Duration Of Lactation Research Articles

Morphological profile of the ovaries of high-yielding cows on day 0 of the induced sexual cycle

An important part of reproduction management programmes on dairy farms is the detection of infertile cows and early re-insemination to achieve higher rates of pregnancy. The purpose of the study was to investigate the features of gonadal morphogenesis in high-yielding cows in the conditions of industrial keeping technology on day 0 of the sexual cycle in vivo in real time. Structural, comparative, and statistical methods were used, as well as biotechnical methods of palpation cyclic examination of ovaries with differential diagnosis of morphophysiological or pathomorphological indicators. The results of diagnostics of the ovaries of dairy cows (n=128) on day 0 of the induced cycle detected by step activity sensors showed a significant structural polymorphism of these organs of the reproductive system. It was found: from 66.67% to 30.77% of cows with a physiological course of the follicular phase of the cycle, i.e., on day 0, a preovulatory follicle or the beginning of ovulation on the ovaries (subject to a decrease in the number of cows suitable for insemination with increasing lactation duration from 50-75 days to 211-306 days (P<0.001). Hypogonadism was diagnosed in 19.45% of cows, and in 61.11% – ovarian dysfunctions with the manifestation of cystic follicular degeneration; 19.44% of cows at the time of the study had irreversible chronic adhesive processes of the genital tract tissues in the “ovary+oviduct” area (ovophoritis and ovosalpingitis in latent form), which allowed for pregnancy to occur, with a pronounced tendency to increase this gonadopathy with an increase in lactation (respectively: 50-75 days – 0.00%; 76-160 days – 22.22%; 161-210 days – 22.22%; 211 and more – 33.33%; p<0.05). The trend of influence of subclinical disorders in the metabolism of cows of the experimental herd on the indicators of the biochemical composition of blood serum and the symptom of ovarian dysfunctions was investigated. Thus, the in vivo morphological and pathological profile of the ovaries of high-yielding cows on day 0 of the sexual cycle was established, which allowed optimising the artificial insemination regime and reduce economically nonprofitless sperm consumption. The results can be used in the practical work of veterinary medicine doctors, researchers, and applicants for higher education in veterinary and biological science

Economic valuation of zootechnical indicators in a tropical dairy goat production system

The objective of our study was to promote advances in the economic valuation method of zootechnical indicators in dairy goat farming by incorporating the analysis of the modeling of biological relationships between the indicators. A Multiple Linear Regression model was developed to predict milk production as a function of zootechnical indexes and to determine which indicators influenced and in what proportion the quantity of liters sold. The absolute and relative economic values of these indicators were then calculated. Milk production was influenced by prolificacy (P=0.00325), age at kidding (P=0.01886), duration of lactation (P=< 2e-16) and parity number (P=0.00575), with absolute and relative economic values respectively as follows: $ 0,086/kid/female/year and 62.3% for prolificacy, -$ 0.001/female/month and -0.5% for age at kidding, $ 0.002/female/day and 1.5% for duration of lactation, and $ 0.051/female/parity and 36.7% for parity number. High values for the age at first kidding and interval between kiddings may be responsible for the effect of age and parity number. In conclusion, the procedures were herein employed and validated to improve the economic valuation method proved to be viable and efficient for application in dairy goat farming. In the situation analyzed, more than 90% of the economic value was obtained by prolificacy and parity number; however, the scarcity of research on these aspects of goat farming and the different indicators analyzed demonstrate the need for continuity of research in order to improve the methods so that their use in the field is applicable in more accessible ways.

