Showing papers on "Lactation published in 1998"
TL;DR: The long-term lowering of blood pressure and of cortisol levels as well as the sedative effects of oxytocin have been found to be related to an increased activity of central alpha 2-adrenoceptors, which may explain the health-promoting effects of certain alternative therapies.
834 citations
TL;DR: The results indicate that the reduced response of the HPA axis to stressors described previously during lactation is already manifested around day 15 of pregnancy in the rat and involves physiological adaptations at the adenohypophysial level.
Abstract: 1. The responsiveness of the rat hypothalamo-pituitary-adrenal (HPA) axis and hypothalamo-neurohypophysial system (HNS) to emotional (elevated plus-maze) and physical (forced swimming) stressors and to administration of synthetic corticotrophin-releasing hormone (CRH) was investigated during pregnancy and lactation. In addition to pregnancy-related adaptations at the adenohypophysial level, behavioural responses accompanying the neuroendocrine changes were studied. 2. Whereas basal (a.m.) plasma corticosterone, but not corticotrophin (adrenocorticotrophic hormone; ACTH), levels were increased on the last day (i.e. on day 22) of pregnancy, the stress-induced rise in both plasma hormone concentrations was increasingly attenuated with the progression of pregnancy beginning on day 15 and reaching a minimum on day 21 compared with virgin control rats. A similar attenuation of responses to both emotional and physical stressors was found in lactating rats. 3. Although the basal plasma oxytocin concentration was elevated in late pregnancy, the stress-induced rise in oxytocin secretion was slightly lower in day 21 pregnant rats. In contrast to vasopressin, oxytocin secretion was increased by forced swimming in virgin and early pregnant rats indicating a differential stress response of these neurohypophysial hormones. 4. The blunted HPA response to stressful stimuli is partly due to alterations at the level of corticotrophs in the adenohypophysis, as ACTH secretion in response to CRH in vivo (40 ng kg-1, i.v.) was reduced with the progression of pregnancy and during lactation. In vitro measurement of cAMP levels in pituitary segments demonstrated reduced basal levels of cAMP and a lower increase after CRH stimulation (10 nM, 10 min) in day 21 pregnant compared with virgin rats, further indicating reduced corticotroph responsiveness to CRH in pregnancy. 5. The reduced pituitary response to CRH in late pregnancy is likely to be a consequence of a reduction in CRH receptor binding as revealed by receptor autoradiography. [125I] CRH binding in the anterior pituitary was significantly reduced in day 11, 17 and 22 pregnant rats compared with virgin controls. 6. Anxiety-related behaviour of the animals as revealed by the time on and entries into the open arms of the elevated plus-maze was different between virgin and pregnant rats with decreased number of entries indicating increased anxiety with the progression of pregnancy (except on pregnancy day 18). The emotional behaviour, however, was not correlated with the neuroendocrine responses. 7. The results indicate that the reduced response of the HPA axis to stressors described previously during lactation is already manifested around day 15 of pregnancy in the rat and involves physiological adaptations at the adenohypophysial level. However, alterations in stressor perception at higher brain levels with the progression of pregnancy may also be involved.
367 citations
TL;DR: In this paper, the authors consider the potential effects on the calf prior to and after calving and suggest that low protein diets may increase the incidence of respiratory acidosis, which may impair the acquisition of passive immunity.
304 citations
TL;DR: The mammary gland is characterized by a unique dependence on hormonal signals for terminal differentiation, which is attained only after pregnancy as discussed by the authors, and it was introduced 200 million years ago with the appearance of mammals to provide nourishment to the newborn in the form of milk.
