Somatomedin C in dairy cows related to energy and protein supply and to milk production

Expanded Therapeutic Applications of Holarrhena Antidysenterica: A Review

BACKGROUND

The use of medicinal plants as a rich resource of therapeutic agents in the treatment and prevention of diseases & ailments has been recognized for millennia and is highly regarded worldwide. Holarrhena antidysenterica (H. antidysenterica), also called kurchi, or kutaj, has been utilized since the dawn of time, Apocynaceae member, also known as H. pubescens, is praised for the medicinal uses of its stem bark, leaves, and seeds in Ayurveda.

OBJECTIVE

The study concentrated on aggregate information regarding H. antidysenterica's therapeutic effects. The purpose of the study was to compile pharmacological activities of H. antidysentrica seeds.

METHODS

Regardless of its broad variety of biological and possible therapeutic uses, there has been increasing concern regarding the use of H. antidysenterica.

RESULT

Various phytochemicals have been extracted from H. antidysenterica in recent years and have demonstrated typical pharmacological properties, including antibacterial, anti-diarrhoeal, anti-diabetic, anti-oxidant, anti-urolithic, and anti-inflammatory activity.

CONCLUSION

This review paper investigated the in-depth description and pharmacological properties of the plant, which produced significant findings on the chemical components present and also verified the traditionally claimed properties associated with the plant.

Metabolic and physiological adaptations to first and second lactation in Holstein dairy cows

Huge differences exist between cow yields and body sizes during their first and second lactations. The transition period is the most critical and investigated phase of the lactation cycle. We compared metabolic and endocrine responses between cows at different parities during the transition period and early lactation. Eight Holstein dairy cows were monitored at their first and second calving during which they were reared under the same conditions. Milk yield, dry matter intake (DMI), and body weight (BW) were regularly measured, and energy balance, efficiency, and lactation curves were calculated. Blood samples were collected on scheduled days from -21 d relative to calving (DRC) to 120 DRC for the assessment of metabolic and hormonal profiles (biomarkers of metabolism, mineral status, inflammation, and liver function). Large variations in the period in question for almost all variables investigated were observed. Compared with their first lactation, cows during their second lactation had higher DMI (+15%) and BW (+13%), their milk yield was greater (+26%), lactation peak was higher and earlier (36.6 kg/d at 48.8 DRC vs. 45.0 kg/d at 62.9 DRC), but persistency was reduced. Milk fat, protein, and lactose contents were higher during the first lactation and coagulation properties were better (higher titratable acidity, faster and firmer curd formation). Postpartum negative energy balance was more severe the during the second lactation (1.4-fold at 7 DRC) and plasma glucose was lower. Circulating insulin and insulin-like growth factor-1 were lower in second-calving cows during the transition period. At the same time, markers of body reserve mobilization (β-hydroxybutyrate and urea) increased. Moreover, albumin, cholesterol, and γ-glutamyl transferase were higher during second lactation, whereas bilirubin and alkaline phosphatase were lower. The inflammatory response after calving was not different, as suggested by the similar haptoglobin concentrations and only transient differences in ceruloplasmin. Blood growth hormone did not differ during the transition period but was lower during the second lactation at 90 DRC, whereas circulating glucagon was higher. These results agree with the differences in milk yield and confirmed the hypothesis of a different metabolic and hormonal status between the first and second lactation partly related to different degrees of maturity.

Adaptive Responses of Thyroid Hormones, Insulin, and Glucose during Pregnancy and Lactation in Dairy Cows

The study examined the effects of different stages of pregnancy and lactation on thyroid, insulin, and glucose responses in dairy cows. In the present study, 30 dairy cows (10 Holstein, 10 Simmental, and 10 Brown) at 30 ± 20 d of lactation were randomly selected and blood samples were collected once every 60 d for one year to measure circulating thyroid stimulating hormone (TSH), total and free triiodothyronines (T3, fT3) and thyroxines (T4, fT4), insulin, and glucose. Pregnant cows showed higher T4 (p = 0.010) and insulin (p = 0.046) concentrations at >180 d than at >60−120 d of pregnancy and in nonpregnant cows. Along the lactation phase, circulating T4 concentrations showed a biphasic trend, decreasing from 0−60 d to >60−120 d phase, which showed the lowest values, and then increasing until the end of lactation (>300 d) (p = 0.016). Glucose showed the highest concentrations at the start of lactation (0−120 days) and the lowest values at the end (p = 0.008). The monitoring of thyroid hormones, insulin, and glucose changes represents an important tool to evaluate the anabolic and/or catabolic adaptation in response to functional periods in dairy cows, which can potentially predispose the cows to an excessive negative energy balance and related metabolic issues.

Nutritional effects on resumption of ovarian cyclicity and conception rate in postpartum dairy cows

Increased genetic potential for milk production has been associated with a decline in fertility of lactating cows. Following parturition the nutritional requirements increase rapidly with milk production and result in negative energy balance (NEBAL). NEBAL delays the time of first ovulation thereby affecting ovarian cycles before and during the subsequent breeding period The effects of NEBAL on reinitiation of ovulation are manifested through inhibition of LH pulse frequency and low levels of glucose, insulin and IGF-I in blood that collectively restrain oestrogen production by dominant follicles. Upregulation of LH pulses and peripheral IGF-I in association with the NEBAL nadir increases the likelihood that emerging dominant follicles will ovulate. The legacy of NEBAL is reduced fertility after insemination in conjunction with reduced serum progesterone concentrations. Diets high in crude protein support high milk yield, but may be detrimental to reproductive performance. Depending upon protein quantity and composition, serum concentrations of progesterone may be lower and the uterine luminal environment is altered. High protein intake is correlated with plasma urea concentrations that are inversely related to uterine pH and fertility. The direct effects of high dietary protein and plasma urea on embryo quality and development in cattle are inconsistent. In conclusion, the poor fertility of high producing dairy cows reflects the combined effects of a uterine environment that is dependent on progesterone, but has been rendered suboptimal for embryo development by antecedent effects of negative energy balance and may be further compromised by the effects of urea resultingfrom intake of high dietary protein.

Physiological Adaptations to Milk Production that Affect the Fertility of High Yielding Dairy Cows

The high yielding dairy cow is expected to produce a substantial milk output every year and at the same time to conceive and maintain a pregnancy to term. To fulfil lifetime production potential a balance between yield, fertility and other influential factors has to be achieved. Any inability on the part of the management system to identify and rectify problems or on the part of the cow to cope with metabolic demands invariably results in economic or welfare issues. Our studies of high yielding dairy cows have revealed that some animals are capable of normal reproductive function whilst others are classic repeat breeders (requiring 3+ services per conception) or simply fail to rebreed. It is well established that the somatotrophic axis (growth hormone and insulin-like growth factors) drives lactation in ruminants but it is also intimately involved in reproductive processes. An awareness of metabolic adaptations to lactation that impact on reproduction in dairy cows is needed for appropriate management.

