Body temperature and endocrine interactions before and after calving in beef cows

Area of Science:

• Reproductive Physiology
• Animal Science
• Endocrinology

Background:

• Peripartum physiological changes in multiparous beef cows are complex.
• Interactions between body temperature (BT) and various hormones are not fully understood.
• Environmental factors and calf characteristics may influence pre-calving physiology.

Purpose of the Study:

• To evaluate peripartum changes in beef cows.
• To investigate the interactions among body temperature and circulating hormones (progesterone, estradiol-17beta, triiodothyronine, cortisol, thyroxine, PGFM).
• To determine factors affecting pre-calving body temperature.

Main Methods:

• Radiotelemetry was used to measure body temperature (BT) in 7 multiparous beef cows every 3 minutes from 144 hours before to 24 hours after calving.
• Environmental temperatures (ET) were recorded hourly.
• Blood samples were collected every 8 hours to measure concentrations of progesterone (P4), estradiol-17beta (E2), triiodothyronine (T3), cortisol, thyroxine (T4), and 13,14-dihydro-15-keto-prostaglandin F2alpha (PGFM).

Main Results:

• Body temperature varied by time of day, with the lowest at 0300 and highest at 1900.
• BT decreased significantly from 48 to 8 hours before calving, independent of ET.
• Pre-calving BT decrease was influenced by calf sex (lower in cows carrying heifers) and associated with increased E2, PGFM, T3, and T4 concentrations; PGFM and T3 explained approximately 30% of the variation during the temperature decrease.

Conclusions:

• Pre-calving body temperature in beef cows is affected by environmental temperature and calf sex.
• The observed prepartum decrease in body temperature appears independent of these factors.
• The prepartum body temperature decrease seems to be partially induced by endocrine changes.