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Apparent ruminal digestibility of forage soybean-based silages, with and without pearl millet, was determined along with evaluation of silages on heifer performance and reproductive function. Fermenters were utilized in a Latin square design and randomly assigned to 1 of the following treatments: 1) control diet of alfalfa haylage (CON), 2) soybean silage (SB) or 3) soybean and pearl millet silage (SB×PM). All diets were formulated to meet or exceed nutrient requirements of replacement beef heifers targeted to gain 0.79 kg/d. These same diets were fed to 90 Angus-Simmental beef replacement heifers [body weight (BW) = 366 kg; body condition score (BCS) = 5.53; age = 377 ± 11 d] 65 d prior to timed artificial insemination (TAI). Heifers were randomly allotted by breed, BCS and BW to 1 of the 3 treatments, with 3 reps/treatment. Diets were terminated 21 d post-TAI and heifers were commingled and placed on a common diet. Pubertal status was determined by progesterone concentrations of 2 blood samples taken 10 d apart prior to both trial initiation as well as initiation of estrous synchronization. Ovulatory follicle diameter was determined at time of breeding by ultrasonography. Pregnancy diagnosis was accomplished 35 and 66 d post-TAI, respectively, to calculate TAI and end of season pregnancy rates. Neither SB nor SB×PM had an effect ( P > 0.37) on apparent ruminal digestion of nutrients compared to the CON. Final BW (414 kg; P ≥ 0.10) and BCS (5.28; P ≥ 0.26) for the heifers were similar among treatments. Likewise, there were no differences in TAI (48%; P > 0.43) or overall breeding season (93%; P > 0.99) pregnancy rates. Ovulatory follicle diameters (11.7 mm) was not different ( P > 0.19) among treatments. In summary, forage soybean-based silages, with and without pearl millet, was an acceptable alternative forage for developing replacement beef heifers.

A 2*2 factorial arrangement of photoperiod treatments in autumn (A) and winter (W) was applied to spring-born crossbred beef heifers (N=540 over 6 yrs ) assigned at weaning (Sep; 0 wk), by body weight and age, to one of four pens in one of two similar open shed/drylot facilities. Supplemental light (350 lux, 1 m above ground) was used to extend photoperiod (natural + supplemental light) to 16 h for 12 wk starting in Sep (A), or Dec (W), or for both periods (AW), while the control group was exposed to natural photoperiod (NP) only. Heifers were fed diets formulated to achieve 60% mature body weight at 32 wk through one of three feeding strategies: low gain during the prepubescent (0.6 kg d-1; 4 to 16 wk), high gain during the pubescent (1.2 kg d-1; 16 to 24 wk) and moderate gain during the post-pubescent (0.7 kg d-1; 24 to 32 wk) period, or low, low, high and constant (0.9 kg d-1) gain throughout these periods, respectively. In May each year heifers were synchronized for fixed-time AI (0 d) followed by exposure to bulls (2-42 d) and turn-out. In the fall bred heifers continued in one management group. At 8 wks postpartum heifers were milked, separated from their calves and milk collected 8 h later used to determine yield and composition. Data were analyzed as a 2*2*3 factorial using Proc Mixed and included the random effect of year. Mean pre- and post- calving body weights and condition scores, and calf birth weight of milked heifers were similar (P>0.05) among treatments. Yield of milk (8.3±0.3, 8.3±0.2, 7.9±0.3 and 7.6±0.2 kg d-1), protein and solids not fat were greater for A- or W- than AWand NP treatments, respectively (P=0.05). Feeding strategy had no significant effect (P>0.05) on milk, body weight or condition. Extended photoperiod treatment during pubescence increased first lactation milk yield by 9.2%. [ABSTRACT FROM AUTHOR]

The experiment was desgined to characterize response after treatment with a 14-d CIDR insert (1.38 g progesterone) followed by GnRH (100 μg Cystorelin) and PG (25 mg Lutalyse) in 79 Angus crossbred heifers. Fifty-three heifers were pubertal (P) and 26 were prepubertal (PP) based on two blood samples for progesterone collected 10 d and 1 d prior to treatment. Mean ages and weights of the P and PP heifers were 405 and 411 d, and 382 and 386 kg, respectively. CIDRs were inserted in all heifers on the same day for 14 d, GnRH was injected on d 23, and PG on d 30. Estrus detection was performed continuously after CIDR removal using HeatWatch®. Sixty-nine heifers exhibited estrus (47 P, 22 PP) after CIDR removal. There was no difference (P > 0.05) in the interval to estrus after CIDR removal for P and PP heifers [50.0 ± 27.3 h (P), and 48.1 ± 28.3 h (PP), respectively]. Comparisons of follicular dynamics were made on the basis of the day of the estrous cycle that heifers were on at the time GnRH was administered based on the day estrus was expressed after CIDR removal. There was a significant effect (P < 0.05) of day of the estrous cycle on mean follicle diameter at GnRH. Response to GnRH was highest among heifers with dominant follicles ≥ 10.0 mm (64/71, 90%) and lower among heifers with follicles < 10 mm (4/8, 44%). Mean follicle diameter was ≥ 10.0 mm among heifers that were on d 5, 6, 7 or 8 of the estrous cycle at GnRH. Concentrations of progesterone in serum at PG were higher (P < 0.05) among P versus PP heifers [7.9 (P) and 6.9 ng/ml (PP), respectively]. Estrous response after PG did not differ among P and PP heifers and peaked between 48 and 60 h. This study provides a descriptive comparison of response to presynchronization with a CIDR prior to GnRH and PG in P and PP beef heifers. Future studies are required comparing long- and short-term CIDR-based protocols to establish the merit of presynchronization among mixed populations of P and PP beef heifers. [ABSTRACT FROM AUTHOR]

This article provides an overview of the Missouri Show-Me-Select Replacement Heifer Program, and is included to provide an example of a working model for the collective considerations that relate to beef heifer development presented in this issue. This program expanded services provided by veterinarians to cow-calf producers, making veterinary practitioners a more integral part of the overall reproductive management of beef herds in their practice areas., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Expanded use of artificial insemination (AI) and/or adoption of emerging reproductive technologies for beef heifers and cows require precise methods of estrous-cycle control. New protocols for inducing and synchronizing a fertile estrus in replacement beef heifers and postpartum beef cows in which progestins are used provide new opportunities for beef producers to synchronize estrus and ovulation and to facilitate fixed-time AI. This article reviews the various estrous synchronization protocols currently available for use in replacement beef heifers. New methods of inducing and synchronizing estrus now create the opportunity to significantly expand the use of AI in the United States cowherd., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Postnatal nutrition has immediate and long-lasting effects on beef heifer reproductive efficiency, longevity, and productivity. This article reviews the effects of nutrients and nutritional management on reproduction in developing heifers. In addition, the current debate on the preferred target weight for heifers at breeding is discussed., (Copyright © 2013 Elsevier Inc. All rights reserved.)

At weaning, heifers should be considered for replacements based on their dam's previous performance; heifer calving date, age, and weight; and previous exposure to implants. Before breeding, heifers should be selected as replacements based on whether they have attained puberty (determined by a prebreeding examination), do not have abnormal pelvic areas, or fail to meet temperament standards. After breeding, heifers should be selected as replacements if they conceive early in the breeding season, are capable of achieving 85% of their mature weight by calving, and calve at a body condition of 5.5 to 6.0., (Copyright © 2013 Elsevier Inc. All rights reserved.)