| Abstract |
The main objectives of the present study were: 1) to evaluate
genetically some lactation, reproduction, semen and growth traits in some
Egyptian buffalo herds through estimating the variance components and
heritability using Bayesian Gibbs Sampling Algorithm applying single trait
animal model and random regression model (RRM), 2) to predict the
breeding values (PBVs) and plot the genetic and phenotypic trends for these
traits using BLUPF90 software, 3) to characterize on SNPs basis some
candidate genes of PRL, DGAT1, FSHR and GH in Egyptian buffalo, 4) to
use PCR-RFLP technique in genotyping the SNP genotypes located in the
promoter regions of these genes, and 3) to detect the molecular associations
of SNP genotypes of PRL, FSHR and GH candidate genes with milk
production and composition, reproduction, semen and body weight traits in
Egyptian buffalo using generalized least square means procedure (GLSM).
For quantitative genetic analyses in this study, four sets of data in
terms of lactation, reproduction, semen and body weights were used. A
pedigreed file of 7345 Test-Day (TD) records of milk (TDMY), fat
(TDFY), protein (TDPY) yields and somatic cell scores (TDSCS) were
gathered monthly from 686 buffaloes, daughters of 83 sires and 423 dams
for a period of 21 years starting from 2003 up to 2023 in three experimental
buffalo herds of El-Nattafe El-Gadid (NG), El-Nattafe El-Kadim (NK) and
El-Gimmeza (EG). Also, a total number of 7279 reproduction records of
age at first calving (AFC), days open (DO) and calving interval (CI)) were
collected for a period of 22 years (2002 to 2023) from 1951 buffaloes,
daughters of 155 sires and 1179 dams in six experimental herds of NG, NK,
EG, El-Nubariya (EN), El-Serw (ES) and Sids (S). Data of 5178 semen
ejaculates were collected from 111 Egyptian buffalo bulls produced from 34
sires and 92 dams during 10 years from 2013 to 2022 in two herds of the
International Livestock Management Training Center at Sakha (IMTC) and
Mahalet Mousa (MM), Kafr El-Sheikh Governorate. Data on body weight at
birth and weaning were collected from 8229 buffalo calves, progeny of 277 sires and 2175 dams for a period of 22 years from 2003 to 2024 in six experimental
herds of NG, NK, EN, ES, EG and S. All the herds are belonging to the
Animal Production Research Institute (APRI), Agricultural Research Center
(ARC), Ministry of Agricultural and Land Reclamation (MALR), Egypt.
For molecular analyses in this study, blood samples from 286
animals (200 female and 86 male) in three herds of NG, NK, and EG were
randomly collected from buffalo animals for genotyping using PCR-RFLP
technique. The candidate genes of GH, PRL and FSHR were investigated in
terms of the association of these genes with lactation, reproduction, semen
and growth traits.
5.1 Quantitative genetic analyses for lactation traits
Heritability values estimated by repeatability single-trait animal
model for lactation traits were mostly moderate, ranging from 0.05 to 0.40
for TDMY, 0.05 to 0.45 for TDFY, 0.06 to 0.44 for TDPY and 0.03 to 0.39
for TDSCS, while those values estimated by RRM for lactation traits were
mostly low at the beginning of lactation, increased gradually to reach the
highest value then decreased gradually to reach the lowest value towards the
end of lactation. The heritabilities estimated by RRM ranged from 0.04 to
0.25 for TDMY, 0.05 to 0.18 for TDFY, 0.03 to 0.23 for TDPY and 0.07 to
0.57 for TDSCS. The ranges in PBVs for lactation traits were moderate or
high, being -2.01 to 3.4 kg for TDMY, -358 to 521 g for TDFY, -53 to 95 g
for TDPY and -0.183 to 0.313 log10 for TDSCS. The plotted genetic trends
for lactation traits were increased favorably from -4.63 to 1.61 kg for
TDMY, -5.0 to 495 g for TDFY and -26 to 280 g for TDPY, along with
favorable decrease of 1.37 to 1.19 log10 in the genetic trend of TDSCS over
time of lactation. On the contrary, the phenotypic trends of lactation traits
were decreased unfavorably from 7.49 kg to be 5.69 kg for TDMY, 510 g to
be 360 g for TDFY and 284 g to be 223 g for TDPY with unfavorable
increase from 1.62 to be 2.43 log10 for TDSCS. 5.2 Quantitative genetic analyses for reproduction traits
Heritability estimated by single-trait animal model for reproduction
traits were low, being 0.10 for AFC, 0.02 for DO and 0.02 for CI. The
ranges in PBVs were moderate or high, being -8.24 to 10.84 mo for AFC, -
124.7 to 123.9 d for DO and -141.8 to 132.5 d for CI. The genetic trends
were favorably decreased from 0.24 mo to be -0.14 mo for AFC, 5.5 d to be
2.9 d for DO and 6.9 d to be 3.6 d for CI. Wide ranges in values of the
phenotypic trends of reproduction traits were observed, in terms of 36.6 mo
to be 36.5 mo for AFC, 127 d to be 71 d for DO and 416 d to be 354 d for
CI.
5.3 Quantitative genetic analyses for semen traits
Heritability estimated by single-trait animal model for semen traits
were moderate, being 0.17, 0.28, 0.27, 0.27 and 0.23 for ejaculate volume
(EV), motility of sperms (MS), live sperms (LS), abnormal sperms (AS)
and sperms concentration (SC), respectively. The ranges in PBVs were
moderate or high, being -0.63 to 0.42 ml for EV, -27.3 to 85.0 % for MS, -
27.3 to 81.7 % for LS, -3.7 to 24.8 % for AS and -1.2 to 2.5×109
sperm per
ml for SC. The genetic trends for semen traits were increased favorably
over time from 1.99 to 2.3 ml for EV, 36.8 to 47.8 % for MS, 35.6 to 47.8
% for LS, 2.3 to 5.9% for AS and 0.39 to 1.24×109
sperm per ml for SC.
The phenotypic trends for EV, MS and LS were decreased from 4.1 to 3.1
ml for EV, 68.2 to 57.1 % for MS and 67.4 to 56.2 for LS, while the trends
were increased from 3.1 to 8.1% for AS and from 0.6 to 1.3×109
sperm per
ml for SC.
5.4 Quantitative genetic analyses for growth traits
Heritability values estimated by animal model for body weight at
birth (BW), weaning weight (WW) and daily gain from birth to weaning
(DG) were mostly moderate or high, being 0.26 for BW, 0.50 for WW and
0.55 for DG. The PBVs ranging from -4.2 to 3.5 kg for BW, -42.4 to 44.2
kg for WW and -0.44 to 0.52 kg for DG. The genetic trends for body
weights and gains increased slightly favorably from 1.6 to 1.8 kg for BW, |
