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Title: Mass and Composition of Mammary Fat Pad, But Not Parenchyma Are Affected by Diet in Pre-weaned Holstein Heifers

item Daniels, K
item Hill, S
item Knowlton, K
item James, R
item Mcgilliard, M
item Capuco, Anthony
item Akers, R

Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 3/10/2008
Publication Date: 7/1/2008
Citation: Daniels, K.M., Hill, S.R., Knowlton, K.F., James, R.E., Mcgilliard, M.L., Capuco, A.V., Akers, R.M. 2008. Mass and Composition of Mammary Fat Pad, But Not Parenchyma Are Affected by Diet in Pre-weaned Holstein Heifers. [abstract]. Journal of Dairy Science.

Interpretive Summary:

Technical Abstract: Overfeeding prepubertal heifers may impair mammary parenchymal growth and reduce milk production, but dietary impacts in pre-weaned calves are unknown. Our objectives were to determine effects of milk replacer composition on mass and composition of mammary parenchyma and fat pad (MFP). Twenty-four newborn heifers were fed one of four milk replacer (MR) diets (n=6/diet): CON (20% CP, 21% fat MR fed at 441 g DM /d), HPLF (28% CP, 20% fat MR fed at 951 g DM/d), HPHF (27% CP, 28% fat MR fed at 951 g DM/d), and HPHF+ (27% CP, 28% fat MR fed at 1431 g DM/d). Calves were fed twice daily with water and starter (20% CP, 1.43% fat) offered ad libitum. Tissue samples were taken on d 63 for analysis of protein, lipid, and DNA. Total mammary gland mass was lowest in CON (CON vs. others; 150 vs. 284 ± 30 g). Increased feeding (HPHF vs. HPHF+; 288 vs. 379 ± 30 g) as well as added fat (HPLF vs. HPHF; 185 vs. 288 ± 30 g) increased gland mass. Neither parenchymal mass (CON, HPLF, HPHF, and HPHF+: 9.2, 11.7, 15.5, 15.1 ± 3.3 g) nor composition were affected by diet. Parenchyma averaged 4.2 ± 0.30% protein, 13.8 ± 2.2% lipid, and 0.21 ± 0.02% DNA. In contrast to parenchyma, MFP was markedly affected by diet. MFP mass (140 vs. 270 ± 30 g; CON vs. other treatments) and total MFP lipid (37 vs. 144 ± 25 g) were lowest in CON but total DNA content did not differ (60 vs. 54 ± 12 mg). The added fat increased MFP mass (173 vs. 273 ± 30 g), tended to increase total MFP lipid (64 vs. 132 ± 25 g), but decreased total MFP DNA (84 vs. 42 ± 12 mg). Increased intake of HPHF raised MFP mass (273 vs. 364 ± 30 g) and MFP lipid (132 vs. 234 ± 22 g), but did not affect MFP total DNA (42 vs. 37 ± 11 mg). Total protein in MFP was unaffected by diet, but protein concentration of MFP was highest in CON compared with the other 3 diets (20 vs. 11 ± 3 mg/g MFP). Added fat decreased MFP protein concentration (20 vs. 9 ± 3 mg/g), and increased intake of HPHF had no effect on MFP protein concentration (9 vs. 6 ± 3 mg/g). In conclusion, diet had no effect on mammary parenchyma, but MFP mass and composition were affected. Implications of these results to future milk production remain to be determined.