ABSTRACT. The factors related to cannibalistic behavior of dams in a Wistar rat colony are identified and analyzed. The maternal genetic effects were tested as a random effect by the method of generalized linear models. The season at parturition, the dam´s age at parturition and the density of the room at parturition were tested as fixed effects, whereas the litter size at birth was tested as a co-variable. The genetic effect of the dam was significant for the number of cannibalized pups. Although the season at parturition, the dam´s age and room density on the day of parturition were not individually significant (p > 0.05), most of the interactions between the variation sources were significant (p < 0.05). Cannibalism occurred mostly in dams aged over 241 days, with parturition during spring. So that occurrences of cannibalism could be avoided, dams with the smallest number of cannibalized pups should be selected, coupled to dams younger than 241 days, breeding during spring. The above strategies may reduce the number of couples in the vivarium and increase their production efficiency.Keywords: laboratory animals, maternal behavior, infanticide, rodents.Efeito do ambiente e da matriz sobre o canibalismo em filhotes de ratos Wistar RESUMO. O objetivo deste estudo foi identificar os fatores relacionados ao comportamento de canibalismo das fêmeas em uma colônia de ratos Wistar. Os efeitos genéticos maternos foram testados como efeito aleatório usando o método dos modelos lineares generalizados. A estação do parto, a idade da fêmea ao parto e a densidade da sala ao parto foram testados como efeitos fixos e o tamanho da ninhada ao nascimento foi testado como covariável. O efeito genético da matriz foi significativo para o número de filhotes canibalizados. A estação do ano ao parto, a idade da matriz e a densidade da sala no dia do parto quando testados separadamente não foram significativos (p > 0,05), porém, a maioria das interações entre estas fontes de variação foram significativas (p < 0,05). O canibalismo ocorreu em maior frequência em fêmeas com idade superior a 241 dias durante a primavera. Para evitar o canibalismo na população estudada, recomenda-se a seleção de fêmeas com menor número de filhotes canibalizados e a maior utilização de matrizes com idade inferior a 241 dias durante a primavera. Estas estratégias podem promover a redução do número de casais necessários no biotério e aumentar sua eficiência reprodutiva.Palavras-chave: animais de laboratório, comportamento materno, infanticídio, roedores.
The rodents Proechimys guyannensis have led a great interest because they are considered as hosts to several pathogens causing zoological diseases. Therefore, it is important to know their biological and physiological parameters. The age at first cubs delivery and the average of birth interval per female were evaluated. The estimated age at puberty was 83 days. The number of pups born per delivery did not differ significantly when associated with the female mating age. However, an increase in the average mortality rate correlated with the increase in delivery number per female was detected. There is no statistical difference neither in the litter size in different seasons of the year, nor in the body weight between sexes for all ages. Differences were found in the daily water consumption and in the feed intake in animals with approximately 100 days of age, perhaps owing to the increased need for energy intake due to sexual activity or even because they had not reached adult weight yet. The parameters assessed in the present study are of relevance for maintaining this species in captivity as a laboratory animal.
The aim of this study was to estimate genetic parameters and genetic trends for reproductive traits in Wistar rats. A total of 1,167 data records from 283 females over six generations of monogamous mating pairs was used. Heritability and genetic correlation were estimated through Bayesian inference and genetic trends were calculated by linear regression of breeding values over generations. Heritability estimates for litter size at birth (LS), calving interval (CI), pup mortality (PM) and maternal cannibalism (CAN) presented low magnitude, ranging from 0.01 to 0.13. CAN presented high and positive genetic correlation with LS and PM (0.77 and 0.78, respectively). On the other hand, all the other estimated genetic correlations were not significant. Genetic trend was positive for LS (+0.0900 pups per generation), and negative for PM and CAN (-1.0085 and -0.5217 pups per generation, respectively). For CI the genetic trend was not significant. It is recommended to increase selection intensity on dams in this Wistar rat population in order to accelerate the genetic progress.
Ratos Wistar são uns dos modelos mais utilizados em pesquisas. Para o bem estar-animal e obter maior produtividade é fundamental que instituições garantam padrões macroambientais preconizados pelo Conselho Nacional de Controle de Experimentação Animal (CONCEA). O objetivo deste trabalho foi avaliar o efeito de macroambientes em parâmetros reprodutivos de ratos. Foram analisados retrospectivamente dados de animais mantidos em instalações não-ideias (A) e ideais (B). Houve diferença na idade ao primeiro parto (p0,05), sendo que as fêmeas do grupo B foram mais precoces e também apresentaram maior número de filhotes por ninhada (p0,05). Não houve diferença (p0,05) quanto ao intervalo entre partos. Foi demonstrado que as condições físicas do biotério afetam diretamente o desempenho reprodutivo.
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