Association between seasonal changes in fatty-acid composition, expression of VLDL receptor and bovine sperm quality.

Reduced reproductive performance of dairy cows during the summer is often associated with elevated temperature. Semen collected and cryopreserved during the summer may be of low quality and might contribute to the compromised fertility of dairy cows during this season. The present study examined the association between seasonality, semen quality and its potential to survive cryopreservation. A comparison between semen collected during the summer (July to August) and that collected during the winter (November to December) revealed the summer semen to be inferior, as reflected by low motility and high mortality of sperm. Furthermore, samples that were defined as good quality had changes in lipid concentration and fatty-acid composition in both the seminal plasma and cell compartment. In particular, semen collected during the summer had reduced levels of polyunsaturated arachidonic acid (20:4; P<0.05) and decreased levels of linoleic acid (18:2; P<0.05) in the cell compartment; corresponding reductions in cholesterol (P<0.06) and fatty-acid concentrations (P<0.001) were detected in seminal plasma of semen collected during the summer. In addition, we provided the first evidence for the existence of a very-low-density lipoprotein receptor (VLDLr) in bovine sperm, suggesting a mechanism for sperm utilization of extracellular lipids. Interestingly, the expression of VLDLr was three-fold greater in samples collected during the winter than in those collected in the summer (P<0.01) and was negatively associated with saturated fatty-acid concentration (P<0.018) but not with that of cholesterol. An opposite pattern was noted for samples obtained during the summer; mRNA expression of VLDLr was negatively associated with cholesterol concentration (P<0.01) but not with that of saturated fatty acids. Such modifications associated with extracellular lipid utilization and fatty-acid composition might explain, in part, the reduced quality of summer semen.

Summer heat stress alters the mRNA expression of selective-uptake and endocytotic receptors in bovine ovarian cells.

Summer heat stress (HS) is a major factor in decreased reproductive performance in high-producing dairy cattle, possibly by affecting the steroidogenic capacity of ovarian follicles and ovarian follicular dynamics. In the present study, mRNA expression of cholesterol receptors was determined in bovine ovarian cells. Two endocytotic receptors (very-low-density lipoprotein receptor (VLDLr) and low-density lipoprotein receptor (LDLr)), and two selective-uptake receptors (scavenger receptor class B type 1 receptor (SRB1) and the lipoprotein-receptor-related protein 8 (LRP8)) were evaluated. Ovarian follicles in four diameter categories were evaluated from cows under non-heat stress (NHS) and HS conditions. As follicle size increased, expression of mRNA in NHS cows increased for the selective-uptake receptors, SRB1 and LRP8, and decreased (P<0.004) for the endocytotic receptors, LDLr and VLDLr. In contrast, in HS cows, mRNA expression did not significantly change (with increasing follicle diameter) for either receptor type. With increasing follicle diameter, cholesterol and fatty acid concentrations in the follicular fluid did not change in HS cows, whereas in NHS cows, cholesterol increased (P<0.008) and fatty acid decreased (P<0.0001). These changes paralleled those in the different lipoprotein fractions in the follicular fluid. In follicles from HS cows, the altered mRNA expression patterns for the endocytotic and selective-uptake receptors caused changes in the regulation of cholesterol supply at critical stages of folliculogenesis, which may play a role in the low turnover rates of ovarian follicles during the summer.

Temporal folate status during lactation in mares and growth in foals.

OBJECTIVE: To identify changes in folate status of mares and foals during lactation and growth, respectively. ANIMALS: 20 Thoroughbred mares and foals. PROCEDURES: Pregnant mares, and following foaling the same mares with their foals, were maintained on mixed grass-legume pasture and fed either a traditional dietary supplement rich in sugar and starch (SS) or a dietary supplement high in fat and fiber (FF). Blood samples were collected monthly from mares and foals up to 6 months after foaling. Total folate concentration in feed and forage was determined. Analyses of plasma folate, RBC folate, plasma homocysteine (HCY), and milk folate concentrations were performed. RESULTS: Mare plasma folate concentrations declined moderately during 6 months of lactation. Mare RBC folate concentrations initially increased after foaling up to 3 months but declined toward the end of the study. Plasma HCY concentration was higher for mares fed the SS supplement, compared with mares fed the FF supplement from foaling to 6 months of lactation. Milk folate concentrations decreased during the first 3 months and then increased. Foal plasma folate initially declined but then increased. Stable concentrations of RBC folate were observed in foals. Plasma HCY concentrations in foals were unaffected by growth during the last 5 months. References range values for plasma folate, RBC folate, milk folate, and plasma HCY concentrations in healthy lactational mares and young growing foals were determined. CONCLUSIONS AND CLINICAL RELEVANCE: Folate status was not impaired in lactating mares and growing foals under the conditions in our study. It appears that folate supplementation is not necessary.