Abstract: On a phylogenetic scale of organ development the mammary gland is a recent acquisition. It was introduced 200 million years ago with the appearance of mammals to provide nourishment to the newborn in the form of milk. The mammary gland is characterized by a unique dependence on hormonal signals for terminal differentiation, which is attained only after pregnancy. At the time of birth, the anlage consists of a few rudimentary ducts in the vicinity of the nipple. Pronounced ductal outgrowth and branching commences at puberty, and in pregnancy an expanded lobulo-alveolar compartment develops. Functional differentiation of the secretory epithelium coincides with parturition and large amounts of milk are produced and secreted during lactation. After weaning of the young, the entire alveolar epithelial compartment is remodeled to resemble a virgin-like state. With each pregnancy, a new round of lobulo-alveolar development occurs. During the past 100 years, intensive efforts have been made to understand the endocrine control of mammopoiesis and lactogenesis. Classical research on endocrine ablated animals firmly established that ovarian steroids and pituitary peptide hormones are mandatory and sufficient for breast development and lactation. In 1900, Halban first established that mammary growth is controlled by the ovary (Halban 1900). He demonstrated that ovariectomy caused mammary regression, and that transplanted ovaries prevented the castration atrophy of mammary glands. Twenty-eight years later, Stricker and Grueter induced mammary development and milk secretion artificially in castrated virgin rabbits by injection of pituitary extract (Stricker and Grueter 1928). In 1933, Riddle, Bates, and Dykshorn purified the respective pituitary hormone (Riddle et al. 1933) and named it prolactin(PRL). In the last several years, the ability to delete genes from the mouse genome has allowed us to identify genetic components of mammary gland development. Molecular insight into the underlying genetic framework and signaling networks of the developing tissue has been gained through experimental manipulations of tissues from wild-type and knockout mice. Two distinct, yet braided, developmental concepts have unfolded. First, discrete signaling networks activated by systemic endocrine hormones induce mammopoiesis. Secondly, some of these signals are relayed through reciprocal interactions between the epithelium and the stroma. Table 1 contains those genes whose elimination from the mouse genome results in impaired mammary gland development. Among these genes are some of the ‘‘usual suspects’’ but also some previously unidentified players. Each mutation affects specific and distinct aspects of mammary development. These knockout mice not only confirmed the involvement of hormonal signaling but also provided tools to identify the tissue compartment that receives and executes these signals.
280 citations
TL;DR: It is indicated that spreading calving throughout the year would lessen seasonal variations in the gross composition of mill supplied to factories, leading to a more even distribution of product yield across the year.
Abstract: This study was designed to evaluate the respective influences of stage of lactation (SOL) and time of year on the seasonal variation in milk composition for pasture-fed dairy cows in New Zealand. Four herds of approximately 20 Friesian cows were used, one herd calving in a 6 week period beginning in each of January, April, July and October. Cows grazed rye-grass-white clover pasture only, except during June when all cows received supplementary pasture silage. Milk samples were collected from each cow in milk on four occasions during the year (September, December, March and June), to give a total of three samples per cow (early, mid and late lactation; about 30, 120 and 210 d respectively after calving). Samples were analysed for a detailed range of components. Concentrations of many milk components (e.g. total protein, fat, casein and whey protein) increased as lactation progressed; the extent of these increases depended on the time of year. These results indicated that spreading calving throughout the year would lessen seasonal variations in the gross composition of mill supplied to factories, leading to a more even distribution of product yield across the year. Despite this, variations in some important manufacturing properties were affected by time of year but not by SOL. Ratios of protein: fat and casein: whey protein were not significantly affected by SOL, but were affected by time of year. The solid fat content of milk was also affected by time of year. Seasonal variations in the manufacturing properties of milk may be reduced but not eliminated by changing the time of calving.
278 citations
TL;DR: During machine-milking, the physiological requirements of the cows need to be considered, and, most importantly, stressors must be minimized.
246 citations
TL;DR: Results indicate that primiparity, long labor, stress to the mother and fetus during labor and delivery, and elevated cord glucose concentrations are risk factors for delayed lactogenesis.
206 citations
TL;DR: Dystocia, retained placenta, and early metritis significantly affected milk yield, as indicated by monthly test day milk yields, and late metritis was not associated with milk loss.
