Prediction of Lifetime Relative Net Income from First Lactation Production and Individual Type Traits in Holstein Cows 1'2

R J. TIGGES, 3 R. E. PEARSON, and W. E. V INSON Department of Dairy Science

Virginia Polytechnic Institute and State University Blacksburg 24061

ABSTRACT

Official type classification data and Dairy Herd Improvement Registry pro- duction records of Holstein cows calving between January 1, 1967, and June 1, 1976, were used to estimate contribu- tions of individual descriptive type traits evaluated in first lactation to lifetime profitabil i ty as measured by a profit function, relative net income. Relative net income estimated total profit from variables available through Dairy Herd Improvement. Contributions of individual type components to profi tabil i ty were estimated from least squares constants adjusted for all descriptive type traits and for linear and quadratic effects of final score, first lactation production, age at first calving, herdlife opportuni ty, stage of lactation, and age when classified.

For the model to predict total profit, regressions were most significant for udder traits. Significant positive regres- sions were for plain or coarse head ; f i rmly attached high and wide rear udder; and desirable teat size and placement. Signifi- cant negative regressions were for narrow and pinched, loose or broken rear udder; lack of defined udder support ; and winged shoulders.

Differences in total profit for body, feet, and hind legs were relatively unim- portant as compared with alternative

Received September 24, 1984. Part of the Southern Regional Dairy Cattle Breed-

ing Project S49 (Genetic Methods for Improving Dairy Cattle for the South).

2Partially supported by a grant from the Holstein- Friesian Association of America.

3Department of Dairy Science, Louisiana State University, Baton Rouge.

codes for udder traits. Codes considered conformationally most desirable for rear udder, udder support, and teats were also most desirable for total profit.

INTRODUCTION

The primary goal in a breeding program is to increase cow profitabili ty, either measured as lifetime profit or profit per unit t ime; the latter is the trait dairy producers seek to maximize. Numerous researchers have developed profi t functions to account for income and expense items over the cow's lifetime (1, 2, 8, 9, 10, 14, 16, 21). These functions differ mainly in com- pleteness and estimation methods [see review (18)I.

Norman et al. (16), utilizing data from over 10,000 Jersey cows, introduced Relative Net Income (RNI), a profit function computed from variables available in Dairy Herd Improve- ment Program. The RN1 was designed to reflect major differences among cows in income and expense.

Tigges et ai. (19) found that RNI and RNI per day accounted for 95 and 86% of the varia- tion among cows for total and per day profita- bility. Normal variation in income and expense items did not markedly affect cow profi tabil i ty rankings. The RNI is sufficiently accurate to be employed for establishing the relative economic importance of traits measured early in the ani- mal's lifetime.

Cow profi tabil i ty is a function of production and longevity. Time required for profitabil i ty to be expressed prohibits direct selection on the trait. A number of researchers have estimated relationships of early type traits with lifetime product ion traits (5, 10, 12, 13, 16, 17). Correlations among overall type appraisals and measures of longevity have been moderately positive, but specific type components indi- vidually are only slightly related to longevity measures (12, 16). Catron (5) found the rela-

1986 J Dairy Sci 69:204-210 204

PREDICTION OF LIFETIME INCOME 205

tionship between longevity measures and Pre- dicted Difference Type, descriptive traits, and scorecard categories to be small. High, wide rear attachments, strong udder support , and correct teat placement were associated with increases in longevity. Traits related negatively to longevity were upstandingness, level rump, and straight hind legs (5).

Honnette et al. (13) predicted lifetime milk and fat yields from first lactation production and type data. Differences in herdlife and life- t ime milk yield due to differences in descriptive codes for body, feet, hind legs, and teat size and placement traits were relatively unimpor- tant as compared with alternative codes for fore udder, rear udder, udder support, and miscel- laneous traits. Alternative codes considered conformational ly ideal for nonudder traits often were associated with average or below average herdlife and lifetime milk yield. Con- versely, codes more desirable for fore udder, rear udder, and udder support were associated with greater lifetime milk yield and longer herdlife.