REARING RODENT PUPS IN FOSTER FAMILIES OF TNEIR OWN OR ANOTHER MAMMAL SPECIES: SURVIVAL AND THE CAUSES OF MORTALITY

Conditions of rearing pups at an early age render a significant impact on subsequent development, reproduction and certain features of the behavior of mammals including rodents. Parents, mostly lactating females, are the main component of the social environment of pups at the early period of postnatal ontogenesis in most mammal species. Therefore, rearing pups in foster families of their own (in-fostering) or another, even taxonomically distant species (cross-fostering) is one of the main methods of assessing the impact of early experience and maternal environment on the development of animal behavior. Cross-fostering or in-fostering is also used for the conservation of valuable animal species. Therefore, more effective fostering methods that provide the maximum survival of the young are necessary to be developed. According to this, we investigated the survival and possible causes of the mortality of rodent pups representing several species in foster families of their own or another mammal species. We conducted a series of experiments on the cross-fostering and in-fostering of house (Mus musculus) and mound-building (Mus spicilegus) mice, yellow steppe lemmings (Eolagurus luteus) and brown rats (Rattus norvegicus), and on rearing rat pups in foster families of the European polecat (Mustela putorius). The proportion of successfully cross-fostered pups (0–68.4) was lower compared to the in-fostered (93.3–100) ones. This result is presumably explained by more significant differences in the maternal environment when reared by a heterospecific female. According to the literature data, the age of foster and recipient female pups, species-specific differences of odor, the presence or absence of a male and the level of paternal care, the level of stress of the mother and offspring, the expression of maternal instinct, the previous female experience in rearing its own and foster pups, the duration of lactation and the nutritional value of maternal milk are the factors that seem to affect the survival and mortality of foster pups.

Associations of Physical Activity and Lactation Duration With Cardiometabolic Risk Factors: The CARDIA Study

BackgroundPhysical activity (PA) and lactation benefit cardiometabolic health. ObjectivesThe purpose of this study was to describe the joint associations of PA and lactation with cardiometabolic risk. MethodsWe averaged PA across exams and summed lifetime lactation in Black and White parous women in the Coronary Artery Risk Development in Young Adults Study. Categories were created for PA (−PA: <median; +PA: ≥median) and lactation (−L: <3 months, +L: ≥3 months). Participants were assigned to one of 4 groups: −PA/−L, −PA/+L, +PA/−L, and +PA/+L (most favorable). Cardiometabolic risk factors at the year 30 exam were standardized into a risk score. We evaluated associations of groups with risk factors and risk score using linear regression. Covariates included age, race, study center, parity, education, smoking, medication use, alcohol consumption, and baseline body mass index, and diet quality. ResultsThe median PA was 256 exercise units and 54% reported lactation duration of ≥3 months. Of 1,068 participants, 303 were in the −PA/−L category, 231 in −PA/+L, 184 in +PA/−L, and 350 in +PA/+L. +PA/+L participants were older, had more years of education, lower body mass index, gained less weight, and less likely to be Black vs −PA/−L participants. Risk scores differed between categories except −PA/+L and +PA/−L (P = 0.08): −PA/−L: 0.23+/−0.04, −PA/+L: 0.08+/−0.04, +PA/−L: −0.02+/−0.05, and +PA/+L: −0.23+/−0.03. After adjustment, +PA/+L was associated with a lower/better risk score (β = −0.15, 95% CI: −0.25 to −0.04). ConclusionsAbove average PA throughout adulthood combined with ≥3 months of lactation was associated with lower risk scores. Participants with either behavior had lower risk vs those with neither behavior. Attaining these levels of behaviors may reduce cardiometabolic risk in parous women.

Higher Availability of Long-Chain Monounsaturated Fatty Acids in Preterm than in Full-Term Human Milk.

