Tibiotarsus bone characteristics and tibial dyschondroplasia incidence of broilers fed diets supplemented with leucine and valine.

Two experiments were conducted to study the effect of standardized ileal digestible (SID) leucine and valine levels on tibiotarsus bone characteristics and the incidence of tibial dyschondroplasia of broilers from day 1 to 21 (Experiment I) and day 21 to 42 post-hatch (Experiment II). Each experimental phase was evaluated independently. In both experiments, a total of 1,500 one-day-old Cobb 500 male broiler chickens were distributed in a completely randomized design 5 × 5 factorial arrangement for a total of 25 treatments. The SID leucine and valine levels were ranged from 10.0 to 19.6 g/kg, and 6.0 to 12.0 g/kg from day 1 to 21 post-hatch, respectively, while day 21 to 42 post-hatch ranged from 10.0 to 18.0 g leucine/kg, and 5.2 to 11.2 g valine/kg. Serum calcium and phosphorus, bone concentrations of calcium, phosphorus and ash, diameter and Seedor index of the tibiotarsus were not affected (p > .05) by the treatments at 21 or 42 days of age. There was an interaction (p ≤.06) between the SID levels of leucine and valine on tibiotarsus breaking strength at 21 days, but not at 42 days of age (p > .05). Tibiotarsus breaking strength was maximized in broilers from day 1 to 21 with the dietary levels of leucine and valine at 14.2 and 9.0 g/kg respectively. Dietary leucine levels reduced linearly (p < .05) the hypertrophic zone of tibiotarsus cartilage at 21 days of age. Therefore, leucine and valine supplementation interact positively on bone strength of broilers from day 1 to 21 post-hatch. Leucine can be a useful amino acid for reducing the hypertrophic cartilage zone in broilers from day 1 to 21, but not from day 21 to 42 post-hatch.

TRIENNIAL LACTATION SYMPOSIUM/BOLFA: Adipokines affect mammary growth and function in farm animals.

The essential role of mammary fat pads in mammary growth and morphogenesis was the first indication that biologically active molecules, secreted from adipocytes or other stromal cells, could regulate endocrine cues for growth and function of the mammary gland. The presence of leptin and adiponectin receptors in mammary tissues suggested that locally produced or circulating adipokines could affect mammary growth and function. Herein, we present the current knowledge on the role of adipokines in mammary cell proliferation and differentiation and in lactogenesis and galactopoiesis in farm animals. We also address the role of milk adipokines in the neonate. Accumulating evidence suggests that adipokines could act as metabolic sensors, regulating mammary growth and function in periods of metabolic adaptations such as late pregnancy and early lactation. Indeed, different experiments reported that adiponectin and leptin expression varies according to physiological stages and nutritional status of the animal. The current review also demonstrates that adipokines, such as leptin and adiponectin, are important regulators of the action of lactogenic hormones in the mammary gland. Findings also suggest important roles for adipokines in growth and intestinal maturation of the neonate.

Leucine and valine supplementation of low-protein diets for broiler chickens from 21 to 42 days of age.

