[Father-male offspring transmission of seasonal variations in testicular diameter and percentage of abnormal sperm in the Ile-de-France ram. 1. Male offspring born in February].

An experiment was conducted on the Ile-de-France (IF) breed to determine if the more or less important sensitivity of the ram to photoperiodism came under genetic control. Five base breed unrelated rams (greater than or equal to 4 yr old), were chosen for this study: 2 good (I and II), 2 bad (III and IV), and an intermediate sire (V). Ram I, which died a few years before the experiment began, was selected on both the low amplitude of its sperm production during a 6-month period of artificial lighting and the very high fertilizing capacity of its sperm in spring. Rams II to V were controlled for 12 (percentage of morphologically abnormal spermatozoa, AM) or 14 (maximum antero-posterior scrotal diameter of both testes, DT) consecutive months. Following this period of control, seasonal variation in rams was assessed as follows: low (ram II), high (rams III and IV) and intermediate (ram V) seasonal variation rams. Breeding (artificial insemination) of these 5 rams to IF ewes resulted in 18 male offspring born in February and distributed as follows: rams I to III: 4 male offspring/ram (families 1 to 3, F1 to F3), rams IV and V: 3 male offspring/ram (families 4 and 5, F4 and F5). The 18 animals were controlled once a week (DT and AM) from 8, 5 to 46 months of age (7 periods, P1 to P7). Regarding DT, mean DT was higher in F1 and F2 than those of the whole population (WP) (represented by a discontinuous line of ordinate 5.0 in Graph 3), but F2 was closer to this population than F1. On the other hand, they were lower in the rams of F3 and F4. Differences between F3 or F4 and WP were lower in autumn than in spring. All families showed significant differences during the experimental periods except at P7 for pairs 3-5 and 4-5. Distances between F1, F2, F3 were always different (P less than 0.01 or P less than 0.001), whatever the size of the population (n = 3 or 4). Weekly F5 values varied in an opposite way to those of F3 and F4: increase in spring and decrease in autumn. Regarding AM, families did not differ as much as in DT (graph 4). Weekly variations in AM were also stronger. However, mean AM was almost always lower in F1 males and somewhat higher in F3 males to that of WP.(ABSTRACT TRUNCATED AT 400 WORDS)