While the role of n-3 and n-6 long-chain polyunsaturated fatty acids (LCPUFAs) in the maturation of the infantile nervous system is extensively studied and relatively well-characterized, data on the potential developmental importance of the n-9 long-chain monounsaturated fatty acid (LCMUFA), nervonic acid (NA, C24:1n-9) are scarce and ambiguous. Therefore, the aim of the present study was to reanalyze our available data on the contribution of NA and its LCMUFA precursors, gondoic acid (C20:1n-9) and erucic acid (EA, C22:1n-9) to the fatty acid composition of human milk (HM) during the first month of lactation in mothers of both preterm (PT) and full-term (FT) infants. HM samples were obtained daily during the first week of lactation, and then on the 14th, 21st, and 28th days. Values of the LCMUFAs, C20:1n-9, EA, and NA were significantly higher in colostrum than in transient and mature HM. Consequently, there were highly significant inverse associations between LCMUFA values and the duration of lactation. Moreover, C20:1n-9, EA, and NA values were monotonously, considerably, and at many timepoints significantly higher in PT than in FT HM samples. By the 28th day of lactation, summarized LCMUFA values in PT HM samples declined to the level measured in FT HM samples on the first day of lactation; however, EA and NA values were still significantly higher in PT than in FT HM on the 28th day. Significantly higher availability of LCMUFAs in PT than in FT HM underpins the potential biological role of this hitherto somewhat neglected group of fatty acids.

Infant factors that impact the ecology of human milk secretion and composition—a report from “Breastmilk Ecology: Genesis of Infant Nutrition (BEGIN)” Working Group 3

Infants drive many lactation processes and contribute to the changing composition of human milk through multiple mechanisms. This review addresses the major topics of milk removal; chemosensory ecology for the parent–infant dyad; the infant’s inputs into the composition of the human milk microbiome; and the impact of disruptions in gestation on the ecology of fetal and infant phenotypes, milk composition, and lactation. Milk removal, which is essential for adequate infant intake and continued milk synthesis through multiple hormonal and autocrine/paracrine mechanisms, should be effective, efficient, and comfortable for both the lactating parent and the infant. All 3 components should be included in the evaluation of milk removal. Breastmilk “bridges” flavor experiences in utero with postweaning foods, and the flavors become familiar and preferred. Infants can detect flavor changes in human milk resulting from parental lifestyle choices, including recreational drug use, and early experiences with the sensory properties of these recreational drugs impact subsequent behavioral responses. Interactions between the infant’s own developing microbiome, that of the milk, and the multiple environmental factors that are drivers—both modifiable and nonmodifiable—in the microbial ecology of human milk are explored. Disruptions in gestation, especially preterm birth and fetal growth restriction or excess, impact the milk composition and lactation processes such as the timing of secretory activation, adequacy of milk volume and milk removal, and duration of lactation. Research gaps are identified in each of these areas. To assure a sustained and robust breastfeeding ecology, these myriad infant inputs must be systematically considered.

Milk production of dairy cow at PT. Ultra Peternakan Bandung Selatan

This study aims to determine the effect of body condition score (BCS), lactation length, and dry period on milk production of dairy cows at PT. Ultra Peternakan Bandung Selatan (UPBS). The research was conducted at PT. UPBS, Pengalengan, West Java, the following method used is survey method, where the data of primary and secondary data using 130 lactating dairy cows 3. Complete milk production records as variable y and BCS, lactation length, and dry period as variable x. The effect of BCS, duration of lactation, and dry period were analyzed using multiple linear regression analysis. The results of this study discovered that each factor of BCS, lactation length and dry period duration a very significant effect (P<0,01) with a coefficient of determination (R2) of 76.2%, average milk production 7835±631,33 kg, BCS score 3,25 ±0,26; lactation length is 346±65,26 days, and dry period (R2) is 77±33,18 days. The conclusions of this study; to optimize milk production, the implementation of dairy cows maintenance needed on BCS, lactation length, and optimal dry period according to the recommendations.

Maternal perceptions of human milk expression output: An experimental design using photographs of milk

