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Hormonal changes during lactation in cows of three different breeds
Livestock Production Science, 27 ( 1991 ) 2 8 5 - 2 9 6 Elsevier Science Publishers B.V., A m s t e r d a m
285
Hormonal changes during lactation in cows of three different breeds D. Schams a, F. Graf b, B. Graule a, M.
A b e l e a a n d S. P r o k o p p a
alnstitut.fiir Physiologie, Siidd. Versuchs- und Forschungsanstalt fiir Milchwirtschaj~, Technische Universitiit Miinchen, 8050 Freising-Weihenstephan, Germany bInstitut j~r Tierzucht und Tierhygiene der Universitdt Miinchen. Munich, Germany ( Accepted 17 May 1990 )
ABSTRACT Schams, D., Graf, F., Graule, B., Abele, M. and Prokopp S., 199 I. Hormonal changes during lactation in cows of three different breeds. Livest. Prod. Sci., 27: 285-296. Changes of somatotropin (bST), insulin-like growth factor I (IGF-I), insulin (INS) and free fatty acids (NEFA), and milk yield were measured ante partum and during an entire lactation period in groups of dual-purpose cows of the German Fleckvieh ( FV ) and German Brown Swiss ( BS ) breeds and of German Black and White ( BW ) dairy type cows. In total, 26 cows were studied located on two farms. Blood was collected weekly (8 weeks ante partum (ap) until 40 weeks post partum ( p p ) ) and more frequently ( 10 h, 30 min intervals) at 6 and 2 weeks ap and Weeks 2, 4, 8, 12, 20 and 30 pp. Episodic secretion pattern was recorded only for bST. bST, NEFA and milk showed a clear increase after parturition in all three breeds. NEFA started to rise 2 weeks ante partum. In contrast, INS and IGF-I fell immediately post partum to significantly lower concentrations. As lactation progressed, all of the investigated plasma parameters returned to values seen in pregnancy. The three groups studied of FV, BS and BW cows exhibited significantly different values for bST, INS, IGF-I and milk yield during the first 8 weeks of lactation. NEFA concentrations were significantly higher in BW vs. FV and BS cows. The relation between bST and milk yield was positive and significant in BS cows ( r = 0.58 ). The elevation ofbST pp is due to an increase of episodic secretion pattern (baseline, peak frequency, peak amplitudes and rise of suprabasal peak secretion). Keywords: breeds: dairy cows; hormonal changes.
INTRODUCTION
The purpose of the study was to compare blood concentrations of the metabolic hormones bovine somatotropin (bST); insulin-like growth factor I (IGF-I), insulin (INS), and of free fatty acids (NEFA) ante partum and during an entire lactation period in dual-purpose cows German Fleckvieh (FV), German Brown Swiss (BS) and dairy type German Black and White cows (BW).
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It is assumed that bST is an important hormone for the control of lactation. Differences were found between beef and dairy cattle during peak lactation (Hart et al., 1975) and even within one breed. Selection for milk yield resuited in elevated levels for bST especially during peak lactation (Hart et al., 1978; Gorewit and Agyemang, 1983; Barnes et al., 1985; Kazmer et al., 1986; Bonczek et al., 1988 ). The significant differences in plasma concentrations of bST, insulin or NEFA at peak or mid-lactation between high and low yielding cows disappeared, when lactating beef and dairy cows with controlled dietary intake were subsequently compared, hen both genotypes experienced a similar degree of energy deficit, both groups lost similar amounts of live weight (Johnson and Hart, 1983 ). However, there is also some evidence of intrinsic differences in hormone secretion and in the responsiveness of tissues to energy deficit. Furthermore, more recent work with genetic lines of dairy cows indicates that selection for increased milk yield has been associated with changes in the in vitro responsiveness to lipolytic and lipogenic stimuli in adipose tissue samples during lactation (McNamara, 1989). A decrease of the anabolic hormones (insulin and IGF-I) supports the action of bST to mobilize fat tissue and inhibit lipogenesis. The presented studies should give further evidence for differences in hormonal parameters between dual purpose and dairy type cows. MATERIALS AND METHODS
Experimental animals In total 26 cows were used for the experiment located on two farms. Six German Fleckvieh and six German Black and White cows were used (belonging to the experimental farm of the Animal Breeding Department of the University of Munich in Schleil3heim ). Cows were in their second lactation. Forage (maize-silage and hay) was fed to meet nutritional requirements for ~ 15 kg daily milk production. Concentrates and supplements were fed according to milk yield ( 1 kg for 2.2 kg of milk) by means of transponder. Fourteen Brown Swiss cows were located on the experimental farm Veitshof of the Technical University of Munich in Weihenstephan. They were in their 2nd-9th lactation. They were kept in a free stall barn during the winter time with free access to maize and grass silage and hay ad libitum. Concentrate was given during milking in a double tandem milking parlor according to milk yield ( 1 kg for 2.2 kg milk exceeding 12 kg of milk). Animals went out on pasture day and night from May to September. Calving occurred between November and January. Milk was recorded daily on both farms.
Blood sampling Blood samples were taken from all cows once per week, always on the same day between 8 and 9 o'clock a.m. by needle puncture of the jugular vein (20
HORMONAL CHANGES D U R I N G LACTATION IN COWS OF THREE DIFFERENT BREEDS
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ml) beginning about 8 weeks ante partum (ap) until 40 weeks post partum (pp). Additionally, frequent blood samples (20 ml) from 17 cows were taken from a permanent cannula inserted into the jugular vein one day before, for 10 h at 30 min intervals during Weeks 2, 4, 8, 12, 20 and 30 pp and for the Fleckvieh and Black and White cows during Weeks 6 and 2 ap. Blood was transferred into tubes containing 0.2 ml of a 0.3 M EDTA (Merck Darmstadt, Germany) solution and plastic granulate, shaken, kept in ice water for 5 min and centrifuged for 15 min at 4 ° C at 4000 rpm. Plasma was pipetted into two tubes and kept frozen until analysis.
Analysis of hormones and metabolites bST was determined by RIA using a rabbit antiserum raised against bovine pituitary extracted somatotropin (USDA-bGH-B-1). This antiserum was highly specific and showed no cross-reactivity with other anterior pituitary hormones. Highly purified bST (USDA-bGH-I- 1 ) was used for iodination by the Iodogen (Pierce Chemicals, USA) method. Separation of bound and free hormones was completed using a double antibody technique. The antibody against rabbit gamma globulin was raised in a sheep. Sensitivity of the assay was 0.25-0.50 ng ml-1. The intra-assay coefficient of variation (CV) from control samples was < 9%. The inter-assay CV estimated from control samples of low, medium and high bST concentrations was on average 14%; USDAbGH-B-1 served as the reference preparation. IGF-I was determined by RIA after acid-ethanol extraction (Daughaday et al., 1980) of 50 ~tl blood plasma. Recombinant IGF-I (supplied by Amersham Co., England and Monsanto Co., USA) was used for iodination according to the lactoperoxidase (Boehringer, Mannheim, Germany) method (Marchalonis, 1969 ). Separation of bound and free hormones was clone by a combination of second antibody technique with 12% polyethylene-glycol. As reference preparation, synthetic IGF-I was used for calibration of a bovine plasma pool standard. The intra-assay CV and inter-assay CV was < 10% and < 16%, respectively. Insulin was determined by RIA. The antiserum was raised in a guinea pig against bovine insulin (Novo Co., Copenhagen, Denmark) and showed no cross reaction with IGF-I, IGF-II glucagon and C-peptide. A strong cross reaction (40%) was observed with proinsulin. Separation of bound and free hormones was performed by the double-antibody technique. The antibody against guinea pig gamma globulin was raised in a sheep. Highly purified bovine insulin (26.9 i.u. mg-1, Novo Co., Copenhagen, Denmark) was used for iodination by the iodogen method and served as reference preparation. The assay was validated by parallelism of standard and bovine plasma dilution curves, recovery experiments and reproducibility. The intra-assay CV was below 7% and the inter-assay CV obtained from different control samples averaged 8.4% ( range 6.5-12% ).
