THE INFLUENCE OF MATING FREQUENCY AND NUTRITION ON THE STIMULUS VALUEOF BOARS

Two experiments were conducted to investigate the possible influences of mating frequency and nutrition levels on the stimulus value of indi vidual boars. In Experiment 1, eight young boars were assigned to one of four mating frequencies: 0, 1, 3 or 6 matings week(-1) from 9 to 14 months of age. Between 12 and 14 months of age all boars were used as stimulus males to induce early puberty attainment in groups of prepub ertal gilts. This involved 60 days of daily exposure of a group of eig ht prepubertal gilts to each boar for a period of 20 min from a mean g ilt age of 163 days. There was no significant effect of the number of copulations per week that the boar was allowed on his ability to induc e early puberty attainment in gilts. There was also no effect of matin g frequency on the sexual behaviour of boars, as measured in standardi sed sexual motivation tests. However, the data collected in this area were limited and therefore the results are inconclusive. In Experiment 2, eight boars were fed either a 'high' (n = 4) or 'low' (n = 4) plan e of nutrition from 5 to 9 months of age, these nutritional planes rep resenting feed levels of ad libitum and 1.5 times maintenance, respect ively. From 9 months of age until the conclusion of the study, two of the 'high' plane boars and two of the 'low' plane boars were fed ad li bitum (Treatments HH and LH, respectively) while the remaining two 'hi gh' plane and two 'low' plane boars were fed at a level of 1.5 times m aintenance (Treatments HL and LL, respectively). Each of the boars was exposed to a group of eight prepubertal gilts from 9 months of age in order to assess stimulus value (as described for Experiment 1). There was no significant effect of boar nutritional planes on the stimulus value of the boars as measured by gilt puberty attainment in response to daily boar contact. These results suggest that factors other than m ating frequency and nutrition are responsible for the determination of a boar's stimulus value.