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Effect of 1 α-hydroxycholecalciferol on calcium and phosphorus concentration in goat milk
Small Ruminant Research ELSEVIER
Small Ruminant
Research 21 (1996) 45-49
Effect of 1 a-hydroxycholecalciferol on calcium and phosphorus concentration in goat milk M. Ben Goumi a, M.-J. Davicco b, V. Coxam b, F. De La Farge ‘, J.-P. Barlet bT* a lnstitut Agro-Vht.&inuire Hussun II, Rabat, Morocco b NRA Clermont-Theix, F-63122 Ceyrut, France ’ CHU Toulouse-Rongueil, Toulouse, France Accepted 6 October
1995
Abstract Twelve small black Moroccan goats were used during the second month of their fourth lactation to compare the influence of an increase in plasma calcium (Ca) concentration induced by Ca infusion or by 1(Y-(OH) D, injection on milk Ca concentration. In four goats, Ca gluconate i.v. infusion (7 mg Ca kg-’ body weight) increased plasma Ca concentration from 10.3 k 0.04 to 13.3 $- 0.04 mg dl-’ (P < 0.05) without changing milk production and milk Ca and inorganic phosphorus (Pi) concentration. In five goats, 1 (Y-(OH) D, i.m. injection (3 X 0.5 pg kg-’ body weight) increased plasma Ca and 1,25-(OH), D concentrations from 10.7 f 0.03 to 13.2 + 0.05 mg dl- ’ (P < 0.05) and from 147 + 5 to 764 + 12 pg ml-’ (P < O.OOl), respectively, without changing daily milk production. Daily Ca and Pi secretion through the mammary gland increased from 1.22 + 0.09 g and 1.08 f 0.05 g before treatment to 1.45 k 0.05 g (P < 0.05) and to 1.30 4 0.05 g (P < O.OS>, respectively. No significant variation in plasma or milk Ca or Pi concentrations was observed in three control goats. These results indicate that in goats, as in cattle, plasma 1,25-(OH), D concentration may regulate Ca and Pi secretion
through milk. Keywords: Goat; Calcium; Phosphorus;
Milk;
1,2.5-Dihydroxycholecalciferol
1. Introduction
About 6 X lo6 goats are kept for meat and milk production in Morocco. The small black Moroccan breed is dominant. This local goat, with a low water turnover, can retain water upon rehydration but not store excess water after hyperhydration. These physiological adaptations enable this animal to survive and produce milk during periods of water shortage
* Corresponding
author. Fax: 73 62 44 50.
Elsevier Science B.V. SD1 0092 l-4488(95)008
19-5
(Hossaini-Hilali et al., 1994). During water deprivation, the calcium/inorganic phosphorus (Pi) ratio decreases in milk from ruminants adapted to water stress, owing to the decrease of calcium (Cal and increase of Pi (Yagil and Etzion, 1980; Yagil et al., 1986). Parathyroid hormone (PTH) and calcitonin (CT) do not regulate Ca and Pi concentrations in the milk of domestic ruminants. Neither parathyroidectomy nor intravenous infusion of chelating agents in the cow (Pischke and Stott, 1964) nor CT deficiency induced by thyroidectomy (with thyroxine supplementation) in the goat (Barlet, 1974) has any effect
46
M.B. Goumi et al./ Small Ruminant Research 21 (1996) 45-49
on milk Ca and Pi concentrations. Only PTH-related peptide, secreted by the lactating mammary gland (Ratcliffe et al., 1992), and 1, 25dihydroxycholecalciferol (1,25-(OH),D,), the active metabolite of vitamin D, (De Luca, 1974) has been shown to increase Ca secretion in the milk of goats (Barlet et al., 1992) and cows (Roux et al., 1979), respectively. In the work reported here, we have studied the influence of hypercalcaemia induced by Ca infusion or by 1 cY-hydroxycholecalciferol (1 a-(OH) D,), a synthetic derivative obtained from cholesterol, whose structure differs from that of 1,25-(OH), D, only by the absence of a hydroxyl group in position 25 (Holick et al., 1973) on Ca and Pi concentrations in Moroccan goat’s milk.
