Limits to sustained energy intake. XVII. Lactation performance in MF1 mice is not programmed by fetal number during pregnancy
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SUMMARY Several studies have suggested that lactation performance may be programmed by the number of fetuses during pregnancy, whereas other studies indicate that processes during lactation are more important. As gestation litter size and litter size in lactation are usually strongly correlated, separating the roles of pregnancy and lactation in lactation performance is difficult. To break this link, we experimentally manipulated litter size of MF1 mice to five or 16 pups per litter by cross-fostering. Litter size and mass at birth were recorded on day 1 of lactation prior to litter size manipulation. Maternal body mass and food intake, litter size and litter mass were measured daily throughout. After weaning, the potential differential utilisation of body tissues of the mothers was investigated. Relationships between maternal mass and food intake, including asymptotic daily food intake at peak lactation, offspring traits and other maternal parameters suggested that the number of fetuses the females had carried during pregnancy had no effect on lactation performance. Litter mass increases depended only on maternal food intake, which was highly variable between individuals, but was independent of fetal litter size. The sizes of key organs and tissues like the liver and alimentary tract were not related to maximal food intake at peak lactation or to fetal litter size, but the masses of the pelage, mammary glands and retroperitoneal fat pad were. These data suggest that while growth of the mammary glands and associated structures may be initiated in gestation, and vary in relation to the number of placentas, the ultimate sizes and activities of the tissues depends primarily on factors during lactation.Keywords:
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Among the important aspects of climate change, exposure to high temperatures (heat waves) is rapidly emerging as an important issue, in particular for female mammals during lactation. High temperatures adversely impact ability to dissipate heat, which has negative effects on reproductive output. The cumulative effects on growth of F1 offspring after weaning and future reproductive performance of offspring remain uncertain. In this study, the F1 mice that weaned from mothers lactating at 21°C and 32.5°C were housed at 21°C from day 19 till 56 of age; during which food intake and body mass were measured. The F1 adult females that had been weaned at the two temperatures were bred and then both exposed to 32.5°C during lactation. Energy intake, milk output and litter size and mass were determined. The F1 adults weaned at 32.5°C consumed less food and had lower body mass than their counterparts weaned at 21°C. Several visceral organs or reproductive tissues were significantly lower in mass in F1 weaned at 32.5°C than at 21°C. The exposure to 32.5°C significantly decreased energy intake, milk output and litter mass in F1 adult females during lactation. The F1 adult females weaned at 32.5°C produced less milk and raised lighter pups than those previously weaned at 21°C. The data suggest that transient exposure to hot temperature during lactation has long-lasting impacts on the offspring, including stunted growth and decreases in future reproductive performance when adult. This indicates that the offspring of females previously experiencing hot temperatures have a significant fitness disadvantage.
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Abstract Sow and litter performance of 54 grade Large White sows was measured over four parities. At first mating the animals were allocated at random to three levels of apparent digestible energy intake in lactation and within each of these treatments to three post-weaning treatments. Post-weaning treatments were imposed for 4 days from the day of weaning and involved the feeding of 2.72 kg meal daily, or a period of feed and water withdrawal for 24 h followed by either 3. 63 or 2. 72 kg feed for 3 days. All treatment groups returned to an intake of 2.72 kg meal 5 days after weaning. The imposition of treatments for 4 consecutive days starting at weaning significantly influenced litter size at birth and 4 weeks of age in Parities 2 and 4. However, no differences were found in Parity 3. Sows not subjected to a 24-h period of feed and water deprivation farrowed the largest litters, and sows starved for 24 h and then offered 2.72 kg of meal daily had the smallest litters. The interval beween weaning and either first oestrus or successful mating was not affected by post-weaning or lactation treatments. Energy intake levels in lactation did not affect sow or litter performance, possibly due to the small range in apparent digestible energy intakes.
