Relationships of early performance traits to lifetime profitability in Holstein cows

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1 Relationships of early performance traits to lifetime profitability in Holstein cows K. K. Kulak 1, J. C. M. Dekkers 1, A. J. McAllister 2, and A. J. Lee 3 1 Centre for Genetic Improvement of Livestock, Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, Canada N1G 2W1; 2 Department of Animal Sciences, University of Kentucky, Lexington, KY, USA; 3 Centre for Food and Animal Research, Agriculture and Agri-Food Canada, Ottawa, Ontario, Canada K1A 0C6. Received 26 November 1965, accepted 20 August Kulak, K. K., Dekkers, J. C. M., McAllister, A. J. and Lee, A. J Relationships of early performance traits to lifetime profitability in Holstein cows. Can. J. Anim. Sci. 77: Relationships of first lactation traits to lifetime profitability were studied based on data of 1112 lifetime performance records of purebred Holstein cows from the National Cooperative Dairy Cattle Breeding Project, which was implemented by Agriculture Canada in Lifetime profit was defined based on milk production, body weight, reproductive performance, herdlife, and prices for feed energy, milk, calves, salvage value, and fixed costs. First lactation traits with significant relationships to lifetime profitability were identified using the backward elimination procedure for least squares. Relative weights of each prediction trait were expressed as standard partial regression coefficients. Milk revenue in first lactation was the most important trait, followed by 3 min yield, and udder height. First lactation survival was found to be significant. Increasing age at first calving, number of days from first breeding to conception in first lactation, and teat diameter had significant negative effects on profit. Health traits in first lactation were not significant. The significant traits explained 35% of total variation in lifetime profitability. Key words: Dairy cow, lifetime profitability, early indicator traits Kulak, K. K., Dekkers, J. C. M., McAllister, A. J. et Lee, A. J Rapport entre les caractères modulant les performances en début de production et la rentabilité à vie des vaches Holstein. Can. J. Anim. Sci. 77: Nous avons étudié les rapports des caractères de performance en première lactation avec la rentabilité à vie à partir des données consignées sur relevés de production à vie de vaches Holstein de sang inscrites au Projet coopératif canadien d amélioration des bovins laitiers mis en place en 1972 par le ministère de l Agriculture du Canada. La rentabilité à vie prenait en compte la production laitière, le poids corporel, les performances de reproduction, la vie du troupeau, les veaux, la valeur de récupération et les charges fixes. Les caractères de performance en 1 e lactation donnant des rapports significatifs avec la rentabilité à vie étaient dégagés par élimination régressive. Les pondérations de chaque caractère de prédiction étaient exprimées comme coefficients de régression partielle standards. Le produit du lait en 1 e lactation était le caractère le plus important, suivi du rendement après 3 mn de traite et de la hauteur d attache des tétines. Le taux de survie à la 1 e lactation s avérait significatif. Le report de l âge au premier vêlage, l intervalle première mise à la reproduction-conception en 1 e lactation et le diamètre des tétines avaient des effets négatifs significatifs sur la rentabilité. Les caractères d ordre sanitaire en 1 e lactation n étaient pas significatifs. Les caractères significatifs justifiaient 35 % de la variation totale de la rentabilité à vie. Profitability of individual cows can be regarded as the breeding objective in dairy cattle. This trait is a function of production, length of productive life, reproductive performance, as well as health and management aspects. Kulak et al. (1997) studied lifetime profitability measures of dairy cows and identified discounted lifetime profit adjusted for opportunity costs of postponed replacement (DLPOC) as the best measure of profit. Relationships between first lactation milk yield and subsequent performance, and length of herd life were examined by White and Nichols (1965). A small but real (0.22 correlation existed between level of first lactation production and length