2. Materials
and methods
2.1. Goats and treatments Twelve 5-year-old female black Moroccan goats, weighing 29 k 1 kg (mean f SEM), were used during the second month of their fourth lactation. They were kept in an open yard of the Experimental Station of Tadla (Morocco), and water was available all the time. The goats were given a diet consisting of barley grain and luzeme hay, allowing a daily intake of 9 g Ca and 7 g Pi per animal. Half of the ration was given at 07:OO h and the other half at 17:OO h. The animals were hand milked at 07:OO h and 17:OO h, and immediately before each blood sampling. The volume of milk collected at each milking was measured, and a sample collected and frozen until analyzed. Thus measurement of milk production (mean daily production during the experimental period 0.95 f 0.25 1) and of Ca and Pi concentration in milk samples during and after treatment allowed the calculation of the quantities of these elements simultaneously secreted through the mammary gland. During Week 7 after parturition, four goats received, through the left jugular vein, one infusion of Ca gluconate (7 mg Ca kg-’ body weight, over a 30 min period, starting at 08:OO h). Five other goats were intramuscularly injected with 1 &OH) D, (3 X 0.5 pg kg-’ body weight, given at 08:OO h, and 12 h and 24 h later (Vetalfa, Teva Pharmaceutical Indus-
tries Ltd, Jerusalem, Israel). Three control goats received, in the same way, the same volume of solvent (propylene glycol; 3 X 15 ~1 kg-’ body weight). Serial heparinized blood samples were collected by puncture of the right external jugular vein. Plasma was collected after centrifugation and frozen until analysis. 2.2. Analysis Plasma 1,25-(OH), D concentrations were measured using a previously described radioreceptor assay (1,25_dihydroxyvitamin D 3H RRA kit; Incstar Corporation, Stillwater, MN, USA). The method is based on a calf thymus receptor that is specific for both 1,25-(OH), D, and 1,25-(OH), D, (Reinhardt et al., 1984). The assay involves a preliminary extraction and subsequent purification of vitamin D metabolites using a C ,,OH cartridge (Hollis, 1986). Quantitation was achieved using a non-equilibrium competitive protein binding assay. The addition of a dextran-coated charcoal suspension followed by incubation and centrifugation separates the bound and free hormones. The supernatant, which contains the bound hormone, was decanted into a scintillation vial and counted. Under our experimental conditions, the intra-assay and inter-assay variations were 7% and 8%, respectively. The sensitivity was 5 pg ml- ’ . In plasma and milk, Ca concentration was measured by atomic absorption spectrophotometry (Perkin Elmer 400) and Pi calorimetrically (Phosphore MonorCactif, Biotrol, Paris). Results are given as means &-SEM. The MannWhitney U test was used for comparisons between groups. Within each group, the values measured during or after treatment were compared to those measured before treatment using one-way analysis of variance.
3. Results Intravenous Ca infusion, which had no significant effect upon plasma Pi concentration, induced a significant increase in plasma Ca concentration, starting at the end of the infusion and lasting for at least 3 h (Fig. 1). Milk production as well as milk Ca and Pi concentrations did not vary significantly. Before
47
M.B. Goumi et al./ Small Ruminant Research 21 (1996) 45-49
treatment, the latter were 1.25 &-0.05 and 1.02 + 0.07 During the 2 h following Ca g 1-‘3 respectively. infusion, they were 1.27 f 0.07 and 1.05 f 0.09 g l- I, respectively (Fig. 1). 1 a-hydroxy vitamin D, injection had no significant effect upon milk production. However it induced a significant increase in both plasma and milk Ca and Pi concentrations (Fig. 2). This was associated with an increase in daily Ca and Pi secretion through the mammary gland from 1.22 f 0.09 g and 1.08 f 0.05 g before treatment to 1.45 f 0.05 g (P < 0.05) and 1.30 + 0.05 g (P < 0.05) 24 h later, respectively. This difference lasted for 6 days after the first injection. No significant variation in Ca and Pi mammary secretion was observed in control goats.
1.6~
4. Discussion Plasma 1,25-(OH), D concentrations measured in Moroccan goats before any treatment are similar to those reported in other domestic ruminants: around 50-60 pg ml-’ in ewes (Ross et al., 1980, Ross et al., 1989) and lo-160 pg ml-’ in cows and heifers (Barlet et al., 1981; Horst et al., 1983; Riad et al., 1987).