The objective of our studies was to explore the metabolic profiles of high yielding dairy cows to identify factors influencing their ovarian function and fertility, hence to characterise the physiological adaptations involved. Our studies revealed different relationships between progesterone profile categories and metabolic status post partum. Delayed ovulation (DOV) or persistent corpora lutea (PCL) may be an appropriate response to a nutritional state or physiological situation and it may therefore be inaccurate to refer to these as ‘abnormal’. Whilst associated with high milk yields, not all profile categories detrimentally affected fertility parameters. Delayed ovulation postcalving (DOV1) was identified as the most prevalent abnormal profile encountered in first lactation high yielding cows. This may have occurred because the cows were not yet physically mature and unable to sustain both milk production and growth. The condition lasted long enough (71 ± 8.3 days from calving) to have a detrimental impact on their overall fertility parameters and was associated with significant physiological changes, representative of tissue mobilisation. Although the incidence of persistent luteal phases (PCL1 and PCL2) in dairy cows is increasing, this condition was not found to have any substantial detrimental effects on fertility or production parameters of the primiparous or multiparous cows in these studies. The main reproductive problems in our high yielding primiparous and multiparous cows appeared to be a failure to ovulate and conceive at the expected time or to maintain a pregnancy. These situations were associated predominantly with high milk yields and low concentrations of plasma IGF-I. A failure to ovulate appears to occur when body reserves are mobilised to maintain milk yield at the expense of reproduction and seems most likely to occur in primiparous high yielding cows or those experiencing GH-resistance (low IGF-I) due to excessive body condition loss, reduced feed intakes and factors such as stress and disease. More detailed investigations of dietary means of increasing IGF-I and optimising insulin concentrations, targeted at important reproductive times, are required in high yielding dairy cows, to aid in their management.

Thyroid Hormones, Insulin, Body Fat, and Blood Biochemistry Indices in Dairy Cows During the Reproduction/Production Cycle

This study investigated the changes in: thyroid hormones, amount of subcutaneous fat, and selected indices of blood biochemistry in dairy cows in relation to the reproduction/production cycle. The blood samples were collected both ante- and post-partum every two weeks. When evaluating the mean values of the investigated indices, the major changes were recorded in dairy cows 3 to 14 days after calving. During this period, we observed a significant decrease in the mean serum levels of T3 (P < 0.05), T4 (P < 0.01), and triglycerides (P < 0.01). An opposite trend was observed with a significant increase after calving in the: mean serum levels of β-hydroxybutyrate (P < 0.05), urea (P < 0.01), and mean AST activities (P < 0.05). A significant increase over the normal range was recorded in the average levels of non-esterified fatty acids (P < 0.01) and total bilirubin (P < 0.01). From the next sampling (28 days after calving) onwards we recorded a significant increase in the blood serum levels of cholesterol (P < 0.01), total lipids (P < 0.01), total protein (P < 0.01), as well as a significant decrease in the insulin levels (P < 0.05) and a reduced layer of subcutaneous fat (P < 0.01). The blood serum iodine concentration showed only slight significant changes (P < 0.05) during the observation. Blood serum levels of glucose did not show any significant changes during the whole observation period. Within the whole observation period we found a negative correlation between T3 levels and the layer of subcutaneous fat (r = −0.2606; P < 0.05). This correlation was much more marked in cows 3 to 14 days after calving (r = −0.5077; P < 0.05), which may indicate a possible relationships between the thyroid status, body condition, and post partum negative energy balance.

Limitations of high Alpine grazing conditions for early-lactation cows: effects of energy and protein supplementation

In each of 2 years (years A and B), the effects of three nutritional regimes were examined using 12 cows kept at pasture for 77 days at 2000 m above sea level. Two supplement formulations (1 and 2) were designed, both equally high in readily fermentable energy (14·6 MJ metabolizable energy (ME) per kg dry matter (DM)) but differing in crude protein content (53 and 193 g/kg DM). The treatments imposed were either pasture grass alone (control groups; both seasons) or grass and supplements provided at three levels relative to energy (E) and protein (P) maintenance requirements estimated for lowland conditions. These levels were (i) 1·0 E: 0·8 P provided by 4·6 kg of supplement 1 per day in both years; (ii) 0·5 E: 0·4 P provided by 2·2 kg of supplement 1 per day in year A; (iii) 1·0 E: 2·5 P provided by 4·4 kg of supplement 2 per day in year B. Intensive measurement periods, including food intake estimation by the double alkane technique, were carried out in weeks 3, 7 and 11 on Alpine pasture. Performance data, plasma levels of indicative blood traits and body condition were additionally monitored in the cows at a lowland site for 2 weeks prior to transport. Supplementing with a high energy/low protein concentrate gave no clear benefit in milk yield, which declined proportionately by 0·33 in the 11 weeks under Alpine conditions. Provision of additional supplementary protein (supplement 2) resulted in a proportionate decline in milk yield of only 0·20 over the 11-week period. Cows exhibited high substitution ratios of 1·4 to 2·6 kg herbage DM per kg concentrate DM and cows on all treatments were estimated to consume similar amounts of ME. A combination of reduced fibre intake and lower fibre digestibility with supplementation significantly reduced milk fat contents to low levels. Energy supplementation significantly reduced plasma β-hydroxybutyrate levels. However, live-weight and body tissue loss rates (based on ultrasonic scans of subcutaneous fat layer and longissimus dorsi muscle) were equally great with and without energy supplementation but less severe with extra protein (supplement 2). Adaptation to the high Alpine conditions was achieved in all treatments as indicated by increased blood haemoglobin, accompanied by a lower plasma level of insulin-like growth factor-I. Plasma thyroid hormone levels suggested that adaptation to energy deficiency and possibly to cold was more effective with supplementary energy. Other energy-dependent blood metabolites and insulin responded similarly in all treatments to high altitude grazing. Estimated maintenance energy requirement for Alpine conditions was 0·72 times greater than lowland maintenance requirement.

Serum thyroid hormone evaluation during transition periods in dairy cows

Abstract. Thirty-five multiparous Holstein dairy cows were selected from a high-producing dairy farm in northeastern Italy: 16 in second lactation (L2), 10 in third lactation (L3) and 9 in fourth lactation (L4). Blood sampling was carried out 7 ± 5 days before calving (Pre/C) and 7 ± 5 days after calving (Post/C). Serum triiodothyronine (T3), thyroxine (T4) and a thyroid-stimulating hormone (TSH) were assessed. Two-way analysis of variance (ANOVA) showed statistically significant effects of class (L2, L3, L4) and of period (Pre/C, Post/C) on the parameters studied (T3, T4, TSH). In particular, Bonferroni's multiple comparison test showed lower values in post-calving than in the pre-calving in L2 and L3 for TSH; lower values in post-calving than in the pre-calving in L2 for T3; and lower values in post-calving than in the pre-calving in L2, L3 and L4 for T4. Our results improve the knowledge of endocrine and metabolic changes occurring in dairy cows during transition periods and may be useful to supply a new strategy for the improvement of dairy cow farm management and reproductive performance.

Metabolic response of early-lactating cows exposed to transport and high altitude grazing conditions

The metabolic response of dairy cows to high as opposed to low altitude conditions (2000 m v. 400 m above sea level) was determined. In the first experiment, four cows were subjected to a series of measurements before, during and after transport from lowland to high altitude pasture. During transport, cortisol, l-lactate and non-esterified fatty acids were significantly elevated but decreased within 1 to 3 days to initial levels. After transport, β-hydroxybutyrate and the thyroid hormones immediately increased and returned within 3 weeks to initial levels. Plasma urea increased during transport and subsequently was at an intermediate level due to the different diet. There were no direct carry-over effects of transport on metabolic traits during pasturing.

