M. A. Hoque

Genetic associations of residual feed intake with serum insulin-like growth factor-I and leptin concentrations, meat quality, and carcass cross sectional fat area ratios in Duroc pigs.

Genetic relationships of measures of residual feed intake and daily feed intake with serum IGF-I concentrations at 8 wk of age and at 105 kg of BW, serum leptin concentration at 105 kg of BW, meat quality, and different fat accumulation traits on 834 Duroc pigs in 7 generations were estimated. Two measures of residual feed intake were estimated from the differences between actual and predicted feed intake: phenotypic residual feed intake (RFI(phe)) and nutritional residual feed intake (RFI(nut)). Meat quality traits included drip loss, cooking loss, pork color score, pork lightness (L*), and pH, whereas fat accumulation traits were subcutaneous fat, intermuscular fat, and total fat percent at 5-6th thoracic vertebra; subcutaneous fat, intermuscular fat, abdominal fat, and total fat percent at one-half body length and at last thoracic vertebra, and seam fat score. The IGF-I concentrations at 8 wk of age and 105 kg of BW had weak genetic correlations with measures of residual feed intake and daily feed intake (absolute values ranging from 0.14 to 0.24). The genetic correlations between measures of residual feed intake and serum leptin concentration were strong and positive (r(g) with RFI(phe) and RFI(nut) were 0.74 and 0.80, respectively). Residual feed intake was moderately but negatively correlated with cooking loss (r(g) with RFI(phe) and RFI(nut) were -0.42 and -0.49, respectively), whereas daily feed intake was moderately and positively correlated with drip loss and pH (0.33 and 0.36, respectively). Daily feed intake was also moderately correlated with subcutaneous fat accumulations at the 5-6th thoracic vertebra (0.31) and one-half body length (0.31) regions and was strongly correlated with accumulations at the last thoracic vertebra region (0.57). The genetic correlations between daily feed intake and intermuscular fat accumulations at all of the carcass sites were strong (0.60, 0.76, and 0.56 for intermuscular fat at 5-6th thoracic vertebra, one-half body length, and last thoracic vertebra, respectively). Residual feed intake was strongly and positively correlated with all of the fat accumulation traits (ranging from 0.53 to 0.88). The results indicate that reducing residual feed intake (increased efficiency) would lead to increased cooking loss and darkness, and decreased serum leptin concentration, fat accumulations at the different sites, and seam fat at the 6th rib interface of pork carcasses.

Genetic parameters for measures of energetic efficiency of bulls and their relationships with carcass traits of field progeny in Japanese Black cattle.

Records on 514 bulls from the sire population born from 1978 to 2004, and on 22,099 of their field progeny born from 1997 to 2003 with available pedigree information (total number = 124,458) were used to estimate genetic parameters for feed intake and energy efficiency traits of bulls and their relationships with carcass traits of field progeny. Feed intake and energetic efficiency traits were daily feed intake, TDN intake, feed conversion ratio (FCR), TDN conversion ratio (TDNCR), residual feed intake (RFI), partial efficiency of growth, relative growth rate, and Kleiber ratio. Progeny carcass traits were carcass weight (CWT), yield estimate, ribeye area, rib thickness, subcutaneous fat thickness (SFT), marbling score (MSR), meat color standard (MCS), fat color standard (FCS), and meat quality grade. All measures of feed intake and energetic efficiency were moderately heritable (ranged from 0.24 to 0.49), except for partial efficiency of growth and relative growth rate, which were high (0.58) and low (0.14), respectively. The phenotypic and genetic correlations between FCR and TDNCR were >or=0.93. Selection for Kleiber ratio will improve all of the energetic efficiency traits with no effect on feed intake measures (daily feed intake and TDN intake). The genetic correlations of FCR, TDNCR, and RFI of bulls with most of the carcass traits of their field progeny were favorable (ranged from -0.24 to -0.72), except with fat color standard (no correlation), MCS, and SFT. Positive (unfavorable) genetic correlations of MCS with FCR, TDNCR, and RFI (0.79, 0.70, and 0.51, respectively) were found. The SFT was negatively genetically correlated with FCR and TDNCR (-0.32 and -0.20, respectively); however, the genetic correlation between RFI and SFT was not significantly different from zero (r(g) = -0.08 +/- 0.12). Favorable correlated responses in CWT, yield estimate, ribeye area, rib thickness, MSR, and meat quality grade would be predicted for selection against any measure of energetic efficiency. The correlated responses in CWT and MSR of progeny were greater for selection against RFI than for selection against any other energetic efficiency trait. Results of this study indicate that RFI should be preferred over other measures of energetic efficiency to include in selection programs.

