Evaluation of U.S. sheep breeds for milk production and milk composition

Abstract

Seven standard, Dorset (D), Finnsheep (F), Lincoln (L), Rambouillet (R), Romanov (Ro), Suffolk (S), Targhee (T), and three synthetic breeds of sheep, Synthetic I (F×L), Synthetic II (D×R), and Synthetic III (F×L) × (D×R), were evaluated for milk yield (MILK, 1), average daily milk yield (ADY, ml) and contents of fat, protein, lactose and total solids in a five year lactation trial. Highly significant differences were observed ( P<0.01) among breeds for all traits (30 d postpartum after weaning) except percentages of fat and lactose. Average total milk yield was 65.51 in 122 d, and average daily milk was 533 ml. Suffolk were superior for MILK (83 liters) and ADY (680 ml), followed by Synthetic II. Lowest MILK and ADY values were recorded for Romanov (35 liters and 299 ml, respectively). Synthetic I ranked second lowest. Overall average fat content of milk was 6.0%, Suffolk produced the highest average (6.6%), followed by Dorset (6.5%). Lowest fat percentage was in Synthetic I (5.6%) milk. Overall average protein content was 5.8%; milk of Dorset, Romanov and Synthetic II was similar (6.1%) and ranked highest. Overall average lactose and total solids contents were 4.8% and 17.4%, respectively. Rambouillet ranked first for lactose (4.9%). Finnsheep had lowest percentages of milk protein and lactose (5.4% and 4.7%, respectively), and ranked second lowest for total solids (16.8%). Dorset excelled for total solids (18.2%). Targhee, Lincoln and Synthetic III were intermediate in all traits. It was concluded that variation exists among and within U.S. sheep breeds for milk production traits. Overall performance for milk production was lower than “dairy” sheep breeds of Europe and Middle East. Introduction of superior non-U.S. germ plasm could result in faster genetic improvement than selection within existing U.S. breeds over many generations.