Assessment of expected breeding value for milk production traits of Murrah buffaloes under different heat stress zones in Indian sub-tropical climatic conditions.

Present study was conducted to investigate the impact of temperature humidity index (THI) on expected breeding value (EBV) for daily milk yield (DMY) and monthly test day fat% (MTDF%) and monthly test day SNF% (MTDSNF%) of Murrah buffaloes at ICAR-National Dairy Research Institute, Karnal. 302,101 records of DMY and 9864 records each on MTDF% and MTDSNF% buffaloes spanned over 20 years (1994 to 2013) from NDRI, Karnal, and meteorological were collected from ICAR-CSSRI, Karnal. The year was classified into three zones: non-heat stress (NHSZ), heat stress (HSZ), and critical heat stress zone (CHSZ) based on THI. The heritability (h2) estimates for DMY, MTDF%, and MTDSNF% in NHSZ were 0.432 ± 0.054, 0.090 ± 0.004, and 0.070 ± 0.002; in HSZ 0.491 ± 0.073, 0.112 ± 0.003, and 0.052 ± 0.001; and in CHSZ 0.524 ± 0.077, 0.116 ± 0.004, and 0.092 ± 0.003, respectively. The repeatability (r) for DMY, MTDF%, and MTDSNF% in NHSZ were 0.528 ± 0.006, 0.166 ± 0.007, and 0.135 ± 0.007; in HSZ 0.572 ± 0.007, 0.198 ± 0.006, and 0.077 ± 0.006; and in CHSZ 0.599 ± 0.008, 0.217 ± 0.004, and 0.156 ± 0.009, respectively. EBV for DMY and MTDF% was maximum in NHSZ (8.85 kg and 7.85%) and in HSZ (7.27 kg and7.78%) and lowest (6.90 kg and 7.77%) at CHSZ. For MTDSNF%, EBV was highest during NHSZ (9.6403), declined to 9.6265 at HSZ, and marginally elevated to 9.6271 at CHSZ. Impact of climatic factors on milk production and constituent traits is vital, and proper management should be followed during the heat stress and critical heat stress periods to improve the production performance of Murrah buffaloes.

Marker-assisted selection vis-à-vis bull fertility: coming full circle-a review.

Bull fertility is considered an indispensable trait, as far as farm economics is concerned since it is the successful conception in a cow that provides calf crop, along with the ensuing lactation. This ensures sustainability of a dairy farm. Traditionally, bull fertility did not receive much attention by the farm managers and breeding animals were solely evaluated based on phenotypic predictors, namely, sire conception rate and seminal parameters in bull. With the advent of the molecular era in animal breeding, attempts were made to unravel the genetic complexity of bull fertility by the identification of genetic markers related to the trait. Marker-Assisted Selection (MAS) is a methodology that aims at utilizing the genetic information at markers and selecting improved populations for important traits. Traditionally, MAS was pursued using a candidate gene approach for identifying markers related to genes that are already known to have a physiological function related to the trait but this approach had certain shortcomings like stringent criteria for significance testing. Now, with the availability of genome-wide data, the number of markers identified and variance explained in relation to bull fertility has gone up. So, this presents a unique opportunity to revisit MAS by selection based on the information of a large number of genome-wide markers and thus, improving the accuracy of selection.

Testicular cytology indicates differences in Sertoli cell counts between "good freezer" and "poor freezer" bulls.

In artificial insemination, poor quality of semen unsuitable for cryopreservation and susceptibility of spermatozoa to cryodamage in crossbred bulls have been a matter of concern. Present study was designed to identify the testicular cytology indices that might be used to predict the semen quality and cryotolerance of spermatozoa in bulls. Based on the ejaculate rejection rate and sperm cryotolerance, bulls (Holstein Friesian X Tharparkar crossbred) were classified into either good (producing good quality semen with spermatozoa having good cryotolerance; n = 4) or poor (producing poor quality semen with spermatozoa having poor cryotolerance; n = 4). Testicular cytology was studied in all the 8 bulls using fine needle aspiration technique. Testicular cytology of good bulls and poor bulls differed significantly. The proportion of Sertoli cells was significantly higher in good bulls (25.3 ± 1.6) compared to poor bulls (11.0 ± 0.8). The Sertoli cell index was 46.1 ± 5.0 in good bulls while it was only 13.8 ± 1.3 in poor bulls. The cut off values, as determined using Receiver Operating Characteristics analysis, indicate that the bulls having testicular cytogram comprising of < 15.5% Sertoli cells, < 24.3 Sertoli cell index and > 4.0 spermatogenic cells to Sertoli cell ratio might be a poor bull in terms of semen quality and cryotolerance of spermatozoa. The proportion of Sertoli cells in the testicular cytology had positive (P < 0.05) relationship with semen quality and cryotolerance of spermatozoa.

