Factors affecting first semen collection traits of Kankrej cattle bull

Introduction

Dairy animals' genetic improvement can be achieved by the best tools like artificial insemination. Improvement programme in the form genetics of dairy animal requires genetically superior male for semen collection and to inseminate that semen in large number of females through artificial insemination can only get proper response and improvement. Many limitations and reduces genetic gain per generation was reported by the use of natural mating over the artificial insemination. Intensive systemic and multistage selection is prime requirement of any semen station, institutional and commercial herd to get genetically superior bull. Breeding soundness of breeding bull should be evaluated by certain vigorous parameters like optimum serving capacity and profile of semen production traits. To get proper and lifelong semen production performance from extremely cherished breeding bull, it is obligatory to keep on suitable managemental circumstances. Species and breed of dairy animals should have substantial effect on male reproductive parameters specifically related to semen production which was also reported scientifically. Very fewer scientific reports are associated to first time semen collection traits and performance of Kankrej cattle bull from initiation to retention in semen production system. Effect of genetic composition was well recognised and described for production traits in dairy animals; however, effect of genetic and non-genetic factors on reproduction traits are not attainment much position in Indian circumstance due to need frozen semen doses are more and supply is scanty which hindered assessment system at some degree till date. Semen production traits like semen volume, sperm concentration and motility like parameters were studied by scientists but studies are very scanty when it comes to first time semen collection traits and factors disturbing them. When financial side of breeding bull is under deliberation, first time semen collection traits are very imperative. It is also essential while breeding bull found as recognised and progeny of the best dam and recognized bull will be desired in forthcoming semen collection of semen station. To form scientifically coped semen station, it is key requisite to identify about and designate the induction age bull of specific breed for good semen production. Body weight and scrotal circumference are the essential and conjoint parameters must to be used to evaluate breeding soundness of bull. Pedigree records along with individuals' body weight and scrotal circumference as well as age at first semen collection show vigorous role in early age selection of breeding bull for optimal semen production. Moreover, now a day age, body weight and scrotal circumference of bull has been assimilated by semen stations in the reviewed physical examination at the time assortment of young breeding bull due to its durable correlation with sperm production. Looking to this background information the present hypothesis was made to evaluate effect of season and period of birth of bull on age, body weight and scrotal circumference of bull at first semen collection in Kankrej cattle bulls.

Materials and Methods

Evaluation of first time semen collection traits were carried out on Kankrej cattle bulls of Dama Semen Production Unit (DSPU), Dama. Information on breed characteristics is available on the national portal of the NBAGR website (National Bureau of Animal Genetic Resources 2021). Data pertaining to date of birth, date of the first semen collection of the bull, date of last semen collection and number of semen doses produce from each ejaculate are available with semen stations as databases which were utilized for the present study with permission of the semen stations. Details of period of data and number of bulls utilized for the present study is given following table. The bulls were maintained under proper housing, feeding, management and health care. The young bulls were trained for semen collection using artificial vagina. The semen was collected twice a week from individual bull and ejaculates were obtained with an interval of 15 -30 minutes. The nutrition requirement is standardized, so bulls are fed adlibidum chaffed green and dry fodder mixture as per seasonal availability, concentrate mixture as per requirement based on body weight with area specific mineral mixture. Body weight of bull at first semen collection, scrotal circumference of bull at first semen collection and age of bull at first semen collection were considered to study the effects of season of birth and period of birth.

Average monthly high and low temperature at DSPU, Dama during the period of study

Body weight of bull was measured using digital weighing balance by the semen station for each bull at regular time interval of a month. Body weight (kg) of the bull in the month of first semen collection was used for the present study. Scrotal circumference was measured at the semen stations by pushing testicles firmly into the bottom of the scrotum by placing the thumb and fingers laterally on the side of the neck of the scrotum and pushed ventrally then a flexible metal measure tape was formed into a loop and slipped over the scrotum around its greatest diameter to measure scrotal circumference in centimetres. This scrotal circumference (cm) for each bull was measured by the semen stations every month were collected for the present study. Data recorded by the semen stations regarding date of birth and date of first semen collection of the bulls were used to estimate age of bull at first semen collection (days) for the present study. Kankrej bulls were grouped as per seasons considering birth of bull as winter (November to February), summer (March to June) and monsoon (July to October). Data collected for Kankrej bulls from semen stations were grouped as per year in which particular bull was born.

Coding of season of birth

Considering the fact that the every two year environmental condition show change and accordingly the managemental practises were changing over the particular period, which affect the semen production traits under study.

Coding of period of birth

Statistical Analysis

The effects of season of birth and period of birth on body weight, scrotal circumference and age of bull at first semen collection were studied by multivariate analysis under general linear model and restricted maximum likelihood (REML) method considering all factors listed above have fixed effect. The data were analysed using SAS software version 9.3 and PROC GLM as base command SAS (2011). The differences between the least squares means for sub classes under a particular effect were tested by Scheffe test Scheffe (1959) to check the significance. The high heterogeneous variances between the subclasses, unequal group size, pairwise and unpairwise comparison lead to use of Scheffe test as other tests find differences between the least squares subclass means. Scheffe test is one of the best adjustments that can used to decrease experiment wise error rates when testing multiple comparisons. Scheffe test is a very conservative adjustment that why it is the safest method for data with sub classes. The F-ratio used in the calculation is unique in that the mean square (MS) for only two groups being compared is used in the numerator and the MS for all respective comparison is used in the denominator. This means that each pairwise comparison has to have the same significance as the variance for all comparisons when using Scheffe test.

