We investigated if sexual behaviour of rams can be assessed with an electronic Alpha-Detector (AD) which automatically records mounts of mating rams. To evaluate the rams’ libido (i.e. all sexual activities), we used six intact and six vasectomised rams in pen tests in three different seasons (late spring, autumn and early spring). The pen tests consisted of 30-min visual observations of each ram placed in a group of six Merino ewes (three ewes in oestrus and three ewes not in oestrus). In the pen tests, sexual behaviour was recorded and divided into two categories: pre-copulatory and copulatory. For validation purposes, during the pen tests the 12 rams were equipped with the AD and the number of times the 18 oestrous ewes were mounted were counted over a period of 3 days. Of the 1191 mounts visually identified in the six 30-min sessions, 1026 were recorded automatically by the AD (i.e. 94%). The paddock test is an automated method consisting of the same rams wearing an AD and placed in a flock of ~250 Merino ewes on two occasions (late spring (spring 1) and early spring of the following year (spring 2)), their copulatory activities were automatically recorded over a 5-day period. The results of the pen tests in the three seasons revealed no difference between the two types of rams (breeding v. detecting rams). Based on live observations high correlations (r=+0.81, P<0.003 for breeding and r=+0.76, P<0.02 for detecting rams) were found between pre-copulatory and copulatory behaviours. The libido of the two types of rams measured in pen tests showed high repeatability across the three seasons (83 and 75%, P<0.05 for copulatory and pre-copulatory behaviours, respectively). When measured automatically in paddock tests over two consecutive springs, even higher repeatability was observed in both breeding (94%; P<0.01) and detecting rams (97%; P<0.004) in the number of mounts. In addition, high correlations (+0.89<r<+0.94) between copulatory behaviours, as measured by live observations, and those measured by the AD were obtained. The automatic measurement of ram libido in paddock tests appears to be more reliable than pen tests and far less time consuming. We therefore recommend this automated method to estimate the libido of rams. In addition, this method can be used at any season of the year provided that ewes in oestrus are present in the flock.

Seasonal reproduction is one of the major biotechnical and economic constraints of sheep production in temperate latitudes. Treatments using extra light followed by melatonin implants have been used satisfactorily in open barns, farms and artificial insemination centres to produce out-of-season sexual activity in rams. The aim of the present study is to explore the possibility of replacing melatonin implants with continuous light (LL), which was recently shown to increase LH secretion similar to melatonin and/or pinealectomy. Four experiments during 4 consecutive years were conducted in ‘Ile-de-France’ rams. In each study, one group was systematically exposed to permanent light after a first photoperiodic treatment of 60 long days (LD-LL) during the winter and compared with various other control groups subjected either to a natural photoperiod or the classical LD-melatonin treatment. As expected, blood nocturnal melatonin secretion was suppressed by LL. In all four experiments, LL treatment produced a highly significant and robust increase in ram testicular volume in the spring compared with the testicular volume of control rams or of that of treated rams at the end of the LD. For the two experiments in which fertility was tested, fertility after hand-mating was significantly higher in LD-LL rams than in control rams (76% v. 64%). Therefore, permanent light after an LD treatment may be an interesting alternative to LD-melatonin treatment to induce out-of-season sexual activity in rams.

In vitro preservation of the male gamete is a challenge in the development of artificial insemination techniques for domestic animals. Specific strategies and diluents have been developed for the preservation of the fertilizing ability of the semen for each species. However, the epididymal medium has been demonstrated to be the best sperm environment to maintain sperm viability over several days and weeks for mammals. The aims of this study were to evaluate the motility and in vivo fertility of ram epididymal spermatozoa when the semen was stored for up to 4 days at 4°C undiluted in epididymal plasma. The study was undertaken with two ovine breeds (Ile de France and Corriedale). The motility of epididymal spermatozoa was better preserved in the undiluted epididymal fluid than when epididymal spermatozoa were diluted in classic ovine extender such as skim milk. During storage, the decrease in the percentage of motile sperm was lower if the epididymal spermatozoa were collected immediately after epididymal sampling than 24 h after castration or animal death. The fertility obtained after cryopreservation of the stored sperm and subsequent intrauterine insemination ranged from 55% to 24% following 24 to 96-h sperm storage. There was a linear regression relationship between fertility and the number of motile sperm inseminated for both breeds. These results show that it is possible to keep epididymal sperm motile and fertile for several days without dilution. Such a method of sperm preservation could be a final possibility for animals of high genetic value or for endangered species when the collection of semen before death of the animal is not possible.