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Free fatty acids (NEFA) were determined by an enzyme-colour test obtained from Wako Chemicals, Neuss, Germany.
Statistical analysis The episodic secretion pattern was evaluated by P U L S A R (Merriam and Wachter, 1982 ) with some modifications for smoothing of profiles according to Cleveland (1979). Differences between groups were determined by the Wilcoxon multiple range test. Interactions between groups and effect of lactation stage were evaluated by analysis of variance and Scheffe's multiple range test (SAS program ). 40 ; A
milk
yield
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IGF-I
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' -S' '-'1~',i'' 'e~' i~'iii'2ii'2',i'zii'3'2'3i54'0 s.p. 1
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Fig. 1. Milk yield and mean plasma concentrations ofbST, 1GF-I, insulin and NEFA at weekly intervals 8 weeks ap until 40 weeks pp from six German Black and White cows.
HORMONAL CHANGES DURING LACTATION IN COWS OF THREE DIFFERENT BREEDS
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RESU LTS
Mean values per week are shown for bST, IGF-I, insulin, NEFA and milk yield for the three different breeds in Figs. 1-3. bST increased significantly in all three breeds after parturition for at least 4 weeks and decreased to a plateau around Week 18 pp. Circulating bST-concentrations were significantly higher in German Black and White cows. The pattern of change in IGF-I and insulin levels with advancing lactation was in opposition to that of bST in each breed (the decrease pp was significant in all three breeds). Levels of
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Fig. 2. Milk yield a n d m e a n plasma concentrations o f b S T , IGF-I, insulin a n d NEFA at weekly' intervals 8 weeks ap until 40 weeks pp from six G e r m a n Fleckvieh cows.
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Fig. 3. Milk yield and mean plasma concentrations ofbST, IGF-I, insulin and NEFA at weekly intervals 8 weeks ap until 40 weeks pp from 14 German Brown Swiss cows.
NEFA increased significantly in all breeds and paralleled the rise in bST and milk yield. The changes around parturition (means_+ SD from 8 weeks ap compared with 8 weeks pp), the statistical significance and the differences between the breeds are given in Table 1. Analysis of variance of 8 weeks ap and pp indicated significant influences of breed and differences between the ap and pp periods. Milk yield in kg day -1 during the first 8 weeks pp (22.5_+3.3 for FV; 34.2 _+4.0 for BW and 27.9 + 4.9 for BS) was significantly ( P < 0 . 0 5 ) different between breeds. The highest milk yield and increase of blood plasma concentrations for bST
HORMONAL CHANGES DURING LACTATION IN COWS OF THREE DIFFERENT BREEDS
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TABLE 1 Plasma concentrations o f bST, IGF-I, insulin and NEFA during 8 weeks before parturition (ap) and 8 weeks after parturition ( pp ) in three different breeds o f cows ( mean -+ SD ) Parameter
German Fleckvieh
G e r m a n Black & White
G e r m a n Brown Swiss
bST (/t 1-'
ap PP
2.9-+ 1.3"* 8.0_+4.4 a*
3.7-+ 1.9 16.9-+ 17.90*
4.2-+ 1.8 b 12.0-+ 7. I a**
IGF-1 (~g l -
ap pp
608 -+ 236 337_+ 134"*
473 _+225 b 220_+ 130 b*
432 _+ 163" 140_+ 54c**
Insulin (mU l-t)
ap pp
45.3 +_21.8 a 13.5+9.5 a*
40.2 +_20.1 a 9.9+_4.8 b*
18.2 +_ 15.6 b 7.8-+ 3.9 b**
NEFA (mmol 1- ~)
ap pp
0.11 +_0.07 0.35 _+0.30 "8*
0.16_+0.2l 0.51 +_0.44 a*
0.14-+ 0.11 0.28 -+ 0 . 1 9 b**
* P < 0.05; * * P < 0.01 statistically different. Different superscripts indicate statistical significance ( P < 0.05 ) between breeds.
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2 p.p. parturition
4 p.p.
12 p.p.
#225
30 p.p. weeks
Fig. 4. E p i s o d i c secretion p a t t e r n for bST at 6 a n d 2 weeks ap a n d 4, 12 a n d 30 weeks p p in t w o Fleckvieh (Nos. 45 a n d 43) a n d two Black a n d W h i t e (Nos. 227 a n d 225 ) cows.
and NEFA post partum was found in Black and White (dairy type ) followed by the Brown Swiss cows. In contrast, IGF-I and insulin levels were lowest in the Brown Swiss group. Time courses with frequent sampling were evaluated only for bST. Typical
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BW
FV
I
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m mm
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peak area equivalent
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overall mean
si 2
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8
12
20
30
weeks p.p.
4
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8
12 20 3 0 p,p.
parturition
Fig. 5. Concentrations o f b S T (mean + SEM ) after evaluation by P U L S A R program for overall mean, baseline, peak area equivalent, peak frequency and peak amplitude in Brown Swiss (n = 9 ) German Black and White ( n = 4) and German Fleckvieh ( n = 4 ) cows.
