Reid Borgwardt

Behavioural responses of domestic pigs and cattle to humans and novel stimuli

Two experiments were conducted on pigs and beef cattle to study whether or not regular exposure to either humans or novel objects resulted in stimulus-specific or generalised behavioural responses. Groups of pigs and cattle were allocated to one of three treatments: regular brief exposure to either (1) an experimenter handling the animals in a positive manner (Human treatment) or (2) three novel objects (Novel Object treatment) and (3) minimal contact with humans and novel objects (Minimal treatment). After 4 weeks of treatment, the behavioural responses of the animals to humans and novel objects were studied. Pigs in the Human treatment were quicker (P < 0.01) to physically interact with the experimenter in the Human Approach Tests than pigs in the other two treatments. Pigs in the Human treatment were also quicker (P < 0.05) to closely approach the experimenter than pigs in the Novel Object treatment. Cattle in the Human treatment spent more time (P < 0.05) close to the experimenter in the Human Approach Tests than cattle in the other two treatments. Furthermore, cattle in the Human treatment were also quicker (P < 0.01) to closely approach the experimenter than cattle in the Minimal treatment. Pigs in the Human treatment were quicker (P < 0.01) to approach within 0.5 m of the novel stimulus in the Novel Object Approach Tests than pigs in the Minimal treatment and there was a tendency for pigs in the Novel Object treatment to approach the novel stimulus more rapidly (P < 0.07) than pigs in the Minimal treatment. The approach behaviour of cattle to the novel object in the Novel Object Approach Tests was similar for the three treatments. The results of these experiments provide evidence that changes in the behavioural response of animals undergoing regular positive handling by humans is stimulus specific to humans. Furthermore, there was some evidence that the behavioural response of pigs, but not cattle, to the novel stimulus was affected by previous exposure to that stimulus and other novel stimuli.

Effect of early experience on the sexual performance of yearling rams

The following study examines the effect of early sexual experience on the sexual performance of yearling rams. Forty-eight rams were given four individual 30 min exposures to estrous ewes at 10 months of age (experimental Ss). Forty-seven male counterparts were given no early heterosexual experience (control Ss). All subjects were maintained in a single all-male group from weaning (3 months of age). At 22 months of age, experienced and control rams were individually exposed to four estrous ewes for 30 min on four occasions at weekly intervals. Sexual behaviors observed included courship, mounting and ejaculation frequencies. Significantly fewer experienced rams than control rams (P < 0.01) failed to show sexual interest in ewes on Test Day 1 (1 of 48 vs. 13 of 47 rams, respectively). In addition, sexually active experienced rams exhibited higher (P < 0.01) rates of ejaculation than sexually active control rams on all four test days (x = 4.17 vs. 3.45 per 30 min, respectively). Follow-up studies on non-performing rams revealed that continuous exposure to ewes usually activated sexual interest in females. It was concluded that lack of exposure to ewes during early development can inhibit the expression of sexual behavior in rams. This effect has not been reported in the sexual development of male cattle and swine.

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.

Heterosexual experience differentially affects the expression of sexual behavior in 6- and 8-month-old ram lambs

Abstract The sexual performance of 6- and 8-month-old ram lambs (175 and 26 subjects, respectively) was quantified when individually exposed to four estrous ewes for 30 min on four occasions 7 days apart. In addition, half of the animals in each age class (experimental subjects) were exposed to 16 estrous females for 6, 16 or 24 h after testing on Test Days 1, 2 and 3. Control subjects received no additional exposure to females. Sexual performance improved for all groups over the 4 weeks of testing. However, 6-month control rams improved at a slower rate than 6-month experimental rams. By the fourth weekly test, 58% of the control rams and 85% of the experimental rams had attained ejaculatory competence. Treatment did not affect the sexual performance of the 8-month-old subjects; both control and experimental groups had attained 100% ejaculatory competence by the fourth week. Length of the extended exposure to females did not affect the results. It was concluded that the sexual responsiveness of ram lambs toward females is sufficiently undeveloped at 6 months (i.e. puberty) that extended exposure to sexually receptive ewes is needed for many males to exhibit adult levels of sexual performance. At 8 months, the sexual development of ram lambs has sufficiently matured so that relatively brief encounters with estrous females releases the full expression of adult sexual behaviors. These findings may be of benefit to sheep breeders who wish to use ram lambs in their breeding programs.

Effect of early fenceline exposure to estrous ewes on the sexual performance of yearling rams

Abstract Previous research has demonstrated that early heterosexual (mating) experience improves the sexual performance of yearling rams. The present study examines the effect of early fenceline (FL) contact of young ram lambs with estrous females on their sexual performance as yearlings. A total of 104 rams, 7–8 months of age, were given either no contact (NC), direct contact (DC) or FL exposure to estrous ewes during a 3-week period in the fall breeding season. When initially tested for sexual performance as yearling rams at 18–19 months, 8 of 21 (38%) FL rams exhibited no sexual interest in estrous females (did not court or mount females), a result that was intermediate to and not significantly different from (P>0.05) the incidence of sexual disinterest exhibited by NC (59%) and DC rams (15%). The difference between NC and DC rams was significant (P 0.05) the incidence of mounting by NC and DC males (41% vs. 85%, respectively). Again, NC and DC rams differed from one another (P

Sexual responses of rams to ovariectomized and intact estrous ewes.

