L. ZHANG1,2, G.R. WIGGANS3, J. CLAY4, R. LACROIX5, J.Z. WANG1, T. GIPSON1 and S.S. ZENG1,*
1E (Kika) de la Garza American
Institute for Goat Research, Langston University, Langston, OK 73050, USA
2 Northeast Agricultural Research Center of China, Changchun, Jilin
130124, China
3 Animal Improvement Programs Laboratory, USDA-ARS,
Beltsville, MD 20705, USA
4 Dairy Records Management Systems,
North Carolina State University, Raleigh, NC 27603, USA
5
AgSource Cooperative Services, Verona, WI 53593, USA
The effects of breed, parity, stage of lactation (month), herd size, and regions/states on fat and protein content, somatic cell count (SCC) and production of milk from dairy goats enrolled in the Dairy Herd Improvement (DHI) program in the United States (U.S.) in 2007 were investigated to help goat producers improve their herd management and receive premiums for high quality goat milk. Statistical analysis of composite DHI data indicated that composition, SCC and production of goat milk were affected by many non-infectious factors. Marked variations (P < 0.05) in fat and protein content and milk production were found among goat breeds, particularly among those non-registered goats. In the first five parities, milk fat and protein content was relatively constant, however, a sharp decline (P < 0.05) was observed in parity 6. As parities increased, SCC in milk increased steadily (P < 0.05). Significant differences (P < 0.05) in all variables were discovered among regions. Large herds of goats tended to have lower milk fat and protein content but higher milk production and SCC than the small herds (P < 0.05). The above findings suggest that it be economically imperative to consider culling goats after their fifth lactation and that year-round breeding and lactation programs be practiced, if dairy goat producers in the U.S. are to meet the Grade "A" goat milk requirements. All factors that contributed to variations in fat, protein, SCC and production of goat milk should be taken into consideration when establishing price incentive systems for goat milk.
(Key words: Goat milk, DHI, somatic cell count, milk production)