Effects of Dietary Levels of Forage and Ruminally Undegraded Protein on Early Lactation Milk Yield by Alpine Does and Doelings

Abstract

Goetsch, A.L., Puchala, R., Lachica, M., Sahlu, T. and Dawson, L.J. 2000. Effects of dietary levels of forage and ruminally undegraded protein on early lactation milk yield by Alpine does and doelings. J. Appl. Anim. Res., 18: 49–60.

Thirty-one Alpine does and 31 doelings (52±1.62 and 34±0.86 kg initial body weight, respectively) were used to determine effects of dietary levels of forage and ruminally undegraded protein (RUP) and change in forage level on early lactation performance. Goats began a 2-week covariate period at 3–9 days after parturition, then were assigned to treatments: 80 = 80% forage diet; 80R = 80 with added RUP; 40 = 40% forage diet; 40R = 40 with RUP added; 40–80 = 80 in weeks 1–3, transition to 40 in weeks 4–5 and 40 in weeks 6–16; and 80R-40R-80R in weeks 1–3, transition to 40R in weeks 4–5 and 40R in weeks 6–16. Diets were 18–19% crude protein (dry matter basis);for 80R and 40R, equal crude protein was supplied by blood, fish and feather meals, substituting for approximately two-thirds of soybean meal protein. Milk yield was greater (P<0.05) for 40 and 40R than for 80 and 80R, and was influenced (P<0.05) by RUP in weeks 1–3 and 4–5 (weeks 1–3: 2.51, 2.74, 2.72, 3.33, 2.44 and 2.54 kg/day; weeks 4–5: 2.52, 2.73, 3.13, 3.59, 2.56 and 2.62 kg/day; weeks 6–16: 2.18, 2.33, 2.85, 3.11, 2.54 and 3.01 kg/day for 80, 80R, 40, 40R, 80–40 and 80R-40R, respectively). Milk protein concentration was greater (P<0.05) for 40 and 40R than for 80 and 80R (e.g., week 5: 2.81, 2.72, 2.91, 2.86, 2.76 and 2.94% for 80, 80R, 40, 40R, 80–40 and 80R-40R, respectively). In conclusion, milk yield- in a 16-week early lactation period was greater with 40 vs 80% forage, although RUP impacted milk yield only early in the experiment. Changing dietary forage level in early lactation of dairy goats did not influence subsequent production.

Key words:

• Goat
• lactation
• forage
• protein