Objectives of this s tudy were to determine the extent that differences in profitabili ty, as measured by RNI, can be predicted from indi- vidual descriptive type traits appraised during first lactation by the Holstein Association of America (11) and to determine contributions of these traits to profitabili ty, holding final score, and first lactation production constant.

M A T E R I A L S A N D METHODS

Data were official type classification data and Dairy Herd Improvement Registry produc- tion records of 34,675 Holstein cows calving between January 1, 1967, and June 1, 1976 (12). Records were edited to include only cows between 18 and 36 mo of age at first parturi- tion, which were classified first between 20 and 46 mo of age in the initial 305 d of first lacta- tion. Cows were from herds on continuous test, remained in the same herd for all lactations, were milked twice daily, and had from 270 to 600 d between each pair of successive parturi- tions. Lifetime yields of milk and fat were computed from DHIR records. First lactation records were from the Animal Improvement Programs Laboratory, US Department of Agri- culture, were adjusted to a 305-d mature equi- valent, and were deviations from weighted, contemporary yield (6).

Type traits were age-adjusted (4) final score and descriptive type codes from the Holstein classification system (11). The system com- prised 11 conformation traits and 1 miscel- laneous trait (12). Each trait had from three to five mutally exclusive codes. For analysis, the alternative code within each trait utilized was 1 and all other codes within the trait were 0.

Preliminary analyses indicated that all herd year effects in RNI could not be accounted for by including herd-year in the model. This was because approximately 85% of the observations were excluded from the final data set by the restrictions imposed. Thus, the results pre- sented will be based on RNI calculated from data deviated from all contemporaries (DRNI). The DRNI was calculated based on 1982 prices (19) as follows:

DRNI = (Deviated lifetime product value) x (net percentage)

+ (deviated number of freshenings) × (net calf value)

- (deviated rearing fixed costs)

- (deviated feed cost for growth after first calving)

- ( d e v i a t e d days of herd life) x (daily maintenance feed and fixed and operating cost)

where deviated lifetime product value = [(life- t ime milk - lifetime milk of contemporaries, kg) x $.1396] + [(lifetime fat - lifetime f a t o f contemporaries, kg) × $3.79)] ; net percentage = 83%, 17% of milk income needed for feed to support production (feed for maintenance, growth and reproduction included elsewhere); net calf value = $70 - $20 (two inseminations) - $9 (feed to support gestation); deviation rear- ing fixed cost = $.40 x (age at first calving, d - age at first calving of contemporaries, d); deviated feed cost for growth = $.15 × devia- t ion days from calving to 42 mo or disposal; daily maintenance feed cost = $.70, and daily fixed and operating cost = $1.82. Salvage value, feed cost to first calving, and initial value of the animal were included in original RNI; however, they did not vary from cow to cow. Thus, they were not included in the calculation of DRNI.

Multiple regression models predicting DRNI were examined. Independent variables were linear and quadratic effects of final score, first

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206 TIGGES ET AL.

lactation milk and fat production, herdlife opportunity (days from first calving to last available production testing date for the herd), ages at first calving and at classification, days in milk when classified, and descriptive type codes. A separate regression coefficient was fit for all but one of the alternative codes for each descriptive trait. The acceptable code was omitted in each case. The alternative codes in- cluded were 1 for the descriptive codes of the cow and 0 for all other codes (13). Importance of descriptive type codes was determined from actual and standard partial regression coeffi- cients adjusted for first lactation yield and final score differences. Final score adjustment was to remove effects on lifetime production variables of preferential treatment of higher scoring cows (12). First lactation milk and fat were included in models to determine contributions of indi- vidual type codes independently of first lacta- tion production.

R ESU LTS AN D DISCUSSION

Means and standard deviations for produc- tion traits of the 34,675 cows are in Table 1. Lifetime milk and fat production were within the range generally reported (7, 10, 20). Mean number of completed lactations was slightly less than reported by other workers (15, 21). Age adjusted final score was similar to those found by Catron (5). Age at first calving also was similar to those found in (10, 20). Mean relative net income was $1234 ($1.05/d

of herdlife). Means for all deviated traits were near zero in the original data set (12); however, cows surviving editing had means considerably lower for lifetime milk and fat, herdlife, RNI, and RNIPD.

