EJACULATE PROPERTIES AND REPRODUCTIVE EFFICIENCY OF LARGE WHITE BOARS DURING EXPLOITATION

: The main objective of this study was to assess the variability of ejaculate properties: volume of ejaculate (VOL, ml), sperm concentration (CON, spermatozoa/ml), total sperm count (NT) and the number of doses produced (NPD) per ejaculate under the influence of season, boar and the interval between two mounts. Reproductive efficiency of boars was analysed based on the farrowing rate (FR). The study included 341 ejaculates from seven Large White boars. Impact assessment was carried out by applying the GLM procedure of the statistical package SAS 9.1.3. The average values of VOL, CON, NT, NPD and FR were: 244.28 ml, 203.77x10 6 spermatozoa/ml, 43.48x10 9 spermatozoa, 17.39 doses and 67.58%. Ejaculate properties varied under the influence of season (P<0.01, P<0.001). The interval between two mounts did not affect only the variability of CON. The difference between the best and worst boars was 91.99x10 6 spermatozoa/ml of ejaculate (P<0.001). During summer VOL ejaculate was the lowest (191.36 ml). The highest NPD (19.04 doses) was produced during the autumn months, and during the same period the highest concentration of sperm was recorded (242.16x10 6 spermatozoa/ml). Regardless of the differences in the farrowing rate between boars not being statistically significant (P=0.0882), it is necessary to perform the ranking and promptly identify boars with farrowing rate below average.


Introduction
Modern pig production is based on highly productive breeds with the use of modern technical and technological solutions and biotechnological methods in breeding and reproduction. The success of artificial insemination depends largely on quantitative and qualitative properties of the ejaculate.
In the populations of pigs where a continuous selection is conducted, there is a tendency for better exploitation of boars, good production performance, which is reflected in obtaining the greatest possible number of doses per ejaculate of optimal fertile capability (Savić et al., 2013a). The volume of ejaculate, sperm concentration and sperm motility are characteristics/properties which determine the number of doses per ejaculate, fertility of doses and the number of sows that can be inseminated.
Research by Young et al. (2010) shows that there are differences in farrowing rate between the 30 herds analyzed (54.7-92.4%), and the cause of such broad range is consequence of different procedures and technological operations carried out in herds. In the pig production, reproductive performance is assessed based on the farrowing rate, and the number of live born piglets, however, in the commercial sector boars of superior and inferior fertility are used (Flowers, 2013).
The aim of this study was to evaluate variability of ejaculate and reproductive efficiency of Large White boars during use in reproduction.

Material and Methods
The research was conducted on a reproduction farm, in the period from 2011 to 2012. Total of 341 ejaculates of 7 Large White boars were analyzed during two years of use in reproduction. In addition to the evaluation of ejaculate, also the reproductive efficiency boars was tested.
Sows were inseminated twice, and from a total of 919 matings, 602 farrowings were realized. Of the total number of analyzed ejaculates, 40 (11.73%) were unusable, so they were not evaluated. Reasons for ejaculates being considered unusable were different: dead sperm in the ejaculate, sperm motility subjectively estimated to be below 70%, the presence of impurities, etc.
Boars were housed in a separate facility, in boxes measuring 2×4 m, with partly slated concrete floor. The microclimate conditions in facility for boars were under automatic control. The animals were fed a balanced feed mixture, and fresh water was available to them ad libitum.
The impact of season was examined as the impact of a class: 1 (December, January, February), 2 (March, April, May), 3 (June, July, August) and 4 (September, October, November). The average interval between two mounts was 8.80 days. The research included: the volume of ejaculate (VOL, ml), sperm concentration (CON, x10 6 spermatozoa/ml), the total number of spermatozoa in the ejaculate (NT, x10 9 spermatozoa) and the number of doses produced (NPD). Reproductive efficiency of boars was investigated based on the farrowing rate (FR, %), which is calculated as the relative ratio between the number of farrowed sows in relation to the number of inseminated sows.
Taking of the ejaculate was performed using standard manual method, the introduction of mobile phantoms into boxes where boars are housed. The ejaculate volume was measured by graduated cylinder, with an accuracy of ±2 ml. The concentration of native sperm was evaluated by application of the photocolorimeter. Dosages for insemination were standardized to a volume of 100 ml and 2.5 billion spermatozoa per dose. The total number of spermatozoa in the ejaculate was obtained by multiplying the sperm concentration by the volume of ejaculate.
Impact assessment was carried out by applying the General Linear Model procedure of the statistical package SAS 9.1.3 (SAS Inst. Inc., 2002Inc., -2003, using the following model: where: y ijkanalysed property of the ejaculate, μ-general population average, B ithe impact of boar (i=1,2,3,4,5,6,7), S j -the impact of season (j=1,2,3,4), b(x ijk -)linear regression impact of the interval between two consecutive mounts and e ijkrandom error.
The boars were ranked based on the value of the farrowing rate, by forming two groups of boars (with the farrowing rate above and below the general average). Comparison of Least Square Means (LSMeans) values of ejaculate properties and mean values of the farrowing rate was performed by t-test.

