The goal of our study was to investigate the frequency of bovine mastitis in dairy cows and identify potential risk factors.
Mastitis prevalence
Cow level
According to the results shown in Table 1, we discovered a significant incidence of mastitis at the cow level, with a rate of 68.5%, using both clinical inspections of the udder and the California Mastitis test (CMT). The prevalence rate contrasts from that reported by
Hocine et al., (2021) in Algeria and
Belay et al., (2022) in Ethiopia, where the prevalence rates were 41.66% and 17.1%, respectively. Our findings, however, are consistent with prior research in Ethiopia, such as studies by
Abebe et al., (2016) and
Melesse and Minyahil (2019), which found prevalence rates of 64.3% and 73%, respectively, as well as
Maalaoui et al., (2021) in Tunisia, who reported a prevalence rate of 60.3%. These discrepancies may be attributable to regional, environmental and agroecological variables, changes in farm management, husbandry methods, production systems and the investigators’ research methodology or equipment. Mastitis is also a complicated illness involving the combination of animal risk factors and causative agents, and its incidence varies
(Radostits et al., 2007).
In our study, 65.4% of dairy cows had subclinical mastitis. This number is comparable to other studies done in Algeria
(Fartas et al., 2017; Meskini et al., 2021b; Ghallache et al., 2021), which showed prevalence rates of 61.6%, 62.8% and 66.4%, respectively. Nonetheless, the prevalence rate in our research was greater than that discovered by
KAKI et al., (2019) in Bejaia (26%) and
Ferroudj et al., (2021) in Algeria’s Dry land area (12.9%). The prevalence rate in our study was also lower than the findings of
Boufaida et al., (2012) in Algeria’s Est area (79%) and
Ouakli et al., (2022) in Blida province (71%).
In this study, the prevalence of clinical mastitis at the cow level was 3.1%, which is similar with the findings of
Abebe et al., (2016) in Ethiopia (3.4%) but higher than the prevalence reported by
Belay et al., (2022) of 1.9%. It is crucial to note, however, that the prevalence of subclinical mastitis was significantly greater than that of clinical mastitis. This disparity might be attributed to a failure to pay attention to subclinical mastitis when treating clinical infections
(Lakew et al., 2019). Subclinical mastitis is 15-40 times more common than clinical mastitis, lasts longer, has a large economic burden and frequently precedes clinical mastitis, according to
Seegers et al., (2003). According to
Erskine (2003), the udder’s defensive mechanism tends to reduce the degree of infection and it has been hypothesized that the risk of subclinical mastitis is higher than that of clinical mastitis.
Quarter level
Table 2 indicates that the total prevalence of mastitis in the quarters was 35.19%, which is comparable to the findings of
Abebe et al., (2016) in Ethiopia (34.7%), Dinaol
Belina et al., (2016) with (29.2%) and
Elbably and Asmaa (2013) in Egypt (29.08%). The hindquarters were more impacted than the forequarters, particularly the right hindquarters, which is consistent with earlier study noted above.
Zeryehun et al., (2013) ascribed the higher infection rates in these quarters to their high production capacity and greater risk of fecal and environmental contamination.
Mastitis risk factors
Intrinsic risk factors (animal risk factors)
As shown in Table 3, the findings revealed a substantial connection between the frequency of bovine mastitis and age and parity number (p<0.05).
Older cows showed a greater frequency of mastitis than younger cows, with cows aged 6-7 years having the greatest prevalence (87.50%) compared to cows aged 2 or 3 years (57.50%). In addition, mastitis was shown to be more prevalent in multiparous cows (76.47%) than in primiparous cows (63.33%), which is similar with earlier studies by
Zeryehun et al., (2013) and
Belay et al., (2022). The greater prevalence of mastitis in older cows in this research may be attributable to bigger teats and more relaxed sphincter muscles, making it easier for infectious agents to enter and grow in the udder
(Radostits et al., 2007). According to
Abebe et al., (2016), older cows with four or more parities are especially sensitive to mastitis due to their pendulous udders and mastitis history, which render the teats and udder more susceptible to damage and infection.
The research additionally showed that the stage of lactation had a significant effect on the prevalence of mastitis (p< 0.05), with a larger relative frequency in the late lactation stage (80.56%) compared to the early (67.21%) and mid-lactation phases (60.53%). This conclusion supports previous findings by
Youssif et al., (2021) and
Maalaoui et al., (2021). Mastitis is more common in late lactation due to recurrent and continuous exposure to infections with infectious germs during milking procedures or the removal of the teat “plug”
(Youssif et al., 2021).
According to the findings of this study, no statistically significant correlation (P>0.05) was found between breed and mastitis or between milk output level and mastitis prevalence. This contrasts previous studies that demonstrated a substantial influence of these parameters on mastitis incidence, such as (
Asmare and Kassa, 2017;
Melesse and Minyahil, 2019) for milk output production and
Moges et al., (2012) and
Belay et al., (2022) for breed risk factors.
This lack of significance in our analysis might be related to breed sample variations. Our study used only imported breeds, whereas other studies used native and crossbred animals, which are known to be more resistant to mastitis infection. High-yielding cows are more prone to mastitis than low-yielding cows, according to
(Radostits et al., 2007).
This might be due to the increased possibility of injuries developing in bigger udders, resulting in a higher risk of disease introduction. Also, the stress associated with excessive milk production may have an impact on the animal’s defensive system.
Extrinsic risk factors (management risk factors)
Data in Table 4 show that Cow cleanliness, particularly of the legs and udder, has been recognized as a risk factor for mastitis; Cows with low hygiene had a greater mastitis incidence (68.18%) than cows with good hygiene (55.56%), consistent with findings by
Abebe et al., (2016) and
Melesse and Minyahil, (2019).
According to
Weigel et al., (2018), environmental conditions and herd management practices have a substantial influence on animal well-being and health, keeping the herd clean and comfortable helps lower the occurrence and severity of mastitis.
While using a biocide or soap to clean the udder (instead of using only water) was proven to have a substantial influence on lowering mastitis cases with rates of 42.86%, 60.53% and 74.12%, respectively. Farmers frequently refuse to use detergents for fear of affecting milk quality during milk control.
Wiping the udder after cleaning had a considerable influence on the incidence of mastitis 60.98% when this operation is performed versus 71.91% when it is not.
Whereas
Idriss et al., (2013) claim that teat canals can be partially open for 1-2 hours after milking, feeding cows soon after milking is critical to prevent infections from readily infiltrating via the open teat canal. However, this study observed no significant influence on mastitis, which might be ascribed to the animals not standing for 1-2 hours due to a lack of acceptable quality and amount of feed (
Asmare and Kassa, 2017).
This research reveals that previous mastitis history had no significant impact on mastitis incidence, in contrast to several studies such as
Melesse and Minyahil (2019), who reported that previous udder infections were more likely to be re-infected than those with no previous exposure. This could be attributed to previously exposed cows retaining carriers and the limited efficacy of medications used to treat mastitis in the research area.
According to the findings of this study, treating dry cows had a favorable effect on lowering the prevalence of mastitis (p<0.05). As shown by
Peterson-Wolfe et al., (2010), cows are most vulnerable to mastitis infections in the last seven to ten days of the dry season. As a result, it is advised that the early dry phase therapy be repeated two weeks before calving. Yet, because of fears about abortion, many farmers in the study declined to carry out systematic treatments during this time period.