In the second experiment, three groups of six different dairy cows were either grazed in one of two consecutive years or kept inside (2nd year only). Lowland sojourn lasted for 4 weeks, and high altitude period for 8 weeks. At the end of high altitude sojourn, both outside and inside groups were found still to have significantly higher plasma cortisol values than at lowland. Thyroid hormones and ketosis related metabolites sharply increased at the start of the alpine period and were elevated for 1 to 3 weeks thereafter. According to the hormonal and metabolic profiles, the permanently housed cows did not benefit from the less adverse climatic conditions and the lower physical strain. Plasma urea closely reflected dietary changes in the ratio of nitrogen to fermentable organic matter. Plasma protein, albumin, creatinine, and liver enzyme activities were not affected by transport or high altitude sojourn in both experiments. The results indicate that the metabolic response to transport and high altitude conditions can be mostly explained by the efforts to cover the additional energy requirements. Overall the data suggest a wide but nevertheless limited ability of early-lactating cows to adapt to high altitude conditions.

Relationship of post-partum interval in mature beef cows with nutritional environment, biological type and serum IGF-1 concentrations

Mature cows of nine breeds were fed (four cows per level within breed) at either 0·55, 0·71, 0·88 or 1·05 MJ metabolizable energy (ME) per kg initial body weight0·75 per day during non-lactational periods for an average of 4 years. During lactation, energy allowances were increased by 0·17 MJ ME per kg body weight0·75 per day. Breeds represented four biological types: moderate genetic potential for milk yield and growth (Angus, Hereford, Red Poll), moderate milk and high growth (Charolais, Eimousin), high milk and moderate growth (Braunvieh, Pinzgauer) and high milk and growth (Gelbvieh, Simmental). The objective was to test the effects of biological type and nutritional environment on length of post-partum interval as determined from serum progesterone levels. The potential of serum insulin-like growth factor-1 (IGF-1) level at 3 weeks post partum for predicting the length of the post-partum interval was also evaluated. Non-parametric statistical analyses appropriate for right-censored survival data were used to test effects on post-partum interval because collection of serum was terminated prior to ovulation in some cows.

Energy availability × biological type effects on post-partum interval were significant. Increased energy availability tended to decrease post-partum interval in all biological types with high potential growth types exhibiting the greatest positive response to increased food. Post-partum interval for types with high growth potential was shorter within food level when associated with high rather than moderate potential for milk yield. Serum IGF-1 was related to post-partum interval at lower energy availability but appeared to have limited usefulness for identifying cows with extended intervals. Inherent direct and maternal production potential interact with available food resources to influence the post-partum interval of mature beef cows.

Interrelationships between negative energy balance (NEB) and IGF regulation in liver of lactating dairy cows

In dairy cows, negative energy balance (NEB) during the early post-partum period is associated with major alterations in the growth hormone-insulin-like growth factor (GH-IGF) axis. Since the liver mediates nutrient partitioning during lactation, we aimed to determine how NEB alters the endocrine regulation of the insulin-like growth factor (IGF) system by investigating the expression of IGF family members and related steroid receptors. On the second day of lactation, cows were allocated to one of two treatments designed to produce mild (MNEB) or severe NEB (SNEB). MNEB cows (n=5) were fed ad lib grass silage supplemented with concentrate and milked x1 daily and SNEB cows (n=6) were restricted in dietary intake and milked x3 daily. Energy balance (EB) status was monitored until the second week of lactation when plasma and liver samples revealed a markedly divergent metabolic profile. At this time, plasma protein and hepatic mRNA for IGF-I was reduced in SNEB cows compared with MNEB cows. Both levels of expression correlated highly when data from all animals was pooled (r=0.963; P<0.01). SNEB cows also exhibited reduced hepatic expression for transcripts encoding IGF-1R, IGF-2R, IGF binding proteins (IGFBPs) -3, -4, -5, -6, acid labile subunit, and receptors for oestrogen (ERalpha) and growth hormone (total GHR and 1A variant), while the expression of IGFBP-2 was elevated. Expression of mRNA for IGF-II, IGFBP-1 and receptors for insulin (A/B) and glucocorticoid (alpha) was unaffected by EB. Results demonstrate that SNEB affects hepatic synthesis of IGF-I, and other components known to modulate the bioavailability and stability of circulating IGF-I.

Effect of Photoperiod in the Third Trimester of Gestation on Milk Production and Circulating Hormones in Dairy Goats

Multiparous Israeli Saanen goats (n = 8) were blocked at dry off (approximately 45 d prepartum) into 2 treatments of 4 goats each based on body weight (BW), previous milk production, and the number of detected embryos in utero. Treatments consisted of long-day (16 h light:8 h dark) and short-day (8 h light:16 h dark) photoperiods at normothermic ambient temperature (22 degrees C, 72% relative humidity). All goats were returned to ambient photoperiod after kidding, milked twice daily, and milk yield was automatically recorded. Dry matter intake was similar between treatments and averaged 980 g/d. Milk production was greater in the short-day than in the long-day treatment (2,932 vs. 2,320 g/d) during the 12-wk experimental period. Milk protein and lactose contents were similar in both treatments and averaged 3.61 and 4.88%, respectively, whereas milk fat was greater in the long-day treatment (4.80 vs. 4.22%). Plasma insulin-like growth factor 1 was greater in the long-day treatment (149 vs. 73 ng/mL) during the dry period than in the short-day treatment, but was similar postkidding, averaging 76 ng/mL. Concentrations of triiodothyronine in plasma were similar in both treatments during the dry period, but greater during lactation in the short-day treatment (122.1 vs. 94.1 ng/mL). Plasma prolactin was greater in the long-day than in the short-day treatment during the dry period (28.0 vs. 17.5 ng/mL), whereas it was similar throughout lactation (11.7 ng/mL). These data support the idea that greater milk production in goats exposed to short days during the dry period is not explained by differences in feed intake or increased secretion of insulin-like growth factor 1.

Metabolic Profiles in Ovulatory and Anovulatory Primiparous Dairy Cows During the First Follicular Wave Postpartum

Metabolic hormones affect ovarian function in the cow. However, the relationship between metabolic factors and ovarian function is not clear in the postpartum primiparous cow because they are still growing. The aim of the present study was to investigate in detail the time-dependent profile of the metabolic hormones, metabolites, and milk yields of ovulatory and anovulatory primiparous cows during the first follicular wave postpartum. We used 16 primiparous Holstein cows and obtained blood samples for the profiles of metabolites (glucose; non-esterified fatty acid, NEFA; ketone body; total cholesterol; and aspartate aminotransferase), metabolic hormones (growth hormone, GH; insulin-like growth factor-I, IGF-1; and insulin), and progesterone every other day from 1 to 21 days postpartum. In addition, all ovaries were observed using ultrasound. Dairy milk yield was recorded during the experimental period. In all cows, the first follicular wave postpartum was observed and 6 of the cows ovulated. The plasma glucose (P<0.0001) and IGF-1 (P<0.001) concentrations were lower and the plasma NEFA (P<0.0001) and ketone bodies (P<0.0001) concentrations and daily milk yield (P<0.0001) were higher in the anovulatory cows compared to the ovulatory cows. However, the GH levels, which enhance lipolysis for milk production, insulin and other metabolites did not differ between the two groups. In conclusion, the present study suggests that anovulation of the dominant follicle during the first follicular wave postpartum in primiparous cows is induced by low IGF-1 levels that are similar to those of multiparous cows. In addition, anovulatory cows are likely to mobilize body fat stores for milk production more easily than ovulatory cows.