of herd life. Gilmore (1977) found that milk and fat yields in first lactation, and dairy character, were significant predictors of annualized lifetime profit and annualized milk income minus feed and health costs, while body capacity and final score had a smaller effect on the latter. The coefficients of determination of the models that included the above independent Mots clés: Vache laitière, rentabilité à vie, indicateur précoce 617 variables were 0.27 and 0.40 for annualized lifetime profit and annualized milk income minus feed and health costs. Beaudry et al. (1988) found that first lactation performance was more highly correlated with per day profit than with total lifetime profit. Norman et al. (1981) found that first lactation yield had a correlation of 0.56 with income per day of productive life. De Haan et al. (1992) found correlations between DLPOC and first lactation product value of 0.55 and 0.59 for grade and registered cows, respectively. Everett et al. (1976) showed first lactation milk yield to have correlations of 0.18, 0.25, 0.36, 0.32, and 0.31 with stayabilities to 36, 48, 60, 72, and 84 mo, respectively, suggesting that bulls with higher evaluations for milk yield have daughters that last longer. It must be noted that these relationships are affected by the voluntary culling rather than health per se. Abbreviations: DLPOC, discounted lifetime profit adjusted for opportunity costs

2 618 CANADIAN JOURNAL OF ANIMAL SCIENCE Norman and Van Vleck (1972) examined relationships of first lactation type ratings under the Cornell type Appraisal System and first lactation production with lifetime producing ability. Of the first lactation variables, milk yield had the highest correlation with lifetime milk (0.34) and fat yield had the highest correlation with number of lactations (0.21). They reported that 35 type traits in first lactation were as useful as first lactation production variables in predicting number of lactations. Fore-udder attachment, udder depth, and teat placement were shown to be most useful in predicting lifetime income by Cassell et al. (1990). Norman et al. (1981) found that cows with higher scores for final score, suspensory ligament, and mammary system were more profitable than cows with lower scores. Gilmore (1977) found dairy character the only significant type trait to predict annualized lifetime profit. Although mastitis is the major health problem in first lactation heifers, losses are somewhat less in heifers than in older cows. Balaine et al. (1981) found that number of mastitis treatments during the herd life had a correlation with profit per day of High-yielding cows can be a source of increased risk of disorders. The best evidence currently available suggests that the cow which produced more milk than her herdmates is at increased risk of milk fever. Other diseases, such as metritis, cystic ovary, ketosis and clinical mastitis may also be related to high production (Erb 1987). Dairy farmers are reluctant to accept first lactation production as an adequate and sole indicator of a cow s lifetime profitability. However, lifetime production traits can only be measured on cows at the end of their productive lives. Therefore, examination of relationships of various first lactation traits with lifetime profitability of individual cows could speed up identification of the most profitable cows and make selection and culling for lifetime profitability more efficient. The literature identifies milk production in first lactation as the most important biological trait affecting profitability of the dairy cow. Also, reproduction and health-related problems were recognised as having an impact on profit. In addition, some type traits were identified to be significantly related to the profitability of the dairy cow. However, there is no consistency in identifying traits other than production. It is necessary to examine relationships further in order to gain a better understanding of relationships between traits that can be measured early in a cow s life and her lifetime profitability. The above considerations led to the objective of this study, which was to determine relationships of lifetime profitability measures to performance traits measured in early life, up to the end of first lactation. MATERIALS AND METHODS Data for