examples for the episodic secretion pattern are shown in Fig. 4. The means_+ SEM calculated by PULSAR for the overall mean, baseline, area of peak equivalents, peak frequency and peak amplitude are given in Fig. 5. There is a general tendency for all parameters (except peak frequency ) to be highest in the dairy type and lowest in Fleckvieh cows. There was no clear difference in peak frequency between groups, but there was a significant (Z 2 test, P<0.001 ) dependence on the stage of lactation in all three breeds. For the other parameters, analysis of variance indicated breed differences, but this difference was not significant due to the small number of animals per group. There was a significant influence ( P < 0 . 0 0 1 ) of the stage of lactation on all parameters in the three breeds. DISCUSSION
A similar pattern was observed in changes around parturition for all the parameters studied for the three different breeds. Growth hormone and NEFA showed a clear increase after parturition parallel to milk yield. Insulin and IGF-I were negatively related to those parameters. As lactation progressed, all of the investigated plasma parameters reached pregnancy values again. The
H O R M O N A L C H A N G E S D U R I N G LACTATION IN COWS O F T H R E E D I F F E R E N T BREEDS
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described changes for growth hormone are in agreement with observations made by Johke and Hodate ( 1977 ), Hart et al. ( 1978 ), Herbein et al. ( 1985 ), Kunz et al. (1985), Ronge and Blum (1988) and others. In contrast to bST, NEFA increased 1-2 weeks before parturition. This is in agreement with observations made by Giesecke et al. (1987a). The reason is not known, but could be related to the parallel decrease of insulin and IGF-I. These classical anabolic hormones tend to decrease at this time. This decrease is more pronounced after parturition and confirms data from Giesecke et al. (1987b) and Ronge and Blum (1988). The period of peak lactation is characterized as one of energy deficit, bST may enhance the availability of energy-yielding metabolites by increasing the rates of fat mobilization from adipose tissue (lipolysis) or by inhibition oflipogenesis as it was observed by Keys and Capuco (1985) under in vitro conditions. The energy deficit itself is the main regulator according to McNamara (1989) which stimulates the intensity of lipolysis and inhibition of lipogenesis, bST seems to be the main mediator. The physiological and biochemical mechanisms involved may include sympathetic nervous system activity, numbers of adrenergic receptors on adipocyte membranes, concentrations of counter-regulatory hormones such as insulin and IGF-I, adenosine responsiveness and activities of adenyl cyclase, protein kinase, and hormone-sensitive lipase. The lipolytic action of bST is supported by the steep decrease of insulin and IGF-I during the first week pp, the period of extreme energy deficit as shown in many studies. The level of energy seems to be the main trigger for release of somatotropin. For example, some of our non-pregnant Brown Swiss cows with a higher persistency of lactation curve, with daily milk yield of 28-30 kg day ~ at 10 months of lactation already had basal levels ofbST and NEFA. Calculation of energy balance was not made in our study but a positive energy balance at that time can be assumed since the animals gained body weight. In general there is a positive correlation between milk yield, bST and NEFA. But this is not always the case for individual cows. Food uptake and digestibility of food may be different in those animals resulting in a different energy balance and therefore different release pattern of bST, NEFA and anabolic hormones insulin and IGF-I. A direct comparison of the different breed groups is only possible for FV vs. BW. Body weight started to increase 10-13 weeks pp in FV and BW cows. The increase up to Week 40 pp was 9.3% (57 kg) for FV and 12.5% (74 kg) for BW cows. A balanced or slightly positive energy balance can be assumed. Nevertheless the difference between the dairy type and dual-purpose cow is striking at the beginning of lactation. Milk yield was quite similar (7348 vs. 7128 kg) for the 305-day lactation between BS vs. BW cows, but the shape of the curve was different. The higher milk yield at the beginning in BW cows correlated well with higher levels ofbST and NEFA and led us to assume that energy again is the main stimulator. Possibly the main difference between the
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dairy and dual-purpose type is a higher sensitivity of the dairy cow to react to a decrease of energy with a higher mobilizing capacity. The lower concentrations of IGF-I and insulin during the first 8 weeks pp in BS cows is indicative of a more pronounced negative energy balance, that was not totally reflected by bST and NEFA concentration. This assumption is supported in an experiment, where FV and BW cows were injected with a slow release formulation of bST at 9 weeks pp (unpublished observations). Similar peripheral bST concentrations were measured but BW cows responded with a higher increase of NEFA. The difference between the dairy and dual-purpose cow seems to be the domination of fat mobilization during peak lactation in dairy cows in contrast to a more pronounced anabolic regulation in dual-purpose cows. But this assumption needs further research and confirmation. The increase of bST post partum in all three breeds examined is a result of an increase of the episodic secretion pattern. As shown in Fig. 5 all parameters evaluated contribute to the elevation. The higher amplitudes and baseline levels dominate. The increased pulse frequency results in a higher peak area. The results confirm reports in Holstein cows by Phillips and Athanasiou (1978) and Bines et al. (1983). The decreasing tendency after 12 weeks for all parameters in our BW cows agrees with data by Vasilatos and Wangsness ( 1981 ) in Holstein cows. The episodic secretion pattern does not show a clear daily rhythm pattern and confirms data from Bines et al. ( 1983 ). In contrast, Hove and Blom ( 1973 ) reported a decrease ofbST in cows after feeding. The results further support the assumption that somatotropin is more responsible for the adaption on long term metabolic processes (homeorheses) as postulated by Bauman and Currie (1980). ACKNOWLEDGEMENT
This work was supported by a grant of the European Community. We gratefully acknowledge the supply of pituitary bGH preparations by USDA, Beltsville and NIAMKDD, Bethesda, USA; Dr. P. Gluckman, Auckland, New Zealand for the IGF-I antiserum and C.H. Li, San Francisco, USA for synthetic IGF-I. REFERENCES Barnes, M.A., Kazmer, G.W., Akers, R.M. and Pearson, R.E., 1985. Influence of selection for milk yield on endogenous hormones and metabolites in Holstein heifers and cows. J. Anim. Sci., 60: 271-284. Bauman, D.E. and Currie, W.B., 1980. Partitioning of nutrients during pregnancy and lactation: a review of mechanisms involving homeostasis and homeorhesis. J. Dairy Sci., 63: 15141529. Bines, J.A., Hart, I.C. and Morant, S.V., 1983. Endocrine control of energy metabolism in the cow: diurnal variations in the concentrations of hormones and metabolites in the blood plasma
