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pendent and dependent ones The indirect effect is the ef fect of an independent variable on a dependent variable through one or more intervening or mediating variables The Bunaji White Fulani cattle are the most numer ous of all Nigerian breeds of cattle being the principal milk producer in Nigeria accounting for over 90 of


AGRICULTURA TROPICA ET SUBTROPICA VOL 44 3 2011, milk yield of Bunaji cows using path analysis The results measuring cylinder and was later converted to the nearest. so obtained could be useful in the selection of animals for kilograms Heart girth was measured using a tape rule. better milk production The teats were measured using a thread which was read. off on a tape rule udder circumference was measured. using a tape rule while a graduated measuring stick was. MATERIALS AND METHODS used for the udder height measurements. Location of study and experimental animals Statistical analysis. Data were obtained from 267 randomly selected Bunaji Means standard deviations SD and coefficients. White Fulani cows The animals were selected in their of variation CV of weekly milk yield and linear type. breeding tracts in certain smallholder farms in Nasarawa traits were computed Pairwise correlations among milk. State north central Nigeria The State falls within the yield and morphometric characters were also determined. guinea savannah agro ecological zone and is found be Standardized partial regression coefficients called path. tween latitudes 7052 N and 8056 N and longitudes 7025 E coefficients beta weights were calculated This was to. and 9037 E respectively It has two distinct seasons The allow direct comparison of values to reflect the relative. wet season lasts from about the beginning of May and importance of independent variables to explain variation. ends in October The dry season is experienced between in the dependent variable The path coefficient from an. November and April Annual rainfall figures range from explanatory variable X to a response variable Y as de. 1100 to 2000 mm About ninety percent of the rains fall scribed by Mendes et al 2005 is shown below. between May and September the wettest months being PY Xi bi SXi. July and August Temperatures are generally high during SY. the day particularly in the months of March and April where. The mean monthly temperatures in the State range be PY Xi path coefficient from Xi to Y i HG FRTL FLTL. tween 20o and 34o with the hottest months being March RRTL RLTL UC UH. April and the coolest months being December January bi partial regression coefficient. Dense Forest are few and far apart and are found mainly SXi standard deviation of Xi. in lowland areas particularly where population pressure SY standard deviation of Y. is less on the land The animals were subjected to the tra The significance of each path coefficient in the multiple. ditional management grazing system linear regression model was tested by t statistic using the. following model,Traits measured tj bj j t n p 1 j 1 2 P. Milk yield MY and seven biometric traits were meas where. ured on each lactating animal weekly for six consecutive var bj the diagonal member of matrix s2 X X 1. months October 2008 March 2009 in the early to late s2 mean square of residual obtained from ANOVA. dry season period following standard procedure and ana. tomical reference points Mohd Eisa et al 2006 Canji The indirect effects of Xi on Y through Xj were calculated. et al 2008 Measurements were restricted to apparently as follows. healthy animals in their first second and third lactations IEYXi rXiXjPY Xj. respectively Information on the lactation stages of the where. animals was provided by the herdsmen Each animal IEYXi the direct effect of Xi via Xj on Y. was subsequently tagged for identification purpose The rXiXj correlation coefficient between ith and jth inde. body parts measured were heart girth HG fore right pendent variables. teat length FRTL fore left teat length FLTL rear right PY Xj path coefficient that indicates the direct effect of. teat length RRTL rear left teat length RLTL udder jth independent exogenous variable on the dependent. circumference UC and udder height UH measured endogenous variable. as the distance from the ground to the udder floor at the Coefficient of determination R2 was partitioned into its. points directly in front of the fore and rear teats The components using path analysis as follows. milking routine consisted of udder cleaning and manual R2 P2Y X1 P2Y X2 P2Y X3 P2Y X4 P2Y X5 P2Y X6 P2Y X7. pre stimulation Milking was done by hand twice a day 2rX1X2PY X1PY X2 2rX1X3PY X1PY X3 2rX1X4PY X1PY X4. in the morning 0600 0800hr and in the evening 1600 2rX1X5PY X1PY X5 2rX1X6PY X1PY X6 2rX1X7PY X1PY. 1800 hr respectively Milk yield was determined using a X7. 2rX2X3PY X2PY X3 2rX2X4PY X2PY X4 2rX2X5PY X2,AGRICULTURA TROPICA ET SUBTROPICA VOL 44 3 2011. PY X5 2rX2X6PY X2PY X6 2rX2X7PY X2PY X7 2rX3X yield kg heart girth fore right teat length fore left. 4 Y X3 Y X4, 2rX3X5PY X3PY X5 2rX3X6PY X3PY X6 teat length rear right teat length rear left teat length. 2rX3X7PY X3PY X7 2rX4X5PY X4PY X5 2rX4X6PY X4PY X6 udder circumference and udder height cm averaged. 2rX4X7PY X4PY X7 2rX5X6PY X5PY X6 2rX5X7PY X5PY 1 92 170 34 5 01 4 73 4 90 4 69 40 81 and 64 42. 2rX6X7PY X6PY X7 respectively The present value recorded for milk yield. where is comparable to the range 0 81 2 43 kg reported by. P2Y Xi direct effects of explanatory variables HG FRTL Ahamefule and Ibeawuchi 2008 for the same breed. FLTL RRTL RLTL UC UH in contributing to of cattle The variation in milk yield appeared greater. the variation of Y Milk yield than in any of the measurements and may be due to. 2r XiXj PY Xi PY Xj combined effects of explanatory the influence of the environment on this trait However. variables HG FRTL FLTL variations in the teat lengths and udder circumference. RRTL RLTL UC UH in contrib seemed similar,uting to the variation of Y Milk.
