Replacement heifers from March and May calving herds were offered ad libitum meadow hay and 4 lb/d supplement or grazed meadow and offered 1 lb/d supplement from mid- January to mid- April. Heifers fed hay gained more during the treatment; however, heifers grazing meadow experienced compensatory gain, resulting in similar body weight at pregnancy diagnosis in both calving herds. Pregnancy rates were similar between treatment groups in March and May heifers. A reduced input winter management system is a viable option to maintain pregnancy rates in early and late summer breeding seasons

Applegarth, Andy

Funston, Richard N.

Musgrave, Jacqueline A., Musgrave

Nielson, Hazy Rae

Nollette, John

Springman, Shelby A.

English

DigitalCommons@University of Nebraska

University of Nebraska - LincolnDigitalCommons@University of Nebraska - LincolnNebraska Beef Cattle Reports Animal Science Department2017Impact of Heifer Development System in TwoDifferent Breeding SeasonsShelby A. SpringmanUniversity of Nebraska-Lincoln, shelby.springman@huskers.unl.eduHazy Rae NielsonUniversity of Nebraska-Lincoln, hnielson21@gmail.comJacqueline A. Musgrave MusgraveUniversity of Nebraska - Lincoln, jmusgrave1@unl.eduJohn NolletteUniversity of Nebraska-Lincoln, john.nollette@unl.eduAndy ApplegarthUniversity of Nebraska-Lincoln, andy.applegarth@unl.eduSee next page for additional authorsFollow this and additional works at: http://digitalcommons.unl.edu/animalscinbcrPart of the Large or Food Animal and Equine Medicine Commons, Meat Science Commons, andthe Veterinary Preventive Medicine, Epidemiology, and Public Health CommonsThis Article is brought to you for free and open access by the Animal Science Department at DigitalCommons@University of Nebraska - Lincoln. It hasbeen accepted for inclusion in Nebraska Beef Cattle Reports by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln.Springman, Shelby A.; Nielson, Hazy Rae; Musgrave, Jacqueline A. Musgrave; Nollette, John; Applegarth, Andy; and Funston, RichardN., "Impact of Heifer Development System in Two Different Breeding Seasons" (2017). Nebraska Beef Cattle Reports. 1008.http://digitalcommons.unl.edu/animalscinbcr/1008AuthorsShelby A. Springman, Hazy Rae Nielson, Jacqueline A. Musgrave Musgrave, John Nollette, Andy Applegarth,and Richard N. FunstonThis article is available at DigitalCommons@University of Nebraska - Lincoln: http://digitalcommons.unl.edu/animalscinbcr/10088 · 2017 Nebraska Beef Cattle Report©  Th e Board Regents of the University of Nebraska. All rights reserved.ResultsMarch- born Gain and Reproductive PerformanceMarch- born HAY heifers had greater (P = 0.01) ADG during the treatment period than MDW heifers (Table 1). However, following treatment, MDW heifers tended (P = 0.07) to have a greater ADG compared with HAY heifers. Summer ADG (May 22 to Sept. 10) was similar (P = 0.12) between treatments. Signifi cant year eff ects are noted on summer ADG among heifers developed in 2012 compared with other develop-ment years, presumably due to the severe drought. Post- treatment and prebreeding BW was greater (P = 0.02) for HAY heifers. At pregnancy diagnosis, HAY heifers tend-ed (P = 0.06) to have greater BW compared with MDW heifers. Percent of mature BW prior to the breeding season was greater (P = 0.02) for HAY compared with MDW. Pubertal status prior to breeding was not diff erent (P = 0.51) between treatments. Furthermore, pregnancy rates were similar for HAY and MDW heifers (P = 0.97, 88 ± 4%). Calving rate and the proportion of heifers that calved within the fi rst 21 d was also similar (P ≥ 0.54) between treatments.May- born Gain and Reproductive PerformanceData for BW gain and reproductive performance on May- born heifers are presented in Table 2. Similar to March- born heifers, May- born heifers on HAY had greater (P = 0.01) ADG during the treatment period. Spring and summer ADG was greater (P = 0.03) for MDW heifers, due to a compensatory gain eff ect. Post- treatment and pre- breeding BW was greater (P = 0.02) for