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of beef and dairy cows. Horm. Metabol. Res., 15: 330-334. Bonczek, R.R., Young, C.W., Wheaton, J.E. and Miller, K.P., 1988. Responses of somatotropin, insulin, prolactin, and thyroxine to selection for milk yield in Holsteins. J. Dairy Sci., 71: 2470-2479. Cleveland, W.S., 1979. Robust logically weighted regression and smoothing scatterplots. J. Am. Stat. Assoc., 74: 829-836. Daughaday, W.H., Mariz, I.K. and Blethen, S.L., 1980. Inhibition of access of bound somatomedin to membrane receptor and immunobinding sites: a comparison of radioreceptor and radioimmunoassay ofsomatomedin in native and acid-ethanol-extracted serum. J. Clin. Endocrinol. Metab., 51:781-788. Giesecke, D., Meyer, J. and Loibl, G., 1987a. Lipidmobilisation und Fetts~iuremuster bei Kfihen mit hoher Milchleistung. In: D. Giesecke (Editor), Fortschritte d. Tierphysiol. u. Tierern/~hr., 18: 43-56. Giesecke, D., Meyer, J., Graf, F. and Kosak, F., 1987b. Stoffwechselbelastung, frei Fetts/iuren und Ketogenese bei KiJhen mit hoher Milchleistung. In: D. Giesecke (Editor), Fortschritte d. Tierphysiol u. Tierern~ihr., 18: 10-19. Gorewit, R.C. and Agyemang, K., 1983. Serum growth hormone concentrations in high and low producing Holstein cows over lactation. J. Dairy Sci., 66: Suppl. 1,234. Hart, I.C., Bines, J.A., Balch, C.C. and Cowie, A.T., 1975. Hormone and metabolite differences between lactating beef and dairy cattle. Life Sci., 16: 1285-1292. Hart, I.C., Bines, J.A., Morant, S.V. and Ridley, J.L., 1978. Endocrine control of energy metabolism in the cow: comparison of the levels of hormones (prolactin, growth hormone, insulin and thyroxine) and metabolites in the plasma of high- and low-yielding cattle at various stages of lactation. J. Endocrinol., 77: 333-345. Herbein, J.H., Aiello, R.J., Eckler, L.I., Pearson, R.E. and Akers, R.M., 1985. Glucagon, insulin, growth hormone, and glucose concentrations in blood plasma of lactating dairy cows. J. Dairy Sci., 68: 320-325. Hove, K. and Blom, A.K., 1973. Plasma insulin and growth hormone in dairy cows: diurnal variation and relation to food intake and plasma sugar and acetoacetate levels. Acta Endocrinol., 73: 289-303. Johke, T. and Hodate, K., 1977. Bovine serum prolactin, growth hormone, and triiodothyronine levels during late pregnancy and early lactation. Jpn. J. Zootech. Sci., 48: 772-776. Johnson, I.D. and Hart, I.C., 1983. Manipulation of milk with growth hormone. In: W. Haresign and D.J.A. Cole (Editors), Recent Advances in Animal Nutrition. Butlerworths, London, pp. 105-123. Kazmer, G.W., Barnes, M.A., Akers, R.M. and Pearson, R.E., 1986. Effect of genetic selection for milk yield and increased milking frequency on plasma growth hormone and prolactin concentration in Holstein cows. J. Anim. Sci., 63: 1220-1227. Keys, J.E. and Capuco, A.V., 1985. Effect of bovine growth hormone (bGH) on acetate incorporation by mammary and adipose tissue from Holsteins at different stages of first term gestation and lactation. J. Dairy Sci., 68: Suppl. 1,106. Kunz. P.L., Blum, J.W., Hart, I.C., Bickel, H. and Landis, J., 1985. Effects of different energy intakes before and after calving on food intake, performance and blood hormones and metabolites in dairy cows. Anim. Prod., 40:219-231. Marchalonis, J.J., 1969. An enzymic method for the trace iodination of immunoglobulins and other proteins. Biochem. J., 113: 299-305. McNamara, J.P., 1989. Regulation of bovine adipose tissue metabolism during lactation. 5. Relationships of lipid synthesis and lipolysis with energy intake and utilisation. J. Dairy Sci., 72: 407-418. Merriam, G.R. and Wachter, K.W., 1982. Algorithms for the study of episodic hormone secretion. Am. J. Physiol., 243:E310-E318.
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Phillips, R.W. and Athanasiou, V.N., 1978. Stability of plasma metabolites and hormones in lactating dairy cows. Am. J. Vet. Res., 39: 949-952. Ronge, H. and Blum, J.W., 1988. Somatomedin C and other hormones in dairy cows around parturition, in newborn calves and in milk. J. Anim. Physiol. Anita. Nutr., 60: 186-176. Vasilatos, R. and Wangsness, P.J., 1981. Diurnal variations in plasma insulin and growth hormone associated wilh two stages of lactation in high producing dairy cows. Endocrinology, 108: 300-304. RESUME Schams, D., Graf, F., Graule, B., Abele, M. et Prokopp, S., 199 I. Modifications hormonales au cours de la lactation chez les vaches de trois races. Livest. Prod. &'i., 27:285-296 (en anglais). On a suivi avant le v61age et au cours de la lactation enti6re les concentrations plasmatiques de la somatotropine (BST), des facteurs de croissance insuline-like (IGF-I), de l'insuline et des acides gras libres (AGE) et de la production laitibre chez des groupes de vaches des races allemandes Fleckvieh, Brune et Pie-Noire. On a suivi au total 26 vaches rOparties entre deux refines. Les 6chantillons de sang ont 6t6 pr61ev6s chaque semaine, de 8 semaines avant le v61age 40 semaines aprbs, et plus fr6quemment (a 30 minutes d'intervalle) aux semaines 6 et 2 avant v~lage ct 2, 4, 8, 12, 20 et 30 aprbs, Le profil de la s6cr6tion n'a 6t6 enregistr6 que pour la BST. Dans les trois races, les concentrations de la BST et des AGE et la quantit6 de lair ont nettement augment6 aprbs le v61age. La concentration des AGE a commenc6 ~ augmenter 2 semaines avant le vblage. Les concentrations de l'insuline et des IGF- 1 ont diminu6 aussit6t apres le v6lage jusqu'a des valeurs significativement plus faibles. Avec l'avancement de la lactation les concentrations des parambtres plasmatiques sont revenues aux niveau observ6s en gestation. On a observ6 des diff6rences significatives entre les trois races pour la BST, l'insuline, les IGF1 el la production laiti6re au cours des 8 premi6res semaines de lactation. Chez les Brunes, les AGL ont 616 significativement plus 61ev6s et la BST a 6t6 en corr61ation positive significative (r=0,58) avec la production laiti6re. L'augmentation de la concentration de la BST r6sulte d'une augmentation du niveau de base et de la fr6quence et dc l'amplitude des pics. KURZFASSUNG Schams, D., Graf, F., Graule, B., Abele, M. und Prokopp, S., 1991. Anderung der Hormonspiegel im Verlaufder Laktation in Gruppen yon drei verschiedenen Rinderrassen. Livest. Prod. Sd., 27:285-296 (aufenglisch). Die Hormone Somatotropin (bST), Insulin ahnlicher Wachstumsfaktor I (IGF-I) und Insulin (INS) sowie freie Fetts~iuren (NEFA) und die Milchleistung wurden in drei verschiedenen Rinderrassen (Deutsches Fleekvieh, Deutsches Braunvieh sowie Deutsche Schwarzbunte) beginnend vor der Geburt einschleiBlich der nachfolgenden Laktationsperiode gemessen. Insgesamt standen 26 Versuchskfihe, verteilt auf zwei Versuchsstationen zur Verftigung. Blutproben wurden w6chentlich (8 Wochen ante bis 40 Wochen post parlum) bzw. in frequenten Abst~inden in den Wochen 6, 2 ap sowie 2, 4, 8, 12, 20 und 30 pp aus der Vena jugularis entnommen. Die episodische Sekretion wurde nur ffir bST ermittelt. Nach der Geburt erfolgte mit der Milchleistung ein klarer Anstieg ftir bST und NEFA in alien drei Rassen. Im Gegensatz dazu fielen Insulin und IGF-I nach der Geburt signifikant ab. Mit Fortschreiten der Laktation stiegen bzw. fielen die Werte wieder aufdas ursprfingliche Niveau. Es bestanden signifikante Unterschiede zwischen den Rassen w~ihrend der ersten 8 Wochen pp. Eine signifikante Korrelation bestand zwischen bST und Milchleistung (r=0.58) bei den Braunviehkiihen. Der Anstieg des Wachstumshormons resultierte aus einer verst~irkten episodischcn Sekretion mit erh6hten Basalwerten, Gipfelamplitude und Frequenz der Episoden.
