Association Between Recycled Manure Solids Bedding and Subclinical Mastitis Incidence: A Canadian Cohort Study

Conditioner application improves bedding quality and bacterial composition with potential beneficial impacts for dairy cow's health

Recycled manure solids (RMS) is used as bedding material in cow housing but can be at risk for pathogens development. Cows spend several hours per day lying down, contributing to the transfer of potential mastitis pathogens from the bedding to the udder. The effect of a bacterial conditioner (Manure Pro, MP) application was studied on RMS-bedding and milk qualities and on animal health. MP product was applied on bedding once a week for 3 months. Bedding and teat skin samples were collected from Control and MP groups at D01, D51, and D90 and analyzed through 16S rRNA amplicon sequencing. MP application modified bacterial profiles and diversity. Control bedding was significantly associated with potential mastitis pathogens, while no taxa of potential health risk were significantly detected in MP beddings. Functional prediction identified enrichment of metabolic pathways of agronomic interest in MP beddings. Significant associations with potential mastitis pathogens were mainly observed in Control teat skin samples. Finally, significantly better hygiene and lower Somatic Cell Counts in milk were observed for cows from MP group, while no group impact was observed on milk quality and microbiota. No dissemination of MP strains was observed from bedding to teats or milk.

IMPORTANCE

The use of Manure Pro (MP) conditioner improved recycled manure solids-bedding quality and this higher sanitary condition had further impacts on dairy cows' health with less potential mastitis pathogens significantly associated with bedding and teat skin samples of animals from MP group. The animals also presented an improved inflammation status, while milk quality was not modified. The use of MP conditioner on bedding may be of interest in controlling the risk of mastitis onset for dairy cows and further associated costs.

Ability of unsterilized recycled manure solids bedding to support growth of Klebsiella pneumoniae and Escherichia coli

Although recycled manure solids (RMS) bedding is used on dairy farms, it could allow bacterial growth when contaminated by feces and thus increase the incidence of clinical mastitis in cows. The objective of this study was to describe bacterial growth in three different types of RMS bedding, as well as in sand, when samples were experimentally inoculated with Escherichia coli and Klebsiella pneumoniae. Two 3-day trials were conducted, during which treatments included inoculating bedding samples with E. coli and K. pneumoniae, as well as no inoculation. The trial was repeated 3 times for each bedding sample on each day. Samples were incubated at 15°C for 3 d and bacterial counts were measured every day. After inoculation, there was no significant K. pneumoniae or E. coli growth phase during the trial in those RMS samples that were prepared either in a container or in a heap. Recycled manure solids and sand samples prepared in a rotary drum, however, showed a similar active growth phase of K. pneumoniae during the first 24 h of the trial. Moreover, a significant E. coli growth phase was observed in the samples of sand bedding in the first 24 h. The 3 different types of RMS bedding samples did not react in a similar manner to coliform inoculation. No active growth phase was observed in bedding samples already containing a high bacterial concentration following inoculation with coliforms.

Impact of recycled manure solids bedding on hygiene and odds of hock lesions in dairy cows

The use of recycled manure solids (RMS) as bedding for dairy cows has become more popular over the last decade. Once producers own the RMS producing equipment, they are not restricted in the amount of bedding they can use in stalls, due to its large availability and low production costs. Thus, they are usually able to provide a soft lying area for their cows. Nevertheless, the potential positive impact of RMS on cows' hygiene and odds of hock lesions is not clearly demonstrated. Objectives of this research were, therefore, to compare RMS-bedded cows' hygiene level and odds of hock lesions to straw-bedded cows (comparative group). To achieve this, an observational cross-sectional study was conducted in 27 RMS- and 61 straw-bedded herds. During the farm visit, 30 cows per herd were scored for hygiene of three body regions (udder, lower legs and flank/upper legs) using a score ranging from 1 to 4 (1 being the cleanest and 4 the dirtiest). In addition, both hocks were scored (0 to 3) to evaluate the presence of lesions (0 when there was no lesion and 3 when a swelling protrusion > 2.5 cm was present). Continuation-ratio models were used to compute the odds of having a given score to the odds of having a lower score. Recycled manure solids usage was associated with lower odds of having an udder hygiene score ≥3 [odds ratio (OR): 0.43; 95% CI: 0.20, 0.95] and of having a score of 4 (OR: 0.29; 95% CI: 0.09, 0.93). It was also associated, compared to straw, with cleaner lower legs. We observed lower odds of having a score ≥2 (OR: 0.45; 95% CI: 0.21, 0.98), ≥3 (OR: 0.16; 95% CI: 0.04, 0.66), or a score of 4 (OR: 0.07; 95% CI: 0.01, 0.40) in RMS-bedded herds. No statistically significant association could be highlighted between RMS usage and flank/upper legs hygiene. Furthermore, we did not observe any statistically significant associations between bedding type (RMS vs. straw) and odds of hock lesions. In conclusion, cows bedded with RMS had generally cleaner udders and cleaner lower legs than straw-bedded ones. No association was found between bedding type and odds of hock lesions.