Reindeer bull introduction affects the onset of the breeding season

Biostimulation and pheromones in livestock: A review

This review examines aspects of the phenomenon of biostimulation in swine, goats, sheep, cattle and deer, to improve the collective knowledge and exploitation of its relevant mechanisms and effects in animal production. The long-term goal is to implement biostimulation strategies that benefit livestock reproduction and production while being both cost-effective and socially acceptable.

Potential applications of assisted reproductive technologies (ART) in reindeer (Rangifer tarandus)

Interest in the use of assisted reproductive technology in reindeer husbandry has gradually increased during the last decades. This article reviews Western and Russian literature on reindeer semen collection, semen cryopreservation and artificial insemination. In addition, literature on the synchronisation of the stage of reindeer oestrous cycle among females, recovery of in vivo embryos, embryo transfer, the production of in vitro-produced embryos and pregnancy diagnosis is reviewed.

Reproduction of male reindeer (Rangifer tarandus)

The present review provides a comprehensive assessment on the basic aspects of the reproduction of the Rangifer male with a special focus on pubertal development, and the seasonal dynamics of gametogenesis, androgenesis, antler cycle and other physiological and behavioural characteristics of the rutting male. A greater understanding of the reproductive physiology of the males is needed to improve existing management strategies of semi-domestic stocks in the changing climate and to develop species-specific assisted reproductive technologies for improving the in situ and ex situ conservation programs to preserve endangered subspecies as well as to facilitate the transfer of genetic resources between fragmented wild or semi-domestic populations.

The Antler Cycle and Fecal Testosterone of Male Sambar Deer Rusa unicolor unicolor at the Horton Plains National Park in Sri Lanka

This study is aimed at evaluating the relationship between endogenous testosterone levels and antler development in male sambar deer (Rusa unicolor unicolor) inhabiting the Horton Plains National Park, Sri Lanka. Seven antler growth stages of sambar were documented based on phenotypic observations for the first time in Sri Lanka as (a) cast, (b) growing 1—single spike, (c) growing 2—antler fork into a Y as the second tine appears, (d) growing 3—velvet begins to harden as the third tine appears, (e) growth completed—velvet shedding begins, (f) hard antler, and (g) casting. Fecal samples were collected every month for a period of eighteen months from male sambar deer in different stages of the antler growth cycle, feeding in the wet patana grasslands of the park, and the fecal testosterone level was estimated by radioimmunoassay. Ten animals were randomly selected from each antler stage for the experiment. The results disclose that the highest concentrations of testosterone were recorded in the hard antler stage. Velvet shedding was preceded by an increase in the testosterone level, and it is the sudden drop in the testosterone concentration which triggers the antler casting. The casting stage corresponded with the lowest mean testosterone concentration. Although the study was able to conclude a clear relationship between the fecal testosterone levels of the male sambar deer in the Horton Plains National Park and their antler stages, there is no clear seasonality for the antler cycle.

The "ram effect": new insights into neural modulation of the gonadotropic axis by male odors and socio-sexual interactions

Reproduction in mammals is controlled by the hypothalamo-pituitary-gonadal (HPG) axis under the influence of external and internal factors such as photoperiod, stress, nutrition, and social interactions. Sheep are seasonal breeders and stop mating when day length is increasing (anestrus). However, interactions with a sexually active ram during this period can override the steroid negative feedback responsible for the anoestrus state, stimulate luteinizing hormone (LH) secretion and eventually reinstate cyclicity. This is known as the “ram effect” and research into the mechanisms underlying it is shedding new light on HPG axis regulation. The first step in the ram effect is increased LH pulsatile secretion in anestrus ewes exposed to a sexually active male or only to its fleece, the latter finding indicating a “pheromone-like” effect. Estradiol secretion increases in all ewes and this eventually induces a LH surge and ovulation, just as during the breeding season. An exception is a minority of ewes that exhibit a precocious LH surge (within 4 h) with no prior increase in estradiol. The main olfactory system and the cortical nucleus of the amygdala are critical brain structures in mediating the ram effect since it is blocked by their inactivation. Sexual experience is also important since activation (increased c-fos expression) in these and other regions is greatly reduced in sexually naïve ewes. In adult ewes kisspeptin neurons in both arcuate and preoptic regions and some preoptic GnRH neurons are activated 2 h after exposure to a ram. Exposure to rams also activates noradrenergic neurons in the locus coeruleus and A1 nucleus and increased noradrenalin release occurs in the posterior preoptic area. Pharmacological modulation of this system modifies LH secretion in response to the male or his odor. Together these results show that the ram effect can be a fruitful model to promote both a better understanding of the neural and hormonal regulation of the HPG axis in general and also the specific mechanisms by which male cues can overcome negative steroid feedback and trigger LH release and ovulatory cycles.

