HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Valk, H. Articles by Beynen, A. C. Search for Related Content PubMed PubMed Citation Articles by Valk, H. Articles by Beynen, A. C.

Influence of Phosphorus Intake on Excretion and Blood Plasma and Saliva Concentrations of Phosphorus in Dairy Cows

H. Valk^*, L. B. J. ebek^* and A. C. Beynen^*,

^* ID TNO Animal Nutrition P.O. Box 65, 8200 AB Lelystad, The Netherlands
Department of Nutrition, Faculty of Veterinary Medicine P.O. Box 80.152, 3508 TD Utrecht, The Netherlands

Corresponding author:
H. Valk; e-mail:
h.valk{at}id.dlo.nl.

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS ACKNOWLEDGEMENTS REFERENCES

 
Phosphorus (P) balance, and blood plasma P and saliva P concentrations were measured in multiparous dairy cows through two lactations and two dry periods. The cows were fed three amounts of P at either 100, 80 or 67% of the Dutch P recommendation, actually resulting in dietary P concentrations of 3.2 to 3.9, 2.6 to 2.9 and 2.2 to 2.6 g P/kg dry matter during lactation for the three treatments, respectively. On the basis of plasma P values as low as 0.9 mmol/l and saliva P values as low as 5.1 mmol/l during the second lactation period within the experiment, the 67% group was considered to be deficient in P. By decreasing milk production, and thus lowering P losses with milk, P retention in the 67% group remained near zero. The P supply with the 80% ration was considered to be just sufficient. At high milk yield and marginal dietary P concentrations, plasma P and saliva P concentrations were decreased. The higher P intake in high-compared with low-producing cows resulted in a constant absolute fecal P excretion, due to the fact that the apparent P digestibility was raised with increasing milk yield. There was a direct relationship between milk P output and the percentage of apparent P digestibility for individual animals.

Key Words: phosphorus • blood plasma • dairy cow

Abbreviation key: P67 = dietary P at 67% of the requirement, P80 = dietary P at 80% of the requirement, P100 = dietary P at 100% of the requirement

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS ACKNOWLEDGEMENTS REFERENCES

 
From an environmental point of view, an efficient use of ingested phosphorus (P) by dairy cows is important to minimize fecal P output and, as a result, P losses to the environment. Lowering P intake can reduce P excretion, but diets for dairy cows must contain sufficient P to meet the requirement for milk production (Call et al., 1987). For the assessment of P requirements of dairy cows, both results from controlled feeding trials and knowledge of P metabolism is required (Valk and Beynen, 2002). Under normal conditions, urinary P excretion is negligible and, therefore, the P balance of dairy cows is determined by P intake, intestinal absorption and secretion with milk (Valk et al., 2000). Milk P output is directly related to milk yield, as milk P concentration is constant (AFRC, 1991; GfE, 1993; NRC, 2001). Fecal P essentially depends on the amount of P intake (Ternouth, 1989; Khorasani et al., 1997). Fecal P is of exogenous or endogenous origin. The amount of unabsorbed dietary P is relatively low when animals are fed below their P requirement (Koddebusch and Pfeffer, 1988). The endogenous fecal P excretion is variable (McDowell, 1992) and consists of inevitable losses and a variable fraction (Spiekers et al., 1993). The inevitable losses are the sum of P in microbial residues, sloughed cells, and digestive secretions and are assumed to equal 1.0 g per kg DMI (Spiekers et al., 1993). Scott et al. (1995) suggested that total endogenous fecal P excretion depends more on P intake than on DMI. Endogenous fecal P under a P-depleted situation (variable P fraction = 0) mainly originates from the salivary glands, which form the main route for ruminants to excrete excess ingested P (Valk et al., 2000). The amount of salivary P is the product of saliva output and saliva P content. Thus, at similar feed compositions, DMI and milk yield differences in P intake will lead to differences in salivary P contents, causing differences in fecal endogenous P losses. Most of our knowledge concerning P metabolism in ruminants originates from studies with sheep. Quantitative extrapolation of sheep data to cattle is fraught with uncertainty. To assess P requirements of the dairy cow, data on this species are required.

