Correlated responses in maternal performance following divergent selection for heat loss in mice1

Abstract

Divergent selection in mice was applied in 3 independent replicates for high (maintenance high; MH) and low (maintenance low; ML) heat loss for 16 generations. An unselected control (maintenance control; MC) was also maintained in all replicates. Selection ceased for 26 generations; heat-loss measurement and selection resumed at generation 42. Lactation performance, dam weight, dam feed intake, and efficiency of production of pup weight were recorded or calculated for MH and ML dams in all 3 replicates at generation 46 or 47 with the objective of determining whether selection for heat loss has created correlated responses in maternal performance. One-half of the dams reared their own litters, and one-half reared cross-fostered (across lines) litters. Between 10 and 12 litters were used from each replicate-line-rearing class. Litter size was recorded, and litters were standardized to 8 pups within 24 h of birth. For cross fostering, MH litters were matched to ML litters born within 24 h of each other, and MH-ML litter pairs were cross-fostered at 3 d of age. A weigh-suckle-weigh protocol was used to obtain milk production estimates over a 2-h suckling period at 6, 9, 12, and 15 d. Dam (plus litter) feed intake

Limits to sustained energy intake. X. Effects of fur removal on reproductive performance in laboratory mice

“…As indicated by a weigh-suckle-weigh method, mice selected for high heat loss produced on average 20.6% (1.70·g/1.41·g) more milk over a 2·h collection period than the low heat loss mice (McDonald and Nielsen, 2006). Furthermore, the litters weaned by mice selected for high heat loss were on average 10.1·g heavier than the litters produced by the low heat loss line.…”

Limits to sustained energy intake. XIII. Recent progress and future perspectives

“…These data indicate that a key factor influencing maternal suckling duration is the risk of the mother overheating during the suckling bout (Leon et al, 1978;Leon et al, 1983;Bates et al, 1985;Leon et al, 1985;Adels and Leon, 1986;Newkirk et al, 1998). Further support for the HDL theory comes from comparisons of the reproductive performance of mice selectively bred to enhance their capacity to dissipate heat (Nielsen et al, 1997a;Nielsen et al, 1997b;Kgwatalala et al, 2004;McDonald and Nielsen, 2006). These mice have elevated milk production and raise heavier litters (McDonald and Nielsen, 2007).…”

Effects of a Maternal Low Protein Isocaloric Diet on Milk Leptin and Progeny Serum Leptin Concentration and Appetitive Behavior in the First 21 Days of Neonatal Life in the Rat

“…Maternal and offspring suckling factors are both likely to be involved in the increased milk production in a setting of increased pup milk consumption. There are data in the literature that indicate that pup consumption affects milk production as well as data showing that milk production has an influence on pup consumption (19,20). One way to determine the relative influences of these two possibilities in future studies would be to reduce the number of pups suckling the dam.…”