August Body Condition Score Description and Use of a New Trait

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1 Body Condition Score Description and Use of a New Trait August General 1.1 Trait definition Body Condition Score (BCS) is based on a visual assessment of the pelvic region only. BCS describes a subjective method of assessing the amount of metabolisable energy stored in fat and muscle (body reserves) of live animals, which is available to sustain growth, maintenance, milk production (and fetal development) (Banos et al., 2007; Lassen et al., 2003). It is independent of the animal s frame size and body weight (Koenen and Groen, 1998, Coffey et al., 2003). There is a good relationship between BCS and total body fat content such that BCS is a useful management aid for dairy farmers in monitoring the nutritional and metabolic status of cows (Coffey et al., 2003). Similar traits have been part of the linear assessment scheme for decades. They are called depending on country where used dairy form, dairy character or angularity. These traits denote a visual assessment of the rib structure, often seen as an overall tendency of a cow to be angular and thin. Body weight on the other hand is affected by animal size (skeletal development), degree of fatness, and gut fill, all of which are dependent of the stage of pregnancy, stage of lactation, and age-dependent growth (Berry et al., 2002). Body Condition Score is an Interbull trait. The trait is defined differently according to the countries submitting data to the common run. Belgium, Switzerland, Germany, Denmark, Finland, Sweden (NAV) and the Great Britain send data of a trait called Body Condition Score, while Italy and the USA send in data for Angularity. The Netherlands call the trait Relative fatness or body composition of the cow, and New Zealand has a Visual estimate of condition. 1.2 Scale BCS is scored on different scales in different countries. In case field-inspectors collect the trait in connection with the linear type assessment, the same scale is used both for BCS and type traits. In The Netherlands, Denmark and the UK, a scale from 1 9 is used, while a scale from 1 to 5 in increments of 0.1 or 1 50 was applied in the US. When BCS was scored with regard to special research projects, other scales might have been applied, e.g. a scale from 1 to 10 (in Ireland and NZ), or from 1 to 5 in increments of 0.25 (Ireland and Italy). The score of 1 denotes a thin (emaciated) cow and the highest score a fat animal. 2 Genetics 2.1 Frequency of scoring BCS was introduced as a new trait about a decade ago, and initial research concentrated on establishing the genetic behaviour of the trait. Table 1 shows the heritability estimates for BCS obtained for Holstein in different countries. The estimates vary between 0.07 and 0.38, those obtained from data recorded during routine on farm linear type appraisal in Europe lie above

2 Table 1. Heritability estimates for BCS, Holstein h 2 Author Comments BCS 0.37 Gulinski et al., 2005, Poland BCS Dechow et al., 2004a, USA diff. stages of lactation BCS 0.21; 0.22 Dechow et al., 2004a/b, USA score 1 50 BCS 0.24 Kadarmideen and Wegmann, 2003, Switzerland BCS 0.25 Lassen et al., 2003, Denmark 1 st parity BCS < Lassen et al., 2003, Denmark 1 st parity BCS > Lassen et al., 2003, Denmark 1 st parity BCS Dechow et al., 2001, USA 1 st lact., 6 diff. lact. Stages BCS Dechow et al., 2001, USA 2 nd lact., 6 diff. lact. Stages BCS 0.19 Dechow et al., 2003, USA Collected by field-officers BCS Koenen et al., 2001, Netherlands different stages of lactation BCS Gallo et al., 2001, Italy different stages of lactation BCS Pryce et al., 2001, UK Week1, Week 10, avg BCS 0.38 Veerkamp et al., 2001, NL with linear type traits BCS Pryce et al., 2000, UK Based on Jones + Brotherstone, several stages of lactation Furthermore, the question arose whether the trait was the same throughout a lactation or a cow s productive life, i.e. whether the heritability at various points of time was the same and the genetic correlations between different parts of a cow s life cycle were close to one. The following tables present some of these genetic parameters for Holstein, either in first or second lactation and at differently defined points of time. Table 2. Heritabilities and genetic correlations for BCS between bimonthly lactation periods (Koenen et al., 2001). Holstein 1 to 2 mths 3 to 4 mths 5 to 6 mths 7 to 8 mths 9 to 10 mths 1 to 2 months to 4 months to 6 months to 8 months 1 Table 3. Heritabilities and genetic correlations for BCS between different days in milk in first and second lactation (Dechow et al., 2004a). Lact day

