Abstract

Pregnancy rate of yearling (15-18 months) red deer hinds may be influenced by time that puberty is attained, especially if stags are removed before all hinds have had a chance to conceive. This paper reports on two studies that investigated onset of puberty in red deer hinds. In Study 1, ovarian follicle populations and luteal activity of pubertal and adult red deer hinds were monitored for three months during their transition into the breeding season. Yearling (n = 5) and adult (n = 5) hinds were grazed in one group and weighed monthly. A fertile stag was run with them from 20 March until 11 May. Yearling hinds were significantly lighter than adults in March (85.8 vs 91.3 kg, SED = 2.1). There were no significant differences between yearling and adult hinds in mean day of first (14 April vs 8 April, SED = 3.5) or second (23 April vs 16 April, SED = 3.7) ovulations, or interval between ovulations (9 vs 8 days, SED = 0.7). First ovulation was invariably followed by a transient rise in plasma progesterone concentration and then a second ovulation preceded by oestrus. All hinds conceived to their first mating, demonstrating the ability of red deer hinds to exhibit high conception rates. In Study 2, daily observations for mating activity of yearling (n = 80) and adult (n = 80) hinds were carried out continuously from dawn until dusk for the period 25 March-27 April. Hinds were grazed on pasture in one of five single sire mating groups: Gp1, adults only (n = 40); Gp2, yearlings only (n = 40); Gp3, adults (n = 20) + yearlings (n = 20); Gp4, adults (n = 10) + yearlings (n = 10); Gp5, adults (n = 10) + yearlings (n = 10). Hinds were scanned by rectal ultrasonography to determine pregnancy status and estimate fetal age. Yearling hinds were significantly lighter than adults in March (101 vs 119 kg, SED = 1.3). The stag in Gp3 was replaced due to exhaustion and consequently, mean conception date of yearlings in that group was 16 days later than that of the yearlings in Gps 2,4 & 5, which had a mean conception date 12 days later than that of the adults (1 May vs 15 April vs 3 April, SED = 1.1; P < 0.001). There was no significant difference between age groups in the number of non-pregnant hinds. These data indicate that yearling red deer hinds reach puberty and are mated in mid-April, about two weeks later than adult hinds. Conception failure was not a limiting factor to yearling reproductive performance; therefore, under standard farming conditions, it is unlikely that stags will be removed from the mating mob before yearling hinds have had a chance to conceive. KEYWORDS: red deer hinds; puberty; reproduction.

IC, Scott, GW Asher, KT O'Neill, and RP Littlejohn

Proceedings of the New Zealand Society of Animal Production, Volume 65, Christchurch, 306-311, 2005