Effect of age and parity on litter size in pigs

Litter size increased (P less than 0.01) as the age of the dam at farrowing increased. However, previous reproductive experience (parity) had no direct effect on litter size of dams of the same age.     

Effects of age and parity on litter size and offspring sex ratio in golden hamsters (Mesocricetus auratus)

Golden hamsters that were mated repeatedly from 55 days of age produced 6-12 litters. Litter size at birth rose between the 1st and 2nd litters, peaked on the 3rd, and declined steadily after the 5th litter. Offspring sex ratio (% male) at birth followed a similar pattern: increasing between the 1st and 2nd litters, remaining high through the 3rd, and becoming increasingly female-biased thereafter. Weaning success decreased sharply after the 6th litter and most dams failed to raise any young to weaning after the 9th litter. These sequential effects on litter size, offspring sex ratio and weaning success were also observed in females mated once at different ages, but they occurred considerably later in life, i.e. increasing parity hastened the effects of advanced age. These age- and parity-related changes in litter composition are consistent with the Trivers-Willard hypothesis that physiologically-stressed females would skew offspring sex ratios to favour daughters. However, since the observed changes in sex ratio were probably due to differential prenatal mortality, their adaptive significance is unclear.     

Effects of litter size on sympathetic activity in young adult rats

Rearing animals in small litters induces a permanent increase in body weight and body fat. To determine whether changes in sympathoadrenal activity contribute to this effect, litter size was adjusted the day after birth and maintained until weaning at 21 days. Sympathetic nervous system (SNS) activity was measured in adult animals using [(3)H]norepinephrine ([(3)H]NE) turnover in peripheral tissues. Although litter size was without effect on [(3)H]NE turnover in chow-fed animals, acceleration of [(3)H]NE turnover by dietary sucrose was completely abolished in heart and attenuated in interscapular brown adipose tissue and kidney of rats reared in small litters. Body and epididymal fat-pad weights were heavier in rats reared in small litters; however, weight gain in response to dietary enrichment with sucrose did not differ as a function of litter size. Thus litter size alters dietary activation of the SNS, and this effect presumably reflects changes in central nervous system regulation.     

An investigation of playful behaviour in Rattus norvegicus and Mus musculus (Mammalia)

The playful behaviour of laboratory rats ( Rattus norvegicus ) was investigated in litters of five individuals with the mother present; parallel observations were made on mice ( Mus musculus ). Seven mixed litters containing four young rats and a young mouse fostered at birth were also observed.
Solitary play was recorded in both species and took a similar form but social play was only observed in rats. In rats, solitary play frequently preceeded social play.
The behavioural elements involved in the social play of Rattus norvegicus were described, and the majority of these were the playful equivalent of adult agonistic behaviour elements. These social play elements were found to be organized into definite sequences which differed from those of adult aggression. Each behavioural element was found to act as a social releaser.
Young mice did not respond playfully to social play from a rat litter mate; mice were less attractive to rats as playmates in comparison with fellow rats.     

The influence of the sex of litter-mates on subsequent maternal behaviour in Rattus norvegicus.

Female rats reared in unisexual (U) or bisexual (B) cross-fostered litters were mated at 75 days of age and their maternal behaviour compared by periodic observation over 20 days following birth of their litters. In two separate experiments, U-females showed a lower incidence of pregnancy and, at birth, of litters with ten or more pups than B-females (P less than 0-05). Litters culled to ten animals on the day after birth were significantly heavier in B- than in U-females, although this difference was not evident at weaning as litters reared by U-females showed a relatively greater (P less than 0-01) increase in weight during the investigation than the corresponding litters reared by B-females. Using a scoring method, no difference was evident in the opportunities that U- and B-females offered for their pups to suck, and, when not nursing pups in the nest, both groups of females engaged equally in activities such as grooming, sleeping, eating, and rearing on their hind legs. Throughout the 20-day observation period, B-females maintained significantly more elaborate nests (as scored on an arbitrary scale) than U-females. This difference was evident in females rearing litters of both five and ten animals, and was observed in two separate experiments. In addition, whereas only 15 per cent of U-females were observed nest-building, over 60 per cent of B-females were noted to be engaged in this activity on one or more occasions (P less than 0-001). It is suggested that, in the light of previous findings, these results may reflect differences in oestrogen and/or progesterone metabolism in unisexually-reared and bisexually-reared female rats.     

