Risk Assessment and Consequences of Retained Placenta for Uterine Health, Reproduction and Milk Yield in Dairy Cows

The objective of the study was to determine the value of metabolic indicators characterising the energy and acid-base metabolism of dairy cows for predicting the risk of retained placenta (RP). The connection between RP and different factors analysed, and the effect of RP on the development of puerperal metritis (PM) as well as on reproduction and milk production was studied. A total of 105 Holstein-Friesian cows were included and sampled between days -14–0 prepartum and then on days 4, 10–14, 28–35, 56–63 and 84–91 postpartum, for metabolic tests. From day 4, at times coinciding with the days of metabolic sampling, uterine involution and metritis were monitored by clinical examination, and from days 28–35 ovarian activity was monitored by ultrasonography. On days -14–0, the plasma non-esterified fatty acids (NEFA) concentration showed a positive Odds Ratio (OR) 102.1, P < 0.05; while urinary net acid-base excretion (NABE) exhibited a negative correlation (OR 0.99; P < 0.05) with the odds of RP. NEFA and NABE were negatively correlated (Pearson’s coefficient: -0.24; P < 0.05). Ketonuria of grade ≥ 2+ increased the probability of RP (OR: Infinite; P < 0.05). On day -14–0 prepartum, elevated plasma NEFA concentration, decreasing urinary NABE and grade ≥ 2+ ketonuria indicates a higher risk of RP. The odds of RP were not influenced by parity, sex and viability of the calf, and the calving assistance. RP increased the risk of PM (OR: 27.3; P < 0.0001). The RP alone did not exert an influence on the metabolic status, reproductive performance or milk production of cows. Risk indicators, energy balance, acid-base metabolism, milk production In recent decades, the milk production of dairy cows has increased steadily, while their reproductive performance has declined. This is mostly due to production diseases, commonly occurring in the peripartal period (Brydl et al. 2003, 2008; Ingvartsen 2006; Thatcher et al. 2006). Retained placenta (RP) is an important disorder of dairy cows, which occurs in 4 to 18% of calvings (Han and Kim 2005). The aetiology of RP is not completely clear. Factors contributing to its occurrence include calving-related factors such as dystocia, stillbirth, twinning, length of gestation (Correa et al. 1993; Han and Kim 2005), parity (Correa et al. 1993), and certain nutritional problems (Laven and Peters 1996). In other cases, no association was found between dystocia (Curtis et al. 1985), parity (Han and Kim 2005) and the development of RP. Oxidative stress may contribute to RP as well. For this reason, the beneficial effect of adequate supplementation with known nutrients (e.g. selenium, zinc, copper, iron and vitamin E, A and C, etc.) required for antioxidant defence has been reported in some (Trinder et al. 1973; Harrison et al. 1984; Miller et al. 1993), but not all (Hidiroglou et al. 1987; Stowe et al. 1988) previous studies. Few data are available on the role of metabolic status preceding the development of RP, more specifically, the disturbances of energy balance and acid-base metabolism as ACTA VET. BRNO 2009, 78: 163–172; doi:10.2754/avb200978010163 Address for correspondence: Dr László Könyves Szent István University Faculty of Veterinary Science H-1078 Budapest, István u. 2 Hungary Phone: +36 1478 4242 Fax: +36 1478 4243 E-mail: [email protected] http://www.vfu.cz/acta-vet/actavet.htm risk factors for RP. It is known that in the peripartal period, dairy cows have a negative energy balance (NEB). The available energy amount depends on the dry matter intake and utilisation, the latter being determined by the rumen microflora (Grummer 1995) and adaptive changes of the ruminal epithelium, which depend on the acid-base conditions within the rumen (Dirksen et al. 1999). Optimally, the majority of cows adapt to the NEB over a longer period of time during a multi-step process consisting of a series of physiological, metabolic and endocrine changes (Ingvartsen 2006). This adaptation process can be followed with the help of indicators such as plasma non-esterified fatty acids (NEFA), acetoacetic acid (AcA), certain metabolic hormones, urinary net acid-base excretion (NABE) (Huszenicza et al. 2002; Brydl et al. 2003; Jorritsma et al. 2003). Deviations from the physiological range indicate disturbances of this adaptation mechanism and, therefore, they can be defined as risk factors or risk indicators. NEB may develop already at the end of gestation (Brydl et al. 2003, 2008; Grummer et al. 2004) and it may contribute to the development of many production diseases such as the fatty liver syndrome and ketosis (Bertics et al. 1992), dystocia (Zamet et al. 1979), or immunosuppression (Goff 2003). Overcondition (Hayirli et al. 2002) as well as management defects and environmental factors resulting in reduced dry matter intake increase the risk of development of prepartum NEB (Grummer et al. 2004). RP has a decisive role in the development of metritis (Kaneene 1995), but ketosis occurring at the early stage of lactation is also a major risk factor (Huszenicza et al. 1998). RP increases the risk of fatty liver syndrome and ketosis (Han and Kim 2005); the latter, in turn, delays the postpartum resumption of cyclic ovarian function and prolongs the interval from calving to first ovulation (Huszenicza et al. 1998; Opsomer et al. 2000). RP and puerperal metritis (PM) prolong the interval from calving to first service and conception and decrease the conception rate (Maizon et al. 2004; Han and Kim 2005). Few sources are available in the literature on strategies for the prevention of production diseases. Early diagnosis and prevention require a thorough knowledge of the risk factors predisposing to their development (Jorritsma et al. 2003; Ingvartsen 2006; Mulligan et al. 2006). The objective of this study was to obtain a better understanding of the above risk factors predisposing cows to production diseases. Certain metabolic indicators may be suitable for predicting the risk of RP and serve as a basis for the development of preventive and monitoring strategies for practice. For this reason, the correlations between RP and indicators characterising the energy balance and acid-base status of dairy cows as well as certain environmental and animal-dependent predisposing factors were studied. In addition, the effects of RP on the development of puerperal metritis as well as on metabolic status, reproductive performance, and milk production were analysed. Materials and Methods Characteristics of the herd studied The farm serving as the study site had a dairy herd comprising 730 Holstein-Friesian cows. Milk production of the 305-day lactation was 8,000 kg, with 3.6–3.7% butterfat and 3.1–3.2% milk protein content. In the previous year, the calving interval was 433 days, the calving to conception interval was 168 days, the number of services per conception was 3.3, the interval from calving to first service was 97 days, and the pregnancy rate to first service was 43%. The rate of losses due to mortality, and emergency slaughter was 9.7%, and the total sorting out rate was 31.4%. The farm used loose housing system and the cows were kept in groups, in houses with deep litter and having outdoor pens. Groups were formed by considering the serial number of lactations, the milk production level, and the lactation and pregnancy status of the cows. The calving barn was of loose system, with the cows kept in small groups. In the two weeks before calving, in the calving barn and in the first month of lactation the primiparous and multiparous cows were kept together, while from the peak of lactation they were kept in separate groups. The daily ration fed to cows was formulated with the help of a ration-optimising programme (AminoCow 3.0), by taking into consideration the composition of forages determined by feed analysis, the lactation and pregnancy status, the milk production, and the body condition score. The calculated nutrient content of the total mixed ration (TMR), distributed to the cows twice a day met the requirements (NRC, 2001). 164