Fried and cooked potato co-products improve diet physical properties and milk production in Holstein lactating dairy cows

The aim of the present study was to evaluate the effects of replacing barley grain with heated potato slice wastes (HPSW) or French fries’ wastes (FFW) on dry matter intake and production performance of lactating Holstein dairy cows. Twenty-four Holstein dairy cows (body weight: 639 ± 20.3 kg, parity: 3.0 ± 0.21, days in milk: 123 ± 11.7, raw milk yield: 41.5 ± 2.86 kg/d) were randomly assigned to 3 treatments: 1) Control: diet containing 204 g/kg of dry matter (DM) barley grain as the main source of non-forage carbohydrates, 2) HPSW: diet containing 104 g/kg DM barley grain and 100 g/kg DM HPSW, 3) FFW: diet containing 104 g/kg DM barley grain and 100 g/kg DM FFW. The results showed that the frying process of potato increased the fatty acid content from 4.9 to 198 g/kg DM. The replacement of barley grain with HPSW or FFW decreased dry matter intake significantly (P=0.02) and values were 24.6, 23.3, and 23.8 kg/d for control, HPSW and FFW respectively. Also, results revealed higher energy corrected milk yield for HPSW and FFW (42.9 and 43.9 kg/d respectively) than control (40.6 kg/d). When compared to control, feeding HPSW and FFW enhanced feed efficiencies (P<0.01) and the values were 1.61, 1.75, and 1.77 for control, HPSW and FFW respectively. As barley grain was replaced with potato co-products, the proportion of nitrogen intake excreted in the urine decreased (P<0.01), with values of 312, 327, and 380 g/kg for HPSW, FFW and control respectively. Also, milk urea nitrogen and the ratio of urine nitrogen to intake nitrogen were lower for HPSW and FFW than in the control, indicating a more efficient utilization of dietary crude protein by dairy cows in treatments containing potato co-products. The inclusion of fried and cooked potato co-products increased (P<0.01) the physically effective neutral detergent fiber of diets measured at zero time from 122 for control to 181 and 172 g/kg DM for HPSW and FFW respectively. Consequently, rumination time (min/day) increased from 417 for control to 527 and 555 for HPSW and FFW respectively, which confirmed the positive effects of heated potato processing co-products on dietary physical properties. In conclusion, the results of the current study showed that replacement of barley grain with fried and cooked potato co-products improved diet physical properties and production performance of Holstein lactating dairy cows.