Impaired immune responses in broiler hatchling hindgut following delayed access to feed.

One of the key stimulators of intestinal development in the chick is physical exposure to feed, while feed withholding delays the onset of gut development. A delay of 24-72 h in onset of feeding is quite common in the poultry industry due to variation in hatching time and hatchery treatments. As intestinal development occurs in concert with the development of the gut associated lymphoid tissue (GALT), we investigated the effects of short term feed withholding on development of GALT in broiler hatchlings. GALT activity was determined by antibody production (systemic and locally in the gut), distribution of B and T lymphocytes in the gut, expression of lymphocyte specific genes, and distribution of B and T lymphocytes in the cloacal bursa. Our findings show that while development of GALT in the foregut (duodenum, jejunum, ileum) was only slightly and temporarily impeded by feed withholding, GALT activity in the hindgut and the gut-related cloacal bursa was significantly delayed during the first 2 weeks of life: Systemic and intestinal antibody responses following rectal immunization to antigen were lower, colonization of the hindgut (cecum and colon) by T and B lymphocytes was delayed, as well as the expression of chIL-2 mRNA in hindgut T lymphocytes. We also found that the increase of B and T population size in the cloacal bursa was delayed with time. Full recovery occurred from 2 weeks of age. The 2-week vulnerable period should be seriously considered in circumstances where hatchlings are in transit for extended periods from hatcheries to farms.

Expression of mRNA of lipoprotein receptor related protein 8, low density lipoprotein receptor, and very low density lipoprotein receptor in bovine ovarian cells during follicular development and corpus luteum formation and regression.

Lipoproteins in the plasma are the major source of cholesterol obtained by the ovarian theca and granulosa cells for steroidogenesis. In this study, we have identified mRNA expression in bovine theca and granulosa cells of two lipoprotein receptors, low density lipoprotein receptor (LDLr) and very low density lipoprotein receptor (VLDLr) in granulosa cells from small antral follicles through preovulatory follicles and in theca cells from large and medium sized antral follicles. In the corpus luteum (CL) both these receptors were found in the developing and differentiating stages whereas only mRNA for VLDLr was detected in the regression stage. This study also described for the first time, the presence of lipoprotein receptor related protein (LRP8) in granulosa cells from small antral follicles through preovulatory follicles and in theca cells from large and medium sized antral follicles. This may indicate a role of LRP8 in cholesterol delivery to steriodogenic cells. LRP8 was not detected in any of the CL stages. The roles of the LDLr superfamily in lipid transport to ovarian cells and its participation in follicular and CL development and regression is discussed.

Lipid transport in the developing bovine follicle: messenger RNA expression increases for selective uptake receptors and decreases for endocytosis receptors.

Differences in rates of steroid production and secretion will, eventually, determine the developmental rates of ovarian follicles. The major supply of cholesterol, the precursor for steroid and androgen biosynthesis, to ovarian cells is from circulating lipoproteins via membrane receptors from the low density lipoprotein receptor (LDL) superfamily. This occurs by either endocytosis, which has been described for very low density lipoprotein receptors (VLDLr), for LDL receptors (LDLr), and by the selective uptake pathway described for the scavenger receptor class B type 1 receptor (SRB1) and the recently described ovarian receptor, lipoprotein receptor-related protein 8 (LRP8). In this study, the mRNA expression of these four cholesterol receptors in bovine ovarian cells was determined at different stages of follicular development. In small antral follicles, mRNA expression of the endocytosis receptors was higher than in large antral follicles. Expression of LRP8 mRNA increased linearly with follicular size together with an increase in LDL, VLDL, and cholesterol concentrations in the follicular fluid. SRB1 mRNA expression tended to increase with follicular diameter. Because different mRNA expression patterns were found for the two types of receptor, this may imply different regulation of cholesterol supply at different stages of follicular development. Accumulation of LDL and VLDL particles in the follicular fluid of large antral follicles may enhance cholesterol availability for the intense steroidogenic activity that is essential at these stages.

Mucin dynamics in the chick small intestine are altered by starvation.