yield Pairwise correlations,SPSS 2001 statistical package was employed in the. analysis Phenotypic correlations between milk yield and type. traits are presented in Table 2 Milk yield had positive. and significant association with heart girth fore right teat. RESULTS AND DISCUSSION length fore left teat length rear right teat length rear left. teat length and udder circumference r 0 538 0 766, Milk yield and morphological traits P 0 01 However milk yield negatively correlated with. udder height r 0 420 P 0 01 The present results, The means standard deviations and coefficients of are consistent with the findings of Roy and Saha 2004. variation of weekly milk yield and conformation where heart girth had positive and significant correlation. traits of Bunaji cows are presented in Table 1 The milk with milk yield of cows In a related study Canji et al. 2008 reported significant association between heart. Table 1 Descriptive statistics of weekly milk yield kg girth and longevity of cows of Slovak Simmental breed. and conformation traits cm of Bunaji cows There are varying reports on the relationships between. udder traits and milk yield of various species and breeds. Traits Mean Standard deviation Coefficient of variation. MY 1 92 0 37 19 27 of livestock The present finding on the positive relation. HG 171 52 8 93 5 21 ship between teat length and milk yield agrees with the. FRTL 5 01 0 82 16 37 submission of Narian et al 1986 in goats Similarly. FLTL 4 73 0 80 16 91 Strapak et al 2005 reported that teat development posi. RRTL 4 90 0 79 16 12 tively correlated with longevity based on higher milk pro. RLTL 4 69 0 78 16 63 duction In contrast Wojcik and Czaja 2002 and Weiss. UC 40 81 6 77 16 59 et al 2004 reported low and significant negative cor. UH 64 42 7 62 11 83 relations between teat length and milk yield of cows In. MY milk yield HG heart girth FRTL fore right teat their paper Mohd Eisa et al 2006 found non significant. length FLTL fore left teat length RRTL rear right positive and negative correlations between the two traits. teat length RLTL rear left teat length UC udder in the different breeds of She Camel investigated These. circumference and UH udder height observed discrepancies could however be attributed to. Table 2 Pearson s coefficients of correlation between milk yield and conformation traits of Bunaji cows. Traits MY HG FRTL FLTL RRTL RLTL UC UH,MY 0 538 0 721 0 726 0 689 0 709 0 766 0 420. HG 0 605 0 575 0 578 0 545 0 564 0 161,FRTL 0 940 0 899 0 915 0 829 0 204.
FLTL 0 902 0 963 0 831 0 245,RRTL 0 931 0 786 0 170. RLTL 0 815 0 202, Significant at P 0 01 for all correlation coefficients. AGRICULTURA TROPICA ET SUBTROPICA VOL 44 3 2011, Table 3 Direct and indirect effects of conformation traits on milk yield of Bunaji cows. Traits Correlation coefficient Direct Indirect effect. with milk yield effect,HG FRTL FLTL RRTL RLTL UC UH Total. HG 0 538 0 100 0 067 0 014 0 042 0 051 0 251 0 041 0 438. FRTL 0 721 0 112 0 061 0 023 0 064 0 085 0 370 0 052 0 609. FLTL 0 726 0 024 0 058 0 104 0 065 0 090 0 371 0 062 0 750. RRTL 0 689 0 072 0 058 0 101 0 022 0 088 0 351 0 043 0 619. RLTL 0 709 0 094 0 055 0 102 0 023 0 067 0 363 0 051 0 615. UC 0 766 0 446 0 056 0 093 0 020 0 057 0 076 0 058 0 320. UH 0 420 0 254 0 016 0 023 0 006 0 012 0 019 0 102 0 166. Table 4 Direct and combined effects of the independent of milk produced increased The negative correlation re. variables contributing to the variation of milk yield of corded for udder height and milk yield is consistent with. Bunaji cows documented evidence in literature Keskin et al 2005. Traits Coefficient Mohd Eisa et al 2006 indicating that the closer the ud. of determination R2 der to the ground the higher the milk production. Direct effects, P2Y X1 0 010 Path coefficients of explanatory variables.
