The objectives of this study were to determine the effects of season, year of calving and parity on lactation period, calving interval, number of days open and dry period in Egyptian buffalo, and to estimate genetic and phenotypic parameters for these traits using a multi-trait animal model. Season of calving, year of calving and parity affected the traits studied. Heritability estimates for lactation period, calving interval, dry period and number of days open were 0.09, 0.07, 0.13 and 0.08 respectively and repeatability estimates were 0.27, 0.14, 0.27 and 0.19 respectively. Estimates of the permanent environmental component (c2) were low. Genetic correlations between these traits were low and positive, except for that between lactation period and dry period, which was negative. A similar pattern was observed for phenotypic correlations, but these were higher than those observed for genetic correlations.  South African Journal of Animal Science, Vol 31, Issue 3, Oct – Dec (2001) pp.195-199 Key Words Buffalo, Calving interval, Days open, Dry period, Heritabilit

Aziz, M.A.

El-Chafie, O.M.

Jordaan, G.F.

Mahdy, A.T.

Schoeman, S.J.

English

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South African Journal of Animal Science 2001, 31(3)© South African Society of Animal ScienceThe South African Journal of Animal Science is available online at http://www.sasas.co.za/Sajas.html195Genetic and phenotypic variation of some reproductive traits in EgyptianbuffaloM.A. Aziz1, S.J. Schoeman2#, G.F. Jordaan2, O.M. El-Chafie3 and A.T. Mahdy11Department of Animal Production, Faculty of Agriculture, Alexandria University, Alexandria, Egypt; 2 Department ofAnimal Science, University of Stellenbosch, South Africa; 3 Animal Research Institute, Ministry of Agriculture, Cairo,EgyptAbstractThe objectives of this study were to determine the effects of season, year of calving and parity onlactation period, calving interval, number of days open and dry period in Egyptian buffalo, and to estimategenetic and phenotypic parameters for these traits using a multi-trait animal model. Season of calving, yearof calving and parity affected the traits studied. Heritability estimates for lactation period, calving interval,dry period and number of days open were 0.09, 0.07, 0.13 and 0.08 respectively and repeatability estimateswere 0.27, 0.14, 0.27 and 0.19 respectively.  Estimates of the permanent environmental component (c2) werelow. Genetic correlations between these traits were low and positive, except for that between lactation periodand dry period, which was negative.  A similar pattern was observed for phenotypic correlations, but thesewere higher than those observed for genetic correlations.Keywords:  Buffalo, calving interval, days open, dry period, heritability.#Author to whom correspondence should be addressed; e-mail: sjsc@maties.sun.ac.zaIntroductionShort lactation periods, long calving intervals, long dry periods and a large number of days open arecharacteristics typical of buffalo cows.  These traits have low heritabilities, and means are associated with alarge degree of variation due to numerous environmental factors (Mourad, et al., 1989; Parakash, et al.,1989; Khalil, et al., 1991; Afifi, et al., 1992; Ibrahim, 1998; Khan & Akhtar, 1998; Penchev, 1998; Suhail, etal., 1998; Tiwana & Dhillon, 1998; Vasconcellos & Tonhati, 1998; Tonhati et al., 2000). A soundknowledge of the source of this variation is essential for the application of sound breeding and managementpractices.  The objectives of this study were to determine the effects of some environmental factors onlactation period, calving interval, dry period and number of days open, and to estimate heritabilities,repeatabilities and genetic and phenotypic correlation coefficients between the above-mentioned traits.Materials and MethodsData for this study were obtained from a herd belonging to the Animal Production Research Instituteof the Egyptian Ministry of Agriculture located in Mehallet Mousa, Kafr El-Sheikh Governorate. A total of2505 records were collected between 1979 and 1992.  Animals were fed Egyptian clover ad libitum fromOctober to May and were supplemented with a concentrate mixture according to milk production. From Juneto September, animals were given a concentrate mixture with wheat or rice straw and a limited amount ofhay when available.  