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.

(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.

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://pubs.nmsu.edu/_b/B120/

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

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

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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.

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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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