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Plasma samples taken every 30 min over a 26-h period each month from six 4- to 15-month-old red deer stags were analysed for GH. In addition, two samples taken at 10.00 and 22.00 h were analysed for insulin-like growth factor-I (IGF-I) and insulin-like growth factor-II (IGF-II). A concentrate diet was available ad libitum. Food intake, body weight and antler status were recorded. Concentrations of GH were analysed using the PULSAR peak detection routine. Secretion of GH was pulsatile in every month of sampling, but the pattern of pulsatility differed seasonally. During the autumn and early winter (April-June in the Southern hemisphere) GH pulses were frequent and of low amplitude. In contrast, GH pulses in spring (August-September) were of high amplitude and high frequency resulting in a high mean level of GH circulating in the plasma. In early summer (November) the GH pulse amplitude was much lower and pulse frequency fell. There was a rise in GH pulse frequency not accompanied by an increase in GH pulse amplitude in summer (December-January). GH pulse amplitude seemed to be the main determinant of mean GH plasma level. Secretion of IGF-I was raised 1 month after peak monthly mean GH secretion. There was little consistent relationship between concentrations of IGF-II and mean daily GH. Concentrations of GH correlated positively and significantly with liveweight gain and antler growth rate with a delay of 1 month. Significantly positive correlations between concentrations of IGF-I, liveweight gain and antler growth rate were observed. It is considered that the spring and summer (September-December) seasonal acceleration of liveweight gain and antler development in stags could be a consequence of high winter/early spring (August-September) GH pulse frequency and amplitude resulting in increased concentrations of IGF-I, particularly in October.

Blood samples were taken from six tame red deer stags at 3-15 months of age once a month from a jugular catheter every 30 min for 24 h to investigate hormonal secretion during puberty and during growth of the pedicle and first antler. All plasma samples were analysed for LH and testosterone concentrations and the resultant data were analysed using the PULSAR pulse detection routine. In addition each stag was injected wih gonadotrophin-releasing hormone (GnRH; 20 ng/kg body weight) after the above samples had been taken and the bleeding regimen was continued for a further 2 h. Body weight, antler size and status (i.e. whether the stags had a pedicle or antler) were also recorded. The pulsatile secretion of LH could be considered to have occurred in three phases. The first of these was one of development, with the LH pulse frequency increasing to 8 pulses/24 h, the second a phase of regression, with a decrease in LH pulse frequency to 2 pulses/24 h, and finally a second phase of development characterized by increased LH pulse frequency to 12 pulses/24 h. Testosterone secretion generally followed the same pattern. During the period before the permanent bony pedicles grew, there were less than five LH pulses/24 h. When the pedicles were growing, LH and testosterone pulsatile secretion increased but the pulse frequency of both hormones fell during velvet antler growth.(ABSTRACT TRUNCATED AT 250 WORDS)

Lamb survival and birth weight data were collected from 3 Booroola-Merino crossbred flocks from 1975 to 1982. The mean litter sizes for these flocks were 1.79, 1.99, and 1.80, with birth rank ranging from 1 to 4 within each flock. Birth weight was the most important factor affecting survival; other apparent effects, such as that of year, ewe age, and birth rank could be largely explained by birth weight differences. Using a quadratic function relating chances of survival to birth weight for single-born lambs, optimum birth weights for the 3 flocks were estimated as 5.45, 4.73, and 4.27 kg. A hyperbolic relationship between survival and birth weight was used for multiple-born lambs, which rarely had higher birth weights and associated dystocia problems. At any given birth weight within a range common to all litter sizes, lambs born in large litters (~ 3) had a lower probability of survival than contemporary lambs born as singles or twins. Age-at-death data indicated that, in all birth ranks, a large proportion of deaths occurred within the first 12 h post-partum.

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