Showing papers on "Lactation published in 1999"
TL;DR: It is concluded that the first test day milk yield and the fat to protein ratio were more reliable indicators of disease, fertility, and milk yield than was body condition score or loss of body condition Score.
404 citations
TL;DR: Mastitis and breast milk HIV-1 load may increase the risk of vertical transmission of HIV- 1 through breast-feeding.
Abstract: Human immunodeficiency virus (HIV) type 1 load in breast milk and mastitis were examined as risk factors for vertical transmission of HIV-1. Six weeks after delivery, HIV-1 load and sodium (an indicator of mastitis) were measured in breast milk from 334 HIV-1-infected women in Malawi. Median breast milk HIV-1 load was 700 copies/mL among women with HIV-1-infected infants versus undetectable (<200 copies/mL) among those with uninfected infants, respectively (P<. 0001). Elevated breast milk sodium levels consistent with mastitis occurred in 16.4% of HIV-1-infected women and were associated with increased vertical transmission of HIV-1 (P<.0001). Median breast milk HIV-1 load was 920 copies/mL among women with versus undetectable among those without elevated breast milk sodium levels, respectively (P<.0001). Mastitis and breast milk HIV-1 load may increase the risk of vertical transmission of HIV-1 through breast-feeding.
394 citations
TL;DR: It is concluded that the actions of intracerebral oxytocin include independent effects on the responses of the hypothalamo-pituitary-adrenal axis and oxytoc in systems to stressors and the anxiety-related behaviour which are modulated by the reproductive state of the animals.
392 citations
TL;DR: In this article, a commercial source of conjugated linoleic acids (CLA) was infused abomasally to by-pass rumen fermentation to determine the effect of CLA supplementation on milk of dairy cows.
Abstract: Conjugated linoleic acids (CLA) have positive health effects in experimental models. Our objective was to determine the effect of CLA supplementation on milk of dairy cows. A commercial source of CLA was infused abomasally to by-pass rumen fermentation. The supplement contained 61.2% CLA; the major CLA isomers were cis/trans 8,10, cis/trans 9,11, cis/trans 10,12 and cis/trans 11,13. Four Holstein cows were used in a 4 x 4 Latin square design. Treatments were 5-d infusions of 0, 50, 100 and 150 g/d of CLA supplement. Infusion increased milk fat content of CLA from 6.8 mg/g fat (zero dose) to 63.6 mg/g fat (highest dose). All of the major CLA isomers in the supplement were transferred to milk fat in a dose-dependent manner. Apparent efficiency of transfer to milk fat was 22.5, 22.5, 10.2 and 26.3% for cis/trans 8,10, cis/trans 9,11, cis/trans 10,12 and cis/trans 11,13, respectively. CLA infusion had no effect on milk protein and little effect on milk yield (21.5, 20.4, 20.9 and 18.3 kg/d for 0, 50, 100 and 150 g/d CLA supplement, respectively). However, CLA infusion dramatically reduced milk fat. On average, the content and yield of milk fat were reduced by 52 and 55%, respectively. The role of specific CLA isomers and mechanism(s) for the reduction in milk fat have not been established, although the pattern of milk fatty acids demonstrated effects were most pronounced on de novo fatty acid synthesis and the desaturation process. Overall, dietary supplemention of CLA increased milk fat content of CLA, altered milk fatty acid composition and markedly reduced the content and yield of milk fat.
380 citations
TL;DR: Women who are at risk for delayed onset of lactation need additional breast-feeding support during the first week postpartum, and frequent nursing should be recommended, as delayed onsetof lactation was associated with the lack of infant suckling.