Changes in Plasma Metabolic Hormone Concentrations During the Ovarian Cycles of Japanese Black and Holstein Cattle

The aim of the present study was to investigate the changing profiles of plasma metabolic hormones during the ovarian cycles of beef and dairy cattle. We used 16 non-pregnant, non-lactating Japanese Black beef cattle (6 heifers and 10 cows; parity=2.3 +/- 0.8) and 12 multiparous Holstein dairy cows (parity=3.0 +/- 0.3). Blood samples for hormonal analysis (growth hormone, GH; insulin-like growth factor-I, IGF-1; insulin; and progesterone, P4) were obtained twice weekly for 40 days before artificial insemination for Japanese Black cattle and from 50 to 100 days postpartum for Holstein cows. Luteal phases were considered normal if the P4 concentrations for at least 3 time points over the course of 7 days remained above 1 ng/ml and at least 2 of the time points were above 2 ng/ml. The patterns of the ovarian cycles were classified into two types (normal or abnormal, such as having prolonged luteal phase and cessation of cyclicity) on the basis of the plasma P4 profiles. The plasma concentrations of IGF-1 in both breeds increased transiently during the preovulatory period when the P4 levels were low and decreased to lower levels during the luteal phase when the P4 levels were high. The plasma concentrations of insulin in the 3(rd) week of normal ovarian cycles when the plasma P4 concentration dropped to less than 1 ng/ml were higher than those at other time points in the Japanese Black cattle, but not in the Holstein cows. The plasma concentrations of GH did not change during the ovarian cycle in either breed. In conclusion, the present study indicates that the plasma IGF-1 concentration increases during the follicular phase (low P4 levels) and decreases during the luteal phase (high P4 levels) in non-lactating Japanese Black and lactating Holstein cattle. The results suggest that ovarian steroids, rather than nutrient status, may be related to the cyclic changes in IGF-1 secretion from the liver in cattle.

Endocrine characteristics of late pregnant hyperketonaemic ewes and their reproductive performance following the induction of ovarian cyclicity out of the breeding season

Ketosis was diagnosed in a flock of Merino ewes that conceived from synchronised oestrus in the early autumn period. On day 140 of pregnancy the ewes were sampled for determination of betaOH-butyrate (BHB), AST, glucose, non-esterified fatty acids (NEFA), total cholesterol (TCH), insulin, T4, T3, cortisol, IGF-1 and leptin. The results were evaluated according to the number of fetuses born some days later and the presence of hyperketonaemia (BHB: > or = 1.60 mmol/l). In May, about 3 months after lambing, cyclic ovarian function was induced (Cronolone + eCG), and the ewes were inseminated artificially (AI) 48 h after the removal of gestagen-containing sponge. At the time of AI and 10 days later blood samples were collected again to check the plasma levels of the same constituents as previously (in samples taken at AI), and to monitor the ovarian response by assaying progesterone (in both samples). On day 140 of gestation significantly lower BHB levels were detected in dams with single (n = 41) than in those with twin (n = 57) pregnancies. Hyperketonaemia was found only in ewes bearing twins (n = 27). These animals had higher NEFA and cortisol, and lower TCH, insulin, IGF-1, leptin and T3 levels than their normoketonaemic twin-bearing flock-mates, and those with single pregnancy. The blood glucose concentrations varied within a wide range, and the means of groups did not exhibit any significant differences. The formerly hyperketonaemic individuals were characterised by lower leptin level 3 months after lambing, and they showed a poorer response to the cycle-induction procedure than the others. The non-responders had lower IGF-1 and leptin levels than those ovulated after this treatment. It was concluded that the subclinical form of ovine ketosis is characterised by complex endocrine alterations, reflecting an obvious form of negative energy balance. If attempts to induce cyclic ovarian function outside the breeding season are made soon after lambing, the ovarian response and fertility of these ewes may also be depressed.

Physiology of the periparturient period and its relation to severity of clinical mastitis

Incidence of clinical mastitis is highest at drying off and during the periparturient period. Intramammary Escherichia coli infection in high-yielding cows can show a severe clinical response during the early post-partum period. Severe clinical mastitis is mainly determined by cow factors, in particular the functionality of the circulating polymorphonuclear leukocytes (PMN) which are recruited to the mammary gland during the inflammatory reaction. There is a co-incidence between the periods of highest incidence of clinical mastitis and specific structural changes in the mammary gland. During the periparturient period, marked changes in various systemic and local hormones are related to the secretory state of the mammary gland epithelium (lactogenesis). Estrogen and progesterone induce proliferation of the mammary epithelium throughout gestation and act as survival factors in different tissues, although conflicting data have been reported on their effect on PMN oxidative burst. Somatotropin (STH), responsible for maintenance of lactation in ruminants, has been shown to positively influence innate immunity and a more rapid recovery in milk production of severely affected animals. The concentration of STH, and as a result also IGF-I levels is, however, quite low during early lactation. IGF-I and its regulating binding proteins are associated with cell survival, modulation of apoptosis and functionality of PMN in humans. During early lactation, bio-availability of IGF-I is decreased, which might reduce its stimulating effects on PMN quality and functionality. PRL, concomitantly known as a lactogenic hormone and an immunoregulatory cytokine, has also been associated with modulation of the immune system. It is expected that in periparturient animals, hormone changes could interfere with the immune response and the clinical response of mastitis.

Effects of varying energy intake and sire breed on duration of postpartum anestrus, insulin like growth factor-1, and growth hormone in mature crossbred cows1

Objectives of this study were to evaluate effects of seven sire breed groups and three levels of daily ME intake (DMEI = 132 or 189 kcal ME/kg BW(0.75) or ad libitum), beginning 5 mo prepartum, on BCS, length of postpartum anestrus, and circulating concentrations of IGF-1 and GH in F1 cows (six to eight cows per sire breed in each DMEI group) out of Angus or Hereford dams. At the initiation of the study, BW were 522, 530, 548, 572, 575, 577, and 595 kg for cows sired by Longhorn, Galloway, 1960s Hereford or Angus, 1980s Hereford or Angus, or Nellore, Salers, and Shorthorn bulls, respectively (SE = 13; P < 0.001 for sire breed). After 4 mo on DMEI treatment during the pre-partum period, cows fed 132 kcal of ME/kg BW(0.75)gained little to no BW; cows fed 189 kcal ME/kg BW(0.75) gained 50 kg; and cows fed ad libitum gained 70 kg (all groups differ P < 0.05). Concentrations of progesterone in weekly blood samples collected 2 to 14 wk after calving were used to establish when normal luteal function resumed to predict length of postpartum anestrus. Length of anestrus was affected by level of DMEI in cows sired by Galloway, Longhorn, and Nellore bulls, but not other breeds (P < 0.02 for interaction of sire breed and DMEI). Level of DMEI, but not sire breed, affected (P < 0.01) BCS at wk 2 postpartum. Concentrations of IGF-1 at wk 2 postpartum differed (P < 0.001) due to sire breed, and changes in concentrations of IGF-1 from wk 2 to 14 were influenced (P < 0.03) by the interaction of sire breed and level of DMEI; which was primarily the result of differences in rate of decrease over time among different sire breed x level of DMEI groupings. Concentrations of GH did not differ due to sire breed but varied (P < 0.001) due to the interaction of DMEI and week postpartum, for which concentrations of GH did not differ at wk 2 but increased over time at rates that were inversely proportional to level of DMEI. Length of anestrus was negatively associated (P < 0.05) with day of calving, BCS, and BW. When effects of sire breed and level of DMEI were accounted for (residual correlation), length of anestrus was inversely associated (P < 0.01) with IGF-1 concentrations. Breed of sire influenced length of postpartum anestrus and energy balance, as predicted by IGF-1, in crossbred cows fed varying levels of DMEI.