The absorptive surface of the small intestine is covered by a layer of mucus secreted by goblet cells. The secreted mucins and thickness of the adherent layer influence nutrient digestion and absorption processes as well as the functionality of the mucosa. In this study, methods for the analysis of mucin synthesis and dynamics in the chick small intestine are described. A fragment of chicken mucin cDNA was isolated and characterized; this fraction had 60% homology to human mucin MUC-5AC. The thickness of the mucus adherent layer and the relative amounts of mucin glycoprotein and mRNA were also examined in the small intestines of control and starved chicks. Relative amounts of intestinal mucin mRNA and protein increased in the duodenum and jejunum of starved chicks, and mucus adherent layer thickness decreased throughout the small intestine. In starved chicks, higher mRNA expression and protein concentrations with lower amounts of adherent mucus may be related to a higher rate of degradation of the mucus layer, a lower rate of mucus secretion, or an altered rate of mucin turnover. It thus appears that starvation alters mucus dynamics in the small intestine, and this may affect intestinal digestive function and defense.

Maternal antibodies block induction of oral tolerance in newly hatched chicks.

Oral antigens administered to newly hatched chicks induce oral tolerance. Some of the antigens encountered via the gut during this period are pathogen-derived, and should not be tolerogenic. As chicks are protected in early life by maternal antibodies, we assumed that the same antibodies also served to prevent tolerance by blocking the relevant antigen. We used bovine serum albumin (BSA) as a model antigen, and initially showed that tolerance was invariably generated in chicks younger than 3 days of age. We then showed that tolerance and its prevention were due to circulatory BSA: intravenous BSA induced tolerance, BSA was present in serum of previously fed chicks, and tolerance was completely blocked in chicks containing high levels of maternal anti-BSA. These findings indicate that tolerance in the young chick is probably generated in central lymphoid organs, and that maternal antibodies block access of antigen to these organs, thereby preserving immune competence.

Ontogeny of brush border carbohydrate digestion and uptake in the chick.

Ingestion of carbohydrates from the small intestine is the major route of energy supply in animals. In mammals these functions develop both pre- and postnatally and are coordinated for the sucking period. In birds, the physiological requirements are different and hatchlings ingest diets rich in complex carbohydrates soon after hatching. The present study examined the ontogeny of intestinal carbohydrate uptake in the chicken. The expression of mRNA for a brush border enzyme, sucrase-isomaltase (SI), which is critical in disaccharide digestion, was determined, together with that of the Na-glucose transporter (SGLT)-1, which is the major apical glucose transporter, In addition, the homeobox gene cdx, which is involved in inducing SI expression in mammals was examined. It was found that the expression of cdxA mRNA and cdxA protein increased from day 15 of incubation until hatch, after which further changes were small. CdxA protein was shown to bind to the promoter region of SI in the chick indicating that cdxA is similar to the mammalian cdx2. The mRNA of SI was observed at 15 d incubation, increased from 17 d of incubation to a peak on day 19, decreased at hatch and had a further peak of expression 2 d post-hatch. In contrast, the mRNA of SGLT-1 was not detected until 19 d of incubation when a major peak of expression was observed followed by a decrease to low levels at hatch and small increases post-hatch. It appears that both SI and SGLT-1 mRNA are expressed before hatch in the chick, but the ontogeny of expression is controlled by different mechanisms.

Na+/glucose co-transporter abundance and activity in the small intestine of lambs: enhancement by abomasal infusion of casein.

The purpose of the present study was to determine the effect of abomasal casein infusion on glucose uptake and abundance of the Na+/glucose co-transporter (SGLT1) 1 in the ovine small intestine. Lambs (body weight 35 (sem 1.0) kg) were surgically fitted with abomasal infusion catheters and were fed diets containing equal portions of wheat hay and cracked maize. Lambs were infused with either 500 g water/d or with 500 g water containing 35 g casein/d. The infusion period lasted 10 d, after which lambs were killed, exsanguinated and eviscerated. Brush border membrane vesicles (BBMV) were prepared using mucosa from different small intestinal regions. Intake and total tract digestibility of nutrients were similar between treatments and averaged 1134, 1142 and 486 g/d and 67, 70, and 94 % for DM, organic matter and non-structural carbohydrates respectively. Crude protein (Nx6.25) digestibility was 15 % greater in the casein-infused than control lambs. Glucose uptake to BBMV ranged from 101 to 337 pmol/mg protein per s along the small intestine and was greatest in the mid-section of the small intestine. In the mid-jejunum, glucose uptake was greater (P<0.07) in lambs infused with casein and averaged 120 pmol/mg protein per s compared with 68 pmol/mg protein per s in the control group. SGLT1 affinity was similar between treatments and averaged 104 microm in the different segments of the small intestine of lambs. However, lambs infused with casein exhibited similar values along the small intestine and affinity averaged 106 microm, while in the control group a greater affinity (85 microm) was measured in the mid-jejunum. SGLT1 protein abundance was correlated with glucose uptake in the BBMV in the casein-treated lambs, but not in the control group. These results suggest that glucose uptake along the small intestine of lambs is influenced by casein or its derivatives in the small intestine via SGLT1 affinity and activity at the brush border membrane, and that SGLT1 activity may be regulated by post-translational events affected by amino acids and peptides.