Abstract: Objective To identify infant feeding, socioeconomic, demographic, and delivery-related factors that affect women's self-reported timing of the onset of lactation. Design Longitudinal survey of women from day 1 postpartum until self-reported onset of lactation. Subjects were interviewed in person on day 1 postpartum, then surveyed daily by telephone regarding infant feeding method, breast symptoms, and perception of whether the onset of lactation had occurred. Medical records were reviewed. Subjects/setting Data were collected from 192 women after they gave birth to a healthy, term singleton. Statistical analyses performed χ 2 Analyses were used to identify variables associated with delayed onset of lactation (onset of lactation ≥72 hours postpartum). Multivariate logistic regression was used to identify the independent association of each significant variable with delayed onset of lactation. Results Risk factors for delayed onset of lactation included white/Hispanic ethnicity, heavy/obese body build, delivery of offspring by unscheduled cesarean delivery, vaginal delivery with prolonged stage 2 labor, infant birth weight less than 8 lb, and exclusive formula-feeding before the onset of lactation. Applications/conclusions Women who are at risk for delayed onset of lactation need additional breast-feeding support during the first week postpartum. During their hospitalization, these women should be instructed about the normal lactation process and the possibility that onset of lactation may occur later than 72 hours postpartum. Frequent nursing should be recommended, as delayed onset of lactation was associated with the lack of infant suckling. JAm Diet Assoc. 1999;99:450-454.
306 citations
TL;DR: Investigating effects of exogenous fibrolytic enzyme supplementation on dry matter intake, milk production, and digestibility in multiparous lactating Holstein cows in early lactation found it has the potential to enhance milk yield and nutrient digestibility of cows inEarly lactation without changing feed intake.
265 citations
TL;DR: The effects of milk fever, ketosis, and lameness were studied using data from 23,416 Finnish Ayrshire cows that calved in 1993 and were followed for one lactation to model the association among the repeated measurements.
261 citations
TL;DR: Elevated respiratory quotient and carbohydrate utilization during pregnancy continue during lactation, consistent with preferential use of glucose by the fetus and mammary gland, and results indicate increased energy expenditure and preferentialUse of carbohydrates during pregnancy and lactation.
221 citations
TL;DR: The majority (15 of 17) of homozygous (rlx-/-) mice are fertile and produce normal litters, however their mammary development is deficient; pups are unable to suckle and die within 24 h of birth unless cross-fostered to a wild-type (RLx+/+) foster mother.
Abstract: We have used gene targeting to generate relaxin (rlx)-deficient mice. The majority (15 of 17) of homozygous (rlx-/-) mice are fertile and produce normal litters. However their mammary development is deficient; pups are unable to suckle and die within 24 h of birth unless cross-fostered to a wild-type (rlx+/+) foster mother. The nipples of rlx-/- animals do not enlarge significantly during pregnancy, and their histology retains the appearance of the virgin state. Breast parenchyma is somewhat underdeveloped at term even though milk is produced. Mammary ducts become grossly dilated in these animals. Heterozygous (rlx+/-) mice lactate normally. The interpubic ligament does not relax during pregnancy in rlx-/- mice. Plasma osmolality during late gestation was significantly higher (P < 0.001) in rlx-/- mice than in wild-type controls.
216 citations
TL;DR: Increased apoptosis and cell proliferation, relative to that in lactating glands during the same stage of gestation, suggest that a nonlactating period serves to promote cellturnover prior to the next lactation.
Abstract: Lifetime milk production is maximized when dairy cows are pregnant during approximately 70% of each lactation. Between lactations, a nonlactating period is necessary for optimal milk production in the succeeding lactation. With cessation of milking, alveolar structure is largely maintained and little or no loss of cells occurs. However, increased apoptosis and cell proliferation, relative to that in lactating glands during the same stage of gestation, suggest that a nonlactating period serves to promote cell turnover prior to the next lactation. Even in the absence of pregnancy, mammary involution in dairy animals occurs at a slower rate than in rodents; alveolar structure is maintained for several weeks and lactation can be reinitiated after four weeks or more of involution. Although apoptosis appears to be initiated within a similar time frame to that in rodents, the maximum proportion of apoptotic epithelial cells appears to be lower than in rodents, and apoptosis may be accompanied by an initial increase in cell proliferation. The ability to manipulate apoptosis and cell proliferation during the nonlactating period and during lactation is expected to provide enormous benefits to the dairy industry.
206 citations
TL;DR: Regardless of the time of occurrence during the lactation, mastitis had a long-lasting effect on milk yield; cows with mastitis did not reach their premastitis milk yields during the remainder of the lactations after onset of the disease.