Low Doses of Bovine Somatotropin During the Transition Period and Early Lactation Improves Milk Yield, Efficiency of Production, and Other Physiological Responses of Holstein Cows

The objectives of this experiment were to determine whether low doses of bovine somatotropin (bST) during the transition period and early lactation period improved dry matter intake (DMI), body weight (BW), or body condition score (BCS); provoked positive changes in concentrations of somatotropin, insulin, insulin-like growth factor-I (IGF-I), glucose, nonesterified fatty acids, and Ca; or improved milk yield (MY) response without obvious adverse effects on health status. Eighty-four multiparous Holstein cows completed treatments arranged in a 2 x 3 x 2 factorial design that included prepartum and postpartum bST, dry period (30 d dry, 30 d dry + estradiol cypionate, and 60 d dry), and prepartum anionic or cationic diets. Biweekly injections of bST began at 21 +/- 3 d before expected calving date through 42 +/- 2 d postpartum (control = 0 vs. bST = 10.2 mg of bST/d; POSILAC). At 56 +/- 2 d in milk, all cows were injected with a full dose of bST (500 mg of bST/14 d; POSILAC). During the prepartum period and during the first 28 d postpartum, no differences in mean BW, BCS, or DMI were detected between the bST treatment group and the control group. During the first 10 wk of lactation, cows in the bST treatment group had greater mean MY and 3.5% fat-corrected milk yield and lower SCC than did cows in the control group. When cows received a full dose of bST, an increase in milk production through wk 21 was maintained better by cows in the bST group. Mean concentrations of somatotropin, IGF-I, and insulin differed during the overall prepartum period (d -21 to -1). During the postpartum period (d 1 to 28), cows in the bST group had greater mean concentrations of somatotropin and IGF-I in plasma. Concentrations of Ca around calving did not differ because of bST treatment. Results suggest that changes in concentrations of blood measures provoked by injections of bST during the transition period and early lactation period resulted in improved metabolic status and production of the cows without apparent positive or negative effects on calving or health.

Sex steroids and growth factors in the regulation of mammary gland proliferation, differentiation, and involution

The mammary gland is subjected to major morphological and biochemical changes during the lactation cycle. It is therefore not surprising that this dynamic process is strictly controlled. The importance of the sex steroid hormones 17beta-estradiol and progesterone for normal development of the mammary gland was recognized several decades ago and has been unequivocally confirmed since. Furthermore, it is now also established that the influence of sex steroids is not restricted to mammogenesis, but that these hormones also control involution. Another important regulatory role is played by growth factors that have been shown to modulate survival (epidermal growth factor, amphiregulin, transforming growth factor alpha, insulin like growth factor, and tumor necrosis factor alpha) or apoptosis (tumor necrosis factor alpha, transforming growth factor beta) of mammary cells. However, the molecular mechanism underlying the influence of sex steroid hormones and/or growth factors on the development and function of the mammary gland remains largely unknown to date. Also scarce is information on the interaction between both groups of modulators. Nevertheless, based on the current indications compiled in this review, an important functional role for sex steroid hormones in the lactation cycle in co-operation with growth factors can be suggested.

An energy-rich diet causes rumen papillae proliferation associated with more IGF type 1 receptors and increased plasma IGF-1 concentrations in young goats

We tested the hypothesis that the dietary energy-dependent alterations of the rumen papillae size are accompanied by corresponding changes in systemic insulin-like growth factor (IGF)-1 concentration and in rumen papillary IGF type 1 receptors (IGF-1R). Young male goats (n=24) were randomly allocated to two groups (n=12) and fed a high level (HL) metabolizable energy [1200 kJ/(kg(0.75).d)] or a low level (LL) [500 kJ/(kg(0.75).d)] diet for 42 d. The concentration of ruminal total SCFA did not differ between the groups, but the molar proportion of butyric acid was enhanced by 70% in the HL group (P<0.05). Both the length and width of the papillae were greater (P<0.05) in the HL group, and the surface was 50-100% larger (P<0.05) in the tissue sampled from the artrium ruminis, the ventral ruminal sac and the ventral blind sac. Transport of Na+ across the rumen epithelium, which is amiloride sensitive, was higher (P<0.05) in the HL than in the LL group. Furthermore, the plasma IGF-1 concentration was about twofold higher in the HL group (P<0.05), and the maximal rumen epithelial IGF-1R binding was also higher in the HL (P<0.05) than in the LL group. IGF-1R mRNA and IGF-1 mRNA were detected in rumen papillae; however, they were unaffected by dietary treatments. DNA synthesis and cell proliferation of cultured rumen epithelial cells were higher (P<0.05) after IGF-1 treatment (25 or 50 microg/L) compared with those in the medium without IGF-1. Thus dietary energy-dependent alterations of rumen morphology and function are accompanied by corresponding changes in systemic IGF-1 and ruminal IGF-1R.

Responses of Holstein Cows to a Low Dose of Somatotropin (bST) Prepartum and Postpartum

Objectives were to evaluate the effects of a low dose of bovine somatotropin (bST) injected prepartum and postpartum on body condition score (BCS), body weight (BW), and milk yield (MY) in cows as well as somatotropin insulin, insulin-like growth factor-I (IGF-I), glucose, and nonesterified fatty acids (NEFA) in plasma. Holstein cows nearing second or later parities were assigned randomly to control (CON = 98) or bST-treated (TRT = 95) groups. Biweekly injections of bST began 21 +/- 3 d before expected calving and continued through 42 d postpartum (CON vs. TRT; 0 vs. 10.2 mg of bST/ d). From 42 to 100 d postpartum, no cows received bST. During yr 1, somatotropin, IGF-I, insulin, NEFA, and glucose were measured in plasma samples from 82 cows. During yr 2, effects of bST on BCS and BW of 111 cows were evaluated, but no blood samples were collected. Milk yields through 100 d of all 193 cows were analyzed. Prepartum treatment with bST resulted in greater prepartum plasma concentrations of somatotropin, insulin, and numerically greater NEFA but did not affect glucose or IGF-I. Postpartum bST increased mean plasma concentrations of somatotropin and NEFA, but not INS, IGF-I, or glucose. Mean BCS of cows did not differ prepartum, around parturition, or postpartum. Although mean BW did not differ prepartum or around calving, cows receiving bST maintained greater BW postpartum. Cows receiving bST tended to have higher MY (6.6%) in the first 60 d of lactation, but differences did not persist through 100 d, including approximately 40 d when no cows received bST. Number of cows that were culled due to health (CON = 3 vs. TRT = 2) or died (CON = 3 vs. TRT = 1) were not affected by treatment. Low doses of bST in the transition period resulted in higher postpartum BW, quicker recovery of body condition during lactation, and significantly more milk during treatment.

Energy imbalance related predisposition to mastitis in group-fed high-producing postpartum dairy cows

The energy imbalance related predisposition to mastitis was studied in group-fed postpartum dairy cows (n = 333) kept in 4 large-scale units and producing milk of low somatic cell count (SCC). Blood samples were taken on Days 1-3 after calving for assaying some metabolites and hormones related to the negative energy balance (NEB). If mastitis was diagnosed later, aseptic milk samples were taken to identify the pathogens. Considering pathogen types [contagious pathogens: Staphylococcus (S.) aureus, Gram-positive (GP) environmental pathogens, and Gram-negative (GN) environmental pathogens + mastitis with no detectable pathogens (NDP)] separately, stepwise logistic regression was used to analyse the relation between the potential prognostic value of hormones and metabolites and mastitis outbreak. Only the elevated (> or = 1.00 mmol/l) serum beta-hydroxybutyrate (BHB) levels predisposed the cows to mastitis in the subsequent 4 weeks. This prognostic value of BHB was significant only in GN + NDP mastitis and in cases caused by GP environmental pathogens, but not in S. aureus mastitis (odds ratio: 5.333, 3.600 and 1.333, respectively).

