Effect of pre-mating nutritional status in red deer ( Cervus elaphus scoticus) hinds on the sex ratio of their offspring

Abstract

The aim of this experiment was to study the effect of nutritional status during the pre-mating period on the offspring sex ratio and certain metabolic indicators in red deer hinds. Seventy-six, non-lactating, non-pregnant hinds were assigned to one of six groups at the onset of the rutting season and maintained in separate pens until mating. Groups were randomly allocated to one of three experimental diets, which were offered for 28 days and designed to provide 115% (115-MR; n = 24), 100% (100-MR; n = 26) and 85% (85-MR; n = 26) of maintenance requirements. Body weights were recorded on days 0 and 28 and body weight changes (BWC) during this period were recorded. On days 0, 14 and 28, blood samples were obtained from 4 females/diet in order to determine the plasma triiodothyronine (T 3), reverse triiodothyronine (rT 3) and glucose (GL) concentrations. Mating was initiated on day 28 using 1 stag/group, and gender of the offspring was recorded at parturition. The interval from the onset of mating to conception (MCI) was determined relative to the parturition date. The percentage males born, MCI and plasma glucose and thyroid hormones did not differ between the 115-MR, 100-MR and 85-MR hind groups. BWC within groups were not constant, as each group had animals, which lost, maintained or gained body weight. Accordingly hinds were re-classified as those representing a positive (BWC+; n = 38) or negative/neutral BWC (BWC−; n = 38). The percentage of male offspring was 65.8% versus 44.7% for BWC+ and BWC− hinds, respectively. MCI was similar for male and female offspring but shorter in the BWC+ versus BWC− groups (7.98 days versus 15.03 days; P < 0.01) with no interaction. No differences in T 3, rT 3 or T 3/rT 3 ratio between BWC+ and BWC− hinds were recorded, although differences were recorded between the days of sampling ( P < 0.01). GL was influenced ( P < 0.01) by hind BWC pattern, day of sampling and the interaction (181.4, 127.8 and 138.7; 103.8, 112.7 and 108.9 mg/dl, for days 0, 14 and 28 for the BWC+ and BWC− groups, respectively). The pre-mating nutritional status of red deer hinds may influence the male/female ratio of the offspring. No evidence was recorded indicating that this effect may be mediated by a difference in offspring survival rate with regard to the sex of the fawns or associated with metabolic indicators in the hinds.