191 citations
TL;DR: In both types of oxytocin gene disablement, the only evident defect was a complete failure of postpartum homozygotes to transfer milk to the suckling young, which consequently did not survive unless the mothers were treated with exogenous oxytocIn, and these findings are surprising in view of the vast literature on a wide range of species suggesting important roles for oxytoc in regulating gonadal function, in expression of sexual behaviour, in parturition and initiation of maternal behaviour as well as
Abstract: Our understanding of the functions of oxytocin in mammals has recently been challenged by findings in transgenic mice in which the oxytocin gene has been knocked out. Mammals generally have only two posterior pituitary nonapeptide genes, for oxytocin and vasopressin, while some marsupials do not express oxytocin but do express a closely related peptide, mesotocin, which acts at the oxytocin receptor (Acher et al. 1995). Birds have arginine vasotocin and mesotocin (Acher et al. 1995), while among other vertebrates a subclass of cartilaginous fishes evidently produces oxytocin (Michel et al. 1993). Mice homozygous for deletion of exon 1 of the oxytocin gene, containing the oxytocin nonapeptide sequence, were produced by homologous recombination in mouse embryonic stem cells. Offspring from matings of the heterozygotes were in the correct Mendelian frequency, indicating no lethal developmental defects in the homozygotes, which later showed normal sexual maturation, with both males and females showing sexual behaviour and normal fertility (Nishimori et al. 1996). Young and colleagues (1996) used gene targeting to generate a mouse with most of the first intron and the last two of the three exons of the oxytocin gene eliminated. The amount of oxytocin gene transcripts in the supraoptic and paraventricular nuclei of homozygotes was 1% of the wild-type level, with less than 0·4% of the wild-type content of oxytocin in the pituitary gland, and no oxytocin detectable in blood plasma by RIA. In both types of oxytocin gene disablement, the only evident defect was a complete failure of postpartum homozygotes to transfer milk to the suckling young, which consequently did not survive unless the mothers were treated with exogenous oxytocin. Thus parturition and maternal behaviour proceeded without oxytocin, although these processes were not studied in detail. These findings are surprising in view of the vast literature on a wide range of species suggesting important roles for oxytocin in regulating gonadal function, in expression of sexual behaviour, in parturition and initiation of maternal behaviour as well as in lactation. It is appropriate to consider whether the results from the oxytocin knockout mice arise from peculiarities in the roles of oxytocin in the mouse in comparison with other species, or indicate redundancy in the mechanisms in which oxytocin normally has an important role; apart that is, from the milk-ejection reflex in which there is no evident redundancy, at least in the mouse.
154 citations
TL;DR: Reducing the dosage of GnRH used for synchronization of ovulation and timed AI in lactating dairy cows reduces synchronization costs per cow and per pregnancy without compromising the efficacy of the synchronization protocol.
154 citations
TL;DR: Yeast supplementation during early lactation significantly improved DM intake, milk yield, and the digestibility of crude protein and acid detergent fiber in multiparous Holstein cows.
TL;DR: The diet containing oilseeds and supplemented with an adequate amount of vitamin E allowed cows to yield milk that could be used to manufacture butter with high oleic acid content, good spreadability, and resistance to oxidation.
Journal Article•
TL;DR: The value of further studies was underlined, especially to provide more accurate quantification of the composition changes associated with elevated SCC, and to improve the imperfect knowledge about the effects of parity and stage of lactation on the studied relationships.
Abstract: Relationships between somatic cell count (SCC) and variation in milk production at the cow level were reviewed to provide average reference values suitable for the assessment of economic losses due to subclinical mastitis. The literature analysis involved 19 papers, defining milk yield and/or its composition either at test-day level or at the whole lactation level as statistical unit. Within each type of approach, study populations and designs differed. Regression models implemented also showed large differences. At test-day level, the average trend was a loss of 0.4 kg of milk in primiparous cows and 0.6 kg in multiparous, by each 2-fold increase of SCC above 50,000 cells/mL. At the lactation level, the average trend was a loss of 80 kg of milk in primiparous and 120 kg in multiparous, by each 2-fold increase of the geometric mean of SCC above 50,000 cells/mL. Protein content of milk showed a small increase of 0.15 g/kg (at the test-day level) while fat content showed a small decrease of 0.20 g/kg (both at the test-day and at the lactation level), by each 2-fold increase of SCC. The value of further studies was underlined, especially to provide more accurate quantification of the composition changes associated with elevated SCC, and to improve the imperfect knowledge about the effects of parity and stage of lactation on the studied relationships.
TL;DR: The authors showed that supplementing formula-fed preterm or full-term infants with docosahexaenoic acid and arachidonic acid leads to plasma and red blood cell LC-PUFA levels similar to those of breastfed infants.
