The effect of diet on somatic cell count, mastitis and gastro-intestinal parasite infestation in dairy goats.

B. R. Min¹, G. Tomita¹, S. P. Hart¹, W. Pomroy², and T. Sahlu¹

¹E (Kika) de la Garza Institute for Goat Research, Langston University, Langston, OK
²Veterinary and Biomedical Science, Massey University, Palmerston North, New Zealand

A study was conducted to investigate effects of concentrate level on milk somatic cell counts (SCC), incidence of intramammary infection (IMI) in udder halves, and gastro-intestinal parasite infestation in pastured dairy goats during mid- and late lactation (June-Sept., 2001; 90-200 days in milk). Twenty-four Alpine goats (55 ± 11 kg BW) were randomly allocated to four treatments and were supplemented with 0.66 (treatments A and B), 0.33 (treatment C), or 0 kg concentrate (treatment D) per kg of milk over 1.5 kg/d. Mixed vegetative forages (wheat/berseem clover, sudan grass, and cowpeas) were rotationally grazed except for A (confined and fed alfalfa hay). Milk samples for bacteriology and SCC were collected monthly from both halves. Fecal and blood samples were collected monthly for strongyloid fecal egg count (FEC) and packed cell volume (PCV) analysis, respectively. Prior to analysis, FEC and SCC were log transformed and PCV were transformed to their arcsin value. Coagulase negative Staphylococcus (52.4%), S. aureus (14.3%), and Pseudomonas aeruginosa (14.3%) were the most prevalent isolates. Infected glands had higher SCC (3.1 x 10⁶ vs 1.0 x 10⁶; P < 0.001) than uninfected glands. Mastitis was positively correlated with SCC in A (R² = 0.41; P < 0.01) and B (R² = 0.35; P < 0.05), but was not correlated with C (R² = 0.18) or D (R² = 0.29; P = 0.07). Infection increased SCC, but the degree of increase in SCC varied with pathogen. The FEC was lower in A (102 eggs/g; P < 0.01) than in B (972 eggs/g), C (972 eggs/g), and D (1,171 eggs/g), but there were no differences among levels of supplementation in pastured goats. Treatment D tended (P = 0.09) to have lowest PCV. High levels of concentrate supplementation did not reduce parasitism in pastured does. In addition, effective mastitis screening requires bacteriological culture since SCC were not highly correlated with IMI.