While genetics are an unreliable indicator of fertility, antral follicle count (AFC) has recently been recognized as a useful fertility prediction tool in heifers. The aim of this study was to determine if AFC exerts an effect on response to synchronization, time to estrus (TTE), and/or time to ovulation (TTO). Twenty-five crossbred heifers were classified by AFC, either high (> 25 antral follicles), moderate (16–24 antral follicles), or low (< 15 follicles) and utilized in two experiments. In experiment 1, heifers were subjected to the Select Synch + CIDR fixed time artificial insemination (FTAI) protocol. After synchronization, estrus activity was monitored every 3 h until standing estrus was observed. Heifers were examined at 12 and 18 h after observation of standing estrus and every 3 h thereafter to monitor ovulation. In experiment 1, the proportion of heifers that responded to the protocol was not significant (P = 0.71) among classification groups. Time to estrus and time to ovulation were similar between groups (P > 0.90). In experiment 2, heifers were placed with bulls for 60 d and were monitored for signs of estrus every 3 h. Results of experiment 2 indicated that response to estrus synchronization was similar across groups (P = 0.46). Time to estrus was greater (P = 0.04) in the high AFC group than in the low or moderate AFC groups. This may be attributed to lower concentrations of circulating gonadotropins in high AFC heifers, resulting in decreased intrafollicular estradiol. Differences in TTE results between experiment 1 and experiment 2 may be explained by increased reproductive function as heifers continued to mature during the study. These results suggest that differences in TTE may be related to AFC. Additional research is needed to corroborate these results and inform the creation of differing FTAI protocols based on AFC.

Dormant forage at weaning in Southwestern rangelands may not be nutritionally sufficient to support growth potential of calves administered a growth promoting implant. Therefore, the objective of this study was to investigate the influence of level of supplementation when heifers were administered a Synovex-C implant at weaning on growth and antral follicle counts (AFC). At weaning (8 months old), heifers (n = 17) were stratified by bodyweights (BW) and AFC and assigned to receive one of two levels of supplement (High or Low) and implant (Implant and No Implant; all heifers received a Synovex C implant at 2 months old). Heifers assigned to the Implant group received a second Synovex-C implant at weaning, thus creating four treatment groups: High Implant (n = 4), High No Implant (n = 4), Low Implant (n = 5), and Low No Implant (n = 4). Heifers were utilized in a complete randomized block design with a 2 x 2 factorial. Heifers were individually fed supplement three times a week for 26 weeks with refusals being weighed after each feeding to determine intake. During the receiving phase High and Low heifers were offered 1.94 kg/h/d and 1.17 kg/h/d, respectively, of 20% CP cube for the first 4 weeks of the study. After acclimation High and Low heifers were offered 1.26 kg/h/d and 0.68 kg/h/d, respectively, of 32% CP cube for the remainder of the study. Biweekly BW and monthly body condition scores (BCS) were recorded. Prior to the start of the project and 45 d before the breeding season, AFC were conducted via transrectal ultrasonography. Average daily gain (ADG), BW, and BCS were analyzed as repeated measures in SAS (PROC MIXED). Antral follicle counts were analyzed using MIXED procedures in SAS. Implant, supplement level, implant × supplement level, and implant × supplement level × week did not impact BW or BCS (P ≥ 0.22). Week (P < 0.0001), implant × week (P < 0.0004), and supplement level × week (P < 0.0001) impacted BW. Week (P < 0.0001), implant × week (P = 0.008), and supplement level × week (P = 0.0005) influenced ADG. Implant heifers tended to have increased ADG (P < 0.09) and High Implant heifers tended to have increased ADG compared to the other implant x supplement level treatments (P ≤ 0.09). Body condition score was significantly different across weeks (P < 0.0001). There was no difference between week (P = 0.64) on AFC. Implant (P > 0.22), supplement level (P > 0.43), and implant x supplement level (P > 0.80) did not influence AFC. In conclusion, administration of a second Synovex-C implant at weaning did not impact AFC and feeding implanted heifers at a higher supplementation level tended to improve ADG.

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.