Effect of preservatives and maturity on the nutritional value of alfalfa hay for lactating dairy cows.

Abstract

Urea was applied uniformly inside alfalfa hay bales at baling or on top of bales subjected to rain and weather damage. Hay temperature, color, mold retardation and chemical composition were measured. Also, 24 lactating cows were used to test acceptability of the urea-treated hays. Cows were blocked for 14 d pre-treatment milk production and randomly assigned to one of six treated hays for 3 wk (4 cows/group). Cows were then reassigned at random to another hay for an additional 3 wk. Addition of 1% or more urea to high moisture alfalfa hay resulted in higher nutritional quality through reducing bale temperatures, non-enzymatic browning, and moldiness, compared to high moisture untreated hay. Urea treatment of high moisture hay decreased ADF and NDF content, while increasing digestibility of their fiber components. Urea treated hays were readily eaten by cows with no significant differences (P>.05) between treatments in DM intake, milk production, milk composition, or DM, ADF, and NDF digestion coefficients. Five types of alfalfa hay varying in % ADF were fed to 40 lactating cows. Cows were divided into 10 groups of 4 each based on 14-d pre-treatment milk. Each hay was mixed in TMR diets with 50 or 65% concentrate. In vivo and in situ trials were conducted to determine DM, ADF and NDF digestion. Results indicated that DMI, 3.5% FCM, cows body weight, body score, rectal temperature, and milk composition except milk fat were not affected by type of hay or level of concentrate. Milk fat was affected by level of concentrate (P<.16) while milk production was affected by type of hay (P<.01). Dry matter digestion coefficients for the complete rations showed no change with increased ADF in hay. Large decreases were noted in in situ DM, ADF, and NDF digestion as hay ADF increased. In another experiment, 32 mid to late lactation cows were used in a 41 d production trial. Cows were fed 2 levels of concentrate (25 vs. 50%) with alfalfa hay. Data indicated that DMI, milk yield, 3.5% FCM, milk composition, and other parameters did not differ between treatments. This might be due to the lack of response to higher concentrate level.