Milk Yield and Composition of Lactating Cows Fed Steam-Flaked Sorghum and Graded Concentrations of Ruminally Degradable Protein

Abstract

To determine the effect of various amounts of ruminally undegradable protein in the diets of lactating cows fed steam-flaked sorghum, 24 Holstein cows (90 +/- 50 d in milk) were assigned to three treatments: 0.8% urea, 6% soybean meal, or 5% fish meal. Respective percentages of ruminally undegradable protein in the diets (as a percentage of crude protein) were 30, 35, and 39%. All diets contained 37% alfalfa hay; 3 to 5% cottonseed hulls; 10 to 13% whole cottonseed; 39% steam-flaked sorghum (360 g/L); 5% of a molasses, mineral, and vitamin supplement; and the different protein supplements. Intake of dry matter was higher for cows fed urea than for cows fed soybean meal or fish meal diets. In cows that yielded more than 40 kg/d of milk (4 cows per treatment), the soybean meal and fish meal diets resulted in higher yields of milk and 3.5% fat-corrected milk and a greater efficiency of conversion of feed to milk than did the urea diet. Cows that yielded less than 40 kg/d of milk (4 cows per treatment) at the beginning of treatment tended to yield more milk when fed urea than when fed the protein supplements. Nutrient digestibilities were not greatly affected by source of N, suggesting a beneficial effect of urea supplementation on nutrient digestibilities because replacement of protein supplements with cottonseed products caused the neutral detergent fiber content of the urea diet to be about 7% higher than that of the other diets. These data show that response to ruminally undegradable protein in diets of lactating cows fed steam-flaked sorghum was related to milk yield.

Efeito de fontes e formas de processamento do amido sobre o desempenho e o metabolismo do nitrogênio em vacas Holandesas em lactação

“…De acordo com Santos et al (1998), os efeitos positivos do aumento da degradabilidade do amido sobre o teor de proteína do leite estão relacionados, possivelmente, à síntese microbiana mais intensa, que acarreta aumento no fluxo de proteína metabolizável para o intestino e melhora o perfil de aminoácidos essenciais. Entretanto, neste trabalho, o teor de proteína no leite e a síntese de proteína microbiana diminuíram (P<0,05) com a utilização da raspa de mandioca, apesar da alta digestibilidade ruminal do amido.…”

Metabolizable protein supply according to the nrc (2001) for dairy cows grazing elephant grass

“…Milk fat (3.37; 3.27, 3.30%), protein (3.07; 3.12; 3.08%) lactose (4.39; 4.40; 4.41%) and total solids (11.73; 11.66; 11.70%) contents and yields were not affected (P > 0.05) by treatments (Table 5). Milk protein yield in high producing dairy cows (> 30 kg day -1 ) is affected by the MP supply and by the MP amino acid profile (Schwab et al, 1976;Santos et al, 1998 Increasing concentrate CP by feeding extra soybean meal beyond the NRC (2001) recommendation increased milk urea nitrogen (MUN) linearly (P < 0.05) (11.17; 13.9; 15.63 mg dL -1 ). This increase in MUN without an increase in milk yield and composition, indicates a poor utilization of this extra protein in the concentrate.…”

Substituição do milho e do feno de capim-tifton por palma forrageira. Produção de proteína microbiana e excreção de uréia e de derivados de purina em vacas lactantes

“…Segundo Santos et al (1998), o nível ótimo de nitrogênio amoniacal ruminal varia de acordo com a disponibilidade de carboidratos fermentáveis no rúmen. Zeoula et al (2002) afirmaram que a sincronização entre as fontes de carboidratos e nitrogênio pode acarretar maximização da eficiência microbiana e diminuição da perda de nitrogênio na forma de N-NH 3 .…”