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D Meikle and M Westberg

Food deprivation after weaning often has greater effects on the reproductive success of females than of males. However, if animals are deprived prenatally (that is, through food deprivation of the mother during gestation), the reproductive success of males may be more adversely affected than that of females because of a disruption in the organizational effects of testosterone in neonatal male mice. The hypotheses that daughters of female mice deprived of food during gestation would have lower reproductive success than control daughters, but that the impact of maternal food deprivation would be lower for daughters than it would be for sons, was tested. There was no difference in the proportion of daughters of food-deprived and control mothers that produced one or two litters. However, the mean number of pups weaned in the second litters by daughters of control females (5.9 +/- 0.57 SEM) was greater than the number of pups weaned by daughters of food-deprived females (4.5 +/- 0.65 SEM). There were no differences in the mean birth or weaning body weights of offspring. Therefore, maternal food deprivation in mice may have a small but significant effect on the reproductive success of daughters. However, studies of sons born to females that were subjected to the same food deprivation protocol indicate that maternal food deprivation may have a much greater effect on the reproduction of sons than on that of daughters.

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D. B. Meikle and L. C. Drickamer

Summary. Female house mice deprived of food intermittently for 1 week before mating gave birth to fewer male young, but litters of females deprived of food for 2 weeks did not differ from control litters. Since mean weights of females did not differ between the two treatments, our results suggest that females were initially stressed by food deprivation, but recovered in the second week.

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D. B. Meikle and M. W. Thornton

Pregnant female house mice maintained on a consistent low-food diet give birth to a lower proportion of males than do control females fed ad libitum. Because house mice may experience daily fluctuations in food availability, we tested whether intermittent feeding during gestation influences the sex ratio of the offspring. In addition, we tested whether intermittent feeding has asymmetrical effects on the masses of adult male and female offspring. Females deprived of food every other day one week before mating and those deprived every third day during gestation produced a lower proportion of males than did control (fed ad libitum) females. Males born to females that were deprived of food during gestation had the same body mass at birth as males born to control females, but as adults their mass was lower than that of control males. There were no differences in the birth or adult body masses of female offspring. Because males of low body mass may have relatively low lifetime reproduction, our results support the Trivers–Willard model of sex ratio variation.

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A Meikle, M Kulcsar, Y Chilliard, H Febel, C Delavaud, D Cavestany and P Chilibroste

The effect of parity (multiparous vs primiparous) and body condition score (BCS; <3.0 or ≥3.0, lean vs fat) at parturition on metabolic and endocrine profiles from 1 month before to 2 months after parturition were studied in 42 Holstein cows grazing on improved pastures. BCS and milk production were determined every 2 weeks. Non-esterified fatty acids (NEFA), β-hydroxy-butyrate (BHB), insulin, IGF-I, leptin, thyroxine (T4) and 3,3′,5-tri-iodothyroinine (T3) were determined in plasma every 10 days. Progesterone was determined three times per week after parturition. Primiparous cows had a lower BCS during the early postpartum period and produced less milk than multiparous animals. Primiparous cows had higher NEFA concentrations and they presented more samples with BHB concentrations of >1 mmol/l than multiparous cows. Multiparous cows had higher T3, T4 and IGF-I concentrations, while fat cows had higher leptin and IGF-I concentrations. All hormone concentrations were diminished in the first week postpartum. Primiparous cows and fat cows presented a steeper decay of IGF-I and leptin around parturition than multiparous cows and lean cows. While thyroid hormones and IGF-I showed increasing concentrations from approximately day 30, leptin concentrations remained low until the end of the experimental period. The initiation of ovarian cyclicity was delayed in primiparous cows and especially in primiparous lean cows, consistent with longer intervals from parturition to first service and to conception. The endocrine signals most likely to inform the reproductive axis regarding a negative energy balance were IGF-I and leptin.