The objective of this study was to determine the requirements and interactions between the standardized ileal digestible (SID) Leu and Val levels in low-protein diets, and their effects on performance, serum characteristics, carcass yield and diameter of muscle fibers of broiler chickens from d 21 to 42 posthatch. A total of 1,500 21-day-old Cobb 500 male broiler chickens were distributed in a completely randomized design in a 5 × 5 factorial arrangement for a total of 25 treatments with 3 replicates of 20 birds each. Treatments consisted of 5 SID Leu levels (1.0, 1.2, 1.4, 1.6, or 1.8%) and 5 SID Val levels (0.52, 0.67, 0.82, 0.97, or 1.12%). At 42 d of age, there was interaction (P < 0.05) between the SID levels of Leu and Val on feed intake and weight gain. There was a quadratic effect (P < 0.05) of Leu and Val levels on feed conversion, with minimal point estimated at the levels of 1.19 and 0.86%, respectively. Dietary Leu supplementation reduced linearly (P < 0.05) serum concentrations of triglycerides and ß-hydroxybutyrate. Dietary Leu increased (P ≤ 0.05) the fiber diameters of the pectoralis major muscle and breast yield at the levels of 1.24 and 1.13%, respectively, while the thigh yield was improved with the level of 0.71% Val. Abdominal fat decreased linearly (P < 0.05) with increasing levels of dietary Leu and Val. The SID Leu and Val levels needed to optimize weight gain and feed conversion in low-CP diets for broiler chickens from d 21 to 42 posthatch were estimated at 1.15 and 0.86%, and 1.19 and 0.86%, respectively. The supplementation of Leu and Val can reduce the abdominal fat deposition in birds fed low-CP diets during the grower phase. Leu and Val interactions can influence the performance but not the serum characteristics, carcass yield and diameter of muscle fibers of broilers fed low-protein diets. Therefore, it is necessary to consider the dietary Leu content to estimate the ideal level of Val in low-CP diets for optimum broiler performance.

Caecal microbiota of chickens fed diets containing propolis.

The present study aimed to evaluate the effect of different levels of ethanolic extract of propolis (EEP) and raw propolis (RP) on broiler performance and on selected bacterial groups in caecal microbiota using fluorescent in situ hybridization (FISH) measured by fluorescent activated cell sorting. Two experiments were conducted with 120 male chicks from 1 to 21 days of age for each, raised in cages and distributed in a completely randomized experimental design; there were five replicates with four birds per experimental unit and six treatments for each experiment (trial 1 - EEP - 0, 1000, 2000, 3000, 4000 and 5000 ppm and trial 2 - RP - 0, 100, 200, 300, 400 and 500 ppm). Fluorescent probes were used against the bacterial groups in caecal samples collected at 21 days of age. The data were subjected to one-way anova followed by Tukey's and regression analyses were used to assess the relationship between dietary levels of EEP or RP on performance and intestinal microbiota (p < 0.05). In the trial 1, results showed that the EEP did not cause any significant (p > 0.05) modification in the performance and caecal microbiota. In the trial 2, RP inclusion did not affect the performance but changed the bacterial composition (p < 0.05). Clostridiaceae, Gammaproteobacteria excluding Enterobacteriaceae and Lactobacillus spp. showed a quadratic response (p < 0.05), with the lowest value predicted to occur at 240 ppm, 221 ppm and 213 ppm of RP respectively. The proportion of Bacteroidaceae and Gammaproteobacteria did not differ (p > 0.05) among the experimental groups. The inclusion of ethanolic extract of propolis did not affect the performance and intestinal microbiota, whereas the supplementation of raw propolis modulates the caecal microbiota composition without any effects on chicken performance.

Differences in body condition of gilts that are maintained from mating to the end of gestation affect mammary development.