Differential histone modification status of spermatozoa in relation to fertility of buffalo bulls.

In this study genome-wide di-methylated H3K4 (H3K4me2) and tri-methylated H3K27 (H3K27me3) modification profiles were analyzed in spermatozoa of buffalo bulls having wide fertility differences. The custom designed 4 × 180 K buffalo (Bubalus bubalis) ChIP-on-chip array was fabricated by employing array-based sequential hybridization using bovine and buffalo genomic DNA for comparative hybridization. The buffalo specific array developed had 177,440 features assembled from Coding sequences, Promoter and CpG regions comprising 2967 unique genes. A total of 84 genes for H3K4me2 and 80 genes for H3K27me3 were found differentially enriched in mature sperm of high and sub-fertile buffalo bulls. Gene Ontology analysis of these genes revealed their association with different cellular functions and biological processes. Genes identified as differentially enriched between high and sub-fertile bulls were found to be involved in the processes of germ cell development, spermatogenesis and embryonic development. This study presents the first genome-wide H3K4me2 and H3K27me3 profiling of buffalo bull sperm. Results provide a list of specific genes which could be made responsible for differential bull fertility.

Development of a predictive model for daughter pregnancy rate and standardization of voluntary waiting period in Murrah buffalo.

A predictive model for daughter pregnancy rate (DPR) in Indian Murrah buffaloes has been developed. The data pertaining to first lactation reproduction traits, viz., age at first calving (AFC), first service period (FSP), and number of services per first conception (NS/FCON) of 719 Murrah buffaloes calved from 1985 to 2010 at the National Dairy Research Institute (NDRI), Karnal (Haryana), India were adjusted against significant environmental influence. First lactation reproduction records of 474 Murrah buffaloes were used for determining voluntary waiting period (VWP) and estimating DPR. Seven simple and multiple regression models in each case were developed where the buffaloes had their first insemination after 63 days (DPR 63), 84 days (DPR 84), and 105 days (DPR 105) of first calving. Among the seven models (I to VII) for DPR 63, DPR 84, and DPR 105, model II, having only FSP as an independent reproduction variable, was found to be the best prediction model, based on the four statistical criterions (high coefficient of determination (R 2), low mean sum of squares due to error (MSSe), conceptual predictive (CP) value, and Bayesian information criterion (BIC)). Three linear equations were developed using model II, viz., DPR 63 = 0.0033 (274 − FSP), DPR 84 = 0.0027 (332 − FSP), and DPR 105 = 0.0027 (310 − FSP). The average errors for the prediction of DPR 63, DPR 84, and DPR 105 were 1, 13, and 8 %, respectively. Therefore, 63 days of VWP is the optimum period for getting the best DPR in Indian Murrah buffaloes.

Enhancing milk and fertility performances using selection index developed for Indian Murrah buffaloes.

Selection for genetically superior Murrah buffaloes under Network Project on Buffalo Improvement, India, is presently based on milk yield, and it was observed that even in the absence of any direct selection pressure applied on fertility, there has been a downward trend in fertility associated with the selection for milk yield. The aim of the study was to develop selection indices which include fertility besides milk yield in Murrah buffaloes. Data pertaining to 1,224 lactation records spread over a period of 19 years were recorded and analyzed in the study. The negative association of pregnancy rate (fertility) with a 305-day milk yield (-0.08 ± 0.04) and wet average (-0.12 ± 0.02) indicated the importance of incorporating fertility trait in the construction of selection index. Four types of selection indices were constructed and evaluated. Two indices were developed using expected producing ability 305-days milk yield (EPAMY) with 6.5 and 4% fat in milk along with expected fertilizing ability (EFA). The other two indices developed consist of expected producing ability wet average (EPA WA) and EFA. The index involving (EPA WA and EFA) was found to be a more effective selection criterion in our herd, as the accuracy of index was more (0.61), in comparison to the index involving EPA MY and EFA. The robustness of selection index was assessed by increasing the relative economic values of included traits by 25 and 50%, and accuracy of the index remains almost stable without much change. The developed selection strategy involving EPA WA and EFA should be considered for the genetic evaluation of Murrah buffaloes, as it has a potential for maximizing the lifetime reproduction and production performances of the breed.

Detection of Single-Nucleotide Polymorphism in AGPAT6 Gene, Associated with Milk Fat Content, using Tetra-Primer ARMS PCR-Based Assay, in Karan Fries Breeding Bulls.

