Establishing New Isosexual Pairs in Adult Male Guinea Pigs (Cavia porcellus) to Facilitate Social Housing.

Guinea pigs (Cavia porcellus) are a commonly used species in biomedical research. As social creatures, compatible guinea pigs should be housed together unless scientific objectives or veterinary care require otherwise. Extensive literature suggests that adult male guinea pigs are highly aggressive in the presence of females, but data are lacking regarding the compatibility of cohoused adult males in the absence of females. Most studies that use adult males do not report housing densities. We used serial wound scoring and observations of behavior to determine whether unfamiliar adult male guinea pigs will develop stable, prosocial isosexual pairs. Wound scoring was performed before and 24 h after pairing. Serial behavioral observations assessed affiliative and agonistic behaviors at 0.5, 2, 24, and 48 h after pairing. Wound scoring and behavioral observations continued weekly for 1 mo and monthly thereafter. Wound scores were significantly higher at 24 h after pairing as compared with baseline and all other time points. Wounding was rare after week 2, indicating reduced aggression. Furthermore, affiliative behaviors significantly increased over time while agonistic behaviors were rare. Together, these data suggest that unfamiliar adult male guinea pigs establish stable prosocial pairs after an acclimation period. As was done in the present study, providing ample space, separate shelters for each animal, and the absence of female guinea pigs will likely facilitate successful pairing. We recommend consideration of a social housing program for adult male guinea pigs to provide companionship and enrich their housing environment.

Measuring ramp use in guinea pigs (Cavia porcellus).

To investigate the utility of ramps as enrichment and as a method for establishing demand for commodities, the latency to climb a ramp of increasing slope to obtain food was measured in four guinea pigs. The average height where guinea pigs failed to climb was 29.1 cm (slope 14.2 degrees). In addition, the increasing slope altered climbing behavior; when climbing speed was tested using the same slope for all trials within a single session, the guinea pigs maintained their climbing speed as the gradient increased across sessions. In comparison, when the slope was increased with each successful climb within a session, climbing speed was not maintained. Installing the maximum slope climbed can promote increased exercise and foraging but avoid physical harm or barriers to resources. Furthermore, these results indicate that climbing, a simple behavior with measurable differences as a function of slope and thus, effort, could be used as a method for testing the demand for commodities, such as food type or enrichment items, to be included in the husbandry of guinea pigs to improve welfare of the small cavy.

Growth performance and reproductive function impairment of glyphosate-based herbicide in male guinea pig (Cavia porcellus).

Glyphosate formulations, widely applied non-selective systemic herbicides, are progressively becoming the most controversial pesticides on the market due the adverse effects they pose to humans and environment. The information on these potential hazardous effects to the handlers of the pesticide remains obscure. This study investigated effects of glyphosate-based herbicide on growth performance, seminal parameters and hemato-biochemical profiles in male guinea pig. Forty sexually mature male guinea pigs weighing between 393.3 and 418.4 g were divided into four groups of 10 animals each and orally administered 0, 186, 280 and 560 mg/kg body weight of WILLOSATE daily for 60 days. Daily feed intake and body weight gain were recorded. At the end of experimental period all animals were humanely sacrificed, and blood samples and vital organs were collected for appropriate analysis. Results showed a significant decrease (p < 0.05) in body weight gain (-102.2%), final body weight (-9.8%) and feed intake (-13.1%) of animals following sub-chronic exposure of WILLOSATE. The weights of the liver and kidney increased significantly (p < 0.05) by 25.4% and 28.8%, respectively, while testicular weights decreased (p < 0.05) by 24% with increasing doses of WILLOSATE. A decrease in sperm motility (-67.9%), viability (-52.7%) and concentration per vas deferens (-40.7%), and an increase in sperm major (28.1%) and minor (45.3%) morphological aberrations were recorded in WILLOSATE - exposed guinea pigs when compared to controls. There was a dose-dependent increase (p < 0.05) in MCV and WBC and a decrease in Hb content and RBC, as well as serum content in total protein (-11.8%). The serum content of cholesterol (37.8%), urea (87.1%), creatinine (22.4%), ALAT (74.2%) and ASAT (88.7%) were significantly higher in treated groups compared to controls. These results point toward the toxic effects of WILLOSATE on vital organs and reproductive function of the body at high doses and long-term exposure.

