Sire Evaluation Research Articles

Evaluation of sires using univariate animal model in Murrah buffaloes

The percentage of sires superior to the population mean was 63.24, 58.82, and 60.29% using LS, BLUP, and DFREML method respectively for AFC trait. The corresponding figure in percentage applying LS, BLUP and DFREML methods were 51.47, 58.82 and 39.71% for FCI; 60.29, 47.06 and 47.06% for FLMY; 54.41, 64.71 and 42.65% for FLP; 51.47, 80.88 and 44.12% for WFC, and 51.47, 29.40 and 44.12% for FSP trait, respectively. The LS and BLUP methods gave almost the same results. This study concluded with the results that LS and BLUP method gave the same result for evaluating the different sires considering all the traits, viz. AFC, FCI, FLMY, FLP, WFC, and FSP. The values of lower error variance and high relative efficiency suggested that the BLUP method was best for evaluating the different sires followed by LS and DFREML methods using different first lactation traits.

Genotype-environment interaction effects on weight gain in cattle using reaction norms

The existence of genotype-environment interaction (GEI) using reaction norm models and their impact on the genetic evaluation of Nellore sires for body weight at 120, 210, 365 and 450 days of age was verified. Three models were used: animal model (AM) that disregards GEI and the one-step reaction norm model with homogeneous and heterogeneous residual variance (1SRNMH_het). Bayes Inference via Gibbs Sampling was used to estimate the variance components. The AM model better fits to weights at 120 and 210 days of age, while 1SRNMH_het was more adequate for body weights at 365 and 450 days of age, suggesting the existence of GEI. The posterior means of direct heritability were 0.33±0.01 and 0.36±0.01 and maternal heritability of 0.21±0.01 and 0.19±0.01 for body weights at 120 and 210 days of age, respectively. For body weights at 365 and 450 days of age, posterior means of heritability varied along the environmental gradient, but the ranking of sires based on breeding values was not changed by different environmental gradients. All rank correlations were greater than 0.80, strongly suggesting a scale effect of GEI. Despite the evidence of GEI on post-weaning weight gain, it did not change the ranking of sires. Therefore, it did not have a relevant impact on the genetic evaluation of sires because they are robust to environmental changes.

Sire evaluation and effect of various factors on growth performance in males of Tharparkar and Karan fries cattle

The current study was undertaken with the objective of sire evaluation as well as studying the effect of genetic and non-genetic factors on growth performance in males of Tharparkar and Karan Fries Cattle. Data on body weights of Tharparkar and Karan Fries males born during the period 1994-2012 at ICAR-NDRI, Karnal, were utilized. The overall least squares means of birth weight and weights at one-month interval up to 12 months of age were 26.92±0.24, 35.55±0.22, 45.04±0.28, 57.56±0.40, 70.02±0.51, 82.62±0.66, 95.18±0.80, 105.11±1.55, 108.19±1.15, 114.20±1.15, 120.11±1.09, 130.35±1.11 and 136.91±4.13 kg respectively, in KF males. In TP males, least square means for birth and one-month were 21.34±0.77 and 25.63±0.67 kg, respectively. Effect of month and period of birth was highly significant on all traits except 1 month and 12-months for the former effect. The effects of genetic group and parity were mostly significant on body weights in KF males. Regression on birth weight was highly significant for all the weight traits. Effect of sire and birth-month was highly significant on all traits except one-month weight in KF. In Tharparkar, effect of season was highly significant on birth weight. Growth curves were linear, and deviations of average body weekly weight showed more divergence with increasing age. Growth rates from birth to three-months age in KF and TP males were 320 g/day and 226 g/day. Effect of non-genetic factors indicated the need of further improvement in feeding and management practices for augmenting growth, i.e. body weights especially in calves born to primiparous dams.