3 Table 4. Heritabilities and genetic parameters for BCS between different days in milk in first lactation (Gallo et al., 2001). DIM dry Table 5. Heritabilities and genetic correlations for BCS between different points of time during a cow s life cycle (Dechow et al., 2001). 1. lactation calving postpartum First service Pregn check Before dry Dry-off Calving Postpartum First service Pregn check Before dry Dry-off lactation calving postpartum First service Pregn check Before dry Dry-off Calving Postpartum First service Pregn check Before dry Dry-off 0.11 Generally, the genetic correlations were very high (close to one) between subsequent periods and dropped for periods longer apart (Dechow et al, 2004a; Gallo et al., 2001). BCS at calving (Dechow et al., 2001) showed relatively low correlations to the following lactation stages both in first and second lactation (r g ) and this was explained with the difficulty of scoring this trait at calving. The appearance of the hip and pin bones may be more prominent around parturition due to the loosening of the pelvic structure that occurs before calving. This change may lead to a tendency to under-evaluate BCS at parturition and thus produces low correlations with subsequent periods. Low relationships between scores collected directly at calving and later in lactation were corroborated by Banos et al. (2005) who worked with a trait called Body Energy Content which was based on body lipid and protein changes predicted from weekly changes in body condition score and live weight of each cow. Correlations between the Body Energy Content of the first week after calving with each of the following weeks until the end of lactation were low, mainly below 0.1. When correlating the score of the fifth week with that of later weeks, the correlation was substantially higher, dropping slowly from 1.0 to 0.6 over the lactation. Cows that are genetically superior milk producers tend to have 3

4 genetically lower BCS in late lactation (Berry et al., 2002) which might have an influence on the correlation between BCS early and late in lactation. 2.2 BCS change throughout a cow s production cycle Body condition score is a trait which is in continuous flow. It drops after calving when the cow mobilises body reserves in order to account for the requirements of a high milk yield and moves towards the peak of her lactation. After the peak, BCS starts slowly to pick up again and reaches a high at dry-off (Dechow et al., 2001; Pryce et al., 2001; Coffey et al., 2003; Dechow et al., 2003; Dechow et al., 2004a;). Coffey et al. (2003) could show that sires differ in the way their daughters lose and regain body energy throughout lactation. Cows genetically inclined to produce higher levels of milk tend to have lower levels of BCS, lose more BCS in early lactation, and have consequently more severe negative energy balance in early lactation. Higher producing cows likely partition more nutrients toward production and less toward replenishing body condition during mid- to late lactation, and then recover body condition at a more rapid rate in late lactation and the dry period (Dechow et al., 2004a). Over the lifetime of the cow, the replenishment of body lipid is cyclical and failure to replenish sufficient body lipid in one lactation may result in carry-over effects in subsequent lactations. (Coffey et al., 2003). Cows losing most BCS in early lactation tend to gain most BCS in late lactation (Berry et al., 2002). While most cows show this cycle, some, especially high genetic merit cows, were also found to be constantly in negative energy balance. These animals put additional energy in milk production and lose weight throughout lactation, no nadir can be determined (McCarthy et al., 2007). Likewise, Coffey et al. (2003) found a few sires in their data, whose daughters continued to lose body energy through to the end of lactation. 2.3 BCS change The question arises whether the absolute level of BCS is crucial or whether the loss and later on rise of body condition during lactation has a significant influence on other traits, like milk yield or fertility, health etc. BCS loss or BCS change describe the change between two scores, often between one assessment short after calving and then one weeks later. The heritabilities for BCS change were low (see Table 6), between 1 and 9 %. After some investigation, all authors concluded that BCS change was a less useful trait to work with then BCS. Instead, Pryce et al. (2001) suggested to use a body condition score collected early in lactation. In a study by Dechow et al. (2004a), the genetic correlation between BCS at different days in milk, lactation, and ages were high and change in BCS was only lowly heritable. Therefore, the time of scoring was of minor importance. Otherwise, evaluations from random regression models for Days in Milk when the relationship was strongest, might be of value. Table 6. Heritability estimates for BCS change, Holstein h 2 Author Comments BCS change 0.09 Pryce et al., 2001 Change between week 1 and 10 BCS change Dechow et al., 2004a, USA BCS differences between days 0 and 70, 305 and 70 BCS loss Dechow et al., 2002, USA BCS calving BCS postpartum The magnitude of the loss in body condition depends on the level of the score at the start of lactation. As mentioned above, cows with a lower BCS at calving tend to lose more BCS in early lactation 4

