Effects of heat-stress-reducing systems on blood constituents, milk production and milk quality of Holstein and Jersey cows and heifers on pasture.

The objective of this study was to evaluate the influence of different heat-stress-reducing systems, i.e., sprinkler + artificial shade, shower + artificial shade, and artificial shade, on serum mineral, hormonal, hematological, and metabolite profiles, on milk production, and milk composition in lactating cows and pubertal heifers of Holstein and Jersey breeds. For this purpose, 12 animals were used: 3 Holstein cows with an average (mean ± SD) body weight of 600 ± 30 kg, 53 ± 11 months of age, and milk yield of 27 ± 3.5 kg/day; 3 Jersey cows with an average body weight of 370 ± 11 kg, 40 ± 6 months of age, and milk production of 11 ± 1.5 kg/day; 3 Holstein heifers (325 ± 25 kg and 16 ± 0.6 months of age); and 3 Jersey heifers (250 ± 25 kg and 13 ± 0.6 months of age). Animals were used in a replicated 3 × 3 Latin square design with a 3 × 2 × 2 factorial arrangement of treatments that included three treatments (sprinkler + artificial shade, shower + artificial shade, and artificial shade), two breeds (Holstein, Jersey), and two physiological stages (lactating cows, heifers). The experimental treatments influenced (P < 0.05) the concentrations of triiodothyronine, with the shower and shade systems showing greater and similar concentrations (99.5 and 96.3 µg/dL, respectively) when compared with sprinkler treatment (89.2 µg/dL). There was an effect (P < 0.05) of breed on the concentrations of Na + , K + , hemoglobin, hematocrit and mean corpuscular volume levels with the Holsteins having lower levels of Na + , K + , hemoglobin, hematocrit and mean corpuscular volume (101.1, 4.0 ng/mL, 11.2 g/dL, 24.7%, and 42.3 µm3, respectively) than the Jerseys (106.5 and 4.3 ng/mL, 12.4 g/dL, 27.7%, and 46.3 µm3, respectively. Total cholesterol and high-density lipoproteins were influenced by physiological stage (P < 0.05). Concentrations of cholesterol and high-density lipoproteins were higher for cows (94.1, and 56.9 mg/dL, respectively) than for heifers (56.9 and 42,9 mf/dL, respectively). Milk production and fat content were affected (P < 0.05) by breed (P < 0.05), with Holstein cows producing more milk (23.9 kg/day) than Jersey cows (12.0 kg/day), but Jersey cows had higher fat concentration (4.6%) than Holstein cows (3.0%). Therefore, the three different thermal-stress-reducing-systems tested were able to maintain the serum biomarkers within normal physiological ranges. However, the most appropriate thermal-stress-reducing-systems would be a sprinkler systema because it uses less water compared with the shower system.

Yerba mate (Ilex paraguariensis) as a source of antioxidants with soybean grain in supplementation of lactating ewes reared in tropical pastures.

The hypothesis tested is that the association of soybean grain and yerba mate as an antioxidant source can increase the concentration of polyunsaturated fatty acids (PUFA) with lower oxidation of milk from lactating ewes reared in tropical pastures. Sixteen ewes were randomly distributed in a 2x2 factorial scheme (with or without yerba mate at 110 g / kg of dry matter (DM); with or without soybean grain at 210 g/kg of DM). Yerba mate intake reduced DM intake, and concentrations of ether extract (EE), protein, lactose, defatted dry extract, density, omega-3 concentrations, and the ratio between saturated/monounsaturated fatty acids (FA), but increased the concentration of monounsaturated FA and the sequestering power of free radicals by DPPH without altering the concentrations of conjugated dienes and the concentrations of substances reactive to thiobarbituric acid in milk. Supplementation with soybean grain decreased the birth weight of the lambs and increased the concentrations of conjugated linoleic acid (CLA), PUFA, omega - 6, omega ratio - 6/omega - 3, and total blood cholesterol. The addition of yerba mate did not influence the oxidative profile of milk. Supplementation with soybean grain improved the FA profile of milk, increasing the concentrations of CLA and PUFA. The results suggest that the association of yerba mate and soybean grain helps to improve the fat quality of milk from ewes raised in tropical pastures, as shown by the enhanced antioxidant activity, although it does not help prevent oxidation of milk rich in PUFA.