Evaluation of sires according to offspring beef quality

Beef production in the Russian Federation is mainly based on the use of over-replacement young animals and culled adult cattle of dairy and dual purpose breeds, and only 10 % of it is obtained from cattle of specialized beef breeds and their crossbreds. The selection and widespread use of the best breeding sires will help to increase the dairy and meat productivity of cows and overcome the negative correlation between the most important selected traits in large numbers of livestock. The results of the evaluation of the off spring of sires of Simmental breed of domestic and foreign selection (Canadian), as well as the sire of Red-and-White dairy breed have been presented in the article. The complex index of the sire Sokol 1335/6330 TS-2811 of Simmental breed of the Canadian selection (purebred), born in 1999 in the collective farm of name after Ilich in the Kalacheyevsky district in the Voronezh region (color pale-mottled), according to the beef characteristics of the off spring was 116, which corresponds to the international category EX – “excellent” (KI[sub]1[/sub]). From this it follows that the sire Sokol 1335/6330 TS-2811 is an improver for beef productivity with the assignment of category C[sub]1[/sub]. The sire Redky 6631 TS-2710 belongs to the line Signal 4863, born in 1989 in the state farm “Moskovsky” in the Kharkiv region (color pale-mottled) of domestic selection received the complex index 102 for the beef productivity of off spring, corresponding to KI[sub]3[/sub] (G) – “good” with the assignment of category C[sub]3[/sub]. The sire Pamir 9060,2566 CGF-123 of Red-and-White breed belongs to the line Siling Traijun Rocket 252803, which has the A[sub]3[/sub]B[sub]3[/sub] breeding category, is the loser in terms of the meat productivity of the off spring. It follows from this that the sons of sires of Simmental breed of the domestic and Canadian selection have the advantage in beef productivity over the sons of the sire of Red-and-White breed.

Comparison of sire breeding values for milk yield traits based on daughters milked once or twice daily in New Zealand

Abstract Context In New Zealand, cows are usually milked twice a day (TAD), but in ~8% of herds, cows are milked once a day (OAD) for the entire lactation. If a genetic correlation (rg) of the same trait expressed in two environments (such as TAD and OAD) is substantially <1.0, then the genetic merit assessed from TAD herds may not be reliable for predicting genetic merit in OAD herds. Initial evaluation of sires has been undertaken from progeny test herds with TAD milking, and the best sires have then been made widely available for use in TAD or OAD herds. Aim The study was designed to test formally whether sire re-rankings occur in widely used sires at different milking frequencies. Methods Regression coefficients and rank correlations (rS) for estimated breeding values (EBVs) of 242 widely used sires (86 Holstein-Friesian, 96 Jersey and 60 crossbred) were calculated for yields of milk, fat and protein, and for somatic cell score (SCS). The rS values were contrasted with expected rank correlations (rE) between TAD and OAD EBVs assuming rg = 1.0 between true BVs expressed at the two milking frequencies and accounting for the fact that sires were highly selected. Key results Within and across breeds, regression coefficients of OAD on TAD EBVs for the same traits were <1.0, but rS values between TAD and OAD EBVs of the same sires were strong (>0.75) for milk yield, moderate–strong for fat and protein yield (0.55–0.77), and moderate for SCS (0.41–0.65). Estimates of rS were higher than their critical rE values, indicating no significant sire re-ranking across milking frequencies. Conclusions On the basis of the results, a separate selection program to generate sires for use in OAD herds is not justified. Implications Farmers operating under OAD systems can rely on genetic evaluation of sires evaluated in TAD systems and used in the OAD population. However, producers should recognise that the realised productive and economic advantage of daughters of elite sires born in OAD herds is diminished relative to that expected in TAD herds.

Recent Advances in Sire Evaluation Methods: A Review

This review deals with the various traditional and recent methods of sire evaluation. A sire evaluation is a method of prediction of sire’s next-generation produced by breeding with specified females and creating their records in a specific environment. Breeding worth of progeny tested sires are obtained through sire index method that assigns ranking to each sire based on their genetic merit. Numerous sire indices are broadly classified in two type’s viz., indices which are purely meant for ranking purposes and those which, besides, provide an estimate of the breeding worth of each sire. Sires can be evaluated in single or multiple herds. The statistical equations represent sire evaluation as linear or non-linear methods. Numerous methods can be incorporated as the advances are made in sire evaluation based on data structures, breeding approaches and selection methods. There are various approaches of sire evaluation such as Least Squares Method (LSM), Simple Regressed Least Squares (SRLS), Best Linear Unbiased Prediction (BLUP) and Derivative-Free Restricted Maximum Likelihood (DFREML) for single as well as multiple trait models which can be used to derive genetic worth of an individual. An efficient method of sire evaluation shows minimum within sire variance or error variance.