P2Y X2 0 013, P2Y X3 0 001 Path coefficients of the explanatory variables are pre. P2Y X4 0 005 sented in Table 3 Path analysis provides a basis to meas. P2Y X5 0 009 ure direct and indirect effects of exogenous predictor. P2Y X6 0 199, variables on the endogenous response variable Here. P2Y X7 0 065, the correlation coefficient is partitioned into its compo. Combined effects, X 1 HG and X 2 FRTL 0 014 nents One component is the path coefficient or stand. X 1 HG and X 3 FLTL 0 003 ardized partial regression coefficient that measures the. X 1 HG and X 4 RRTL 0 008 direct effect of a predictor variable upon its response. X 1 HG and X 5 RLTL 0 010 variable The other component is the indirect effect s. X 1 HG and X 6 UC 0 050 of a predictor variable on the response variable through. X 1 HG and X 7 UH 0 008 other predictor variables, X 2 FRTL and X 3 FLTL 0 005 Estimated correlation coefficient at phenotypic level.
X 2 FRTL and X 4 RRTL 0 014 between heart girth and milk yield was 0 538 Its direct. X 2 FRTL and X 5 RLTL 0 019 effect on milk yield path coefficient 0 100 though. X 2 FRTL and X 6 UC 0 083 low was however significant Strong positive correla. X 2 FRTL and X 7 UH 0 016, tion was found between fore right teat length FRTL and. X 3 FLTL and X 4 RRTL 0 003, milk yield 0 721 However the direct effect of FRTL. X 3 FLTL and X 5 RLTL 0 004, X 3 FLTL and X 6 UC 0 018 on milk yield was low 0 142 and non significant It was. X 3 FLTL and X 7 UH 0 003 realized indirectly via udder circumference Similar ob. X 4 RRTL and X 5 RLTL 0 013 servations were observed for rear right teat length and. X 4 RRTL and X 6 UC 0 050 rear left teat length path coefficient 0 104 and 0 048. X 4 RRTL and X 7 UH 0 006 respectively The direct effect of fore left teat length was. X 5 RLTL and X 6 UC 0 068 low negative and non significant 0 001 covered con. X 5 RLTL and X 7 UH 0 010 siderably by the indirect effect of udder circumference. X 6 UC and X 7 UH 0 052 The phenotypic correlation between udder circumference. Sum total 0 687 and milk yield was the strongest 0 766 This was equal. change in conformation in accordance with breed age ly manifested in its direct effect on milk yield which was. and stage of lactation of the animal found to be the greatest 0 446 The present finding is in. Result obtained on udder circumference is comparable consonance with the report of Keskin et al 2005 where. to that reported by Strapak et al 2005 in dairy cattle the direct effect of udder circumference on milk yield of. Kukovics et al 2006 also reported that udder size had Akkeci goats was highest This is an indication that ud. strong effect on milk yield of sheep According to these der circumference is an important trait to be considered. authors as the size of the udder increased the quantity while selecting cows for breeding purposes The relation. AGRICULTURA TROPICA ET SUBTROPICA VOL 44 3 2011, ship between udder height and milk yield was negative single contribution to the variation in milk yield How. 0 420 Its direct effect on milk yield was equally nega ever the direct effect of fore right teat length fore left. tive 0 254 but highly significant teat length rear right teat length and rear left teat length. were non significant as they were considerably realised. Coefficients of determination and establishment via udder circumference The optimum regression model. of a preliminary regression equation included forecast indices such as udder circumference. udder height and heart girth This equation could serve as. The direct and combined effects of linear type traits on a useful practical tool for livestock farmers and research. the variation of milk yield are presented in Table 4 Udder ers in the field for predicting milk yield and for selection. circumference had the highest direct contribution to the purposes. variation in milk yield R2 0 199 The sum of determi. nation coefficients of any independent variable and two. independent variables interaction in the present study REFERENCES. was d 0 687 According to path analysis principle the. sum of determination coefficients plus the determination Ahamefule F O Ibeawuchi J A 2008 Variations in. coefficient of error is 1 In this case the determination weekly milk yield and composition of Muturu N dama. coefficient of error was 1 d 0 313 The preliminary and White Fulani cows in early lactation Journal of. multiple regression equation was Animal and Veterinary Advances 7 469 474. Y 0 443 0 004HG 0 050FRTL 0 011FLTL Canji V Strapak P Strapakova E Juhas P 2008 Ef. 0 034RRTL 0 044RLTL 0 024UC 0 012UH fect of conformation traits on longevity of Slovak Sim. mental breeds Slovak Journal of Animal Science 41,Establishment of optimum regression model 83 90.
