PSXII-25 - Effects of level and source of dietary forage on performance of lactating Alpine goats

Thirty-two primiparous and 32 multiparous Alpine goats consumed diets varying in level and source of forage to determine influences on lactation performance. Diets were 40, 50, 60, and 70% forage (40F, 50F, 60F, and 70F, respectively), with forage in 60F and 70F being coarsely ground grass hay (primarily orchardgrass) and that in 40F and 50F cottonseed hulls, alfalfa pellets, and wheat hay. Initial body weight was 56.1±1.22 and 58.3±1.33 kg for primiparous and multiparous goats, respectively. Diets were 15.7-16.1% crude protein, 40.5, 45.9, 57.1, and 59.6% neutral detergent fiber (NDF), 6.1, 7.4, 4.6, and 5.0% acid detergent lignin, 10.0, 15.8, 50.1, and 55.5% particle retention on a 19-mm sieve, and 28.1, 32.4, 41.9, and 43.2% physically effective NDF for 40F, 50F, 60F, and 70F, respectively. The experiment started at 14 days-in-milk and lasted 16 wk. Average daily gain was similar (P > 0.05) among treatments (-23, -33, -28, and -28 g; SEM=1.11), but dry matter intake [(DMI) 2.71, 2.75, 1.96, and 1.95 kg/d, SEM=0.133] and milk yield (2.82, 2.71, 2.23, and 2.10 kg/d; SEM=0.157) were lower (P < 0.05) for the 2 diets highest in forage. Treatments affected (P < 0.05) milk fat (3.16, 3.37, 2.93, and 2.97%; SEM=0.120) and protein concentrations (2.62, 2.69, 2.58, and 2.52% for 40F, 50F, 60F, and 70F, respectively; SEM=0.042). Milk energy yield was greater (P < 0.05) for the 2 diets highest in concentrate (7.51, 7.45, 5.68, and 5.34 MJ/d; SEM=0.471), although relative to DMI yield was not affected (P > 0.05) by diet (2.94, 2.95, 2.76, and 2.74 MJ/kg for 40F, 50F, 60F, and 70F, respectively (SEM=0.164) and was greater (P < 0.05) for multiparous vs. primiparous goats (2.64 and 3.05 MJ/kg; SEM=0.116). In conclusion, lactational performance of Alpine goats in early to mid-lactation will be constrained with diets high in forage of moderate quality and large particle size.