Effect of Photoperiod with Sunlight at Thermal Stress and Sperm Parameters in Guinea Pigs.

<b>Background and Objective:</b> Photoperiod can regulate reproductive physiological processes in mammals, in which improvements in testosterone concentration, testicular volume and seminal quality have been reported. The aim was to evaluate the influence of photoperiod treatments on guinea pigs' spermatic parameters. <b>Materials and Methods:</b> Thirty guinea pigs, between males and females, were distributed in two rooms with the photoperiodic treatment of 10 hrs light and 14 hrs dark (PT₁ with artificial photoperiod and PT₂ photoperiod with sunlight by opening windows from 08:00-18:00) and one without any direct light stimulus (PT₀) for 78 days. The temperature and humidity were recorded and the TH index was calculated for each room. The sperms were recovered in Tris base medium from the epididymis of 16 males to determine sperm concentration, motility, kinetic parameters, vitality, HOST, acrosomal integrity and DNA fragmentation. <b>Results:</b> Sperm values in PT₁ and PT₀ were similar but PT₂ obtained values lower in sperm concentration, non-progressive motility, total motility, VCL, ALH, vitality, HOST+, acrosomal integrity, sperm with non-fragmented DNA and no pregnancies were reported (0/5). A 100% pregnancy was observed in PT₀ (4/4) and 50% in PT₁ (2/4). However, precocity was evidenced in PT₁ compared to PT₀. PT₂ recorded higher peaks in temperature (33.8°C, THI 81, considered as thermal stress) compared to PT₀ (32.65°C, THI 81.8) and PT₁ (32.75°C, THI 81.6). <b>Conclusion:</b> An artificial photoperiod can improve sperm characteristics and reproductive precociousness of guinea pigs, unlike the photoperiod with sunlight, which generated low spermiogram values and absence of pregnancy due to thermal stress.

Water consumption in small mammals (dwarf rabbits, Guinea pigs and chinchillas): New data about possible influencing factors.

Information on water requirement of small mammals is sparse and the assessment of daily water consumption is an important aspect of the veterinary practice in exotic pet nutrition. Water and feed daily intake are interlaced, that way the water to feed ratio is a meaningful indication. However, various factors such as ambient temperature or the uptake of substances to be eliminated via the kidney (i.e. calcium) must be taken into account when estimation of water consumption is carried out. Moreover, behavioural abnormalities could affect water consumption, like in the case of water uptake as a substitute action. Adequate water supply for small mammals is indispensable for health reasons (prophylaxis of urolithiasis) and consequences relevant to animal welfare. For this purpose, data from different trials enrolling no. 5 Flemish Belgian (FB) and no. 5 New Zealand White (NZW) rabbits, no. 10 dwarf rabbits, no. 7 guinea pigs and no. 7 chinchilla, were obtained to assess water intake according to feed rationing. Water balance following feed rationing was seen to differ across the species of small mammals considered in these trials. The comparative approach pointed to species-dependent water intake behaviour. Due to the species-related high variation in water uptake, it is not possible to give general recommendations for water supply of small mammals. In addition, water uptake is also influenced by the water content of the food, absolute dry matter uptake and food composition. Nevertheless, an additional supply of drinking water is recommended for all species, since unsatisfactory water supply reduces dry matter intake and may lead to energy undersupply.

Optical Aberrations of Guinea Pig Eyes.

