76 Acta argiculturae Slovenica, Supplement 5, 76–79, Ljubljana 2016 24th Int. Symp. “Animal Science Days”, Ptuj, Slovenia, Sept. 21st−23rd, 2016. COBISS: 1.08 Agris category code: L73 FAT-TO-PROTEIN RATIO: EVALUATION OF METABOLIC DISORDERS AND MILK YIELD Michal VLČEK 1, Juraj CANDRÁK 2, Radovan KASARDA 3 Fat-to-protein ratio: evaluation of metabolic disorders and milk yield 1 Dep. of Animal Genetic and Breeding Biology, Slovak Univ. of Agriculture in Nitra, Tr. A. Hlinku 2, 949 76 Nitra, Slovakia, e-mail: xvlcekm@uniag.sk 2 Same address as 1, e-mail: juraj.candrak@uniag.sk 3 Same address as 1, e-mail: radovan.kasarda@uniag.sk ABSTRACT The aim of the paper was to evaluate the occurrence of metabolic disorder based on the fat-to-protein ratio and the effect of fat-to-protein ratio on the milk yield. In total, 680 records of test day (from 3 to 150 days) of 188 cows originating from 4 farms in west part of Slovakia between years 2013 and 2016 were collected to perform the study. The statistical analyses were carried out by SAS software. The highest prevalence of ketosis risk (19.08 %) was found in first month after calving, while the frequency of acidosis risk increased gradually from the start (10.53 %) to the middle of lactation (26.60 %). In the analysed group of cows the average milk yield at level 35.83 kg day−1 was found. The selected effect of herd, parity, year, calving season, days in milk and fat-to-protein ratio explained 55.67 % of the milk yield vari- ability. Due to the effect of fat-to-protein ratio the decrease of milk yield 1.2 kg day−1 was observed. Based on the results the fat-to-protein ration can be regarded as good estimator of metabolic disorders occurrence. Key words: cattle, dairy cows, test day, fat-to-protein ratio, milk yield, metabolic disorders balance around calving. A certain degree of negative en- ergy balance is expected in cows in late gestation and ear- ly lactation (Duffield et al., 2009). Berge and Vertenten (2014) observed high prevalence of ketosis in fresh cows. Currently, the lactational prevalence of SCK in Europe is estimated to be at 25 % (Raboisson et al., 2014). The aim of this study was to analyse the occurrence of metabolic disorders using the fat-to protein ratio and estimate the impact of fat-to-protein ratio on the milk yield in dairy cows. 2 MATHERIALS AND METHODS In total 188 dairy cows from 4 farms in west part of Slovakia were included into the study. The records of test day of milk yield of cows between 3 and 150 days in milk (DIM) were collected in period 2013 to 2016. The risk of metabolic disorders prevalence based on the fat-to- 1 INTRODUCTION The problems of negative energy balance (NEB), disproportional energy metabolism (fatty liver, ketosis, subacute, acute ruminal acidosis), disturbed mineral uti- lization and perturbed immune function are common in transition cows (Esposito et al., 2014). Duffield et al. (2009) reported that poor adaptive response to the onset of lactation can lead to the problems of clinical diseases and impaired milk production. Subacute ruminal acidosis (SARA) is characterized by depressed rumen pH for several hours per day due to accumulation of volatile fatty acids and insufficient ru- men buffering (Plaizier et al., 2009). SARA is a prevalent metabolic disorder that has been found in high-produc- ing dairy herds, mainly due to the feeding excessively fer- mentable diets (Gao and Oba, 2014). Subclinical ketosis (SCK) is a major dairy cow meta- bolic disorder caused by strong dietary negative energy Acta agriculturae Slovenica, Supplement 5 – 2016 77 FAT-TO-PROTEIN RATIO: EVALUATION OF METABOLIC DISORDERS AND MILK YIELD level 18.24 %. Compared to our results Buttcheriet et al. (2012) reported for dairy cows lower proportion of meta- bolic disorders at level 9.7 %. Figure 1 shows the prevalence of acidosis and keto- sis over 5 months of lactation. The highest observed prev- alence of ketosis risk (19.08 %) in first month after calv- ing is in accordance with study of Gantner (2015), who reported that the highest ketosis risk was determined in early lactation (till 60th day), while the lowest frequency was after the 180th day. In addition, Berge and Vertenten (2014) found that the average herd prevalence of ketosis in fresh cows 1 to 3 week post-calving was 41 %, whereas only 1.6 % of the cows were diagnosed with clinical keto- sis within 35 days postpartum. The frequency of acidosis risk within analysed cows increased gradually from the start to the middle of lacta- tion (Fig. 1). Gao and Oba (2014) reported that the risk of SARA is greater for early- and mid-lactation cows compared with late lactation cows mainly due to feeding highly fermentable diets and greater feed intake. Our results indicated that