HAY heifers compared with MDW heifers. At pregnancy diagnosis, BW was similar (P = 0.16) between treat-ments. Percent of mature BW prior to the breeding season was greater (P = 0.02) for the impact of heifer development system on subsequent growth and reproductive performance in early and late summer breeding seasons.ProcedureA 4- yr study was conducted at the Gudmundsen Sandhills Laboratory (GSL), Whitman, NE, that utilized replacement heifers from 2 calving seasons. March- born (n = 225) and May- born (n = 258), crossbred (5/8 Red Angus, 3/8 Continental) heifers were stratifi ed by BW and randomly assigned to 1 of 2 post- weaning nutritional treatments (2 pastures·treatment- 1·year- 1) from mid- January to mid- April. Heifers were off ered ad libitum meadow hay (HAY) and 4 lb/d (29% CP, DM) supplement or allowed to graze meadow (MDW) and off ered 1 lb/d of the same supplement. Prior to and following treatment, heifers were managed together within their respective breeding group. Prior to each breeding season, 2 blood samples were collected 10 d apart to determine pubertal status. Heifers with plasma progesterone concentrations greater than 1 ng/mL at either collection were considered pubertal. Heifers were synchronized with a single PGF2α injection 5 d aft er being placed with bulls for a 45 d breeding season. Pregnancy diagnosis was conducted via transrectal ultrasonography 40 d following bull removal.Statistical AnalysisData were analyzed using the GLIMMIX procedure of SAS (SAS Institute, Inc., Cary, N.C.), evaluating year, treatment, and year × treatment. Th e proportions of pubertal and pregnant heifers were analyzed using an odds ratio. Least squared means and SE of the proportion of pubertal and pregnant heifers by treatment were obtained using the ILINK function.Shelby A. SpringmanHazy R. NielsonJacqueline A. MusgraveJohn NolletteAndy ApplegarthRick N. FunstonSummary with ImplicationsReplacement heifers from March and May calving herds were off ered ad libitum meadow hay and 4 lb/d supplement or grazed meadow and off ered 1 lb/d sup-plement from mid- January to mid- April. Heifers fed hay gained more during the treatment; however, heifers grazing meadow experienced compensatory gain, resulting in similar body weight at pregnancy diagnosis in both calving herds. Pregnancy rates were similar between treatment groups in March and May heifers. A reduced input winter management system is a viable option to maintain pregnancy rates in early and late summer breeding seasons.IntroductionTraditional recommendations suggest heifers reach 55 to 65% of mature body weight (BW) at the time of breeding. Due to the cost of retaining replacement heifers, more eff orts have been made to devise economical methods of developing heifers. Previous studies have indicated heifers developed to lower target BW have comparable reproductive performance to heifers developed in higher input systems. Furthermore, it has been reported heifers fed to 51% vs. 57% mature BW showed no diff erence in puberty attainment. However, heifers developed on corn residue had a reduced percentage that reached puberty compared with winter range or drylot developed heifers. Th erefore, the objec-tive of the current study was to determine  Impact of Heifer Development System in Two Diff erent Breeding Seasons2017 Nebraska Beef Cattle Report · 9 Table 1.  Eff ect of over- winter treatment on developing March- born heifer gain and reproductive performanceDevelopment Year TreatmentItem 2012 2013 2014 2015 SEM P- value Hay1 MDW2 SEM P- valuen 50 50 101  24 113 112ADGTreatment ADG,3 lb/d 1.37 1.43 1.57 1.28 0.11 0.42  1.70 1.12 0.07 0.01Spring ADG,4 lb/d 2.03x 0.66xy 0.33y 0.31y 0.31 0.06  0.46 1.21 0.20 0.07Summer ADG,5 lb/d 0.60b 1.37a 1.23a 1.48a 0.06 <0.01  1.12 1.21 0.03 0.12Body WeightWeaning BW, lb 425b 412b 467a 463ab 9 0.01 443 441 4 0.86Post- treatment BW, lb 644yz 639z 697x 648xz 13 0.07 683 631 8 0.02Pre- breeding BW,6 lb 701ab 664b 712a 677ab 11 0.049 705 672 7 0.02Percent of Mature BW,7 % 57ab  