Abstract: Long-chain polyunsaturated fatty acids (LC-PUFA) are essential for normal development. Fetal accretion of LC-PUFA occurs during the last trimester of gestation; therefore, premature infants are born with minimal LC-PUFA reserves. Recent studies indicate that the newborn can synthesize LC-PUFA from essential fatty acid precursors; however, the extent of de novo synthesis remains to be established. Postnatally, human milk provides LC-PUFA to the newborn. Maternal LC-PUFA reserves depend upon diet and can be improved by supplementation of docosahexaenoic acid and arachidonic acid during pregnancy and lactation. This in turn affects fetal LC-PUFA accretion and postnatal provision through mother's milk. Supplementation of formula-fed preterm or full-term infants with docosahexaenoic acid and arachidonic acid leads to plasma and red blood cell LC-PUFA levels similar to those of breast-fed infants. The higher blood and presumably tissue levels of LC-PUFA following supplementation lead, however, to only temporary functional benefits.
TL;DR: The contribution of maternal endogenous conversion of linoleic acid to milk dihomo-gamma-linolenic and arachidonic acids is studied, using stable isotope techniques, to estimate that about 30% of milk linolesic acid is directly transferred from the diet.
TL;DR: Simplified procedures based on only one milking could be effective in the testing programs for milk yield and SCC, thus, reducing the economic costs of milk recordings in mammary health and breeding programs.
TL;DR: Results indicate that the length and geometry of the dendritic trees of OT and VP neurons are altered in opposite ways during lactation, affect the availability of postsynaptic space and alter the electrotonic properties of the neurons, affecting the efficacy of synaptic inputs.
Abstract: Oxytocin (OT) and vasopressin (VP) release from the neurohypophysis are correlated with the electrical activity of magnocellular cells (MNCs) in the supraoptic (SON) and paraventricular nuclei. Synaptic inputs to MNCs influence their electrical activity and, hence, hormone release. During lactation OT neurons display a synchronized high-frequency bursting activity preceding each milk ejection. In parallel to the adoption of this pattern of electrical activity, an ultrastructural reorganization of the SON has been observed during lactation. In the present study we performed a light microscopic, morphometric analysis of identified OT and VP neurons in the SON to determine whether the dendrites of these neurons participate in the plasticity observed during lactation. The dendritic trees of OT neurons shrunk during lactation ( approximately 41% decrease in the total dendritic length) because of a decreased dendritic branching concentrated at a distance of 100-200 microm from the soma. No changes in the maximal distal extension were observed. The distribution pattern of dendritic length into branch orders also was affected. Strikingly, opposite effects were observed in VP neurons. The dendritic trees during lactation elongated ( approximately 48% increase in the total dendritic length) because of an increased branching close to the soma. No changes in the maximal distal extension were observed. These results indicate that the length and geometry of the dendritic trees of OT and VP neurons are altered in opposite ways during lactation. These changes would influence the availability of postsynaptic space and alter the electrotonic properties of the neurons, affecting the efficacy of synaptic inputs.
TL;DR: Stable lead isotope and lead concentration data are obtained from a longitudinal study of mobilization of lead from the maternal skeleton during pregnancy and lactation and in which the newly born infants were monitored for 6 months postpartum to evaluate the effects of the local environment on lead body burden of the infant.