5 (Coffey at al., 2003). Or expressed the other way round, cows that were genetically inclined to have relatively high postpartum BCS tended to lose less BCS in the first weeks after calving (Dechow et al., 2002). 2.4 Scoring together with linear type traits When not collected for research purposes, BCS is usually recorded together with linear type traits on a regular basis by trained field-officers. In this case, BCS is treated like linear type trait, i.e. raw data are standardised to the same standard deviation of all field-officers (Koenen et al., 2001; Coffey et al., 2003) and often, an effect for age and stage of lactation or even day of lactation (Days in Milk) is put into the model. As mentioned above, BCS is in constant flow and highly influenced by the state of lactation. The question arises whether there is an optimal point of time for collecting BCS or whether data should be treated in a certain way in order to account for this aspect. Coffey et al. suggested to apply random regression techniques providing a time-oriented dimension to genetic evaluations and they concluded from their study that single observations of BCS collected routinely in national type appraisal schemes could be used in genetic analyses. Dechow et al. (2003) investigated whether it was feasible to collect data on BCS during linear type appraisal also in the US. As BCS changed more than other traits during lactation, fixed effects for age and stage of lactation were not included, instead Days in Milk were included as a polynomial regression coefficient of order 1 to 5. They concluded that collecting BCS data in connection with linear type traits gave practical data and that BCS was heritable and had genetic variation for use in national evaluation. 2.5 Influence of Breeds/Strains McCarthy et al, 2007 compared three different strains of Holstein cows, a New Zealand strain, a high yielding strain, and a strain with high durability, under different feeding strategies. The New Zealand strain contained lighter and more efficient cows with less change in BCS, a lower peak yield and a higher persistency. The other two strains had a higher BCS at calving and subsequently a higher BCS loss thereafter. The high genetic merit cow put additional concentrate in milk, not in body weight, they lost BCS throughout the lactation (no particular nadir could be found), had a high peak in yield, but a lower persistency, and inferior reproductive performance. The NZ strain gained weight in late lactation, whereas the high production cows lost weight throughout the whole lactation. The data revealed that the higher the BCS loss, the lower the reproductive performance. 2.6 Alternative traits (dairy form or dairy character) and their heritability As mentioned above, angularity, dairy form or dairy character (term depending on country where used) are used as alternative traits to BCS. Although, strictly seen, the two traits denote different features BCS the coverage of the pelvis bones with fat and dairy form the openness of the rib cage, they are occasionally used as alternatives. Dairy form has been part of the linear assessment scheme for decades and the question arises whether BCS gives some additional information dairy form does not, which justifies the collection of BCS in addition to dairy form on national level. The genetic correlation between BCS and dairy form was found to be (Lassen et al., 2003), (Kadarmideen and Wegmann, 2003), (Dechow et al., 2003), (Dechow et al., 2004b), 0.73 (Dechow et al., 2004c), to (Veerkamp and Brotherstone, 1997) and with angularity (Pryce et al., 2000), i.e. more angular cows with an open rib cage are genetically correlated with thin cows. Despite their high correlation, BCS and dairy form are not entirely the same trait, and according to Dechow et al., (2003) dairy form evaluates more than level of body condition. 5

