Effect of litter size

FIGURE 8.4. Effect of litter size on mean percentage preimplantation loss in 1035 control rat litters. Between 1970 and 1988, 1035 control rats were cesarean sectioned on Day 20 of gestation and the numbers of resorptions and implants were counted. Numbers within the bars indicate number of litters. 

FIGURE 8.6. Effect of litter size (live fetuses per litter) on incidence of supernumerary rib in 1379 control rat litters. Between 1978 and 1988, fetal skeletons from 1379 litters of control rats were stained with alizarin red and examined for supernumerary rib. 

Table 16.18 Effect of litter size on miik yieid in the sow ...

Berard, J., M. Kreuzer, and G. Bee, 2008. Effect of litter size and birth weight on growth, carcass and pork quality, and their relationship to post mortem proteolysis. J Anim Sci. 86 2357-2368. 

No teratogenesis observed in 7 generations at dietary level of 17.5 mg/kg positive effect on litter size and survival... 

In a dominant lethal test, treatment of male mice with a single oral dose of 5 mg/kg disulfoton had no effect on male fertility (Herbold 1980). In a three-generation reproductive study, exposure of male and female rats to disulfoton in the diet at 0.5 mg/kg/day resulted a "slight" reduction of litter sizes in... 

Administration of diazinon at 10, 20, or 100 mg/kg/day diazinon by oral gavage during gestation days 6-15 in CD-I rats had no significant effect on litter sizes or numbers of viable fetuses (Infurna et al. 

Two-generation studies were performed in which groups of 20 female Sherman rats were exposed by diet to Aroclor 1254 in doses of 0,0.06,0.32,1.5, or 7.6 mg/kg/day or Aroclor 1260 in doses of 0,0.39,1.5, or 7.4 mg/kg/day (Linder et al. 1974). Exposure to Aroclor 1254 caused significantly reduced litter sizes at 7.6 mg/kg/day in the Fla generation (14% smaller than controls) and 4.5 mg/kg/day in the Fib, F2a, and F2b generations (15-72% smaller than controls). No effects on litter size were found in either generation of rats fed 0.06 mg/kg/day of Aroclor 1254 or 0.39 mg/kg/day of Aroclor 1260. Insufficient information is available to determine whether the effect on litter size is due to reproductive or developmental toxicity because fertility and other reproductive end points were not evaluated in the study. 

Monoethanolamine showed reproductive toxicity when administered at a dose of 850 mg/kg/day, causing 16% mortality to pregnant animals (Environmental Health Research and Testing 1987). This study also indicated that monoethanolamine reduced the number of viable litters but had no effect on litter size, the birth weight, or percentage survival of the pups. 

Effects on reproduction [size of litters/broods evidence of teratogenicity (physical defects) in foetuses]. 

The progeny, mated within the experimental group, had a decreased number of pregnancies and reduced litter size at the 0.5 )u.g/kg while no effect was observed in 0.25 /xg/kg progeny. 

Other additional studies or pertinent information which lend support to this MRL Additional studies have reported developmental effects in rodents exposed to trichloroethylene. Following exposure of rats on gestation days 6-19, decreased litter size (Narotsky and Kavlock 1995), and increased micro- or anophthalmia (Narotsky and Kavlock 1995 Narotsky et al. 1995) were observed in the offspring at 1,125 mg/kg/day, but not at 844 mg/kg/day (Narotsky et al. 1995). 

No differences were noted in the litter sizes among those treated and the controls. No differences were noted in the number of stillborn pups or in pup weights. The study authors concluded that there was no evidence of adverse diisopropyl methylphosphonate-induced reproductive effects. However, as discussed in Section 2.2.2.1, there is some confusion regarding the actual doses to which the animals were exposed in the Hardisty et al. (1977) study. Therefore, results from this study are considered inappropriate for human health risk assessment. 

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