Early posthatch feeding stimulates satellite cell proliferation and skeletal muscle growth in turkey poults.

The effect of early posthatch feeding on skeletal muscle growth and satellite cell myogenesis was studied in turkey poults. Poults were either fed immediately posthatch or food-deprived for the first 48 h and then refed for the rest of the experiment. Body and breast muscle weights were lower in the starved poults than in fed controls throughout the experiment (P < 0.05). Cultures of breast muscle satellite cells revealed significantly higher DNA synthesis in the fed group than in the starved group as early as d 1 (P < 0.05). These levels continued to rise, reaching approximately 500-fold those of feed-deprived poults on d 4. In the latter group, thymidine incorporation peaked only on d 6, and then declined. Thereafter, it decreased to the same levels as those in the fed group. Satellite cell number per gram muscle increased until d 4, and was higher in the fed group than in the starved group (P < 0.05). Pax7 levels in cell cultures derived from the fed group were markedly higher than in the starved group on d 2 (P < 0.05). Myogenin levels in both culture and muscle were higher in the fed than in the starved groups until d 4 (P < 0.05). Phosphorylation of the survival factor Akt and cyclin-dependent kinase inhibitor p21 levels were higher in cells derived from the fed group relative to those from the starved group 48 h posthatch (P < 0.05). Similarly, Akt phosphorylation and insulin-like growth factor I (IGF-I) levels were significantly higher in the muscles of the fed group (P < 0.05). Together, these results suggest that immediate posthatch feeding of poults is critical for satellite cell survival and myogenesis probably via IGF-I.

Ethiopian-born and native Israeli school children have different growth patterns.

OBJECTIVE: Nutrition status of preschool children in Azezo, North West Ethiopia, and Ethiopian-born and native Israeli children aged 7 to 11 y and 12 to 15 y was studied. The aim of the study was to determine the growth patterns of immigrant children after changes in their nutritional habits. METHODS: The Ethiopian-born and native school children were recruited from a caravan-dwelling site and a boarding school and from a town adjacent to the caravan site and a boarding school, respectively. RESULTS: Weight for age was lower than -2 standard deviations of the Z score in 40.5%, 55.6%, 31.9%, and 61% of children aged 1 to 24, 25 to 36, 37 to 48, and 49 to 60 mo, respectively. Similarly, 18.9%, 59.3%, 39.1%, and 19.5% of children aged 1 to 24, 25 to 36, 37 to 48, and 49 to 60 mo had a height for age lower than -2 standard deviations of the Z score. The Ethiopian-born boys aged 7 to 11 y had lower body weight (P < 0.03), mean arm muscle circumference, plasma transthyretin and magnesium (P < 0.0001), and higher triceps skinfold thickness (P < 0.01) compared with the controls. Similarly, the Ethiopian-born girls had lower body weight (P < 0.006), weight-to-height ratio (P < 0.02), mean arm muscle circumference and plasma transthyretin, calcium, and magnesium (P < 0.0001), and higher triceps skinfold thickness (P < 0.0001) than their Israeli counterparts. Weight, weight-to-height ratio, mean arm muscle circumference, plasma calcium and magnesium (P < 0.0001), and transthyretin (P < 0.01) were lower and triceps skinfold thickness (P < 0.0001) was higher in the Ethiopian-born boarding school children than in the native Israelis of the same age range. CONCLUSIONS: The Azezo study confirmed that malnutrition-induced developmental impairment in preschool children is a major problem in Ethiopia. It is a manifestation of a rural economic and educational poverty and cannot be eradicated by palliative short-term nutritional programs. Although ethnicity and prenatal and postnatal malnutrition may have contributed, an insufficiency or imbalance of vital nutrients appeared to be the determinant factor for the lower relative growth of the Ethiopian-born children. The children from Ethiopia may have a propensity to avoid certain foods because of digestive intolerance or early childhood dietary habituation. Parental financial constraint may have been a factor in the younger group. These findings have implications for nutrition and welfare policies for children emigrating from developing countries.