The objective of these measurements within the long-term trial was to study fecal P excretion by dairy cows offered marginal amounts of dietary P. In addition, information is needed on how fecal P excretion reacts to P intake in early, mid, or late lactation or during the nonlactating period before parturition. Therefore, P balances were measured within the framework of the long-term feeding trial described earlier by Valk and ebek (1999). It was anticipated that P retention would become negative when animals are deficient in P. In addition, the P concentrations in plasma and saliva were determined as potential indicators of the P status. Three amounts of P intake were evaluated, and apart from the P balances, the concentrations of P in saliva and plasma were determined through two lactations and two dry periods. Part of the data thus obtained was used to quantify P metabolism in dairy cows and to assess the P requirement using the factorial method.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS ACKNOWLEDGEMENTS REFERENCES

 
During the performance trial described by Valk and ebek (1999), which lasted from calendar wk 3 of 1996 until wk 43 of 1997, nine balance studies were carried out (Table 1). During each 2-wk balance study, P intake, fecal P, and milk P were measured quantitatively. During four balance periods (1, 3, 5 and 9 [Table 1]) urinary P excretion was quantified as well. Twenty-four multiparous Holstein-Friesian dairy cows were used, which were expected to go through different stages of lactation and dry periods (Table 1). The cows were allocated on the basis of age, calving date, milk yield, and milk composition to six blocks of four cows each and, within blocks, then were allotted to three treatments. Experimental diets were obtained by offering concentrates with different P contents in addition to a basal diet.

View this table: [in this window] [in a new window]   Table 1. Schedule of periods during which the P balance studies were carried out within the framework of the feeding trial described by Valk and ebek (1999). The stage of lactation of the cows and the composition of the basal diets offered during the balance periods are indicated.

Valk and ebek (1999)

Valk and ebek, 1999

Fecal P excretion was measured on the basis of quantitative collection of the feces during three consecutive days (Tuesday, Wednesday, and Thursday) in each week of the 2-wk periods. Fecal output was collected quantitatively for each cow, placed in a 100-l container and weighed, mixed, and sampled proportionally (5% sample) when the container was loaded to 75%. Fecal samples were pooled to yield one sample per cow per week and were analyzed for DM, ash, and P content. For the statistical analysis the mean of the two consecutive weeks per cow was used. During four periods, every urine drain was collected manually in plastic buckets from 9 cows (3 per treatment), weighed, and sampled proportionally during a 24-h period. Finally, all samples were pooled to yield one sample per cow per day and were analyzed for P.

Cows were milked twice daily, and milk yield was recorded at each milking. During the balance periods, milk samples were taken during a.m. and p.m. milkings on three consecutive days each week and were then analyzed for P content. Total P was determined by atomic absorption spectrophotometry in ashed samples after dissolving in 1 M nitric acid and after treatment with a molybdovanate reagent (ISO 6491). Detailed information on feed sampling and chemical analyses is given by Valk and ebek (1999).

Prior to each balance study, blood and saliva samples were taken from individual cows once per period. Blood was sampled from the jugular vein into heparinized tubes and centrifuged for 10 min to obtain plasma which was stored at –20°C until analysis. Blood samples were analyzed for P. Saliva samples were taken with a sponge held against the opening of the parotid gland. For a period of 2 hr before sampling, cows were not allowed to eat, in order to avoid contamination of the saliva samples by remaining feed in the mouth. Saliva samples were analyzed for P and sodium. Sodium was analyzed to check any contamination of the saliva sample by feed residues. If sodium concentrations were too high (i.e., >200 mmol/l), these observations were removed from the analysis.

Statistical Analyses
The results for the dry cows in balance periods 4 and 5 were combined for those cows that were nonlactating in both periods. Statistical analysis was done for the three balance periods of lactation 1 (Table 1), for one data set for dry period 1, and for the first two balance periods during the early stage of the next lactation (Lactation 2). Immediately after balance period 7, the cows on treatment P67 developed a marked reduction in milk yield, as described Valk and ebek (1999) and Valk et al. (1999). Due to those problems and to avoid general health problems with these cows, treatment P67 was changed to P80 in order for the cows to recover. Results of these recovered cows were not taken into account in the statistical analysis. Therefore, for balance periods 8 and 9 only the differences between P100 and the original P80 group were analyzed statistically. For balance period 8, statistical analysis also was done on a low- versus high-producing group of cows (8_high and 8_low). Differences between treatments also were analyzed statistically for cows while in their second dry-off period (Dry 2).