this study consisted of 1112 lifetime performance records of purebred Holstein cows from the National Cooperative Dairy Cattle Breeding Project, which was implemented by Agriculture Canada in The foundation herd for this project was the result of an earlier experiment, in which selection was for total solids yield during the first 180 days of the first two lactations (Hickman 1971). The Holstein cows on the project at Lennoxville, Lethbridge, and Ottawa were mated to Canadian and American progeny-tested Holstein bulls available through artificial insemination as well as to Holstein bulls from the Agriculture Canada research herd to produce the foundation of the Holstein line. The specific outside bulls used and their progeny test information, available at the time the bulls were selected in 1971, were reported by Lee et al. (1982). The purposes of breeding to bulls from outside the population were (1) to have a broad genetic base of the Holstein line, (2) to evaluate the contributions outside breeding could make to long-term performance in the Holstein line, and (3) to improve the milk and protein yield of the Holstein line. A detailed description of the overall project is in Animal Research Institute Technical Bulletin no. 1 (McAllister et al. 1978). The overlapping bull group design of Hickman and Freeman (1969) was used to avoid confounding groups of bulls with differences between years. In the Holstein line, half the matings each year were to bulls used the previous year and half to bulls used for the first time, which was designed to prevent development of inbreeding and strong relationships among animals. Three research stations, in Ottawa, Lethbridge, and Lennoxville, supplied data. Recorded traits represented growth, production, reproduction, nutrition, health, maintenance and management aspects of each cow from birth to disposal or the end of the project (September 1986). Animals were cared for according to the recommended code of practice of Agriculture Canada (1990). A management protocol specified feeding guidelines and management practices for the different age classes of heifers and for milking and dry cows for all stations to standardize husbandry. Facilities, forage type and quality, and climate differed among stations (Lee et al. 1982). Several edits were applied to the data to ensure that only cows with valid information were used (Kulak 1994). Table 1 outlines first lactation variables that were used in this study. The relationship of these traits to the lifetime profitability measures, as reported in an earlier study by Kulak et al. (1997), were investigated by backward regression analysis. For a detailed description of the profitability measure and its parameters, reference is made to (Kulak 1994). Revenue and cost items (with prices present in 1993) were computed for all cows which calved at least once. The revenue items considered were returns from milk, calf, and salvage value upon disposal. Cost items included costs for feed, reproduction, veterinary treatment, calf value for the animal whose profit is being calculated, and fixed costs. It was assumed that the ration contained sufficient protein and energy. The feeding program consisted of good-quality forage fed free choice at all times, a mineral mix was available free choice, and hay, grass-legume silage, or a roughage mixture and grain were fed according to requirements. Feed intake was therefore fully determined by the energy and protein requirements of the cow. Predicted net energy requirements were derived using National Research Council (NRC 1989) guidelines for maintenance, pregnancy and growth, along with estimates of 69.9, 35.6 and 25.1 MJ ME kg 1 of fat, protein and lactose production (Dommerholt and Wilmink 1986).