The Effects of Environmental Control on Cognition in Rats (Rattus norvegicus)

The aim of this study was to allow nonhuman animals to control their environment using operant conditioning procedures and to assess the effect of control on cognitive tasks. The study tested 4 predictions: (a) rats (Rattus norvegicus) will control a light stimulus; (b) animals will exhibit preferences for particular stimulus strengths; (c) animals who exert control over environmental stimuli will show improved performance on cognitive tasks compared with animals who lack control; and (d) at the end of the operant phase, experimental subjects will have lower corticosterone levels than animals who lack control. Experimental subjects did show control over a light stimulus and performed significantly better over time in a discrimination task compared with subjects who could not control their environment. There was no difference in corticosterone levels between control and experimental subjects. The results will both contribute to our understanding of how control of environmental stimuli affects the welfare of animals in captive environments and aid in designing experimental conditions that will increase validity and reliability in research.     

云南省34个县市黄胸鼠和褐家鼠体表寄生蚤调查

目的调查云南省黄胸鼠Rattus flavipectus和褐家鼠R.norvegicus体表寄生蚤的感染情况,为云南省鼠疫防控提供科学依据。方法 2012年7月—2013年11月,在云南省34个县市随机选取采样点,笼捕法采集黄胸鼠和褐家鼠,收集并鉴定体表寄生蚤,统计宿主和蚤类物种组成、染蚤率、蚤指数,并根据蚤种组成进行分层聚类。结果采集鼠类842只,其中黄胸鼠714只、褐家鼠128只;共检获体表寄生蚤3227匹,涵盖10个已知蚤种,其中,印鼠客蚤Xenopsylla cheopis和缓慢细蚤Leptopsylla segnis为优势物种。黄胸鼠和褐家鼠的染蚤率分别为48.88%和53.91%,2种鼠的总体蚤指数为3.83匹/只,其中有16个县市的印鼠客蚤指数>1。聚类分析将所有样点聚成3大支系:A支系印鼠客蚤占优势,主要分布于云南省南部地区;B支系优势种不明显或具有其他蚤种,分布于云南省中部地区;C支系缓慢细蚤占优势,分布于云南省北部地区。结论印鼠客蚤和缓慢细蚤是云南省主要蚤种,在接近半数地区印鼠客蚤指数>1,防疫形势非常严峻。云南省黄胸鼠和褐家鼠体表蚤区系组成具有一定的地带性,其中南部地区为印鼠客蚤优势分布区,可视为媒介监测和防控的重点区域。     

Selection response for litter size at birth and litter weight at weaning in the first parity in mice

Summary Five 60-pair lines of mice were selected for seven generations for the following criteria: number born alive (LSO), random selection of litters (LC), number born alive divided by the weight of the dam at 9 weeks (LSO/DWT), total litter weight weaned divided by the weight of the dam at 9 weeks (LWT/DWT), and weight of litter weaned (LWT). All traits were measured in the first parity only and litters were not standardized. Realized heritabilities for LSO, LWT, LSO/DWT, and LWT/ DWT were 0.10± 0.06, 0.11±0.07, 0.22 ± 0.04, and 0.22 ± 0.08, respectively. Selection response for the two ratio lines was due to correlated responses in the respective numerators, LSO and LWT, as DWT did not decrease. In terms of improving LWT, selection for LWT/ DWT was three times as effective as selection for LSO/ DWT.     

Warfarin-resistance genotype determination in the Norway rat, Rattus norvegicus

The 2-stage determination is based on changes in blood coaggulation activity brought about both by the administration of warfarin in conjunction with vitamin K1 epoxide and by feeding a vitamin K-free diet for 4 days. When it was applied to laboratory-bred rats of known warfarin-resistance genotype, 35/35 homozygous susceptible, 44/44 homozygous resistant and 131/133 heterozygous rats were correctly classified. This method was equally effective in identifying the genotype of wild rats carrying the warfarin-resistance gene, Rw2. The procedure is rapid and accurate.     

