The Julian Date Calendar: A Helpful Tool for Livestock Management Decisions


Guide B-130

Jason L. Turner and Craig Painter

College of Agricultural, Consumer and Environmental Sciences, New Mexico State University


Respectively, Extension Horse Specialist, Department of Extension Animal Sciences and Natural Resources; and State 4-H Agent for Agriculture and Natural Resources, New Mexico State University. (Print Friendly PDF)

Introduction

The tables in this guide are designed to aid livestock owners in keeping more complete and useful date records for a herd. These tools can help predict birthing dates, the date to wean young animals, when to remove sires from a pasture of females for a “set” breeding season, and when to take routine measurements (e.g., weight) for collection of routine performance data. Note that it applies only to non-leap years; in leap years (2020, 2024, 2028, etc.), add one day for any date occurring after February 28.

Aerial photograph of a large herd of cattle walking along a fenceline.

(Photo by John Wenzel courtesy of the Hurt Cattle Company.)

Examples of How to Use the Julian Date Calendar (Table 3)

Expected Birth Date. Add 283 to the “day number” that the cow was bred. If date bred was June 5 (Day 156), the cow should calve about 283 days later, or March 15 (Day 439). For a mare, add 340 days to the “day number” for the last date bred. If the mare was last bred on April 16 (Day 106), then the mare should foal about 340 days later, or March 22 (Day 446).

Breeding Season. Assume bulls are turned out on May 1 (Day 121), and the breeding season is to extend for 75 days. Then, 121 + 75 = 196. So the bulls should be removed from the breeding pasture on July 15 (Day 196).

Calving Interval. If the calving interval in the herd averages more than 12 months, or 365 days, the management program should be reviewed. If a cow calves on March 15 (Day 74) and again on March 9 (Day 433) of the next year, her calving interval is 359 days.

Return to Estrus, Ovulation Interval, Pregnancy Determination. If you are using artificial insemination and ultrasound to manage breeding of your mare, you may wish to determine when the mare will next ovulate. If the mare last ovulated a follicle on April 5 (Day 95), then she should ovulate again 21 days later on April 26 (Day 116). If the mare last ovulated on April 26 (Day 116) and you wanted to “check her in foal” at 45 days of pregnancy, then you would ultrasound for pregnancy on June 10 (Day 161).

Weaning date. If a goat doe has kids on March 5 (Day 64) and you want to wean kids at 10 weeks of age, then you would wean 70 days later on May 16 (Day 134). If you want to wean a foal born on March 28 (Day 87) at 6 months, or 180 days of age, then you would wean the foal on September 24 (Day 267).

Drug Withdrawal Time. The withdrawal period is the time between the last dose of the pharmaceutical given and the time when the animal can be safely slaughtered for food. If the “pour-on” dewormer used on your beef animal was dosed on October 10 (Day 283) and has a 48-day withdrawal period, the animal should not be sent to slaughter prior to November 27 (Day 331).

205-Day Weight. Calves must be weighed between 160 and 250 days of age for correct adjustment to the 205-day weaning-age weight. Thus, the earliest date to weigh a calf born on March 15 (Day 74) is 160 days later, on August 22 (Day 234). November 20 (Day 324) is the last day that a March 15 calf can be weighed for a 205-day adjustment weight.

365-Day Weight. Yearling calves must be weighed between 330 and 450 days of age for this adjustment. So an animal born on March 15 (Day 74) must be weighed between February 8 (Day 404) and June 8 (Day 524) of the following year to determine the adjusted weight.

Tables 1 and 2 provide some reference information for livestock management that can aid your calculations using Table 3.

Table 1. Average Length of Estrus, Estrous Cycle, and Gestation (in days) for Common Livestock Species

Species

Estrus (heat)

Estrous cycle

Gestation (pregnancy)

Beef cow

0.25–1.0

21

283

Sheep

1–1.5

17

150

Goat

1–2

21

150

Swine

1.5–2.5

21

114

Horse

5–7

21

340

Source: Momont, H.W. 2016. Overview of the reproductive system. In Merck Veterinary Manual, 11th ed. Retrieved May 23, 2019, from https://www.merckvetmanual.com/reproductive-system/reproductive-system-introduction/overview-of-the-reproductive-system


Table 2. Age at Traditional Weaning (in days) for Common Livestock Species

Species

Age at weaning

Beef cow1

180–240

Sheep2

60–90

Goat3

60–90

Swine4

21–42

Horse5

120–180

1Mathis, C.P., and M. Encinias. 2005. Early weaning beef calves [Guide B-126]. Las Cruces: New Mexico State University Cooperative Extension Service.

2Mathis, C.P., and T. Ross. 2005. Sheep production and management [Circular 604]. Las Cruces: New Mexico State University Cooperative Extension Service.