The goal of this project was to determine if different body conditions in late gestation that are due to varying body conditions at mating affect mammary development and mammary gene expression of gilts. Gilts that were fed ad libitum in the growing period were selected based on their backfat depths to form 3 groups at mating, namely, low backfat (LBF; 12-15 mm; = 14), medium backfat (MBF; 17-19 mm; = 15), and high backfat (HBF; 22-26 mm; = 16). During gestation, LBF, MBF, and HBF gilts were fed approximately 1.25, 1.43, and 1.63 times maintenance requirements to maintain their differences in body condition. Feed intake was increased by 1 kg in the last 10 d of gestation. Backfat depths of gilts were ultrasonically measured at mating and on d 30, 50, 70, 100, and 109 of gestation. Blood samples were obtained at mating and on d 109 of gestation to measure concentrations of IGF-1, glucose, insulin, estradiol, urea, free fatty acids, leptin, and adiponectin. Gilts were slaughtered on d 110 of gestation to collect mammary glands for compositional analyses. Mammary extraparenchymal tissue weight was lesser in LBF and MBF gilts than in HBF gilts (1,259.3, 1,402.7, and 1,951.5 ± 70.4 g, respectively; < 0.01). The weight of parenchymal tissue was not affected by treatment ( > 0.10), but its composition was altered. Concentrations of DNA and RNA decreased as backfat depth increased ( < 0.05), whereas percent fat and DM increased ( < 0.05). Circulating concentrations of leptin tended to be lower at mating ( < 0.10) and were lower on d 109 of gestation ( < 0.05) in LBF gilts than in HBF gilts. On d 109 of gestation, concentrations of insulin ( < 0.01) and IGF-1 ( < 0.05) were lower in LBF and MBF gilts than in HBF gilts, whereas those of urea were greater ( < 0.05). The mRNA abundance in parenchymal tissue for all genes studied was not affected by treatments ( > 0.10) with the exception of , which had a greater expression level in LBF gilts than in MFB or HBF gilts ( < 0.05). Percent of Ki-67-positive cells, used to assess mammary cell proliferation rate, was greater in HBF gilts than in LBF gilts ( < 0.05). When differences in body conditions of gilts that were present at mating were maintained throughout gestation, it had an impact on mammary development. Extraparenchymal tissue mass was affected and, more importantly, composition of parenchymal tissue was altered, indicating a beneficial effect of gilts being in the thinner treatment groups at mating.

Body condition of gilts at the end of gestation affects their mammary development.

The impact of body condition at 110 d of gestation on mammary gland development, mammary gene expression, and hormonal and metabolite status of gilts was studied. Thirty-nine gilts were equally divided into 3 groups based on their backfat thickness at the end of gestation: 1) low backfat (LBF; 12-15 mm), 2) medium backfat (MBF; 17-19 mm), or 3) high backfat (HBF; 21-26 mm). Gilts had similar BW (138.1 ± 8.2 kg) and backfat thicknesses (16.4 ± 1.0 mm) at mating and the 3 groups were achieved via ingestion of varying amounts of feed throughout gestation. Jugular blood samples were obtained from all gilts at mating and at 109 d of gestation to assess hormonal and metabolic statuses, and animals were slaughtered on d 110 to collect mammary glands for compositional analyses and for measure of gene expression. The LBF gilts had less extraparenchymal tissue ( < 0.01) and parenchymal tissue ( < 0.05) than HBF gilts. Mammary parenchyma from LBF gilts also tended to contain less DM ( < 0.10), contained more protein ( < 0.05), and had greater RNA concentrations ( < 0.01) than that from HBF gilts. None of the 15 genes studied in mammary parenchymal tissue differed in terms of expression level, and the rate of mammary cell proliferation was similar among treatments ( > 0.10). There was a tendency for circulating leptin concentrations on d 109 of gestation to be lower in LBF gilts than in MBF gilts ( < 0.10), whereas values for HBF gilts did not differ from those of the other treatments ( > 0.10). Current results demonstrate that being too thin at the end of gestation (12-15 mm backfat) has a negative impact on mammary development in gilts, whereas having backfats varying from 17 to 26 mm seems to have no detrimental effects on mammogenesis. Backfat thickness in late pregnancy must therefore be considered to achieve optimal sow lactation performance.

Valine, isoleucine, arginine and glycine supplementation of low-protein diets for broiler chickens during the starter and grower phases.