Abstract: We have obtained stable lead isotope and lead concentration data from a longitudinal study of mobilization of lead from the maternal skeleton during pregnancy and lactation and in which the newly born infants were monitored for 6 months postpartum to evaluate the effects of the local environment on lead body burden of the infant. Samples of maternal and infant blood, urine, and diet and especially breast milk were measured for 21 mothers and 24 infants. Blood lead concentrations were less than 5 microg/dl in all except one subject. The mean lead concentration in breast milk +/- standard deviation was 0.73 +/- 0.70 microg/kg. In seven subjects for whom serial breast milk sampling was possible, the lead concentration varied by factors of from 2 to 4, and for three subjects there was an increase at or after 90 days postpartum. For the first 60-90 days postpartum, the contribution from breast milk to blood lead in the infants varied from 36 to 80%. Multiple linear regression analyses indicated statistically significant relationships for some of the variables of isotope ratios and lead concentrations between breast milk, blood, urine, and diet for infants and mothers. For example, the analyses revealed that both a mother's breast milk 207Pb/206Pb and 206Pb/204Pb ratios and lead concentration provide information to predict her infant's blood 207Pb/206Pb and 206Pb/204Pb ratios. The major sources of lead in breast milk are from the maternal bone and diet. An evaluation of breast milk lead concentrations published over the last 15 years indicates that studies in which the ratio of lead concentrations in breast milk to lead concentrations in whole maternal blood (Multiple>100) were greater than 15 should be viewed with caution because of potential contamination during sampling and/or laboratory analyses. Selected studies also appear to show a linear relationship between breast milk and maternal whole blood, with the percentage of lead in breast milk compared with whole blood of <3% in subjects with blood lead levels ranging from 2 to 34 microgram/dl. The levels of lead in breast milk are thus similar to those in plasma. Breast-fed infants are only at risk if the mother is exposed to high concentrations of contaminants either from endogenous sources such as the skeleton or exogenous sources.
TL;DR: Uptake, synthesis and desaturation of FA by the mammary gland of dairy cows are affected by arterial concentrations of 16:0, 18:0 and cis-18:1(n-9); mean chain length was significantly reduced by P and O treatments, suggesting an effect of Mammary gland uptake of long-chain FA on the termination process of mammary glands synthesis of FA.
Abstract: The effect of dietary lipids on the fatty acid (FA) profile of cows' milk fat is mainly dependent on digestive processes and mammary gland uptake and metabolism of FA. The objective of this study was to determine the separate effects of high arterial concentrations of 16:0, 18:0 and cis-18:1(n-9) on uptake, synthesis and 18:0 desaturation rate in the mammary gland of lactating dairy cows, via arterio-venous differences and mammary gland balance of FA. In a 4 x 4 Latin square, four lactating Holstein cows with cannula in the proximal duodenum were infused duodenally with a mixture providing daily 0 (C treatment) or 500 g FA with mainly 16:0 (P treatment), 18:0 (S treatment) or cis-18:1(n-9) (O treatment). Significantly higher arterial concentrations of infused FA in arterial plasma nonesterified FA and triglycerides (NETGFA) were observed with P and O treatments, but the effect of the S treatment was much lower. Arterio-venous differences of NETGFA increased with arterial concentrations. The number of synthesized FA in the mammary gland was not significantly affected by duodenal infusion of FA. Mean chain length was significantly reduced by P and O treatments, suggesting an effect of mammary gland uptake of long-chain FA on the termination process of mammary gland synthesis of FA. Across all treatments, 4:0 mammary gland balance increased linearly (r = 0.67, P = 0.004) with mammary gland FA uptake. Mammary gland desaturation of 18:0 to cis-18:1(n-9) averaged 52% and was not significantly affected by treatments, but was reduced by trans-18:1 mammary gland uptake. Uptake, synthesis and desaturation of FA by the mammary gland of dairy cows are affected by arterial concentrations of 16:0, 18:0 and cis-18:1(n-9).
TL;DR: Thirty sows were allocated at their first farrowing to five litter size treatments by cross-fostering within 48 h post partum and milk yield was linearly related to litter size.
Abstract: Thirty sows were allocated at their first farrowing to five litter size treatments. Litter sizes of six, eight, 10,12 and 14 were established by cross-fostering within 48 h post partum. Milk yield (Y, kg/day) of sows was linearly related to litter size (L) and was described by the equations; Y = 5·98 (s.e. 0·48) + 0·689 (s.e. 0·046)L, R2 = 0·99; residual s.d. = 0·29; P < 0·001 and Y = 8·20 (s.e. 0·46) + 0·324 (s.e. 0·044)1, R2 = 0·95; residual s.d. = 0·28; P < 0·002 for early (day 10 to day 14) and late (day 24 to day 28) lactation, respectively. The composition of milk from sows suckling various litter sizes remained relatively stable but suckling frequency in early lactation increased linearly in response to increased litter size. Litter size significantly affected the average growth rate of individual piglets; piglet growth rate from birth to weaning at 28 days of age decreased from 283 g/day to 202 giday in response to increasing litter size from six to 14. The relationships between milk yield, average piglet growth rate and litter size indicate that the number of functional glands is the major factor influencing milk yield of sows. Increasing the number of functional glands by increasing litter size more than compensates for any decrease in milk output from individual glands.