Results from the regression model to predict deviated RNI (DRNI) are in Table 2. Twelve percent of the variation in profit was explained by the model. Interpretations of regression coefficients were hampered by inclusion of quadratic terms and highly related independent variables. Significant regressions were for linear and quadratic effects of final score and linear effects of first lactation milk and fat produc- tion, days in milk when classified, and herdlife opportunity.

Standard partial regression coefficients also were expressed as percentages of the sum of all absolute standard partial regression coefficients to determine the relative effects of independent variables on RNI. Linear and quadratic effects of final score accounted for 37% of the summed absolute standard partial regressions. However, a negative effect was found for the linear form and a positive effect for the quadra- tic form.

Summed relative effects for linear and quadratic terms of first lactation milk and fat slightly exceeded relative effects of descriptive traits. Relative effect of descriptive traits was 15%. First lactation type traits would appear to increase information of cow profitability after first lactation milk and fat production was

TABLE 1. Means and standard deviations of lifetime variables (34,675 cows).

Variable ~ Actual Contemporary deviations

SD X SD Lifetime milk, kg 17,688 13,454 -2,432 13, 313 Lifetime fat, kg 659 503 -90 498 ME first milk, kg 7,130 1,469 0 1,343 ME first fat, kg 256 52 1 47 Her dlife, d 1,010 668 - 153 697 Age at first calving, d 858 98 2.5 85 No. lactations 2.9 1.7 . . . . . . Final score 80.4 3.6 . . . . . .

RNI, $ 1,234 2,032 --126 1,885 RNIPD, $ 1.05 1.38 -.10 1.26

1 ME = Mature equivalent, RNI = relative net income, RNIPD = relative net income per day after first calving.

Journal of Dairy Science Vol. 69, No. 1, 1986

PREDICTION OF LIFETIME INCOME 2 0 7

TABLE 2. Regression coefficients for predicting de- TABLE 3. Regression coefficients for descriptive type viated relative ne t income, codes in predict ing deviated relative ne t income.

Regression Percent Regression Percent Variable ~ coefficients of sum s Trait Code I coefficients of s u m 2

FS - 1 5 1 . 2 3 " 16.1 Stature FS 2 1.22" 20.8 FM .21" 8.3 Head FM 2 9.58 X 10 -6 .8 FF 7.4* 10.4 FF 2 .01 .4 AFC - . 1 6 .4 AFC 2 3.13 × 10 -4 .2 Front end ACLS 50.42 6.3 ACLS 2 .74 6.3 DMC 1.25 * 3.8 Back DMC 2 -- .002 1.8 HLO - . 4 5 * 9.4 HLO 2 7.77 × 10 -s .8 Descriptive traits 15.0 Rump I ntercep t 5,428 R 2 .123

1FS = Final score, FM = first lactation milk, FF = first lactation fat, AFC = age at first calving, ACLS = age at classification, DMC = days in milk at classifica- tion, HLO = herdlife oppor tuni ty .

2Absolute s tandard partial regression coefficient expressed as a percentage of the sum of absolute stan- dard partial regression coefficients.

*Significant (P<.05).

k n o w n . Th i s w a s in c o n t r a s t t o t h e f i n d i n g s o f N o r m a n e t al. (16) .