Purpose: The guinea pig is widely used in studies of refractive error development and myopia which often involve experimental optical manipulations. The study described here investigated the optical quality of the guinea pig eye, for which there are limited data, despite its fundamental importance to understanding visually guided eye growth. Methods: The ocular aberrations of eight adolescent New Zealand pigmented guinea pigs (6-11 weeks old) were measured after cycloplegia using a custom-built Shack-Hartmann aberrometer and fit with a Zernike polynomial function to the 10th order (65 terms). The optical quality of their eyes was assessed in terms of individual Zernike coefficients, and data were further analyzed to derive root-mean-square (RMS) wavefront errors, modulation transfer functions (MTFs), point spread functions (PSFs), Strehl ratios, and depth of focus. A 4-mm pupil was used in all computations. The derived data are compared with equivalent data from normal young adult human eyes. Results: The guinea pigs exhibited low hyperopia and a small amount of positive spherical aberration, with other aberration terms decreasing with increasing order. Their average depth of focus, estimated from through-focus modulation, was 3.75 diopters. The RMS wavefront error of the guinea pig eye was found to be larger than that of the human eye for the same pupil size, reflecting a higher degree of aberrations, although the PSF (area) on the retina was smaller and sharper due to its shorter focal length. The radial average best-focus MTF derived for the guinea pig eye showed good performance at very low spatial frequencies, with a steeper decline with increasing frequency than for the human eye, dropping below 0.3 at 9 cpd. When converted to linear units (cycles/mm), the guinea pig eye had a higher spatial frequency cutoff and a slight contrast advantage for low spatial frequencies compared to the human eye. Conclusions: The optical quality of the guinea pig eye is far superior to their reported behavioral visual acuity. This implies a neuroanatomical limit to their vision, which contrasts with the close match of optical and neural limits to spatial resolution in human eyes. The significance for eye growth regulation of the relative optical advantages exhibited by guinea pig eyes, when optical quality is expressed in linear rather than angular retinal units, warrants further consideration.

Back to the future: re-establishing guinea pig in vivo asthma models.

Research using animal models of asthma is currently dominated by mouse models. This has been driven by the comprehensive knowledge on inflammatory and immune reactions in mice, as well as tools to produce genetically modified mice. Many of the identified therapeutic targets influencing airway hyper-responsiveness and inflammation in mouse models, have however been disappointing when tested clinically in asthma. It is therefore a great need for new animal models that more closely resemble human asthma. The guinea pig has for decades been used in asthma research and a comprehensive table of different protocols for asthma models is presented. The studies have primarily been focused on the pharmacological aspects of the disease, where the guinea pig undoubtedly is superior to mice. Further reasons are the anatomical and physiological similarities between human and guinea pig airways compared with that of the mouse, especially with respect to airway branching, neurophysiology, pulmonary circulation and smooth muscle distribution, as well as mast cell localization and mediator secretion. Lack of reagents and specific molecular tools to study inflammatory and immunological reactions in the guinea pig has however greatly diminished its use in asthma research. The aim in this position paper is to review and summarize what we know about different aspects of the use of guinea pig in vivo models for asthma research. The associated aim is to highlight the unmet needs that have to be addressed in the future.

Investigation of Various Intramuscular Volumes Delivered to the Semimembranosus Muscle of Cavia porcellus.

The goal of this study is to provide quantitative data on the ideal volume for intramuscular (IM) injections into the semimembranosus muscle of guinea pigs weighing between 320 to 410 grams. This evaluation comprised 2 experiments. The first was to assess dispersion leakage of intramuscularly injected iohexol, a radiocontrast agent commonly used in Computed Tomography (CT), based on analysis of in vivo imaging. The second used varying volumes of intramuscularly injected sodium chloride (0.9% NaCl) to assess pain and pathology associated with IM injection. Hartley guinea pigs were injected IM with varying volumes of either iohexol or sodium chloride (150, 300, 500, 1000 and 1500 µL). In the iohexol experiment, results suggest IM volumes of 150 and 300 µL remain within the target muscle. In the experiment using sodium chloride, pain and pathology did not increase as IM volume increased. The pathology noted was related to needle tract through the musculature rather than the volume size of the injectate. The results did not reveal a correlation between volume of IM 0.9% NaCl and pain levels. We conclude that volume size correlates more with precision and accuracy of delivery into the intended muscle tissue. Regarding tissue distribution, our findings also suggest that the optimal capacity for IM injection in the semimembranosus muscle should be less than 500 µL.