TL;DR: Estimates of milk losses consequent to dystocia, stillbirth, milk fever, retained placenta, metritis, cystic ovaries, ketosis, displaced abomasum and locomotor disorders were reviewed.
TL;DR: The response of dairy cows fed grass silage-based diets to the abomasal infusion of water or 6.5 g of His alone or in combination with either 6.0 g of Met or 19.0G of Lys is concluded that His is the first-limiting AA when grass silages are supplemented with cereal concentrates, while neither Met nor Lys are the second- Limiting AA with grasssilage feeding.
TL;DR: Local control of apoptosis in rodents during weaning, and after peak lactation in dairyanimals, may be due to the actions of milk-bornesurvival factors or their inhibitors, and can bemanipulated by frequency of milk removal.
Abstract: Lactation depends on regular suckling or milkingof the mammary gland. Without this stimulus, milksecretion stops and mammary involution is induced.Involution caused by abrupt cessation of milk removal is characterized by de-differentiation andapoptosis of mammary epithelial cells, the extent andtime course of the latter varying between species.Apoptosis is inhibited and milk secretion is restored by re-suckling, if milk stasis is of shortduration. Mammary involution and apoptosis also occurduring weaning, even in concurrently-pregnant animalswhen the interval between lactations is restricted, suggesting that tissue remodeling is essentialfor subsequent lactation. Declining milk production inruminants after peak lactation is also associated with,and probably results from, net cell loss by apoptosis. Involution and apoptosis arecontrolled by changes in systemic galactopoietic hormonelevels, and by intra-mammary mechanisms responsive tomilk removal. Milk stasis precipitated by litter removal or cessation of milking may involveintra-mammary control related to physical distension ofthe epithelium. Local control of apoptosis in rodentsduring weaning, and after peak lactation in dairyanimals, may be due to the actions of milk-bornesurvival factors or their inhibitors, and can bemanipulated by frequency of milk removal.
TL;DR: In this article, five standard lactation curve models were used to predict a typical dairy cow lactation derived as the average daily milk yield of 325 complete first lactation Holstein-Friesian cows in one herd.
TL;DR: Because of the occurrence of the noncoagulating milk and a possibly unfavorable genetic trend in the milk coagulation properties, it would be important to improve these traits in the Finnish Ayrshire breed.
TL;DR: The physiology of human lactation is described with secretions on mammary gland anatomy and development, the mechanisms of milk secretion and ejection, and the temporal sequence of events during the transition from pregnancy to lactation (lactogenesis).
TL;DR: It is concluded that altering the forage concentrate ratio in the diet of lactation cows influenced milk yield and milk composition, but the addition of buffer to the diet prevented the elevation in trans-C18:1 fatty acids in milk fat, and related milk fat depression, associated with feeding high-concentrate diets.
TL;DR: For example, this paper examined variation in and patterns of milk composition and production, maternal energy output, and pup growth and energy deposition over the entire lactation period in 18 grey seal mother-pup pairs using hydrogen isotope (3H2O and D2O) dilution.
Abstract: Phocid seals are one of the few groups of mammals capable of sustaining the energetic demands of lactation entirely through body nutrient stores while fasting. Lactation performance of the female in turn influences the rate and pattern of pup growth. We examined variation in and patterns of milk composition and production, maternal energy output, and pup growth and energy deposition over the entire lactation period in 18 grey seal mother-pup pairs using hydrogen isotope (3H2O and D2O) dilution. Milk composition was independent of maternal mass and nutrient stores, indicating dependence on other physiological and genetic factors. Heavier females lactated longer (r2=0.653, P<0.001), had higher total milk outputs (r2=0.652, P<0.001), and produced larger pups at weaning (r2=0.417, P=0.005). While fatter females lactated for longer periods of time (r2=0.595, P<0.001), females with a larger lean body mass at parturition produced more milk (r2=0.579, P<0.001). Total milk energy output was the strongest predictor of pup weaning mass, which, along with the pup's efficiency of energy storage, accounted for 91% of the variation in weaning mass. Nevertheless, there was sufficient plasticity in milk composition and energy output that some smaller females produced relatively large pups. Few females appeared to deplete body nutrients to the point where it might limit the duration of lactation.