54b  58a 55ab 1 0.049  58 55 1 0.02Pregnancy Diagnosis BW, lb 767b 816ab 847a 851a 12 0.02 831 809 6 0.06Pubertal,8 % 66a  30b  68a 54ab 7 <0.01  53 57 5 0.51Pregnancy Rate, % 92  82  84 96 7 0.21  88 88 4 0.97Calving rate, % 90  80  82 — 6 0.36  86 83 4 0.54Calved in fi rst  21 d, % 80  75  78 — 7 0.83  78 78 5 0.98 1HAY = heifers received ad libitum hay and 4 lb/d supplement from Jan. 15 to April 15.2MDW = heifers grazed meadow and received 1 lb/d supplement from Jan. 15 to April 15.3Treatment ADG from Jan. 16 to April 22 (96 d), includes the treatment period.4Spring ADG from April 22 to May 22 (30 d).5Summer ADG from May 22 to Sept 10 (111 d).6Pre- breeding BW determined May 22.7Percent of mature BW at breeding based on mature cow size of 1,218 lb.8Considered pubertal if blood serum progesterone concentration > 1 ng/mL.a,b,c For Development Year, means in a row with diff erent superscripts are diff erent (P ≤ 0.05).x,y,z For Development Year, means in a row with diff erent superscripts are diff erent (0.05 ≤ P < 0.1).Table 2.  Eff ect of over- winter treatment on developing May- born heifer gain and reproductive performanceDevelopment Year TreatmentItem 2012 2013 2014 2015 SEM P- value HAY1 MDW2 SEM P- valuen 66 65 68 59  128  130ADGTreatment ADG,3 lb/d 1.17xz 0.86yz 1.10xz 1.41x 0.09 0.09 1.39 0.86 0.07 0.01Spring ADG,4 lb/d 1.92b 2.43a 2.56a 1.90b 0.07 0.01 2.07 2.34 0.04 0.03Summer ADG,5 lb/d 0.68c 0.84c 1.76a 1.34b 0.07 <0.01 1.06 1.26 0.04 0.03Body WeightWeaning BW, lb 434x 434x 406xy 397y 11 0.05 417 419 4 0.90Post- Treatment BW, lb 580 522 527 540 13 0.13 575 514 9 0.02Pre- breeding BW,6 lb 697 672 686 666 11 0.32 703 657 7 0.02Percent Mature BW,7 % 57 55 56 55  1 0.32  58 54 1 0.02Pregnancy Diagnosis BW, lb 765b 772ab 866a 787ab 13 0.05 811 785 11 0.16Pubertal,8 % 78a 37b 96a 54b  5 <0.01 72 60 4 0.02Pregnancy Rate, % 71 62 70 76  6 0.38 72 68 4 0.44Calving Rate, % 68 57 67 —  6 0.35 65 63 5 0.77Calved in 1st 21 d, % 75 74 60 —  8 0.27 60 78 6 0.031HAY = heifers received ad libitum hay and 4 lb/d supplement from Jan. 15 to April 15.2MDW = heifers grazed meadow and received 1 lb/d supplement from Jan. 15 to April 15.3Treatment ADG from Jan. 5 to May 10 (125 d), includes the treatment period.4Spring ADG from May 10 to July 9 (30 d).5Summer ADG from July 9 to Sept 10 (63 d).6Pre- breeding BW determined July 9.7Percent of mature BW at breeding based on mature cow size of 1,218 lb.8Considered pubertal if blood serum progesterone concentration > 1 ng/mL.a,b,c For Development Year, means in a row with diff erent superscripts are diff erent (P ≤ 0.05).x,y,z For Development Year, means in a row with diff erent superscripts are diff erent (0.05 ≤ P < 0.1).10 · 2017 Nebraska Beef Cattle Reportthan in May (87 vs. 70 ± 3%). Th e lower pregnancy rate in May heifers may be due to declining forage quality and quantity during the breeding season.Shelby A. Springman, graduate studentHazy R. Nielson, former graduate studentJacqueline A. Musgrave, research technicianJohn Nollette, research technicianAndy Applegarth, operations managerRick N. Funston, professor, University of Nebraska- Lincoln West Central Research and Extension Center, North Platte, Neb.HAY (58%) compared with MDW (54%). May- born heifers on HAY had greater (P = 0.02) pubertal status prior to breeding than MDW. Signifi cant development year eff ects are noted for spring and summer ADG due to the severe drought year in 2012. Pregnancy and calving rates were similar (P ≥ 0.44) between treatments, although, the proportion of heifers that calved in the fi rst 21 d was greater (P = 0.03) for MDW compared with HAY.Heifer development system did not impact pregnancy rate in the March or May replacement heifers; however, March heifer pregnancy rate was greater (P < 0.01) 

Impact of Heifer Development System in Two Different Breeding Seasons

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Impact of Heifer Development System in Two Different Breeding Seasons

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