285
Hormonal changes during lactation in cows of three different breeds D. Schams a, F. Graf b, B. Graule a, M.
A b e l e a a n d S. P r o k o p p a
alnstitut.fiir Physiologie, Siidd. Versuchs- und Forschungsanstalt fiir Milchwirtschaj~, Technische Universitiit Miinchen, 8050 Freising-Weihenstephan, Germany bInstitut j~r Tierzucht und Tierhygiene der Universitdt Miinchen. Munich, Germany ( Accepted 17 May 1990 )
ABSTRACT Schams, D., Graf, F., Graule, B., Abele, M. and Prokopp S., 199 I. Hormonal changes during lactation in cows of three different breeds. Livest. Prod. Sci., 27: 285-296. Changes of somatotropin (bST), insulin-like growth factor I (IGF-I), insulin (INS) and free fatty acids (NEFA), and milk yield were measured ante partum and during an entire lactation period in groups of dual-purpose cows of the German Fleckvieh ( FV ) and German Brown Swiss ( BS ) breeds and of German Black and White ( BW ) dairy type cows. In total, 26 cows were studied located on two farms. Blood was collected weekly (8 weeks ante partum (ap) until 40 weeks post partum ( p p ) ) and more frequently ( 10 h, 30 min intervals) at 6 and 2 weeks ap and Weeks 2, 4, 8, 12, 20 and 30 pp. Episodic secretion pattern was recorded only for bST. bST, NEFA and milk showed a clear increase after parturition in all three breeds. NEFA started to rise 2 weeks ante partum. In contrast, INS and IGF-I fell immediately post partum to significantly lower concentrations. As lactation progressed, all of the investigated plasma parameters returned to values seen in pregnancy. The three groups studied of FV, BS and BW cows exhibited significantly different values for bST, INS, IGF-I and milk yield during the first 8 weeks of lactation. NEFA concentrations were significantly higher in BW vs. FV and BS cows. The relation between bST and milk yield was positive and significant in BS cows ( r = 0.58 ). The elevation ofbST pp is due to an increase of episodic secretion pattern (baseline, peak frequency, peak amplitudes and rise of suprabasal peak secretion). Keywords: breeds: dairy cows; hormonal changes.
INTRODUCTION
The purpose of the study was to compare blood concentrations of the metabolic hormones bovine somatotropin (bST); insulin-like growth factor I (IGF-I), insulin (INS), and of free fatty acids (NEFA) ante partum and during an entire lactation period in dual-purpose cows German Fleckvieh (FV), German Brown Swiss (BS) and dairy type German Black and White cows (BW).
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It is assumed that bST is an important hormone for the control of lactation. Differences were found between beef and dairy cattle during peak lactation (Hart et al., 1975) and even within one breed. Selection for milk yield resuited in elevated levels for bST especially during peak lactation (Hart et al., 1978; Gorewit and Agyemang, 1983; Barnes et al., 1985; Kazmer et al., 1986; Bonczek et al., 1988 ). The significant differences in plasma concentrations of bST, insulin or NEFA at peak or mid-lactation between high and low yielding cows disappeared, when lactating beef and dairy cows with controlled dietary intake were subsequently compared, hen both genotypes experienced a similar degree of energy deficit, both groups lost similar amounts of live weight (Johnson and Hart, 1983 ). However, there is also some evidence of intrinsic differences in hormone secretion and in the responsiveness of tissues to energy deficit. Furthermore, more recent work with genetic lines of dairy cows indicates that selection for increased milk yield has been associated with changes in the in vitro responsiveness to lipolytic and lipogenic stimuli in adipose tissue samples during lactation (McNamara, 1989). A decrease of the anabolic hormones (insulin and IGF-I) supports the action of bST to mobilize fat tissue and inhibit lipogenesis. The presented studies should give further evidence for differences in hormonal parameters between dual purpose and dairy type cows. MATERIALS AND METHODS
Experimental animals In total 26 cows were used for the experiment located on two farms. Six German Fleckvieh and six German Black and White cows were used (belonging to the experimental farm of the Animal Breeding Department of the University of Munich in Schleil3heim ). Cows were in their second lactation. Forage (maize-silage and hay) was fed to meet nutritional requirements for ~ 15 kg daily milk production. Concentrates and supplements were fed according to milk yield ( 1 kg for 2.2 kg of milk) by means of transponder. Fourteen Brown Swiss cows were located on the experimental farm Veitshof of the Technical University of Munich in Weihenstephan. They were in their 2nd-9th lactation. They were kept in a free stall barn during the winter time with free access to maize and grass silage and hay ad libitum. Concentrate was given during milking in a double tandem milking parlor according to milk yield ( 1 kg for 2.2 kg milk exceeding 12 kg of milk). Animals went out on pasture day and night from May to September. Calving occurred between November and January. Milk was recorded daily on both farms.
Blood sampling Blood samples were taken from all cows once per week, always on the same day between 8 and 9 o'clock a.m. by needle puncture of the jugular vein (20
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ml) beginning about 8 weeks ante partum (ap) until 40 weeks post partum (pp). Additionally, frequent blood samples (20 ml) from 17 cows were taken from a permanent cannula inserted into the jugular vein one day before, for 10 h at 30 min intervals during Weeks 2, 4, 8, 12, 20 and 30 pp and for the Fleckvieh and Black and White cows during Weeks 6 and 2 ap. Blood was transferred into tubes containing 0.2 ml of a 0.3 M EDTA (Merck Darmstadt, Germany) solution and plastic granulate, shaken, kept in ice water for 5 min and centrifuged for 15 min at 4 ° C at 4000 rpm. Plasma was pipetted into two tubes and kept frozen until analysis.
Analysis of hormones and metabolites bST was determined by RIA using a rabbit antiserum raised against bovine pituitary extracted somatotropin (USDA-bGH-B-1). This antiserum was highly specific and showed no cross-reactivity with other anterior pituitary hormones. Highly purified bST (USDA-bGH-I- 1 ) was used for iodination by the Iodogen (Pierce Chemicals, USA) method. Separation of bound and free hormones was completed using a double antibody technique. The antibody against rabbit gamma globulin was raised in a sheep. Sensitivity of the assay was 0.25-0.50 ng ml-1. The intra-assay coefficient of variation (CV) from control samples was < 9%. The inter-assay CV estimated from control samples of low, medium and high bST concentrations was on average 14%; USDAbGH-B-1 served as the reference preparation. IGF-I was determined by RIA after acid-ethanol extraction (Daughaday et al., 1980) of 50 ~tl blood plasma. Recombinant IGF-I (supplied by Amersham Co., England and Monsanto Co., USA) was used for iodination according to the lactoperoxidase (Boehringer, Mannheim, Germany) method (Marchalonis, 1969 ). Separation of bound and free hormones was clone by a combination of second antibody technique with 12% polyethylene-glycol. As reference preparation, synthetic IGF-I was used for calibration of a bovine plasma pool standard. The intra-assay CV and inter-assay CV was < 10% and < 16%, respectively. Insulin was determined by RIA. The antiserum was raised in a guinea pig against bovine insulin (Novo Co., Copenhagen, Denmark) and showed no cross reaction with IGF-I, IGF-II glucagon and C-peptide. A strong cross reaction (40%) was observed with proinsulin. Separation of bound and free hormones was performed by the double-antibody technique. The antibody against guinea pig gamma globulin was raised in a sheep. Highly purified bovine insulin (26.9 i.u. mg-1, Novo Co., Copenhagen, Denmark) was used for iodination by the iodogen method and served as reference preparation. The assay was validated by parallelism of standard and bovine plasma dilution curves, recovery experiments and reproducibility. The intra-assay CV was below 7% and the inter-assay CV obtained from different control samples averaged 8.4% ( range 6.5-12% ).