3;jr’r+-I -40 -20 0
20 40 60 SO 100 120140 160180200 220240
Fig. 1. Calcium (black circles) and inorganic phosphorus (black squares) concentrations in plasma and milk from four goats following Ca gluconate infusion (black bar) (meansf SEM; * P < 0.05; * * P < 0.01, comparison with values before treatment).
Hours from first injection
Fig. 2. Plasma 1,25dihydroxycholecalciferol (1,25-(OH), D), calcium (Ca) and inorganic phosphorus (Pi) and milk Ca and Pi concentrations in five goats (black circles) following I a-hydroxycholecalciferol treatment (arrows) (means f SEM; * P < 0.05; ’ * P < 0.01, comparison with controls (open circles).
Work presented demonstrates that an increase in plasma Ca concentration induced by i.v. Ca infusion had no significant effect upon milk Ca and Pi concentration (Fig. 1) or upon secretion of these elements through milk. However an increase in milk Ca and Pi concentration induced by 1 a-(OH) D, injection was associated with increased plasma Ca and Pi concentration. The daily milk production of each animal did not change before and after treatment. Thus, 1 (Y-(OH) D, significantly increased daily excretion of these minerals through the mammary gland. Since 1 cw-(OH) D, is rapidly metabolized (Holick et al., 19761, this would indicate that 1 (Y-(OH) D,, hydroxylated to 1, 25-(OH), D, in the liver, induced hypercalcaemia and hyperphosphataemia in goats (Fig. 21, as previ-
48
M.B. Gowni et al./ Small Ruminant Research 21 (1996) 45-49
ously reported in cattle (Barlet, 19751, and increased mammary Ca and Pi secretion. Similar results have already been reported in cows given Solanum glaucophyllum which contains a sterolglycoside of I,25 (OH), D (Roux et al., 1979). However the administration of high doses of 1, 25 (OH), D, to vitamin D-deficient rats or high doses of vitamin D to normal rats produces no change in milk Ca and Pi (Dostal et al., 1983). Nevertheless, in rats as in humans (Kumar et al., 1979), plasma 1, 25-(OH), D peaks during lactation (Halloran et al., 1979). Receptors for 1, 25-(OH), D are present in mammary tissue (Colston et al., 1980, Colston et al., 19861, and their number increases during lactation (Colston et al., 19881, so that 1, 25-(OH), D may regulate milk Ca and Pi in rats. This metabolite may have a similar role in lactating goats (Fig. 2). In conclusion, these results show that in goats as in cattle, plasma, 1, 25-(OH), D concentration may regulate Ca and Pi secretion through milk, by regulating milk Ca and Pi concentration without changing daily milk production.
References Barlet, J.-P., 1974. Role physiologique de la calcitonine chez la chtvre gestante ou allaitante (A physiological role for calcitonin in pregnant or lactating goats). Ann. Biol. Anim. B&hem. Biophys., 14: 447-457. Barlet, J.-P., 1975. Influence du 1 cu-hydroxycholecalciferol sur la calctmie et la phosphat6mie des bovins (Influence of 1 a-hydroxycholecalciferol on plasma calcium and phosphorous concentration in the bovine). C.R. Acad. Sci. Paris, 281 D: 1497-1500. Barlet, J.-P., Champredon, C., Coxam, V., Davicco, M.-J. and hormone-related peptide Tressol, J.-C., 1992. Parathyroid might stimulate calcium secretion into the milk of goats. J. Endocrinol., 132: 353-359. Barlet, J.-P., N’Guyen, T.M., Davicco, M.-J., Dardillat, C., Lefaivre, J. and Garabcdien, M., 1981. Plasma levels of vitamin D metabolites in the bovine species during the perinatal period. Reprod. Nutr. Develop., 21: 127-134. Colston, K.W., Berger, U., Wilson, P., Hadcocks, L., Naecm, I., Earl, H.M. and Coombes, R.C., 1988. Mammary gland 1,25dihydroxyvitamin D, receptor content during pregnancy and lactation. Mol. Cell. Endocrinol., 60: 15-22. Colston, K., Hirst, M. and Feldman, D., 1980. Organ distribution of the cytoplasmic 1,25-dihydroxycholecalciferol receptor in various mouse tissues. Endocrinology, 107: 1976-1922.