Sire Evaluation Based on First Lactation 305 Day Milk Yield and Individual Part Lactation Records in Frieswal Cattle

Background: Frieswal, the crossbred cattle, between sahiwal and Holstein Friesian breed with 62.50 per cent of exotic (inheritance) with total lactation milk yield of (4000 Kg) with average lactation length 300 days (PDC Annual Report, 2015-16). Presently, the Frieswal Animal is mainly maintained at 36 Military Farms located in various agro-climatic regions in the country.Methods: The present study was undertaken on first lactation 305 days and part lactation records of 1470 Frieswal cows maintained over a period of 10 years (2003-2012) from military farm at CIRC Meerut Uttar Pradesh as well as Ambala. The success of any breed improvement programme depends mainly on the Sire evaluation which involves the estimation of expected breeding value of the bulls on the basis of average first lactation 305-day or less milk yield and part lactation records of their daughters (FL305DMY).Result: The estimate breeding value of 55 Frieswal sires on the basis of first lactation 305-day or less milk yield and individually part lactation records, by LSM, BLUP and DFREML methods were 2701.48 kg and 2660.70 kg, followed by 333.40, kg and 329.17 kg, respectively. A number of 55 Frieswal sires with three or more daughters were evaluated and ranked on the basis of first lactation 305-day milk yield and individual third month part lactation was having better heritability and comparatively higher genetic correlations with the first lactation 305-days or less milk yield.

Multiple linear regression analysis using monthly test day milk yield predicting the first lactation production performance for sire evaluation in Murrah buffaloes

A total of 9071 first lactation monthly test-day milk yield records of Murrah buffaloes were used to predict the first lactation 305-day milk yield (FL305DMY) by using stepwise backward regression analysis. For the prediction of FL305DMY best combination of monthly test-day milk yields were selected based on adjusted R 2 and RMSE values. The objective of the study was to compare various methods of sire evaluation viz., least squares (LSQ), simple regressed least squares (SRLS), best linear unbiased prediction sire model (BLUP-SM) and best linear unbiased prediction animal model (BLUP-AM) in terms of accuracy and efficiency. The methods were compared on the basis of error variance, coefficient of determination, coefficient of variation and rank correlations among the methods. The accuracy of prediction of FL305DMY from monthly test-day milk yields were observed to be best for TD-2 (45 th day), TD-4 (105 th day) and TD-6 (165 th day) combination with BLUP-AM as the most efficient method for sire evaluation. Individual, key monthly TD-6 (165 th day) milk yield has high rank correlation with EBVs obtained from actual 305-day milk yield. It was concluded that the optimum combination of TD-2 (45 th day), TD-4 (105 th day) and TD-6 (165 th day) or individual TD-6 (165 th day) can be used for genetic evaluation of Murrah sires.

Genetic and environmental analysis of female calf survival in the Israel Holstein cattle population

The objectives were to estimate the effects of various environmental factors on female calf survival of Israeli Holsteins, to estimate the economic value of calf survival under Israeli conditions, to estimate the genetic and environmental variance components for calf and cow survival using the individual animal model, to perform GWAS analyses of survival to first calving and herd life after first calving, to estimate the genetic and environmental trends for calf survival since 1985, to estimate genetic correlations of calf survival with the traits included in the current Israeli breeding index, and to estimate the consequences of inclusion of calf survival in the national selection index. Mean calf survival rate of Israeli Holsteins from 2001 through 2008 was 0.85, and the mean economic value of survival to first calving was $526. Birth month, gestation length, dystocia, and twin birth significantly affected calf survival rate. Dystocia and twin birth each reduced survival rate by 0.034. Survival rate was highest for calves born in October and lowest for calves born in February. The difference between these months was 3.4%. Maximum survival was at a gestation length of 276 d, the mean gestation length for this population. Survival rate was reduced to 0.76 for calves born after a gestation length of 260 d. The individual animal model was applied for all the genetic analyses. Heritability for calf survival to first calving, as estimated by REML, was 0.009, whereas heritability of herd life from first calving was 0.15. The complete data set for genetic analysis of survival to first calving included 1,235,815 calves born between 1985 and 2017. Annual genetic and phenotypic trends for calf survival were 0.019 and 0.015%, respectively. Correlations of transmitting abilities of 226 sires born since 2010 for calf survival with the traits included in the Israeli breeding index were significant only for the maternal effects of dystocia and stillbirth. The GWAS analysis was based on the transmitting abilities of 1,493 bulls with genotypes and reliabilities >0.5 for calf survival and cow herd life. There were 7 single nucleotide polymorphisms with coefficients of determination >0.03 for calf survival and 12 single nucleotide polymorphisms with coefficients of determination >0.05 for cow survival. There was no overlap between the genome-wide significant markers for the GWAS analyses of calf survival and cow herd life. This corresponds to the conclusion from the REML results and the low correlations between the sire evaluations that the genetic control of the 2 traits are not similar. Inclusion of calf survival in the Israeli breeding would result in a 0.5% increase in calf survival over 10 yr but reduce progress for the other traits by 8%.