3 KULAK ET AL. EARLY PERFORMANCE TRAITS VS. LIFETIME PROFITABILITY IN HOLSTEIN COWS 619 Table 1. Description of prediction traits considered Trait Description HERD Research station (Lethbridge, Lennoxville, Ottawa) YEAR1FR Year of first freshening ( ) SEASON Season of first freshening (1=April Sept.; 0=Oct. March) FLS 1 for cows that did survive first lactation, 0 for cows that did not MLKREV1 Milk revenue in first lactation calculated using age-corrected yields YIELD3M Average three minute yield of a.m. and p.m. records (kg) YIELD%RQ Fraction of yield by rear quarters DIM1 Days in milk in first lactation (d) AFB Age at first breeding (d) AFC Age at first calving (d) DT1B1 Days from calving to first breeding (d) BRTC1 Days from first breeding to conception (d) DOPEN1 Days open in first lactation (d) DDRY1 Days in dry period (d) REARVET Number of veterinary treatments in the rearing period MAST1 Number of mastitis treatments in first lactation REPRO1 Number of reproductive treatments in first lactation OTHD1 Number of other health problems in first lactation LENGTHT z Average teat length of front and rear teats (were measured from the point of connection to the udder to the distal end in cm) DIAMT z Average teat diameter of front and rear teats (taken with outside-diameter callipers at the mid-length (cm)) UH 1 The distance from the floor to the average height of the point of attachment of all teats (cm) DISTT z Distance between the lateral alignment at the front and rear teats (cm) BW 1 body weight (kg) SHOOK z Distance between the extreme lateral protrusion of the shoulder and hook on both sides with the average (cm) WHOOK z Distance between the lateral extremities of the hooks (cm) RUMPL z Distance between the extreme lateral protrusion of the hooks and pins on both sides with the average (cm) CHESTW z Distance between the narrowest body section behind the shoulders (cm) CHESTD z Vertical distance from the floor of the chest behind the legs to the rear part of the withers (cm) WITHERH Distance from the floor to the highest part of the withers at 280 d (cm) HTDN Consumption of TDN between 26 and 34 wk of age (kg TDN) FEEDEF Ratio of milk energy (MJ) produced to TDN consumption in 8 16 wk of first lactation (MJ kg 1 TDN) z Recorded at 112 d of first lactation. Statistical Analysis The General Linear Models Procedure (SAS Institute, Inc. 1990) was used to quantify relationships of first lactation traits with lifetime profit. The following Model 1 was used: Profit jklmn = HERD jk YEAR1FR jl SEASON jm + FLS jklmn + b 1j MLKREV1 + b 2j YIELD3M + b 3j YIELD%RQ + b 4j AFB + b 5j AFC + b 6j DT1B1 + b 7j BRTC1 + b 8j DDRY1 + b 9j REARVET + b 10j MAST1 + b 11j REPRO1 + b 12j OTHD1 + b 13j LENGTHT + b 14j DIAMT + b 15j UH + b 16j DISTT + b 17j BW + b 18j SHOOK + b 19j WHOOK + b 20j RUMPL + b 21j CHESTW + b 22j CHESTD + b 23j WITHERH + b 24j HTDN + b 25j FEEDEF + e jklmn Where j is the measure of profitability (MMF = lifetime milk revenue minus lifetime feed costs, LP is the lifetime profit, DLP is the discounted lifetime profit, ADLP LTL is the annualized DLP per year of total life, ADLP LPL is the annualized DLP per year of productive life, DLPOC is the DLP adjusted for opportunity cost of postponed replacement, EF is the economic efficiency); k is the herd; l is the year within kth herd; m is the season within klth herd-year; n is the individual within klmth herd-year-season; Profit jklmn is the jth measure of profit of the nth individual in the mth season in the lth year in the kth herd b 1j b 25j is the linear regression coefficients for profit on trait under consideration. See Table 1 for an explanation of variables. The backward elimination procedure (Draper and Smith 1981) was used, which drops, in a stepwise manner, variables with nonsignificant partial regression coefficients. Standard partial regression coefficients were derived by multiplying regression coefficients by the ratio of the standard deviation for independent variable to the standard deviation for dependent variable. Two classes of models were considered: Class A with only linear effects and Class B with linear and quadratic effects. An additional model, referenced as Model 2, with variables available from Dairy Herd Improvement programs, was tested also: Profit jklmn = HERD jk YEAR1FR jl SEASON jm + FLS jklmn + b 1j MLKREV1 + b 2j DIM1 + b 3j AFC + b 4j DOPEN1 + b 5j DDRY1 + e jklmn After identifying significant traits for the above model, the effects of inclusion of additional information was tested. First, the addition of type traits (body measurements) was examined (Model 3). Body measurements considered were: SHOOK, WHOOK, RUMPL, CHESTW, CHESTD, WITH- ERH. Second, the addition of feed efficiency to Model 2, was investigated (Model 4). In addition, a model with only herd-year-season interaction (only 3-way interaction), and FLS (Model 5) was tested to examine the contribution of FLS to the explanation of variation in profit measures. Coefficients of determination were computed for each model based on:

4 620 CANADIAN JOURNAL OF ANIMAL SCIENCE Table 2. Statistics of performance traits Variable N Mean Std. dev. 1 MLKREV YIELD3M 823 z YIELD%RQ 823 z DIM AFB AFC DT1B1 888 z BRTC1 888 z DOPEN1 888 z DDRY1 888 z REARVET MAST REPRO OTHD LENGTHT DIAMT UH DISTT BW SHOOK WHOOK RUMPL CHESTW CHESTD WITHERH 1061 z HTDN 930 z FEEDEF 930 z z Records were fewer for some traits. R 2 = (SS M SS HYS )/(SS T SS HYS ) where SS M is the sums of squares due to model; SS HYS is the sums of squares due to herd, year, season interaction; SS T is the total sums of squares A contrast for FLS was needed to quantify the difference between cows that survived first lactation versus those that did not. The SAS contrast for FLS gave the difference between FLS = 0 and FLS = 1 with all other effects set to zero. Because some traits (DT1B1, BRTC1, DOPEN1, and DDRY1) were defined to be zero for FLS = 0, but are, on average, greater than zero for FLS = 1, this difference was considered when computing expected difference between cows culled in first lactation and other cows, everything else being equal. RESULTS Relationships of Early Performance Traits with DLPOC Means and standard deviations of traits measured early in life and in first lactation are in Table 2. Contributions to profit and a direct comparison of traits for Models 1 A and 1 B are shown in Tables 3 and 4 as partial and standard partial regression coefficients. Milk revenue in first lactation was by far the greatest indicator of profit (based on standard partial regression coefficients). Three minute milk yield was the second variable of importance in Model 1 A, and length of the dry period was next in Model 1 B. Model 1 A explained 35% of variation in profit. Model 1 B, with quadratic effects, did not increase explanation of variability significantly (R 2 = 0.37). Table 3. Significant (P < 0.10) partial (PRC) and standard partial regression coefficients (SPRC) of DLPOC on early indicator traits using Model 1 A (obs = 684), R-square = 0.35 Trait PRC P > T Std. error SPRC Std. error FLS contrast AFC (days) BRTC1 (days) DDRY1 (days) HTDN (TDN) MLKREV1 ($) DIAMT (cm) UH (cm) SHOOK (cm) RUMPL (cm) YIELD3M (kg) YIELD%RQ Table 4. Significant (P < 0.10) partial (PRC) and standard partial regression coefficients (SPRC) of DLPOC on prediction traits using Model 1 B (obs=684), R-square = 0.37 Trait PRC P > T Std. error SPRC Std. error FLS contrast Linear DDRY BW (kg) FEEDEF MLKREV ($) DIAMT (cm) UH (cm) SHOOK RUMPL YIELD3M YIELD%RQ Quadratic FEEDEF SHOOK RUMPL Tables 3 and 4 show how much cows that did survive first lactation outperformed cows that did not. The difference was $588 for Model 1 A and $593 for Model 1 B ( and in standard deviations of DLPOC). The basis for using actual dollar values was that it is better understood by producers (and considering low inflation rate in Canada dollar values can still be relevant, despite using prices present in 1993); however, these effects can be express as relative differences. Figure 1 illustrates the significant quadratic effects for SHOOK and indicates that, as length from shoulder to hook increased profit increased. The polynomial regression of DLPOC on RUMPL is illustrated in Figure 1. The initial increase in rump length caused a decrease in profit, followed by a plateau and then a slight increase in profit. The extremes of the graph should be interpreted with care, since they are based on limited observations. There does not appear to be a strong relationship between rump length and DLPOC. Results of Model 2, which included variables recorded by the DHI program, are in Table 5. Out of four variables tested (in addition to herd, year, season, and FLS) three were significant. Days open (DOPEN1) was not significant. Out of the five type traits that were tested for addition to Model 2 (excluding DOPEN1, which was found to be not