Daily P intake, milk P, fecal P, and P retention were calculated per cow per period as a mean of the observed results during the period of 2 wk. These parameters and the concentrations in saliva and plasma were analyzed for treatment effects per period by linear regression using the following statistical model:

where µ = mean, _i = mean for block i (only for period 1 and 2), ß_j = effect of P treatment j, and _ij = variation within a block. Statistical analysis was carried out using Genstat (3). Treatment means and slopes of linear regression lines in graphs were compared by Student’s t test. The level of statistical significance was set at P < 0.05.

	RESULTS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS ACKNOWLEDGEMENTS REFERENCES

 
P Balance and Apparent Digestibility
No effect of dietary P on DMI or apparent digestible DM was observed (Tables 2 and 3). In most periods, fecal P decreased significantly with decreasing P intakes. The difference in fecal P output reflected the difference in P intake because, except for periods 6 and 7, there was no significant effect of dietary P on milk P output. In period 1, P retention for cows fed on diet P67 was significantly lower than that for cows given the other treatments. In the next period, the P retention on P100 was significantly higher than on the other treatments. At the end of Lactation 1 (period 3) and for the subsequent dry-off period there were no significant differences in P retention between the treatments. During lactation 2 (periods 6, 7, and 8), P retention in cows fed on diet P100 was about 5 g higher than for those on the other treatments. However, due to the small number of cows, only the difference during period 7 was statistically significant. Only for period 9, a significant difference in urinary P content between the P100 and P80 groups was observed. The apparent P digestibility varied from 42.4% (P100 group, period 2) to 66.0% (P80 group, period 8_high) and increased significantly during periods 2 and 3 between the highest and the lowest P treatments. For the periods of Lactation 2, the differences in apparent P digestibility did not reach statistical significance (P = 0.05).

	DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS ACKNOWLEDGEMENTS REFERENCES

 
Two weeks after the start of the experiment and at wk 20 of lactation (Table 2, Lactation 1, period 1), P retention of the cows offered the P67 ration was highly negative (–6.8 g P/cow daily). Presumably, for the cows offered P67, the absorption process was not yet fully adapted to the low amount of P intake. Fecal P output was high in relation to the level of P intake, indicating that the absorption process was not yet regulated in response to the low input of P. The P apparently was mobilized from body reserves to compensate for the excretion of P in milk and feces. It is not likely that P was mobilized from the bones because mobilization is not activated within a period of 2 wk of feeding P-depleted rations (Annenkov, 1982). However, P may have been mobilized from soft organs and tissues. During period 2 of Lactation 1, P retention for all three groups was positive, due to the lower milk P output and to adaptation of P absorption process in the P67 group. It can be speculated that true P absorption in the P67 group was not changed, but that the pool of P in the gut was reduced due to the low input via feed and saliva. As a consequence, the amount of P in feces declined, resulting in a higher apparent digestibility (Table 2). Compared with P100, the P80 group had lower fecal P output as a result of lower P intake, with similar milk P output and P balance during all of the three balance periods in Lactation 1, suggesting that dietary P can be reduced from 100 to 80% of the Dutch standard. In other words, mobilization of P apparently did not occur when P intake of the cows was reduced from 100 to 80% of the Dutch P recommendation. During the first dry period, P retention was positive, indicating that the lowest P intake (15.5 g/day) was enough to meet the requirement of dry pregnant cows. However, the need for fetal growth during the last months of pregnancy is about 4 g/day (Netherlands Committee on Mineral Nutrition, 1973). In our trial, the mean retention by the P100 group was 2.9 g/day and in the P67 group it was 0.8 g/day, pointing to redistribution of P in the body of the pregnant cows in the latter group. These data are consistent with the assessment by NRC (2001) that the maintenance requirement for P is 1.0 g/kg of DMI and the gestation requirement averages 4 g/d during the last 60 d of pregnancy.

