The purpose of this study was to evaluate the effect of mastitis on the reproductive performance in crossbred cows. Experimental cows (32) were screened for SCM incidence (24) modified Californian Mastitis Test (mCMT), increased somatic cell count (SCC, between 2.5 - 8.0 × 105 /ml), higher electric conductivity (EC) of milk (>4.27) and abnormal milk. Based on this, the cows were divided into four groups, group I- cows were without any clinical symptom of mastitis, group II- cows with chronic sub-clinical mastitis without clinical signs, group III - cows with clinical mastitis before first artificial insemination (AI) and group IV - cows with clinical mastitis after first AI. Each group of experimental cows consisted of 8 animals. The reproductive performance of different groups revealed that number of days to first AI (FPAI), inter-estrus interval, service per conception and days open were higher (<0.05) in mastitis groups as compared to healthy group of cows, whereas FPAI was higher (p <0.05) for group III than group IV cows. The inter-estrus interval, service per conception, days open was higher (p<0.05) for group IV than group III cows. Non-significant variation were found between the chronic sub-clinical and clinical mastitis cows except days open, which was more (p<0.05) in clinical mastitis group cows. It was concluded that incidence of clinical mastitis after AI had a profound negative effect on reproductive performance than other group cows.
Mastitis is defined as an inflammatory reaction of the mammary gland, which can be caused by many factors such as infection due to pathogens, trauma or injury to the udder and irritants (Physical and chemical; Philpot and Nickerson, 2000). Dairy cattle are worldwide affected by mastitis in clinical as well as in subclinical form. Mastitis an intramammary infection causes the deterioration of ovarian follicular responses in cows, resulting in low fertility (Wolfenson et al., 2015). Mastitis is still the most costly and most dreaded disease of dairy farmers because of curtail milk production, treatment costs, milk discarding and premature culling (Philpot and Nickerson, 2000; Yang et al., 2012). The negative effects of mastitis are not only limited to this but it indirectly influence the reproductive performance of dairy cows. Many studies have confirmed that mastitis has deleterious effects on reproductive performances of lactating cows and affects the net profitability of a dairy farm (Ahmadzadeh et al., 2009; Gunay and Gunay, 2008; Nava-Trujillo et al., 2010; Bachay et al., 2011). Some researcher (Ahmadzadeh et al., 2009) explained clinical mastitis effects on reproductive performance by increase in days open, number of days to first service and poor conception rate. The negative effect of mastitis on fertility occurred either before AI or after the first AI postpartum, resulting in decreased reproductive efficiency (Santos et al., 2004). The adverse effects of mastitis are due to complication in pregnancy (ovulation, fertilization, implantation and maintenance of pregnancy) process and delay of the postpartum ovarian function. Cows suffering from mastitis in early lactation before first AI take longer time to reactivate their ovarian function, which limits the Profitable and efficient milk production from a dairy cow. Keeping this in view of negative effect, the present study was carried out to find out the effect of mastitis incidence on reproductive performances of cross bred cows maintained in a tropical condition.
Materials and Methods
Selection of Animals and Experimental Design
The experiment was carried out on 32 crossbred cows in third parity. The cows were selected from the experimental herd of National Dairy Research Institute (NDRI), Karnal, Haryana (latitude 29.43° N & longitude 77.2° E), India. The experimental animals were divided into groups on the basis of mCMT score, SCC, EC values and clinical sign, cows with negative mCMT score, low SCC (<250000 cells/ml) and lower EC value throughout experimental period. The healthy group (n=8), cows with positive (+/++/+++) mCMT score and higher SCC (2.5 – 8.0 × 105cells/ml) for at least one month were taken in SCM group (n=8). The clinical mastitis cows were selected on the basis of clinical sign and was divided into group as cows with clinical mastitis before AI (n=8) and cows with clinical mastitis after AI (n=8). The animals were kept in a loose housing system and wares were fed as per the standard feeding practices followed at the livestock farm. Green fodder and water was available ad lib all the times to experimental cows.
Milk and Blood Collection Schedule
The experimental cows were milked twice daily at 6 am and 6 pm in a double row-herringbone milking parlor equipped with automatic milking machine. Milk samples were collected from healthy and infected quarter of sub-clinical mastitis cows at weekly intervals from day 54 of lactation till conception. Sub clinical mastitis cows were determined by modified California mastitis test (Sastry, 1978). EC was measured by electrical conductivity meter (Model LT-26). SCC of milk samples was determined by a Lactoscan automatic analyzer.
Measurement of Reproductive Performances
The reproductive performance parameters like calving to first service interval, inter-estrus interval, days open, the number of services per conception and calving interval were recorded during the experiment. All reproductive records of healthy and mastitis cows with sub-clinical and clinical mastitis before and after first AI. AI or between first AI and pregnancy were obtained from farm livestock records. The status of pregnancy was confirmed by rectal palpation between 60–65 days post insemination.
Statistical analysis of data was performed by using SYSTAT software package. Mean and standard error was calculated and the significance at 5% was tested by employing analysis of variance (ANOVA).