BackgroundThe widespread use of breast pumps in the United States is a recent phenomenon that is reshaping how individuals understand and perceive lactation. In the 1990s, adequacy of milk supply was primarily measured indirectly by infant weight gain and/or diapers; now >95% of all lactating persons in the United States use breast pumps and are seeing their milk regularly. How seeing milk impacts the perception of lactation sufficiency is an important area of research.Research aim/question: To understand personal and intersubjective influences of seeing expressed human milk on perceptions of milk supply among participants who express milk for their infants. MethodsWe surveyed 805 lactating participants from the United States about their pumping practices using an online survey. Participants described pumping practices, milk output, and beliefs. They were then randomized to view one of three photographs of expressed milk (<2 oz, 4 oz, >6oz) and asked to imagine they had just pumped that amount and provide a written response; this created 4 exposure groups (2 increase and 2 decrease) and a control group (no difference). ResultsParticipants randomized to a higher volume reported more positive feelings and used the terms “good”, “great”, and “accomplished” to describe emotional responses to output. Participants randomized to lower milk volumes reported more feelings of “bad” or “depressed.” A subset of participants reported feeling “annoyed” about small volumes of milk. ConclusionsParticipants in this study were very conscious of the volume of milk pumped each session; both increases and decreases were associated with emotional responses that could contribute to decisions about pumping practices, perceived milk supply, and lactation duration.

Fitness correlates of blubber oxidative stress and cellular defences in grey seals (Halichoerus grypus): support for the life-history-oxidative stress theory from an animal model of simultaneous lactation and fasting.

Life-history-oxidative stress theory predicts that elevated energy costs during reproduction reduce allocation to defences and increase cellular stress, with fitness consequences, particularly when resources are limited. As capital breeders, grey seals are a natural system in which to test this theory. We investigated oxidative damage (malondialdehyde (MDA) concentration) and cellular defences (relative mRNA abundance of heat shock proteins (Hsps) and redox enzymes (REs)) in blubber of wild female grey seals during the lactation fast (n = 17) and summer foraging (n = 13). Transcript abundance of Hsc70 increased, and Nox4, a pro-oxidant enzyme, decreased throughout lactation. Foraging females had higher mRNA abundance of some Hsps and lower RE transcript abundance and MDA concentrations, suggesting they experienced lower oxidative stress than lactating mothers, which diverted resources into pup rearing at the expense of blubber tissue damage. Lactation duration and maternal mass loss rate were both positively related to pup weaning mass. Pups whose mothers had higher blubber glutathione-S-transferase (GST) expression at early lactation gained mass more slowly. Higher glutathione peroxidase (GPx) and lower catalase (CAT) were associated with longer lactation but reduced maternal transfer efficiency and lower pup weaning mass. Cellular stress, and the ability to mount effective cellular defences, could proscribe lactation strategy in grey seal mothers and thus affect pup survival probability. These data support the life-history-oxidative stress hypothesis in a capitalbreeding mammal and suggest lactation is a period of heightened vulnerability to environmental factors that exacerbate cellular stress. Fitness consequences of stress may thus be accentuated during periods of rapid environmental change.

Lactation duration and lifetime progression to metabolic syndrome in women according to their history of gestational diabetes: a prospective longitudinal community-based cohort study

BackgroundDespite the many signs of progress in pharmacotherapies, metabolic syndrome (MetS) is one of the main public-health burdens worldwide. Our study aimed to compare the effect of breastfeeding (BF) in women with and without gestational diabetes mellitus (GDM) on MetS incidence.MethodsOf females who participated in the Tehran Lipid and glucose study, women who met our inclusion criteria were selected. The Cox proportional hazards regression model, with adjustment of potential confounders, was done to evaluate the relationship between duration of BF and incident of MetS in women with a GDM history compared to non-GDM.ResultsOut of 1176 women, there were 1001 non-GDM and 175 GDM. The median follow-up was 16.3 (11.9, 19.3) years. Results of the adjusted model illustrated that the total BF duration was negatively associated with MetS incidence risk (hazard ratio (HR) 0.98, 95% CI 0.98–0.99) in total participants indicating that per one-month increase of BF duration, the hazard of MetS reduced by 2%. The HR of MetS in Comparison between GDM and non-GDM women demonstrated significantly more reduced MetS incidence with a longer duration of exclusive BF (HR 0.93, 95% CI 0.88–0.98).ConclusionsOur findings illustrated the protective effect of BF, especially exclusive BF, on MetS incidence risk. BF is more effective in reducing the risk of MetS among women with a history of GDM than among women without such a history.

