103 OVIDUCTAL SECRETORY PROTEINS AS MEDIA SUPPLEMENT FOR IN VITRO EMBRYO DEVELOPMENT IN CATTLE

2012 ◽  
Vol 24 (1) ◽  
pp. 164
Author(s):  
S. K. Das ◽  
A. K. Sharma ◽  
V. Bhatia ◽  
A. K. Mohanty

The objective of this study was to determine the effect of oviducal secretory proteins (cOSP) as a media supplement on in vitro embryo development in cattle. Oviducal secretory proteins were collected from slaughterhouse oviducts by repeated freeze–thaw process and purified by ammonium sulfate precipitation (30%, 40%, 50% and 60%) followed by dialysis in 50 mM tris-HCl (pH 7.0) buffer. Dialyzed products were further purified by SP Sephadex cation exchange column and diethylaminoethyl cellulose (DEAE) anion exchange column, extensively washed and eluted by 50 mM tris-HCl (pH 7.0) containing 1.5 M NaCl. Both bound and unbound proteins were collected separately, dialyzed in phosphate buffer saline and quantified. Presence of protein was confirmed by running sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) and OSP bands between ∼66 kD to ∼97 kD were found. The pooled purified cOSP were used as a media supplement in 3 different concentrations (0, 10, 50 and 100 μg mL–1) for in vitro production (n = 3) of cattle embryos. Cumulus–oocyte complexes (n = 370) were collected from slaughterhouse ovaries, washed thoroughly and cultured in maturation media for 24 h in 5% CO2 at 38.5°C with maximum humidity. In vitro-matured oocytes were fertilized with in vitro capacitated sperm in Fert-BO media at 38.5°C in 5% CO2. After 16 to 18 h, oocytes were washed and cultured in embryo development media for cleavage. After 40 to 42 h, cleavage was observed and embryos were transferred into the replacement media for further development. A total of 68.42%, 69.31%, 61.82% and 41.67% cleavage rate and 15.38%, 21.31%, 14.70% and 15.0% blastocyst rate was observed at concentrations of 0, 10, 50 and 100 μg mL–1, respectively. These results indicate that addition of cOSP at 10 μg mL–1 increased blastocyst formation significantly (P < 0.05) compared with 0, 50 and 100 μg mL–1 and increased cleavage rate significantly (P < 0.05) compared with 50 and 100 μg mL–1. The authors acknowledge sincere thanks to the Director, Joint Director (Research), National Dairy Research Institute, Karnal and Incharge, Eastern Regional Station, National Dairy Research Institute, Kalyani, for providing the necessary facilities to carry out the work.

2012 ◽  
Vol 24 (1) ◽  
pp. 188
Author(s):  
A. K. Sharma ◽  
A. K. Mohanty ◽  
S. K. Das

The purpose of this study was to determine the effect of heparin-binding oviducal secretory proteins as a media supplement on IVF and embryo development in cattle. The native proteins were isolated from oviducts collected from a slaughterhouse by repeated freeze-thawing and precipitated by ammonium sulfate (60%) followed by dialysis overnight in 10 mM phosphate buffer solution containing 1 mM PMSF at pH 7.0 at 4°C. The dialyzed product was then passed through a high-performance liquid chromatography system with a HiTrap™ heparin prepacked column (GE Healthcare, Piscataway, NJ) equilibrated with 10 mM phosphate buffer containing 1 mM EDTA. The collected protein fractions [heparin-binding protein (HBP), heparin-unbinding protein (HUBP)] and total protein (TP) were run on SDS-PAGE. The SDS-PAGE profile of the eluted HBP fraction contained 5 major protein bands visible between approximately 66 to 97 kDa, the profile of the HUBP fraction contained 2 bands nearer to approximately 66 kDa and in TP, all 7 bands were visible between approximately 60 to 95 kDa. All 3 fractions (i.e. HBP, HUBP and TP) were used in 3 different concentrations (0, 1, 10 and 30 μg mL–1) for in vitro maturation, sperm preparation, IVF and in vitro culture of cleaved embryos. Cumulus–oocyte complexes were collected from slaughterhouse ovaries, washed 4 to 5 times and cultured in maturation media for 24 h in a 5% CO2 incubator at 38.5°C with maximum humidity. In vitro-matured oocytes were co-incubated with capacitated sperm in Fert-BO media at 38.5°C in 5% CO2 in air with maximum humidity. After 18 h, oocytes were washed thoroughly and cultured in embryo development media for cleavage. After 40 to 42 h, cleavage was observed and embryos were transferred into the replacement media for further development. In the HBP group, overall cleavage rates (%) were 63 ± 3.0, 53 ± 2.6, 65 ± 4.7 and 43 ± 0.6 and blastocyst formation (%) was 17 ± 1.6, 23 ± 2.5, 25 ± 2.2 and 24 ± 1.7 in 0, 1, 10 and 30 μg mL–1 concentrations, respectively. However, in the HUBP group, the overall cleavage rates (%) were 66 ± 4.3, 56 ± 2.0, 60 ± 2.7 and 32 ± 0.8 and blastocyst formation (%) was 18 ± 1.1, 25 ± 1.8, 24 ± 2.2 and 14 ± 0.8 in 0, 1, 10 and 30 μg mL–1 concentrations, respectively. In the TP group, cleavage rates (%) were 67 ± 4.9, 60 ± 4.1, 73 ± 3.2 and 41 ± 1.6 and blastocyst formation (%) was 19 ± 1.1, 18 ± 1.9, 27 ± 2.2 and 20 ± 1.6 in 0, 1, 10 and 30 μg mL–1 concentrations, respectively. These results indicate that 10 μg mL–1 of the total oviductal secretory protein fraction used as a media supplement significantly increased (P < 0.01) the cleavage rate and blastocyst formation as compared with the HBP and HUBP fractions. The authors sincerely acknowledge the director and joint director (R), National Dairy Research Institute, Karnal and Incharge, Eastern Regional Station, National Dairy Research Institute, Kalyani, India, for providing the facilities to carry out the work.


