Increased genetic selection and capacity for milk production in dairy cows has been associated with a decline in fertility. Following parturition, nutritional requirements increase rapidly with milk production and the resulting negative energy balance (NEBAL) extends for 8–10 weeks of early lactation. NEBAL delays the timing of first ovulation through attenuation of LH pulse frequency and low l...

BACKGROUND Adolescent mothers may be at increased risk of irreversible bone loss during pregnancy and lactation, particularly when calcium intake is low. OBJECTIVE Longitudinal changes in bone mass from lactation to postweaning were evaluated in 10 adolescent mothers aged 15-18 y who habitually consumed <500 mg Ca/d. DESIGN Total-body bone mineral content (TBBMC), total-body bone mineral de...

Male care has energetic and opportunity costs, and is more likely to evolve when males gain greater certainty of paternity or when future mating opportunities are scarce. However, little is known about the substantial benefits that males may provide to females and offspring. Using phylogenetic comparative methods and a sample of over 500 mammalian species, we show that mammals in which males ca...

The effects of reproduction and maternal investment (i.e., milk transfer) on trace element levels remain poorly understood in marine mammals. We examined the blood dynamics of mercury (Hg) and selenium (Se) during lactation in the northern elephant seal (Mirounga angustirostris), a top predator from the North Pacific Ocean. Total Hg and Se levels were measured in whole blood and milk of 10 moth...

We investigated the effect of the amount of body condition loss in the dry period and early lactation in 42 high-yielding Holstein-Friesian cows on milk yield and the share of fatty acids in milk fat. Energy reserves were estimated based on the body condition scoring (BCS) and backfat thickness (BFT). Milk yield and milk composition were determined over 305-d lactation. From d 6 to 60 of lactat...