TL;DR: The high degree of colocalization of AGRP and NPY, coupled with previous reports from the laboratory demonstrating increased NPY expression in the ARH in response to suckling, suggests that A GRP andNPY are coordinately regulated and may be involved in the increase in food intake during lactation.
Abstract: During lactation, the levels of neuropeptide Y (NPY), which plays an important role in mediating food intake, are significantly elevated in a number of hypothalamic areas, including the arcuate nucleus (ARH). To identify additional hypothalamic systems that might be important in mediating the increase in food intake and alterations in energy homeostasis during lactation, the present studies examined the expression of agouti-related protein (AGRP), a recently described homologue of the skin agouti protein. AGRP is found in the hypothalamus and has been suggested to play an important role in the regulation of food intake. In the first experiment, animals were studied during diestrus of the estrous cycle, a stage of the cycle when estrogen levels are basal and similar to lactation, or during days 12–13 postpartum. Lactating animals had their litters adjusted to eight pups on day 2 postpartum. Brain tissue sections were used to measure AGRP messenger RNA (mRNA) levels by in situ hybridization. AGRP mRNA signa...
TL;DR: In this paper, the authors show that immunomodulating agents are normally present in human milk in physiologically relevant quantities for at least the first 3 mo of the breastfed infant's life.
Abstract: Postpartum changes in the concentrations of IL-1beta, IL-6, tumor necrosis factor-alpha (TNF-alpha), transforming growth factor-beta1 (TGF-beta1), TGF-beta2, and prostaglandin E2 in 257 human milk samples collected longitudinally from 49 healthy mothers during the first 12 wk of lactation were determined by ELISA or RIA The proinflammatory cytokines IL-1beta, IL-6, and TNF-alpha were present in only a proportion of samples, and there was a wide range of concentrations detected at each time in the present study (IL-1beta, <15-400 pg/mL; IL-6, <15-1032 pg/mL; TNF-alpha, <15-2933 pg/mL) Concentrations of prostaglandin E2 increased after the first week and remained elevated for the remainder of the study (range, < 10-9966 pg/mL) The antiinflammatory cytokines TGF-beta1 (range, 43-7108 pg/mL) and TGF-beta2 (range, 208-57935 pg/mL) were present in substantial quantities in all samples, and there was little change in the mean concentration during 12 wk of lactation The present study shows that immunomodulating agents are normally present in human milk in physiologically relevant quantities for at least the first 3 mo of the breast-fed infant's life
TL;DR: There was an apparent increased efficiency of the breast (milk production per unit breast tissue) after 6 months, which may have been due to redistribution of tissues within the breast.
Abstract: Quantitative measurements were made of relative breast volume and milk production from 1 month of lactation until 3 months after weaning, and the storage capacity of the breasts was calculated. The increase in breast tissue volume from before conception until 1 month of lactation was maintained for the first 6 months of lactation (means+/-S.E.M.) (190.3+/-13.1 ml, number of breasts, nb = 46). During this period of exclusive breast-feeding, 24 h milk production from each breast remained relatively constant (453.6+/-201 g, nb = 48), and storage capacity was 209.9+/-11.0 ml (nb = 46). After 6 months, breast volume, milk production and storage capacity all decreased. There was a relationship between 24 h milk production and the storage capacity of the breasts, and these both appeared to be responding to infant demand for milk. At 15 months of lactation, the 24 h milk production of each breast was substantial (208.0+/-56.7 g, nb = 6), even though the breasts had returned to preconception size. This was associated with an apparent increased efficiency of the breast (milk production per unit breast tissue) after 6 months, which may have been due to redistribution of tissues within the breast. The possible causes of the decrease in breast volume are discussed.
TL;DR: Overall, the studies demonstrated that grazing dairy cattle are likely to be infected with gastrointestinal nematode parasites, usually Ostertagia ostertagi and Cooperia species.
