Factors important for bull purchasing decisions and management in extensive rangeland production systems of New Mexico: a producer survey

There were 463,000 head of beef cows in New Mexico as of January 1, 2021 (NASS, 2020), down roughly 4% from 2020 (NASS, 2019). Frequent drought often results in herd reduction and loss of valuable genetic progress. Bull selection is critical due to their influence on herd development. A survey was conducted to identify traits important to bull selection in New Mexico. Surveys were collected digitally (n = 83) and via the mail (n = 74). Responses were largely by cow/calf producers averaging 57 ± 1 years old with 24 ± 1 years' experience. Survey respondents represented 4,384,296 acres of private owned, private leased, and leased public rangeland and irrigated pasture meadow in New Mexico and surrounding states. Average cow/calf operation size was 294 ± 39 head and average bull herd size was 21 ± 3 head. Average price paid for a bull in the past 2 years was $3,981 ± 213. Physical characteristics, individual bull performance information, and genetic information are all important traits to New Mexico bull buyers; however, most producers (56%) indicated that structural soundness was the most important factor influencing their selection decisions. Amongst expected progeny differences (EPDs), New Mexico producers consider the calving ease direct (CED) and birth weight (BW) EPDS to be most important (40% and 35%, respectively). Producers also indicated that multitrait selection indexes used by the American Angus Association were important to their selection decisions, with the beef value ($B) and weaned calf value ($W) indexes being cited most often (35% and 31%, respectively). Elements important to bull purchase include the bull's sale preview (87%), body condition score (86%), feed efficiency/average daily gain information (85%), and actual scrotal circumference (82%). Following purchase of a new bull, most (60%) keep the bull separate from the cow herd until the following breeding season, while the remaining 40% of producers turn newly purchased bulls out within 30 days of purchase. Sixty eight percent of producers evaluate semen quality annually or prior to the start of the breeding season. Interestingly, 39% of producers indicated they used reproductive technologies like artificial insemination and synchronization of estrus while most (80%) test for trichomoniasis. The primary factor influencing culling decisions is age, followed by soundness and fertility.

PSI-31 Retrospective analysis of growth performance and carcass ultrasound data of yearling bulls enrolled at the Cal Poly Bull Test

Since 1956, the Cal Poly Bull Test has evaluated performance of yearling bulls in a multi-breed contemporary group in the western United States. The main objectives of this study were to evaluate the consistency of the relationship between growth and ultrasound traits and between the number of bulls selling and sale price over a 19-year period from 2001–2019. Out of 3,712 bulls, a total of 2,503 Angus and 453 Hereford bulls were used in the analyses using SAS. Bulls were sold in the following pre-determined breed categories; Angus Heifer Bulls, Multi-Trait Angus Bulls, Growth Angus Bulls, and Hereford Bulls. The breed × year interaction significantly (P < 0.01) affected sale price, scrotal circumference (SC), ultrasound ribeye area (UREA), ultrasound intramuscular fat percentage (UIMF), end weight, and average daily gain (ADG). Overall, Hereford bulls had significantly (P < 0.0001) lower ADG than Angus bulls. A positive relationship between ADG and UREA (P < 0.0001; r2 = 0.10) and between UREA and SC (P < 0.0001; r2 = 0.05) was observed. A significant, positive relationship (P < 0.01; r2 = 0.24) between end weight and REA was also exhibited. A significant breed × year interaction (P < 0.01) was observed for sale price, wherein Angus heifer bulls consistently sold for the highest price. Additionally, sale price analyses indicated a moderate, negative relationship (P = 0.02; r2 = -0.584) between number of animals entered in the sale and price. Consistently, Angus bulls had higher (P < 0.0001) sale prices. Sales with higher bull numbers were those with the lowest average prices. The year and breed category explained 31 and 22.5 % of the variance in the price, respectively. Growth performance and sale price may have a biological or genetic component as indicated by breed differences consistently over the 19-year period.

