Effect of beta-carotene and vitamin A on progesterone production by bovine luteal cells

The relationship between concentrations of plasma vitamin A and c-carotene and corpora lutea was studied using 52 Holstein cows. Bovine luteinizing hormone was added to incubation tubes in doses of 0, 10, or 100 ng/ml. Regression of progesterone secretion by luteal cells in vitro on plasma beta-carotene was positive and significant for corpora lutea collected during the winter months when plasma beta-carotene was low. The two were unrelated during the summer months when beta-carotene was higher. Similar regressions for in vitro progesterone production and vitamin A were not significant in either season. These results suggest that in vivo beta-carotene status is related to bovine luteal function in vitro.     

Bovine vitamin A and beta-carotene intake and lactational status. 1. Responsiveness of peripheral blood polymorphonuclear leukocytes to vitamin A and beta-carotene challenge in vitro

Dietary vitamin A and beta-carotene were assessed on their interaction with lactational status to influence neutrophil function in vitro. Cows were fed 1) 53,000 IU or 2) 213,000 IU vitamin A, or 3) 53,000 IU vitamin A plus 400 mg beta-carotene/cow per d from 6 wk before to 2 wk after dry off. Blood neutrophils were isolated the day of dry off and 2 wk after dry off and incubated with retinol, retinoic acid, or beta-carotene. Phagocytosis and kill of Staphylococcus aureus were measured. Across all treatments, kill was higher after dry off than before dry off. Phagocytosis tended to be lower after dry off than before in cows fed vitamin A only. In vitro, 10(-6) M beta-carotene stimulated phagocytosis after dry off and kill before dry off in cows fed vitamin A only. In general, retinol and retinoic acid suppressed phagocytosis but did not affect kill. Neutrophils from cows fed high amounts of vitamin A were more susceptible to in vitro suppression than those from cows fed adequate amounts of vitamin A. Therefore, vitamin A and beta-carotene supplementation interacts with lactational status to influence the responsiveness of bovine neutrophils to vitamin challenge in vitro.     

Bovine vitamin A and beta-carotene intake and lactational status. 2. Responsiveness of mitogen-stimulated peripheral blood lymphocytes to vitamin A and beta-carotene challenge in vitro

The interaction of dietary vitamin A and beta-carotene with lactational status on the in vitro proliferation of mitogen-induced peripheral blood lymphocytes was studied. Cows were fed (IU/cow per d) 1) 53,000 IU vitamin A, 2) 213,000 IU vitamin A, or 3) 53,000 IU vitamin A plus 400 mg beta-carotene from 6 wk before to 2 wk after dry off. Lymphocytes were incubated with retinol, retinoic acid, or beta-carotene. Concanavalin A-induced blastogenesis was inhibited by 10(-6) M retinol and 10(-8) M retinoic acid in cows fed 53,000 IU vitamin A before dry off. In contrast, 10(-7) M retinol and 10(-7) M retinoic acid stimulated Concanavalin A-induced blastogenesis for cows fed vitamin A plus beta-carotene before dry off. After dry off, retinol and retinoic acid did not affect Concanavalin A-induced blastogenesis in all treatment groups. In vitro, 10(-5) M beta-carotene inhibited Concanavalin A-induced blastogenesis before and after dry off in all treatment groups. Blastogenesis in the absence of mitogen stimulation or induced by lipopolysaccharide was inhibited by all vitamins before and after dry off in all treatment groups. These data indicate that vitamin A and beta-carotene supplementation interact with lactational status to influence the responsiveness of bovine blood lymphocytes to vitamin challenge in vitro.     