Concentrate feeding strategy in lactating dairy cows: metabolic and endocrine changes with emphasis on leptin

This study aimed to evaluate metabolic and endocrine adaptations to energy intake in multiparous Holstein cows (n = 90; mean 9434 kg energy-corrected milk yield/305 d) over the first 20 wk postpartum and to assess the association of leptin with metabolic, endocrine, and zootechnical traits. Concentrates were fed automatically for 24 h at 30% (C30) or 50% (C50) of total dry matter intake (DMI) from wk 1 to 10 postpartum and at linearly reduced amounts thereafter. Roughage was fed for ad libitum intake. The DMI was measured over 24 h; milk yield and body weight (BW), twice/d; milk composition, 4 times/wk; and milk acetone, weekly. Blood samples for determination of metabolite, hormone, and electrolyte concentrations and enzyme activities were obtained at wk 2 prepartum, and at wk 1 to 16 and at wk 20 postpartum from 0730 to 0900. Body condition scores (BCS) and backfat thickness were measured postpartum and during wk 1, 4, 8, 12, 16, and 20. Energy balance (EB) was considerably lower, but milk yield only slightly lower, in C30 than C50. Metabolic stress was more marked in C30 than C50, expressed by lower, glucose, insulin, insulin-like growth factor-1 (IGF-1), triiodothyronine, milk protein, and lactose concentrations, higher nonesterified fatty acid, beta-hydroxybutyrate, growth hormone, and milk acetone concentrations, and an accelerated decrease in BCS and backfat thickness. Nevertheless, C30 adapted successfully and thus maintained high milk yields despite negative EB. Leptin concentrations were lower in C30 than in C50 over the first 20 wk postpartum and were positively associated with BCS, EB, BW, cholesterol, albumin, insulin, and IGF-1; negatively associated with DMI and triiodothyronine; and were higher in cows calving in spring than in fall. Leptin is one among several factors involved in the regulation of energy metabolism and may be important for overall homeostatic and homeorhetic control of metabolism and thus for maintenance of performance.

Metabolic profiles and progesterone cycles in first lactation dairy cows

This study investigated the ovarian function, metabolic profiles and fertility in first lactation Holstein-Friesian dairy cows (mean 305 day milk yield: 7417+/-191kg, n=37). Reproductive profiles obtained from milk progesterone analysis were categorized into normal (n=17) and four abnormal profiles (delayed ovulation, DOV1, n=9; DOV2, n=2; persistent corpus luteum, PCL1, n=6; PCL2, n=4; 1: immediately post-calving, 2: subsequent cycles). Fifty-five percent of cows had abnormal profiles with half of these being categorized as DOV1. Fertility of DOV1 and DOV2 cows was reduced whereas PCL1 and PCL2 cows had similar reproductive competence to normal profile cows. DOV1 animals had higher milk energy values, lower energy balances, lower dry matter intakes (DMI) and greater body weight and body condition score (BCS) losses post-calving than normal profile animals. DOV1 animals also had lower insulin-like growth factor-I (IGF-I) and higher betahydroxybutyrate (BHB) concentrations and tended to have the lower insulin and glucose concentrations in the pre-service period than normal profile cows. All PCL animals had vulval discharges postpartum. Despite this, the DMI, body weight and BCS changes, IGF-I concentrations and fertility of PCL1 animals was similar to normal profile cows. In conclusion, the high prevalence of delayed ovulation post-calving (DOV1) in primiparous high yielding cows lasted long enough (71+/-8.3 days) to have a detrimental impact on fertility and was associated with significant physiological changes. This study did not establish any detrimental effects of PCL profiles on fertility or production parameters.

Time empty and ketone body status in the early postpartum period of dairy cows

This study aimed to assess the effect of ketone body status early postpartum on time empty in 74 multiparous dairy cows under field conditions. Animals were equally distributed across eight farms and were controlled by the same herd-fertility-monitoring programme. Cows were visited twice antepartum and six times postpartum at weekly intervals between 0530 and 0830 a.m. On these occasions, body condition scores and milk yields were measured, blood and milk samples were taken, cows were gynaecologically examined, and parameters of reproduction were recorded. Cows with a time empty of less or more than 80 days were classified as early and late conceiving cows (EC and LC, respectively). A time empty of 80 days results in calving-to-calving intervals of 1 year and classification based on this threshold value resulted in groups of equal size and equal distribution of EC and LC within farms. Ketone bodies measured were beta-hydroxybutyrate in blood and acetoacetate and acetone in blood and milk. Blood and milk ketone body concentrations, as well as the ratios of acetoacetate and acetone to beta-hydroxybutyrate, over the first 6 weeks postpartum were higher in LC than in EC, whereas plasma glucose and non-esterified fatty acids and milk fat, protein and urea concentrations did not exhibit clear differences between groups. Ketone body concentrations were as good predictors of time empty as ketone body ratios and might have practical impact in herd-fertility-monitoring programmes.

Use of threshold serum and milk ketone concentrations to identify risk for ketosis and endometritis in high-yielding dairy cows

OBJECTIVE

To use threshold concentrations of acetone and beta-hydroxybutyrate in milk and serum, respectively; identify risk for ketosis and endometritis; and assess analyses of blood and milk samples as predictors of risk for ketosis in high-yielding dairy cows.

ANIMALS

90 multiparous Holstein cows.

PROCEDURE

At intervals before and after parturition, blood samples were obtained for determination of glucose, nonesterified fatty acids, leptin, insulin, insulin-like growth factor-1, and beta-hydroxybutyrate concentrations. Samples of milk were obtained at similar intervals after parturition for determination of fat content and concentrations of acetone, protein, and lactose. Reproductive examination of each cow was performed weekly.

RESULTS

For each cow, threshold concentrations of acetone and beta-hydroxybutyrate were calculated as 75th and 90th percentiles of maximum postpartum concentrations of acetone in milk (0.40 and 0.87 mmol/L) and beta-hydroxybutyrate in serum (2.30 and 3.51 mmol/L). Significant decrease in milk production (442 to 654 kg of energy-corrected milk/305-day period per cow) was associated with acetone or beta-hydroxybutyrate in excess of threshold values. Milk acetone concentrations > 0.40 mmol/L were associated with 3.2 times higher risk for endometritis. Low plasma glucose, high serum beta-hydroxybutyrate, and high milk acetone concentrations during week 1 after parturition were indicators of increased risk for ketosis later during lactation.

CONCLUSIONS AND CLINICAL RELEVANCE

Determination of milk acetone concentration during the week after parturition may identify cows at risk for ketosis and endometritis; with appropriate interventions, development of disease and production losses may be reduced.