1. Two experiments were performed to study the supplementation of valine, isoleucine, arginine and glycine (Val, Ile, Arg, Gly) in low-protein diets for broiler chickens in the starter (1-21 d; Exp. 1) and grower (22-42 d; Exp. 2) phases. 2. A low-crude protein (CP) diet was formulated to meet the requirements of all amino acids (AA) supplied by the control diet except for Val, Ile, Arg and Gly. The other experimental diets were obtained by the isolated or combined supplementation of the studied AA in the low-CP diet. 3. Growth, serum parameters and litter characteristics were taken in both of the experiments. Carcass measurements were taken in Experiment 2. 4. In the starter and grower phases, low-CP diets without supplementation resulted in birds with a poorer weight gain and feed conversion than those of the birds that received the control diet. 5. In the starter phase, individual supplementation with Val and Gly, but not Ile and Arg, restored the weight gain of the birds, while diets with the addition of Val + Gly, Val + Ile + Arg, Val + Ile + Gly and Val + Ile + Arg + Gly restored their feed conversion. 6. In the grower phase, weight gain was re-established at the same rate as the control diet for the diets supplemented with Val + Ile, Val + Ile + Arg, Val + Ile + Gly and Val + Ile + Arg + Gly. However, the feed conversion was restored only in birds that received the diet supplemented with all studied AA. 7. The supplementation of Val and Gly in low-CP diets was sufficient to avoid adverse effects in the performance and serum parameters of broilers in the starter phase. However, birds in the grower phase required the combined supplementation of Val, Ile, Arg and Gly, to prevent compromised performance.

Effect of dietary supplementation with an ethanolic extract of propolis on broiler intestinal morphology and digestive enzyme activity.

The present study aimed to evaluate the effect of different levels of an ethanolic extract of propolis (EEP) on broiler performance, carcass characteristics, weight of gastrointestinal organs, intestinal morphometry and digestive enzyme activity. 1020 male broiler chicks were assigned in a completely randomised experimental design to six treatments (EEP supplement levels of 0, 1000, 2000, 3000, 4000 and 5000 ppm) and five replications, and 34 birds per experimental unit. The experimental diets were administered from 1 to 21 days of age, and the birds were subsequently provided a ration based on corn and soybean meal. EEP supplementation from 1 to 7 days negatively affected (p < 0.05) the weight gain and feed intake. The proventriculus weight at 7 days exhibited a quadratic response (p < 0.05), which predicted a lower weight at a dose of 2865 ppm of the EEP. For the duodenum at 21 days of age, the response pattern (p < 0.05) predicted that birds that were fed 2943 and 3047 ppm of the EEP would exhibit an improved crypt depth and villus-to-crypt ratio respectively. The villus height, crypt depth and villus-to-crypt ratio in the jejunum and the ileum were not affected (p > 0.05). With increased EEP doses, the duodenal sucrase activity linearly decreased at 7 days of age and linearly increased in the jejunum at 21 days of age (p < 0.05), while pancreatic enzyme activity was unaffected (p > 0.05). Although the carcass and cut yields did not improve, the percentage of abdominal fat decreased (p < 0.05). The supplementation of the broiler pre-starter diet with 1000-5000 ppm of the EEP impaired performance at this stage, most likely due to the decreased sucrase activity. However, the EEP supplementation from 3000 ppm improved intestinal morphophysiology at 21 days of age and did not affect the performance or carcass yield at 42 days of age.

Characterization of the bacterial microbiota of Biomphalaria glabrata (Say, 1818) (Mollusca: Gastropoda) from Brazil.

UNLABELLED: Roughly 200 000 000 people in 74 countries infected with schistosomes all share the fact that they came in contact freshwater harbouring infected snails. The aim of the study is to characterize the microbiota of wild and laboratory-reared snails of Biomphalaria glabrata from Pernambuco, Brazil. The microbiota of these molluscs was identified biochemically by the VITEK 2 automated microbiological system. Antimicrobial susceptibility testing was carried out by the disc diffusion method with ß-lactam antibiotics, aminoglycosides, quinolones, folate pathway inhibitors, fenicols and tetracyclines. The results showed that all bacteria identified were gram-negative, including 11 bacterial genera: Aeromonas, Citrobacter, Enterobacter, Cupriavidus, Rhizobium, Stenotrophomonas, Pseudomonas, Klebsiella, Acinetobacter, Vibrio and Sphingomonas. Regarding the antimicrobial susceptibility, all the isolates exhibited resistance to amoxicillin and sensitivity to meropenem (beta-lactam antimicrobials). The microbiota of the wild snails consisted predominantly of Enterobacter cloacae, while the laboratory-reared snails predominantly showed Citrobacter freundii and Aeromonas sobria. SIGNIFICANCE AND IMPACT OF THE STUDY: Biomphalaria glabrata is a Brazilian freshwater Planorbidae of great medical relevance as an intermediate host of Schistosoma mansoni. About a month after being infected by one or more miracidia larvae of a compatible schistosome, B. glabrata sheds thousands of cercariae into the water where they seek human skin and, if successful, penetrate to establish infection, eventually taking up residence and maturing in blood vessels of the small intestine. Results obtained from this study aim at targeting novel biological control strategies for schistosomiasis such as paratransgenesis. This is the first study on the microbiota of B. glabrata from Brazil.

