Environmental effects on thermoregulation and breathing patterns during early postnatal development in hand‐reared lambs

Abstract

SUMMARYThis study examines the effect of hand-rearing developing lambs in a warm (WR; 25°C) or cool (CR; 10-15°C) ambient temperature on the control of thermoregulation and breathing patterns, when maintained at a fixed level of nutrition over the first month of postnatal life. Measurements were made during non-rapid eye movement sleep whilst lambs were maintained for at least 1 h at warm (28-19°C) and cold (14-5°C) ambient temperatures at 1, 7, 14 and 30 days of age. All lambs were able to maintain normal body temperature, but oxygen consumption was higher in CR lambs at 14 and 30 days of age. At 1 day of age shivering was rarely observed in any lambs, but at 7 and 14 days of age more WR than CR lambs responded to cold exposure via shivering. Plasma concentrations of triiodothyronine were higher at 7 and 14 days of age in CR lambs. Breathing frequencies were similar in WR and CR lambs, and from 7 days of age the incidence of expiratory laryngeal braking was higher in warm compared with cold study temperatures. By 30 days of age the recruitment of this mechanism was greater in CR lambs. Mean growth rate was slower over the first week of postnatal life in CR compared with WR lambs. This difference decreased over the first month of life, as growth rate increased from 83 to 130 g day-' in the CR group but remained constant at approximately 150 g day-' in the WR lambs. Total weight of the lungs and heart, but not the liver, were lower at 1 month but not at 1 week of postnatal life in CR lambs. It is concluded that a modest decrease in the ambient temperature in which postnatal lambs are reared, when on a fixed feed intake, alters lung size, the recruitment of laryngeal braking and the control of body temperature.

Adipose Tissue Development During Early Postnatal Life in Ewe-Reared Lambs

“…The major finding of the present study is that perirenal adipose tissue undergoes two clear developmental phases over the first month of postnatal life which could be mediated by modest changes in lamb body temperature around the established normothermic set point of 40-0°C (Recabarren, Vergara, Llanos & Seron-Ferre, 1987;Symonds et al 1995a). Phase one occurs over the first 4-7 days of life and is associated with the maintenance of high quantities of mRNA for UCP in conjunction with a peak in the amount and thermogenic activity of UCP at 4 days.…”

Maintenance of arterial pressure in infant rats during moderate and extreme thermal challenge

“…Laryngeal constriction during expiration may be an indication of laryngeal braking, a maneuver that is thought to enhance oxygen transport in the lungs (Blumberg & Alberts, 1990). Interestingly, respiratory records of adult dogs exhibiting the ACR (see Figure 18, Youmans et al, 1974, and Figure 3, Gilfoil, Youmans, & Turner, 1959) bear a striking resemblance to records that are commonly described as indicative of laryngeal braking, that is, such records contain a shoulder on the expiratory curve (e.g., Andrews et al, 1991;Davis & Bureau, 1987;Symonds et al, 1995). Interestingly, respiratory records of adult dogs exhibiting the ACR (see Figure 18, Youmans et al, 1974, and Figure 3, Gilfoil, Youmans, & Turner, 1959) bear a striking resemblance to records that are commonly described as indicative of laryngeal braking, that is, such records contain a shoulder on the expiratory curve (e.g., Andrews et al, 1991;Davis & Bureau, 1987;Symonds et al, 1995).…”

Nutrition, temperature and homeostasis during perinatal development

“…Significant differences between euthyroid or hypothyroid warm-and cold-reared lambs assessed by analysis of variance: * P < 0.05, ** P < 0.01. Data for euthyroid lambs adapted from Symonds, Andrews, Buss,Clarke, Darby, Johnson & Lomax (1995).…”