5 KULAK ET AL. EARLY PERFORMANCE TRAITS VS. LIFETIME PROFITABILITY IN HOLSTEIN COWS 621 Table 5. Significant (P < 0.10) partial and standard partial regression coefficients of DLPOC on prediction traits for Model 2 (obs=1112), R-square = 0.35 Standard Partial partial regression Std. error regression Std. Trait coefficients P > T estimate coefficients error FLS contrast MLKREV1 ($) AFC (d) DDRY1 (d) Fig. 1. Regression of discounted lifetime profit adjusted for opportunity costs of postponed replacement (DLPOC) on distance between shoulder and hook ( ) and rump length (+) using Model 1 B. significant), only SHOOK was significant (Table 6). Variation explained by the addition of type traits was minimal; the R-square was 0.35 for both models. Feed efficiency also did not add to the R-square of final Model 2 (Model 4 in Table 7). This could be caused by the fact that cows were fed according to yield, similarly as DLPOC was computed based on NRC requirements. Table 7 also shows results of analyzing a model (Model 5) with only herd-yearseason and FLS. It was found that cows that did not survive first lactation generated $982 less in lifetime profit than cows that did survive first lactation. Relationships of Early Performance Traits with Other Profit Measures Table 8 displays early performance traits that were found to be significant and their standard partial regression coefficients for different profitability measures using Model 1 A. For all measures, milk revenue (MLKREV1), 3 min yield (YIELD3M), age at first calving (AFC), days from first breeding to conception (BRTC1), average teat diameter (DIAMT), and udder height (UH) were significant. Percent of yield by rear quarters (YIELD%RQ) was significant for Table 6. Significant (P < 0.10) partial and standard partial regression coefficients of DLPOC on prediction traits for Model 3 (obs=1061), R-square = 0.35 Standard Partial partial regression Std. error regression Std. Trait coefficients P > T estimate coefficients error FLS contrast MLKREV1 ($) AFC (d) DDRY1 (d) SHOOK (cm) all measures except ADLP LPL. Consumption of TDN during the 26th 34th week of life (HTDN) and distance from shoulder to hook (SHOOK) were significant for all profit measures except for DLP. Rump length (RUMPL) was significant for ADLP LTL and DLPOC. Dry period (DDRY1) was significant only for DLPOC. Table 8 also exhibits contrasts between cows that survived first lactation versus cows that did not. Cows that did survive first lactation had higher profits of $1679 for DLP and of $376 for ADLP LTL. Efficiency was increased by Table 9 shows correlations of prediction traits with different profitability measures. Milk revenue in first lactation, 3 min yield, and feed efficiency had the highest correlations. The pattern of phenotypic correlations between prediction traits and profit measures indicated that, in most cases, largest correlations were with ADLP LPL, then with EF, followed by ADLP LTL, DLP, and lowest correlations were with DLPOC. Coefficients of determination for herd, year, and season interaction are presented as well (Table 8). DLPOC had the lowest herd differences (R 2 = 0.09). In all other profitability measures, herd effects accounted for approximately twice as much variation in profit as in DLPOC. This means that DLPOC is less affected by herd differences than any other profitability measure. DISCUSSION In the analyses, errors were assumed identically and independently distributed random variables. Genetic relationships among animals were ignored. This is not expected to bias estimates of fixed effects (Draper and Smith 1981), but could have biased levels of significance. Given the limited heritability of the traits involved (Strandberg 1991) and the

6 622 CANADIAN JOURNAL OF ANIMAL SCIENCE Table 7. Significant (P < 0.10) partial and standard partial regression coefficients of DLPOC on prediction traits for Model 4 (obs = 930, R- square = 0.35), and Model 5 (obs = 1112, R-square = 0.11) Model 4 Standard Partial partial regression Std. error regression Std. Trait coefficients P > T estimate coefficients error FLS contrast MLKREV1 ($) AFC (days) DDRY1 (days) Model 5 FLS Table 8. Summary of standard partial regression coefficients for different profitability measures using Model 1 A Profitability Measures Trait DLP ADLP LTL ADLP LPL EF DLPOC MLKREV ** 0.66 ** 0.63 ** 0.64 ** 0.66 ** YIELD3M 0.12 ** 0.09 ** 0.05 ** 0.07 * 0.11 * YIELD%RQ 0.11 ** 0.07 ** ** AFB 0.08 * AFC 0.12 ** 0.09 ** 0.07 ** 0.09 ** 0.07 BRTC ** 0.11 ** 0.11 ** 0.09 DDRY BW 0.06 HTDN * DIAMT 0.08 * 0.10 ** 0.08 ** 0.08 ** 0.09 * UH 0.07 * 0.09 ** 