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This experiment was performed to assess two different biodegradable coating formulations for the preservation of corn silage quality. Soy-and casein-based biodegradable coatings were evaluated for their ability to exclude oxygen and preserve corn silage. Experiments were conducted under natural conditions outdoors. The effect of the coating composition on silage quality was compared with the quality of silage covered with a plastic (0.15 mm) (positive control) and uncovered (negative control) after 4 and 8 week periods. The results showed that the two biodegradable coatings offered the same level of silage protection during the overall experiment (8 weeks). As compared with the negative control, the two formulations prevented deterioration associated with air infiltration (heating, mold growth and dry matter losses) and limited the decrease in nutritive value. Also, the pH of the coated silage was significantly lower (P ≤ 0.05) than the negative control after 4 weeks of storage. Silage coated with the biodegradable coatings was able to maintain the pH below 4.5 during the first 4 weeks of storage. The decline in lactic acid concentration seems to have been initiated by the lactate-utilizing yeasts, responsible for the increase in the silage pH. No visual growth of mold was observed in silage sealed with biodegradable coatings. This study showed that biodegradable coatings were able to protect the quality of silage during 4 weeks but the biodegradable coatings were not as good as plastic at preserving silage after 8 weeks of storage.

One hundred and eighty-six crossbred steers (194.4 ± 1.5 kg) were used to determine the effect of protein supplementation of medium-quality grass hay or silage on performance during wintering and compensatory growth during the grazing period. All steers received the hay or the silage ad libitum during the 182-d wintering period. They were also fed fixed quantities of one of three supplements: C, a control with no supplemental protein; CM, a canola meal; and FM, a fish meal containing supplements. Daily amounts of supplementation were fixed to supply to each steer the same amount of barley (85 g 100 kg−1 BW), of dry molasses (15 g 100 kg−1 BW) and of minerals, vitamins and Bovatec (10 g 100 kg−1 BW). The protein supplements CM and FM supplied the equivalent of 95 g of crude protein daily 100 kg−1 BW compared with 15 g 100 kg−1 BW for the control. Expressed as g kg−0.75, forage DM intake was 13.3% higher when fed as hay than as silage (P < 0.0001). Protein supplementation increased forage DM intake when fed as hay (P < 0.02) but not when fed as silage. Average daily gains (ADG) tended to be 5.8% higher for steers fed hay than for those fed silage (P = 0.06). Protein supplementation markedly improved ADG (P < 0.0001). When hay was fed, no differences were found in ADG between CM and FM supplementation; however, FM supplementation produced higher ADG than CM when silage was fed (P < 0.001). Feed efficiency was not affected by the type of forage fed, but it was higher for steers receiving protein supplementation (P < 0.001), the effect being more evident when the forage was fed as silage (P < 0.001) than when fed as hay (P = 0.07). Compensatory gains were obtained when the steers were taken out to pasture in early spring; steers fed silage, which obtained smaller ADG during wintering, showed higher ADG in pasture (P < 0.01). After 62 d grazing, the effect of protein supplementation during winter on body weight had almost disappeared. Key words: Protein supplementation, forages, cattle, growth

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