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Brown Alfalfa Hay—Its Chemical Composition and Nutritive Value in Dairy Rations¹

Kansas Agricultural Experiment Station, Manhattan, Kansas

ABSTRACT

Normal, long alfalfa hay was compared in chemical composition and in apparent digestibility with brown, excessively heated hay from the same source and with black excessively heated, chopped hay from a different source. The alfalfa hay was supplemented only with drinking water. Each type of hay was fed to two dairy cows in amounts equal to the animals' appetites. The data on digestibility were supplemented by comparisons with four cows in a double-reversal feeding test of the same type of brown hay with normal alfalfa hay from a different source. During most of this test, both hays were chopped before feeding; the hay supplied approximately 50 per cent of the total dry matter intake and was fed in conjunction with sorgo silage and a grain mixture.

The following interpretations of results seem justified:

1. Chemical analyses showed that brown hay contained more ash and more crude fiber than normal alfalfa hay from the same stack, and that excessive heating during storage resulted in decreased percentages of nitrogen-free extract and of ether extract. Similar, but larger, differences in percentage composition were noted between the normal hay and a black grade of alfalfa hay obtained from a different source.
   
2. Excessive heating during storage consistently lowered the apparent digestibility of all nutrients measured, except that of ether extract which was consistently greater in the heated hays. Protein was affected most, with average digestibility-coefficients of 67 for normal hay, 16 for brown hay, and 3 for black hay. Average coefficients for the other nutrients in the normal, brown, and black hays, respectively, were: Dry matter—60, 41, and 27; ether extract—25, 33, and 42; crude fiber—41, 36, and 14; and nitrogen-free extract—72, 59, and 53. The digestible protein and total digestible nutrients in these hays were calculated to be as follows: 14 and 56 for the normal hay, 3 and 38 for the brown hay, and 0.6 and 23 for the black hay.
   
3. When alfalfa hay was the sole source of dry matter in the ration, the daily intake of dry matter per 1,000 pounds of body weight was—20 for normal hay, 15 for brown hay, and 10 for the black hay. In terms of digestible nutrients, these daily intakes were equivalent to 2.9 pounds of digestible protein and 11.3 pounds of total digestible nutrients for the cows fed normal hay, 0.5 and 5.6 for the brown-hay cows, and 0.06 and 2.3 for the black-hay cows.
   
4. When dairy cows were limited to rations of alfalfa hay and tap water fed to the limits of the animals' appetites, nutrient intakes were adequate for the cows fed normal hay, but were decidedly inadequate for the cows fed the brown and black hays. Under these conditions, the total daily water intake minus the equivalent of that in the milk produced was: 4.9 pounds of water per pound of dry matter consumed in normal hay, 3.9 for brown hay, and 4.7 for the black hay. The cows fed heated hays lost considerable in body weight, developed a gaunt appearance, and—in the case of the black hay—also became uneasy and appeared to crave something in their rations. Feces voided by cows fed excessively heated hay took on a dark to black appearance, contained less moisture, and those resulting from the black hay were voided in the form of hard, dry, flattened pellets.
   
5. When fed in conjunction with sorgo silage and a grain mix and compared with normal hay from a different source, the brown alfalfa hay was consumed in greater amounts; but average daily milk production appeared to be somewhat in favor of the normal hay. However, these comparisons were limited to only four cows in a double-reversal feeding test, and the chemical analyses indicated that the original quality of the brown hay was superior to that of the normal hay both in protein and in fiber content.
   
6. These results show that excessively heated alfalfa hay may be decidedly inferior in nutritive value to green alfalfa hay, and that this impairment in feeding value is more or less proportional to the intensity of brown to black color developed during excessive heating of the hay. Palatability observations—as measured by feed intakes and refusals—showed that brown alfalfa hay was less palatable than normal green hay from the same stack, but that this same type of brown hay was more palatable than normal green hay obtained from a different source and apparently containing less protein and more fiber than originally present in the alfalfa from which the brown lay was produced.
   

¹ Contribution No. 156, Department of Dairy Husbandry.