Abstract P324: Female Reproductive Factors and Risk of Type 2 Diabetes and Cardiovascular Disease Among Women With a History of Gestational Diabetes

Introduction: The link between gestational diabetes mellitus (GDM) and long-term risk of type 2 diabetes (T2D) and cardiovascular disease (CVD) is well established; however, risk factors underlying the progression of disease remain uncertain. Hypothesis: Female reproductive factors including ages at menarche, menopause, and first birth, number of live births, and surgically-induced menopause (uni- or bilateral oophorectomy or hysterectomy) are associated with higher risk of progression, while breastfeeding is associated with lower risk of progression from GDM to T2D/CVD. Methods: Participants in the Nurses’ Health Study II reported reproductive history at cohort baseline and over follow-up, including 5346 women with a history of GDM. Self-reported incident T2D or CVD (myocardial infarction, coronary revascularization or stroke) were confirmed via questionnaire or medical records. We estimated the hazard ratios (HR [95%]) across quintiles of each reproductive factor with incident T2D and CVD using Cox models adjusting for age, race/ethnicity, smoking, BMI at 18 years, physical activity, family history of T2D or CVD, alcohol intake, menopausal status, aspirin use, and Alternate Healthy Eating Index. Results: We documented 988 incident T2D and 149 CVD cases over 25 years of follow-up. In adjusted models, higher total lactation duration was associated with lower risk of T2D (5 categories: 0, 1-6, 7-12, 13-24, &gt;24 months, p for trend=0.01; highest vs. lowest category: HR 0.77 [95%CI: 0.60, 0.98]) and CVD (p for trend=0.03, HR 0.39 [95%CI: 0.19, 0.80]). Early age at menarche was linearly associated with higher risk of T2D (5 categories: ≤11, 12, 13, 14, &gt;14 y: p for trend &lt;0.0001), lowest (≤11 y) vs. reference (13 y) category: HR 1.28 [95%CI: 1.06, 1.53], while no trend could be observed for CVD outcomes (p for trend=0.48). Higher age at 1 st birth was associated with lower CVD risk (5 categories: &lt;23, 23-25 [reference], 26-29, 30-34, ≥35 y, p for trend=0.001; highest vs reference category: HR 0.17 [95%CI: 0.05, 0.57]), but not T2D). Compared with natural menopause, surgically induced menopause was associated with higher T2D risk: 1.32 (1.00, 1.73). Number of live births and age at menopause were not associated with T2D or CVD among women with GDM history. Conclusions: Breastfeeding was associated with lower T2D and CVD risks among women with GDM history, suggesting some shared risk factors or etiologies across reproductive lifespan and long-term cardiometabolic health. Ages at menarche and 1 st birth showed differential associations with T2D and CVD.

Assessment of influence of duration of the service period on the milk yield of cows

The Ural type of the Russian Black-and-White mottled breed features high rates of milk yield, good suitability for industrial milking technology, but the duration of their productive longevity is 2.4–2.6 lactations only. The decline in productive longevity is associated, in particular, with qualities of reproductive system. As a result of the conducted researches, it was found that due to elongation of lactation (over 305 days), more milk was obtained by 847–890 kg, or by 9.5–10.0%. At the same time, there is a decrease in MFF and MFP in milk for 305 days of lactation: by 0.01–0.02% for fat and by 0.02% for protein. The highest average daily milk yield was recorded in lactation duration of 305 days. The daughters of all assessed servicing bulls had the same service period of 132–134 days. It is 52–54 days higher than optimal indicators, or by 65–68%. The fertility index of cows exceeds 48%, so we can say that the fertility of cows is good. The fertility potential of the livestock is good and decrease of service period duration will increase the efficiency of dairy cattle breeding in the farm.

