C. Cadorniga et Ld. Satter, PROTEIN VERSUS ENERGY SUPPLEMENTATION OF HIGH ALFALFA SILAGE DIETS FOR EARLY LACTATION COWS, Journal of dairy science, 76(7), 1993, pp. 1972-1977
An experiment was conducted to test the hypothesis that cows in early
lactation are more likely to be limited by protein than by energy when
fed diets containing high proportions of alfalfa silage. After a 2-wk
covariate period, 26 multiparous cows were assigned to one of four tr
eatments from wk 3 to 14 of lactation. Treatments were a positive cont
rol diet with equal amounts of forage and grain (DM basis), an all for
age diet serving as negative control, and two test diets with 75% fora
ge and 25% of either high moisture ear corn or expeller soybean meal.
The latter two diets were equal in energy content but differed in the
amount of protein made available for absorption in the small intestine
. Alfalfa silage was the only forage in all diets. Milk yield with the
four diets averaged 36.3, 25.5, 32.1, and 35.5 kg/d, and milk protein
content was 2.93, 2.63, 2.77, and 2.75%. The negative control diet se
verely depressed milk protein content, which was not restored totally
by either test diet. We concluded that absorbable protein supply to th
e intestine is first-limiting when high alfalfa silage diets are fed t
o cows in early lactation.