Heifers were bred for the first time at 24 months of age and the average age of cowswas 6.3 years. Cows were usually served two months after calving by natural mating to sires that werechosen at random.The data set was edited to exclude missing values. Records with missing parent identification datawere included in the analysis. The editing procedure reduced the size of the data set to 1589 records,representing the performance of 544 cows and 87 sires.  Data were classified according to cow, sire, dam,year of calving, season of calving and parity.  Year was divided into two seasons, viz. winter (October toMarch) and summer (April to September). The traits studied were lactation period, calving interval (d), dryperiod (d), and number of days open.   The number of days open was calculated as the difference betweenthe interval between two consecutive calvings and a constant gestation period (318 days).  Paritiesnumbering eight or more were classified together.South African Journal of Animal Science 2001, 31(3)© South African Society of Animal ScienceThe South African Journal of Animal Science is available online at http://www.sasas.co.za/Sajas.html196Data were analysed by least squares analysis with unequal subclass numbers using the PROC GLMprocedure of SAS (1990).  The model used was :Yijkl=µ+p i+sj+yk+eijklwhere: Yijkl   =  the vector of observationsµ       =  the overall mean,pi       =  the effect of the ith parity,sj       =  the effect of the jth season of calving,yk      = the effect of the kth year of calving,  eijkl    is the error term, assumed to be randomly and independently distributed with a meanequal to 0 and variance equal to σ2e.All factors in the model except the error term were assumed to be fixed.  Differences between meanswere evaluated using the Duncan Multiple Range Test (Steel & Torrie, 1980).  Subsequently, a multitraitrepeatability animal model was fitted using the VCE 4.2.5 package of Groeneveld (1994, 1997) andGroeneveld &  Garcia Cortés (1998).  The model previously assumed was fitted to the same data with theinclusion of additive genetic and permanent environment as additional random effects.  Repeatabilityestimates were obtained from the equation:t = (σ2a + σ2c)/σ2pwhere σ2a = additive genetic varianceσ2c = permanent environmental varianceσ2p = total phenotypic varianceNo asymptotic standard errors were computed for the genetic parameters.Results and DiscussionMean squares for factors affecting lactation period, calving interval, dry period and number of daysopen are presented in Table 1.  Parity, season of calving and year of calving had an effect (P ≤ 0.01) on thetraits studied.Table 1  Mean squares of factors affecting lactation period, calving interval, dry period and number of daysopen in Egyptian buffaloMean SquareSource of variation dfLactation period Calving Interval Dry PeriodNumber of DaysopenParitySeason of calvingYear of calvingError71131567390513.86**8218.2475905.91**11682.58173217.10**240785.69**75876.77**12312.38947830.00**151093.43**51246.65**17152.11173217.10**240785.69**75876.77**12312.38R2 (%) 15 16 26 16**P < 0.01Regression equations of the four traits on parity number are presented in Table 2, while least squaresmeans for the four traits classified by season of calving and year of calving are shown in Table 3.  Lactationperiod was the shortest for the first parity and did not differ (P > 0.05) between the other parities.Table 2  Regressions of least squares means for lactation period, calving interval, dry period and number ofdays open (Y) on parity number (X)Trait Mean (d) CV (%) Regression R2Lactation periodCalving intervalDry periodNumber of days open208.6518.9307.3199.551.727.051.368.1Y = 128.9 + 37.9X - 3.34X2Y = 599.6 – 40.6X + 2.92X2Y = 469.9 – 78.2X + 6.22X2Y = 218.6 – 40.6X + 2.92X20.710.940.920.94South African Journal of Animal Science 2001, 31(3)© South African Society of Animal ScienceThe South African Journal of Animal Science is available online at http://www.sasas.co.za/Sajas.html197All traits were characterized by large coefficients of variation. The highest least squares mean forcalving interval was recorded between the first and second parities and the lowest for the fifth parity.  Thisdiffered (P ≤ 0.05) from the means of other parities.Season of calving did not have any effect on lactation period (P > 0.05), but cows that calved inwinter had longer calving intervals, longer dry periods and a greater number of days open than those thatcalved in summer (P < 0.01). No trend was evident for least squares means over years of calving for any ofthe traits studied.  