Colston, K., Wilkinson, J.R. and Coombes, R.C., 1986. 1,25-dihydroxyvitamin D, binding in estrogen-responsive rat breast tumor. Endocrinology, 119: 397-403. De Luca, H.F., 1974. Vitamin D: the vitamin and the hormone. Fed. Proc., 33: 2211-2219. Dostal, L.A., Boass, A. and Toverud, S.U., 1983. Effects of high doses of vitamin D, and 1,25-dihydroxyvitamin D, in lactating rats on milk composition and calcium homeostasis of the suckling pups. Endocrinology, 162: I63 1- 1638. Halloran, B.P., Barthell, EN. and De Luca, H.F., 1979. Vitamin D metabolism during pregnancy and lactation in the rat. Proc. Natl. Acad. Sci. USA, 76: 5549-5553. Holick, M.F., Semmler, E.J., S&noes, H.K. and De Luca, H.F., 1973. 1 a-hydroxy derivative of vitamin Da: a highly potent analog of I.25dihydroxy vitamin D,. Science, 180: 190-191. Holick, M.F., Tavela, T.E., Holick, S.A., Schnoes, H.K. and De Luca, H.F., Gallagher, B.M., 1976. Synthesis of 1 a-hydroxy [6-3~1 vitamin D, and its metabolism to 1cy,25-dihydroxy [6-3~1 vitamin D, in the rat. J. Biol. Chem., 251: 1020-1024. Hollis, B.W., 1986. Assay of circulating 1,25-dihydroxyvitamin D involving a novel single-cartridge extraction and purification procedure. Clin. Chem., 32: 2060-2063. Horst, R.L., Hove, K., Littledike, E.T., Reinhardt, T.A., Uskokovic, M.R. and Partridge, J.J., 1983. Plasma concentrations of 1,25-dihydroxyvitamin D, 1,24R,25-trihydroxyvitamm D3 and 1.25.26~trihydroxyvitamin D, after their administration to dairy cows. J. Dairy Sci., 66: 1455- 1460. Hossaini-Hilali, J., Benlamlih, S. and Dahlbom, K., 1994. Effects of dehydration, rehydration, and hyperhydration in the lactating and non-lactating black Moroccan goat. Comp. Biochem. Physiol., 109A: 1017-1026. Kumar, R., Cohen, W.R., Silva, P. and Epstein, F.H., 1979. Elevated 1,25-dihydroxyvitamin D plasma levels in normal human pregnancy and lactation. J. Clin. Invest., 63: 342-344. Pischke, L.D. and Stott, G.H., 1964. Relationship of bovine parathyroids to calcium and phosphorus in milk. J. Dairy Sci., 47: 698. Ratcliffe, W.A., Thompson, G.E., Care, A.D. and Peaker, M., 1992. Production of parathyroid hormone-related protein by the mammary gland of the goat. J. Endocrinol., 133: 87-93. Reinhardt, T.A., Horst, R.L., Orf. J.W. and Hollis, B.W., 1984. A microassay for 1,25-dihydroxyvitamin D not requiring high performance liquid chromatography. Application to clinical studies. J. Clin. Endocrinol. Metab., 58: 91-98. Riad, F. Lefaivre, J. and Barlet, J.-P., 1987. 1,25-dihydroxycholecalciferol regulates salivary phosphate secretion in cattle. J. Endocrinol., 112: 427-430. Ross, R., Care, A.D., Robinson, J.S., Pickard, D.W. and Weatherley, A.J., 1980. Perinatal 1,25-dihydroxycholecalciferol in the sheep and its role in the maintenance of the transplacental calcium gradient. J. Endocrinol., 87: 17P-18P. Ross, R., Halbert, K. and Tsang, R.C., 1989. Determination of the production and metabolic clearance rates of 1,25-dihydroxyvitamin D, in the pregnant sheep and its chronically catheterized fetus by primed infusion technique. Pediat. Res., 26: 633-638.
M.B. Goumi et al./ Small Ruminant Research 21 (1996) 45-49 Roux, R., Davicco, M.-J., Canillo, B.J. and Solanum glaucophyllum in pregnant cows. mineral composition and plasma calcium els in dams and newborn calves. Ann. Biophys., 19: 91-101.
Barlet, J.-P., 1979. Effect on colostrum and phosphorus levBiol. Anim. Bioch.