the higher prevalence of ketosis can be associated with quick increase of milk production in early lactation. The intake of dry matter and energy is lower than cows´ requirements what result to negative energy balance (NEB) and production of ke- tones (acetoacetic acid, acetone and β-hydroxybutyrate) in blood (Esposito et al., 2014). The lower levels of keto- sis were found mainly in herds fed with total mixed ratio (TMR) or feeding forage and concentrate in comparison to the herd fed with partial mixed ratio (PMR) (Berge and Vertenten, 2014). Oetzel (2007) reported that the oc- currence of ketosis is uncommon in TMR-fed herds be- protein ratio (F/P ratio) was indicated according to the methodology of Gantner (2015) and the F/P ratio was divided into the groups: K when F/P ≥ 1.5 meaning ketosis risk, N when F/P 1.0 – 1.5 meaning normal conditions, A when F/P < 1.0 meaning acidosis risk. The effect of F/P ratio on milk yield was analysed with using general linear model (GLM) procedure in- corporated in SAS software (SAS Institute, 2009). In the GLM model were included fixed effects of year, calving season, parity, herd and the random effects of F/P ratio and days in milk. For statistical analyses calving season was grouped as spring (March to May), summer (June to August), autumn (September to November) or winter (December to February). The parity of cows was divid- ed into groups of first parity, second parity and third or higher parity. 3 RESULTS AND DISCUSSION Overall, 680 records of test day (3 to 150 days in milk) of 188 dairy cows from 4 farms were analysed. All 4 herds were fed by total mixed ratio (TMR). Evaluated cows were divided into the groups according to first parity (n = 42), second parity (n = 59) and third or higher par- ity (n = 88), and the same animal could be also observed at different parity. The average milk production of cows across all herds was 35.83 ± 11.17 kg day−1 with average 68.18 ± 40.38 days in milk and average parity 2.23 ± 0.8. Within the analysed group of cows higher proportion for acidosis risk was found. The frequency of ketosis risk was 12.21 %, while the acidosis risk reached frequency at 0 5 10 15 20 25 30 Month 1 (n=152) Month 2 (n=172) Month 3 (n=144) Month 4 (n=118) Month 5 (n=94) Acidosis (%) Ketosis (%) Figure 1: The prevalence of acidosis and ketosis over the 5 months of lactation (150 days in milk); n – number of observations Acta agriculturae Slovenica, Supplement 5 – 201678 M. VLČEK et al. 4 CONCLUSION Within analysed group of cows higher proportion for acidosis risk was found. The frequency of ketosis risk was 12.21 %, while the acidosis risk reached propor- tion at level 18.24 %. The highest prevalence of ketosis risk was observed in first month after calving, while the frequency of acidosis risk increased from the start to the middle of lactation. In addition, the results indicated that the higher prevalence of ketosis has been associated with quick increase of milk production in early lactation. Ex- cept F/P ratio each of selected fixed effects included in GLM model significantly affected the milk production. But the results indicated that the F/P ratio have negative impact of milk yield and reflect the risk of subclincal ke- tosis or subacute ruminal acidosis. Therefore, the evalua- tion of F/P ratio can be regarded as the non-invasive and cheap method of metabolic disorders prediction to elimi- nate its negative effect on milk yield. 5 ACKNOWLEDGMENT This study was supported by the Slovak Research and Development Agency under the Contract No. APVV-14-0054. The data were provided by the Breeding Services of Slovakia, s. e. 6 REFERENCES Berge A.C., Vertenten G. (2014). 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However, the results indicated that due to the effect of F/P ratio the milk production decreased by 1.2 kg day−1. The effect of F/P ratio has been reported for dairy cattle in several studies (Toni et al., 2011, Buttchereit et al., 2012, Zink et al., 2014). Buttcheriet et al. (2012) re- ported that fat-to-protein ratio (F/P ratio) and body con- dition score are potential variables to describe how well cows can adapt to the challenge of early lactation. The increase of F/P ratio in the early lactation was also sig- nificantly associated with increase of risk of being culled from the herd (Toni et al., 2011). Moreover, the F/P ratio is a valuable indicator of negative energy balance in post- partum cows and might be helpful in selecting concern- ing metabolic or other disorders (Zink et al., 2014). Parameter Estimate Standard Error p-value| Intercept 38.312 5.126 < 0.0001 Herd 1 −8.957 1.614 < 0.0001 Herd 2 −4.702 1.451 0.0013 Herd 3 2.320 1.505 0.1239 Herd 4 Referent . . 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