659
Evaluation of diets formulated with soybean-based products, blood meal, or rumen-protected lysine to meet MP lysine demands of lactating dairy cows
Objectives were to determine if production of early to mid-lactation dairy cows was maintained when fed diets formulated to be similar in grams of metabolizable protein (MP) lysine and methionine but lower in CP. Diets were formulated using: 1) soy-based protein (positive control; PC, 17.7% CP, 204 g/d MP-lys), 2) blood meal and soy-based protein (BM; 16.4% CP, 203 g/d MP-lys), or 3) rumen-protected lysine and soy-based protein (RPL; 16.2% CP, 205 g/d MP-lys). Diets formulated to desired MP lysine (204 g/d) were compared with a negative control diet lower in MP lysine (LL; 16.2% CP, 193 g/d MP-lys) created by removing dietary RPL. Diets were formulated using AMTS (Version 3.4.7.1). Sixteen Holstein cows blocked by parity (12 multiparous) and production were assigned one of four treatments arranged in a 4 × 4 Latin square design with 28-day periods. The model included: treatment, square, treatment × square and period. Treatments were prepared as four separate concentrate mixes which were combined with common amounts of corn silage (36% of diet DM) and alfalfa hay (19%) among diets. Milk production was similar (P > 0.10) comparing BM and RPL with PC or LL, but tended (P = 0.06) to be greater for BM over RPL. Cows fed BM and RPL had lower (P= 0.04) DMI than LL; however, ECM was sustained which led to an increase in feed efficiency comparing BM and RPL with LL. Performance of lower CP diets, BM and RPL, were similar to PC, but performance from LL suggests that MP supply was sufficient across treatments.
|
|
|
|
|
|
|||
Treatment |
||||||||
Item |
PC |
BM |
RPL |
LL |
SEM |
Contrast1 |
||
DMI, kg/d |
26.16 |
25.64 |
25.46 |
26.66 |
0.61 |
B |
||
Milk, kg/d |
39.47 |
40.44 |
38.81 |
39.50 |
1.08 |
d |
||
ECM |
39.35 |
40.43 |
39.37 |
39.88 |
1.36 |
--- |
||
ECMFE |
1.53 |
1.59 |
1.59 |
1.52 |
0.05 |
a, B |
||
Fat, % |
3.47 |
3.54 |
3.59 |
3.55 |
0.12 |
--- |
||
Fat, kg/d |
1.35 |
1.42 |
1.39 |
1.40 |
0.06 |
--- |
||
Protein, % |
3.17 |
3.06 |
3.10 |
3.13 |
0.08 |
A, b |
||
Protein, kg/d |
1.25 |
1.23 |
1.20 |
1.23 |
0.05 |
--- |
||
MUN, mg/dL |
16.59 |
13.92 |
14.03 |
13.46 |
0.33 |
A, b |
||
1Contrasts: A = PC vs. BM + RPL; B = BM + RPL vs. LL; D = BM vs. RPL. Uppercase = P < 0.05, lowercase = 0.05 < P < 0.10. |
||||||||
Keywords: amino acid, lysine, metabolizable protein