180 likes | 200 Vues
Study analyzing crossbred and purebred dairy cows in the US based on yield traits and heterosis effects for economic comparisons.
E N D
Objectives • Document the number and type of crossbred cows in the US. • Estimate heterosis and breed differences using cows of different breed composition competing in the same herd. • Compare the economic merit of crossbred and purebred cows.
Traits Considered • Milk, fat, and protein yields • Somatic cell score (SCS) • Productive life (PL) • Linear type composites not available • Body size estimates obtained from literature • Udder and leg trait estimates assumed zero • Net merit, cheese merit, fluid merit calculated • Adjusted to Holstein scale • Fertility, mortality, and calving ease not available
Breeds Are Evaluated Separately • Separate data sets reduce bias in evaluations within breeds, but provide: • No evaluations for crossbreds • No method to compare cows across breeds • New Zealand, Australia, and the Netherlands include crossbreds and account for heterosis in evaluations. • USDA-DHIA evaluations exclude crossbred cows unless identified as part of a “grading-up” program.
Yield Traits & SCS Data • Data were from the national test-day database available May, 2001. • 572 herds each with at least 5 crossbred cows • 10,442crossbred cows born since 1990 • 140,421 purebred herdmates (80% were Holstein) • Crossbreds defined by sire breed and maternal grandparent breeds. • Sires were purebred, dam breed used for unknown maternal grandparent breed • XX (crossbred) not accepted for maternal grandparents • Holstein and Red & White considered one breed
Number of F1 & Purebred CowsIn Mixed Breed Contemporary Groups
Number of F1 & Backcross Cows With Holstein Sire or Grandparent
Results • Estimated breed means • Estimates of heterosis • Economic comparisons • Rank other breeds on Holstein base • Some new crossbreeding theory
Crossbreeding TheoryHolstein Brown Swiss Protein Yield 0.96 0.94 0.92 Protein kg/d —Additive (A) only 0.90 — A+Dominance (D) max heterosis (H) 0.88 —A+D min H —A+D+AA max H 0.86 —A+D+AA min H 0 25 50 75 100 % Holstein genes — Holstein mean
Merit of F1 Holstein Crossbreds Compared to 2000 genetic base for Holstein
Conclusions • Currently< 0.5% of DHI cows are crossbred. • Heterosis was about 4% for yield traits, < 1% (unfavorable) for SCS, and 1% for PL. • Profit from Jersey Holstein and Brown Swiss Holstein crosses is higher than from Holsteins. • Fewer extreme bulls are found in minor breeds. • Backcross yields were higher than expected.
Holstein Guernsey USDA Yearbook of Agriculture 1947 From 1939-1954, M.H. Fohrman studied 113 Guernsey, Jersey, Holstein, and Red Danes crosses at Beltsville. Another study of 137 Ayrshire, Brown Swiss and Holstein crosses was conducted from 1959-1968 (McDowell and McDaniel, 1968).
Holstein Jersey USDA Yearbook of Agriculture 1947 All cows sired by Beltsville Holstein No. 966
Jersey Holstein USDA Yearbook of Agriculture 1947 X-1 and X-47 were sired by an unidentified Jersey sire. All others sired by Beltsville Jersey No. 1114
Three-Breed Crosses USDA Yearbook of Agriculture 1947 Butterfat yield of three breed crosses was greater than from their F1 crossbred dams. Three breed crosses averaged 14,927 pounds of milk and 641 pounds of butterfat as 2-year-olds in 1947.