Peripartum changes of plasma and milk vitamin A and beta-carotene among dairy cows with or without mastitis

Over 12 mo we studied the relationship between peripartum concentrations of vitamin A and beta-carotene in blood plasma and milk of 93 Holsteins with or without subsequent mastitis. Blood was sampled daily from 7 days prepartum through 7 days postpartum and on alternate weeks through wk 10 of lactation. Milk samples were collected daily for 7 days postpartum and then biweekly for 10 wk. Somatic cell counts were on biweekly milk samples. Vitamin A and beta-carotene of blood plasma decreased rapidly prepartum to reach minimum concentrations at calving (vitamin A) or on day 4 to 6 postpartum (beta-carotene). Thereafter, both vitamin A and beta-carotene increased rapidly through 10 wk postpartum. Concentrations of vitamin A and beta-carotene in colostrum were higher than concentrations in milk. Cows with mastitis (somatic cells greater than 500,000 cells/ml milk) had lower vitamin A in blood plasma during days 0 to 7 and wk 2 and 4 postpartum than cows without mastitis. When data were analyzed with loge of somatic cell count as an independent regression variable, results were similar. In contrast to vitamin A, peripartum beta-carotene in blood plasma was higher among mastitic cows and was related to higher loge of somatic cell count. No significant difference was observed between mastitic and non-mastitic cows for vitamin A and beta-carotene in milk. Lower concentrations of plasma vitamin A and higher concentrations of beta-carotene during the immediate postpartum period were associated with higher milk somatic cell counts among dairy cows during lactation.     

Peripartum serum vitamin E, retinol, and beta-carotene in dairy cattle and their associations with disease

Peripartum decreases in serum concentrations of vitamins A and E may contribute to impaired immune function in dairy cows. The objectives of this study were to describe peripartum serum concentrations of alpha-tocopherol, beta-carotene, and retinol and their associations with disease risk. On 20 farms over 1 yr, blood samples were collected weekly from 1057 cows from 1 wk before expected calving until 1 wk postpartum. Serum concentrations of alpha-tocopherol, beta-carotene, and retinol, as well as several biochemical variables were measured. Their associations with the risk of retained placenta or clinical mastitis were modeled separately with logistic regression, and the factors associated with the concentration of each vitamin were modelled with mixed linear regression. Differences in vitamin concentrations between 2 batches of sera analyzed 6 mo apart required stratification of statistical analyses. Accounting for the effects of parity, season, and twins, an increase in alpha-tocopherol of 1 microg/mL in the last week prepartum reduced the risk of retained placenta by 20%, whereas serum nonesterified fatty acid concentration > or = 0.5 mEq/L tended to increase risk of retained placenta by 80%. In the last week prepartum, a 100 ng/mL increase in serum retinol was associated with a 60% decrease in the risk of early lactation clinical mastitis. There were significant positive associations of peripartum serum concentrations among each of alpha-tocopherol, beta-carotene, and retinol.     

Interrelationships between energy balance and postpartum reproductive function in dairy cattle

Genetic improvement of dairy cows has markedly increased milk yield over the last three decades. Increased production has been associated with reduced conception rates (66% in 1951 versus 40 to 50% since 1975). Because conception rate in dairy heifers has remained higher, the metabolic demands of higher production may be related to the decline in reproductive performance in cows. During early lactation, increasing dietary intake fails to keep pace with rising milk production. The resultant negative energy balance and rate of mobilization of body reserves appear directly related to the postpartum interval to first ovulation and lower conception rate. Delays in the onset of normal ovarian activity, thus limiting the number of estrous cycles before breeding, may account for the observed decrease in fertility. Negative energy balance probably acts similarly to undernutrition and may manifest in delayed ovarian activity by impinging on pulsatile secretion of LH. Lower availability of glucose and insulin may also decrease LH pulsatility or limit ovarian responsiveness to gonadotropins. Alternatively, release of endogenous opioids in association with increasing feed intake or other lactational hormone responses may provide neural or pituitary inhibition of the pulsatile LH production that is requisite for ovarian follicular development.     

