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Interactions between Metabolic Load and Dairy Cow Welfare-related Parameters in Herbage based Feeding Systems
In Switzerland, herbage feeding with only little input of concentrates plays an important role in milk production. The objective here was to investigate the effects of a solely herbage based diet on production, metabolic, endocrine and welfare-related parameters of dairy cows. Twenty-five multiparous Holstein dairy cows were divided into two groups according to their previous lactation yield (4679-10808 kg): a control (C, n=13) and a treatment group (nC, n=12) from wk 3 antepartum until wk 8 pp. Within C and nC, the median of the preceding lactation yields (7752 kg) was used to split cows into a high (CH, nCH) and low yielding (CL, nCL) subgroup. While CH/CL received fresh cut herbage plus additional concentrate according to their estiamted energy and nutrient requirements, no concentrate was fed to nCH/nCL throughout the experiment. Milk yield and DMI were recorded daily. Blood samples were weekly and analyzed for IGF-1, glucose, NEFA, BHBA, and welfare-related parameters haptoglobin (Hp), serum amyloid A (SAA), beta-endorphin (BE) and alkaline phosphatase (AP). Saliva samples were taken bi-weekly and analyzed for cortisol. Data were analyzed using mixed models. Throughout the study, CH had a higher milk yield (35.9 kg/d) compared to the other subgroups (27.2-31.7 kg/d, P < 0.05). Plasma glucose (3.51 vs. 3.72 mmol/L) and IGF-1 (66.0 vs. 78.9 ng/mL) concentrations were lower in nCH/nCL compared to CH/CL cows (P < 0.05). Plasma NEFA and BHBA concentrations were higher in nCH (1.1 and 1.6 mmol/L) compared to the other subgroups (0.5 and 0.6 mmol/L, P < 0.05). Saliva cortisol (0.60 vs. 0.68 ng/mL), SAA (0.60 vs. 0.87 µg/mL), Hp (728 vs. 909 U/L), BE (30.0 vs. 32.1 pg/mL) and AP (48.5 vs 45.9 mg/mL) were not different among C and nC. In conclusion, in herbage dominated feeding systems without supplementary concentrate especially high yielding dairy cows experience a higher metabolic load during early lactation leading in turn to a reduced lactational performance compared to cows of a similar potential fed according to their needs. Low yielding dairy cows can perform well without concentrate supplementation. Interestingly, the commonly accepted welfare-related parameters cortisol, Hp, SAA, BE and AP did not indicate a reduced animal welfare induced by metabolic stress.
Keywords: welfare, metabolism, herbage feeding, dairy cow