However, means for lactation period decreased from a maximum in 1979 to a minimum in1984, after which they fluctuated between years. The longest calving interval and the greatest number ofdays open occurred in 1980.  The shortest calving interval and the lowest number of days open occurred in1992.  The longest dry period was in 1985 and the shortest dry period was in 1979. The results of this studyare in agreement with the findings of Mourad et al. (1989), Shah (1990), Khalil et al. (1991), Ibrahim (1998)and Vasconcellos & Tonhati (1998) for different breeds of water buffalo.  These workers reported that yearof calving and parity had significant effects on lactation period, calving interval, dry period and number ofdays open.  However, Afifi et al. (1992) reported that year of calving had no effect on calving interval in theEgyptian buffalo, although it affected the number of days open.  In contrast Parakash et al. (1989) observedno effect of year of calving on calving interval, dry period and number of days open for Murrah buffalo.  Theresults of this study are in agreement with those of Mourad et al. (1989), Parakash et al. (1989), Khalil et al.(1991), Afifi et al. (1992) and Ibrahim (1998) who found that calving interval decreased with parity.  Theirresults also indicated that least squares means of year of calving fluctuated considerably over years.Vasconcellos & Tonhati (1998) did not detect any distinct pattern for lactation period with year of calving orage in Murrah buffalo and attributed their results to the effect of herd management. On the other hand, theyfound that means for calving interval were homogenous across years studied.Table 3  Least square means (± s.e.) for the effects of season of calving and year of calving on lactationperiod, calving interval, dry period and number of days openLactation period Calving interval Dry periodNumber ofDays openSeason of calvingWinterSummerYear of calving19791980198119821983198419851986198719881989199019911992228.72±5.23a224.08±4.98 a314.42±25.62a299.14±13.72abc255.10±14.09abc227.33±11.22abcd204.62±9.08d190.11±8.98cd192.63±11.57abcd218.72±11.37ab193.94±10.94abcd216.28±9.84abc205.50±9.22abcd222.57±8.97ab224.35±8.59ab204.89±14.30bcd508.73±5.37a483.59±5.11b512.23±28.30b584.11±14.08a494.57±14.46bc486.03±11.52cd483.88±9.32cde502.61±9.22cd488.23±11.89cde510.56±11.67cd461.11±11.23fg480.72±10.10ef497.39±9.46def508.20±9.21def495.51±8.82def440.92±14.68g279.66±6.34a259.75±6.03b198.40±31.04bc285.40±16.62a239.68±17.07bcd258.87±13.60bc277.40±11.00b312.44±10.69b295.58±14.03bcde291.82±13.77cdef267.16±13.25ef284.45±11.92f291.81±11.17def285.64±10.87ef271.14±10.41f236.04±17.33f190.73±5.37a165.59±5.11b194.24±26.30b266.11±14.08a176.57±14.46bc168.03±11.51cd165.88±9.32cde184.61±9.22cd170.23±11.69cde192.65±11.67cd143.11±11.23fg162.72±10.10def179.39±9.46def190.20±9.21def177.51±8.82def122.92±14.68ga-g Column means without common superscripts differ (P < 0.05)Heritabilities, repeatabilities, genetic correlations and phenotypic correlations are presented in Table4.  Heritability estimates were low, and the highest heritability was 0.13 which was recorded for dry period.The only noteworthy repeatability estimates were those for lactation period and dry period (0.27). Geneticcorrelations between traits were positive, with the exception of that between lactation period and dry period.Phenotypic correlations were of medium magnitude and were greater than genetic correlations.  Allcoefficients were positive, except that between lactation period and dry period.  The highest correlation wasbetween calving interval and number of days open (0.90).South African Journal of Animal Science 2001, 31(3)© South African Society of Animal ScienceThe South African Journal of Animal Science is available online at http://www.sasas.co.za/Sajas.html198The heritability estimates obtained in this study are in agreement with those reported by Mourad etal. (1989), Parakash et al. (1989), Khalil et al. (1991), Afifi et al. (1992), Penchev (1998), Tiwana & Dhillon(1998) and Tonhati et al. (2000) for different breeds of buffaloes.  They also reported low heritabilityestimates for lactation period, calving interval, dry period and number of days open. Genetic correlationestimates reported by these authors are also in agreement with those obtained in this study.  