0.06 ** 0.08 ** 0.10 ** SHOOK 0.06 * * 0.09 * RUMPL * R R 2 HYS FLS contrast z z Contrast derived using partial regression coefficients utilizing Model 1 A. R 2 = coefficient of determination due to model. R 2 HYS = coefficient of determination due to only herd, year, and season.,*,**p 0.10, P 0.05, P 0.01, respectively. fact that genetic relationships among animals were not strong in this data set, the impact of ignoring genetic relationships is expected to be limited. This study used an edited data set from the same large population studies by Lin et al. (1987). Lin et al. (1987) reported phenotypic correlations of milk production traits with body and udder measurements in Holstein heifers. They found that milk production traits (308-d milk, front and rear half yields) were positively correlated with body measurements (heart girth, wither height, body length, and rump length). The results of the present study, which found height at withers and rump length, positively and significantly related to profit measures DLP, ADLP LTL, ADLP LPL, and EF agree with those of Lin et al. (1987). These traits were, however, not significantly related to DLPOC (Table 9). These positive correlations suggest that cows that have high milk production in first lactation were taller and larger than low producers. Lin et al. (1987) also found negative phenotypic correlations between udder height and yield traits, implying that high producing heifers tend to have Table 9. Correlations between prediction traits and profit measures Profitability Measures Trait DLPOC DLP ADLP LTL ADLP LPL EF MLKREV ** 0.55 ** 0.68 ** 0.74 ** 0.70 ** YIELD3M z 0.25 ** 0.43 ** 0.51 ** 0.55 ** 0.53 ** YIELD%RQ z NS NS 0.10 ** 0.15 ** 0.12 ** AFC 0.06 * NS 0.06 * * DT1B ** 0.41 ** 0.48 ** 0.50 ** 0.51 ** BRTC * 0.11 ** 0.13 ** 0.13 ** 0.13 ** DDRY ** 0.15 ** 0.17 ** 0.16 ** REARVET NS 0.15 ** 0.16 ** 0.17 ** 0.17 ** MAST1 NS NS NS 0.05 NS REPRO NS * 0.05 OTHD1 NS NS NS 0.07 * 0.05 DIAMT 0.09 ** 0.10 ** 0.08 ** 0.06 * 0.08 ** UH NS NS 0.10 ** 0.12 ** 0.11 ** HTDN y NS 0.20 ** 0.26 ** 0.31 ** 0.26 ** FEEDEF y 0.34 ** 0.37 ** 0.41 ** 0.41 ** 0.41 ** BW NS 0.11 ** 0.15 ** 0.17 ** 0.14 ** SHOOK NS 0.08 ** 0.09 ** 0.09 ** 0.09 ** WHOOK NS 0.06 * 0.09 ** 0.12 ** 0.08 ** RUMPL NS 0.09 ** 0.12 ** 0.15 ** 0.13 ** WCHEST * 0.06 NS 0.06 DCHEST NS 0.11 ** 0.12 ** 0.13 ** 0.11 ** WITHERH x NS 0.09 ** 0.08 ** 0.07 * 0.06 * z Based on 823 animals. y Based on 930 animals. x Based on 1061 animals., *, ** P 0.10; P 0.05; P 0.01, respectively; NS, non significant. lower udders. The current study found corresponding results (Table 9). De Haan et al. (1992) examined phenotypic relationships between net income, days of productive life, production, and linear type traits in grade and registered Holstein. Coefficients of determination for a prediction of DLPOC by a model that included first lactation product value, stature, fore udder attachment, rear udder height, and udder depth was Only product value, fore udder attachment, and rear udder height were significant (P < 0.01). The coefficient of determination was slightly lower in the current study (0.35 Model 1 A; Table 3). This study also confirmed significance of the effect of udder height. Gilmore (1977) studied the predictive value of first lactation yield and conformation to dairy cattle profitability. He found that only milk, fat and dairy character were significant predictors of annualized net income. The current study also found milk revenue in first lactation to be a significant indicator of lifetime profit, but did not consider dairy character. However, traits such as teat diameter and udder height were found to be significantly related to lifetime profit. Regarding the importance of body weight at 112 d in first lactation as a predictor of lifetime profit, this study found it to be nonsignificant. This is similar to findings by Andrus and McGilliard (1974). Gill and Allaire (1976) found a small negative phenotypic correlation of weight at first freshening with profit per day of life and lifetime profit ( 0.13 and 0.08). This is opposite to phenotypic correlations of body weight at 112 d in first lactation with all profit measures considered in this study; all correlations were positive (0.11 to 0.17) except for DLPOC, which was negative ( 0.03) and nonsignificant.