Two-dimensional, M-mode, and Doppler echocardiography in 22 conscious and apparently healthy pet guinea pigs.

OBJECTIVES: The objective of this study was to report normal echocardiographic values in healthy guinea pigs. ANIMALS, MATERIALS, AND METHODS: Twenty-two privately owned, apparently healthy, conscious guinea pigs underwent complete transthoracic echocardiography. Left ventricular (LV), right ventricular, left atrial, and aortic root dimensions were measured, as were forward flow velocities across the mitral, aortic, and pulmonic valves. The effects of age, body weight, sex, and heart rate on these variables were also investigated. RESULTS: The median age (interquartile range) was 3.0 (1.8-4.0) years with a body weight of 902 (822-998) grams. Echocardiography was feasible in all conscious animals. Early and late diastolic transmitral flow waves were summated in 17 of 22 individuals. In the remaining five animals, the two waves were reversed (E wave-to-A wave velocity less than 1.0). A positive correlation was detected between body weight and LV internal diameter at end-diastole and end-systole and left atrial diameter (P < 0.05). Heart rate was negatively correlated with LV internal diameter at end-systole (r = -0.463, P = 0.035). Age was positively correlated with LV posterior wall thickness at end-diastole and aortic diameter (P < 0.05). LV internal diameter at end-systole was larger in males than in females (P = 0.012), while fractional shortening was lower (P = 0.008). CONCLUSIONS: Descriptive echocardiography ranges in apparently healthy awake guinea pigs have been provided and can be used for cardiac assessment in these pet animals.

Measurement of tear production and establishment of reference values in guinea pigs (Cavia porcellus) using a modified Schirmer tear test.

BACKGROUND: Past studies have shown that 5-mm Schirmer tear tests (STTs) are difficult to interpret in guinea pigs. Modified 2.5-mm STT strips are more adequate for measuring the small volume of tear production in these animals. The aim of this study was to establish reference values for the modified 2.5-mm STT strips. METHODS: Modified STT measurements were performed in random order in both eyes of 50 guinea pig patients. The wetting of the strip was noted at 30 seconds and at 1 minute. RESULTS: The mean±sd STT values for both eyes were 7.58±3.19 mm at 30 seconds and 10.42±3.92 mm at 60 seconds. The median was 8 mm at 30 seconds and 10 mm at 60 seconds for both eyes. Animals under one year of age had lower STT values. STT values at 30 and 60 seconds can both be used. Both eyes should be measured when possible. CONCLUSION: The authors recommend values above 8 mm at 30 seconds and 10 mm at 60 seconds to be considered normal when using a 2.5-mm STT strip. There are ambiguous areas at 5-8 mm and 6-10 mm. If in these ranges the results should be combined with clinical signs and judgement.

Use of the guinea pig in studies on the development and prevention of acquired sensorineural hearing loss, with an emphasis on noise.