R e g r e s s i o n c o e f f i c i e n t s f o r i n d i v i d u a l de- s c r i p t i ve t y p e t ra i t c o d e s a re in T a b l e 3. Be- c a u s e a l t e r n a t i v e c o d e s w i t h i n each t ra i t a re m u t u a l l y exc lus ive , d e p e n d e n c i e s e x i s t e d in t h e fu l l e q u a t i o n s . S o l u t i o n s w e r e o b t a i n e d b y o m i t t i n g e q u a t i o n s f o r c o d e 2 e f f e c t s f o r all t r a i t s e x c e p t u d d e r s u p p o r t , w h e r e c o d e 1 w a s o m i t t e d , a n d m i s c e l l a n e o u s , w h e r e c o d e 0 w a s o m i t t e d (13) . T h e s e c o d e s w e r e s e l e c t e d s i n c e c o d e 2 r e p r e s e n t s " a c c e p t a b l e " c o n f o r m a t i o n , e x c e p t f o r u d d e r s u p p o r t a n d m i s c e l l a n e o u s , w h e r e c o d e s 1 a n d O, r e s p e c t i v e l y , a re d e e m e d a c c e p t a b l e . A c t u a l r e g r e s s i o n s t h u s r e p r e s e n t t h e e f f e c t o f a g i v e n c o d e r e l a t i ve t o t h e a c c e p t - a b l e c o d e f o r t h e t ra i t . R e l a t i v e e f f e c t s o f d e s c r i p t i v e c o d e s w e r e d e t e r m i n e d b y s t a n d a r d pa r t i a l r e g r e s s i o n s fo r e a c h code , w h i c h w e r e a p e r c e n t a g e o f t h e a b s o l u t e s u m o f c o e f f i c i e n t s f o r all d e s c r i p t i v e codes . F r e q u e n c i e s o f e a c h c o d e w e r e a c c o u n t e d f o r in t h e p e r c e n t a g e s ,

Hind legs

Feet

Fore udder

Rear udder

Udder suppor t

Teats

Miscellaneous

1 - 1 2 . 7 1.2 3 54.7 3.7

1 23.2 .6 3 - . 2 0 4 51.1" 4.8 5 - 1 1 . 2 .5

1 - 4 3 . 8 3.1 3 - 6 4 . 3 2.5 4 47.3 3.1

1 - 3 5 . 2 3.1 3 .9 0 4 - 1 3 . 1 .9

1 - 6 7 . 4 2.7 3 - 1 5 . 7 1.0 4 17.6 1.5 5 10.4 .7

1 - 9 . 6 0 3 - 1 7 . 9 1.7 4 63.7 3.9 5 - 4 8 . 7 2.5

1 - 6 6 . 8 2.5 3 - 3 3 . 3 1.6 4 20.0 1.7

1 30.7 1.4 3 - 4 . 7 1.4 4 - 4 0 . 7 3.5 5 - 5 8 . 7 1.1

1 117.1" 5.2 3 - 2 4 . 3 2.1 4 - 8 1 . 9 " 5.2 5 - 1 9 1 . 1 " 4.4

2 - 6 2 . 2 * 4.4 3 - 7 3 . 9 1.9 4 - 1 3 . 9 .7 5 - 2 6 1 . 1 4.0

1 63.2* 5.6 3 93.8 2.0 4 17.1 1.4 5 - - 4 5 , 6 2.1

1 - 2 6 6 . 1 " 4.5 2 27.2 1.8 3 55.4 2.7 4 - 4 1 . 6 .4 5 7.5 .3

1 Omit ted codes set to zero for solution.

2Absolute s tandard partial regression coefficient expressed as a percentage of the sum of absolute stan- dard regression coefficients for the descriptive traits.

*Significant (P<.05).

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2 0 8 T I G G E S ET AL.

because standard deviations of descriptive type traits were determined by their frequencies.

Most significant regressions were found for udder traits. Positive regressions were signifi- cant (P<.05) for head 4, plain or coarse; rear udder 1, firmly attached, high, and wide; and teats 1, plumb, desirable length, size, and place- ment. Negative significant regressions were for rear udder 4 and 5, narrow and pinched, and loose or broken; udder support 2, lack of de- fined halving; and miscellaneous 1, winged shoulders.

Thirteen of the 44 codes had coefficients exceeding +5% of mean RNI; however, only those mentioned were signiicant, due to tow frequencies of the other traits. Traits with large positive coefficients but low frequencies were hind legs 4, bone too light; and teats 3, rear teats back too far. Traits having large negative coefficients were front end 3, coarse shoulder and neck; rump 1, long and wide, nearly level; feet 1, strong, well formed; udder support 3, f loor too low; and udder support 5, broken.