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Seventeen crossbred sows were used in a lactation trial to compare the effects of a 16-h photoperiod with an 8-h photoperiod from d 107 of gestation to weaning at 28 d postpartum. Crossbred sows were used to compare the effects of 16-h (n = 8) and 8-h (n = 9) photoperiods on litter and maternal performance traits. Females were moved into two identical farrowing rooms under either 16- or 8-h photoperiods on d 107 of pregnancy, litters were equalized across treatments at birth and the treatments terminated at weaning on d 28 postpartum. Traits evaluated included litter size at birth and weaning, 21-d pig and litter weights, milk yield and composition on d 15, litter survival rates, suckling frequency for a 24-h period on d 13 and percentage of sows returning to estrus and days to estrus after weaning. Pigs exposed to 16 h light nursed more often (P<.05) than pigs exposed to 8 h light over a 24-h period. This advantage was greatest during the 4-h periods of 1200 to 2000, 0000 to 0400 and 0800 to 1200 h. This difference is perhaps an explanation of why litters exposed to 16 h light weaned more (P<.05) pigs/litter with heavier (P<.01) 21-d litter weights. Nonsignificant advantages were also seen in milk yield and litter survival percentage. In addition, sows exposed to 16 h light had higher (P<.05) total solids content of their milk.
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Resource allocation patterns, as quantified by residual food intake (RFI), and the consequences for offspring development were investigated during lactation in 96 females of a mouse line selected for 104 generations for high litter size at birth (S-line) and in 87 females of a non-selected control line (C-line). Litters of 45 C-line dams (Cs) and 48 S-line dams (Ss) were standardised (s) at birth; other dams (ns) supported total number of pups born (Cns and Sns, respectively). RFI during lactation was significantly lower in Sns-dams than in C-line dams and Sns-dams. After weaning Sns-dams seemed to be able to restore the negative resource situation. Sns-pups were about 25% less mature than Cns-pups at all times. Maturity was similar for Cs- and Ss-pups from 2 d in lactation on, and about 18% and 53% higher than Cns- and Sns-pups. The pre-weaning mortality rate was significantly higher in Sns-litters (35.6 ± 2.76) than in Cns-litters (4.95 ± 2.23). The results suggest that S-line dams allocated considerably more resources to maintenance of offspring than C-line dams. This was insufficient to provide the offspring with an adequate amount of resources, resulting in reduced pup development and increased pre-weaning mortality rates.
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High fat feeding reportedly enhances hypothalamus-pituitary-adrenal (HPA) responses to stress in adult rats. The present study tested whether elevated fat intake during suckling could have short and/or long lasting consequences on HPA regulation in the offspring. Mothers were fed either a control (C; 5% fat) or high fat (HF; 20% fat) diet during the last week of gestation and throughout lactation. After weaning (day 21), pups from C and HF mothers were fed a chow diet. Offspring from both C- and HF-fed mothers were tested for ACTH and corticosterone responses to stress on postnatal days 10 and 35. We found that HF feeding produced higher lipid levels in the milk of HF compared with C lactating rat dams and that offspring of these mothers had significantly increased retroperitoneal fat pad weight and relative adipose mass on day 21 as well as elevated plasma leptin levels on days 10 and 21 of age. After weaning, pups from the HF mothers had lower plasma leptin levels than those from C mothers. Maternal dietary fat affected HPA responsiveness in the offspring in an age-related manner. Neonatal pups (day 10) from the HF mothers exhibited a reduction in the ACTH and corticosterone responses to ether stress. However, in 35-day-old offspring from HF-fed dams, stress-induced ACTH secretion was increased compared with that in pups from the C-fed mothers. These results demonstrate that maternal diet and increased fat intake through the milk are important regulators of HPA responsiveness in neonates and prepubertal rats. During neonatal life, the blunted stress responsiveness seen with elevated fat intake and the resulting high leptin levels might protect the pups from excessive HPA activation. After removal of the maternal dietary influence and reduced leptin levels, enhanced ACTH stress responses are observed as in adult rats fed a HF diet. Because of the inverse relationship between plasma levels of leptin and HPA responses in pups, the possibility exists that the effects of the HF diet on stress responsiveness are mediated by changes in leptin exposure during development.