First postpartum luteal function in dairy cows after ovulation induced by progestogen and gonadotropin-releasing hormone

The objective was to determine the effects of progestogen treatment on the lifespan of the first corpus luteum induced by GnRH in periparturient-milked cows. Dairy cows (n = 55) were assigned randomly following normal parturitions to receive either a progestogen implant (6 mg of norgestomet) or a blank implant (control) for 6 d beginning 2 to 5 d after calving. Fifty micrograms of GnRH were administered i.m. 72 h after implant removal to induce ovulation. Concentrations of LH and FSH in serum from 24 to 30 h and from 66 to 72 h after implant removal were similar among treatments. The magnitude of LH released after GnRH injection was higher in progestogen-treated cows (7.6 +/- .9 ng/ml) than in controls (5.3 +/- .9 ng/ml). Concentrations of estradiol in serum from the beginning of the implant period until 3 d after GnRH injection were higher in cows receiving progestogen (9.1 +/- 1.7 pg/ml) than in controls (5.6 +/- 1.7 pg/ml). The proportion of cows that responded to GnRH (elevated concentrations of progesterone in serum greater than .5 ng/ml within 3 to 5 d after injection) tended to be higher in cows receiving progestogen (24 of 28) than in control cows (19 of 27). By definition, interval to first ovulation after GnRH injection was shorter in cows responding to GnRH (3.8 +/- .5 d) than in those failing to respond (20.2 +/- .9 d).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of dietary vitamin A and beta-carotene on polymorphonuclear leukocyte and lymphocyte function in dairy cows during the early dry period

Vitamin A and beta-carotene improved mammary health in dairy cows around dry off. To define possible mechanisms, cows were fed 1) 53,000 IU vitamin A, 2) 213,000 IU vitamin A, or 3) 53,000 IU vitamin A plus 400 mg beta-carotene/cow per d (n = 10/treatment) from 6 wk before to 2 wk after dry off. Blood polymorphonuclear neutrophil function (phagocytosis, kill, and chemotaxis) and lymphocyte proliferation were measured at wk -6, 0 (dry off), and 2. Concentrations of vitamin A in serum did not differ across vitamin treatments. beta-Carotene in serum was elevated in cows fed beta-carotene. Treatment did not influence phagocytosis or kill. Kill ability increased after dry off in all treatment groups, but phagocytosis tended to decrease after dry off in cows fed vitamin A only. Lymphocyte blastogenesis stimulated by concanavalin A on wk 2 for cows fed 53,000 IU vitamin A but did not vary in the other two groups. Lipopolysaccharide-stimulated blastogenesis peaked at wk 0 and then decreased to pretreatment values by wk 2 in cows fed 213,000 IU vitamin A. These data indicate lymphocyte function is influenced by vitamin A supplementation and that beta-carotene supplementation seems to exert a stabilizing effect on neutrophil and lymphocyte function during the period around dry off.     

Progesterone responses to human chorionic gonadotropin in dairy cattle supplemented with beta-carotene

Twenty Holstein cows were assigned to one of four groups according to milk production and beta-carotene supplementation to evaluate effects of supplementation and milk production on reproductive performance and response of corpus luteum to human chorionic gonadotropin indicated by release of progesterone and secretion of luteinizing hormone in blood plasma. Cows were divided into groups of high and low production and divided further into beta-carotene supplemented and unsupplemented groups. Blood samples were taken 10 days postestrus at 10-min intervals from 1 h prior to injection of 5000 IU human chorionic gonadotropin until 5 h postinjection. Mean days to first detected estrus were 33, 37, 34, and 36 in supplemented, unsupplemented, high-production, and low-production cows. Treatment with beta-carotene and milk production did not affect days to first breeding (63, 67, 62, and 67), or services per conception (3.2, 5.1, 4.6, and 3.7). However, days open were reduced by supplementation (116 versus 186), but milk production had no effect (173 versus 129). Regressions of progesterone on sampling time within treatment and within milk production were significant. Regression of luteinizing hormone on time within production group was also significant. Neither beta-carotene nor milk production affected most reproductive measures, but differences were subtle in corpus luteum response to human chorionic gonadotropin, which may alter endocrine function.     