PSI-39 Retrospective analysis of semen quality attributes of bulls in the Cal Poly Bull Test

The Cal Poly Bull Test has been offering valuable information for genetic improvement via a performance test of yearling beef bulls across the western United States since 1951. Growth and reproductive performance phenotypes were measured and collected over time. Therefore, the objective of this study was to determine the relationship between growth traits and semen quality traits. Performance records and semen samples of Hereford and Angus bulls were collected over a 12-year span from 2001–2013. A total of 1,982 records from Angus (n = 1692) and Hereford (n = 290) bulls were analyzed. All bulls were fall-born and weaned prior to the start of test in May. Bulls were fed for 99.83 ± 0.37 days in accordance with the guidelines of the Beef Improvement Federation where growth performance was assessed monthly during that period. After the conclusion of the test, usually in August, semen was collected from bulls and assessed for sperm motility, morphology and total sperm count. Bulls were retrospectively classified as low (0–1.4 kg), moderate (1.4–1.8 kg), or high (1.8–2.7 kg) average daily gain (ADG) bulls. The correlation among traits was evaluated using Pearson correlation, whereas a linear mixed model was used to evaluate the effect of growth on semen quality attributes. Bull age was moderately, negatively correlated (P < 0.01, r2 = -0.3) with scrotal circumference. Sperm motility and morphology were moderately correlated (P < 0.01, r2 = 0.35). Bull ADG was not strongly correlated (P < 0.01, r2 = 0.15) with semen motility or morphology. The results indicated a significant breed effect (P < 0.01) on semen motility and morphology. Angus bulls had a higher percent of progressively motile spermatozoa (P < 0.01; 72.23% ± 0.73) when compared with Hereford bulls (65.88% ± 1.37). Additionally, Angus bulls had a higher percentage of morphologically normal sperm (P < 0.01; 73.65% ± 0.59) when compared with Hereford bulls (66.29% ± 1.1). However, ADG as a class variable had no impact (P ≥ 0.50) on semen motility or morphology. Thus, these results indicate that higher levels of ADG during the testing period did not negatively impact semen quality attributes. More data must be collected to assess the biology behind the breed effects and validate the effect of body weight gain on semen quality attributes.

PSI-34 Factors influencing bull selection and management in extensive rangeland production systems of California

California’s 660,000 head of beef cattle are highly dependent on bulls used to produce offspring that can perform across the state’s diverse ecological regions. Bulls need to be functional on rugged coastal landscapes, rolling foothills, deserts and in high-elevation terrain. Few data exist that indicate factors related to selection, maintenance and longevity of bulls used in rangeland landscapes. Objectives herein, were to assess factors influencing bull purchasing, management, and culling decisions of California beef producers. Surveys were mailed to the California Cattlemen’s Association membership (n = 1,410) with ~ 12% response rate (n = 171). Data were analyzed for 56% of respondents (n = 95). Mean age and years of bull selection experience of respondents was 61 ± 1 years and 27 ± 2 years, respectively. Respondents managed cattle on a total of 694,949 ha of owned, private leased, and leased public rangelands in California and surrounding states. Cow-calf herd size was 378 ± 92 head and bull battery averaged 18 ± 3 head with average bull longevity of 5 ± 0.8 years. The average price paid for bulls in the last 2 years was $5166 ± 298, while the highest price paid in the last 5 years was $6958 ± 445. Survey responses were used to define current factors driving management after purchase and for subsequent breeding seasons. Methodology for bull turnout management (i.e. high-energy diet, pasture, supplemental hay) had no impact (P = 0.13) on average age of bulls when culled. After bull purchase, 46% of producers turned bulls out directly with females, while 49% held bulls until the following breeding season. Additionally, most producers (75%) did not manage bulls to reduce condition after purchase. Average bull longevity was moderately correlated (P = 0.01; r2 = 0.30) with average bull price a producer was willing to pay. The average age of bulls when culled was not influenced (P = 0.42) by the frequency of semen quality evaluation. Semen quality was evaluated annually by 45% of respondents, while 20% of respondents never evaluated semen quality. Respondents indicated bull age (35%) and structural soundness (29%) as the most common factors for culling bulls. This research suggests the need for additional research focused on bull selection and management to maximize producer investment in reproduction.