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Free fatty acids (NEFA) were determined by an enzyme-colour test obtained from Wako Chemicals, Neuss, Germany.
Statistical analysis The episodic secretion pattern was evaluated by P U L S A R (Merriam and Wachter, 1982 ) with some modifications for smoothing of profiles according to Cleveland (1979). Differences between groups were determined by the Wilcoxon multiple range test. Interactions between groups and effect of lactation stage were evaluated by analysis of variance and Scheffe's multiple range test (SAS program ). 40 ; A
milk
yield
30-
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IGF-I
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Insulin
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' -S' '-'1~',i'' 'e~' i~'iii'2ii'2',i'zii'3'2'3i54'0 s.p. 1
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Fig. 1. Milk yield and mean plasma concentrations ofbST, 1GF-I, insulin and NEFA at weekly intervals 8 weeks ap until 40 weeks pp from six German Black and White cows.
HORMONAL CHANGES DURING LACTATION IN COWS OF THREE DIFFERENT BREEDS
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RESU LTS
Mean values per week are shown for bST, IGF-I, insulin, NEFA and milk yield for the three different breeds in Figs. 1-3. bST increased significantly in all three breeds after parturition for at least 4 weeks and decreased to a plateau around Week 18 pp. Circulating bST-concentrations were significantly higher in German Black and White cows. The pattern of change in IGF-I and insulin levels with advancing lactation was in opposition to that of bST in each breed (the decrease pp was significant in all three breeds). Levels of
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Fig. 2. Milk yield a n d m e a n plasma concentrations o f b S T , IGF-I, insulin a n d NEFA at weekly' intervals 8 weeks ap until 40 weeks pp from six G e r m a n Fleckvieh cows.
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,
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Fig. 3. Milk yield and mean plasma concentrations ofbST, IGF-I, insulin and NEFA at weekly intervals 8 weeks ap until 40 weeks pp from 14 German Brown Swiss cows.
NEFA increased significantly in all breeds and paralleled the rise in bST and milk yield. The changes around parturition (means_+ SD from 8 weeks ap compared with 8 weeks pp), the statistical significance and the differences between the breeds are given in Table 1. Analysis of variance of 8 weeks ap and pp indicated significant influences of breed and differences between the ap and pp periods. Milk yield in kg day -1 during the first 8 weeks pp (22.5_+3.3 for FV; 34.2 _+4.0 for BW and 27.9 + 4.9 for BS) was significantly ( P < 0 . 0 5 ) different between breeds. The highest milk yield and increase of blood plasma concentrations for bST
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TABLE 1 Plasma concentrations o f bST, IGF-I, insulin and NEFA during 8 weeks before parturition (ap) and 8 weeks after parturition ( pp ) in three different breeds o f cows ( mean -+ SD ) Parameter
German Fleckvieh
G e r m a n Black & White
G e r m a n Brown Swiss
bST (/t 1-'
ap PP
2.9-+ 1.3"* 8.0_+4.4 a*
3.7-+ 1.9 16.9-+ 17.90*
4.2-+ 1.8 b 12.0-+ 7. I a**
IGF-1 (~g l -
ap pp
608 -+ 236 337_+ 134"*
473 _+225 b 220_+ 130 b*
432 _+ 163" 140_+ 54c**
Insulin (mU l-t)
ap pp
45.3 +_21.8 a 13.5+9.5 a*
40.2 +_20.1 a 9.9+_4.8 b*
18.2 +_ 15.6 b 7.8-+ 3.9 b**
NEFA (mmol 1- ~)
ap pp
0.11 +_0.07 0.35 _+0.30 "8*
0.16_+0.2l 0.51 +_0.44 a*
0.14-+ 0.11 0.28 -+ 0 . 1 9 b**
* P < 0.05; * * P < 0.01 statistically different. Different superscripts indicate statistical significance ( P < 0.05 ) between breeds.
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2 p.p. parturition
4 p.p.
12 p.p.
#225
30 p.p. weeks
Fig. 4. E p i s o d i c secretion p a t t e r n for bST at 6 a n d 2 weeks ap a n d 4, 12 a n d 30 weeks p p in t w o Fleckvieh (Nos. 45 a n d 43) a n d two Black a n d W h i t e (Nos. 227 a n d 225 ) cows.
and NEFA post partum was found in Black and White (dairy type ) followed by the Brown Swiss cows. In contrast, IGF-I and insulin levels were lowest in the Brown Swiss group. Time courses with frequent sampling were evaluated only for bST. Typical
292
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BW
FV
I
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m mm
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peak area equivalent
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31 o~
baseline !
overall mean
si 2
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8
12
20
30
weeks p.p.
4
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8
12 20 3 0 p,p.
parturition
Fig. 5. Concentrations o f b S T (mean + SEM ) after evaluation by P U L S A R program for overall mean, baseline, peak area equivalent, peak frequency and peak amplitude in Brown Swiss (n = 9 ) German Black and White ( n = 4) and German Fleckvieh ( n = 4 ) cows.