7 KULAK ET AL. EARLY PERFORMANCE TRAITS VS. LIFETIME PROFITABILITY IN HOLSTEIN COWS 623 Work by Gilmore (1977) reported that body capacity was not a significant predictor of annualized lifetime profit. Despite low positive correlations of body weight at 112 d in first lactation with profit measures, this trait was not found to be significant in the present study either. Balaine et al. (1981) found that correlations of total income, value of product, value of milk, value of fat, and value of protein in first lactation with lifetime profit were 0.65, 0.65, 0.67, 0.59, and 0.65, respectively; with lifetime profit per day of productive life correlations were 0.63, 0.63, 0.65, 0.57, and 0.63, respectively; and with efficiency, correlations were high, 0.62, 0.62, 0.64, 0.55, and 0.62, and significant. Results were based on 47 animals with three completed lactations. Balaine et al. (1981) concluded that the total value of product and the value of the main components in first lactation are useful as predictors of profit. The present study found that milk revenue in first lactation was a significant predictor in all profit measures; correlations ranged from 0.44 for DLPOC to 0.74 for ADLP LPL. Balaine et al. (1981) reported negative and significant phenotypic correlations of mastitis cost and breeding services cost to profitability of a dairy cow: 0.41 and 0.20 with lifetime profit, 0.41 and 0.23 with profit per day of productive life, and 0.44 and 0.23 with efficiency. The present study included number of mastitis treatments in first lactation, which is different from Balaine et al. (1981), who had mastitis cost as a variable. The only significant correlation of mastitis treatments in the present study was with ADLP LPL ( 0.05). However, significance was only at the 10% level. Balaine et al. (1981) also reported correlations of number of services per conception and days open of 0.18 and 0.31 with lifetime profit, of 0.17 and 0.03 with profit per day, and of 0.18 and 0.13 with efficiency. The present study considered days open as two variables: days from calving to first breeding and days from first breeding to conception. Only days from first breeding to conception was found to be significant for all profit measures. Milking speed was found to be significantly related to lifetime profitability of a dairy cow in the present study. The high coefficient for 3 min yield (Tables 3 and 4) could be interpreted as the impact of milking speed on yield or culling in later lactations, given first lactation milk revenue. Health traits in first lactation, such as mastitis and reproduction were found to have no significant impact on lifetime profit. This can be explained by the fact that these problems have a greater incidence in later lactations and noting that milk discarded because of mastitis was not accounted for in the computation of profit measures. However, weak correlations were found for mastitis with ADLP LPL, and for reproduction and other diseases with ADLP LPL and EF. More detailed studies are required to clarify these relationships. Early indicator traits explained only half as much variation in lifetime profit as lifetime traits for DLP and DLPOC, and around 75% as much for ADLP LTL, ADLP LPL, and EF (Kulak et al. 1997). There was a small benefit of including quadratic effects in the prediction model (an increase in R 2 of only 2% for DLPOC). However, it should be noted that the interactions between traits were not considered because of increased complexity of the model. CONCLUSIONS Milk revenue in first lactation was the most important first lactation predictor of lifetime profit, followed by 3 min yield, udder height and first lactation survival. Age at first calving, number of days from first breeding to conception in first lactation, and teat diameter were significant, with negative coefficients. It is recommended that those reproduction and type traits that were identified as significant (udder height, age at first calving, days from first breeding to conception in first lactation and teat diameter) should be given more attention in dairy management for improvement of lifetime profitability of a dairy cow. Results in this study were based on data from experimental herds, although management strategies were designed to mimic management in the field. In addition, relationships may change over time due to changes in management, genetics and production levels. Therefore further research using field data would be warranted. 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