Evaluation of sires with respect to production of their daughters and proportion of holstein blood

One of the best domestic dairy breeds is black-motley breed. At the same time, the Holstein breed has been one of the most highly productive for a long time. All world records for milk production were set by the Holstein breed. Moreover, it is very demanding in terms of management. In current conditions of the dairy cattle development, the semen of Holstein sires is still being used to increase the milk production of black-motley cows. Until today, there is no consensus on the optimal proportion of blood of the improving breed. The paper analyzes and evaluates the production of the daughters of sires depending on the proportion of blood of the Holstein breed. As a result, it was found that sires of Holstein lines have a positive effect on the production qualities of the black-motley breed, which ultimately leads to an increase in milk production. At the same time, in order to further improve the breeding and productive qualities of cows in herds, it is necessary to use sires assessed by the quality of the offspring, which are improvers in terms of milk yield and milk fat content. Consistent implementation of all technological solutions should be a fundamental factor in realization of the genetic potential.

26 Evaluation of sire versus dam effect on age at first calving in Brahman heifers

Abstract This study evaluated the possible effects of sire and dam on age at first calving in Brahman heifers. A total of 570 heifers born between the years 2001 and 2017 were exposed as yearlings to fertile bulls through time of pregnancy determination. A calving code was determined by calculating the mean (993 d) and standard deviation (187 d) of heifer age at first calving. Heifers considered to calve early (≤899 d; calving code = 1) or late (≥1087 d; calving code = 3) were at least half a standard deviation (94 d) away from the mean. All other heifers were considered to have a normal age at first calving (900 to 1086 d; calving code = 2). There were 35 sires with 5 or more daughters, resulting in a total of 543 heifers evaluated for the effect of sire. There were 323 daughters of evaluated heifers, which were evaluated for the effect of dam calving code. Also evaluated was the effect of dam and sire calving code on age at first calving of female offspring (n = 287). Variables analyzed included dam and sire of the heifer, age at first calving, and calving code. Data were analyzed using the GLM procedures of SAS and proportions were tested using Chi-square. Sire calving code did affect (P < 0.01) age at first calving and calving code in heifers, but dam calving code did not affect daughter calving code and age at first calving (Table 1). The proportion of daughters calving early compared to sire calving code significantly differed from the expected proportions (P < 0.01), whereas the proportions of daughters calving early for dam calving code did not differ (Table 2). A selection effort to produce Brahman heifers capable of calving early will not be effective from the dam side, but can be effective on the sire side.

Sire evaluation based on first lactation milk yield traits in HF X Gir halfbred

The data on first lactation milk production performance of 422, HF X Gir halfbred cows maintained at Research Cum Development Project on Cattle, MPKV, Rahuri were utilized for estimation of least squares means, correlation among the traits and heritability of traits. Breeding values of sires were estimated by REML computer programme. The overall least squares means (kg) of first lactation monthly test day milk yield (from 1 st to 6 th month) (FLMTDMY), first lactation peak milk yield (FLPMY) and first lactation 300 days milk yield (FL300 DMY) were 10.54 ± 0.14, 10.57 ± 0.13, 10.10 ± 0.12, 9.48 ± 0.12, 8.93 ± 0.11, 8.23 ± 0.11, 14.22 ± 0.14 and 2438.98 ± 38.49 respectively. Phenotypic and genotypic correlations among the traits were positive and significant (P<0.01). Heritability of traits was low to moderate and ranged from 0.06 to 0.25. Sire number HG-412 and HG-129 had highest breeding values for FLMTDMY and H-28I and HG-15 had highest breeding value for FLPMY and FL300DMY and ranked first.

Comparison of lactation curve models for fortnightly test day milk yield

The study of lactation curve helps to predict lactation milk production at a certain point of time and provides useful information for taking desirable decisions on preliminary sire evaluation, early culling of poor producers, breeding and feeding management and comparison of lactation records of unequal length. The test day milk yield data on 511 crossbred cattle were obtained and utilized according to fortnightly interval upto 305th day maintained at Instructional Dairy Farm, G B Pant University of Agriculture and Technology, Pantnagar (Uttarakhand). The different statistical models predicting the shape of lactation curve considered were exponential function, parabolic exponential function, inverse polynomial function and gamma type function. For fortnightly test day milk yield, the inverse polynomial function exhibited the highest coefficient of determination (R2=99.97%) followed by parabolic exponential (89.32%), gamma type (87.26%) and exponential function (35.70). Inverse polynomial function is the best fitted function for explaining the first lactation curve by utilizing the records of fortnightly test day milk yields.