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Oral gavage is a popular route of drug administration during preclinical testing. Despite the growing body of information regarding the effects of oral gavage and the stress associated with this technique, the consequences of such exposure during pregnancy or lactation have rarely been investigated. Therefore, we sought to determine the consequences of oral gavage exposure during pregnancy and lactation on the neurodevelopment and behavior of rat offspring. Pregnant Sprague-Dawley dams underwent either no treatment or oral gavage of distilled water once daily from gestational day 7 until postnatal day 21. Oral gavage treatment had no significant effect on maternal parameters, including bodyweight gain, duration of gestation, litter size, and incidence of neonatal death. Compared with their counterparts from untreated dams, male and female progeny of gavaged dams had longer body lengths on PND 7 and 14 but reduced forelimb grip performance on PND 14 and 17. Therefore, the use of oral gavage during pregnancy and lactation in rats can have opposite effects on the somatic and behavioral development of the offspring. These factors should be considered when using oral gavage as a route of administration during pregnancy. In addition, the inclusion of no-treatment controls is important because they may reveal various restraint-associated effects.
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Objective To determine factors associated with weaning-to-mating interval among sows on commercial farms that wean pigs early. Design Cohort study. Animals 11,861 farrowing sows. Procedure Production, farrowing, and feed intake records were reviewed for sows on 16 farms for which mean duration of lactation was between 14.9 and 18.9 days. Results Among sows with high feed intake during lactation (≥ 5.6 kg/d [12.3 lb/d]), lactation duration was not associated with weaning-to-mating interval, but among sows with low feed intake during lactation (< 5.6 kg/d), weaning-to-mating interval increased as lactation duration decreased. Furthermore, among sows with the lowest feed intake during lactation (< 4.2 kg/d [9.2 lb/d]), those that had heavier litter weights at weaning (> 54 kg [119 lb]) had a longer weaning-to-mating interval than did those that had lighter litter weights at weaning. Sows with low feed intake and high litter weight at weaning accounted for 5 to 20% of sows on each farm. In general, weaning-to-mating interval increased as parity decreased, but the change in weaning-to-mating interval associated with a particular change in lactation duration varied with parity. Clinical Implications When feed intake during lactation is maximized (≥ 5.6 kg/d), lactation duration is not significantly associated with weaning-to-mating interval. Producers should consider fostering or partially weaning litters when sows with high litter weights are not consuming sufficient feed. ( J Am Vet Med Assoc 1997;211:894–898)
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High fat feeding reportedly enhances hypothalamus-pituitary-adrenal (HPA) responses to stress in adult rats. The present study tested whether elevated fat intake during suckling could have short and/or long lasting consequences on HPA regulation in the offspring. Mothers were fed either a control (C; 5% fat) or high fat (HF; 20% fat) diet during the last week of gestation and throughout lactation. After weaning (day 21), pups from C and HF mothers were fed a chow diet. Offspring from both C- and HF-fed mothers were tested for ACTH and corticosterone responses to stress on postnatal days 10 and 35. We found that HF feeding produced higher lipid levels in the milk of HF compared with C lactating rat dams and that offspring of these mothers had significantly increased retroperitoneal fat pad weight and relative adipose mass on day 21 as well as elevated plasma leptin levels on days 10 and 21 of age. After weaning, pups from the HF mothers had lower plasma leptin levels than those from C mothers. Maternal dietary fat affected HPA responsiveness in the offspring in an age-related manner. Neonatal pups (day 10) from the HF mothers exhibited a reduction in the ACTH and corticosterone responses to ether stress. However, in 35-day-old offspring from HF-fed dams, stress-induced ACTH secretion was increased compared with that in pups from the C-fed mothers. These results demonstrate that maternal diet and increased fat intake through the milk are important regulators of HPA responsiveness in neonates and prepubertal rats. During neonatal life, the blunted stress responsiveness seen with elevated fat intake and the resulting high leptin levels might protect the pups from excessive HPA activation. After removal of the maternal dietary influence and reduced leptin levels, enhanced ACTH stress responses are observed as in adult rats fed a HF diet. Because of the inverse relationship between plasma levels of leptin and HPA responses in pups, the possibility exists that the effects of the HF diet on stress responsiveness are mediated by changes in leptin exposure during development.
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