Assessment of endocrine disrupting chemicals in breast milk: Association with dietary habits and duration of lactation

The present study was aimed to assess infant safety associated with the presence of persistent organochlorine pesticides (OCPs) in breast milk, a possible route of transfer of endocrine–disrupting chemicals to newborns in North India. Colostrum and breast milk samples (n = 130) were collected at different stages of lactation. Pesticides analysis was performed using gas chromatography mass spectrometry (GC–MS). We observed that of all the samples analysed, OCPs concentration was higher in breast milk than in colostrum, suggesting pesticides contamination increases over lactation period. As far as OCPs are concerned, dieldrin [1196.64 ± 673.75 ng/g lipid weight (lw)], and β-HCH [1107.78 ± 1301.72 ng/g lw], were the predominant OCPs, followed by aldrin [977.09 ± 707.69 ng/g lw], α-HCH [948.04 ± 476.65 ng/g lw] and 1,1′-(2,2-Dichloroethene-1,1-diyl)bis(4-chlorobenzene) (p,p’DDE) [790.11 ± 399.35 ng/g lw]. The association between OCPs levels and women dietary habits were also explored, and all the OCPs were grouped and compared to each other by consumption level of fish, meat, sea foods, eggs, and dairy products. We found that women consuming non vegetarian food, like fish and meat, were exposed 3.5 times more to OCPs than women consuming vegetarian food. In addition, we also observed that factors like mother's age was positively (<0.005 - <0.001) correlated while gestational age and infant birth weight were negatively (<0.005) associated with the levels of OCPs in colostrum and breast milk, respectively. Unfortunately, neither any standards nor guidelines are available for the use of pesticides, therefore, it is suggested that careless use of OCPs should be checked and suitable remedial measures be taken to decrease human contamination. Moreover, further studies are warranted to elucidate relationship between pesticide residues in breast milk and the maternal and child health.

Productivity of Ukrainian black-spotted dairy cows depending on calving season and duration of lactation

Productivity of Ukrainian black-spotted dairy cows depending on calving season and duration of lactation

Estimating reproductive costs in marine mammal bioenergetic models: a review of current knowledge and data availability.

Reproductive costs represent a significant proportion of a mammalian female's energy budget. Estimates of reproductive costs are needed for understanding how alterations to energy budgets, such as those from environmental variation or human activities, impact maternal body condition, vital rates and population dynamics. Such questions are increasingly important for marine mammals, as many populations are faced with rapidly changing and increasingly disturbed environments. Here we review the different energetic costs that marine mammals incur during gestation and lactation and how those costs are typically estimated in bioenergetic models. We compiled data availability on key model parameters for each species across all six marine mammal taxonomic groups (mysticetes, odontocetes, pinnipeds, sirenians, mustelids and ursids). Pinnipeds were the best-represented group regarding data availability, including estimates of milk intake, milk composition, lactation duration, birth mass, body composition at birth and growth. There were still considerable data gaps, particularly for polar species, and good data were only available across all parameters in 45% of pinniped species. Cetaceans and sirenians were comparatively data-poor, with some species having little or no data for any parameters, particularly beaked whales. Even for species with moderate data coverage, many parameter estimates were tentative or based on indirect approaches, necessitating reevaluation of these estimates. We discuss mechanisms and factors that affect maternal energy investment or prey requirements during reproduction, such as prey supplementation by offspring, metabolic compensation, environmental conditions and maternal characteristics. Filling the existing data gaps highlighted in this review, particularly for parameters that are influential on bioenergetic model outputs, will help refine reproductive costs estimated from bioenergetic models and better address how and when energy imbalances are likely to affect marine mammal populations.

