Accounting for Scale Effects

1

Lopez-Villalobos, Garrick, Peluffo and Laborde -Across-breed Evaluation of Dairy Cows

ACROSS-BREED GENETIC EVALUATION OF

ARGENTINEAN DAIRY CATTLE

Nicolas Lopez-Villalobos1, Dorian J. Garrick1 , Luis Peluffo y Daniel Laborde

1 Institute of Veterinary, Animal and Biomedical Sciences

Massey University, Palmerston North

Ph +64-6-3505103, Fax +64-6-3505699

April 2000

SUMMARY

Across-breed estimated breeding values (EBV) and estimated producing values (EPV) for lactation yields of milk, fat and protein and for body weight and body condition score of straightbred Holstein and Jersey and crossbred Holstein x Jersey dairy cows in 2 Argentinean herds were estimated by Best Linear Unbiased Prediction (BLUP) procedures. Evaluations were based on records of 856 cows using a repeatability animal model.

Averages and standard deviations of lactation yields of milk, fat and protein, estimated by interval centering method using alternate monthly daily herd tests, were 3,546  1,226 L, 136  48 kg and 127  42 kg, respectively. Average days in milk were 224  68. Averages of body weight and condition scores were 425  62 kg and 4.8  0.4 points. Differences in average EBV (including breed effects) for lactation yields of milk, fat and protein and body weight and condition score for Holstein cows compared to Jersey cows were 613 L, –7.2 kg, 8.4 kg, 76 kg and 0.1 points, respectively. First cross heterosis estimates were –121 L milk, 0.5 kg fat, –0.6 kg protein, –3.5 kg body weight, and –0.03 units of condition score.

DATA AND METHODS

Luis Peluffo, an Argentinean dairy farmer, provided records of 856 cows calving in the year 1999 in two herds. Cows were classificated by visual inspection into one of five breed groups, Holstein (H), Jersey (J), ¾ H ¼ J (CH), ½ H ½ J (C), and ¼ H ¾ J (CJ).

Total lactation yields were calculated from alternate monthly test-day records using the interval centering methodology. A few cows had missing observations such that there were 850 lactation records and 854 body weight and condition score records.

Estimated breeding values (EBV) and estimated producing values (EPV) for lactation yields of milk, fat and protein were obtained by BLUP (Best Linear Unbiased Procedures) procedures. The model equation used to describe the lactation yields included the following effects:

herd-month - this effect accounted for differences in yields that result from management and feeding differences between groups of cows lactating in different herds and different months,

lactation number – this effect was included as a covariable with linear and quadratic effects,

proportion of Holstein genes – this accounted for breed effects,

heterosis – this effect was used to account for non-additive effects in cross-bred cows,

days in milk - this effect was included as a covariable with linear and quadratic effects,

genetic merit of the individual animal,

permanent environmental effects of the individual cow, and

residual or temporary environmental effects.

The model equation used to obtain EBVs and EPVs for body weight and condition score was the same as that used for lactation yields but days in milk were replaced by days from calving to day of maesuring body weights and condition scores. Days at measurement were included as covariables with linear, quadratic and cubic effects.

In this data set herds were not connected, as there were not sires with progeny across herds. Therefore, selection and culling decisions should be made on within-herd basis.

Breeding values were calculated to allow for direct across-breed comparison. That is, they included the breed additive group effect and the within-breed genetic merit. Production values included the genetic merit, plus heterosis (where appropriate) and permanent environmental effects.

Two economic indexes were calculated, economic value of genetic merit (EVGM) and economic value of production merit (EVPM). The EVGM was calculated as the sum of the products between EBV for lactation yields of milk, fat, protein, and body weight and respective relative economic values. Similarly, the EVPM was calculated as the sum of the products between EPV for lactation yields of milk, fat, protein, and body weight and respective relative economic values. Relative economic values used to calculate EVGM were – A$0.024/L milk, A$0.4/kg fat, A$1.675/kg protein, and – A$0.215/kg of body weight. Relative economic values to calculate EVPM were – A$0.031/L milk, A$0.585/kg fat, A$2.105/kg protein, and – A$0.290/kg of body weight. These relative economic values were the same to those used in New Zealand (Livestock Improvement, 1999) converted to Argentinean Pesos. In the near futuro, relative economic values should be calculated for Argentinean conditions.

RESULTS

Averages and standard deviations of lactation yields of milk, fat and protein were 3,546  1,226 L, 136  48 kg and 127  42 kg, respectively. Average days in milk were 224  68. Averages of body weight and condition scores were 425  62 kg and 4.8  0.4 points. Average of productive performance adjusted for lactation number and days in milk (in the case of lactation yields) or days at measurment (in the case of body weight and condition score) of the different breed groups are showed in Figures 1, 2 and 3.

Figure 1: Effect of the breed of cow on lactation milk yield.

Figure 2: Effect of the breed of cow on lactation fat and protein yield.

Figure 3: Effect of the breed on cow body weight.

Straightbred Holstein cows produced more milk and protein, less fat and were heavier than straightbred Jersey cows. Cows classified as ½ H ½ J had productions and weights that were intermediate between Holstein and Jersey cows. Estimates of first-cross heterosis were –121 L milk, 0.5 kg fat, –0.6 kg protein, –3.5 kg body weight, and –0.03 units of condition score. Caution should be taken in interpreting these estimates as cows were classified into one of the breed groups by visual inspection and not by pedigree records.

Averages of EBV and EPV for the traits analysed for each of the breed groups are shown in Table 1. Differences in average EBV (including breed effects) for lactation yields of milk, fat and protein and body weight and condition score for Holstein cows compared to Jersey cows were 613 L, –7.2 kg, 8.4 kg, 76 kg and 0.1 points, respectively.

Table 1: Averages for breed groups.

Breeding values can be used to select the animals as parents for the next generation and producing values can be used in culling decisions, along with on-farm information.

Keys used in the Cow Summary

Herd

Herd identifier where the cow is located.

Cow ID

This is the unique across-herd animal identifier used for this evaluation.

Calving date

Calving date of the cow.

Lactation number

Lactation number of the cow.

Breed

This is the breed group where the cow was classified. There were 5 groups, Holstein (H), Jersey (J), ¾ H ¼ J (CH), ½ H ½ J (C), and ¼ H ¾ J (CJ).

Total Lactation and Body Weight Records

Details of lactation yields of milk, fat, and protein adjusted to 224 days in milk as well as actual body weight and condition score are shown for each cow.

EBV

These are the breeding values of the cow for lactation yields of milk, fat, and protein and body weight and condition score. Yields were adjusted for days in milk and body weights and condition scores were unadjusted for days after calving in that the cow was weighted and body scored. EBV can be used to compare cows from different breed groups as breed effects were accounted for. EBV should be used to aid in the choice of parents for replacements.

EPV

These are the estimated production values of the cow for lactation yields of milk, fat, and protein and body weight and condition score. EPV can be used to compare cows from different breed groups as heterosis effects were accounted for. EPV should be used to aid in the choice of cows to retain for future lactations.

Economic Value of Genetic Merit (EVGM) and Economic Value of Production Merit (EVPM)

These two economic indexes combine the genetic evaluations for each trait of a cow with its corresponding relative economic values. EVGM should be used to aid in the choice of cows to breed replacements and EVPM to retain cows for future lactations.

April, 2000. Institute of Veterinary, Animal and Biomedical Sciences, Massey University