Abstract
Data on 3637 cows of seven genetic groups at three generations at Baghabarighat milk shed area, under Bangladesh Milk Producers' Co-operative Union Limited from 1991 to 2000 were analyzed. The genetic groups were Pabna Milking (PM) cows, 2PMX2 Sahiwal (PM×SL), 2PM×2Frisian (PMXFN), 2PMX2Australian Friesian Sahiwal (PMXAFS), 1/2Sahiwalx4PMX4 Friesian[SL(PMXFN)],1⁄2Friesian-4PM Sahiwal[FN(PM-SL)]and1/2Friesian/Sahiwal Jersey [FN(SL-JR)]. The aim of this study was to estimate phenotypic and genetic parameters for productive (birth weight, lactation length, lactation yield, fat% and SNF%) and reproductive (age at first service, service per conception, postpartum heat period and calving interval) traits. The highest birth weight of calves was obtained as 29.78 kg in 2PM×2 AFS, lactation yield as 2225.52 liters in FN(SL-JR), fat% as 4.48 in PMXSL and SNF% as 8.10 in FN(SL-JR). The longest lactation length was observed as 305.18 days in 2PM×2 AFS. The shortest age at first service was observed as 26.83 months in FN (PM-SL), postpartum heat period as 133.23 days in PM and calving interval as 414.90 days in PM. The lowest service per conception was found to be 1.22 in PM cows. In case of generation, the highest birth weight as 29.07 kg, lactation length as 291.01 days, lactation yield as 2269.56 liters, SNF as 8.12% and the lowest age at first service as 23.71 months, service per conception as 1.20, postpartum heat period as 119.80 days and calving interval as 390.40 days were found in third generation while the highest fat % as 4.41 was found in first generation. The heritability values were estimated as 0.27 for birth weight, 0.03 for lactation length, 0.45 for lactation yield, 0.37 for fat%, 0.46 for SNF%, 0.33 for age at first service; 0.001 for service per conception, 0.25 for postpartum heat period and 0.13 for calving interval. The genetic trends for the dairy traits were computed as average of breeding values using all data for cows born during 1991-2000. It was observed that the genetic trend of birth weight of calves increased in PMXSL, PM-FN, 2PM×2 AFS and FN(SL-JR) at the rate of 0.08, 0.10, 0.12 and 0.05 kg per year, respectively. The lactation yield of genetic group PM-FN, 2PM×2 AFS, SL(PMXFN) and FN (SL-JR) rose up at the rate of 6.78, 5.20, 4.14 and 5.19 liters per year, respectively. The genetic group of PM, PMXSL and PMXFN showed negative trend for fat % at the rate of 0.0005, 0.002 and 0.004% per year, respectively. But it increased in 2PM×2 AFS, SL(PMXFN), FN(PMSL) and FN(SL-JR) at the rate of 0.002, 0.013, 0.011 and 0.004% per year, respectively. The genetic trend of SNF% in only one group showed negative trend in PMXSL at the rate of 0.01 % per year. On the contrary, PM, PM-FN, 2PM×2 AFS, SL(PM×FN), FN(PM-SL) and FN (SLXJR) increased at the rate of 0.005, 0.010, 0.011, 0.0002, 0.014 and 0.003% per year, respectively. The high genetic variability of birth weight, lactation yield, fat% and SNF% indicated that there are good opportunities for genetic improvement of these traits in a selection scheme. Among 31, first 3 top sires No. 24 (FN), 14 (SL) and 20 (FN) for birth weight; Sire No.19 (FN), 36 (FN) and 23 (JR) for lactation yield; Sire No. 16 (SL), 11 (PM) and 26 (SL) for fat % and Sire No.14 (SL), 19 (FN) and 16 (SL) for SNF% were ranked on the basis of their predicted breeding values. From the results it is evident that the level of production of different crossbred cows was found to be higher but important reproductive traits were significantly better on PM. Thus it may be concluded that for long term sustainable development and conservation program for PM should be initiated along with that of crossbred in this particular study area.