Where, TS = Test of significance Fs = F for scheffe X i = Mean of i th group X j = Mean of j th group S w = Within group variance n i = Total number of observation of i th group n j = Total number of observation of j th group Present model was design to estimate least squares means (LSMs) of first time semen collection traits under present study for fixed effects of factors i.e. season and period of birth.

Y ijx = μ + S i + T j + e ijx

Where, Y ijx = Semen production trait of x th individual observation belonging to i th season of birth, j th period of birth μ = Overall mean S i = Effect of i th season of birth (i = 1 to 3) T j = Effect of j th period of birth (j = 1, 2, 4, 5 and 6*) e ijx = Residual random error, NID (0 and σ 2 e ) *Period-6 for effect on age of bull at first semen collection only

Results and Discussion

The LSMs of body weight, scrotal circumference and age of bull at first semen collection with the fixed effect of nongenetic factors such as season of birth and period of birth are given in Table -1. General linear model was used for analysis of body weight, scrotal circumference and age of bull at first semen collection. The least squares analysis of variance for the factors affecting these traits are given in Table-2. Numbers of observations for this analysis were comparatively low hence, standard errors are higher.

Body weight of bull at first semen collection

The verall LSM for body weight of bull at first semen collection was 537.69 ± 10.51 kg. Non-genetic factors like season of birth and period of birth contributed nonsignificantly (P>0.05) for variation in body weight of bull at first semen collection. The overall LSM for body weight of bull at first semen collection was higher as compare to 360 and 284.7 kg reported by Sethi et al. (1989) [7] in Karan Fries cattle and Siddiqui et al. (2007) [8] in crossbred cattle respectively. Body weight of bulls at first semen collection were found to be 572.04 ± 34.35, 580.00 ± 23.78 and 584.00 ± 45.54 kg in winter, summer and monsoon born bulls respectively. In accordance to the present study, Naha et al. (2019) [5] reported non-significant effect of season of birth on body weight of bull at first semen collection. Bulls born during 2006 to 2016 were taken in to consideration for the present study. Based on the different periods of birth, body weight of bull at first semen collection ranged from 481.68 ± 59.89 to 692.68 ± 59.89 kg.

Scrotal circumference of bull at first semen collection

The overall LSM for scrotal circumference of bull at first semen collection was 30.86 ± 1.60 cm. Effect of non-genetic factors like season of birth and period of birth were nonsignificant (P>0.05) on scrotal circumference of bull at first semen collection. The overall LSM for scrotal circumference of bull at first semen collection was higher as compared to 28.20 cm reported by Siddiqui et al. (2007) [8] in Crossbred cattle. Bulls born during winter, summer and monsoon seasons has 28.59 ± 2.18, 34.00 ± 1.51 and 30.00 ± 2.89 cm mean scrotal circumference at first semen collection. Scrotal circumference of bull at first semen collection ranged from 23.86 ± 3.80 to 36.86 ± 3.80 cm during the different periods of birth.

Age of Bull at First Semen Collection

The overall LSM for age of bull at first semen collection was 1122.36 ± 86.9 days. Non-genetic factors like season of birth and period of birth contributed non-significantly (P>0.05) to the variation in age of bull at first semen collection. Naha et al. (2015) [4] and Naha et al. (2019) [5] reported higher age of bull at first semen collection of 3.17 and 3.14 years as compared to present study in Sahiwal cattle. Contrary to present finding, lower age of bull at first semen collection were found in the reported values of 20.5 months in HF X Zebu (Siddiqui et al., 2008) [9] , 923 days in F1 Friesian X Tharparkar, 916 days in 50% HF X Tharparkar and 937 days in 75% HF X Tharparkar (Chauhan et al., 2010) [1] , 872.06 days in Karan Fries (Mukhopadhyay et al., 2010) [3] , 908.1 days in HF crossbred (Khatun et al., 2013) [2] , 738.39 days in HF Crossbred (Vijetha et al., 2014) [10] , 1111.37 days in Tharparkar, 810.84 days in 50% Friesian X Tharparkar, 798.41 days in 75% Friesian X Tharparkar and 796.21 days in F1 Friesian X Tharparkar (Panmei et al., 2016) [6] . Age of bull at first semen collection were 1233.17 ± 120.30, 1036.69 ± 94.16 and 1097.22 ± 129.95 days for winter, summer and monsoon born bulls however the differences between them was non-significant. Similarly Chauhan et al. (2010) [1] , Mukhopadhyay et al. (2010) [3] , Khatun et al. (2013) [2] and Panmei et al. (2016) [6] reported non-significant effect of season of birth on age of bull at first semen collection. Based on the different periods of birth, age of bull at first semen collection ranged from 910.16 ± 181.66 to 1298.05 ± 85.02 days. Effect of period of birth of bull was also found non-significant (P>0.05) on age of bull at first semen collection in the present study. Contrarily, Significant effect of period of birth on age of bull at first semen collection was reported by Chauhan et al. (2010) [1] , Mukhopadhyay et al. (2010) [3] , Khatun et al. (2013) [2] and Panmei et al. (2016) [6] .

Conclusion

Effect of season as well as period of birth of bull was non-significant on first time collection of semen doses from Kankrej bull. Non-significant effect of season and period of birth reflects that the semen station scientific management system was working well and providing animal good comfort for production of semen. From this study, it is also noticed that Kankrej breed of cattle is well adjusted with local environment and capable of sustain in such harsh environment.

References

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