Dairy Cows' Health during Alpine Summer Grazing as Assessed by Milk Traits, Including Differential Somatic Cell Count: A Case Study from Italy.

Giovanni Niero,Massimo De Marchi,Cristina Pornaro,Giulio Visentin,Tania Bobbo,Martino Cassandro,Mauro Penasa,Simone Callegaro,Giulio Cozzi

doi:10.3390/ani11040981

Giovanni Niero, Massimo De Marchi + Show 7 more

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https://doi.org/10.3390/ani11040981

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Abstract

Simple SummaryDairy herds in alpine areas usually adopt summer grazing, mainly to reduce feeding costs. This practice is related to the maintenance of local traditions and to the manufacturing of niche dairy products. However, it is important to assess the impact of this practice on cattle health. This case study investigated how milk-related health traits vary across extensive grazing during the summer period, using data collected in a dairy herd whose cows were repeatedly controlled for individual milk samples. Although the transition from barn farming to pasture led to a reduction in milk production, proper grazing management can make dairy cows more resilient in terms of udder health and metabolic efficiency. Findings of the present research report suggested that pasture can be adopted to maintain dairy herd sustainability without impairing animal health.Extensive summer grazing is a dairy herd management practice frequently adopted in mountainous areas. Nowadays, this activity is threatened by its high labour demand, but it is fundamental for environmental, touristic and economic implications, as well as for the preservation of social and cultural traditions. Scarce information on the effects of such low-input farming systems on cattle health is available. Therefore, the present case study aimed at investigating how grazing may affect the health status of dairy cows by using milk traits routinely available from the national milk recording scheme. The research involved a dairy herd of 52 Simmental and 19 Holstein × Simmental crossbred cows. The herd had access to the pasture according to a rotational grazing scheme from late spring up to the end of summer. A total of 616 test day records collected immediately before and during the grazing season were used. Individual milk yield was registered during the milking procedure. Milk samples were analysed for composition (fat, protein, casein and lactose contents) and health-related milk indicators (electrical conductivity, urea and β-hydroxybutyrate) using mid-infrared spectroscopy. Somatic cell count (SCC) and differential SCC were also determined. Data were analysed with a linear mixed model, which included the fixed effects of the period of sampling, cow breed, stage of lactation and parity, and the random effects of cow nested within breed and the residual. The transition from barn farming to pasture had a negative effect on milk yield, together with a small deterioration of fat and protein percentages. Health-related milk indicators showed a minor deterioration of the fat to protein ratio, differential SCC and electrical conductivity, particularly towards the end of the grazing season, whereas the somatic cell score and β-hydroxybutyrate were relatively constant. Overall, the study showed that, when properly managed, pasture grazing does not have detrimental effects on dairy cows in terms of udder health and efficiency. Therefore, the proper management of cows on pasture can be a valuable solution to preserve the economic, social and environmental sustainability of small dairy farms in the alpine regions, without impairing cows’ health.

Highlights

Low-input dairy livestock systems usually adopt pasture grazing in specific periods of the year, in spring and summer; this is primarily dictated by pasture availability in those periods and by economic reasons [1,2,3,4]
The indicators of udder health status, namely, somatic cell score (SCS), differential somatic cell count (DSCC) and EC, averaged 2.81, 65.46% and 870.63 mS, respectively, with coefficients of variation that ranged from 8.77% (EC) to 60.42% (SCS; Table 2)
Summer grazing is a management strategy widely adopted in low-input dairy systems located in the mountains to maintain herd profitability, preserve the environment and increase milk value

Summary

Introduction

Low-input dairy livestock systems usually adopt pasture grazing in specific periods of the year, in spring and summer; this is primarily dictated by pasture availability in those periods and by economic reasons [1,2,3,4]. Mountainous dairy farmers traditionally keep both replacement heifers and milking cows indoors during the cold months of the year to subsequently allow the herd to access the pasture when climatic conditions are more favourable. This practice is important for dairy farmers, and it has economic, social, historical, environmental and touristic implications [5,6,7]. Dairy cows may experience a negative energy status when exposed to grazing, which is reflected in a reduction in milk yield [5] and loss of body condition; a common practice is to provide concentrate supplementation to maintain the milk production of the herd and body fat reserves [18]

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