Guinea pigs have been used in diverse studies to better understand acquired hearing loss induced by noise and ototoxic drugs. The guinea pig has its best hearing at slightly higher frequencies relative to humans, but its hearing is more similar to humans than the rat or mouse. Like other rodents, it is more vulnerable to noise injury than the human or nonhuman primate models. There is a wealth of information on auditory function and vulnerability of the inner ear to diverse insults in the guinea pig. With respect to the assessment of potential otoprotective agents, guinea pigs are also docile animals that are relatively easy to dose via systemic injections or gavage. Of interest, the cochlea and the round window are easily accessible, notably for direct cochlear therapy, as in the chinchilla, making the guinea pig a most relevant and suitable model for hearing. This article reviews the use of the guinea pig in basic auditory research, provides detailed discussion of its use in studies on noise injury and other injuries leading to acquired sensorineural hearing loss, and lists some therapeutics assessed in these laboratory animal models to prevent acquired sensorineural hearing loss.

The way wear goes: phytolith-based wear on the dentine-enamel system in guinea pigs (Cavia porcellus).

The effect of phytoliths on tooth wear and function has been contested in studies of animal-plant interactions. For herbivores whose occlusal chewing surface consists of enamel ridges and dentine tissue, the phytoliths might particularly erode the softer dentine, exposing the enamel ridges to different occlusal forces and thus contributing to enamel wear. To test this hypothesis, we fed guinea pigs (Cavia porcellus; n = 36 in six groups) for three weeks exclusively on dry or fresh forage of low (lucerne), moderate (fresh timothy grass) or very high (bamboo leaves) silica content representing corresponding levels of phytoliths. We quantified the effect of these treatments with measurements from micro-computed tomography scans. Tooth height indicated extreme wear due to the bamboo diet that apparently brought maxillary incisors and molars close to the minimum required for functionality. There were negative relationships between a cheek tooth's height and the depth of its dentine basin, corroborating the hypothesis that dentine erosion plays an important role in herbivore tooth wear. In spite of lower body mass, bamboo-fed animals paradoxically had longer cheek tooth rows and larger occlusal surfaces. Because ever-growing teeth can only change in shape from the base upwards, this is a strong indication that failure to compensate for wear by dental height-growth additionally triggered general expansive growth of the tooth bases. The results suggest that enamel wear may intensify after enamel has been exposed due to a faster wear of the surrounding dentine tissue (and not the other way around), and illustrate a surprising plasticity in the reactivity of this rodent's system that adjusts tooth growth to wear.

Scaling Principles of Distributed Circuits.

Identifying shared quantitative features of a neural circuit across species is important for 3 reasons. Often expressed in the form of power laws and called scaling relationships [1, 2], they reveal organizational principles of circuits, make insights gleaned from model systems widely applicable, and explain circuit performance and function, e.g., visual circuits [3, 4]. The visual circuit is topographic [5, 6], wherein retinal neurons target and activate predictable spatial loci in primary visual cortex. The brain, however, contains many circuits, where neuronal targets and activity are unpredictable and distributed throughout the circuit, e.g., olfactory circuits, in which glomeruli (or mitral cells) in the olfactory bulb synapse with neurons distributed throughout the piriform cortex [7-10]. It is unknown whether such circuits, which we term distributed circuits, are scalable. To determine whether distributed circuits scale, we obtained quantitative descriptions of the olfactory bulb and piriform cortex in six mammals using stereology techniques and light microscopy. Two conserved features provide evidence of scalability. First, the number of piriform neurons n and bulb glomeruli g scale as n∼g3/2. Second, the average number of synapses between a bulb glomerulus and piriform neuron is invariant at one. Using theory and modeling, we show that these two features preserve the discriminatory ability and precision of odor information across the olfactory circuit. As both abilities depend on circuit size, manipulating size provides evolution with a way to adapt a species to its niche without designing developmental programs de novo. These principles might apply to other distributed circuits like the hippocampus.

Effects of feeding flaxseed on performance, carcass trait, and meat fatty acid composition of Guinea pigs (Cavia procellus) under northern Peruvian condition.

