Mineral and water nutrition.
In providing minerals to dairy cattle it is important to distinguish between dietary requirements and feeding recommendations. The requirement is the absolute amount of an element needed to meet the animal's metabolic needs for maintenance, growth, pregnancy, and lactation divided by the coefficient of absorption; this is estimated by the factorial method. Actual estimates of requirements for lactating dairy cattle have been determined for Ca and P. The major difficulties in relying on the requirement estimate are that dry matter intake varies and the true absorption coefficient of the mixture of feeds in the ration generally is unknown. Therefore, feeding recommendations, based on feeding graded concentrations of an element, often offer more applicable information. With the exception of Ca and P, the current feeding recommendations for the other macrominerals, Mg, Na, K, Cl and S, have resulted from feeding trials. With certain environmental and physiologic situations the feeding recommendations may vary. For example, during heat stress the dietary K recommendation for the lactating cow should be higher than in cool weather because of increased sweating and decreased feed intake. Another example may be that the source of supplemental Mg may affect what dietary inclusion rate will yield optimal performance and should be recommended. An important consideration in dairy ration formulation in the future will address the interrelationships of the various macrominerals. There is accumulating evidence that shows that different concentrations of Na, Cl, and K may interrelate and affect lactational performance. Many times the naturally occurring concentrations of one or more of these elements may have to be associated with varying concentrations of the others in order to optimize animal performance and health. Much experimentation likely will examine these interrelationships in the future. Supplementation of trace elements in diets of dairy cattle is common practice. This is because the quantities found in common feedstuffs are relatively low relative to the animal's needs and vary considerably among and within feeds. Supplementation provides a safety margin against potential deficiency. The reader is cautioned to consult other publications regarding potential interactions among the trace elements and their interactions with other nutrients. Potential oversupplementation is a real concern. Maximum safe tolerance concentrations for most trace elements are available. Water is the most important indispensable nutrient. Water requirements are affected by physiologic state and rate of milk yield, body weight, rate of dry matter intake, Na intake, and average minimum environmental temperature. Practically, offering a fresh, abundant supply of easily accessible drinking water at all times is essential.(ABSTRACT TRUNCATED AT 400 WORDS)
Beede
D K
DK
Dairy Science Department, University of Florida, Gainesville.
D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002136:Calcium, Dietary / Q000008:administration & dosage; D002417:Cattle / Q000502:physiology*; D002713:Chlorine / Q000008:administration & dosage; D004326:Drinking; D008274:Magnesium / Q000008:administration & dosage; D008903:Minerals / Q000008:administration & dosage*; D016226:Phosphorus, Dietary / Q000008:administration & dosage; D011188:Potassium / Q000008:administration & dosage; D012982:Sodium, Dietary / Q000008:administration & dosage; D013455:Sulfur / Q000008:administration & dosage; D014131:Trace Elements / Q000008:administration & dosage; D014867:Water / Q000008:administration & dosage*
D002136:Calcium, Dietary; D008903:Minerals; D016226:Phosphorus, Dietary; D012982:Sodium, Dietary; D014131:Trace Elements; D014867:Water; D002713:Chlorine; D013455:Sulfur; D008274:Magnesium; D011188:Potassium