Estimation of energy balance at the individual and herd level using blood and milk traits in high-yielding dairy cows

This study aimed to estimate individual and herd-level energy balance (EB) using blood and milk traits in 90 multiparous high-yielding Holstein cows, held on a research farm, from wk 1 to 10 postpartum (p.p.) and to investigate the precision of prediction with successively decreased data sets simulating smaller herd sizes and with pooled samples. Dry matter intake, milk yield, and BW were measured daily from parturition through wk 10 p.p. Milk composition was determined 4 times per week, and milk acetone was measured weekly. Blood samples for the determination of metabolites, hormones, electrolytes, and enzyme activities were taken weekly from wk 1 to 10 p.p. between 0730 and 0900. Body condition scores and ultrasonic measurements of backfat thickness and fat depth in the pelvic area were evaluated in wk 1, 4, and 8 p.p. Concentrations of glucose, cholesterol, urea, insulin, insulin-like growth factor-1, triiodothyronine, and thyroxine (T4) in blood plasma and of lactose and urea in milk were positively correlated with EB, whereas concentrations of nonesterified fatty acids (NEFA), creatinine, albumin, beta-hydroxybutyrate, and growth hormone and enzyme activities in blood, and concentrations of fat, protein, fat:lactose ratio, and acetone in milk were negatively correlated with EB. Leptin concentration was not correlated to EB over the first 10 wk p.p. To estimate EB linear mixed-effects, models were developed by backward selection procedures. The most informative traits for estimation of EB were the fat:lactose ratio in milk and NEFA and T4 concentrations in blood. The precision of estimation of EB in individual cows was low. Using blood in addition to milk traits did not result in higher precision of estimation of herd-level EB, and decreasing sample sizes considerably lowered the precision of EB prediction. Estimation of overall mean herd-level EB over the first 10 wk p.p. using pooled samples was precise even with small sample sizes, but does not consider the level of EB in particular weeks. In conclusion, estimation of herd-level EB at individual weeks using milk traits only has practical implication with herd sizes of > or = 100 cows if calving is highly seasonal and of or = 400 cows if calving is uniformly distributed. Using blood in addition to milk traits does not improve precision of estimation of herd-level EB, regardless of sample size.

Body condition scores in dairy cows: associations with metabolic and endocrine changes in healthy dairy cows

Relationships between body condition scores (BCS), metabolic profiles and endocrine traits were investigated in 53 healthy Red Holstein cows. Cows were categorized into groups based on BCS ante-partum (a.p.: >3.25 or < 3.25) and on BCS losses during the first 8 weeks after calving (ABCS8 > 0.75 or < or = 0.75). Blood samples were collected 1 week before calving and every 2 weeks post-partum (p.p.). Cows with BCS a.p. >3.25 and deltaBCS < or = 0.75 were oldest and cows with BCS a.p. < or = 3.25 and deltaBCS < or = 0.75 were youngest. Cows with BCS > 3.25 a.p. and that lost > 0.75 BCS in the first 2 months of lactation exhibited signs of subclinical ketosis. If statistically adjusted for the effect of lactation number, average milk yield within the first 8 weeks p.p. and milk fat concentrations were similar between BCS groups, whereas milk protein concentrations differed significantly between BCS groups. Significant differences between groups were observed for blood plasma glucose, bilirubin, beta-hydroxybutyrate, non-esterified fatty acids and insulin concentrations. No differences were seen for albumin, urea, insulin-like growth factor-1, and 3.5.3'-triiodothyronine concentrations and for plasma activities of glutamate-oxalacetate transaminase, gamma-glutamyltransferase and glutamate dehydrogenase. There was a good agreement between BCS and profiles of metabolites and hormones related to energy metabolism in clinically healthy cows. Cows in good body condition a.p. had greater risks of metabolic problems because of excessive mobilization of body reserves. However, the metabolic status was best in cows with a BCS > 3.25 a.p.. if they did not lose much body condition p.p.

Bovine somatotropin dose titration in lactating dairy ewes. 3. Treatment interval

Seventy-four lactating dairy ewes were injected with recombinant bovine somatotropin (bST; sometribove) in a sustained-release formulation. Ewes received 0, 80, 160, or 240 mg of bST/14 d at the end of 2, 4, and 6 wk postlambing, after which injections were withheld for a 28-d period. Response of milk production to bST presented a positive linear contrast and a negative quadratic contrast. After the final injection of bST (d 0), an increase in daily milk production was observed until d +9. A continuous decrease followed with milk production returned to control levels on d +11, +18, and +20, for 80, 160, and 240 mg of bST/14 d. Milk protein content decreased gradually until d +8 before it returned to control levels on d +12, +14 and +14, for 80, 160, and 240 mg of bST/14 d. Levels of bST and IGF-I in plasma presented positive and highly significant linear contrasts and negative quadratics which were significant only for bST. Relative to the evolution of milk production, the evolution of IGF-I levels in plasma was more similar than that of bST, although the correlation of each measure with milk production was high and highly significant. It was concluded that the period between successive injections should be shorter the lower the dose employed; however, a 14-d period seemed to correspond correctly for the dosages and hormone formulation tested.

Metabolic, enzymatic and endocrine status in high-yielding dairy cows--Part 2

Pairs of 29 high-yielding (HC) dairy cows (> or = 45 kg/day reached at least once during lactation) and 29 corresponding control (CC) cows (with milk yields representing the average yield of the herds) were studied in 29 Swiss farms from March 1995 to September 1996. The hypothesis tested was that there are differences in metabolic, enzymatic and endocrine status between HC and CC cows. Cows were studied 2 weeks before and at 5, 9, 13, 17 and 40 weeks post-partum. Concentrations of metabolites, minerals and hormones and enzyme activities were in the normal range in both HC and CC cows. Changes in metabolic and endocrine traits in early lactation expressed insufficient energy intake, but were similar in both HC and CC cows. Homeorhetic and homeostatic control of metabolism in HC cows was thus adequate to adjust to and allow high milk yields. Under adequate husbandry, management and feeding conditions, metabolic disease problems in HC cows [10,500 kg energy-corrected milk (ECM)/lactation, peak yields of > or = 45 kg ECM/day] can be avoided.

First ovulation and ketone body status in the early postpartum period of dairy cows

The effect of ketone body status on occurrence of first ovulation during early lactation was assessed in 84 multiparous dairy cows under field conditions. Animals were equally distributed across 8 farms and were controlled by the same herd fertility monitoring program. Cows were visited twice antepartum and 6 times postpartum at weekly intervals between 5:30 and 8:30 AM. On these occasions, body condition scores and milk yields were measured, blood and milk samples were taken, cows were gynecologically examined, and parameters of reproduction were determined. The onset of first ovulation was specified by milk progesterone determination and rectal palpation. Cows starting postpartum ovarian cyclicity within or after 30 d were classified as early and late responders (ER and LR, respectively). Resumption of the estrous cycle within 30 d postpartum is considered optimal under practical conditions, and classification based on this threshold value resulted in groups of equal size and equal distribution of ER + LR cows within farms. Ketone bodies measured were beta-hydroxybutyrate in serum and acetoacetate and acetone in serum and milk. Blood serum and milk ketone body concentrations during the first 6 wk of lactation were higher in LR than in ER, whereas plasma glucose and nonesterified fatty acid and milk fat, protein and urea concentrations did not differ between groups. Maximal concentrations of ketone bodies from parturition to first ovulation were better predictors of the onset of the estrous cycle than mean or minimal concentrations over the same period. Milk acetone and serum beta-hydroxybutyrate concentrations provided the most reliable information with regard to resumption of ovarian activity of all ketone bodies.