Effects of descriptive type codes on RNI are in Figure 1 as a percentage of mean RNI. For symmetry, effects are presented as a deviation from the mean effect of all codes for each trait. Effects within a trait summed to zero, but dif- ferences between effects were as in regression models (Table 3).

Differences among alternative descriptive codes for body, feet, and leg traits had little impact on lifetime profitabil i ty; differences among alternative codes for rear udder, udder support, and miscellaneous traits were substan- tially greater (Figure 1). Honnette (13), pre- dicting lifetime milk yield, found similar results with one noticeable exception. Alternative codes for fore udder had large effects on life- t ime milk yield, but effects on RNI were com- parable to body traits.

More nearly ideal conformational codes for nonudder traits (generally codes 1 and 2) often were associated with average or below average profit. Codes deemed most desirable had least total profit for stature, back, rump, and feet. In

TRAIT -18

STAT U R E

HEAD

FRONT END

BACK

RUMP

HIND LEGS

FEET

FORE UDDER

REAR UDDER

UDDER SUPPORT

TEATS

MISCELLANEOUS

-18

-114 / ~ , - 6 14 l

.5

5

_, ,

- 2 2 6 DO l I I I I I I | !

I zl 3

5321 I 4

I 3 I 2 4

I 1 423

325 4

I 5 31 2 4

1 I 3 2 4

L 5 4 32 I

I 4 3 Z

1 32 4 1

1 5 2 4 I 3

I 4 0 5 2 3 i

I I I i I I I

-2 2 6 I0

Figure 1. Effects of descriptive type codes as a percentage of mean relative net income.

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PREDICTION OF LIFETIME INCOME 209

TABLE 4. Effects on population average relative net income (RNI) from replacing indicated type codes with codes omitted for solutionfl

Subtrait RN1

(S) Stature 1 4.05

3 -7 .60 Head 1 - .42

3 .03 4 -18.04 5 .57

Front end 1 6.96 3 2.70 4 -5 .96

Back 1 10.24 3 - .10 4 1.90

Rump 1 2.96 3 1.93 4 -4 .36 5 -1 .54

Hind leg 1 .11 3 7.70 4 -6 .69 5 3.65

Feet 1 2.54 3 2.26 4 --5.12

Fore udder 1 - 1.78 3 .54 4 10.70 5 .53

Rear udder 1 -6 .32 3 6.73 4 9.58 5 2.67

Udder support 2 9.70 3 1.26 4 1.07 5 1.57

Teats 1 -17.88 3 -1.13 4 -3.98 5 2.60

Miscellaneous 1 1.86 2 -3.71 3 -3 .60 4 .08 5 - . 4 5

1Negative products of code effects and code frequencies.

contrast, codes considered conformat iona l ly most desirable for fore udder, rear udder, and udder suppor t were also most desirable for to ta l profit .

Effect on the popula t ion average of re- placing all cows of a given code with cows having the acceptable code omi t t ed f rom the analysis (code 0 for miscellaneous, 1 for udder support , 2 for all o ther traits) are in Table 4. These values ref lect bo th the f requency of the code and the difference in prof i tabi l i ty be tween animals of this code and animals coded accept- able. For example, by replacing a code 1 s tature cow with a code 2 s tature cow of identical first milk, fat, final score, etc., an increase in to ta l prof i tabi l i ty o f $4.05 would be expected.

Largest increase in prof i tabi l i ty would be ob- tained by replacing code 1 f ront end ( smooth shoulder, wide chest), code 1 back (straight, strong), code 3 hind leg (sickled), code 4 fore udder (bulgy or loose), codes 3 or 4 rear udde r (low, narrow and pinched) wi th code 2; and replacing code 2 udder suppor t (lack o f defined halving) with code 1.

CONCLUSIONS

Preceding analyses have shown tha t produc- t ion and type traits available in first lactat ion do no t explain a large percentage of the varia- t ion in RNI (Table 2). However, udder traits were shown to be much more impor tan t than body traits (Table 3).

Specifically, scores for rear udder, udder support , and teats were most important . These data suggest selecting for the highest milk yield while avoiding animals with the negative ex- t remes (code 5) for rear udder , udder sup- port , and teats.

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