Abstract:
In an effort to increase the number of lambs produced per ewe's productive lifetime in New Zealand, an increasing number of ewe lambs (8–9 months old) are being bred. This, in turn, results in an increased proportion of second-parity 2-year-old ewes in New Zealand's breeding flock, rather than the more usual first-parity 2-year olds. The longer-term effects of dam parity on resulting ewe progeny are of interest and few studies have examined this. The present study was designed to determine whether parity (first or second) of Romney 2-year-old dams had any effect on the metabolic function of their single- and twin-born and reared ewe lamb progeny at 10 months of age. Ten-month-old, single and twin ewe lamb progeny born to first- or second-parity dams (n = 8 per group) were catheterised and given intravenous glucose (0.17 g/kg liveweight) (GTT), insulin (0.15 IU/kg liveweight) (ITT) and epinephrine (1 μg/kg liveweight) (ETT) tolerance tests to assess their glucose and fat metabolism and adrenal function. Rearing rank reduced (P < 0.05) the insulin response of twins to a glucose challenge, but increased (P < 0.05) their glucose response to an insulin challenge. Offspring from first-parity dams had higher (P < 0.05) basal plasma concentrations of cortisol and cortisone, whereas their cortisol/cortisone responses to an insulin challenge were unaffected by either dam parity or rearing rank. Neither dam parity nor rearing rank appeared to influence responses to an epinephrine challenge. The present study suggests that both dam parity and rearing rank alter the glucose and insulin metabolism of the offspring, which may have longer-term impacts on the growth and reproductive efficiency of the animal.