Results and Discussion
The basic statistical parameters are shown in Table 1. With regard to the values of the standard deviation, the ejaculate volume and sperm concentration exhibit a greatest variation with respect to other fertility traits. The influence of studied factors on the variability of the ejaculate properties is presented in Table 2. All the analysed properties of ejaculate varied under the influence of the season. In addition to micro-climate indicators, the impact of the season should be viewed through the duration of the photoperiod during the year, and expressed significance of the influences indicates to the need and obligation to include this factor in the models in the analysis of properties of ejaculate.
The results of this study are contrary to the study of Savić et al. (2013b) in which the ejaculate volume varied under the influence of boars, while the influence of the interval between two mounts was not significant. The effect of season on ejaculate properties identified in our study is in concordance with the findings of  Interval between two consecutive mounts Volume of ejaculate (ml) ns *** *** Concentration of sperm (x10 6 spermatozoa/ml) *** *** ns Number of total spermatozoa (x10 9 spermatozoa) ns ** * Number of produced doses ns ** * Significance: ns-not significant, *-P<0.05, **-P<0.01, ***-P<0.001 The differences between boars were recorded only in sperm concentration ( Table 3). The difference between the best (ID number 1) and the worst boar (ID number 5) was 91.99x10 6 spermatozoa per millilitre of ejaculate. Since the animals were raised in the same facility, under the same conditions, these differences in phenotypic values of ejaculate concentration, are influenced by the individual characteristics of boars. 16.05 VOL-volume of ejaculate (ml), CON-concentration of sperm (x10 6 spermatozoa/ml), NT-number of total spermatozoa (x10 9 spermatozoa), NPD-number of produced doses; Significance: ab, cd and de-P<0.05; AaBb-P<0.01; AB-P<0.001. Table 4. During the summer (season 3) ejaculate VOL was the lowest, and the difference compared to the season 2 was -123.06 ml. During the summer, sperm concentration was above average, but the NT and NPD were below average, as a consequence of the low volume of ejaculate. Regardless of the fact that the boars were housed in controlled environment conditions, it is possible that higher temperatures during the summer months demonstrated a negative impact on quantitative sperm production. The highest NPD was produced during the autumn months (season 4), and during the same period the highest concentration of sperm was recorded. In comparison to season 2, during the autumn, the sperm concentration was higher by 86.23x10 6 spermatozoa/ml. The reason for the highest concentration of sperm, the total number of spermatozoa in the ejaculate, and the number of doses during the autumn can be the stimulating effect of shortening of the photoperiod on neuro-humoral mechanism of sperm production. 16.91 VOL-volume of ejaculate (ml), CON-concentration of sperm (x10 6 spermatozoa/ml), NT-number of total spermatozoa (x10 9 spermatozoa), NPD-number of produced doses; Significance: ab-P<0.05; AaBb-P<0.01; AB-P<0.001.

Comparison of LSM mean values for observed traits of ejaculate between seasons is presented in
During the spring season the highest volume of ejaculate was determined (314.42 ml), as a result of negative correlation between volume and density and the lowest concentration of sperm (155.93x10 6 spermatozoa/ml). The nature of this correlation is reported in many studies (Wolf and Smital, 2009a;Wolf and Smital, 2009b;Kunowska-Slósarz and Makowska, 2011). The results of our study are partly similar to the study of Tomiyama et al. (2008), who have, during the spring months, determined the highest volume and the lowest concentration, whereas during the autumn period, the volume of ejaculate was the lowest, with a maximum concentration of spermatozoa. Partial similarity exists also with the research of Stančić et al. (2012) who have recorded, during the period June-August and September-November, the average volume of ejaculate (213 and 232 ml) and the concentration of spermatozoa (220x10 6 and 210x106 spermatozoa/ml), while higher values were recorded in the period from December to February (293 ml, 319x10 6 spermatozoa/ml) and March-May (285 ml, 284x10 6 spermatozoa/ml). Contrary to the findings of the present study, Okere et al. (2005), Kondracki et al. (2009), Wolf andSmital (2009a), in the spring period, have determined the minimum volume of ejaculate from the tested breeds. This research is not consistent with the results of Kunowska-Slósarz and Makowska (2011), who have found, in the cold season (October and November), the highest volume and lowest density of ejaculate. Partial similarity exists with the research of Rutten et al. (2000) in which the lowest number of standardized doses is obtained from the semen in the summer period (26.3), and the highest in autumn (28.7), however, in our study, less doses per ejaculate were obtained. Table 5 shows the ranking of boars according to the value of farrowing rate during the reproductive exploitation. The variation of the farrowing rate between boars ranged from 59.31 to 85.37%, which indicates a large difference in performance during use. Reproductive efficiency depends on several factors: boars, breeding season, sows with which boars are mated, weaning-oestrus interval, methods of insemination, sperm capacitive capabilities, etc. The difference in farrowing rate between the best (rank 1, ID number 5) and the worst boar (rank 7, ID number 1) was 26.06%. Regardless of the fact that the differences in the farrowing rate between boars were not statistically significant (P=0.0882), it is necessary to rank and promptly identify boars with farrowing rate below average.
A broad interval of variation was found in the research of Park (2013) in which the farrowing rate on pig farms with pigs of Yorkshire genotype varied in the range 63.8-91.6%. The differences in the farrowing rate between boars are also due to the individual characteristics, so our research is in accordance with the results of Ruiz-Sánchez et al. (2006) who have found that the farrowing rates between boars range from 71 to 98%. The concordance is also present with the results of study by Didion et al. (2009). These researchers have determined the variation of farrowing rate in the range 38.9-82.7%, between 18 investigated boars.