Effects of level and type of fiber sources on feed intake, milk production and composition, nutrient utilization, ruminal fermentation, blood constituents, and eating behavior in Alpine goats

Abstract

Thirty Alpine does and 32 doelings, averaging 45.2 ± 1.45 days-in-milk, were used to assess the effects of level and type of neutral detergent fiber (NDF) sources on dry matter intake, average daily gain, digestion, and milk production. Diets contained 40, 50, 70, and 70% fiber sources, denoted as 40F, 50F, 50W20S, and 40W30S, respectively, with 50W20S and 40W30S containing 50:20 and 40:30% wheat hay:soybean hulls, respectively. The diet NDF concentration was 35.7, 39.3, 51.6, and 51.7% and crude protein was 15.8, 15.3, 11.4, and 11.8% for 40F, 50F, 50W20S, and 40W30S, respectively. Average daily gain was lower (P < 0.05) in two high fiber sources diets compared with 40F, though differences were modest. Dry matter (DM) intake decreased (P < 0.05) in 50W20S and 40W30S relative to 40F and 50F. Heat energy was not affected by diet (P > 0.05). Body condition score in doelings was lowest for 50W20S (P < 0.05), while does showed no differences among diets (P > 0.05). Fiber intake and digestibility were greater (P < 0.05), whereas crude protein intake and digestibility were lower (P < 0.05) in 50W20S and 40W30S compared with 40F and 50F. Milk fat concentration was greatest in 40W30S (P < 0.05), and total solids were greater in 40W30S than 40F and 50W20S (P < 0.05), while 50F was greater than 50W20S but not different from 40F (P > 0.05). Milk urea nitrogen was greatest in 50F, intermediate in 40F, and lowest in 50W20S and 40W30S (P < 0.05). Milk energy yield relative to DM intake was not affected (P > 0.05). Ruminal ammonia-N was lowest in 40W30S (P < 0.05). Although acetate:propionate ratio was unchanged (P > 0.05), acetate increased and ranked 40F < 50F < 50W20S = 40W30S (P < 0.05). Propionate was greatest in 40F, lower in 50F and 40W30S, and intermediate in 50W20S (P < 0.05), while butyrate was greater in 40F and 50F than other diets (P < 0.05). Blood metabolites showed diet effects: total protein was greatest in 50W20S (P < 0.05), albumin was greater in 50F than in 50W20S and 40W30S (P < 0.05), and blood urea nitrogen followed a similar pattern. Cholesterol was greater in 40F and 50F than in 50W20S (P < 0.05), and triglycerides were greater in 50F than in soybean hull diets (P < 0.05). Thyroxine was lowest in 40F (P < 0.05) compared with other diets. Overall, despite variations in intake, digestion, rumen fermentation, and blood metabolites, Alpine goats appear to be well adapted to these diets differing in fiber level and source, maintaining acceptable productivity during mid- to late lactation.