49
Yagil, R., Amir, H., Abu-Rabiya, Y. and Etzion, Z., 1986. Dilution of milk. A physiological adaptation of mammals to water stress? J. Arid Environ., 11: 243-247. Yagil, R. and Etzion, Z., 1980. Effect of drought condition on the quality of camel milk. J. Dairy Res., 47: 159-166.
Small Ruminant
Research 21 (1996) 45-49
Effect of 1 a-hydroxycholecalciferol on calcium and phosphorus concentration in goat milk M. Ben Goumi a, M.-J. Davicco b, V. Coxam b, F. De La Farge ‘, J.-P. Barlet bT* a lnstitut Agro-Vht.&inuire Hussun II, Rabat, Morocco b NRA Clermont-Theix, F-63122 Ceyrut, France ’ CHU Toulouse-Rongueil, Toulouse, France Accepted 6 October
1995
Abstract Twelve small black Moroccan goats were used during the second month of their fourth lactation to compare the influence of an increase in plasma calcium (Ca) concentration induced by Ca infusion or by 1(Y-(OH) D, injection on milk Ca concentration. In four goats, Ca gluconate i.v. infusion (7 mg Ca kg-’ body weight) increased plasma Ca concentration from 10.3 k 0.04 to 13.3 $- 0.04 mg dl-’ (P < 0.05) without changing milk production and milk Ca and inorganic phosphorus (Pi) concentration. In five goats, 1 (Y-(OH) D, i.m. injection (3 X 0.5 pg kg-’ body weight) increased plasma Ca and 1,25-(OH), D concentrations from 10.7 f 0.03 to 13.2 + 0.05 mg dl- ’ (P < 0.05) and from 147 + 5 to 764 + 12 pg ml-’ (P < O.OOl), respectively, without changing daily milk production. Daily Ca and Pi secretion through the mammary gland increased from 1.22 + 0.09 g and 1.08 f 0.05 g before treatment to 1.45 k 0.05 g (P < 0.05) and to 1.30 4 0.05 g (P < O.OS>, respectively. No significant variation in plasma or milk Ca or Pi concentrations was observed in three control goats. These results indicate that in goats, as in cattle, plasma 1,25-(OH), D concentration may regulate Ca and Pi secretion
through milk. Keywords: Goat; Calcium; Phosphorus;
Milk;
1,2.5-Dihydroxycholecalciferol
1. Introduction
About 6 X lo6 goats are kept for meat and milk production in Morocco. The small black Moroccan breed is dominant. This local goat, with a low water turnover, can retain water upon rehydration but not store excess water after hyperhydration. These physiological adaptations enable this animal to survive and produce milk during periods of water shortage
* Corresponding
author. Fax: 73 62 44 50.
Elsevier Science B.V. SD1 0092 l-4488(95)008
19-5
(Hossaini-Hilali et al., 1994). During water deprivation, the calcium/inorganic phosphorus (Pi) ratio decreases in milk from ruminants adapted to water stress, owing to the decrease of calcium (Cal and increase of Pi (Yagil and Etzion, 1980; Yagil et al., 1986). Parathyroid hormone (PTH) and calcitonin (CT) do not regulate Ca and Pi concentrations in the milk of domestic ruminants. Neither parathyroidectomy nor intravenous infusion of chelating agents in the cow (Pischke and Stott, 1964) nor CT deficiency induced by thyroidectomy (with thyroxine supplementation) in the goat (Barlet, 1974) has any effect
46
M.B. Goumi et al./ Small Ruminant Research 21 (1996) 45-49
on milk Ca and Pi concentrations. Only PTH-related peptide, secreted by the lactating mammary gland (Ratcliffe et al., 1992), and 1, 25dihydroxycholecalciferol (1,25-(OH),D,), the active metabolite of vitamin D, (De Luca, 1974) has been shown to increase Ca secretion in the milk of goats (Barlet et al., 1992) and cows (Roux et al., 1979), respectively. In the work reported here, we have studied the influence of hypercalcaemia induced by Ca infusion or by 1 cY-hydroxycholecalciferol (1 a-(OH) D,), a synthetic derivative obtained from cholesterol, whose structure differs from that of 1,25-(OH), D, only by the absence of a hydroxyl group in position 25 (Holick et al., 1973) on Ca and Pi concentrations in Moroccan goat’s milk.