3Penn State University Extension. n.d. Meat goat production and management home study course: Weaning time. Retrieved November 25, 2019, from https://extension.psu.edu/programs/courses/meat-goat/basic-production/general-overview/weaning-time

4Rea, J.C. n.d. Care of pigs from farrowing to weaning. Retrieved May 23, 2019, from https://extension2.missouri.edu/g2500

5Freeman, D.W. 2013. Weaning and management of weanling horses. Retrieved May 23, 2019, from https://horses.extension.org/wp-content/uploads/2019/07/ANSI-3978web.pdf


Table 3. The Julian Date Calender

Day of

Month

Year #1

Day of

Month

Year #2

Jan

Feb

Mar

April

May

June

July

Aug

Sept

Oct

Nov

Dec

Jan

Feb

Mar

April

May

June

July

Aug

Sept

Oct

Nov

Dec

1

1

32

60

91

121

152

182

213

244

274

305

335

1

366

397

425

456

486

517

547

578

609

639

670

700

2

2

33

61

92

122

153

183

214

245

275

306

336

2

367

398

426

457

487

518

548

579

610

640

671

701

3

3

34

62

93

123

154

184

215

246

276

307

337

3

368

399

4274

58

488

519

549

580

611

641

672

702

4

4

35

63

94

124

155

185

216

247

277

308

338

4

369

400

428

459

489

520

550

581

612

642

673

703

5

5

36

64

95

125

156

186

217

248

278

309

339

5

370

401

429

460

490

521

551

582

613

643

674

704

6

6

37

65

96

126

157

187

218

249

279

310

340

6

371

402

430

461

491

522

552

583

614

644

675

705

7

7

38

66

97

127

158

188

219

250

280

311

341

7

373

403

431

462

492

523

553

584

615

645

676

706

8

8

39

67

98

128

159

189

220

251

281

312

342

8

373

404

432

463

493

524

554

585

616

646

677

707

9

9

40

68

99

129

160

190

221

252

282

313

343

9

374

405

433

464

494

525

555

586

617

647

678

708

10

10

41

69

100

130

161

191

222

253

283

314

344

10

375

406

434

465

495

526

556

587

618

648

679

709

11

11

42

70

101

131

162

192

223

254

284

315

345

11

376

407

435

466

496

557

557

588

619

649

680

710

12

12

43

71

102

132

163

193

224

255

285

316

346

12

377

408

436

467

497

528

558

589

620

650

681

711

13

13

44

72

103

133

164

194

225

256

286

317

347

13

378

409

437

468

498

529

559

590

621

651

682

712

14

14

45

73

104

134

165

195

226

257

287

318

348

14

379

410

438

469

499

530

560

591

622

652

683

713

15

15

46

74

105

135

166

196

227

258

288

319

349

15

380

411

439

470

500

531

561

592

623

653

684

714

16

16

47

75

106

136

167

197

228

259

289

320

350

16

381

412

440

471

501

532

562

593

624

654

685

715

17

17

48

76

107

137

168

198

229

260

290

321

351

17

382

413

441

472

502

533

563

594

625

655

686

716

18

18

49

77

108

138

169

199

230

261

291

322

352

18

383

414

442

473

503

534

564

595

626

656

687

717

19

19

50

78

109

139

170

200

231

262

292

323

353

19

384

415

443

474

504

535

565

596

627

657

688

718

20

20

51

79

110

140

171

201

232

263

293

324

354

20

385

416

444

475

505

536

566

597

628

658

689

719

21

21

52

80

111

141

172

202

233

264

294

325

355

21

386

417

445

476

506

537

567

598

629

659

690

720

22

22

53

81

112

142

173

203

234

265

295

326

356

22

387

418

446

477

507

538

568

599

630

660

691

721

23

23

54

82

113

143

174

204

235

266

296

327

357

23

388

419

447

478

508

539

569

600

631

661

692

722

24

24

55

83

114

144

175

205

236

267

297

328

358

24

389

420

448

479

509

540

570

601

632

662

693

723

25

25

56

84

115

145

176

206

237

268

298

329

359

25

390

421

449

480

510

541

571

602

633

663

694

724

26

26

57

85

116

146

177

207

238

269

299

330

360

26

391

422

450

481

511

541

572

603

634

664

695

725

27

27

58

86

117

147

178

208

239

270

300

331

361

27

392

423

451

482

512

543

573

604

635

665

696

726

28

28

59

87

118

148

179

209

240

271

301

332

362

28

393

424

452

483

513

544

574

605

636

666

697

727

29

29

88

119

149

180

210

241

272

302

333

363

29

394

453

484

514

545

575

606

637

667

698

728

30

30

89

120

150

181

211

242

273

303

334

364

30

395

454

485

515

546

576

607

638

668

699

729

31

31

90

151

212

243

304

365

31

396

455

516

577

608

669

730

Acknowledgment

The authors gratefully acknowledge the authors and revisors of previous publications on this subject: Larry Foster and Ron Parker, former Extension Beef Cattle Specialists; Manny Encinias, Extension Beef Cattle Specialist; and John Wenzel, Extension Veterinarian.

For Further Reading

B-120: Anthrax and Livestock
https://aces.nmsu.edu/pubs/_b/B120/welcome.html

B-224: Cow Herd Vaccination Guidelines
https://aces.nmsu.edu/pubs/_b/B224/welcome.html

M-112: Water Quality for Livestock and Poultry
https://aces.nmsu.edu/pubs/_m/M112/welcome.html


Photo of Jason L. Turner.

Jason L. Turner is a Professor and Extension Horse Specialist at NMSU. He was active in 4-H and FFA while growing up in Northeastern Oklahoma. His M.S. and Ph.D. studies concentrated on equine reproduction, health, and management. His Extension programs focus on proper care and management of the horse for youth and adults.


Photo of Craig Painter.

Craig Painter is an Associate Professor and Extension State 4-H Agent for agriculture and natural resources with NMSU’s Cooperative Extension Service. He earned his master’s degree from New Mexico State University in agriculture and Extension education.


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