TL;DR: Weight loss, particularly lean tissue loss, was minimized by feeding the high-protein diet during lactation and the VFI during the first 2 wk of lactation was affected only by body fatness and not by the protein content of the lactation diet.
Abstract: We used 35 primiparous sows to investigate the link between body fatness at farrowing and voluntary feed intake (VFI) during lactation. Two groups of sows were fed differently throughout gestation (either 2.3 kg/d of a diet containing 5.8% CP and 14.6 MJ DE/kg as fed or 1.7 kg/d of a diet containing 15.6% CP and 14.5 MJ DE/kg as fed) so that they commenced lactation at a similar body weight (158 to 152 kg) but with different body compositions: either 340 (fat) or 280 (lean) g of body fat/kg BW (P < .001). During lactation, sows were offered either a low-protein diet (7.9% CP and 15.5 MJ DE/kg as fed) or a high-protein diet (19.0% CP and 15.6 MJ DE/kg as fed) on an ad libitum basis. During lactation, VFI was measured daily, and sow body weight and backfat were measured weekly. Blood samples were collected from sows on d 110 of gestation and d 14 and 28 of lactation, and plasma was analyzed for NEFA, glycerol, insulin, glucose, and beta-hydroxybutyrate. Fat sows ate 30% less than their lean counterparts during lactation (P < .001), which corresponded to a 70% higher concentration of NEFA in plasma (P = .01) and a 30% higher concentration of glycerol (P = .15). The VFI during the first 2 wk of lactation was affected only by body fatness and not by the protein content of the lactation diet. The dietary supply of protein influenced VFI during wk 3 and 4 of lactation, possibly by affecting milk production and hence the drive to consume feed. Weight loss, particularly lean tissue loss, was minimized by feeding the high-protein diet during lactation (P < .002).
TL;DR: Calculations show that for achieving a zero protein balance, 45 to 55 g/d of crude lysine are required for normal to high-yielding sows, respectively.
Abstract: Using 73 Large White gilts, we studied the lysine requirement during lactation. Sow and pig performance and nitrogen balance of sows were measured during the total 21-d lactation period. Variation in body composition of sows between farrowing and weaning was determined by the comparative slaughter technique. Two levels of crude protein (15.5 and 17.1%) were combined with two levels of L-lysine HCl supplementation (0 and .16%), resulting in four diets termed P1L1, P1L2, P2L2, and P2L3, containing .66, .77, .77, and .87% crude lysine, and 15.5, 15.5, 17.1, and 17.1% crude protein, respectively. Sows' feed intake, litter growth rate, and milk energy and protein output were not affected by the diet. Nitrogen balance over the total lactation increased (P < .001) with an increase in lysine and(or) protein (-11.7, -7.0, -3.4, and .4 g N/d for P1L1, P1L2, P2L2, and P2L3 diets, respectively). The losses of body weight and muscle weight were higher in P1L1 gilts (P < .01 and .05, respectively) than in gilts on other treatments, whereas the loss of adipose tissue and backfat was similar for the four groups. Multiple linear relationships between lysine intake and milk nitrogen output as predictors and nitrogen balance (N balance = -15.8 + 1.22 lysine - .63 N milk, R2 = .89) or variation of muscle weight (Vm = -477 + 30.1 lysine - 14.7 N milk, R2 = .70) as predicted values were calculated to estimate lysine requirement according to production performance of sows. Calculations show that for achieving a zero protein balance, 45 to 55 g/d of crude lysine are required for normal to high-yielding sows, respectively.
TL;DR: Data indicate that IGF-I can stimulate the synthesis of an IGF binding protein, which enhances its own mitogenic activity, however, whether this mechanism is operative in the lactating mammary gland in vivo is unknown.
TL;DR: The results indicate that feed restriction during lactation inhibits LH pulsatility and ovarian activity.