THE PRODUCTIVITY OF THE FIRST CALVING COWS OF DIFFERENT CONDITIONS GROWING AND HOUSING

Introduction. The purpose of the work was to study the influence of different conditions of rearing and housing of the first calving cows on their productivity, reproductive capacity and stayability during lactation at the current stage of breeding. Materials and methods of research. The work was carried out based on the data of four breeding plants for the breeding of Ukrainian black and white dairy cows. The data of 3.610 first calving cows that calved during the last six years were analyzed. Statistical processing of the obtained data was carried out by the method of two-factor variance analysis using computer programs. During the analysis, the data were divided by the age of first fertilization and the average daily gain before fertilization. Only animals with a duration of lactation of more than 200 days were selected to determine productivity indicators for lactation. The stayability was determined for the first 10 months of lactation. In determining the probability of abortion and stillbirth, calvings with stillborn calves and abortions after which lactation began are taken into account. Research results. It was established that the live weight of first calving cows, regardless of the housing, increased proportionally to the intensity of their growing. In stall housing, the live weight of first servis that were fertilized at different ages had no significant differences, while in free stall housing, the first calving cows that were inseminated before the age of 470 days had an advantage of 12–19 kg. In terms of milk yield for 305 days of lactation, the first calving cow that were kept tethered and were fertilized at an earlier age exceeded the animals of other groups by 29–148 kg of milk, and those kept without tethering by 564–989 kg. Intensively reared animals produced 244–539 kg of milk more when tethered, and when tethered, this difference was significantly greater and amounted to 530–1081 kg, compared to first calving cow with an increase of less than 800 g. A reading has been established for the trend of increasing the milk yields from the changes in the first fertilization. The intensity of the growth of the heifers before the flooding also has a positive impact on their day milk yield. The probability of unsuccessful calving does not depend on the age of the first insemination in stall housing, but in free housing, animals that were inseminated before 470 days of age had 36–46% more unfavorable results with calving than those that were inseminated in older age The probability of abortion and the birth of a dead calf during stall housing heifers with different intensities of growing before fertilization also had no significant differences, and during free housing heifers with an average daily gain of more than 800 g had 7–9 more cases of unsuccessful calving, calculated on 100 animal compared to heifers with a lower intensity of growing. Conclusions. Increasing the intensity of raising heifers and reducing the age of first insemination contribute to increasing their productivity. It is necessary to carry out constant monitoring of repair youngsters for fatness and to prevent obesity. It leads to a decrease in reproductive capacity, unfavorable calving and, as a result, an increase in the probability of culling in the first lactation, especially in in free housing.

The influence of prey availability on behavioral decisions and reproductive success of a central-place forager during lactation

Marine central-place foragers are increasingly faced with altered prey landscapes, necessitating predictions of the impact of such changes on behavior, reproductive success, and population dynamics. We used state-dependent behavioral life history theory implemented via Stochastic Dynamic Programming (SDP) to explore the influence of changes in prey distribution and energy gain from foraging on the behavior and reproductive success of a central place forager during lactation. Our work is motivated by northern fur seals (Callorhinus ursinus) because of the ongoing population decline of the Eastern Pacific stock and projected declines in biomass of walleye pollock (Gadus chalcogrammus), a key fur seal prey species in the eastern Bering Sea. We also explored how changes in female and pup metabolic rates, body size, and lactation duration affected model output to provide insight into traits that might experience selective pressure in response to reductions in prey availability. Simulated females adopted a central-place foraging strategy after an initial extended period spent on land (4.7–8.3 days). Trip durations increased as the high energy prey patch moved farther from land or when the energy gain from foraging decreased. Increases in trip duration adversely affected pup growth rates and wean mass despite attempts to compensate by increasing land durations. Metabolic rate changes had the largest impacts on pup wean mass, with reductions in a pup’s metabolic rate allowing females to successfully forage at distances of 600+ km from land for up to 15+ days. Our results indicate that without physiological adaptations, a rookery is unlikely to be viable if the primary foraging grounds are 400 km or farther from the rookery. To achieve pup growth rates characteristic of a population experiencing rapid growth, model results indicate the primary foraging grounds need to be <150 km from the rookery.