Abstract: The results of more than 80 experiments on gastrointestinal parasitism and the impact of anthelmintic treatment on milk production in dairy cattle were reviewed. Abattoir surveys of culled dairy cows, faecal egg counts in milking cows, and serological tests and worm counts in cull cows in milk production studies were collated to assess the level of parasitism in dairy herds. The studies were divided into four general categories: induced infections in previously uninfected cattle; naturally infected cattle treated in mid-lactation; naturally infected cattle treated one to three times during the dry period and/or just before or just after parturition; and naturally infected cattle treated repeatedly from early lactation or given strategic treatments throughout the year. In most studies, the milk production of anthelmintic-treated cattle was compared with that of untreated controls. The anthelmintics investigated included members of the organophosphate, benzimidazole, imidazothiazole and macrocyclic lactone groups. The number of experiments in which the medicated (or uninfected) group had a higher milk yield was compared with the number of experiments in which the control (or infected) group had a higher yield. Overall, the studies demonstrated that grazing dairy cattle are likely to be infected with gastrointestinal nematode parasites, usually Ostertagia ostertagi and Cooperia species. These infections may be present as inhibited larvae, and a periparturient or spring rise is associated with their emergence. There is, at present, no reliable means of determining whether a cow or a herd may be parasitised subclinically at a level sufficient to interfere with milk production. In 70 of 87 experiments (80 per cent) there was an increase in milk production (P < 0.001) after anthelmintic treatment, with a median increase of 0.63 kg/day. In each of the four trial categories, a majority of the studies showed that anthelmintic treatment increased milk production. The yield of milk fat by the medicated cows was greater than by the controls in 26 of the 35 experiments in which that variable was studied (P < 0.01).
TL;DR: A mechanistic model to predict milk urea N concentrations was developed using raw data from 3 studies and was evaluated with 18 independent studies and established target concentrations that were sensitive to changes in milk production and amount of N intake and relatively insensitive to body weight, parity, and grouping strategy.
TL;DR: Bone mineral changes during and after lactation were largely independent of the duration of lactation or amenorrhea, and similar effects were observed in formula-feeding women.
TL;DR: The use of fortified human milk generally provides the premature infant adequate growth, nutrient retention, and biochemical indices of nutritional status when fed at approximately 180 mL/kg/day compared with unfortified human milk.
TL;DR: It is demonstrated that ErbB2 signaling is required for proper mammary development and lactation at parturition and at 1 day post-partum, lactationally active, distended lobuloalveoli failed to form.
Abstract: Overexpression of the receptor tyrosine kinase ErbB2/HER2/Neu (ErbB2) occurs in 15-40% of human breast cancers. To determine the function of ErbB2 signaling during normal mouse mammary gland development, we expressed a carboxyl-terminal truncated dominant negative allele of ErbB2 (ErbB2deltaIC) in the developing mouse mammary gland. Despite ErbB2deltaIC expression within mammary glands of pubescent virgin and pregnant mice, a phenotype was not observed until late in pregnancy. At 1 day post-partum, lactationally active, distended lobuloalveoli failed to form. This phenotype was exaggerated in multiparous females expressing ErbB2deltaIC. Immunohistochemical staining for ErbB2deltaIC revealed a concordance between high levels of ErbB2deltaIC protein expression and the absence of lactational products within the lumens of ErbB2deltaIC stained lobuloalveoli. These results demonstrate that ErbB2 signaling is required for proper mammary development and lactation at parturition.
TL;DR: The results suggest that bat mammary tissue has no mechanism to counteract the effect of reduced body temperature and that periods of lactational torpor are likely to cause a pronounced diurnal variation in the rate of milk secretion.