2. Materials
and methods
2.1. Goats and treatments Twelve 5-year-old female black Moroccan goats, weighing 29 k 1 kg (mean f SEM), were used during the second month of their fourth lactation. They were kept in an open yard of the Experimental Station of Tadla (Morocco), and water was available all the time. The goats were given a diet consisting of barley grain and luzeme hay, allowing a daily intake of 9 g Ca and 7 g Pi per animal. Half of the ration was given at 07:OO h and the other half at 17:OO h. The animals were hand milked at 07:OO h and 17:OO h, and immediately before each blood sampling. The volume of milk collected at each milking was measured, and a sample collected and frozen until analyzed. Thus measurement of milk production (mean daily production during the experimental period 0.95 f 0.25 1) and of Ca and Pi concentration in milk samples during and after treatment allowed the calculation of the quantities of these elements simultaneously secreted through the mammary gland. During Week 7 after parturition, four goats received, through the left jugular vein, one infusion of Ca gluconate (7 mg Ca kg-’ body weight, over a 30 min period, starting at 08:OO h). Five other goats were intramuscularly injected with 1 &OH) D, (3 X 0.5 pg kg-’ body weight, given at 08:OO h, and 12 h and 24 h later (Vetalfa, Teva Pharmaceutical Indus-
tries Ltd, Jerusalem, Israel). Three control goats received, in the same way, the same volume of solvent (propylene glycol; 3 X 15 ~1 kg-’ body weight). Serial heparinized blood samples were collected by puncture of the right external jugular vein. Plasma was collected after centrifugation and frozen until analysis. 2.2. Analysis Plasma 1,25-(OH), D concentrations were measured using a previously described radioreceptor assay (1,25_dihydroxyvitamin D 3H RRA kit; Incstar Corporation, Stillwater, MN, USA). The method is based on a calf thymus receptor that is specific for both 1,25-(OH), D, and 1,25-(OH), D, (Reinhardt et al., 1984). The assay involves a preliminary extraction and subsequent purification of vitamin D metabolites using a C ,,OH cartridge (Hollis, 1986). Quantitation was achieved using a non-equilibrium competitive protein binding assay. The addition of a dextran-coated charcoal suspension followed by incubation and centrifugation separates the bound and free hormones. The supernatant, which contains the bound hormone, was decanted into a scintillation vial and counted. Under our experimental conditions, the intra-assay and inter-assay variations were 7% and 8%, respectively. The sensitivity was 5 pg ml- ’ . In plasma and milk, Ca concentration was measured by atomic absorption spectrophotometry (Perkin Elmer 400) and Pi calorimetrically (Phosphore MonorCactif, Biotrol, Paris). Results are given as means &-SEM. The MannWhitney U test was used for comparisons between groups. Within each group, the values measured during or after treatment were compared to those measured before treatment using one-way analysis of variance.
3. Results Intravenous Ca infusion, which had no significant effect upon plasma Pi concentration, induced a significant increase in plasma Ca concentration, starting at the end of the infusion and lasting for at least 3 h (Fig. 1). Milk production as well as milk Ca and Pi concentrations did not vary significantly. Before
47
M.B. Goumi et al./ Small Ruminant Research 21 (1996) 45-49
treatment, the latter were 1.25 &-0.05 and 1.02 + 0.07 During the 2 h following Ca g 1-‘3 respectively. infusion, they were 1.27 f 0.07 and 1.05 f 0.09 g l- I, respectively (Fig. 1). 1 a-hydroxy vitamin D, injection had no significant effect upon milk production. However it induced a significant increase in both plasma and milk Ca and Pi concentrations (Fig. 2). This was associated with an increase in daily Ca and Pi secretion through the mammary gland from 1.22 f 0.09 g and 1.08 f 0.05 g before treatment to 1.45 f 0.05 g (P < 0.05) and 1.30 + 0.05 g (P < 0.05) 24 h later, respectively. This difference lasted for 6 days after the first injection. No significant variation in Ca and Pi mammary secretion was observed in control goats.
1.6~
4. Discussion Plasma 1,25-(OH), D concentrations measured in Moroccan goats before any treatment are similar to those reported in other domestic ruminants: around 50-60 pg ml-’ in ewes (Ross et al., 1980, Ross et al., 1989) and lo-160 pg ml-’ in cows and heifers (Barlet et al., 1981; Horst et al., 1983; Riad et al., 1987).
