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Fifteen lactating Holstein cows in a 3×3 Latin square experiment determined effects of ground newspaper in the diet. Test components of the rations were: A) 20% cottonseed hulls; B) 10% paper and 10% cottonseed hulls; C) 20% paper. All animals received 2.3kg of long alfalfa hay daily. Proximate analysis and gross energy determinations indicated that the paper rations contained more crude fiber, ether extract, and gross energy and less crude protein and ash. Ink in the paper apparently caused higher gross energy values and probably increased ether extract. Estimates of dry matter digestibility by an in vitro technique were not significantly different being 77.4, 77.4, and 77.5 for the control, 10% paper, and 20% paper rations. Average daily ration intakes were significantly different among rations with intakes of 21.5, 17.0, and 12.5kg per day for the control, 10% paper, and 20% paper. Paper at 20% of the ration significantly lowered actual milk yields but did not significantly lower fat-corrected milk yield during the six weeks. Average daily fat-corrected milk yields for control, 10% paper, and 20% paper treatments were 15.9, 16.9, and 16.3kg. Milk fat percentages were 2.6, 3.1, and 3.4 with significant differences between treatments. Milk protein and solids-not-fat were not significantly different; however, there was an inverse linear response between treatment and milk protein percentage. There were small differences in ruminal volatile fatty acids with a significantly lower pH for the 20% paper compared with the control. Paper at 10% in the ration would maintain milk fat percentage without reducing actual milk production during six weeks.

In vitro dry matter disappearances were determined for 11 paper sources and three complete rations containing 0, 10, and 20% newsprint. Inoculum was from an alfalfa hay-fed steer. Alfalfa hay, brome hay, and Solka Floc were reference substrates. Brown wrapping paper and brown cardboard had the highest dry matter disappearances of 90.8 and 77.8%; whereas four glossy or slick magazine papers had significantly lower values of 46.1, 45.1, 41.3, and 41.0%. Newsprint with black ink, without ink, and with colored inks had dry matter disappearances of 33.2, 32.6, and 26.5%, which were significantly lower than those of the glossy magazine papers. Lowest dry matter disappearances of 24.0 and 20.1% were from two magazine papers. The complete rations had 77.9, 80.1, and 81.8% dry matter disappearances for the 0, 10 and 20% paper rations. These data indicate substantial differences in digestibilities of various paper sources.