Twenty-four-hour patterns of hormones and metabolites in week 9 and 19 of lactation in high-yielding dairy cows fed triglycerides and free fatty acids

Effects of feeding crystalline triglycerides (TGA), free fatty acids (FFA), and a starch-rich ration (STA) on metabolite and hormone concentrations in blood plasma were studied in high-yielding dairy cows over a 24-h period in week 9 and 19 of lactating. Energy-corrected milk production in the three groups was similar, but was lower in week 19 than in week 9. Energy and protein intakes were greater in week 9 than in week 19, but energy and protein balances in the three groups and in weeks 9 and 19 were similar. Plasma glucose and triglyceride concentrations were lower in week 9 than in week 19. In cows fed FFA, glucose concentrations were highest in week 9. Plasma triglyceride, phospholipid and cholesterol concentrations were highest, whereas beta-hydroxybutyrate concentrations were lowest in FFA-fed cows in weeks 9 and 19. Concentrations of insulin-like growth factor-I in week 19 were lower in cows fed TGA and FFA than in those fed the starch-rich ration. Post-prandial responses were usually greater following morning than afternoon meals. Fructosamine, albumin, urea, growth hormone, thyroxine, and 3,5,3'-triiodothyronine concentrations were similar in weeks 9 and 19 and were not influenced by dietary treatment or feeding times. In conclusion, there were distinct metabolic and endocrine effects of feeding TGA and FFA compared with STA and the concentrations as well as the 24-h changes of various metabolic and endocrine traits in weeks 9 and 19 of lactation were also different.

Insulin-dependent whole-body glucose utilization and insulin-responses to glucose in week 9 and week 19 of lactation in dairy cows fed rumen-protected crystalline fat or free fatty acids

Whole-body insulin-dependent glucose utilization and insulin responses to glucose in euglycemic-hyperinsulinemic clamps (EHGC) and in hyperglycemic clamps (HGC) were evaluated in high yielding dairy cows fed rumen-protected fat (triglycerides), free fatty acids, or a starch-rich ration (n = 5 per group) in Week 9 and Week 19 of lactation. The experiment was performed under conditions of nonsignificant differences in energy and protein balances in Week 9 and Week 19 and in the three groups. Basal (pre-infusion) concentrations of glucose were lower (P < 0.05) in Week 9 than in Week 19 of lactation and were higher (P < 0.05) in Week 9 in cows fed free fatty acids than in cows fed the starch-rich ration. In EHGC, glucose infusion rates were similar in Week 9 and Week 19 and in the different groups, indicating similar insulin-dependent glucose utilization. Furthermore, because insulin concentrations in EHGC in Week 9 and Week 19 and in the three groups were very similar, metabolic clearance rates of insulin were not affected by stage of lactation and feeding. In addition, insulin responses to the same glucose increments in HGC were not different in Week 9 and Week 19 and in the three groups, indicating that insulin secretion was not affected by stage of lactation and feeding. In conclusion, insulin secretion, insulin metabolic clearance rate, and insulin-dependent glucose utilization between Week 9 and Week 19 of lactation were stable. Furthermore, feeding rumen-protected triglycerides or free fatty acids did not significantly modify insulin secretion, insulin metabolic clearance rate and glucose-dependent glucose utilization compared with starch-rich feeding.

Longissimus dorsi muscle diameter, backfat thickness, body condition scores and skinfold values related to metabolic and endocrine traits in lactating dairy cows fed crystalline fat or free fatty acids

An experiment was performed using 18 dairy cows with > or = 2 lactations from parturition until week 20 of lactation to investigate the effects of feeding rumen-protected crystalline fat (group A) or free fatty acids (group B) compared with a control group not fed supplemental fat or fatty acids (group C). The feeding effects studied were those on milk yield and composition, body weight (BW), body conditions scores (BCS), skinfold values (a measure of subcutaneous fat tissue thickness), backfat thickness and longissimus dorsi muscle diameter (measured by ultrasound), as well as on blood plasma metabolic and endocrine traits. Fat and fatty-acid feeding reduced roughage intake. Net energy and protein balances during the first week of lactation were negative. Milk yield was similar in all groups, but concentrations of milk fat were reduced in group B and of milk protein in groups A and B. BW, BCS, skinfold value, backfat thickness and longissimus dorsi muscle diameter similarly decreased in all groups until weeks 8-12. Concentrations of glucose and fructosamine decreased transiently during early lactation, whereas levels of beta-hydroxybutyrate, urea, total protein and albumin increased reversibly and similarly in all groups. Concentrations of creatinine decreased similarly in all groups until week 4 and those of nonesterified fatty acids until week 12. Triglyceride concentrations increased continuously until week 18, whereas concentrations of phospholipid and cholesterol increased until week 10 and then remained elevated. Triglyceride, phospholipid and cholesterol concentrations were higher in group B than in groups A and C throughout the experiment. Concentrations of insulin, insulin-like growth factor-1, thyroxine and 3,5,3'-triiodothyronine started to increase after the first 6-8 weeks of lactation, while those of growth hormone were transiently low in week 16. None of the hormones exhibited group differences. In this study rumen-protected fat or fatty-acid supplementation failed to improve the energy and protein balances during early lactation and did not affect milk yield, likely due to decreased roughage intake. BCS, skinfold values and backfat ultrasound measurements of subcutaneous adipose tissue mass and of longissimus dorsi muscle diameter indicated mobilization of fat tissue and protein mobilization in early lactation and were mirrored by typical changes of metabolic and endocrine traits.

Role of the insulin-like growth factors and their binding proteins in lactation

Insulin-like growth factor (IGF)-I is thought to mediate a portion of the effects of bST on lactation in dairy cows. Serum concentrations of IGF-I are increased in lactating cows that were treated with bST, and IGF-I receptors are present in bovine mammary tissue. In addition, close arterial infusion of IGF-I into the mammary gland of goats increases milk yield. Little evidence exists to support a direct galactopoietic effect of IGF-I in ruminants. However, IGF-I is a potent mitogen for mammary epithelial cells and may also influence the inhibition of apoptosis of this cell type. The IGF are found in association with a family of individual binding proteins. The high affinity of the IGF for these proteins relative to the IGF receptor allows them to modulate IGF-I bioactivity in the mammary gland at the cellular level. Mammary epithelial cells synthesize multiple forms of IGF binding proteins, and one of these, IGF binding protein-3, is specifically regulated by the IGF. Stimulation of DNA synthesis by IGF-I is enhanced in bovine mammary epithelial cells that overexpress the IGF binding protein-3. These 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. Given the complexity of the interactions between the IGF and their binding proteins, more information is needed before the role of these growth factors in regulating growth, differentiation, and apoptosis of mammary epithelial cells is delineated.

Factors affecting body tissue mobilization in early lactation dairy cows. 2. Effect of dietary fat on mobilization of body fat and protein

Twenty-two multiparous Holstein cows were fed either a control diet or a control diet plus 3% added fat (dry matter basis) to determine the effect of added dietary fat on body tissue mobilization and milk production. Body composition measurements were taken using the D2O dilution technique at -2, 5, and 12 wk postpartum. Cows fed added fat produced 2.7 kg/d more milk than did those fed the control diet alone, but milk production, milk composition, and dry matter intake were not affected by diet. The maximum amount of body tissue loss occurred between -2 and 5 wk postpartum when cows fed both diets mobilized 46 kg of body fat and 12 kg of body protein. Between 5 and 12 wk postpartum, only small changes in both body protein and body fat were observed. Even though cows fed added fat showed a tendency toward reduced body fat mobilization (66 kg for cows fed the control diet vs. 37 kg for cows fed the control diet plus added fat) and increased body protein mobilization (4.8 kg for cows fed the control diet vs. 19.5 kg for cows fed the control diet plus added fat), the differences were not significant. Apparent differences in fat mobilization between diets might have been due to initial body fat stores (159 kg for cows fed the control diet vs. 126 kg for cows fed the control diet plus added fat). Across diets, one unit of change in body condition score corresponded to about 55 kg of empty body fat. Supplemental dietary fat did not reduce body tissue mobilization in early lactation.