The effect of two feeding systems (indoors and at pasture) on intake and digestion of fresh grass was studied at two stages of regrowth (21 and 35 days of regrowth) in two parallel experiments. In Experiment 1, 10 adult Martinik rams weighing, on average, 50.5 (±0.9) kg, including four fitted with rumen cannula, were randomly allocated to two groups according to a 2 × 2 Latin Square design. These rams consumed a 21-day regrowth of Digitaria decumbens grass diet during two successive 28-day periods, indoors (five rams) or at pasture (five tethered rams). In Experiment 2, 10 other Martinik rams weighing, on average, 45.5 (±0.9) kg, including four fitted with rumen cannula, were randomly allocated to two groups according to a 2 × 2 Latin Square design. These rams consumed a 35-day regrowth of D. decumbens grass diet during two successive 28-day periods, either indoors (five rams) or at pasture (five tethered rams). For the indoors groups, in vivo organic matter digestibility (OMD) was measured by total collection of feces. In addition, OMD was estimated indoors and at pasture using the fecal CP (CPf) method (OMDCPf). Organic matter intake (OMI) was then estimated using OMDCPf and fecal organic matter output (OMICPf). Correlations of 0.49 and 0.77 were found between in vivo OMD and OMDCPf (P < 0.05) and between OMI and OMICPf (P < 0.001), respectively. OMDCPf was 1.8% (P < 0.05) and 2.7% (P < 0.01) lower indoors than at pasture at 21 and 35 days of regrowth, respectively, whereas OMICPf indoors was 1.1 and 1.16 times that registered at pasture at 21 and 35 days of regrowth, respectively. The higher OMDCPf at pasture was linked to the higher selective behavior of rams at pasture, whereas the differences in OMICPf between the two feeding systems were linked to differences in the total bulk density of the grass. These studies show that differences in OMDCPf and OMICPf exist between animals fed indoors and at pasture with the same forage and that these differences may vary according to the stage of regrowth of the grass offered.

The fatty acid composition of sperm affects the fertilization rate. The objective was to investigate the effects of dietary fish oil (as a source of n-3 fatty acids) on semen quality and sperm fatty acid composition in sheep. Eight Zandi fat-tailed rams were randomly allocated into two groups and fed either a control diet or a diet supplemented with fish oil. Both diets were isocaloric and isonitrogenous and were fed for 13 weeks, starting in the middle of the breeding season. Semen samples were collected weekly and their characteristics evaluated by standard methods, whereas samples collected at the start and end of the study were assessed (gas chromatography) for sperm lipid composition. Mean (±s.e.m.) sperm concentrations (4.3 × 109 ± 1.3 × 108v. 3.9 × 109 ± 1.3 × 108 sperm/ml and percentages of motile (77.25 ± 3.34 v. 60.8 ± 3.34) and progressively motile sperm (74.13 ± 1.69 v. 62.69 ± 1.69) were significantly higher in the fish oil group than control. Dietary fish oil increased the proportion of docosahexaenoic acid (DHA, C22:6 n-3) in sperm fatty acid composition. We concluded that feeding fish oil as a source of n-3 fatty acids attenuated seasonal declines in semen quality in rams, perhaps through increased DHA in sperm.

This study was conducted to investigate the possibility of using bovine oocytes for a heterologous fertility test by intracytoplasmic sperm injection (ICSI) and to compare the pronuclear formation of ram, bull and minke whale spermatozoa after injection into bovine oocytes. Bovine oocytes were cultured in vitro for 24 h and those with a polar body were selected for ICSI. Frozen-thawed semen from the three species were treated with 5 mM dithiothreitol for 1 h and spermatozoa were killed by storing them in a -20 °C refrigerator before use. ICSI was performed using a Piezo system. Three experiments were designed. In experiment 1, a higher (p < 0.05) male pronuclear formation rate was found in the oocytes injected with ram (52.6%) or bull (53.4%) spermatozoa than with minke whale spermatozoa (39.1%). In experiment 2, sperm head decondensation was detected at 2 h after ICSI in the oocytes injected with a spermatozoon of each species. Male pronuclei were first observed at 4 h in the oocytes injected with ram or bull spermatozoa and at 6 h in oocytes injected with minke whale spermatozoa. The mean diameters of male pronuclei derived from both whale and bull spermatozoa were larger than those from ram spermatozoa (30.4 μm and 28.3 μm vs 22.4 μm, p < 0.005). The mean diameter of female pronuclei in the oocytes injected with whale spermatozoa was also larger than with ram spermatozoa (29.3 μm vs 24.7 μm, p < 0.05). The development of male and female pronuclei was synchronous. In experiment 3, ethanol-activated oocytes injected with a spermatozoon from any of the three species achieved significantly higher (p < 0.05-0.001) cleavage rates than control oocytes. Blastocyst formation was only observed when bull spermatozoa were used. The results of this study indicate that dead foreign spermatozoa can participate in fertilisation activities in bovine oocytes after ICSI.

The objective of this study was to determine any differences in the competitive ability of rams differing in levels of sexual performance. Twenty sexually experienced Targhee-type rams were preselected from a population of 95 males for exhibiting relatively high and low ejaculation rates when individually exposed to oestrous ewes for 30 min. Each of 10 high performers (HP) were paired with each of 10 low performers (LP) on three occasions when competing for food (after food deprivation) and twice when competing for an oestrous female. Tests were 5 min in duration. Food-deprived HP and LP rams were equally aggressive when competing for a source offood that could only be accessed by one ram at a time. Time offeeding by HP and LP rams did not differ. HP rams spent more time with the oestrous ewe and attained more mounts in a greater number of pairings than LP rams even though HP and LP rams did not differ in number of successful agonistic interactions (active displacements and successful defences) when competing for the ewe. It was concluded that HP and LP rams, taken as groups, do not differ in their basic competitive ability and that the greater mating success of HP rams can be explained by their higher levels of libido.