During lactation 2 (Table 3), P retention could only be compared between the P100 and P80 groups because the milk P output of cows fed on the P67 diet had significantly declined. Valk and ebek (1999) and Valk et al. (1999) have described the negative effect of the P67 diet on DMI and milk yield and concluded that the diet produced P deficiency.

Although not significantly different for all periods during Lactation 2, it is clear that a reduction in P supply from 100 to 80% of the requirement resulted in a less positive P retention. It is not known which values of P retention should be considered optimal. For the whole period of lactation, the reduction in fecal P output was about 34% when P intake was reduced from 3.3 (P100) to 2.8 (P80) g P/kg DM at similar milk P output. Such a decrease would contribute significantly to the lowering of potential P losses from dairy manure to the environment.

Plasma and Saliva Results
Plasma and saliva P concentrations for period 1 during Lactation 1 were about 30% lower in P67 cows than in P100. During Lactation 2 plasma P contents in the P67 group were indicative of hypophosphatemia being 0.8 and 0.9 mmol/l. Rodehutscord et al. (1994) consider 1.5 to 1.9 mmol/l as normal values for plasma P, and after P depletion they found values of 0.3 mmol/l. The low plasma P values in cows fed on the P67 diet agree with the P retention data and the effects on feed intake and milk yield. In contrast to saliva P, plasma P during the first period of Lactation 2 (balance period 6) did not differ significantly between the P80 and P100 groups. Taken together, it would appear that plasma P is a more sensitive indicator of the P status than is saliva P concentration. The method of saliva sampling probably is crucial. This seemed to be in contrast with the observations of Wu et al. (2000) who found that plasma P concentrations are not always good indicators of P status. The difference with our trial may be related to the fact that in the study of Wu et al. (2000), cows were fed diets in the range of sufficient to excess, whereas in our trial diets contained sufficient to deficient amounts of P.

When comparing the P100 and P80 groups, it can be concluded that during Lactation 1 the differences in plasma P and saliva P were not marked. For the P80 group during Lactation 2, lower plasma P concentrations were observed, which was probably due to the higher yield of milk when compared to Lactation 1. The plasma P concentrations of 1.1 mmol/l during period 7 and 1.0 mmol/l during period 8 for the cows fed on the P80 diet may point at P depletion. Only during period 8 the low plasma P value was associated with low saliva P content. When, for longer periods, plasma P content is lower than 1.4 mmol/l, it is considered a sign of P deficiency (McDowell, 1992). Thus, based on the plasma and saliva contents, it could be suggested that cows fed on the P80 diet were deficient in P. On the other hand, P retention was not negative and feed intake and milk yield were not depressed (Valk and ebek, 1999). Based on similar plasma P, saliva P, milk yield, DMI, and P retention for the P80 and P100 treatments, it can be concluded that in our trial P intake with the P80 ration was marginally deficient or just sufficient to meet the P requirement.

In order to gain more insight into P metabolism of dairy cows, we plotted for individual lactating cows the relationships between selected variables. Figure 1 shows that an increase in milk P output is associated with an increase in the apparent digestibility of P. Even high-producing dairy cows fed on the P100 diet are able to reach apparent P digestibilities of up to 55%. Wu et al. (2000) stated that apparent P digestibility will range between 45 to 50% when fed closely to the requirement. The slopes are similar for the P80 and P100 groups, but the intercepts (34.4 versus 28.0) are significantly (P < 0.05) different. The latter is a consequence of the fact that, at constant milk P output, the apparent P digestibility will be increased when P intake is lowered. It is further shown that the data for the P67 group differed from those of the other treatments. This may be explained by a change in milk P as a result of feeding the P-deficient diet so that the apparent P digestibility was influenced by both P intake and milk P output. The level of apparent P digestibility in cows fed on the P67 diet was of the same order as that in the P80 group. This may imply that apparent P digestibility does not increase further when P depleted diets are fed. This is in agreement with the observations found by Spiekers et al. (1993). In general terms, the data in Figure 1 illustrate that, with increasing milk production, relatively more P from the ingested amount is transferred to milk and relatively less is excreted with feces, leading to an increased percentage of apparent P digestibility.