Relationships among body condition score,milk constituents,and postpartum luteal function in Norwegian dairy cows

Relationships among body condition score (BCS), milk constituents, and resumption of postpartum luteal function were studied in 162 lactations of first- and second-parity Norwegian dairy cows. Milk components included acetone, lactose, fat, protein, urea, and ratios of fat to protein and fat to lactose. Milk progesterone concentrations were used to determine intervals from calving to first luteal response (> 5 ng/ml). Intervals to first luteal response were divided into categories of early (< or = 24 d) or late (> 24 d) responses. Higher BCS were observed during wk 4 and 5 postpartum among both first- and second-parity cows with early compared with delayed luteal responses. Second-parity cows with early onset of luteal function also had higher BCS from wk 6 through 12, whereas first-parity cows with early onset of luteal function had higher BCS from wk 13 through 15. Higher acetone levels from wk 2 through 4 postpartum were associated with late luteal response in second-parity cows. Greater milk lactose content during wk 1, 2, 3, 6, 7, and 8 postpartum and higher fat fractions during wk 4 postpartum were related to early luteal response in second-parity cows. Relationships between milk constituents and onset of luteal function were less evident and occurred later postpartum among first-parity cows than among second-parity cows. Measures of weekly milk composites obtained during the early postpartum period and BCS were closely associated with postpartum resumption of luteal function. Acetone and lactose values in milk from the first 4 wk postpartum predicted postpartum luteal function in second-parity cows at a sensitivity of 0.84 and specificity of 0.86.     

Relationship of plasma nonesterified fatty acids and walking activity in postpartum dairy cows

To survive and produce milk, postpartum dairy cows use their reserves through lipolysis. If the negative energy balance is severe, nonesterified fatty acids (NEFA) are formed that can impair several physiological processes. A pilot study suggested that increased walking activity after calving may be related to a reduced serum concentration of NEFA. The objective of this study was to determine the relationship between plasma concentrations of NEFA and walking activity in dairy cattle during the postpartum period. Data were collected from 33 multiparous Holstein-Friesian dairy cows. Walking activities were quantified using pedometry, and blood samples were collected for determination of NEFA. Results of this study indicated that a negative relationship existed between walking activity and plasma NEFA concentrations in postpartum dairy cows.     

Modulation of fat-soluble vitamin concentrations and blood mononuclear leukocyte populations in milk replacer-fed calves by dietary vitamin A and beta-carotene

Dairy calves (n = 18), separated from dams at birth, were fed 1 L of pooled-colostrum. For the remaining 7 wk of the study, they were fed one of three diets consisting of either a custom-formulated milk replacer without vitamin A (controls), or supplemented with retinyl palmitate (equivalent to 32,000 IU of vitamin A/d) or with beta-carotene (equivalent to 20,000 IU of vitamin A/d). Plasma retinol, beta-carotene, and RRR-alpha-tocopherol concentrations were lowest at birth, and increased substantially from birth to 1 wk postpartum in all groups, a probable consequence of ingestion of colostrum. From 1 to 7 wk of age, retinol concentrations were greatest in retinyl palmitate-supplemented calves, intermediate in beta-carotene-supplemented calves and lowest in control calves. At 2, 3, 5, 6, and 7 wk, RRR-alpha-tocopherol concentrations were lower in retinyl palmitate-supplemented calves than in control calves. A negative correlation between plasma retinol and vitamin E concentrations existed from wk 2 to 7, suggesting vitamin A influences the absorption and distribution of RRR-alpha-tocopherol. Supplemental retinyl palmitate, but not beta-carotene, was associated with a reduction in the percentage of blood mononuclear leukocytes expressing CD2, CD4, and CD8-T cell antigens and interleukin-2 receptors. By wk 7, leukocyte populations from retinyl palmitate-supplemented calves were more similar to those from adult cattle than those from control calves, suggesting that supplemental vitamin A, as retinyl palmitate, affects the maturation of the neonatal immune system. Differences in the composition of blood mononuclear leukocyte populations may represent changes in immune competency.     

