Prenatal maternal influences on the control of thermoregulation and breathing during non-rapid eye movement sleep in developing lambs
Symonds ME., Lomax MA., Andrews DC., Johnson P.
This study examines the extent to which altering maternal metabolism via chronic cold exposure (i.e., winter shearing) and changes in feed intake over the final month of gestation influences development changes in breathing control during non-rapid eye-movement sleep (Non-REM) of neonatal lambs. In lambs born from well-fed (100% of total energy requirement) unshorn ewes metabolic rate and breathing frequency was lower between 4-30 days of age than those born from under-fed ewes (60% of total requirements for unshorn ewes). Laryngeal braking of expiratory airflow was observed in ca 40% of breaths during non-REM sleep at 14 and 30 days of age in lambs born from well-fed ewes compared with ca 10% of breaths in the under-fed group. The combined effects of under-feeding plus chronic cold exposure (of shorn ewes) resulted in newborn lambs which possess brown adipose tissue with an increased thermogenic activity, and exhibited a higher metabolic rate and breathing frequency over the first day of neonatal life. Laryngeal braking of expiratory airflow was commonly observed in lambs born from shorn ewes between 4-30 days of age, despite maternal under-feeding ewes. It is concluded that changes in maternal metabolism can influence developmental changes in breathing control which may be linked to effects on the control of thermoregulation.