View larger version (72K): [in this window] [in a new window]   Figure 1. Relationship between milk P secretion (g/cow per day) and apparent P digestibility (%) for individual cow data. Cows in the three treatment groups are indicated by different symbols (P67, P80, and P100 are 67%, 80%, and 100%, respectively, of the Dutch P requirement system).

View larger version (73K): [in this window] [in a new window]   Figure 2. Relationship between milk P secretion (g/cow per day) and fecal P both expressed in g/cow per day for individual cow data (P67, P80, and P100 are 67%, 80%, and 100%, respectively, of the Dutch P requirement system).

View larger version (90K): [in this window] [in a new window]   Figure 3. Relationship between milk P secretion (g/cow per day) and blood plasma P concentration (mmol/l) for individual cow data (P67, P80, and P100 are 67%, 80%, and 100%, respectively, of the Dutch P requirement system).

View larger version (71K): [in this window] [in a new window]   Figure 4. Relationship between blood plasma and saliva P concentration both expressed in mmol/l of lactating and nonlactating cows.

	CONCLUSIONS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS ACKNOWLEDGEMENTS REFERENCES

	ACKNOWLEDGEMENTS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS ACKNOWLEDGEMENTS REFERENCES

 
This study was supported partially by the Commodity Board for Foodstuffs, The Hague, The Netherlands and by the Ministry of Agricultural, Nature Management and Fisheries.

Received for publication December 5, 2001. Accepted for publication April 2, 2002.

	REFERENCES

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS ACKNOWLEDGEMENTS REFERENCES

 


Agricultural and Food Research Council (AFRC). 1991. A reappraisal of the calcium and phoshorus requirements of sheep and cattle. Pages 573–612 in Nutrition Abstracts and Reviews (Series B).

Annenkov, B. N., 1982. Methods of determination of the requirements of farm animals for minerals. Pages 285–320 in Mineral Nutrition of Animals. V. I. Georgievski, B. N. Annenkov, and V. I. Samokhin, ed. Butterworths, London, United Kingdom.

Breves, G., and B. Schröder. 1991. Comparative aspects of gastrointestinal phosphorus metabolism. Nutr. Res. Rev. 4:125–140.

Call, J. W., J. E. Butcher, J. L. Shupe, R. C. Lamb, R. L. Boman, and A. E. Olson. 1987. Clinical effects of low dietary phosphorus concentrations in feed given to lactating dairy cows. Am. J. Vet. Res. 48:133–136.[Medline]

Gesellschaft für Ernährungsphysiologie (GfE). 1993. Mitteilungen des Ausschusses für Bedarfsnormen der Gesellschaft für Ernährungsphysiologie. Überarbeitete Empfehlungen zur versorgung von Milchkühen mit Calcium und Phosphor. Proc. Soc. Nutr. Physiol. 42:108–113.

Khorasani, G. R., R. A. Janzen, W. B. McGill, and J. J. Kennelly. 1997. Site and extent of mineral absorption in lactating cows fed whole-crop cereal grain silage or alfalfa silage. J. Anim. Sci. 75:239–248.[Abstract/Free Full Text]

Koddebusch, L., and E. Pfeffer, 1988. Untersuchungen zur verwertbarkeit von phosphor verschiedener herkunfte an laktierende ziegen. J. Anim. Physiol. Anim. Nutr. 60:269–275.

McDowell, L. R. 1992. Minerals in Animal and Human Nutrition. Academic Press, Inc., San Diego, CA.

National Research Council (NRC). 2001. Nutrient Requirement of Domestic Animals, Nutrient Requirements of Dairy Cattle. 7th ed. Natl. Acad. Sci., Washington, DC.

Netherlands Committee on Mineral Nutrition. 1973. Tracing Mineral Disorders in Dairy Cattle. Centre for Agricultural Publishing, Wageningen, The Netherlands.