Commercially available amino acid supplementation of low-protein diets for broiler chickens with different ratios of digestible glycine+serine:lysine.

This work studied the effect of supplementing commercially available amino acids in low-protein diets using different ratios of digestible (dig) glycine+serine:lysine (Gly+Ser:Lys) on performance, serum parameters, feathering, and litter characteristics of broiler chickens during the starter period. A total of one thousand fifty 1-d-old Cobb-Vantress male chicks were distributed in a completely randomized experimental design into 6 treatments with 5 replicates of 35 birds each. The treatments were as follows: T1, control diet based on corn and soybean meal formulated with 22% CP (dig Gly+Ser:Lys ratio of 147); T2, diet with a 2% CP reduction, supplemented with Val (dig Gly+Ser:Lys ratio of 137); T3, similar to T2 with the addition of Gly (dig Gly+Ser:Lys ratio of 147); T4, diet with a 3% CP reduction, supplemented with Val, Ile, and Arg (dig Gly+Ser:Lys ratio of 127); and T5 and T6, similar to T4 with the addition of Gly (dig Gly+Ser:Lys ratios of 137 and 147, respectively). At 7 and 21 d, broilers that had received diets with a 3% CP reduction (19% CP) and a Gly+Ser:Lys ratio that was equivalent to 127 had lower G:F (P < 0.05) and lower total protein and albumin serum concentrations (P < 0.05) than those broilers that received the control feed. However, these parameters were restored to the same level as the control diet with an increase in the dig Gly+Ser:Lys ratio from 127 to 137 and 147. Diets with a 3% CP reduction (19% CP) resulted in litter with reduced (P < 0.05) nitrogen content and lower ammonia emission than the litter of broilers receiving the control diet. The treatments did not influence (P > 0.05) the feather length or feathering scores at 21 or 28 d of age. The supplementation of essential amino acids while maintaining dig Gly+Ser:Lys ratios at and above 137 allowed for a reduction in the dietary CP of 3% without undermining the performance, feathering or serum parameters of early stage broilers.

Messenger ribonucleic acid abundance of intestinal enzymes and transporters in feed-restricted and refed chickens at different ages.

The effects of feed restriction and subsequent refeeding on the gene expression of intestinal enzymes and nutrient transporters at 2 ages, 7 and 35 d, were examined in different groups of broiler chickens. At each age, birds were feed restricted for 7 d (30% of ad libitum intake) followed by 3 d of refeeding ad libitum. Control groups were fed ad libitum. Total RNA of jejunal mucosa was extracted according to the Trizol protocol, and mRNA expression of sodium glucose transporter 1, glucose transporter 2, peptide transporter 1, aminopeptidase, maltase, and sucrase-isomaltase complex was obtained by reverse-transcription PCR. The expression of aminopeptidase, sodium glucose transporter 1, and peptide transporter 1 was higher in feed-restricted groups than in control groups at d 14 (181.4, 116.7, and 80.4%, respectively) and d 42 (143.5, 84.2, and 195.9%, respectively). The mRNA abundance of sucrase-isomaltase complex was higher (159.1%) only in chickens that were feed restricted from d 35 to 42. No statistically significant effect of feed restriction was observed for mRNA abundance of maltase and glucose transporter 2 at either age. After refeeding (d 17 and 45), the RNA abundance of enzymes and nutrient transporters was similar to that in the control group. Thus, this study suggests that an effect of upregulation in gene expression exists during feed restriction that disappears when feed is supplied ad libitum.