This investigation compares the sexual performance of rams when exposed to ovariectomized and intact estrous ewes. In Experiment 1, 22 sexually experienced rams were sequentially exposed to hormone-induced ovariectomized estrous ewes or intact estrous ewes that were cycling naturally or induced to exhibit estrus using progestin sponges. The sexual performance of the rams was not affected by ewe treatment. In Experiment 2, 95 rams were simultaneously exposed to ovariectomized and intact ewes induced to exhibit estrus via hormone treatment. Rams mounted ovariectomized ewes more frequently than intact females, but ejaculation rates were similar for the two treatments. It was concluded that the ejaculation frequency of rams in sexual performance tests (i.e. serving capacity) is not biased by the mode of estrus induction of the stimulus females.

Effect of ewe restraint on the libido and serving capacity of rams

Abstract The following study examines the effect of ewe restraint when assessing the libido and serving capacity of rams. Twenty-five domestic rams were exposed to both unrestrained and restrained estrous ewes under circumstances in which copulations were permitted and prevented. Ewe restraint did not affect the rate of ejaculation or measures of precopulatory behavior when copulation was permitted. When rams were exposed to ewes whose perinea had been covered to prevent copulations (libido tests), bouts of leg-kicking and anogenital sniffing were not affected by female restraint but mounting occurred more frequently when ewes were unrestrained. The latter measures of libido correlated with ejaculation rates (serving capacity) observed in tests permitting copulation and, in four out of six cases, were slightly higher when covered females were restrained. Rams were particularly aggressive (butts and vigorous pawing) toward ewes that were covered and restrained. It was concluded that the advantages of ewe restraint are not great enough to justify its use when assessing the libido and mating potential of rams with estrous ewes.

Sexual stimulation in male sheep and goats

Abstract Previous research has shown that the sexual performance of male goats is enhanced by viewing the mating activities of other males prior to being placed with sexually receptive females. This same experience has no effect on the sexual performance of male sheep. In the present experiment, 14 male goats and 17 rams were individually allowed to sniff and nuzzle the anogenital region of an estrous female and engage in premating behaviors, but not mount for 20 min immediately prior to the administration of 30-min sexual performance tests. A female-absent control treatment was administered to these same animals prior to sexual performance tests. In the sexual stimulation treatments, male goats were more sexually active than rams ( P P >0.20 for all variables). Male goats and sheep did not differ ( P >0.05) in number of completed matings (services) but male goats exhibited more mounts without ejaculation ( P P

Incidence of repeat-breeding among Angus bulls (Bos taurus) differing in sexual performance

Rams exhibiting relatively high levels of sexual performance (HP) repeat-breed the same female fewer times than low-performing (LP) rams. The objective of this study was to determine if HP and LP bulls differed in their tendency to repeat-breed individual females. Eighteen sexually experienced Angus bulls (20–60 months of age) were tested individually with 10 unrestrained, estrous females. The sexual behaviors of all cattle were recorded until the bull achieved six services (ejaculations). Bulls were tested on 2 days with at least 10 days between tests. Frequencies of recorded sexual behaviors were higher for LP than HP bulls (P<0.05), possibly because of the greater time spent in attaining six services. LP and HP bulls did not differ in the number of females serviced. LP bulls serviced the same number of individual females in both tests (4.0±0.3). However, HP bulls serviced a greater number of individual females (repeat-bred less) during Test 2 than Test 1 (4.7±0.3 and 3.0±0.3; P<0.05). There was no correlation between time to attain six services and the number of different females serviced (r=0.04), but the number of different females serviced positively correlated with age of the bull (r=0.53, P<0.05). Repeat-breeding of at least one female was observed in 33 of 36 tests (92%). Repeat-breeding at least one female twice in succession was observed in 24 of 36 tests (67%). There were 12 of 36 tests (33%) in which a female was serviced twice but not in succession. Females were serviced three times in succession in seven tests (19.4%). Sexual performance level did not influence mate preferences or the incidence of repeat-breeding during tests.

Sexual performance of twin ram lambs and the effect of number and sex of contemporary siblings

The objectives of this investigation were to determine the degree of correspondence in the sexual performance of twin male sheep and to compare the sexual performance of ram lambs born co-twin to another male (M-M), co-twin to a female (M-F) and as single (S) offspring. Individual ram lambs (N=117), including 13 M-M twin sets, were exposed to four estrous ewes for 30 min at 7-day intervals over a 4-week period at 8 to 9 months of age.Frequencies of ejaculation (serving capacity) and mounts without ejaculation were recorded. M-M males averaged 2.9 ejaculations and 13.1 mounts per test. Individuals within 9 of the 13 M-M twin sets (69%) differed by an average of 0.5 or fewer ejaculations per test. Although variability within M-M twin sets was very low, variability between the 13 M-M twin sets was also low (coefficient of variation=10.6%). Consequently, frequencies of both ejaculation and mounting (without ejaculation) within the 13 twin sets were not correlated (P=0.50 and P=0.10, respectively). When the progeny of individual sires were compared, mounting frequencies were correlated (P<0.02) but not ejaculation rates (P=0.72). M-M, M-F and S ram lambs did not differ for either ejaculation frequency (P=0.26) or mounts without ejaculation (P=0.98). It was concluded that the sexual performance of related individuals is likely to be very similar and that the number and sex of contemporary siblings does not necessarily influence rates of mounting and ejaculation.