Female effect on antlers of pampas deer (Ozotoceros bezoarticus)

Size and bone mineralization of deer antlers are related to testosterone concentrations, and antler cast is observed after withdrawal of testosterone concentration. Our objectives were to determine if (i) contact with hinds stimulates antler development and increases hard antler period length in pampas deer ( Ozotoceros bezoarticus (L., 1758)) and (ii) antlers from males that were or were not in contact with hinds differ in colour. While 5 males were in breeding paddocks consisting of 1 adult stag and 5–10 hinds, the other 6 males were allocated as a single-male group. We collected, weighed, and measured the volume, circumferences, and lengths of antlers, and determined their colour. First antler cast tended to be later in males in contact with females than those in the single-male group. Antler mass and volume were greater in antlers from males in contact with females. Circumference at the base of first and second tines was also greater in antlers collected from males in contact with females. Surfaces of antlers from these males were darker than those of antlers from males that remained isolated from females in all points. Hind contact stimulated male pampas deer, increasing antler mass, size, and darkness, as well as possibly hard antler period length.

The reproductive performance of female Formosan sambar deer (Cervus unicolor swinhoei) in semi-domesticated herds

This study documented the reproductive performance of 210 adult female Formosan sambar deer (FSD, Cervus unicolor swinhoei) from four semi-domesticated deer herds in Taiwan. An extensive analysis of 525 reproductive records from 2000 to 2008, including the conditions of estrus, gestation, and parturition was conducted. The mean+/-S.E.M. lengths of the estrous cycle, gestation, and fawning interval were 18.2+/-0.5d (n=56), 258.6+/-0.3d (n=160), and 369.9+/-2.3d (n=122), respectively. Hand breeding was performed between June and December (n=494), with the majority (93.1%) occurring between July and October (P<0.05). Fawning occurred from February to September (n=318), and most frequently (83.0%) between April and June (P<0.05). Pregnancy rate per mating in FSD hinds was 64.4%. There was a 1.3:1 male-to-female ratio at birth (P<0.05) among 320 fawns, and only two cases of twinning (0.63%). The postnatal mortality rate was 6.6% (21/320), and the mortality rate in fawns before weaning did not exceed 8% on any farm. Fecundity was enhanced by high pregnancy rates and high offspring survival rates. This study provides baseline information on reproductive performance of FSD, which should be valuable to veterinarians and deer industry personnel for management of FSD on farms in subtropical countries.

Sexual behavior in ewes and other domestic ruminants

Similarities as well as differences across species in the control of sexual behavior are helping to fully understand the subtle relations between physiology and eco-ethological constraints and how the brain integrates such information. We will illustrate this with sexual behavior in domestic ruminants and especially ewes. Females of these species like humans, but unlike rodents, have a long luteal phase. A prolonged exposure to progesterone (Pg) before the preovulatory estradiol rise is necessary for estrous behavior to be displayed. Estradiol action and receptor localization is very similar to that observed in other species. But not too surprisingly, the role of Pg is rather different with a priming effect not observed in rodents. However, as in rodents, Pg also has an inhibitory effect, is necessary for the display of proceptivity and is responsible for the timing of the different periovulatory events. These steroids act on the central nervous system in similar areas across mammalian species to regulate estrous behavior. Steroid fluctuations during the estrous cycle cause changes in catecholaminergic activity in the hypothalamus. Interestingly, these neurotransmitters seem to have very similar effects in ewes and rats as illustrated by the norepinephrine rise after male-female interactions observed in both species. Similar comparisons can be made regarding the action of some neuropeptides, including oxytocin and GnRH, and more integrative processes like sexual differentiation and modulation of reproduction by social interactions. Data on sheep, goats and cows will be compared with those of rodents.

Steroid hormone secretion during the ovulatory cycle and pregnancy in farmed Alaskan reindeer1

Seasonal endocrine changes in 5 non-bred and 10 pregnant Alaskan reindeer have been documented. Blood samples were collected from early September until early May, spanning the breeding season, gestation, or the anovulatory period. Plasma was analyzed by RIA for progesterone (P4), estradiol-17beta, estrone, and estrone sulfate. Elevated P4 in 80% of the reindeer at the onset of the study indicated that ovarian activity had been initiated. The median date for the onset of the first recorded full-length ovulatory cycle was September 23. In nonbred reindeer, the mean ovulatory cycle length from September to May was 24 +/- 1 d (range 18 to 29 d). Nonbred females continued to cycle throughout the winter, displaying 6 to 8 ovulatory cycles after the beginning of blood sampling. Cycle length (mean 22 to 24 d) did not vary between individuals (P = 0.170) or over the course of the winter (P = 0.244). In early April, ovulatory cycles ceased with normal demise of the corpus luteum in 2 females, whereas the remaining 3 females formed apparently persistent corpora lutea. Natural service breeding occurred between September 10 and October 2, and P4 profiles indicated that all breeding females conceived to the first mating. Concentrations of P4 rose steadily after conception and remained elevated throughout gestation, with mean concentrations not varying significantly (P = 0.104) from 4 to 28 wk of gestation. Estrogens all followed patterns similar to each other, remaining at baseline concentrations until approximately 24 wk of gestation and rising coincidently as P4 declined just before parturition. There was a continual overlap throughout the winter in peak P4 concentrations observed in cycling and pregnant reindeer. Calving occurred between April 8 and May 2, resulting in a mean gestation length of 211 +/- 2.2 d (range 198 to 221 d). Information from this study can be used by Alaskan reindeer producers to improve management and profitability of reindeer production.