examples for the episodic secretion pattern are shown in Fig. 4. The means_+ SEM calculated by PULSAR for the overall mean, baseline, area of peak equivalents, peak frequency and peak amplitude are given in Fig. 5. There is a general tendency for all parameters (except peak frequency ) to be highest in the dairy type and lowest in Fleckvieh cows. There was no clear difference in peak frequency between groups, but there was a significant (Z 2 test, P<0.001 ) dependence on the stage of lactation in all three breeds. For the other parameters, analysis of variance indicated breed differences, but this difference was not significant due to the small number of animals per group. There was a significant influence ( P < 0 . 0 0 1 ) of the stage of lactation on all parameters in the three breeds. DISCUSSION
A similar pattern was observed in changes around parturition for all the parameters studied for the three different breeds. Growth hormone and NEFA showed a clear increase after parturition parallel to milk yield. Insulin and IGF-I were negatively related to those parameters. As lactation progressed, all of the investigated plasma parameters reached pregnancy values again. The
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described changes for growth hormone are in agreement with observations made by Johke and Hodate ( 1977 ), Hart et al. ( 1978 ), Herbein et al. ( 1985 ), Kunz et al. (1985), Ronge and Blum (1988) and others. In contrast to bST, NEFA increased 1-2 weeks before parturition. This is in agreement with observations made by Giesecke et al. (1987a). The reason is not known, but could be related to the parallel decrease of insulin and IGF-I. These classical anabolic hormones tend to decrease at this time. This decrease is more pronounced after parturition and confirms data from Giesecke et al. (1987b) and Ronge and Blum (1988). The period of peak lactation is characterized as one of energy deficit, bST may enhance the availability of energy-yielding metabolites by increasing the rates of fat mobilization from adipose tissue (lipolysis) or by inhibition oflipogenesis as it was observed by Keys and Capuco (1985) under in vitro conditions. The energy deficit itself is the main regulator according to McNamara (1989) which stimulates the intensity of lipolysis and inhibition of lipogenesis, bST seems to be the main mediator. The physiological and biochemical mechanisms involved may include sympathetic nervous system activity, numbers of adrenergic receptors on adipocyte membranes, concentrations of counter-regulatory hormones such as insulin and IGF-I, adenosine responsiveness and activities of adenyl cyclase, protein kinase, and hormone-sensitive lipase. The lipolytic action of bST is supported by the steep decrease of insulin and IGF-I during the first week pp, the period of extreme energy deficit as shown in many studies. The level of energy seems to be the main trigger for release of somatotropin. For example, some of our non-pregnant Brown Swiss cows with a higher persistency of lactation curve, with daily milk yield of 28-30 kg day ~ at 10 months of lactation already had basal levels ofbST and NEFA. Calculation of energy balance was not made in our study but a positive energy balance at that time can be assumed since the animals gained body weight. In general there is a positive correlation between milk yield, bST and NEFA. But this is not always the case for individual cows. Food uptake and digestibility of food may be different in those animals resulting in a different energy balance and therefore different release pattern of bST, NEFA and anabolic hormones insulin and IGF-I. A direct comparison of the different breed groups is only possible for FV vs. BW. Body weight started to increase 10-13 weeks pp in FV and BW cows. The increase up to Week 40 pp was 9.3% (57 kg) for FV and 12.5% (74 kg) for BW cows. A balanced or slightly positive energy balance can be assumed. Nevertheless the difference between the dairy type and dual-purpose cow is striking at the beginning of lactation. Milk yield was quite similar (7348 vs. 7128 kg) for the 305-day lactation between BS vs. BW cows, but the shape of the curve was different. The higher milk yield at the beginning in BW cows correlated well with higher levels ofbST and NEFA and led us to assume that energy again is the main stimulator. Possibly the main difference between the
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dairy and dual-purpose type is a higher sensitivity of the dairy cow to react to a decrease of energy with a higher mobilizing capacity. The lower concentrations of IGF-I and insulin during the first 8 weeks pp in BS cows is indicative of a more pronounced negative energy balance, that was not totally reflected by bST and NEFA concentration. This assumption is supported in an experiment, where FV and BW cows were injected with a slow release formulation of bST at 9 weeks pp (unpublished observations). Similar peripheral bST concentrations were measured but BW cows responded with a higher increase of NEFA. The difference between the dairy and dual-purpose cow seems to be the domination of fat mobilization during peak lactation in dairy cows in contrast to a more pronounced anabolic regulation in dual-purpose cows. But this assumption needs further research and confirmation. The increase of bST post partum in all three breeds examined is a result of an increase of the episodic secretion pattern. As shown in Fig. 5 all parameters evaluated contribute to the elevation. The higher amplitudes and baseline levels dominate. The increased pulse frequency results in a higher peak area. The results confirm reports in Holstein cows by Phillips and Athanasiou (1978) and Bines et al. (1983). The decreasing tendency after 12 weeks for all parameters in our BW cows agrees with data by Vasilatos and Wangsness ( 1981 ) in Holstein cows. The episodic secretion pattern does not show a clear daily rhythm pattern and confirms data from Bines et al. ( 1983 ). In contrast, Hove and Blom ( 1973 ) reported a decrease ofbST in cows after feeding. The results further support the assumption that somatotropin is more responsible for the adaption on long term metabolic processes (homeorheses) as postulated by Bauman and Currie (1980). ACKNOWLEDGEMENT
This work was supported by a grant of the European Community. We gratefully acknowledge the supply of pituitary bGH preparations by USDA, Beltsville and NIAMKDD, Bethesda, USA; Dr. P. Gluckman, Auckland, New Zealand for the IGF-I antiserum and C.H. Li, San Francisco, USA for synthetic IGF-I. REFERENCES Barnes, M.A., Kazmer, G.W., Akers, R.M. and Pearson, R.E., 1985. Influence of selection for milk yield on endogenous hormones and metabolites in Holstein heifers and cows. J. Anim. Sci., 60: 271-284. Bauman, D.E. and Currie, W.B., 1980. Partitioning of nutrients during pregnancy and lactation: a review of mechanisms involving homeostasis and homeorhesis. J. Dairy Sci., 63: 15141529. Bines, J.A., Hart, I.C. and Morant, S.V., 1983. Endocrine control of energy metabolism in the cow: diurnal variations in the concentrations of hormones and metabolites in the blood plasma
