Chin-marking behavior in male and female New Zealand rabbits: onset, development, and activation by steroids

Effects of intrauterine position during gestation on specific endocrine and behavioral parameters that impact reproduction in domestic rabbits

Prior studies from others, performed in a different breed, reported that doe rabbits developing between two male siblings (2 M) during gestation display characteristics indicative of masculinization: larger anogenital distance (AGD), larger submandibular glands, and higher chinning frequency than females with zero (0 M) or one (1 M) contiguous brothers. Similar effects are provoked by injecting androgens to the pregnant doe suggesting that prenatal androgen exposure masculinizes female embryos. To further understand the scope of such masculinization we compared 0 M, 1 M, and 2 M females regarding behavioral, neuroendocrine, and somatic parameters, related or not to reproduction. IUP did not impact: body weight, sexual receptivity, mating-induced LH secretion, maternal nest-building, litter size, or milk output. At puberty: a) chinning frequency was: 0 M and males>1 M and 2 M; b) ambulation in open field was lowest in 1 M females and males. IUP effects on AGD were significant only on postnatal day 1: 0 M, 1 M, and males>2 M, in contrast to earlier study. Willingness to nurse at delivery was less frequent in 2 M than in 1 M and 0 M does and correlated with nursing occurrence across lactation. Does that did not nurse at parturition delivered fewer kits/min than those that nursed then, regardless of IUP. The duration of nursing bouts across lactation was significantly longer in the1 M and 2 M does that showed this behavior on postpartum days 1-20. Our findings indicate that IUP is associated with alterations in specific aspects of postpartum maternal behavior.

Effects of Taenia Pisiformis Infection and Obesity on Clinical Parameters, Organometry and Fat Distribution in Male Rabbits

Taenia pisiformis infection causes important economic loss in farms. It is suggested that obesity has a major impact on infection and reproduction. We addressed the impact of T. pisiformis infection in normal and obese rabbits to evaluate its effect on parameters important in behavior and reproduction. T. pisiformis infection in obese rabbits decreased body weight. In the obese-infected rabbits, eosinophils and heterophiles were increased 23% by the infection (P ≤ 0.05). T. pisiformis decreased cholesterol by 13% in normal weight infected rabbits and 10% in obese group (P ≤ 0.05), while triglyceride and VLDL were increased by 23% and 45% in the non-infected obese group (P ≤ 0.05). The infection increased serum cortisol levels only in normal weight rabbits (P ≤ 0.05). Liver weight was 20% higher in obese and obese-infected rabbits (P ≤ 0.05). Testicular weight in obese-infected was 46% higher than normal weight (P ≤ 0.0001) and 20% more than the obese-non-infected (P ≤ 0.0001). Furthermore, the infection reduced the weight of submandibular glands in infected and obese-infected rabbits (P ≤ 0.05), body fat increased 10% in the obese-infected than in the obese, and infected group was 35% over the normal weight non-infected (P ≤ 0.01). Our results show that T. pisiformis alters metabolic characteristics in rabbits, which can impact on the production and welfare of animals.

Communication by olfactory signals in rabbits: its role in reproduction

Rabbits use a variety of olfactory signals to transmit information related with reproduction. Such cues are produced in skin glands (submandibular, anal, Harder's, lachrymal, preputial) and the mammary gland-nipple complex. Some signals are transmitted by active behaviors, for example, chin-marking, urination, and defecation, while others are transmitted passively (e.g., mammary pheromone (MP) and inguinal gland secretions). We show that sex steroids regulate: chinning frequency and the chin gland's size, weight and secretory activity in bucks and does by acting on specific brain regions or on the chin gland, respectively. The "mammary pheromone," identified in milk as 2-methyl-but-2-enal, is essential for guiding the pups to the nipples, but its origin (mammary gland, ventral skin, nipple) remains to be determined. Estradiol, progesterone, and prolactin regulate the emission of an olfactory cue that also triggers nipple-search behavior in the pups, but its chemical identity and relation with the MP are unclear.

