The present experiment aimed to evaluate the effect of partial replacement of corn with chocolate byproducts, protected fats, or their mixture supplemented with zinc in the diet of lactating cows on feed utilization and lactation performance for 90 days. Fifty multiparous Holstein cows (565±25 kg BW, 3±1 parity, 7±1 days in milk, a previous milk production of 35±2.9 kg/d), were randomly assigned to 5 treatments in a completely randomized design. The control diet contained (per kg DM): 412 g concentrate feed mixture, 412 g corn silage, and 176 g berseem hay. The control diet was supplemented with 1 g of zinc daily (Zinc diet). In the other diets, each kg of crushed corn grain was replaced with (DM basis) 600 g chocolate byproducts (CH diet), 400 g protected fats (PF diet), or 500 g of chocolate byproducts and protected fats mixture (1:1 DM basis) (CHPF diet). Both amounts of protected fats and chocolate byproducts had the same energy concentration as 1 kg of corn. The total mixed ration was prepared and distributed using a horizontal mixer system after mixing for 20 min. Chemical analysis showed that the replacement minimally affected the composition of the total mixed rations. Additionally, treatments did not affect feed intake. Compared to the control treatment, the zinc treatment did not affect milk production, milk composition, or feed efficiency. Increased (P<0.05) daily production of milk and component yields, and feed efficiency as well as fat concentration were observed by the CH, PF and CHPF treatments. Without affecting other measured blood parameters or hematocrit, treatments increased (P<0.05) the concentrations of total proteins, albumin, glucose, cholesterol, triglyceride, and zinc in the blood of cows. Additionally, the CH, PF and CHPF treatments increased (P<0.01) the digestibility of nutrients compared to the control treatment. It is concluded that the addition of zinc to the control did not affect cow performance; however, its addition to chocolate byproducts, protected fats, or their mixture to partially replace corn improved the performance of cows.

The present experiment aimed to evaluate the partial replacement of corn with chocolate byproducts or protected fats in the diet of lactating cows on feed utilization, blood profile and lactation performance. Fifty multiparous Holstein cows (560±22 kg BW, 3±1 parity, 7±1 days in milk, and previous milk production of 34±3 kg/d), were randomly assigned to 5 treatments in a completely randomized design for 90 days. The control diet contained a concentrate feed mixture containing (per kg DM 412 g concentrate feed mixture, 412 g corn silage, and 176 g berseem hay). The control diet contained 17.6% crushed corn (DM basis). In another treatment, the control diet was supplemented with 1 g chromium daily (Chromium diet). In the other diets, each kg of crushed corn grain was replaced with 600 g chocolate byproducts (CH diet), 400 g protected fats (PF diet), or 500 g of chocolate byproducts and protected fats mixture (1:1 DM basis) (CHPF diet), DM basis, and each of the diets was also supplemented with 1 g chromium daily. Both amounts of protected fats and chocolate byproducts had the same energy concentration as 1 kg of corn. Without affecting feed intake, the replacement increased (P<0.01) milk production, milk fat concentration, and feed efficiency. The replacement (P<0.05) increased the concentrations of serum total proteins, albumin, glucose, cholesterol, triglyceride, and chromium in comparison with the control diet. Higher (P<0.001) nutrient digestibility was observed with CH, PF, and CHPF treatments. It is concluded that chromium supplementation did not affect feed utilization or cows performance; however, partial replacement of corn with chromium supplemented protected fat, chocolate byproducts or their mixture improved milk production and feed efficiency.

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