A study was conducted to determine the effects of flaxseed supplementation on performance, carcass traits, and hindleg fatty acid composition of guinea pigs. Sixty male and female weaned guinea pigs (1 month old, five animals/cage) were blocked by sex and bodyweight and randomly fed 0 (control) or 100 g/kg flaxseed concentrate diets (15 g/animal) plus ad libitum fresh alfalfa for 30 days. Results showed that flaxseed supplementation had no influence on animal performance. However, final body weight (P = 0.035), total feed intake (P = 0.019), and body weight gain (P < 0.001) were higher in male than female guinea pigs. Similar results were also observed for carcass composition (i.e., hot, chilled, and reference carcass weights). Inclusion of flaxseed reduced saturated (P < 0.001), mono-unsaturated (P = 0.004), and increased (P < 0.001) polyunsaturated (PUFA) fatty acid concentrations in hindlegs. Concentrations of linolenic acid and n-3 PUFA increased (P < 0.001) by 49.7 and 37.1%, respectively as a result of flaxseed inclusion. It was concluded that feeding flaxseed to guinea pigs at 100 g/kg of the concentrate diets improves meat PUFA concentrations with no adverse effects on performance or carcass composition.

Hearing differences in Hartley guinea pig stocks from two breeders.

Across the world, dozens of outbred Hartley guinea pig stocks are used for auditory experiments. The genetic makeup of these different stocks will differ due to differences in breeding protocols, history and genetic drift. In fact, outbred breeding protocols are not intended to produce genetically identical animals, neither across breeders, nor across time. For this reason, it is unclear how reproducible experimental results are likely to be using animals from different stocks. We evaluated the consistency of cochlear function using both clicks and tones in Hartley guinea pigs as a function of breeder (Kuiper and Charles River) and sex using archival Auditory Brain Stem Response (ABR) data and tissue from our own laboratory. Sound levels required to reach baseline threshold for click-induced ABRs were similar between male Charles River and male Kuiper guinea pig stocks. However, the median and average thresholds after exposure to high level noise were larger in the Kuiper population than in the Charles River population with corresponding threshold shifts higher in the Kuiper than in the Charles River animals. We evaluated the relationship between pure-tone thresholds and sex, age, breeder stock, left or right cochleas, weight and 5 test frequencies before and after noise exposure using a linear mixed statistical model. Across all frequencies, the effect of breeder on baseline threshold is statistically significant, with effect sizes most pronounced at the lower frequencies before exposure to noise. After noise exposure, the differences are minimal in the model, indicating that differences in threshold shift are chiefly due to differences in initial baseline hearing. However, a contingency calculation comparing response/no response at the highest speaker output at 32 kHz gave a statistically significant difference between the stocks: 28% of Kuiper cochleas responded to the highest output of the speaker as compared with 71.4% of Charles River cochleas, indicating that noise exposure induced a larger threshold shift in a greater proportion of Kuiper animals. Using our archival cochlear tissue from these studies, we confirmed the sex of each animal by PCR, then compared males and females of the Kuiper stock. Across all baseline frequencies, the effect of sex on threshold is statistically significant, with no noticeable difference after exposure. The effect sizes for baseline thresholds are most pronounced at lower frequencies. These data demonstrate that Hartley guinea pig stocks from different breeders are not uniform in their auditory characteristics, and that due to these differences, results and conclusions can differ among laboratories. Moreover, within a single stock, males and females can provide different data, confirming that male and female animals must be individually evaluated in any auditory protocol.

Voltage readout from a piezoelectric intracochlear acoustic transducer implanted in a living guinea pig.

