AbstractA study was undertaken to compare the effect of four levels of crudeprotein in concentrate mixes on the milk production of cows fed cut forage as green-chop in Puerto Bico. The double-reversal experimental design was used in the study. The four levels of crude-protein used were: 12-, 16-, 20-, and 24-percent. Each of 54 milking cows were used for three consecutive lactation periods. Each animal received a uniform ratio of 1 pound of concentrate mix to every 2.5 pounds of milk, and the proportion of concentrate fed to milk produced was adjusted every 10 days. Milk production expressed as 4-percent fat-corrected milk was the only criterion for evaluation. Napier (Merker) grass, the roughage mostly consumed, varied in nutritive value from good to fair to poor, due to seasonal and annual differences. All animals in this study consumed Merker grass ad libitum. Milk production, concentrate, and roughage consumption data were recorded. Animal weights were recorded at the beginning of each period and then monthly thereafter. No statistical differences were observed in milk production between the four concentrate levels. It can be concluded that all four treatments were equally good. If concentrate feeds with lower crude-protein content can be purchased at less cost, dairymen will reduce their production costs by feeding them.
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