The Relationship Between Leptin Gene Polymorphism and Milk Yield Traits in Simmental and Brown Swiss Cattle

This study was performed to determine the genotype and allele frequencies and the association between the leptin gene Sau3AI polymorphism and some performance traits in Simmental (n=60) and Brown Swiss (n=62) cattle in the province of Erzurum, Türkiye. Considering the allele frequencies in the population, the frequency of the A allele was 0.87 and the frequency of the B allele was 0.13 in Simmental cattle, and the frequency of the A allele was 0.94 and the frequency of the B allele was 0.06 in Brown Swiss cattle. According to the analysis conducted in the Simmental breed, the general averages were found to be 5422.4 ± 1901.74 kg for actual milk yield, 5626.6 ± 1475.85 kg for 305-day milk yield, 298.7 ± 84.80 days for lactation duration, and 18.5 ± 4.84 kg for daily milk yield. As a result of the analysis in the Brown Swiss breed, the general averages were 3917.8 ± 1584.38 kg for actual milk yield, 4614.3 ± 982.62 kg for 305-day milk yield, 254.9 ± 99.88 days for lactation duration, and 16.0 ± 3.82 kg for daily milk yield. According to the statistical analysis results, the impact of genotype on milk yield traits was insignificant in Simmental and Brown Swiss cattle.

The introduction of complementary foods in children. Practical questions

The article presents data characterizing the features and timing of the introduction of complementary foods to children of the first year of life living in the Belgorod region. The purpose of the study was to study the features of feeding children in the first year of life living in the Belgorod region, and to evaluate the success of the implementation of the “National Program for Optimizing the Feeding of Children in the First Year of Life” in pediatric practice. Methods. Subject to the principles of voluntariness and confidentiality, interviews were conducted with 348 women with young children (the first two years of life) born at 38-41 weeks of gestation with an Apgar score of at least 8 points. To conduct the study, a questionnaire was developed that allows retrospectively assessing the duration of breastfeeding and the timing of the introduction of complementary foods. Results. When assessing the nutrition of children in the first year of life, the following problems were identified: early termination of breastfeeding (before the child reaches the age of 3 months) - in 29.8% of cases, violation of the timing of the introduction of complementary foods (earlier than 4 months and later than 6 months - 22% children), the rules for the introduction of complementary foods (52.7%) and the range of selected products. The main source of information for young parents about complementary foods, the timing and methods of its introduction were: in 60.1% - medical workers, in 12.9% - the opinion and advice of relatives, friends and acquaintances, in 3.2% - the exchange of information with other parents with children of the same age, in 18.1% - information contained on the Internet. Research results. The results of the study show the need for further work on the active implementation of the existing recommendations in the practice of pediatricians, aimed at implementing the principles of breastfeeding support to increase the duration of lactation, on the timeliness of the introduction of complementary foods, the implementation of the rules for the introduction and selection of the range of introduced food products.

Changes in Polychlorinated Biphenyl Residues in Milk during Lactation: Levels of Contamination, Influencing Factors, and Infant Risk Assessment.

Given the importance of breastfeeding infants, the contamination of human milk is a significant public concern. The aim of this study was to assess the contamination of human milk with dioxin-like PCBs (dl-PCBs) and non-dioxin-like PCBs (ndl-PCBs) in relation to the duration of lactation and other influencing factors, especially the frequency of the consumption of selected foods during pregnancy. Based on this, the health risk to infants was assessed and compared to the tolerable daily intake (TDI). PCB determinations were performed using gas chromatography/mass spectrometry. The ∑ndl-PCB content ranged from 0.008 to 0.897 ng/g w.w., at an average of 0.552 ng/g wet weight, which was 55% of the maximum level according to the EU guidelines for foods for infants and young children. The toxic equivalent (TEQ) was in the range of 0.033-5.67 pg-TEQ/g w.w. The content of non-ortho, mono-ortho, and ndl-PCBs in human milk decreased the longer lactation continued. Moreover, when pregnant women smoked tobacco, this correlated significantly with increases in the concentrations of PCB congeners 156, 118, and 189 in human milk. The human milk contents of PCB congeners 77, 81, 186, 118, and 189 were strongly positively correlated with the amount of fish consumed. The content of stable congeners PCB 135 and PCB 153 increased with age.