Results and Discussion
The mean value of EC for quarters of healthy cows, subclinical and clinical mastitis cows were significantly 3.82±0.06, 4.27±0.05, 4.94±014 mhos, respectively and varied significantly (p<0.05) between healthy and infected cows (Sharma et al., 2017). The mastitis was determined as per the mCMT score as negative (no gel formation) in healthy groups of cows, +2 to +3 in SCM cows and +4 in clinical mastitis cows. Total SCC in milk of healthy cows were 2.05±0.23 lakh per ml of milk, which increased significantly (p<0.05) to 7.48±0.28 in SCM cows and was again to 12.18±0.56 lakh per ml in milk of clinically infected cows. Mean ± SE values of FPAI (in days) (110.5b ± 5.83), inter-estrus interval (40b ± 1.4 days) and number of services per conception (2.75b ± 0.18) were significantly (p<0.05) greater for clinical mastitis groups of cows as compared to FPAI (83.75a± 4.39d), inter-estrus interval (30.2a± 1.40d) and number of services per conception (1.75a ± 0.25) of healthy group of cows (Table 1 and 2; Fig. 1, 2, 3 and 4). There were no significant variation between sub-clinical and clinical mastitis group of cows, except days open which was significantly (p<0.05) higher (169.61c ± 6.10) for clinical mastitis cows as compared to sub-clinical mastitis (148b ± 8.0) and healthy (105.85a± 10.44) cows.
Table 1: Reproductive performance in healthy and mastitis group of cows
|Days to FPAI||83.75a±4.39||102.25b±6.36||110.5b±5.83|
|Inter estrus interval||30.2a±1.40||38b±1.30||40b±1.4|
|Service per conception||1.75a±0.25||2.5b±0.19||2.75b±.18|
abc Means with different superscripts within a row differ significantly (P<0.05)
Table 2: Effect of clinical mastitis with occurrence of time (CM with before first AI and after first AI) (Mean ± SE) on reproductive parameters of lactating crossbred cows
|Occurrence of Mastitis||FPAI||Inter-estrus interval||Service per conception||Days open|
ab Means with different superscripts within a row differ significantly (P<0.05)
Fig 1: Average first post-partum AI (FPAI) and Inter-estrus interval in days for healthy and mastitis cows
Fig 2: Average number of services per conception and days open in healthy and mastitis cows
The mean values of FPAI (110.5b ± 5.83 d), inter-estrus interval (40b ± 1.4d) and number of services per conception (2.75b ± 0.18) were numerically higher for clinical mastitis groups of cows as compared to FPAI (102.25b ± 6.36d), inter-estrus interval (38b± 1.30d) and number of services per conception (2.5b± 0.19) in sub-clinical mastitis cows. Clinical mastitis after AI adversely influenced reproductive performance than the cows with clinical mastitis before AI. However, FPAI was significantly (p <0.05) greater (123a ±5.09d) for cows suffering with clinical mastitis before first AI in comparison to (96b±3.39d) cows having clinical mastitis after AI. The mean values of inter-estrus interval (44.78b±1.88d), number of services per conception (3.25b±0.25), and days open (178.66b±6.82) were higher (p <0.05) for clinical mastitis cows after AI as compared to values of inter-estrus interval (35a±2.16 d), number of services per conception (2.25a±0.25) and days open (160.33a±6.65 d) for group of cows with clinical mastitis before AI.
Fig 3: Influence of clinical mastitis incidence (before AI and after AI) during early lactation on days to FPAI and Inter-estrus interval
Fig 4: Influence of clinical mastitis incidence (before AI and after AI) during early lactation on service per conception and days open
The results of the study clearly elucidated the negative effects of sub-clinical and clinical mastitis on reproductive performance. Cows that had mastitis before AI showed significantly greater number of days to first AI than the other group of cows and corroborates the previous finding (Barker et al., 1998; Santos et al., 2004; Schrick et al., 2001). The inadequate follicular development; LH surge blockage or decreased estrogen synthesis results in the loss of behavioral estrus (Barker et al., 1998; Schrick et al., 2001; Yang et al., 2012). These factors could explain the delayed first postpartum AI in cows experiencing mastitis before first AI in the current and previous studies. Both clinical and subclinical mastitis have association with a reduction in reproductive performance (Hudson et al., 2012) and due to the reason the number of AI per conception was greater for in cows having clinical mastitis after the first service (group IV) than the cows with clinical mastitis before first AI. It has been found that clinical mastitis in early lactation markedly influence reproductive performances of lactating Jersey cows (Barker et al., 1998) as reported in the present study. The impaired reproductive performance of cows could be due to the direct depression of estradiol production which impair GnRH and LH production in mastitis cows (Lavon et al., 2010). Further, elevated concentrations of serum PGF2α is associated with mastitis (Santos et al., 2004) resulting in decreased embryonic development, increased number of services/conception and number of days to conception. In our study, out of 8 cows in group III, 5 had increased services per conception that accounts 37% of cows that had sub-clinical mastitis in early lactation. Thus occurrence of acute mastitis before AI can delay the calving to first service interval, increases the calving to conception interval and elevated the number of services per conception (Gunay and Gunay, 2008). The results of present study provide evidence that the consequences of mastitis result in suppression of reproductive performance.
The occurrence of mastitis in early lactation have negative impact on reproductive performance by increasing the number of days to first AI, inter-estrus intervals, service per conception, days open than healthy cows resulting in impaired production and reproduction efficiency. Therefore, incidence of sub-clinical mastitis in early lactation needs to be monitored by mCMT to make dairy farm more profitable.
The authors would like to thank the Director of NDRI, Karnal for providing the facilities for the execution of this work.
The experimental protocol was duly cleared by the Institute Animal Ethic Committee.
Conflict of Interest
The authors declare that they have no conflict of interest.