Dimov K 2001 Correlations between the morphologi, The path coefficients of fore right teat length fore left cal and functional traits of the udder in Buffalo cows. teat length rear right teat length and rear left teat length from Bulgarian Murrah Bulgarian Journal of Agricul. were all statistically non significant as revealed by the tural Science 7 185 192. t test Thus they were expunged from the regression Heins B J Hansen L B Seykora A J Johnson D G. model to obtain a much more simplified equation This Linn J G Romano J E Hazel A R 2008 Crossbreds. necessitated the recalculation of the path coefficients of Jersey x Holstein compared with pure Holsteins for. for heart girth udder circumference and udder height production fertility and body and udder measurements. which were earlier found to be significant Estimates during first lactation Journal of Dairy Science 91. obtained for HG UC and UH were 0 144 0 626 and 1270 1278. 0 254 respectively and were found to be highly sig Jeonghoon A 2002 Beyond single equation regression. nificant P 0 01 The direct effects of heart girth ud analysis Path analysis and multi stage regression anal. der circumference and udder height in contributing to ysis American Journal of Pharmaceutical Education. the variation in milk yield were R2 0 021 0 392 and 66 37 42. 0 065 for HG UC and UH respectively The combined Keskin S Kor A Karaca S Lu H M 2005 A study. effects gave R2 value of 0 187 The optimum multiple of relationships between milk yield and some udder. regression model was traits by using of path analysis in Akkeci goats Journal. Y 0 292 0 006HG 0 034UC 0 012UH of Animal and Veterinary Advances 4 547 550. The sum of determination coefficient was 0 665 while Kukovics S Molnar A Abraham M Nemeth T Kom. the determination coefficient of error was 0 335 The losi I 2006 Effects of udder traits on the milk yield. present findings are consistent with earlier reports on the of sheep Archiv Tierzucht Dummerstorf 49 165 175. use of path analysis in modelling in dairy cows Naskar et Mendes M Karabayir A Pala A 2005 Path analysis. al 2004 and in goats Keskin et al 2005 of the relationship between various body measures and. live weight of American Bronze turkeys under three. different lighting programs Tarim Bilimleri Dergisi. CONCLUSIONS 11 184 188,Mohd Eisa M O Abu Nikhaila A M Majid A M. Path analysis revealed that udder circumference had 2006 The relationship between udder teats and milk. the highest significant direct effect on milk yield of Bu yield in She Camel Camelus dromedarius http www. naji cows followed by udder height and heart girth re sustech edu camel workshop papers Paper 204 doc. spectively Udder circumference also made the highest accessed November 2008. AGRICULTURA TROPICA ET SUBTROPICA VOL 44 3 2011, Narian S Prakash B Singh B 1986 Udder and teat of Karan fries cows Indian Journal of Dairy Science. dimensions of Jamunapari goats at different stages of 60 355 359. lactation Indian Journal of Dairy Science 39 325 SPSS 2001 Statistical Package for the Social Sciences. 327 SPSS Inc 444 Michigan Avenue Chicago IL 60611, Naskar S Banik S Tomar S S 2004 Path analysis of Strapak P Candrak J Aumann J 2005 Relationship. 305 days milk yield of Sahiwal cattle Indian Journal of between longevity and selected production reproduc. Dairy Science 57 365 366 tion and type traits Czech Journal of Animal Science. Perz W P Sabek Z Fl ak P 2008 Usefulness of re 50 1 6. gression models for 100 day milk yield estimation in Weiss D Weinfurtner M Bruckmaier R M 2004. dairy cows Slovak Journal of Animal Science 41 Teat anatomy and its relationship with quarter and ud. 126 132 der milk flow characteristics in dairy cows Journal of. Roy P K Saha R C 2003 Asssociation of certain body Dairy Science 87 3280 3289. measurements with some economic traits in Jersey Wojcik P Czaja H 2002 The relationship between ud. Tharparkar Red Sindhi crossbred cows Indian Journal der conformation and cow performance in three succes. of Dairy Science 56 380 340 sive lactations Annals of Animal Science 2 17 27. Rao T K S Dang A K Singh C 2007 Effect of udder Wright S 1934 The method of path coefficients An. and teat characteristics on milk composition and yield nals of Mathematical Statistics 5 161 215. Received for publication January 12 2011,Accepted for publication June 13 2011.
Corresponding author,Yakubu Abdulmojeed,Department of Animal Science. Faculty of Agriculture,Nasarawa State University,Keffi Shabu Lafia Campus. P M B 135 Lafia Nigeria,e mail abdul mojeedy yahoo com.

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