Environmental color affects Nile tilapia reproduction.

We investigated the effects of environmental color on the reproductive behavior of Nile tilapia, Oreochromis niloticus. Two environmental colors were tested by covering the aquarium (60 x 60 x 40 cm) with white (12 groups) or blue (13 groups) cellophane and observing reproductive behavior in groups of 2 males (10.27 +/- 0.45 cm) and 3 females (10.78 +/- 0.45 cm) each. After assignment to the respective environmental color (similar luminosity = 100 to 120 Lux), the animals were observed until reproduction (identified by eggs in the female's mouth) or up to 10 days after the first nest building. Photoperiod was from 6:00 h to 18:00 h every day. Food was offered in excess once a day and water quality was similar among aquaria. Daily observations were made at 8:00, 11:00, 14:00 and 17:00 h regarding: a) latency to the first nest, b) number of nests, c) gravel weight removed (the male excavates the nest in the bottom of the aquarium), d) nest area, and e) mouthbrooding incubation (indication of reproduction). The proportion of reproducing fish was significantly higher (6 of 13) in the group exposed to the blue color compared the group exposed to the white color (1 of 12; Goodman's test of proportions). Moreover, males under blue light removed significantly larger masses of gravel (blue = 310.70 +/- 343.50 g > white = 130.38 +/- 102.70 g; P = 0.01) and constructed wider nests (blue = 207.93 +/- 207.80 cm(2) > white = 97.68 +/- 70.64 cm(2); P = 0.03) than the control (white). The other parameters did not differ significantly between light conditions. We concluded that reproduction in the presence of blue light was more frequent and intense than in the presence of white light.

Environmental color affects Nile tilapia reproduction

We investigated the effects of environmental color on the reproductive behavior of Nile tilapia, Oreochromis niloticus. Two environmental colors were tested by covering the aquarium (60 x 60 x 40 cm) with white (12 groups) or blue (13 groups) cellophane and observing reproductive behavior in groups of 2 males (10.27 ± 0.45 cm) and 3 females (10.78 ± 0.45 cm) each. After assignment to the respective environmental color (similar luminosity = 100 to 120 Lux), the animals were observed until reproduction (identified by eggs in the female's mouth) or up to 10 days after the first nest building. Photoperiod was from 6:00 h to 18:00 h every day. Food was offered in excess once a day and water quality was similar among aquaria. Daily observations were made at 8:00, 11:00, 14:00 and 17:00 h regarding: a) latency to the first nest, b) number of nests, c) gravel weight removed (the male excavates the nest in the bottom of the aquarium), d) nest area, and e) mouthbrooding incubation (indication of reproduction). The proportion of reproducing fish was significantly higher (6 of 13) in the group exposed to the blue color compared the group exposed to the white color (1 of 12; Goodman's test of proportions). Moreover, males under blue light removed significantly larger masses of gravel (blue = 310.70 ± 343.50 g > white = 130.38 ± 102.70 g; P = 0.01) and constructed wider nests (blue = 207.93 ± 207.80 cm² > white = 97.68 ± 70.64 cm²; P = 0.03) than the control (white). The other parameters did not differ significantly between light conditions. We concluded that reproduction in the presence of blue light was more frequent and intense than in the presence of white light.

Eye color as an indicator of social rank in the fish Nile tilapia.