BACKGROUND: The bovine AGPAT6 gene is one of the potential candidate genes governing milk fat synthesis. OBJECTIVES: Identification of single nucleotide polymorphisms (SNP) in the targeted region of AGPAT6 gene and their effect on expected breeding values (EBV) of first lactation milk production traits viz. fat %, fat yield and 305 days milk yield in Karan Fries (KF) breeding bulls were sought. MATERIALS AND METHODS: A tetra-primer ARMS PCR technique was adapted to genotype an SNP, g.36,175,805C>T located on 5' flanking region of AGPAT6 gene. The relationship between EBV of milk production traits and polymorphic locus of AGPAT6 gene was assessed. RESULTS: Three kinds of genotype (CC, CT, and TT) with respect to g.36,175,805C>T SNP locus were observed. The identified SNP had significant (P<0.05) influence on EBV of fat % (EBV-FP). The KF bulls with CC and CT genotype had comparatively higher EBV-FP than the bulls with the TT genotype. The substitution of "C" allele by "T" allele led to a decrease of 0.0045 % in the EBV-FP. CONCLUSION: The identified SNP was significantly associated with EBV-FP, thus it may be utilized as a molecular marker for developing marker-assisted selection strategy to enhance the milk fat content in KF cattle population.

Polymorphism of growth hormone gene and its association with seminal and sexual behavioral traits in crossbred cattle.

The decline in the male reproductive ability in terms of sexual behavior and seminal traits might lead to nonavailability of required number of bulls in a progeny testing program. The present study was conducted in 493 crossbred cattle (Bos taurus × Bos indicus) bulls to study polymorphisms of growth hormone (GH) gene and its association with seminal and sexual behavioral characteristics. A 428-base pair fragment of GH gene spanning over the fourth exon, fourth intron, and fifth exon was amplified and digested with AluI restriction enzyme. Bulls were found to be polymorphic, with two variants, LL and LV, and higher genotypic frequency for LL being 0.88. Twelve nucleotide changes and a single nonsynonymous substitution of Leucine by Valine were observed from GH1 (L) to GH2 (V). Statistical analysis revealed that the genotype of the GH gene had a significant effect on libido score, reaction time, Flehmen response, requirement of mounting stimulus, sperm mass activity, number of semen doses per collection, individual fresh sperm motility, postthaw sperm motility, acrosome integrity, hypo-osmotic swelling test, live and dead count, total morphological abnormality, and head abnormality of sperm in crossbred bulls. Growth hormone gene might be considered a candidate gene for seminal and sexual behavioral traits in crossbred cattle.

Genome-wide profiling of sperm DNA methylation in relation to buffalo (Bubalus bubalis) bull fertility.

The DNA methylation pattern in spermatozoa of buffalo bulls of different fertility status was investigated. Spermatozoa isolated DNA from two groups of buffalo bulls (n = 5), selected based on their artificial insemination-generated conception rate data followed by IVF efficiency, were studied for global methylation changes using a custom-designed 180 K buffalo (Bubalus bubalis) CpG island/promoter microarray. A total of 96 individual genes with another 55 genes covered under CpG islands were found differentially methylated in sperm of high-fertile and subfertile buffalo bulls. Important genes associated with biological processes, cellular components, and functions were identified to be differentially methylated in buffalo bulls with differential fertility status. The identified differentially methylated genes were found to be involved in germ cell development, spermatogenesis, capacitation, and embryonic development. The observations hint that methylation defects of sperm DNA may play a crucial role in determining the fertility of breeding bulls. This growing field of sperm epigenetics will be of great benefit in understanding the graded fertility conditions of breeding bulls in commercial livestock production system.

Effect of lameness (hoof disorders) on productivity of Karan Fries crossbred cows.

In present study production performance of 96 lame cows was compared with 67 healthy cows. No significant effect of parity and year of calving on milk yield were observed but the effect of season of calving was significant (P < 0.01). Effect of lameness on milk yield at the second, third and fourth months and 305 days was highly significant (P < 0.01), and was also significant (P < 0.05) on lactation yield of the fifth and tenth months. The effect of lameness on monthly and 305-day milk yield was significant (P < 0.01) only for those cows diagnosed lame before calving and during the first month of lactation. The differences in mean monthly yield were highly significant (P < 0.01) at the second, third and fourth months; and significant (P < 0.05) in the first and fifth months. The loss in the first lactation month of cows which were diagnosed as lame in the second month, was found to be significant (P < 0.05). Thus the yield of the month previous to the diagnosis (sub-clinical stage) was also affected. A significant (P < 0.01) total loss of 498.95 kg of milk yield was observed during a period of 305 days.