Composition and Nutritive Value of Ground Sea Clam Shells as Calcium Supplements for Lactating Holstein Cows

¹ Department of Animal Sciences, Rutgers-The State University, New Brunswick, NJ 08903
² New Jersey Marine Advisory Service, Cape May Court House, NJ 08210

Ocean quahog and surf clam shells were evaluated as Ca supplements with aragonite as a reference standard. Shells obtained directly after processing were dried, and particle size was reduced through a jaw crusher and disc grinder. Calcium, total acid-consuming capacity, and rate of reactivity (pH 6 and 3) for aragonite, Ocean quahog, and surf shell were 39.2, 38.5, and 36.4%; 19.8, 18.8, and 18.4 meq/g; >9, >9, and 3.5 h at pH 6; and 43, 38, and 20 min at pH 3; respectively. Particle size was determined by dry sieving with 75, 80, and 55% of aragonite, Ocean quahog, and surf shell >150 µ. Shell characteristics contributed to variation in particle size. Each Ca source provided approximately 65% of Ca intake for three midlactation Holstein cows fed a corn silage and concentrate (l:l, DM basis) diet in a 3 x 3 Latin square design for 4 wk. Cows fed aragonite, Ocean quahog, and surf shell averaged DMI, 20.3, 21.6, and 22.6 kg/d; milk yield, 26.9, 28.8, and 28.3 kg/d; milk fat, 4.23, 4.17, 4.03%; milk protein, 3.48, 3.32, and 3.40%; apparent digestibility of DM, 72.5, 71.7, and 72.0%; apparent digestibility of Ca, 20.6, 31.5, and 33.9%; and fecal pH, 6.31, 6.31, 6.45; respectively. Data support that sea clam shells reduced to the particle size utilized in this study can serve as effective Ca supplements for lactating dairy cows.

Key Words: calcium supplements • sea clam shells • lactation

Submitted on June 22, 1992
Accepted on October 28, 1992