The ability to measure the voltage readout from a sensor implanted inside the living cochlea enables continuous monitoring of intracochlear acoustic pressure locally, which could improve cochlear implants. We developed a piezoelectric intracochlear acoustic transducer (PIAT) designed to sense the acoustic pressure while fully implanted inside a living guinea pig cochlea. The PIAT, fabricated using micro-electro-mechanical systems (MEMS) techniques, consisted of an array of four piezoelectric cantilevers with varying lengths to enhance sensitivity across a wide frequency bandwidth. Prior to implantation, benchtop tests were conducted to characterize the device performance in air and in water. When implanted in the cochlea of an anesthetized guinea pig, the in vivo voltage response from the PIAT was measured in response to 80-95 dB sound pressure level 1-14 kHz sinusoidal acoustic excitation at the entrance of the guinea pig's ear canal. All sensed signals were above the noise floor and unaffected by crosstalk from the cochlear microphonic or external electrical interference. These results demonstrate that external acoustic stimulus can be sensed via the piezoelectric voltage response of the implanted MEMS transducer inside the living cochlea, providing key steps towards developing intracochlear acoustic sensors to replace external or subcutaneous microphones for auditory prosthetics.

A comparison of the growth performance, carcass traits, and behavior of guinea pigs reared in wire cages and floor pens for meat production.

To achieve efficient production of guinea pigs for meat, it is essential to determine the most suitable housing system. A total of 220 guinea pigs were maintained in either wire cages (n = 11, 10 animals per cage) or floor pens (n = 11, 10 animals per pen) containing a deep litter of woodchips, both housing systems having the same dimensions (2 × 1 × 0.4 m). Growth traits, food intake and feed conversion ratio were recorded weekly and expressed as the difference between the two groups. After 77 days, the animals were slaughtered, and carcass traits were evaluated. Growth performance and carcass trait parameters, as well as mortality and behavior trends, were not affected by the housing system type. Nonetheless, the use of wire cages is recommended for raising guinea pigs since water, urine and feces pass through the wire floor, resulting in cleaner animals.

Cortisol during adolescence organises personality traits and behavioural syndromes.

Despite the growing evidence for the importance of developmental experiences shaping consistent individual differences in behaviour and physiology, the role of endocrine factors underlying the development and maintenance of such differences across multiple traits, remains poorly understood. Here, we investigated how an experimental manipulation of circulating glucocorticoids during early adolescence affects behavioural and physiological variation and covariation later in life in the precocial cavy (Cavia aperea). Plasma cortisol concentrations were experimentally elevated by administering cortisol via food for 3 weeks. Struggle docility, escape latency, boldness, exploration and social behaviour were then tested three times after individuals attained sexual maturity. In addition, blood samples were taken repeatedly to monitor circulating cortisol concentrations. Exogenous cortisol affected mean trait expression of plasma cortisol levels, struggle docility and escape latency. Repeatability of cortisol and escape latency was increased and repeatability of struggle docility tended to be higher (approaching significance) in treated individuals. Increased repeatability was mainly caused by an increase of among-individual variance. Correlations among docility, escape latency and cortisol were stronger in treated animals compared to control animals. These results suggest that exposure to elevated levels of cortisol during adolescence can alter animal personality traits as well as behavioural syndromes. Social and risk-taking traits showed no correlation with cortisol levels and were unaffected by the experimental manipulation, indicating behavioural modularity. Taken together, our data highlight that cortisol can have organising effects during adolescence on the development of personality traits and behavioural syndromes, adding to the increasing evidence that not only early life but also adolescence is an important sensitive period for behavioural development.

Guinea pig for meat production: A systematic review of factors affecting the production, carcass and meat quality.

In developing countries, interest in guinea pig farming is growing exponentially because it provides a regular source of high quality animal protein for domestic consumption. Guinea pigs (Cavia porcellus) are prolific animals, grow and are capable of reproduction on a flexible diet, and are adaptable to a wide range of climates. This article mainly reviews findings on guinea pig meat production, including factors affecting raising guinea pigs, carcass and meat quality. We also present some studies that describe biological and pathologic effects on carcass component composition. During the last decades no standard procedure has been established for guinea pig carcass evaluation, which makes very difficult any comparison of results with other studies around the world. Herein we highlight a variety of factors that significantly affect carcass and meat quality. Some of these factors are production systems, environmental and genetic factors, management systems, the diet and health status, age, sex and reproductive management.