PSI-35 Foot and hair shedding scores of crossbred cattle grazing native rangeland differ by age group

Structural soundness is crucial to improve productivity and longevity of beef cattle in rangeland landscapes. In addition, hair shedding scores are utilized to select for heat tolerant cattle. Thus, the objective of this study was to collect data indicative of cattle adaptability to extensive rangeland landscapes in the Cal Poly beef cattle herd. Three trained technicians assigned claw set, foot angle and hair shedding scores. All data were collected over a 2-day period (n = 3 ranch locations) and foot scores were only collected from females (n = 211) that were at least 1 year of age. Each female was assigned a score for foot angle and claw set (1–9, 5 being ideal). A hair shedding score was also allocated (1–5, 1 = 0% winter coat, 5 = 100% winter coat) to both cows and calves of dams assigned to different age groups. Cattle were retrospectively assigned to a group based on age (Young = 2–3 years of age, Moderate = 4–7 years of age, Old = 8+ years of age) and data were analyzed with the main effects of ranch location and cow age group. Ranch location had no impact (P > 0.05) on foot score or hair shedding score. Cow age group had a significant impact (P < 0.01) on claw set, with young cows exhibiting a lower and more ideal foot score. However, cow age had no effect on hoof angle (P = 0.23). Young cows had a greater (P < 0.001) hair shedding score than their counterparts. Calf hair shedding score was not different (P ≥ 0.23) among dam age groups or ranch locations. Thus, these data indicate that feet and leg structure is compromised as cows age, and younger cows with higher hair shedding scores may lack adaptability to heat stress.

Effect of forage species and supplement type on rumen kinetics and serum metabolites in growing beef heifers grazing winter forage

The objective of this study was to determine the effect of stockpiled forage type and protein supplementation on VFA production, serum metabolites, and BW in yearling beef heifers. Over 2 yr, spring-born, Angus crossbred yearling beef heifers ( = 42; 305 ± 2.9 kg initial BW) were randomly assigned to 1 of 3 forage pasture types: 1) endophyte-infected tall fescue [TF; (Schreb.) Dumort], 2) a big bluestem ( Vitman) and indiangrass ( L.) combination (BI), or 3) switchgrass (SG; L.). Each pasture was then randomly assigned to receive either 1 of 2 isonitrogenous CP treatments: 1) 0.68 kg·heifer·d of dried distiller's grains with solubles (DDGS; 28% CP and 88% TDN) or 2) 0.22 kg·heifer·d of blood meal and fish meal (BF; 72.5% CP and 69.5% TDN), resulting in a 3 × 2 factorial arrangement of treatments. Treatments were initiated in January and terminated in April in both years of the study. Body weights and blood samples were collected approximately every 28 d from initiation of grazing until the end of the trial. Heifer BW change from January to February and overall BW change were greater ( < 0.01) for TF heifers. However, BW change from March to April was not different ( = 0.84) among forage types. Supplement type did not influence ( ≥ 0.13) BW or BW change from January to February and from January to April; however, heifers fed DDGS had greater ( = 0.03) BW gain from March to April. Heifer BW change from February to March exhibited ( < 0.05) a forage type × supplement interaction, with BF-fed heifers gaining more BW on BI pastures than DDGS-fed heifers. Serum glucose concentrations, ruminal acetate, and the acetate:propionate ratio were greater ( ≤ 0.04) for SG heifers. However, circulating serum NEFA and urea N (SUN) concentrations were not different ( ≥ 0.85) among forage types. Serum glucose and NEFA concentrations were not influenced ( ≥ 0.61) by supplement type. Circulating SUN concentrations were greater ( < 0.01) in BF-supplemented heifers. Ruminal acetate tended to be greater ( = 0.09) and butyrate concentrations were greater ( < 0.01) for BF-supplemented heifers. The acetate:propionate ratio was not influenced ( = 0.15) by supplement type. These results suggest that a compensatory gain period prior to breeding would be needed for these native warm-season species to be a viable opportunity for growing and developing replacement heifers in the southeastern United States.