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of beef and dairy cows. Horm. Metabol. Res., 15: 330-334. Bonczek, R.R., Young, C.W., Wheaton, J.E. and Miller, K.P., 1988. Responses of somatotropin, insulin, prolactin, and thyroxine to selection for milk yield in Holsteins. J. Dairy Sci., 71: 2470-2479. Cleveland, W.S., 1979. Robust logically weighted regression and smoothing scatterplots. J. Am. Stat. Assoc., 74: 829-836. Daughaday, W.H., Mariz, I.K. and Blethen, S.L., 1980. Inhibition of access of bound somatomedin to membrane receptor and immunobinding sites: a comparison of radioreceptor and radioimmunoassay ofsomatomedin in native and acid-ethanol-extracted serum. J. Clin. Endocrinol. Metab., 51:781-788. Giesecke, D., Meyer, J. and Loibl, G., 1987a. Lipidmobilisation und Fetts~iuremuster bei Kfihen mit hoher Milchleistung. In: D. Giesecke (Editor), Fortschritte d. Tierphysiol. u. Tierern/~hr., 18: 43-56. Giesecke, D., Meyer, J., Graf, F. and Kosak, F., 1987b. Stoffwechselbelastung, frei Fetts/iuren und Ketogenese bei KiJhen mit hoher Milchleistung. In: D. Giesecke (Editor), Fortschritte d. Tierphysiol u. Tierern~ihr., 18: 10-19. Gorewit, R.C. and Agyemang, K., 1983. Serum growth hormone concentrations in high and low producing Holstein cows over lactation. J. Dairy Sci., 66: Suppl. 1,234. Hart, I.C., Bines, J.A., Balch, C.C. and Cowie, A.T., 1975. Hormone and metabolite differences between lactating beef and dairy cattle. Life Sci., 16: 1285-1292. Hart, I.C., Bines, J.A., Morant, S.V. and Ridley, J.L., 1978. Endocrine control of energy metabolism in the cow: comparison of the levels of hormones (prolactin, growth hormone, insulin and thyroxine) and metabolites in the plasma of high- and low-yielding cattle at various stages of lactation. J. Endocrinol., 77: 333-345. Herbein, J.H., Aiello, R.J., Eckler, L.I., Pearson, R.E. and Akers, R.M., 1985. Glucagon, insulin, growth hormone, and glucose concentrations in blood plasma of lactating dairy cows. J. Dairy Sci., 68: 320-325. Hove, K. and Blom, A.K., 1973. Plasma insulin and growth hormone in dairy cows: diurnal variation and relation to food intake and plasma sugar and acetoacetate levels. Acta Endocrinol., 73: 289-303. Johke, T. and Hodate, K., 1977. Bovine serum prolactin, growth hormone, and triiodothyronine levels during late pregnancy and early lactation. Jpn. J. Zootech. Sci., 48: 772-776. Johnson, I.D. and Hart, I.C., 1983. Manipulation of milk with growth hormone. In: W. Haresign and D.J.A. Cole (Editors), Recent Advances in Animal Nutrition. Butlerworths, London, pp. 105-123. Kazmer, G.W., Barnes, M.A., Akers, R.M. and Pearson, R.E., 1986. Effect of genetic selection for milk yield and increased milking frequency on plasma growth hormone and prolactin concentration in Holstein cows. J. Anim. Sci., 63: 1220-1227. Keys, J.E. and Capuco, A.V., 1985. Effect of bovine growth hormone (bGH) on acetate incorporation by mammary and adipose tissue from Holsteins at different stages of first term gestation and lactation. J. Dairy Sci., 68: Suppl. 1,106. Kunz. P.L., Blum, J.W., Hart, I.C., Bickel, H. and Landis, J., 1985. Effects of different energy intakes before and after calving on food intake, performance and blood hormones and metabolites in dairy cows. Anim. Prod., 40:219-231. Marchalonis, J.J., 1969. An enzymic method for the trace iodination of immunoglobulins and other proteins. Biochem. J., 113: 299-305. McNamara, J.P., 1989. Regulation of bovine adipose tissue metabolism during lactation. 5. Relationships of lipid synthesis and lipolysis with energy intake and utilisation. J. Dairy Sci., 72: 407-418. Merriam, G.R. and Wachter, K.W., 1982. Algorithms for the study of episodic hormone secretion. Am. J. Physiol., 243:E310-E318.
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Phillips, R.W. and Athanasiou, V.N., 1978. Stability of plasma metabolites and hormones in lactating dairy cows. Am. J. Vet. Res., 39: 949-952. Ronge, H. and Blum, J.W., 1988. Somatomedin C and other hormones in dairy cows around parturition, in newborn calves and in milk. J. Anim. Physiol. Anita. Nutr., 60: 186-176. Vasilatos, R. and Wangsness, P.J., 1981. Diurnal variations in plasma insulin and growth hormone associated wilh two stages of lactation in high producing dairy cows. Endocrinology, 108: 300-304. RESUME Schams, D., Graf, F., Graule, B., Abele, M. et Prokopp, S., 199 I. Modifications hormonales au cours de la lactation chez les vaches de trois races. Livest. Prod. &'i., 27:285-296 (en anglais). On a suivi avant le v61age et au cours de la lactation enti6re les concentrations plasmatiques de la somatotropine (BST), des facteurs de croissance insuline-like (IGF-I), de l'insuline et des acides gras libres (AGE) et de la production laitibre chez des groupes de vaches des races allemandes Fleckvieh, Brune et Pie-Noire. On a suivi au total 26 vaches rOparties entre deux refines. Les 6chantillons de sang ont 6t6 pr61ev6s chaque semaine, de 8 semaines avant le v61age 40 semaines aprbs, et plus fr6quemment (a 30 minutes d'intervalle) aux semaines 6 et 2 avant v~lage ct 2, 4, 8, 12, 20 et 30 aprbs, Le profil de la s6cr6tion n'a 6t6 enregistr6 que pour la BST. Dans les trois races, les concentrations de la BST et des AGE et la quantit6 de lair ont nettement augment6 aprbs le v61age. La concentration des AGE a commenc6 ~ augmenter 2 semaines avant le vblage. Les concentrations de l'insuline et des IGF- 1 ont diminu6 aussit6t apres le v6lage jusqu'a des valeurs significativement plus faibles. Avec l'avancement de la lactation les concentrations des parambtres plasmatiques sont revenues aux niveau observ6s en gestation. On a observ6 des diff6rences significatives entre les trois races pour la BST, l'insuline, les IGF1 el la production laiti6re au cours des 8 premi6res semaines de lactation. Chez les Brunes, les AGL ont 616 significativement plus 61ev6s et la BST a 6t6 en corr61ation positive significative (r=0,58) avec la production laiti6re. L'augmentation de la concentration de la BST r6sulte d'une augmentation du niveau de base et de la fr6quence et dc l'amplitude des pics. KURZFASSUNG Schams, D., Graf, F., Graule, B., Abele, M. und Prokopp, S., 1991. Anderung der Hormonspiegel im Verlaufder Laktation in Gruppen yon drei verschiedenen Rinderrassen. Livest. Prod. Sd., 27:285-296 (aufenglisch). Die Hormone Somatotropin (bST), Insulin ahnlicher Wachstumsfaktor I (IGF-I) und Insulin (INS) sowie freie Fetts~iuren (NEFA) und die Milchleistung wurden in drei verschiedenen Rinderrassen (Deutsches Fleekvieh, Deutsches Braunvieh sowie Deutsche Schwarzbunte) beginnend vor der Geburt einschleiBlich der nachfolgenden Laktationsperiode gemessen. Insgesamt standen 26 Versuchskfihe, verteilt auf zwei Versuchsstationen zur Verftigung. Blutproben wurden w6chentlich (8 Wochen ante bis 40 Wochen post parlum) bzw. in frequenten Abst~inden in den Wochen 6, 2 ap sowie 2, 4, 8, 12, 20 und 30 pp aus der Vena jugularis entnommen. Die episodische Sekretion wurde nur ffir bST ermittelt. Nach der Geburt erfolgte mit der Milchleistung ein klarer Anstieg ftir bST und NEFA in alien drei Rassen. Im Gegensatz dazu fielen Insulin und IGF-I nach der Geburt signifikant ab. Mit Fortschreiten der Laktation stiegen bzw. fielen die Werte wieder aufdas ursprfingliche Niveau. Es bestanden signifikante Unterschiede zwischen den Rassen w~ihrend der ersten 8 Wochen pp. Eine signifikante Korrelation bestand zwischen bST und Milchleistung (r=0.58) bei den Braunviehkiihen. Der Anstieg des Wachstumshormons resultierte aus einer verst~irkten episodischcn Sekretion mit erh6hten Basalwerten, Gipfelamplitude und Frequenz der Episoden.