Beef Production Systems in the Nebraska Sandhills

Four studies were conducted to determine the effectiveness of improving production systems of beef cattle in the Sandhills region of Nebraska. These studies were to determine impacts of modified estrus synchronization protocols, genomic testing heifer calves for longevity, and evaluation of 2 differing calving systems (March or May) for improving biological outcome and improved production. Experiment 1 utilized 180 yearling heifers to determine the effectiveness of a second dose of prostaglandin F2α(PGF) with those females not expressing estrus after an initial 14 d MGA-PG estrus synchronization protocol. The treatment of PGF did increase estrus expression, but did not increase the pregnancy success of these females. Experiment 2 utilized 1,518 yearling heifers in a 14 d MGA-PG estrus synchronization protocol. Treatment of 5 μg GnRH was administered 72 h prior to a fixed-time AI (TAI) simultaneous with the typical PGF administration (25mg). The dose of 5 μg GnRH did not increase pregnancy success for initial TAI when compared to the control females. Study 3 genotyped 414 March or May born heifers from the Gudmundsen Sandhills Laboratory from the years 2009-2012. Phenotypic data for each individual was compared to the genomic results from the Igenity Gold panel reported on a 1-10 scale. Regression analysis revealed the birth BW genomic score is a predictor for actual birth BW. The genomic score for calving-ease direct is also a predictor for weaning BW. The iii genomic predictor scores for heifer pregnancy as well as stayability show no significance as predictors for actual heifer pregnancy and female stayability. The final study compared the biological differences when calving in a March versus a May calving season. Data from 3 consecutive years were utilized with 503 cows from the March and 301 from the May systems. Calf birth BW and calf BW at dam’s breeding was greater for May-born calves than March-born. Adjusted weaning BW was greater for March-born. Pregnancy rates, weaning rates, calving interval, calving difficulty, and calf vigor were similar between the systems. Advisors: Richard N. Funston and James C. MacDonal

Understanding the Needs of Residents in Sevier County to Plan Impactful Programs

USU Extension provides evidence-based community education in response to community needs. A needs assessment was conducted in Sevier County UT in 2021 to determine critical needs of residents. The results of the assessment will guide Extension programming in Sevier County

Efficacy of a Second Injection of Prostaglandin F2α in Yearling Beef Heifers Following Previous Estrus Synchronization

Angus- based, yearling beef heifers were utilized to determine the effects of administering a second prostaglandin F2α (PGF; Lutalyse, Zoetis Animal Health, Parsippany, NJ) injection to heifers who did not previously respond to estrus synchronization. All heifers were exposed to a melengestrolacetate (MGA)- PGF protocol. Following PGF injection, heifers were observed for estrus (estrus detection patches rubbed) for 3 d and inseminated. Heifers who did not show signs of estrus were placed with fertile bulls. Aft er 3 d with bulls, heifers with greater than 50% of the rub- off coating removed from estrus detection aids were considered to have been bred. One- half of the heifers not showing estrus received a second PGF injection; the other half were the controls and received no further treatment. Heifers remained with bulls for 4 d. Percentage expressing estrus was greater for heifers receiving a second PGF injection. However, pregnancy rate was similar between treatments

Evaluation of Commercial Genomic Tests for Maternal Traits in Crossbred Beef Cattle

DNA samples were collected from beef heifers born at the Gudmundsen Sandhills Laboratory and analyzed with a genomic test. Phenotypic data from these females were compiled and used in a regression analysis to evaluate the utility of these genomic scores as predictors for phenotypic outcomes. Th e genomic score for birth body weight (BW) was signifi cantly associated with animal birth BW. Th e genomic score for heifer pregnancy was not a statistically significant predictor of actual pregnancy. Neither dam age or the genomic score for stayability were significant predictors of actual reproductive longevity

Effect of GnRH Injection at - 72 h in MGA- PGEstrus Synchronization Protocol

Yearling beef heifers from 2 locations were synchronized with melengestrol acetate (MGA)- prostaglandin F2α (PGF) fi xed time AI (TAI) protocol. At PGF administration 72 h before AI, heifers were randomly assigned to receive either 0 or 5 μg gonadotropinreleasing hormone (GnRH). Th e administration of 5 μg GnRH at PGF did not increase estrus activity or improve TAI pregnancy rates at either location (Location 1, 56% (GnRH) vs. 57%; Location 2, 59% (GnRH) vs. 53%). Administering GnRH at PGF increased (74% vs. 63%) pregnancy rates for heifers inseminated during a follow- up heat detection period at one location. A low dose of GnRH administered 72 h prior to AI in a 14 d MGA- PGF synchronization protocol does not increase pregnancy rates or estrus expression in yearling, beef females bred with TAI when compared to the normal MGAPGF synchronization protocol