Reproductive and metabolic characteristics of dairy cattle supplemented with beta-carotene

Seventy-eight Holstein cows alternately were assigned at calving to receive beta-carotene supplementation or act as controls to determine effects of beta-carotene on reproduction and carotene, luteinizing hormone, progesterone, insulin, glucose, and glucagon concentrations in blood plasma. Cows were fed a corn silage-based complete ration. Biweekly jugular blood samples were collected beginning the week after parturition through 90 days. At day 30, supplemented cows received 600 mg synthetic beta-carotene daily for 60 days. Plasma carotene reached a peak of 2.45 micrograms/ml compared to 1.50 micrograms/ml in controls. Supplementation significantly increased plasma carotene but had no effect on luteinizing hormone, progesterone, insulin, glucose, glucagon, or reproductive measures. Days to first heat, days to first breeding, days open, and services per conception averaged 74, 74, 95, and 1.7 for supplemented cows and 64, 76, 102, and 1.9 for control cows. Progesterone increased as lactation progressed. Somatic cells were not different between supplemented and control cows. Supplementation of beta-carotene did not improve reproductive efficiency or alter luteinizing hormone, progesterone, insulin, glucose, or glucagon in blood plasma or affect somatic cells in milk.     

Genetic analysis of postpartum measures of luteal activity in dairy cows

The objective of this study was to estimate genetic parameters for measures of luteal activity during the first 60 d postpartum. Analyses were made with different sampling intervals to investigate the possibility of combining progesterone measurement with routinely performed milk recording. Progesterone level in milk as an indicator of female fertility when selecting sires in a progeny-testing scheme was also examined. Data were collected from 1996 to 1999, and comprised 1,212 lactations from 1,080 British Holstein-Friesian cows at 8 commercial dairy farms in the United Kingdom. Milk samples for progesterone analysis were collected thrice weekly. Mixed linear animal models were used to analyze the data. Heritability for the percentage of samples with luteal activity during the first 60 d postpartum (PLA) was 0.30 and decreased with more infrequent sampling to 0.25, 0.20, and 0.14 for weekly, twice-monthly, and monthly sampling, respectively. Measures of PLA had a high negative genetic correlation with prolonged anovulation (−0.53 for monthly sampling, < −0.87 otherwise) and a moderate positive genetic correlation with persistent corpus luteum in the first estrus cycle (>0.65 if at least twice-monthly sampling). Genetic correlations with interval from calving to commencement of luteal activity were close to −1 for all PLA measurements and the selection index calculations showed that monthly progesterone sampling could be used with high accuracy (0.80 with 50 daughters per bull) to predict breeding values for commencement of luteal activity. Progesterone analysis at the time of regular milk recording could thereby be used to select for an early interval from calving to commencement of luteal activity and, at the same time, a decreased frequency of prolonged anovulation during the postpartum period.     

Relationship of in vitro immune function with health and production in Holstein cattle.

Eighty-seven lactating Holstein cows from the Iowa State University Breeding Research Herd were evaluated for 20 in vitro measures of immune function. Principal component analysis was used to discard redundant assay variables such that the 11 remaining variables were more nearly independent than the original variables. Multiple linear regression in an animal model was used to determine the effects of these 11 variables on lifetime production and on general, under, and reproductive health traits. A significant joint effect of the 11 immune function variables on California mastitis test scores was observed. California mastitis test scores were positively correlated with antibody-dependent neutrophil cytotoxicity and negatively correlated with antibody-independent neutrophil cytotoxicity. Wisconsin mastitis test scores were also positively associated with antibody-dependent neutrophil cytotoxicity. Cytochrome c reduction was negatively associated with mammary and total health costs. A positive relationship between clinical mastitis and discarded milk and IgG2 was observed, and IgG1 was associated with increased quarter California mastitis test scores and increased production. Thus, certain in vitro immune function assays may serve as indicators of susceptibility to health problems in dairy cattle, particularly for traits associated with udder health.     