Utility of first lactation fat energy corrected milk yield as a trait for genetic evaluation of Mehsana buffalo bulls using various sire evaluation methods

India being a vegetarian country, milk is the major source of dietary bio-energy, but majority of animals are routinely being evaluated on the basis of their milk producing ability. The present study was aimed to come up with a sire evaluation methodology based on first lactation Fat Energy Corrected Milk Yield (FBE) in order to obtain an accurate and unbiased estimate of breeding value of Mehsana buffalo bulls and ranking them on the basis of their daughter's performance for future herd improvement. Data for the present study included 7825 she buffaloes in their first lactations, extended over a period of 25 years (1989 to 2013), from field progeny testing programme of Dudhsagar Research and Development Association (DURDA), Dudhsagar Dairy, Mehsana, Gujarat. The data were classified into different subclasses based on period, season, cluster and age at first calving group. The average breeding values of Mehsana buffalo bulls evaluated for FBE by least squares method (LSM), best linear unbiased prediction sire model (BLUP-SM) and best linear unbiased prediction animal model (BLUP-AM) methods were 1215.89, 1185.7 and 1185.7 kcal, respectively. BLUP-AM method had lowest error variance as compared to LSM and BLUP-SM methods of sire evaluation. This indicated that BLUP-AM was most efficient method.

Sire selection and genetic improvement of dairy cattle assuming pure market competition

Breeding companies and farmers rely on selection indices to identify sires they expect to improve production system profitability. Such indices combine estimates of genetic merit for individual traits with corresponding economic values that are fixed based on circumstances at a particular time. Perfect market competition has also been proposed as an economic basis to value alternative sires. The objective of this study was to propose an economic model and develop it for the evaluation of dairy sires. The pure competition model (PUC) was used to evaluate the relationship between a profitability index based on the PUC approach versus the traditional selection index approach for 330 dairy sires comprising Holstein-Friesians, Jerseys, and Ayrshires. The correlation between these 2 selection indices was only 0.56, indicating that the conventional selection index did not correlate well with an index based on the PUC model. In particular, the higher ranking bulls were overvalued using the conventional selection index. Our study concluded that the use of fixed economic values is problematic for the delivery of consistent rankings in selection indices. In contrast, sire rankings based on PUC are more reliable because the sires are evaluated on the basis of efficiency gains rather than production while accounting for market prices and marginal values of dairy outputs over time.

Sire evaluation models for estimating breeding values of Mehsana buffaloes

First lactation data on 7,782 Mehsana buffaloes sired by 184 sires maintained at Dudhsagar Research and Development Association, Dudhsagar Dairy, Mehsana over a period of 24 years (1989–2012) were used to estimate least-squares means (LSM) and breeding value of the first lactation fat yield (FLFY) and average fat percentage (AFP) using univariate and bivariate models with the help of WOMBAT software. The effectiveness of different sire evaluation models using FLFY and AFP were compared on the basis of error variance, coefficient of determination (CV%), R2-value, AIC, BIC and Spearman’s rank correlation. The average estimate of FLFY and AFP was 135.04±0.57 kg and 7.11±0.11% in Mehsana buffaloes. These estimates were significantly affected by period and season of calving, and age at first calving group. The average expected breeding value of Mehsana buffalo bulls for FLFY and AFP were 133.24 kg and 7.14% using sire model (BLUP-SM), 135.71 kg and 7.22% using univariate animal model (BLUP-U-AM) and 133.23 kg and 7.14% from bivariate animal model (BLUP-B-AM), respectively for FLFY and AFP. The spearman’s rank correlation indicated similarity of rankings by BLUP-U-AM and BLUPB- AM. Animal model had a wider range of breeding values indicating the greater differentiating ability of the model. Based on error variance, AIC, BIC, R2 and CV; animal model was found to be superior in comparison to sire model.

Reaction norm analysis of pig growth using environmental descriptors based on alternative traits.