2021 ◽  
Vol 99 (Supplement_3) ◽  
pp. 310-310
Author(s):  
Saulo Menegatti Zoca ◽  
Julie Walker ◽  
Taylor Andrews ◽  
Adalaide C Kline ◽  
Jerica J Rich ◽  
...  

Abstract Sire conception rate (SCR) is a field measure of fertility among bulls, but it can be influenced by several factors (Sperm transport, sperm-egg binding, early embryo development, etc). The objective of this study was to evaluate the relationship between SCR, sperm motility, SERPINA5 concentrations, and in vitro embryo development. Measurements were performed in 19 bulls with SCR values ranging from -7.7 to 4.45. For each bull, an aliquot of frozen-thawed semen was used for analyses of total (TMOT) and progressive (PROG) motility. Remaining semen was fixed with 2% formaldehyde, and concentration of SERPINA5 was determined by immunolocalization (antibody SERPINA5/Dylight405; PA5-79976-Invitrogen / ab201798-Abcam). Mean fluorescence intensity was determined in ~200 sperm heads/bull. Approximately 149 oocytes/bull were fertilized in vitro for embryo development analysis (cleavage and blastocyst rates). Statistical procedures were performed in SAS (9.4) using the procedures CORR for correlations (SCR, TMOT, PROG, SERPINA5, cleavage and blastocyst) and GLIMMIX for comparison of “field-fertility” (SCR divided in HIGH or LOW) and “field-embryo-fertility” (LOW-SCR sires were divided based on blastocyst rate (HIGH or LOW) resulting in two classifications; LOW-HIGH≥31% and LOW-LOW≤26%, respectively). There were positive correlations (P &lt; 0.05) between cleavage-blastocyst (r=0.50), SERPINA5-cleavage (r=0.48), and TMOT-PROG (r=0.76). Sire SCR was not associated with SERPINA5, TMOT, PROG, cleavage and blastocyst rate (P &gt; 0.52). Among LOW-SCR sires, LOW-LOW sires (-4.83±0.60) tended to have a better SCR score than LOW-HIGH (-6.18±0.42) sires (P = 0.08), but there were no differences (P &gt; 0.43) between LOW-HIGH, LOW-LOW, and HIGH sires for SERPINA5, TMOT, PROG, and cleavage. In conclusion, some LOW SCR sires have good embryo development indicating a different mechanism for their low SCR; however, these differences in SCR could not be explained by TMOT, PROG, SERPINA5, cleavage and blastocyst. There were, however, positive correlations between cleavage-blastocyst rate, and SERPINA5-cleavage rate.


Reproduction ◽  
2001 ◽  
pp. 737-744 ◽  
Author(s):  
Z Roth ◽  
A Arav ◽  
A Bor ◽  
Y Zeron ◽  
R Braw-Tal ◽  
...  

The fertility of dairy cows decreases during the summer and remains low during the cooler autumn although the animals are no longer under heat stress. The aim of this study was to characterize a delayed effect of summer heat stress on oocyte quality in the autumn and to improve oocyte quality by enhanced removal of follicles damaged during the previous summer. Lactating cows (n = 16) were subjected to heat stress during the summer. In autumn, ovarian follicles (3-7 mm in diameter) were aspirated by an ultrasound-guided procedure during four consecutive oestrous cycles. Follicles were aspirated from control cows on day 4 and from treated cows on days 4, 7, 11 and 15 of each oestrous cycle. All cows received PGF(2alpha) and GnRH injections on days 19 and 21, respectively, and maintained cyclicity, as indicated by plasma progesterone concentrations. On day 4 of each cycle, the oocytes recovered were examined morphologically, matured and activated in vitro, and cultured for 8 days. In cycle 1 (early October) both groups showed low percentages of grade 1 oocytes, cleavage, four- and eight-cell embryos, morulae and parthenogenetic blastocysts. Subsequently, the number of grade 1 oocytes increased earlier (cycle 2) in treated than in control cows (cycle 3; P < 0.05). The cleavage rate in the control group remained relatively low throughout (32-58%), whereas in the treated group it increased from 40% (cycle 1) to 75% (cycles 3 and 4; P < 0.05). The number at each stage of embryo development increased slightly but remained low throughout in the control group, whereas in the treated group significant (P < 0.05) increases of all stages were observed in cycles 3 and 4. The results show a delayed effect of summer heat stress on oocyte quality and embryo development in the autumn. Enhanced removal of the impaired cohort of follicles led to earlier emergence of healthy follicles and high quality oocytes in the autumn.