Abstract: In the pipistrelle bat (Pipistrellus pipistrellus), the metabolic load of lactation is not met to any significant extent by increased food intake or mobilization of body reserves, and aerial foraging accounts for most of the animal's energy expenditure even during lactation. Energy conservation must, therefore, play a critical role in maintaining lactation. The principal mechanism for energy conservation appears to be the bat's ability to enter torpor, but this may itself interrupt milk synthesis and secretion unless the pipistrelle mammary gland is adapted to counteract its effect. The effect of torpor on mammary tissue function was studied in mammary tissue explant cultures prepared in weeks 1–3 of lactation, when milk water yield was 0.20, 0.88, and 0.30 mL/d respectively. Protein synthesis measured by incorporation of radiolabeled amino acids was 44% lower (P < 0.001) in bat tissue explants cultured at ambient temperature (22°C) compared with 37°C. The reduction was similar to that observed in mouse mammary tissue (57%) and was unaffected by stage of lactation. Analysis of explant protein after [35S]methionine labelling showed the majority of proteins synthesised in culture to be milk proteins; it also demonstrated that the decrease in protein synthesis at ambient temperature was a general phenomenon: synthesis of both secretory and intracellular mammary proteins was reduced at the lower culture temperature. The results suggest that bat mammary tissue has no mechanism to counteract the effect of reduced body temperature and that periods of lactational torpor are likely to cause a pronounced diurnal variation in the rate of milk secretion. J. Exp. Zool. 284:35–41, 1999. © 1999 Wiley-Liss, Inc.
TL;DR: Lactating females obtained six times more energy from increased food consumption than from mobilization of fat stores, compared with non-reproductive bats, suggesting they used compensatory mechanisms in their energy budgets in lactation.
Abstract: 1. The energy budgets of lactating and non-reproductive female Brown Long-Eared Bats fed primarily on noctuid moths (≈ 27·2 kJ g–1) were constructed and compared in flight enclosures in captivity.
2. The average dry food consumption of non-reproductive individuals was 1·8 g bat–1 day–1 (gross energy intake = 48 kJ day–1). The average food consumption throughout days 10–35 of lactation was 2·0 g bat–1 day–1 (gross energy intake = 53 kJ day–1). Lactating females obtained six times more energy from increased food consumption than from mobilization of fat stores, compared with non-reproductive bats.
3. Milk export, calculated using the difference in water turnover between lactating and non-reproductive bats (measured using 2H turnover) averaged 2·6 ml bat–1 day–1 (22·9 kJ day–1). This was similar to the average milk intake of sucklings estimated from 3H turnover (22·9 kJ day–1).
4. Energy available for respiration from food and mobilization of fat stores was 18·2 kJ day–1 for lactating females compared with 36·8 kJ day–1 for non-reproductive females. In comparison, respiratory daily energy expenditure (DEE) of lactating and non-reproductive bats, measured by doubly labelled water (DLW), was 21·3 kJ day–1 and 23·6 kJ day–1, respectively. Hence, there was a discrepancy between respiratory DEE (measured by DLW) and net available energy estimates for non-reproductive bats but not for lactating bats.
5. Respiratory DEE for lactating bats was equal to or less than that of non-reproductive females, suggesting they used compensatory mechanisms in their energy budgets in lactation.
TL;DR: Disruption of the genes for PRLand the PRL receptor, as well as those for transcription factors important in mammary gland regulation(Stat proteins), have provided a new set of animal models with which to study normal mammary glands development and the relationships of PRL to breastcarcinogenesis.
Abstract: Prolactin (PRL) regulates the development of the mammary gland at three stages in the reproductive life history of females. The first stage is mammary gland organogenesis, during which PRL contributes to the maturation of the mammary glands from a primary ductal system, which grows from terminal end buds, to the fully mature nonpregnant gland. The mature mammary gland is characterized by an absence of terminal end buds, and the development of a highly branched architecture, which is decorated by lobular buds. During pregnancy PRL, placental lactogens, and progesterone stimulate the expansion and physiological differentiation of the lobuloalveolar system from the lobular buds. After delivery PRL, in the context of falling progesterone, stimulates the final induction of milk protein gene expression and lactation. PRL acts directly on the mammary epithelium, and indirectly by stimulating luteal progesterone secretion in rodents. Disruption of the genes for PRL and the PRL receptor, as well as those for transcription factors important in mammary gland regulation (Stat proteins), have provided a new set of animal models with which to study normal mammary gland development and the relationships of PRL to breast carcinogenesis. Two major deficiencies in our current knowledge of PRL actions are our understanding of the role of epithelial-stromal interactions in PRL-induced mammary morphogenesis, and the identity of developmentally important genes that are regulated by PRL during normal mammary gland organogenesis.