Rodehutcord, M., A. Pauen, P. Windhausen, R. Brintrup, and E. Pfeffer. 1994. Effects of drastic changes in P intake and P concentrations in blood and rumen fluid of lactating ruminants. J. Vet. Med. Ser. A 41:611–619.

Scott, D., A. A. J. Rajaratne, and W. Buchan. 1995. Factors affecting fecal endogenous phosphorus loss in the sheep. J. Agric. Sci. 124:145–151.

Spiekers, H., R. Brintrup, M. Balmelli, and E. Pfeffer. 1993. Influence of dry matter intake on faecal phosphorus losses in dairy cows fed rations low in phosphorus. J. Anim. Physiol. Anim. Nutr. 69:37–43.

Ternouth, J. H. 1989. Endogenous losses of phosphorus by sheep. J. Agric. Sci. 113:291–297.

Valk, H., and A. C. Beynen. 2002. The assessment of phosphorus requirements of dairy cows. Livest. Prod. Sci. (In press).

Valk, H., J. A. Metcalf, and P. J. A. Withers. 2000. Prospects for minimizing P-excretion in ruminants by dietary manipulation. J. Environ. Qual. 29:28–36.[Abstract/Free Full Text]

Valk, H., and L. B. J. ebek. 1999. Influence of long-term feeding of limited amounts of phosphorus on dry matter intake, milk production, and body weight of dairy cows. J. Dairy Sci. 82:2157–2163.[Abstract]

Valk, H., L. J. ebek, A. T. van’t Klooster, and A. W. Jongbloed. 1999. Clinical effects of feeding low dietary phosphorus levels to high yielding dairy cows. Vet. Rec. 145:673–674.

Van Es, A. J. H. 1978. Feed evaluation for ruminants. 1. The system in use from 1977 onwards in the Netherlands. Livest. Prod. Sci. 5:331–345.

Wu, Z., L. D. Satter, and R. Sojo. 2000. Milk production, reproductive performance, and fecal excretion of phosphorus by dairy cows fed three amounts of phosphorus. J. Dairy Sci. 83:1028–1041.[Abstract]

This article has been cited by other articles:

				E. Charbonneau, P. Y. Chouinard, G. F. Tremblay, G. Allard, and D. Pellerin Timothy silage with low dietary cation-anion difference fed to nonlactating cows J Dairy Sci, May 1, 2009; 92(5): 2067 - 2077. [Abstract] [Full Text] [PDF]

				H. Arriaga, M. Pinto, S. Calsamiglia, and P. Merino Nutritional and management strategies on nitrogen and phosphorus use efficiency of lactating dairy cattle on commercial farms: An environmental perspective J Dairy Sci, January 1, 2009; 92(1): 204 - 215. [Abstract] [Full Text] [PDF]

				E. Kebreab, N. E. Odongo, B. W. McBride, M. D. Hanigan, and J. France Phosphorus Utilization and Environmental and Economic Implications of Reducing Phosphorus Pollution from Ontario Dairy Cows J Dairy Sci, January 1, 2008; 91(1): 241 - 246. [Abstract] [Full Text] [PDF]

				R. S. Dias, E. Kebreab, D. M. S. S. Vitti, A. P. Roque, I. C. S. Bueno, and J. France A revised model for studying phosphorus and calcium kinetics in growing sheep J Anim Sci, October 1, 2006; 84(10): 2787 - 2794. [Abstract] [Full Text] [PDF]

				R. O. Maguire, Z. Dou, J. T. Sims, J. Brake, and B. C. Joern Dietary Strategies for Reduced Phosphorus Excretion and Improved Water Quality J. Environ. Qual., November 7, 2005; 34(6): 2093 - 2103. [Abstract] [Full Text] [PDF]

				Z. Wu, S. K. Tallam, V. A. Ishler, and D. D. Archibald Utilization of Phosphorus in Lactating Cows Fed Varying Amounts of Phosphorus and Forage J Dairy Sci, October 1, 2003; 86(10): 3300 - 3308. [Abstract] [Full Text] [PDF]

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Valk, H. Articles by Beynen, A. C. Search for Related Content PubMed PubMed Citation Articles by Valk, H. Articles by Beynen, A. C.