We investigated the association of eye color with the dominant-subordinate relationship in the fish Nile tilapia, Oreochromis niloticus. Eye color pattern was also examined in relation to the intensity of attacks. We paired 20 size-matched fish (intruder: 73.69 11.49 g; resident: 75.42 8.83 g) and evaluated eye color and fights. These fish were isolated in individual aquaria for 10 days and then their eye color was measured 5 min before pairing (basal values). Twenty minutes after pairing, eye color and fights were quantified for 10 min. Clear establishment of social hierarchy was observed in 7 of 10 pairs of fish. Number of attacks ranged from 1 to 168 among pairs. The quartile was calculated for these data and the pairs were then divided into two classes: low-attack (1 to 111 attacks - 2 lower quartiles) or high-attack (112 to 168 attacks - 2 higher quartiles). Dominance decreased the eye-darkening patterns of the fish after pairing, while subordinance increased darkening compared to dominance. Subordinate fish in low-attack confrontations presented a darker eye compared to dominant fish and to the basal condition. We also observed a paler eye pattern in dominants that shared low-attack interactions after pairing compared to the subordinates and within the group. However, we found no differences in the darkening pattern between dominants and subordinates from the high-attack groups. We conclude that eye color is associated with social rank in this species. Moreover, the association between eye color and social rank in the low-attack pairs may function to reduce aggression.

Eye color as an indicator of social rank in the fish Nile tilapia

We investigated the association of eye color with the dominant-subordinate relationship in the fish Nile tilapia, Oreochromis niloticus. Eye color pattern was also examined in relation to the intensity of attacks. We paired 20 size-matched fish (intruder: 73.69 ± 11.49 g; resident: 75.42 ± 8.83 g) and evaluated eye color and fights. These fish were isolated in individual aquaria for 10 days and then their eye color was measured 5 min before pairing (basal values). Twenty minutes after pairing, eye color and fights were quantified for 10 min. Clear establishment of social hierarchy was observed in 7 of 10 pairs of fish. Number of attacks ranged from 1 to 168 among pairs. The quartile was calculated for these data and the pairs were then divided into two classes: low-attack (1 to 111 attacks - 2 lower quartiles) or high-attack (112 to 168 attacks - 2 higher quartiles). Dominance decreased the eye-darkening patterns of the fish after pairing, while subordinance increased darkening compared to dominance. Subordinate fish in low-attack confrontations presented a darker eye compared to dominant fish and to the basal condition. We also observed a paler eye pattern in dominants that shared low-attack interactions after pairing compared to the subordinates and within the group. However, we found no differences in the darkening pattern between dominants and subordinates from the high-attack groups. We conclude that eye color is associated with social rank in this species. Moreover, the association between eye color and social rank in the low-attack pairs may function to reduce aggression.

Effects of melatonin on orofacial movements in rats.

RATIONALE: While reserpine-induced oral movements (OM), an animal model of tardive dyskinesia, are more persistent in old than in adult rats, old animals present spontaneous OM, which are phenomenologically similar to those presented by reserpine-treated adult rats. We postulate that these OM may be the result of oxidative stress induced by both age and reserpine treatment. OBJECTIVES: We intended to determine the preventative effects of exogenous melatonin (one of the most important endogenous antioxidants) as well as suppression of endogenous melatonin via continuous exposure to light on reserpine- or age-induced OM in rats. METHODS: Adult (4 months of age) male Wistar rats were repeatedly treated with saline or melatonin (5 mg/kg, IP) and saline or reserpine and kept under a 12-h light/dark cycle for quantification of reserpine-induced OM as well as oxidative stress (via quantification of lipid peroxidation). To verify the effects of endogenous melatonin suppression on reserpine-induced OM, adult rats were repeatedly treated with saline or reserpine and continuously exposed to light. To verify the effects of exogenous melatonin on age-induced OM older (20 months of age) rats were long-term treated with saline or melatonin and kept under a 12-h light/dark cycle. RESULTS: Melatonin attenuated both reserpine- and age-induced OM. Reserpine enhanced striatal lipid peroxidation, that was prevented by melatonin co-administration. Continuous exposure to light increased spontaneous as well as reserpine-induced OM, indicating that endogenous melatonin may be involved in this movement disorder. CONCLUSIONS: We suggested that melatonin attenuates both reserpine- and age-induced OM in rats.