Effects of calcium ammonium nitrate fed to dairy cows on nutrient intake and digestibility, milk quality, microbial protein synthesis, and ruminal fermentation parameters.

We evaluated the effects of supplemental calcium ammonium nitrate (CAN) fed to dairy cows on dry matter (DM) intake, nutrient digestibility, milk quality, microbial protein synthesis, and ruminal fermentation. Six multiparous Holstein cows at 106 ± 14.8 d in milk, with 551 ± 21.8 kg of body weight were used in a replicated 3 × 3 Latin square design. Experimental period lasted 21 d, with 14 d for an adaptation phase and 7 d for sampling and data collection. Cows were randomly assigned to receive the following treatments: URE, 12 g of urea/kg of DM as a control group; CAN15, 15 g of CAN/kg of DM; and CAN30, 30 g of CAN/kg of DM. Supplemental CAN reduced DM intake (URE 19.0 vs. CAN15 18.9 vs. CAN30 16.5 kg/d). No treatment effects were observed for apparent digestibility of DM, organic matter, crude protein, ether extract, and neutral detergent fiber; however, CAN supplementation linearly increased nonfiber carbohydrate digestibility. Milk yield was not affected by treatments (average = 23.1 kg/d), whereas energy-corrected milk (ECM) and 3.5% fat-corrected milk (FCM) decreased as the levels of CAN increased. Nitrate residue in milk increased linearly (URE 0.30 vs. CAN15 0.33 vs. CAN30 0.38 mg/L); however, treatments did not affect nitrite concentration (average: 0.042 mg/L). Milk fat concentration was decreased (URE 3.39 vs. CAN15 3.35 vs. CAN30 2.94%), and the proportion of saturated fatty acids was suppressed by CAN supplementation. No treatment effects were observed on the reducing power and thiobarbituric acid reactive substances of milk, whereas conjugated dienes increased linearly (URE 47.6 vs. CAN15 52.7 vs. CAN30 63.4 mmol/g of fat) with CAN supplementation. Treatments had no effect on microbial protein synthesis; however, molar proportion of ruminal acetate and acetate-to-propionate ratio increased with CAN supplementation. Based on the results observed, supplementing CAN at 30 g/kg of DM should not be recommended as an optimal dose because it lowered DM intake along with ECM and 3.5% FCM, although no major changes were observed on milk quality and ruminal fermentation.

Enzymatic effects of Pleurotus ostreatus spent substrate on whole-plant corn silage and performance of lactating goats.

Pleurotus ostreatus (oyster mushroom) synthesizes enzymes that degrade lignin, cellulose, and hemicellulose. The objectives of this study were to evaluate the effect of Pleurotus ostreatus spent substrate (POSS) on whole-plant corn silage (WPCS) chemical composition, antioxidant capacity, lignin monomers, and in vitro digestibility, as well as the performance of lactating goats fed corn silage treated with different levels of POSS. In experiment 1, 4 levels of lignocellulolytic enzymes were tested in a complete randomized design: 0, 10, 20, and 30 mg of lignocellulosic enzymes per kilogram of fresh matter, 4 replicates per treatment (vacuum-sealed bags). The bags were opened 60 d after ensiling. In experiment 2, corn silage treated with 3 enzyme levels (0, 10, or 30 mg/kg of fresh matter) was fed to lactating goats as part of the total mixed ration. Nine lactating Saanen goats (62.68 ± 7.62 kg BW; 44 ± 8 d in milk; 2.91 ± 0.81 kg of milk/day, mean ± SD) were assigned to three 3 × 3 Latin squares. Data were analyzed using the GLIMMIX procedure of SAS (version 9.4, SAS Institute Inc.), and means were compared by linear and quadratic orthogonal contrast. In experiment 1, neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin, and cellulose quadratically decreased in the WPCS treated with POSS. At the nadir point, POSS decreased NDF by 14.1%, ADF by 19.5%, lignin by 9.07%, and cellulose by 22.1% compared with the untreated silage. Therefore, POSS led to a quadratic increase in in vitro dry matter digestibility of WPCS (+8.88% at the vertex) compared with the untreated silage. In experiment 2, POSS quadratically increased the in vivo total-tract ADF digestibility. Also, the concentration of polyphenols in the milk of goats linearly increased with the addition of POSS, and no differences were observed among treatments for milk yield and composition. In summary, adding 10 mg of lignocellulolytic enzymes from POSS per kilogram of fresh matter of whole-plant corn at ensiling had a more evident reduction in lignin and cellulose concentration, leading to greater in vitro digestibility, as well as greater in vivo ADF digestibility; however, milk yield was not different among treatments.