6 Another trait not part of the linear assessment scheme, but related to frame and dairy form, is heart girth. Gallo et al. (2001) collected data on heart girth, measured in cm. The genetic correlation between heart girth and BCS was Correlations over to other traits 3.1 Milk yield BCS at various stages in lactation is negatively correlated with milk and also fat and protein yield, i.e. the thinner the cows, the higher the (milk) yield (see Dechow et al., 2001; Berry et al., 2002). The correlations were strongest for milk yield and less pronounced for protein. BCS at calving had the lowest correlation, while that around pregnancy check or 120 days in lactation showed the highest correlation. Similar results were found in another study, where no distinction between different stages of lactation was made. An increasing yield was genetically correlated with a decreasing condition score, the relationship was for fat yield, and for protein yield (Gallo et al., 2001). BCS at calving did not have an influence of milk yield later in lactation, which was also shown by Roche et al. (2007). Table 7. Genetic correlation between BCS and production at different points in first lactation (Dechow et al., 2001). Milk Fat Protein Calving Postpartum Pregnancy check Dry-off Table 8. Genetic correlation between BCS and milk yield at day 60, day 240 and cumulative milk yield at day 240 (Berry et al., 2002). Milk yield on day 60 Milk yield on day 240 Cum. milk day 240 BCS day BCS day BCS day BCS day BCS day Also dairy character and yield, here expressed as protein yield, showed the same pattern, i.e. a more angular cow had a higher protein yield than a less angular cow (Hansen et al., 2002). This tendency was considered genetically unfavourable, i.e. more angular or thinner cows are deemed less advantageous than fatter animals. 3.2 Reproduction Cows that are genetically superior producers tend to have genetically lower BCS, especially during the lactation. However, this genetic relationship is moderate and less than 1.0 (see Tables above). 6

7 Therefore, selection could improve production without necessarily causing a decline in genetic levels of BCS. BCS and Days to First Service were genetically negatively correlated, i.e. a thin cow was inseminated later in lactation, this was independent of adjustment for milk production. Services per conception declined as genetic levels of BCS during the lactation increased. BCS may be a useful tool in selection programs to maintain or improve genetic levels of reproductive performance (Dechow et al., 2001). Table 9. Genetic correlation between BCS and reproduction traits at different points in first lactation (Dechow et al., 2001). Days to first ~ milk adjusted Services per ~ milk adjusted service conception Calving Postpartum Pregnancy check Dry-off Table 10. Genetic correlation between BCS and milk or days open (Dechow et al., 2004c). Milk Days open ~ milk adjusted BCS Generally, an increase in yield is genetically associated with an increase in BCS loss by lowering postpartum BCS and a high BCS loss means a decrease in fertility (more days to first insemination). On the other hand, first insemination soon after calving entails a higher number of inseminations per conception. An increase in BCS at calving was genetically correlated with less BCS loss during early lactation. Breeding for cows being highly angular and having a high dairy form means that these cows become genetically thinner and that the amount of BCS lost during early lactation is likely to increase at a given level of BCS at calving. Continued selection, whether directly or indirectly, for thinner cows is likely to continue to increase negative energy balance and BCS loss in early lactation (Dechow et al., 2002). Table 11. Genetic correlation between BCS loss and production and fertility traits (Dechow et al., 2002) 1 st lactation 2 nd lactation Milk Fat Protein Days to first service Services per conception Health Generally, a low BCS (thin cow) or a high dairy form score were genetically associated with a high 7

