Table 4.
Genetic parameters for heat tolerance in dairy cattle breeds reared in tropical countries.
| Region | Country | Dairy cattle breeds | Traits | Genetic model | Genetic parameters | Reference | ||
|---|---|---|---|---|---|---|---|---|
| Asia | Thailand | Holstein crossbreds | MY | Repeatability test-day model | Negative correlation for MY parameter between additive effects with and without HS across all three parities ranged between −0.21 and − 0.33. Negative correlation ranging from −0.45 to −0.56 was also detected between permanent environment effects. | Boonkum et al. (6) | ||
| MY | ssGREML, repeatability model, RRM | Genetic correlation between MY and heat tolerance ranged from −0.06 to 0.13 for old data and 0.16 to 0.30 for recent data. Heritability (h2) estimates for MY ranged from 0.33 to 0.40 (recent data) and 0.19 to 0.21 for old data. | Sungkhapreecha et al. (5) | |||||
| MY, SCS, FPR | ssGBLUP, BLUP | Additive genetic effects observed were 0.094, 0.035, and 0.001, respectively for MY, FPR, and SCS using BLUP method. They also found 0.015,005, and 0.001 for MY, FPR, and SCS when used ssGBLUP. The h2 estimates ranged from 0.334, 0.049, and 0.060 for MY, SCS, and FPR. | Sungkhapreecha et al. (23) | |||||
| Latin America | Brazil | Pure breed Gir | MY | RRM | A negative genetic correlation between general production level and specific ability to respond to HS was obtained (−0.23). A decline in additive genetic variance with rising THI values was observed for all DIM, especially between 40 to 200. A reduction in permanent environmental variance with increasing THI values was observed at any DIM. h2 estimates of up to 0.22 were obtained for lower THI values and DIM. h2 estimates of up to 0.29 were obtained for THI values <78 and DIM ˃ 290. | Santana et al. (43) | ||
| Holstein | MY | RRM | Lower estimates of additive genetic variance observed for THI ≥ 70 and DIM 75–170. Lower estimates for permanent environment effects were obtained for greater values of THI and lower DIM. Higher h2 estimates ranging from 0.18 to 0.30 were obtained at THI ≤ 54 and DIM≤60. The genetic correlation between THI ≤66 and DIM 70–200 was 0.80. | Santana et al. (77) | ||||
| Holstein | MY, F%, P%, SCS | Two-trait RRM | The h2 estimates were greater for lower THI thresholds and longer DIM while h2 estimates for SCS increased with rising THI values in the 2nd and 3rd lactation. Genetic correlations between MY and THI values (THI of 47 and 80) were 0.90, 0.76; and 0.63 while genetic correlation between F%, P% and THI was 0.80. | Santana et al. (78) | ||||
| Guzerá | MY | RRM | At THI value from 72–90, h2 estimates for TDMY ranged from 0.16 to 0.35 throughout lactation and THI values. | Santana et al. (44) | ||||
| Holstein | MY | RRM fitting LP, SP, and Wilmink function | The h2 estimates for TDMY regressed with THI values ranged between 0.15 to 0.21 and 0.07 to 0.22 when using LP and SP functions, respectively. | Negri et al. (67) | ||||
| MY | RRM | Combining THI and DTV showed a rise in reliability of EBVs of sires with less than 30 daughters and a 27% increase for sires with 10 daughters. | Negri et al. (79) | |||||
| SFA, UFA, MUFA, PUFA, C16:0, C18:0, C18:1 | Single-trait repeatability test-day models, RRM | Variations in h2 estimates between general and HS conditions increased from 0.03 to 0.06 for UFA parameters like unsaturated and monounsaturated. There was also a negative genetic correlation between general and HS additive genetic effects for saturated fatty acids ranging from −0.007 to −0.32. | Dauria et al. (4) | |||||
| MY, SCS, F%, P%, LP, CP, C16:0, C18:0, C18:1, SFA, UFA, MUFA, PUFA | Single trait animal model, RRM | The h2 estimate for milk production declined from 0.31 to 0.14, fat (0.28 to 0.16), protein (0.26 to 0.30), lactose (0.43 to 0.30), among other fatty acids profiles and continued to decline as THI increased from 51 to 78. Genetic correlation among breeding values at higher THI values was greater than 0.80 for all dairy cattle. | Carrara et al. (100) | Gir, Holstein, Gir x Holstein at F2 | RT | GWAS | h2 and repeatability estimates for RT were 0.13 ± 0.08 and 0.29 ± 0.06, respectively. | Otto et al. (101) |
| Sub-Saharan Africa | Tanzania | Mixed breed dairy cattle | MY | FRM with RRM on a function of THI | Additive genetic variance for MY along THI spectrum ranged from 9.83 to 7.52. Covariance between the intercept and slope for additive genetic effect ranged from −0.24 to −2.10. There was also a negative genetic correlation (−0.06 to −0.09) between MY and THI values. h2 estimates for MY ranged from 0.38 to 0.50. | Ekine-Dzivenu et al. (13) |
BLUP, best linear unbiased prediction; DIM, days in milk; DTV, diurnal temperature variation; EBVs, estimated breeding values; F%, fat percentage, P%, protein percentage; FRM, fixed regression models; FPR, fat to protein ratio; FP, percentage of fat; PP, protein percentage; LP, lactose percentage; CP, casein percentage; SFA, saturated fatty acids; UFA, unsaturated fatty acids; MUFA, monounsaturated fatty acids; PUFA, polyunsaturated fatty acids; C16:0, percentage of palmitic fatty acids; C18:0, percentage of stearic fatty acids; C18:1, percentage of oleic fatty acids; GWAS, genome-wide association studies; h2, heritability estimates; MY, milk yield; ssGBLUP, single-step genomic best linear unbiased prediction; ssGREML, single-step genomic restricted maximum likelihood; REML, restricted maximum likelihood; RRM, random regression models; LP, Legendre orthogonal polynomial functions; SP, Linear splines functions; RT, rectal temperature; SCS, somatic cell score; TDMY, test day milk yield; THI, temperature-humidity index.