AGB 211: Livestock and Poultry Breeding (2+1)

SIRE INDEX

Sire index is the estimate of the hereditary potentialities of a bull for milk production or any other trait. The sire’s transmitting ability for production is estimated by mathematical means and expressed as sire index or bull index. In other words, breeding values of the bulls are expressed by sire indices. Several indices for assessing the breeding worth of sires have been developed. They are as follows:

• Simple daughter average index (Edward, 1932)

S_I = D_i = [1 / m_i] Σ D_ij

where, D_ij = yield of j^th daughter of the i^th sire

m_i = number of dams mated to i_th sire

• Yapp’s index or Equiparent index (Yapp, 1925)

P = S + D / 2

S + D = 2P

S_I = 2P - D 

where, P = average of the progeny

D = average of the dams

• Mount hope index (Goodale, 1927)

SI = D + 3/7 (D – M) when daughter’s average exceeds dam’s average

= D – 7/3 (M – D) when daughter’s average is less than dam’s average

where, D = average of the daughters

M = average of the dams

• Gifford’s index (Gifford, 1930)

S_I = 2P - H

where, H = herd average

• Wright’s index (Wright, 1931)

SI = [2 / n+2] + [H / n+2 ] X (2P – D)

where, n = number of dam-daughter comparisons

H = herd average

P = daughters average

D = dams average

• Corrected daughter average index or Krishnan’s index (Krishnan, 1956)

S_I = D – b_DM (M – H)

where, D = daughters average

b_DM = intrasire regression of daughter on dam

M = dams average

H = herd average

• Dairy search index (Sundaresan, 1965)

S_I = A + [n / n+12] [(D – C_D) – b(M – C_M)]

where, A = herd average

n = number of daughters

D = daughters average

M = dams average

C_D = weighted average of contemporary daughters

C_M = weighted average of contemporary dams

b = regression coefficient

• Herdmate comparison (Henderson and Carter, 1957)

PD = [(n_i / (n_i + 20)] {D_i - 0.9 (HM_i – A) – A}

where, PD = predicted difference

D_i = average of the daughters at the i^th herdmate level

HM_i = average of the herdmates at i^th herdmate level

n_i = number of daughters at the i^th herdmate level

• Contemporary comparison

I = µ + {n / n + k} (D - C)

where, n = number of daughters

C = average of daughters’ contemporaries

k = ratio of error variance to sire variance

• Best linear unbiased prediction (BLUP) (Henderson, 1975)

Y_ijk = µ + F_i + S_j + E_ijk

where, Y_ijk = measurement on the k^th progeny of the j^th sire born in the i^th herd- year- season

µ = overall mean

F_i = effect of the i^th herd- year- season

S_j = effect of the j^th sire born

E_ijk = residual error