Pen size and parity effects on maternal behaviour of Small-Tail Han sheep

The aim of this experiment was to study the effects of pen size and parity on maternal behaviour of twin-bearing Small-Tail Han ewes. A total of 24 ewes were allocated to a 2×2 design (six per pen), with parity (primiparous or multiparous) and pen size (large: 6.0×3.0 m; small: 6.0×1.5 m) as main effects at Linyi University, Shandong Province, China. Behaviour was observed from after parturition until weaning. All ewes were observed for 6 h every 5 days from 0700 to1000 h and from 1400 to 1700 h. Continuous focal animal sampling was used to quantify the duration of maternal behaviours: sucking, grooming and following as well as the frequency of udder accepting, udder refusing and low-pitched bleating. Oestradiol and cortisol concentrations in the faeces (collected in the morning every 5 days) were detected using EIA kits. All lambs were weighed 24 h after parturition and again at weaning at 35 days of age. The small pen size significantly reduced following (P<0.005), grooming (P<0.001) and suckling durations (P<0.05), as well as the frequency of udder refusals (P<0.001). However, there was a significant interaction with ewe parity, with decreased grooming and suckling in the small pen largely seen in the multiparous ewes (P<0.001). Independent of pen size, multiparous ewes accepted more sucking attempts by their lambs (P<0.05) and made more low-pitched bleats than primiparous ewes (P<0.001). Multiparous ewes had higher faecal oestradiol concentrations than primiparous ewes (P<0.001), and ewes in small pens had higher faecal cortisol levels compared with ewes in larger pens (P<0.001). As lambs increased in age, the duration of maternal grooming, following and suckling as well as frequency of udder acceptance and low-pitched bleating all declined, and the frequency of udder refusing increased (P<0.001 for all). Ewe parity, but not pen size, affected lamb weight gain during the period of observation (P<0.001). This is the first study to show that pen size, interacting with parity, can affect the expression of maternal behaviour in sheep during lactation. The study is also the first to report on the maternal behaviour of Chinese native sheep breeds (Small-Tail Han sheep), with implications for the production of sheep in China.     

The influence of the food size,distance and food site on food carrying behavior in rats (Rattus norvegicus)

The behavior to foods in rats (Rattus norvegicus) was investigated in a seminatural enclosure and in a straight alley in the laboratory. In both situations, the size of food (0.045-, 1-, and 3-g pellets were used in the enclosure and 0.045-, 0.2-, 1-, and 3-g pellets in the alley) and distance between food sites and nest site (1.8, 3.6, 5.4, and 7.2 m in the enclosure and 2, 4, and 6 m in the alley) were varied. In both situations, when food was presented in only 1 place, the food carrying behavior increased as the size of food increased from 0.045 to 1-g. One and three g pellets were always carried, regardless of the distance to nest. On the other hand, when multiple food sites were presented in the alley, rats were more likely to carry small pellet from the further food site, whereas large pellet was always carried and were not influenced by the distance. The behavior to foods in the enclosure, however, was not influenced in either food site condition. This might be due to the difference in familiarity to the environment and anxiety from perceived predation risk.     

Effect of birth litter size, birth parity number, growth rate, backfat thickness and age at first mating of gilts on their reproductive performance as sows

The present study was performed to evaluate retrospectively the influence of birth litter size, birth parity number, performance test parameters (growth rate from birth to 100kg body weight and backfat thickness at 100kg body weight) and age at first mating (AFM) of gilts on their reproductive performance as sows. Traits analysed included remating rate in gilts (RRG), litter size, weaning-to-first-service interval (WSI), remating rate in sows and farrowing rate (FR). Data were collected from 11 Swedish Landrace (L) and 8 Swedish Yorkshire (Y) nucleus herds and included 20712 farrowing records from sow parities 1-5. Sows that farrowed for the first time during 1993-1997, having complete records of performance test and AFM, were followed up to investigate their subsequent reproductive performance until their last farrowing in 1999. Analysis of variance and multiple regression were applied to continuous data. Logistic regression was applied to categorical data. The analyses were based on the same animals and the records were split into six groups of females, i.e. gilts, primiparous sows, and sows in parities 2-5, respectively. Each additional piglet in the litter in which the gilt was born was associated with an increase of her own litter size of between 0.07 and 0.1 piglets per litter (P<0.001). Gilts born from sow parity 1 had a longer WSI as primiparous sows compared with gilts born from sow parity 4 (0.3 days; P<0.05) or parity 5 (0.4 days; P<0.01). Gilts with a higher growth rate of up to 100kg body weight had a larger litter size (all parities 1-5; P<0.05), shorter WSI (all parities 1-5; P<0.05) and higher FR (parities 2 and 5; P<0.05) than gilts with a lower growth rate. Gilts with a high backfat thickness at 100kg body weight had a shorter WSI as primiparous sows (P<0.001) compared with low backfat gilts, and 0.1 piglets per litter more as second parity sows (P<0.01). A 10 day increase in AFM resulted in an increase in litter size of about 0.1 piglet for primiparous sows (P<0.001) and a decrease (P<0.05) for sow parities 4 and 5.