However, theyreported positive genetic correlations between lactation period and dry period.Table 4 Heritabilities (bold) and repeatabilities (on the diagonal), genetic correlations (above the diagonal)and phenotypic correlations (below the diagonal), for lactation period, calving interval, dry period andnumber of days open in the Egyptian buffaloTrait Lactation period Calving interval Dry period Number of days openLactation periodCalving intervalDry periodNumber of daysopen0.090.270.47-0.370.470.090.070.140.490.90-0.290.220.130.270.470.070.300.210.080.19ConclusionsPoor reproductive efficiency was observed in the herd investigated in this study. The resultsindicated that the animals had short lactation periods, long calving intervals, long dry periods and a largenumber of days open. The very low heritability estimates coincided with low genetic correlations betweentraits and moderate phenotypic correlations.  The permanent environmental component and repeatabilitieswere also relatively low. It was concluded that the traits studied were mostly influenced by non-geneticfactors. There should be scope for reducing the length of the calving interval and days open in the currentherd by means of selection, efficient management regimes and proper feeding.AcknowledgementStudy leave of  M.A. Aziz was supported by a grant from UNESCO.ReferencesAfifi, E.A., Khalil, M.H., Bedeir, L.H. & Zeidan, S.M., 1992.  Genetic analysis of reproductive traits inEgyptian buffaloes.  Egypt. J. Anim. Prod., 29,  139-154.Groeneveld, E., 1994.  VCE- a multivariate, multimodel REML covariance component  estimation package.Proc. 5th World Congress Genet. Appl. Livest. Prod., 22, 47-50 (Guelph, Canada).Groeneveld, E., 1997.  VCE-4, User’s guide and reference manual.  Institute of Animal Husbandry andAnimal Behaviour, Mariensee, Germany.Groeneveld, E. & Garcia Cortés, A., 1998.  VCE 4.0, a (co)variance component package for frequentists andBayesians.  Proc 6th World Congress Genet. Appl. Livest. Prod., 27, 455-458 (Armidale,Australia).Ibrahim, S.A., 1998.  Analysis of non-genetic factors affecting calving interval and post-partum traits inEgyptian buffaloes.  Egypt. J. Anim. Prod. 35, 597-607.Khalil, M.H., Mourad, K.A., Mohamed, M.M. & Owen, J.B., 1991.  Genetic and phenotypic evaluation forreproductive performance of Egyptian buffaloes.  Anim. Prod. 52, 75-82.Khan, R.N. & Akhtar, S., 1998.  Production characteristics of Nili-Ravi buffaloes.  Asian-Australian J.Anim. Sci. 12,  56-60.Mourad, Kawthar A., Khattab, A.S. & Ibrahim, M.A.R., 1989.  Effect of genetic and non-genetic factors onreproductive traits in Egyptian buffaloes.  Buffalo Bulletin 8, 9-16.South African Journal of Animal Science 2001, 31(3)© South African Society of Animal ScienceThe South African Journal of Animal Science is available online at http://www.sasas.co.za/Sajas.html199Parakash, A., Tripathi, V.N. & Tomer, S.S., 1989.  Genetic analysis of reproductive traits of Murrahbuffaloes.  Indian J. Dairy Sci. 42,  426-430.Penchev, P, 1998.  Phenotypic and genotypic evaluation of the buffalo population bred in Bulgaria.Bulgarian J. Agric. Sci. 4, 463-469.SAS, 1990.  SAS User's Guide: Statistics.  1990 edition, Cary, NC, USA.Shah, N.H., 1990.  Prolonged  calving intervals in the Nili-Ravi buffalo.  Ph.D. dissertation, Faculty ofDiergeneeskunde, Utrecht, the Netherlands.Steel, R.G.D. & Torrie, J.H., 1980.  Principles and Procedures of Statistics.  Second edition, McGraw-HillBook Co., New York.Suhail, S.M., Syed, M. & Amjad, M., 1998.  Production and reproduction performance of Nili-Ravibuffaloes in N.W.F.P. Peshawar.  Sarhad J. Agric. 14, 403-406.Tiwana, M.S. & Dhillon, J.S., 1998.  Genetic improvement of buffalo productivity under farm and fieldconditions.  In Souveu.  Seminar on problems of buffalo reproduction and their solutions.  [editedby R.K. Sethi and S.K. Jindal].  October, 16, 1998.  Hisar, India.Tonhati, H., Vasconcellos, F.B. & Albuquerque, L.G., 2000.  Genetic aspects of productive and reproductivetraits in a Murrah buffalo herd in São Paulo, Brazil.  J. Anim. Breed. Genet. 117, 331-336.Vasconcellos, B.F. & Tonhati, H., 1998.  Inbreeding and its effects on some productive and reproductivetraits in a Murrah buffalo herd.  J. Anim. Breed. Genet. 115, 299-306.

Genetic and phenotypic variation of some reproductive traits in Egyptian buffalo

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Genetic and phenotypic variation of some reproductive traits in Egyptian buffalo

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