Abstract: Effects of nutritional deficit during lactation on secretion of gonadotropic hormones and ovarian follicular populations around weaning were investigated in 24 primiparous crossbred sows. Sows were allocated to receive close to ad libitum intakes (H) or approximately 50% of this amount (L) during a 28-d lactation. Serial blood samples were collected 1 d before weaning (W-1), in the hours following weaning (W), and 1 d after (W+1). Their ovaries were removed on the day of weaning or 2 d later (W+2) and subjected to macroscopic and histological observations. Mean and basal LH concentrations were not influenced by the level of feeding. Frequency of LH pulses was reduced in L sows (.17, .5, and .5 vs 1.50, 1.17, and .83 pulses/6 h at d W-1, W, and W+1 respectively; P or = 4 mm (P < .05). Values of these macroscopic characteristics increased after weaning ( P < .05). At weaning, the percentage of healthy follicles was higher in the first class (< 1 mm) and lower in the second class (1 to 2.99 mm) in L compared to H sows (P < .05). Whatever the day of sampling, IGF-I concentrations in follicular fluid tended to be lower in L than in H sows. These results indicate that feed restriction during lactation inhibits LH pulsatility and ovarian activity.
TL;DR: Because of the large variation among and within cows, the monitoring of protein utilization of an individual cow was inaccurate, however, milk urea concentration in bulk milk is a valuable tool to monitor the rumendegraded protein balance in the ration.
TL;DR: Local control of mammary function is reviewed, emphasising the important role played by an autocrine inhibitory protein, the feedback inhibitor of lactation, which operates to influence lactogenesis, gland development and, eventually, gland involution.
Abstract: For the mother, lactation represents the final stage of an investment in her genetic material. Like any investment it is costly and, hence, it needs to be carefully controlled. To her offspring, lactation means survival, so it must happen at any cost. This apparent conflict is rationalized by the mother devolving some control to the offspring while retaining ultimate sanction herself. Part of this results from overt and more subtle influences of the presence of young on the mother's endocrine system, but an equally important part operates at each mammary gland to ensure that output is appropriate to the needs of the young, and no more. The young exert influence by removing milk, while the mother retains control by responding on an hour to hour basis to the presence of milk in the gland. Local control is inevitably most evident where secretion itself is concerned, but also operates to influence lactogenesis, gland development and, eventually, gland involution. This paper will review local control of mammary function, emphasising the important role played by an autocrine inhibitory protein, the feedback inhibitor of lactation.
TL;DR: It is found that maternal diet and increased fat intake through the milk are important regulators of HPA responsiveness in neonates and prepubertal rats and that enhanced ACTH stress responses are observed as in adult rats fed a HF diet.
Abstract: 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.
TL;DR: Infusion of starch abomasally resulted in increases of most uses of glucose, including milk lactose production, glucose oxidation, and the possible storage of glucose as body fat, which indicates that the early lactation dairy cow has a greater capacity for glucose metabolism than is provided by voluntary feed intake of average diets.
TL;DR: First-litter sows fitted with stomach cannulas were used to test the hypothesis that making gilts anabolic during lactation by providing them with extra nutrition would increase milk production and pig growth, and evidence is provided that primiparous sows seem to partition extra energy into body growth rather than into milk production.
Abstract: First-litter sows fitted with stomach cannulas were used to test the hypothesis that making gilts anabolic during lactation by providing them with extra nutrition would increase milk production and pig growth Gilts were allocated to one of three dietary treatments after farrowing: 1) restricted, sows were fed 50% of their estimated ad libitum intake; 2) ad libitum, sows were encouraged to eat as much feed as possible; and 3) superalimented, sows were infused seven times daily through their cannula to achieve a 25 to 30% increase in energy intake in excess of that achieved by sows fed on an ad libitum basis Milk production was estimated in mid- (d 10 to 15) and late (d 21 to 25) lactation by a modification of the isotope dilution technique Milk production was similar between treatments in mid- and late lactation (P > 05), and this was reflected in a similarity in weaning litter weight (P = 238) Milk composition was similar also (P > 05) between dietary treatments Superalimentation provided gilts with 38% more energy (P < 001) than gilts fed on an ad libitum basis, and they accrued live weight (51 kg) and backfat (18 mm) during lactation (P < 001) These data provide evidence that, unlike multiparous sows that show an increase in milk yield when made anabolic during lactation, primiparous sows seem to partition extra energy into body growth rather than into milk production