Retinol concentration in maternal and cord serum: its relation to birth weight in healthy mother-infant pairs.

BACKGROUND: Vitamin A is an essential micronutrient for the development and growth of the fetus. The objective of this study was to identify a possible association between low serum retinol and birth weight in healthy mother-infant pairs in Southern Israel. A secondary objective was to examine ethnic differences in maternal and cord serum retinol. METHODS: Serum retinol was measured at delivery from pairs of healthy mothers and healthy mature newborns. RESULTS: Of the 313 mother-infant pairs studied, 56% were Jews and 44% Bedouins. The proportion of infants with birth weight of 2500-2999 g was greater among mothers with lower serum retinol (<0.7 micromol/l) compared to mothers with normal serum retinol (> or =0.7 micromol/l) (p<0.001). Cord retinol <0.7 micromol/l was more frequent in infants with birth weight 2500-2990 g compared to infants with birth weight > or =3000 g (p=0.006). Using a split model and stepwise multiple regression analysis, infant's birth weight was significantly influenced by cord retinol concentration in infants born to mothers with low serum retinol; gestational age and cord retinol alone explained 27% of the variability of birth weight in this group. A higher proportion of Bedouin than Jewish infants had serum retinol <0.7 and <0.35 micromol/l (both p<0.001). CONCLUSION: Low cord and maternal serum retinol may reflect poor vitamin A status of the newborn and the mother, which in turn may affect fetal growth.

Establishment of immune competence in the avian GALT during the immediate post-hatch period.

Population dynamics of intestinal lymphocytes and the temporal development of lymphocyte functions were studied in broiler chicks during the first 2 weeks post-hatch. This period is of major immunological importance as the chick is immediately exposed to environmental antigens and pathogens. We show that the gut-associated lymphoid tissue contains functionally immature T and B lymphocytes at hatch, and that function is attained during the first 2 weeks of life as demonstrated by mRNA expression of both ChIL-2 and ChIFNgamma. Functional maturation occurred in two stages: the first-during the first week post-hatch, and the second during the second week, which was also accompanied by an increase in lymphocyte population, as determined by expression of antigen receptor genes. Evidence is presented to show that in the intestinal milieu cellular immune responses mature earlier, and are a prerequisite for humoral responses. Hence, the lack of antibody response in young chicks is primarily due to immaturity of T lymphocytes.

Effect of polyunsaturated fatty acid supplementation on biophysical parameters and chilling sensitivity of ewe oocytes.

Fat supplementation in the diet influences reproductive performance of lactating ruminants. Changes in the fat supply alter fatty acid composition and this can affect physical properties of cell membranes. This study examined the effect of rumen bypass polyunsaturated fatty acid (PUFA) supplementation on oocyte quality, chilling sensitivity, and lipid phase transition in oocytes of the sheep. Ewes were fed a diet supplemented with calcium soaps of fish oil for 13 weeks. More follicles and oocytes were found in the ovaries of ewes supplemented with PUFA than in control ewes. The number of high-quality oocytes was higher in ewes fed PUFA than in control ewes (74.3 and 57.0%, P < 0.05, respectively). Evaluation of phospholipid fatty acid composition indicated that PUFA were present in small proportions in oocytes, and eicosapentaenoic acid and docosahexaenoic acid were absent. Supplementation with PUFA increased the proportion of long chain unsaturated fatty acid in the plasma and cumulus cells phospholipids by 7.4 and 12.7%, respectively (P < 0.05). Integrity of oocyte membranes following chilling (16 degrees C, 15 min) was improved by PUFA supplementation increasing from 62.5 to 90.0% (P < 0.05). Due to changes in the oocyte's fatty acid profile, physical properties of the membrane were changed and the midpoint temperature of lipid transition reduced by 11 degrees C. These results suggest that supplementation of rumen bypass PUFA to ruminant diets can change fatty acid composition of follicle components and influence parameters such as number and quality of oocytes and their chilling resistance.