AbstractTwo feeding regimes were compared using 13 lactating cows (11 Holstein- Fresian and two Brown Swiss) confined in corrals. The rations consisted of a conventional concentrates mixture and sorghum silage in treatment A, and of 22.5 percent sugarcane bagasse mixed with 20.0 percent molasses and 57.5 percent other concentrates (complete ration) in treatment B. The experimental design was a double-reversal with 10-week periods, each divided into a 3-week adjustment and a 7-week comparison phase, preceded by a 25-day preliminary period. During the 7 weeks of the comparison phase of the first of the three experimental periods, five cows on treatment A averaged 37.0 pounds of concentrates and 30.5 pounds of silage consumption daily, while eight cows on treatment B consumed an average of 48.0 pounds of the complete ration. Average daily milk production with these respective rations during the comparison phase in question was 53.1 and 56.9 pounds. No significant differences between treatments were found. Over the three experimental periods of the double-reversal, daily intakes averaged 36.6 pounds of conventional concentrates mixture, 30.2 pounds of silage, and 45.1 pounds of complete ration. On treatments A and B, daily milk production averaged 48.6 and 47.4 pounds; milk fat percentage, 2.85 and 3.23; milk solids-notfat percentage, 9.08 and 9.03; milk total solids percentage, 11.92 and 12.26; milk protein percentage, 3.53 and 3.43; and daily liveweight gain, 1.15 and 1.01 pounds, respectively. The difference between treatment means was significant for milk fat (P < .01) and milk total solids (P < .05) percentages. Since the complete ration resulted in productive performance comparable to that obtained with ad libitum consumption of conventional concentrates, it is concluded that the former is capable of sustaining milk production at nearly maximum capacity. Milk production on treatment B was also equal to that obtained in a previous experiment with a complete ration containing 7.5 percent less bagasse and 5.0 percent less molasses, and correspondingly higher proportions of soybean meal and shelled corn.
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