Effects of composition and density of the group on the performance, behaviour and age at puberty in swine

The effect of age and growth traits on puberty and reproductive performance in the gilt

“…However, within the two youngest age groups, namely 130 and 150 days, and overall, the finding of significant negative correlations (Table 3) between the interval from stimulation to puberty and lifetime growth rate, live weight and backfat thickness at stimulation indicates that the rate of sexual maturation in the gilt can be accelerated by a higher rate of growth and by increased body fat reserves. Other factors contributing to this variability include the influence of social environment during rearing (Clark, Bell, Tribble and Lennon, 1985) and season (Mavrogenis and Robison, 1976). On the assumption that threshold levels of age, live weight and fatness are necessary for the attainment of puberty, it is reasonable to postulate that these levels might differ between genetic strains of gilts, genotype having been shown to be a major factor influencing the attainment of puberty (Christenson, 1981;Hutchens, Hintz and Johnson, 1981).…”

Pre- and Postpubertal LH and Estradiol Pattern in Gilts Subjected to Intermittent Inescapable Electroshock

“…The causal relationships in this variation are poorly understood. It has been suggested that the vari-ation as well as the problems with delayed puberty seen in intensively housed gilts (Christenson 1981, Rampacek et al 1981, Clark et al 1985, Prunier & Meunier-Salaiin 1989 may be attributed to nonspecific physiological reactions to long term stress. Several management routines and intensive housing methods can alter the activity in the hypothalamus-pituitary-adrenal (HPA) axis and are usually suggested to increase the basal level of plasma cortisol (Barnett & Hutson 1987).…”