Progesterone determination in Iberian red deer by time-resolved fluorometry: an alternative method to RIA

The validation for Iberian red deer of a commercially available Time-resolved fluoroimmunoassay (TR-FIA) designed for analysis of progesterone in human beings was carried out. Intra-assay coefficients of variation ranged from 3.6% to 7.4%, while inter-assay coefficients of variation varied from 5.2% to 15.5%. Accuracy, evaluated by comparing results yielded by TR-FIA with those obtained from a validated radioimmunoassay (RIA) in the measurement of 14 samples, provided a high regression coefficient (R(2)= 0.93). Different progesterone concentrations added to pool plasma showed percentages of recovery that ranged between 102.6% and 82.48%. The limit of detection was 0.102 nmol/L. The results obtained indicate that the present method is suitable for the measurement of progesterone in female Iberian red deer.

Overview of the response of anoestrous ewes to the ram effect

The present review summarises knowledge of the reproductive response of anoestrous ewes to the introduction of rams – in other words, the ram effect. The ovarian and endocrine response, the factors that determine whether ewes will respond or not (associated with both the stimulus and the receptivity of the ewes) and some aspects of practical management are discussed. Information on the use of the ram effect to stimulate post-partum, prepubertal and cyclic ewes is also given. New insights are provided on ovarian response patterns, including recently collected information on luteal responses. The existence of delayed ovulation (5–7 days after the introduction of the rams) followed by luteal phases of normal or short length, luteal cysts and luteinised follicles is reported after scanning the ovaries with ultrasound. Endocrine parameters for depth of anoestrus, such as LH pulsatility and FSH concentrations, and how the concentrations of these hormones should be considered are discussed. Particular attention is paid to the observation of spontaneous, higher LH pulsatility and higher FSH concentrations in anoestrous ewes that respond to rams with luteal phases than in those that fail to respond. The use of progestogen priming and single progestogen administration and the possible advantages for synchronisation of oestrus are also discussed. Other factors that should be considered before the ram effect is applied, such as the strength of the stimulus and some practical considerations, are also included.

The male effect, mounting behavior, and the onset of estrus in farmed muskoxen1

Muskox farming is an emerging industry in Alaska. For such an endeavor to succeed, it is necessary to develop fundamental husbandry tools specifically for this species. This study examined the role of the bull in the onset of seasonal ovarian activity and the synchrony of estrus and tested the efficacy of a radiotelemetric estrus detection system. Twenty parous female muskoxen, ranging in age from 4 to 15 yr, were divided into three groups (balanced by age and body weight). Groups received early bull exposure (EBE; August 1, n = 7), late bull exposure (LBE; August 22, n = 6), or remained physically isolated from a bull (NBE; n = 7). Just before bull introduction, radiotelemetry transmitters were attached to the rump of muskox cows in the EBE and LBE groups. Plasma samples were collected from all the cows twice weekly and analyzed for progesterone (P4). The mean date of onset of seasonal ovarian activity was earlier in the EBE and LBE groups than in the NBE group (P < 0.001) and was earlier in EBE (P < 0.021) than in LBE. All EBE and LBE cows conceived to the first fertile cycle, giving 100% fertility. The time interval for the onset of ovarian activity between the first and last cow within each group was 7 d in the EBE group, 12 d in the LBE group, and 24 d in the NBE group. Radiotelemetry correctly identified estrus 95% of the time (18 of 19 instances). Mean length of estrus for each cow, calculated from the time of first mount until last mount, was 771 +/- 98 min (range = 4 to 1,508 min). Mean number of mounts during estrus was 8.89 +/- 1.29 (range = 3 to 25 mounts). Length of estrus at the first short cycle did not differ from the length of the first fertile estrus between, or within, individuals. Estrous behavior was initiated more frequently during the night (2300 to 0500; P < 0.05). Bull introduction can be used as a simple, low-cost management tool for synchronizing estrus in farmed muskoxen. Radiotelemetry was an effective tool for identifying breeding behavior in this species.