8 disease incidence, i.e. displaced abomasums, metabolic and digestive diseases, mastitis, and all diseases. In other studies, a high dairy form and low body condition were furthermore unfavourably correlated with an increase in locomotive disorders. Similar results were obtained when using EBVs based on Danish data. The results indicated that at a given level of production, cows genetically inclined to be thin (high dairy form and low body condition) have higher levels of disease. Selection to increase yield and maintain current levels of body condition or dairy form should help limit unfavourable changes in levels of cow health while yields increase. In this study, dairy form tended to be more strongly correlated with disease incidence than BCS. It is not clear that genetic evaluations for body condition would provide valuable genetic information beyond current dairy form evaluations (Dechow et al., 2004b). Table 12. Genetic correlation between BCS or Dairy Form and several diseases (Dechow et al., 2004b; Lassen et al., 2003)) BCS Dairy Form Displaced abomasums -0.48* 0.54* Met. + digestive diseases -0.64* 0.65* Cystic ovaries Reproductive diseases Mastitis -0.93* 0.60* All diseases -0.79* 0.85* Diseases other than mastitis Based on Danish data, genetic correlations were calculated between disease data and BCS. Relationships were unfavourable, i.e and 0.41 for clinical mastitis and other diseases, respectively, and 0.13 and 0.39 for the same traits when adjusted for protein yield. (Hansen et al., 2002). These findings suggest that dairy character should be given a negative rather than a positive weight in the breeding goal in order to improve health. 4 Conclusion/ Recommendation: BCS is a reasonably new trait which can be collected by field inspectors when assessing the linear type traits. It shows a high genetic correlation with dairy form (or angularity), but the two traits describe different features of the cow s body and strictly speaking cannot be considered the same trait. Nevertheless, the addition of BCS evaluations does not increase reliability when dairy from observations are available and therefore, BCS would only be necessary if selection for BCS is shown to improve cow health or reproductive performance beyond what is possible with selection for dairy form. BCS change or BCS loss, i.e. the difference between a score at the beginning and at a given point of time later in lactation, is only lowly heritable and of little usefulness. Therefore there is no need to add it in any index calculations. This has also the advantage that only one score per lactation is sufficient and data could be solely collected in connection with the linear type traits if wished. BCS shows conflicting correlations with the other group of traits of interest: negative correlations with 8

9 milk production, but positive correlations with health and fertility traits. Until now, if used, BCS has been included in a milk index with a negative weight in order to select for thin and angular animals and further enhance milk production. As the information of milk yield itself is good and strong enough, correlated information would not be needed, therefore it is recommended not to include BCS as an indirect trait in a milk index. Instead, BCS would be a useful trait to include either in a fertility or in a disease index, but then with a positive weight, i.e. fatter animals are desirable. Such an index for fertility could be based on traits like calving interval, BCS, and linear type traits. When selecting for disease resistance, observations for diseases themselves should be available and included for being effective, only BCS or dairy character as an auxiliary trait do not provide enough correlated information. As mentioned above, BCS should receive a positive weight in such an index. The general conclusion is that BCS is in itself does not necessarily have any value and is not useful in connection with milk yield. It might help to improve fertility and disease resistance when included in an index with an appropriate weight and thus limit the unfavourable effect of selection for higher milk yield on fertility or disease resistance. Although BCS and dairy form can be used in similar contexts and yield similar results, there might still be some reasons to prefer the new trait BCS to the long used trait dairy form. Many cattle producers are more familiar with BCS than with dairy form, evaluation procedures for scoring body condition are well documented, and psychologically it might be more easily accepted to select for higher BCS than selecting against dairy form. 5 References Banos, G., Brotherstone, S., Coffey, M.P., Genetic profile of total body energy content of Holstein cows in the first three lactations. J. Dairy Sci. 88, Banos, G., Brotherstone, S., Coffey, M.P., Prenatal maternal effects on body condition score, female fertility, and milk yield of dairy cows. J. Dairy Sci. 90, Berry, D.P., Buckley, F., Dillon, P., Evans, R.D., Rath, M., Veerkamp, R.F., Genetic parameters for level and change of body condition score and body weight in dairy cows. J. Dairy Sci. 85, Coffey, M.P., Simm, G., Hill, W.G., Brotherstone, S., Genetic evaluations of dairy bulles for daughter energy balance profiles using linear type scores and body condition score analyzed using random regression. J. Dairy Sci.86, Dechow, C.D., Rogers, G.W., Clay, J.S., Heritabilities and correlations among body condition scores, production traits, and reproductive performance. J. Dairy Sci. 84:

10 Dechow, C.D., Rogers, G.W., Clay, J.S., Heritability and correlations among body condition score loss, body condition score, production and reproductive performance. J. Dairy Sci. 85: Dechow, C.D., Rogers, G.W., Klei, L., Lawlor, T.J., Heritabilities and correlations among body condition score, dairy form and selected linear type traits. J. Dairy Sci., Dechow, C.D., Rogers, G.W., Klei, L., Lawlor, T.J., 2004a. Heritability and correlations for body condition score and dairy form within and across lactation and age. J. Dairy Sci. 87: Dechow, C.D., Rogers, G.W., Sander-Nielsen, U., Klei, L., Lawlor, T.J., Clay, J.S., Freeman, A.E., Abdel-Azim, G., Kuck, A., Schnell, S., 2004b. Correlations among body condition scores from various sources, dairy form, and cow health from the United States and Denmark. J. Dairy Sci. 87: Dechow, C.D., Rogers, G.W., Klei, L., Lawlor, T.J., van Raden, P.M., 2004c. Body condition scores and dairy form evaluations as indicators of days open in US Holsteins. J. Dairy Sci. 87: Gallo, L., Carnier, P., Cassandro, M., Dal Zotto, R., Bittante, G., Test-day genetic analysis of condition score and heart girth in Holstein Friesian cows. J. Dairy Sci. 84, Gulinski, P., Mlynek, K., Litwincyuk. Z., Dobrogowska, E., Heritabilities of and genetic and phenotypic correlations between condition score and production and conformation traits in Black-and- White cows. Animal Science Papers and Reports 23, no 1, Hansen, M., Lund, M.S., Soerensen, M.K., Christensen, L.G., Genetic parameters of dairy character, protein yield, clinical mastitis, and other diseases in the Danish Holstein Cattle. J. Dairy Sci. 85: Kadarmideen, H.N., Wegmann, S., Genetic parameters for body condition score and its relationship with type and production traits in Swiss Holsteins. J. Dairy Sci. 86: Koenen, E.P.C., Groen, A.F., Genetic evaluation of body weight of lactation Holstein heifers using body measurements and conformation traits. J. Dairy Sci. 81: Koenen, E.P.C:, Veerkamp, R.F., Dobbelaar, P., De Jong, G., Genetic analysis of body condition score of lactating Dutch Holstein and red-and-white heifers. J. Dairy Sci. 84: Lassen, J., Hansen, M., Soerensen, M.K., Aamand, G.P., Christensen, L.G., Madsen, P., Genetic relationship between body condition score, dairy character, mastitis, and diseases other than mastitis in first-parity Danish Holstein cows. J. Dairy Sci. 86: McCarthy, S., Berry, D.P., Dillon, P., Rath, M., Horan, B., Influence of Holstein-Friesian strain and feed system on body weight and body condition score lactation profiles. J. Dairy Sci. 90,

11 Pryce, J.E., Coffey, M.P., Brotherstone, S., The genetic relationship between calving interval, body condition score and linear type and management traits in registered Holsteins. J. Dairy Sci. 83: Pryce, J.E., Coffey, M.P., Simm, G., The relationship between body condition score and reproductive performance. J. Dairy Sci. 84: Roche, J.R., Lee, J.M., Macdonald, K.A., Berry, D.P., Relationships among body condition score, body weight, and milk production variables in pasture-based dairy cows. J. Dairy Sci. 90, Veerkamp, R.F., Brotherstone, S., Genetic correlations between linear type traits, food intake, liveweight and condition score in Holstein-Friesian dairy cattle. Anim. Sci. 64, Veerkamp, R., Koenen, E.P.C., De Jong, G., Genetic correlations among body condition score, yield, and fertility in first-parity cows estimated by random regression models. J. Dairy Sci. 84, Dorothee Boelling August