In vitro effects of beta-carotene and vitamin A on peripartum bovine peripheral blood mononuclear cell proliferation

The effects of beta-carotene, retinol, and retinoic acid on function of mononuclear cells during the peripartum period was assessed in vitro. Blood was collected from 14 Holstein cows on wk -4, -1, 0, 1, and 4 postpartum, and mononuclear cells were obtained by gradient centrifugation. Mononuclear cell proliferation induced by concanavalin A was measured in the presence of beta-carotene, retinol (1 x 10(-9) and 1 x 10(-8) M), and retinoic acid (1 x 10(-10) and 1 x 10(-9) M). Retinol and beta-carotene had no effect on spontaneous cell proliferation, whereas retinoic acid was suppressive. However, 1 x 10(-9) M beta-carotene enhanced concanavalin A-induced proliferation at wk -1, whereas 1 x 10(-8) M beta-carotene was suppressive at wk -4. Retinoic acid suppressed concanavalin A-induced proliferation at wk 0, but retinol had no effect. These results suggest a mechanism by which beta-carotene affords the mammary gland protection against infection immediately prepartum.     

Relationship of fertility to milk yield in Swedish cattle

Data consisted of 48,830 and 21,136 records of Swedish Red and White and Swedish Black and White cattle. Fertility in virgin heifers and in first lactation cows was measured by first service pregnancy rate and number of services per pregnancy. Production trait considered was FCM produced in first 100 d of lactation. The heritabilities for fertility traits in virgin heifers and first lactation cows were about .05 in both breeds. The genetic correlations between fertility measures within parity were close to one in both breeds, suggesting that these were measures of the same trait. The genetic correlations between fertility in virgin heifer and in first lactation were about .88 for Swedish Red and White breed and between .6 and .7 for Swedish Black and White breed. The association between fertility and production in first lactation cows was antagonistic, with genetic correlations between first service pregnancy rate and milk yield of -.13 and -.32 for Swedish Red and White and Swedish Black and White breed, respectively. The association between first service pregnancy rate in virgin heifers and milk yield in first lactation was also antagonistic, with genetic correlations of -.14 and -.41 for Swedish Red and White and Swedish Black and White breed, respectively.     

Effects of supplemental vitamin A or beta-carotene during the dry period and early lactation on udder health.

Effects of vitamin A or beta-carotene supplementation during the dry period and early lactation on the frequency of new intramammary infection and clinical mastitis and on SCC and milk yield were examined. Eighty-two Holstein cows were randomly assigned to one of three groups: 1) 50,000 IU/d of vitamin A per cow (approximately equivalent to 1978 NRC recommended daily intake for dairy cows); 2) 170,000 IU/d of vitamin A per cow; or 3) 50,000 IU/d of vitamin A plus 300 mg of beta-carotene per cow. Cows were supplemented during the 2 wk before drying off, throughout the dry period, and for the first 6 wk of lactation. Concentrations of serum vitamin A did not differ among treatment groups but tended to decrease for all treatment groups from 14 d before drying off to calving. After calving, serum vitamin A tended to increase in all groups through wk 6 of lactation. Serum beta-carotene tended to be higher in beta-carotene-supplemented cows at dry-off, in the early dry period, and again during lactation. Serum beta-carotene decreased sharply in all groups during the prepartum period. The frequency of clinical mastitis and of new intramammary infection during the dry period, near parturition, and for the first 6 wk of lactation did not differ among treatment groups. The percentage of quarters newly infected over the entire trial was 26.8 in the control, 25.0 in the high vitamin A, and 30.6 in the beta-carotene group. Pathogens isolated most frequently were coagulase-negative staphylococci, streptococci other than Streptococcus agalactiae, and coliforms.(ABSTRACT TRUNCATED AT 250 WORDS)