inc., Arden Hills, MN). Mineral intake, number of visits, and duration at the feeder were recorded over a 95-d monitoring period while pairs were grazing native range. Liver biopsies were collected from a subset of cows on the final day of monitoring and analyzed for mineral concentrations. Data were analyzed with the GLM procedure in SAS for mineral intake and feeding behavior with age class (cows vs. calves), intake category (high vs. low), and the interaction between class and category in the model. Correlations were calculated among cow feeding behavior and calf intake and growth performance with the CORR procedure, and a comparison of liver mineral concentrations among cows of high (>90 g/d; average 125.4 g/d) and low (50 g/d; average 72.2 g/d) consumed greater (P < 0.001) amounts of minerals than low-intake calves (

Three experiments were conducted to evaluate supplementation strategies for beef cattle grazing in the Northern Great Plains. In experiment 1, 28 cow-calf pairs had access to electronic feeders (SmartFeed system; C-Lock Inc., Rapid City, SD) that monitored individual vitamin and mineral supplement (VTM) intake. Cows had greater VTM intakes (81.1 ± 8.2 g/d; P < 0.01) than calves (44.2 ± 8.6 g/d) but both attended feeders a similar (P = 0.71) proportion of days. Furthermore, we noted greater (P < 0.01) concentrations of Se, Cu, and Co in livers of HIGH intake cows compared to LOW intake cows. Experiment 2, we used the SmartFeed system to regulate intake of individual heifers (n = 60) in a group pasture scenario assigned to control (CON), VTM, or energy supplement (NRG) treatments, and evaluated supplement intake, and concentrations of liver mineral and metabolites. Though no differences were observed in BW and ADG, treatments that provided VTM enhanced liver concentrations of Se, Fe, Cu, and Co (P < 0.05). No differences (P = 0.85) were observed in concentrations of NEFA; however, NRG heifers had greater (P = 0.01) glucose concentrations than CON and VTM heifers. Experiment 3 objectives were to determine the influence of feeding VTM and NRG supplements to beef heifers (n = 35) during the first 84 days of pregnancy on concentrations of progesterone (P4), corpus luteum (CL) size and fetal body measurements. Providing NRG during early gestation resulted in heavier CLs (P = 0.003) that produced more P4 (P = 0.002) and greater fetal femur growth (P = 0.009) whereas providing VTM enhanced fetal liver growth (P = 0.05). Overall, we were able to successfully monitor and control individual mineral intake, corroborated those differences in liver mineral concentrations, and observed alterations in fetal growth after mineral and energy supplementation.

Daily sperm production in bulls is determined by the size of the testicular Sertoli cell (SC) population established before puberty. Fine needle aspiration (FNA) is currently used as a diagnostic tool, but its value to determine SC and germ cell (GC) counts remains unexplored. The objectives were to compare three sampling techniques [(smears produced via 22G fine needle aspiration (SMR) vs. tissue sections collected via 14G aspiration (FNS) vs. conventional tissue sections (HIS)] and two stains [immunohistochemistry with GATA4 (IHC) and HE] to determine SC density in prepubertal bulls. Fourteen age-matched Angus bulls were surgically castrated. Testicular parenchyma samples and smears were stained using anti-GATA4 as a specific SC marker and HE. For stain comparison, mirrored tissue cuts were produced allowing cell counts of complementary seminiferous tubule (ST) cross sections. All data were analyzed using Pearson’s product moment correlations and linear regression. Testicular weights were correlated with IHC SC density (P = 0.018). High correlations existed for SC and GC counts done on ST cross sections using IHC (P < .0001) and HE (P < .0001). Within HIS and FNS, high correlations (r = 0.955; P ≤ 0.0001) existed between SC and automated GATA4+ cell densities. However, when comparing IHC SC density across techniques, no significant correlations (P ≤ 0.587) existed. The high correlation observed between SC counts done on mirrored ST cross sections for HE and IHC underlines the value of GATA4 as a specific SC marker in prepubertal bulls. Furthermore, the high correlation established between SC and GATA4+ cell densities within IHC HIS and FNS collection methods infers SC density determination can be automated. However, lack of correlation for SC density among techniques indicates that aspiration and conventional methods lead to different results. Research supported by North Dakota EPSCoR Doctoral Dissertation Assistantship (DDA) program.