Aggressive behavior is reduced in bulls actively immunized against gonadotropin-releasing hormone.

The purpose of this research was to compare the frequency of aggressive behavior's in beef bulls actively immunized against gonadotropin-releasing hormone relative to contemporary nonimmunized control bulls and surgically castrated steers. Eight males were assigned to each ofthese treatments in each of 4 yr. Immunized males were treated with a GnRH-keyhole-limpet hemocyanin (KLH) conjugate at approximately 4 mo of age. A secondary (booster) immunization was administered at 12 mo. Steers were castrated at 4 mo of age. Animals in each treatment in each year were housed as a single group prior to testing. At approximately 16 mo of age, each group of eight animals was placed in a 10- x 16-m enclosure for 20 min on five occasions at 2 to 3 d intervals. An observer recorded butts initiated by each animal as well as participation in bouts of sparring. Relative to control bulls, immunocastration reduced the frequency of butts initiated (P < 0.05) and participation in sparring bouts (P < 0.05) to levels typically observed in steers (P > 0.05). These observations indicate that active immunization against GnRH reduces the incidence of aggressive behavior in male beef cattle and are consistent with our postulate that immunoneutralization of GnRH is an effective alternative to surgical castration in the management of beef cattle.

Artificial selection of rams for sexual performance and its effect on the sexual behavior and fecundity of male and female progeny.

The objective of this study was to determine the effect of a single generation of artificial selection for sexual performance in rams on the sexual behavior and fecundity of their male and female progeny. Ninety-two ram lambs born to sires selected for either high or low sexual performance were evaluated for their sexual behaviors at approximately 8 months of age when individually exposed to four estrous ewes for 30min in four weekly serving capacity tests. Number of mounts and successful matings (ejaculations) were recorded. Fourteen of the 17 high-performing ram lambs identified were sired by high-performing sires, whereas 22 of 37 low-performing ram lambs were sired by low-performing sires (P<0.01). Sons of high-performing sires exhibited more ejaculations (P<0.04) and more mounts without ejaculation (P<0.02) than sons of low-performing sires. The two groups of ram lambs did not differ in mating efficiency (ratio of ejaculations to total mounts). Daughters of high-performing rams (N=79) exhibited their first behavioral estrus approximately 8 days earlier than daughters (N=61) of low-performing sires (P<0.005). Ovulation rates for the two groups of ewe lambs did not differ (P=0.55). It was concluded that there was sufficient genetic variation in the population of sheep studied to obtain a significant response to selection for ram sexual performance in both male and female offspring in a single generation.

Early sexual experience fails to enhance sexual performance in male goats.

We studied the effects of early sexual experience on the adult sexual performance of male dairy goats. Seven postpubertal males were exposed to an estrous female on four occasions during their 1st yr of life. These males were housed with six additional males (controls) that received no early sexual experience. As yearlings, the 13 males were individually exposed to two estrous does for 30 min on three occasions at weekly intervals. Mounts with and without ejaculation were recorded. Sexually experienced and inexperienced males did not differ for either of these variables or a measure of mating efficiency (mounts per ejaculation). Mating efficiency improved for the experimental males during their four initial exposures to estrous females (P < .05). We conclude that male goats, in contrast to male sheep, are not likely to exhibit substandard sexual performance if denied heterosexual experience in their 1st yr.

Repeated matings with individual ewes by rams differing in sexual performance.

Twenty-four sexually mature rams were individually exposed to 10 estrous ewes on three occasions to determine the relationship between levels of sexual performance (ejaculation rate or serving capacity) and the incidence of repeated matings (ejaculations) with individual ewes. Rams that attained six ejaculations in a relatively short period of time (HP rams) mated fewer times with individual ewes than low-performing (LP) rams (P < .01). As a consequence, HP rams tended to mate with a greater number of different ewes than did LP rams (P < .06). In addition, time required to attain six ejaculations was inversely correlated with the number of different ewes mated (P < .03). The HP rams did not differ from LP rams in the number of different ewes investigated and courted. These findings highlight the value of using rams with relatively rapid ejaculation rates when breeding large groups of naturally cycling or synchronized ewes.

Fostering in swine as affected by age of offspring.

Forty-eight pigs were fostered at 2 to 9 h or at 2, 4, or 7 d of age to determine age-related differences in the behavioral interactions between fostered pigs, resident pigs, and the sow during the first 6 h after fostering. Pigs were fostered in pairs to sows with litters of comparable age. In each test, the two fostered pigs and two resident pigs of similar body weight were observed for 6 h, and rate of ambulation, successful and unsuccessful suckling attempts, vocalizations, and approaches to within a body length of the sow's snout were recorded. Sniffs and aggression directed at the fostered and resident pigs by the sow were also recorded. Eleven of 12 pigs fostered at 2 to 9 h of age met the criterion for successful suckling within 6 h of fostering. Suckling success at the three older ages (2, 4, and 7 d) was much lower (25 to 50%; P < .005) after 6 h had passed. The behavior of pigs fostered at 2 to 9 h was similar to that of the resident pigs at all ages, whereas the pigs fostered at 2, 4, or 7 d showed a greater reluctance to engage in suckling, higher rates of ambulation, and more frequent vocalizations. Sows tended to be more aggressive toward older fostered pigs. It was concluded that fostering pigs older than 1 to 2 d of age will slow the rate at which they integrate into the new sow-litter environment and engage in suckling behaviors.

Measures of libido and their relation to serving capacity in the ram.

The purpose of this study was to determine whether the ejaculation rate (serving capacity) of sexually experienced rams could be estimated by selected measures of sexual libido when rams were exposed to estrous ewes under conditions that prevented copulations. Twenty-four crossbred rams selected for either high or low rates of copulation were exposed to two restrained estrous ewes under three treatment conditions that 1) permitted the full range of precopulatory and copulatory behaviors, 2) permitted precopulatory behaviors and mounting but precluded copulation, or 3) permitted precopulatory behaviors but not mounting or copulation. Frequencies of precopulatory behaviors (bouts of leg-kicking and anogenital sniffing) in each of the three treatment conditions and mounting frequency in Treatment 2 occurred in proportion to the ram's characteristic ejaculation rate (P < .001), suggesting that the mating potential of rams can be estimated under conditions that preclude copulation. Frequencies of precopulatory behaviors and mounting were lower when the rams were allowed to copulate, due largely to periods of sexual inactivity after ejaculations.

Relationship between the sexual performance of bulls and their behavioral responses to non-sexual novel stimuli.

Individual differences in the sexual reaction times and ejaculation rates (serving capacity) of 14 beef bulls were compared with their behavioral responses to a novel arena and to novel non-sexual visual and auditory stimuli. Correlation coefficients for ejaculation rates were consistently low and nonsignificant, but bulls that were most inhibited by the novel environment/stimuli exhibited the longest latencies for first mount and ejaculation. The emotional reactivity of bulls may be more closely related to their sexual inhibitions than to measures of reproductive success.

The theory of high-altitide corrections to the U.S. Navy standard decompression tables. The cross corrections.

The theoretical basis for the Cross high-altitude corrections to the USN Standard Decompression Tables is derived. Providing corrections are made for depth and ascent rate and if no decompression stops are made, a dive at altitude can be transformed to a dive at sea level for which the theoretical tissue responses are mathematically similar to the altitude dive. The transformation fails if decompression stops are required due to the fact that the stop criteria used in the USN Tables do not obey the same rule of transformation. It is shown that the failure of the high-altitude correction is expected to be conservative.