Ability of mice to detect estrous odor in bovine urine: roles of hormones and behavior in odor discrimination

This study was designed to evaluate the ability of mice to discriminate cow urinary odor from different reproductive phases, with a view toward detecting the estrous phase. Experiments were also carried out to establish the relationship between androgen and mouse behaviors during estrous detection. Further, the study was also intended to establish the relationship between androgen and behaviors in estrous detection. Bovine urine was collected during estrus and non-estrous periods, i.e., prepubertal, preovulatory, ovulatory, postovulatory, pregnancy, and lactation. Behavioral analyses were carried out in a Y-maze apparatus, in which the mice were acclimatized in before odor-preference tests. The number and duration of visits, and grooming behavior by male responders towards the urine samples, were recorded. Intact male mice showed a higher response towards estrus urine samples than towards non-estrous urine. By contrast, orchidectomized mice failed to discriminate estrous urine, whereas castrated mice treated with testosterone regained the ability to discriminate estrus odor. A higher level of grooming behavior was found in males exposed to estrous urine than to urine of other phases. These results suggest that normal mice have the ability to detect estrus, and that this discriminating ability is androgen dependent. The grooming behavior shown by males in response to estrous urine may be taken as a key parameters in estrous detection. The results further suggest that bovine estrous urine produces specific odors that probably involve both intraspecific and interspecific communication.

Physiological response of rabbits to heat, cold, noise and mixing in the context of transport

The effects on rabbits of four potential transport-related stressors (heat [HS], cold [CS], noise [NS] and mixing with unfamiliar animals [MS]) on certain physiological and meat quality parameters were studied. These are factors which may act to reduce the welfare of rabbits during their transport to the slaughterhouse. The rabbits were exposed to each potential stressor for four and a half hours prior to slaughter. HS groups showed the highest plasma concentrations of cortisol, lactate and glucose and greater packed cell volume (PCV) and osmolarity than the control group, and the meat exhibited a low initial pH as a direct consequence of lactic acid accumulation. The rabbits exposed to cold (CS) and noise (NS) showed physiological responses to the potential stressor, although to a lesser degree than rabbits exposed to heat. Cold stressed rabbits showed increased levels of creatine kinase (CK) and a higher PCV as well as decreased muscle glycogen concentration compared to the control. Rabbits exposed to noise showed muscular damage as demonstrated by increased levels of CK and lactate dehydrogenase (LDH) activity in the blood and a high final pH in meat. Mixing unfamiliar rabbits (MS) lead to higher CK activity, lower lactate and glucose concentration and the meat pH was slightly higher than the control group. In conclusion, these results suggested that rabbits exposed to heat were the most affected out of all three groups, although cold, noise and mixing with unfamiliar rabbits also had a detrimental effect on physiological and meat quality parameters.

Sex steroid regulation of chin-marking behavior in male New Zealand rabbits

Chin-marking behavior (chinning) was evaluated daily in nine intact adult male rabbits. All subjects (Ss) displayed chinning (mean of means +/- SE = 61 +/- 7 marks/10 min) but the frequency of this behavior varied largely across them (range of mean chinning frequency = 19-84 marks/10 min). Chinning frequency showed abrupt variations at intervals of 2-3 days, but periodogram analysis did not reveal the existence of an endogenous rhythm in this behavior. Castration significantly decreased (mean of means +/- SE = 29 +/- 9 marks/10 min; p < 0.01). but did not suppress chinning. Testosterone propionate (TP; 1 mg/day for 16 days) restored chinning in castrated Ss to slightly below precastration levels (mean +/- S.E. V 53 +/- 13 marks/10 min). The daily administration of 1 microgram estradiol benzoate (EB) plus 1 mg dihydrotestosterone propionate (DHTP) stimulated chinning within 2 days (mean increase = 147%; p < 0.005). DHTP (1 mg/day) given alone stimulated chinning only after 11 days of treatment (mean increase = 475%; p < 0.01). At higher doses, both DHTP (10 mg/day) and EB (10 or 50 micrograms/day) stimulated chinning by 450%, 80%, and 100%, respectively, over baseline values. Results indicate that chinning largely depends on testicular steroids. Androgen receptor occupation by T or DHT, which is enhanced by E, optimally activates chinning.