3;jr’r+-I -40 -20 0
20 40 60 SO 100 120140 160180200 220240
Fig. 1. Calcium (black circles) and inorganic phosphorus (black squares) concentrations in plasma and milk from four goats following Ca gluconate infusion (black bar) (meansf SEM; * P < 0.05; * * P < 0.01, comparison with values before treatment).
Hours from first injection
Fig. 2. Plasma 1,25dihydroxycholecalciferol (1,25-(OH), D), calcium (Ca) and inorganic phosphorus (Pi) and milk Ca and Pi concentrations in five goats (black circles) following I a-hydroxycholecalciferol treatment (arrows) (means f SEM; * P < 0.05; ’ * P < 0.01, comparison with controls (open circles).
Work presented demonstrates that an increase in plasma Ca concentration induced by i.v. Ca infusion had no significant effect upon milk Ca and Pi concentration (Fig. 1) or upon secretion of these elements through milk. However an increase in milk Ca and Pi concentration induced by 1 a-(OH) D, injection was associated with increased plasma Ca and Pi concentration. The daily milk production of each animal did not change before and after treatment. Thus, 1 (Y-(OH) D, significantly increased daily excretion of these minerals through the mammary gland. Since 1 cw-(OH) D, is rapidly metabolized (Holick et al., 19761, this would indicate that 1 (Y-(OH) D,, hydroxylated to 1, 25-(OH), D, in the liver, induced hypercalcaemia and hyperphosphataemia in goats (Fig. 21, as previ-
48
M.B. Gowni et al./ Small Ruminant Research 21 (1996) 45-49
ously reported in cattle (Barlet, 19751, and increased mammary Ca and Pi secretion. Similar results have already been reported in cows given Solanum glaucophyllum which contains a sterolglycoside of I,25 (OH), D (Roux et al., 1979). However the administration of high doses of 1, 25 (OH), D, to vitamin D-deficient rats or high doses of vitamin D to normal rats produces no change in milk Ca and Pi (Dostal et al., 1983). Nevertheless, in rats as in humans (Kumar et al., 1979), plasma 1, 25-(OH), D peaks during lactation (Halloran et al., 1979). Receptors for 1, 25-(OH), D are present in mammary tissue (Colston et al., 1980, Colston et al., 19861, and their number increases during lactation (Colston et al., 19881, so that 1, 25-(OH), D may regulate milk Ca and Pi in rats. This metabolite may have a similar role in lactating goats (Fig. 2). In conclusion, these results show that in goats as in cattle, plasma, 1, 25-(OH), D concentration may regulate Ca and Pi secretion through milk, by regulating milk Ca and Pi concentration without changing daily milk production.
References Barlet, J.-P., 1974. Role physiologique de la calcitonine chez la chtvre gestante ou allaitante (A physiological role for calcitonin in pregnant or lactating goats). Ann. Biol. Anim. B&hem. Biophys., 14: 447-457. Barlet, J.-P., 1975. Influence du 1 cu-hydroxycholecalciferol sur la calctmie et la phosphat6mie des bovins (Influence of 1 a-hydroxycholecalciferol on plasma calcium and phosphorous concentration in the bovine). C.R. Acad. Sci. Paris, 281 D: 1497-1500. Barlet, J.-P., Champredon, C., Coxam, V., Davicco, M.-J. and hormone-related peptide Tressol, J.-C., 1992. Parathyroid might stimulate calcium secretion into the milk of goats. J. Endocrinol., 132: 353-359. Barlet, J.-P., N’Guyen, T.M., Davicco, M.-J., Dardillat, C., Lefaivre, J. and Garabcdien, M., 1981. Plasma levels of vitamin D metabolites in the bovine species during the perinatal period. Reprod. Nutr. Develop., 21: 127-134. Colston, K.W., Berger, U., Wilson, P., Hadcocks, L., Naecm, I., Earl, H.M. and Coombes, R.C., 1988. Mammary gland 1,25dihydroxyvitamin D, receptor content during pregnancy and lactation. Mol. Cell. Endocrinol., 60: 15-22. Colston, K., Hirst, M. and Feldman, D., 1980. Organ distribution of the cytoplasmic 1,25-dihydroxycholecalciferol receptor in various mouse tissues. Endocrinology, 107: 1976-1922.
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