Influence of early postweaning traits on genetic improvement of meat productivity in purebred Berkshire pigs

The objective of this study was to estimate genetic parameters for growth and body composition traits at 60 d of age and at finish in a population of Berkshire pigs and to evaluate the effectiveness of selection at 60 d of age for meat productivity. A total of 4,548 purebred Berkshire (2,344 males and 2,204 females) pigs born between December 1994 and January 2005 were used in this study. The traits analyzed were BW at 60 d of age; daily BW gain from birth to finish, from weaning to 60 d, from weaning to finish, and from 60 d to finish; age at finish; backfat thickness at 60 d of age and at finish; loin eye area at 60 d of age (LEA60) and at finish; and the number of teats. The heritability estimates for BW at 60 d of age, daily BW gain from weaning to 60 d, backfat thickness at 60 d of age, and LEA60 were 0.22, 0.25, 0.49, and 0.22, respectively. The estimated common environmental effect for BW at 60 d of age, daily BW gain from weaning to 60 d, backfat thickness at 60 d of age, and LEA60 were 0.12, 0.13, 0.18, and 0.21, respectively. Therefore, the common environmental effect should be included in the model to analyze traits at 60 d of age. The positive genetic correlation between LEA60 and loin eye area at finish and the negative genetic correlation between LEA60 and backfat thickness at finish indicated that improvement of the ultrasonic loin eye area at 60 d of age may result in favorable correlated responses to the traits at finish, an increase in loin eye area, and a decrease in backfat thickness. In addition, genetic correlations of backfat thickness at 60 d of age with backfat thickness at finish and loin eye area at finish were found to be favorable, indicating that improvement of ultrasonic backfat thickness at 60 d of age may result in greater correlated responses to the traits at finish: an increase in loin eye area and a decrease in backfat thickness. Therefore, constructing a selection scheme that includes body composition traits at 60 d and traits at finish is practical for gaining a greater selection response.

Genetic parameters for dry matter, energy and protein intake, and their relationships with performance and carcass traits in Japanese Black cattle

Genetic parameters for feed intake and performance traits of 514 bulls and carcass traits of 22 099 of their progeny, and the relationships of measures of feed intake with performance and carcass traits were estimated. Feed intake traits were dry matter intake (DMI), concentrate intake (CONI), roughage intake, ratio of roughage intake to DMI, metabolizable energy intake (MEI) and digestible crude protein intake (DCPI). Performance traits included daily gain, metabolic weight, live weight at the end of test, dry matter conversion ratio and residual feed intake. Progeny carcass traits were carcass weight, percentage of meat yield, rib eye area (REA), subcutaneous fat, marbling score, meat colour (MCS), fat colour (FCS) and meat quality grade. All the feed intake and performance traits were moderately heritable. The heritabilities for REA and MCS were moderate, and that for FCS was low, while those for the other carcass traits were high. Selection against DMI, CONI and DCPI would reduce excessive intake of feed, but would have undesirable effects on growth and most of the carcass traits. Selection against MEI would lead to improvements in feed efficiency and growth traits. Selection against DCPI would also improve feed efficiency; however, responses in growth traits would decrease. Results indicate that selection against MEI might be better than any other measures of feed intake to improve feed efficiency with simultaneous improvement in growth and most of the carcass traits.

Genetic variability of maternal effect on body measurements and its intra- and inter-genetic relationship with direct effect in Japanese Black calves

This study was conducted to evaluate the importance of maternal effect on body measurement traits at an early stage of growth, and to estimate the genetic relationships between direct and maternal effects and among body measurement traits at 0 month (0-mo) and 4 months (4-mo) of age in a population of Japanese Black calves. Body measurements and body weight of 889 Japanese Black calves were estimated with the use of an animal model by the Residual Maximum Likelihood procedure. Direct heritabilities were low to moderate, ranging between 0.17 ± 0.09 and 0.48 ± 0.13 at 0-mo, and slightly lower, ranging between 0.15 ± 0.07 and 0.33 ± 0.13 at 4-mo. Estimated maternal heritabilities were low to moderate, ranging between 0.08 ± 0.07 and 0.33 ± 0.07 at 0-mo and 0.13 ± 0.06 to 0.33 ± 0.06 at 4-mo. The direct genetic correlations between 0-mo and 4-mo were moderate to highly positive, ranging from 0.53 ± 0.23 to 0.96 ± 0.09. The estimated direct genetic correlation of chest width with other width traits was low and positive at both ages, whereas with hip width it was high and positive (0.80 ± 0.09) at 0-mo, suggesting that simultaneous improvement of body width of the front and back parts is possible. Maternal genetic effects were relatively independent of direct genetic effects for body measurement traits and can be considered in genetic evaluation.

Genotype and environmental interaction in growth and milk yield traits of indigenous Red Chittagong cattle

The present study was conducted to reveal the G×E interaction in growth and milk yield traits of indigenous Red Chittagong cattle reared in two production environments. Traits included: birth weight (BW), weaning weight (WW), average daily gain (ADG), daily milk yield (DMY), lactation length (LL) and lactation yield (LY). Data accumulated on a total of 161 animals during 2005 to 2012 in growth traits and 76 animals during 2005 to 2008 in milk yield traits. The heritability of BW, WW and ADG were 0.47±0.04, 0.49±0.17, 0.49±0.16 respectively and the heritability of DMY, LL, LY were 0.47± 0.07, 0.47±0.06 and 0.47±0.08, respectively. The effect of genotype x environment interaction was non-significant (p>0.05) on BW, WW and ADG whereas its effect was highly significant (p<0.001)on DMY, LL and LY. Correlations (genetic) between the breeding values of BW, WW and ADG in two production environment were 0.19, 0.13 and 0.11, respectively and correlations (genetic) between breeding values of DMY, LL and LY were 0.07, 0.18 and -0.01, respectively. The said genetic correlation values represented the degree of genotype by environment interaction arising on the RCC in the said two production environments.Traits with positive genetic correlation values indicate their acceptability (no difference) where as traits with negative correlation values indicate that RCC parents should be selected and used separately in two production environments.