Comparing March and May Calving Systems in the Nebraska Sandhills

Three production years for March and May calving, Red Angus- based cows and their off spring from the Gudmundsen Sandhills Laboratory (GSL), Whitman, NE, were evaluated. Steer progeny were evaluated through harvest and carcass data collected. Calf birth body weight (BW) and breeding BW were greater for May calves vs. March; however, adjusted weaning BW was greater for March calves. Pregnancy rates, weaning rates, calving interval, calving difficulty, and calf vigor were similar between calving systems. Udder score was greater for March cows. Compared with March calf- fed steers, May calf- fed steers had greater hot carcass weight (HCW), longissimus muscle area (LMA), marbling, and backfat. May yearlings had greater HCW, LMA, marbling, and backfat compared with March calf- feds. In the Sandhills, a May calving system can increase production while reducing total herd inputs when compared to a March calving system

Satellite Kinematics I: A New Method to Constrain the Halo Mass-Luminosity Relation of Central Galaxies

Satellite kinematics can be used to probe the masses of dark matter haloes of central galaxies. In order to measure the kinematics with sufficient signal-to-noise, one uses the satellite galaxies of a large number of central galaxies stacked according to similar properties (e.g., luminosity). However, in general the relation between the luminosity of a central galaxy and the mass of its host halo will have non-zero scatter. Consequently, this stacking results in combining the kinematics of satellite galaxies in haloes of different masses, which complicates the interpretation of the data. In this paper we present an analytical framework to model satellite kinematics, properly accounting for this scatter and for various selection effects. We show that in the presence of scatter in the halo mass-luminosity relation, the commonly used velocity dispersion of satellite galaxies can not be used to infer a unique halo mass-luminosity relation. In particular, we demonstrate that there is a degeneracy between the mean and the scatter of the halo mass-luminosity relation. We present a new technique that can break this degeneracy, and which involves measuring the velocity dispersions using two different weighting schemes: host-weighting (each central galaxy gets the same weight) and satellite-weighting (each central galaxy gets a weight proportional to its number of satellites). The ratio between the velocity dispersions obtained using these two weighting schemes is a strong function of the scatter in the halo mass-luminosity relation, and can thus be used to infer a unique relation between light and mass from the kinematics of satellite galaxies.Comment: 8 pages, 3 figures, MNRAS submitte

Satellite Kinematics II: The Halo Mass-Luminosity Relation of Central Galaxies in SDSS

The kinematics of satellite galaxies reflect the masses of the extended dark matter haloes in which they orbit, and thus shed light on the mass-luminosity relation (MLR) of their corresponding central galaxies. In this paper we select a large sample of centrals and satellites from the Sloan Digital Sky Survey (SDSS) and measure the kinematics (velocity dispersions) of the satellite galaxies as a function of the $r$-band luminosity of the central galaxies. Using the analytical framework presented in Paper I, we use these data to infer {\it both} the mean and the scatter of the MLR of central galaxies, carefully taking account of selection effects and biases introduced by the stacking procedure. As expected, brighter centrals on average reside in more massive haloes. In addition, we find that the scatter in halo masses for centrals of a given luminosity, $\sigma_{\log M}$, also increases with increasing luminosity. As we demonstrate, this is consistent with $\sigma_{\log L}$, which reflects the scatter in the conditional probability function $P(L_c|M)$, being independent of halo mass. Our analysis of the satellite kinematics yields $\sigma_{\log L}=0.16\pm0.04$, in excellent agreement with constraints from clustering and group catalogues, and with predictions from a semi-analytical model of galaxy formation. We thus conclude that the amount of stochasticity in galaxy formation, which is characterized by $\sigma_{\log L}$, is well constrained, is independent of halo mass, and is in good agreement with current models of galaxy formation.Comment: 17 pages, 12 figures, MNRAS submitte

Satellite Kinematics III: Halo Masses of Central Galaxies in SDSS

We use the kinematics of satellite galaxies that orbit around the central galaxy in a dark matter halo to infer the scaling relations between halo mass and central galaxy properties. Using galaxies from the Sloan Digital Sky Survey, we investigate the halo mass-luminosity relation (MLR) and the halo mass-stellar mass relation (MSR) of central galaxies. In particular, we focus on the dependence of these scaling relations on the colour of the central galaxy. We find that red central galaxies on average occupy more massive haloes than blue central galaxies of the same luminosity. However, at fixed stellar mass there is no appreciable difference in the average halo mass of red and blue centrals, especially for M* \lsim 10^{10.5} h^{-2} Msun. This indicates that stellar mass is a better indicator of halo mass than luminosity. Nevertheless, we find that the scatter in halo masses at fixed stellar mass is non-negligible for both red and blue centrals. It increases as a function of stellar mass for red centrals but shows a fairly constant behaviour for blue centrals. We compare the scaling relations obtained in this paper with results from other independent studies of satellite kinematics, with results from a SDSS galaxy group catalog, from galaxy-galaxy weak lensing measurements, and from subhalo abundance matching studies. Overall, these different techniques yield MLRs and MSRs in fairly good agreement with each other (typically within a factor of two), indicating that we are converging on an accurate and reliable description of the galaxy-dark matter connection. We briefly discuss some of the remaining discrepancies among the various methods.Comment: 19 pages, 14 figures, MNRAS submitted, comments welcom