Contemporary group (CG) estimates of different phenotypes have not been widely explored for pigs. The objective of this study was to extend the traits used to derive environmental descriptors of the growing pig, to include CG estimates of early growth between birth and start of feed intake test (EADG), growth during feed intake test (TADG), lifetime growth (ADG), daily feed intake (DFI), backfat (BF) and muscle depth (MD). Pedigree and performance records (n=7,746) from a commercial Australian piggery were used to derive environmental descriptors based on CG estimates of these six traits. The CG estimates of growth traits described different aspects of the environment from the CG estimates of carcass traits (r<0.10). These definitions of the environment then were used in reaction norm analysis of growth, to evaluate sire-by-environment interaction (Sire×E) for growth. The most appropriate reaction norm model to evaluate Sire×E for growth was dependent on the environmental descriptor used. If the trait used to derive an environmental descriptor was distinctly different from growth (e.g., BF and MD), CG as an additional random effect was required in the model. If not included, inflated common litter effect and sire intercept variance suggest there was unaccounted environmental variability. There was no significant Sire×E using any of the definitions of the environment, with estimated variance in sire slopes largest when environments were defined by BF ( =97±83(g/day)2 ), followed by environments defined by DFI ( =39±101(g/day)2 ). While there appears to be differences in ability to detect Sire×E, improved data structure is required to better assess these environmental descriptors based on alternative traits. The ideal trait, or combination of traits, used to derive environmental descriptors may be unique for individual herds. Therefore, multiple phenotypes should be further explored for the evaluation of Sire×E for growth in the pig.

Comparative efficiency of different multiple linear regression prediction equations of first lactation 305-day milk yield for sire evaluation in Murrah buffaloes

In this study, first lactation 39059 weekly test-day milk yield records of 961 Murrah buffaloes were used to predict first lactation 305-day milk yield (FL305DMY) by stepwise backward regression method. The best single, two, three and four test day combinations were selected for prediction of FL305DMY based on adjusted R2 and RMSE values. The sires were evaluated for 305-day actual and predicted first lactation milk yield based on derived multiple regression equations using four methods viz. least squares (LSQ), simple regressed least squares (SRLS), best linear unbiased prediction sire model (BLUP-SM) and best linear unbiased prediction animal model (BLUP-AM) methods. The effectiveness of different sire evaluation methods were judged by error variance, coefficient of determination, coefficient of variation and spearman’s rank correlation. The accuracy of prediction of FL305DMY from weekly test day milk yields were observed to be best for TD-7 (48th day) and TD-22 (153rd day) combination with BLUP-AM as the most efficient method for sire evaluation. It was concluded that the FL305DMY can be predicted as early as 153rd day of lactation and further can be used for early genetic evaluation of Murrah sires.

Relationships of nutritional plane and feed efficiency with sexual development and fertility related measures in young beef bulls

Sexual development in beef bulls appears to be influenced by nutritional plane and feed efficiency. Yearling bulls fed high (GRAIN = 49) and moderate (ROUGHAGE = 109) nutritional planes, were submitted to a performance test where scrotal circumference (SC), scrotum and testis ultrasonograms and hormones were monitored throughout. Scrotal thermographs, blood cell counts and semen were evaluated at the end of the test. Residual feed intake (RFI) was the measure of feed efficiency, and bulls within each population were characterized as efficient and inefficient. During the test period, the GRAIN group had greater triiodothyronine (T3), leptin and scrotal skin thickness (SST) while having greater T3, leptin, % motile sperm, % normal sperm, scrotal temperature and values for red blood cell variables at the end of the test when compared to the ROUGHAGE group. During the test, the efficient GRAIN group had lesser testis pixel intensity while at the end of the performance test the bulls of this group had greater % normal sperm and lower testis pixel intensity compared to bulls in inefficient GRAIN group. In comparison, the efficient ROUGHAGE group had less T3, SC and SST while at the end of the test these bulls had less T3, leptin, SC, SST and scrotal temperature compared to bulls in the inefficient ROUGHAGE group. Complete blood cell variables, semen quality, scrotal biometry and thermography explained most of the variation in RFI. Results of the present study support the hypothesis that there is an antagonistic relationship between feed efficiency and sexual development in young bulls, which seems partially offset when there is a greater plane of nutrition. Thus, feed efficiency should be factored in the reproductive evaluation of sires.

WE ARE HONORED TO BE THE DISCIPLES OF VALERY BURKAT

WE ARE HONORED TO BE THE DISCIPLES OF VALERY BURKAT