Reproduction ◽  
2003 ◽  
pp. 543-553 ◽  
Author(s):  
JM Lozano ◽  
P Lonergan ◽  
MP Boland ◽  
D O'Callaghan

Two experiments were carried out to study the effect of nutrition on embryo development in two periods in superovulated ewes (Expt 1) and on oocyte developmental capacity during the late follicular phase (Expt 2). In Expt 1, a lower superovulation response in terms of animals ovulating (P < 0.05), ovulation rate per ewe ovulating (P = 0.1) and number of good quality embryos per animal treated (P < 0.07) was noted in ewes fed an ad libitum diet compared with ewes offered control (1.5 times the daily maintenance energy requirements, 1.5 x M) or low energy (0.5 x M) diets. Nutrition also modified the morphological and functional quality of the oocytes and embryos recovered. Thus, 92% of day 4 embryos recovered from ewes offered the control diet were classified as good embryos, compared with 70 and 82% of those recovered from ewes offered the ad libitum and low diets, respectively (P < 0.05). Ewes offered the ad libitum diet had a greater percentage of poorly developed embryos compared with ewes offered the control or low diets (P < 0.05). Ewes fed the low diet tended to have more non-fertilized oocytes than ewes offered the control diet (P = 0.09). Diet of recipient ewes to which good quality embryos were transferred on day 4 did not affect embryo quality, when assessed 12 days later (day 16 of pregnancy). However, recipient diet affected prostaglandin F(2alpha) (PGF(2alpha)) production in vitro, and uterine tissue that originated from recipient ewes on the low diet secreted more PGF(2alpha) relative to uterine tissue that originated from recipients on the control diet (P < 0.05). In Expt 2, fewer total (P < 0.05) and good quality (P < 0.01) oocytes and a lower percentage of good quality oocytes (P < 0.01) were obtained from superovulated ewes offered the ad libitum diet compared with ewes offered the low diet. In addition, cleavage rate tended to be higher (51 versus 35%, P = 0.09) in ewes offered the low diet compared with ewes offered the ad libitum diet. In conclusion, changes in diet can affect the quality of the oocyte and embryo in superovulated sheep. A lower superovulation response and a decrease in the quality of oocytes and embryos indicate that ad libitum diets are highly detrimental for superovulatory programmes when compared with low and control diets. In addition, the results from the present study indicate that a low energy diet during early embryo development increased the uterine production in vitro of PGF(2alpha) which could lead to a poor uterine environment thereby compromising the development of the embryo.


2010 ◽  
Vol 22 (1) ◽  
pp. 233
Author(s):  
M. K. Jena ◽  
D. Malakar ◽  
A. K. De ◽  
S. Garg ◽  
Y. S. Akshey

The present study was carried out to see the developmental efficiency of zona-free and with zona parthenogenetic goat embryos cultured in Research Vitro Cleave from Cook Australia (RVCL), Embryo Development Media (EDM), modified synthetic oviductal fluid (mSOF), and modified Charles Rosenkrans media (mCR2a). Zona-free embryos were cultured in 4 media, whereas with zona embryos were cultured in 3 media except mCR2a. Ovaries were collected from slaughterhouse and oocytes were isolated by puncturing the follicles in medium containing Dulbecco’s phosphate-buffered saline, 3% BSA, and 50 μg mL-1 gentamicin. Oocytes were matured in maturation medium containing TCM-199 (HEPES modified), 0.05 mg mL-1 Na pyruvate, 0.003 mg mL-1 L-glutamine, 5.5 mg mL-1 glucose, 3 mg mL-1 BSA, 5 μg mL-1 FSH, 10 μg mL-1 LH, 1 μg mL-1 estradiol-17β, 50 μg mL-1 gentamicin, and 10% FBS in 5% CO2 in air at 38.5°C. The COC (15 to 20 oocytes) were placed in 100-μL droplets of maturation medium and incubated in a CO2 incubator (5% CO2 in air) with maximum humidity at 38.5°C for 27 h. Matured oocytes were made cumulus free by treatment with hyaluronidase (0.5 mg mL-1) and zona-free by pronase (2 mg mL-1) in zona-free parthenogenesis. Then the oocytes were activated by 5 μM Ca ionophore for 5 min in a CO2 incubator and then treated with 2 mM 6-DMAP for 4 h. Activation was also done by electrical activation with DC 1.78 kV cm-1, 20 μs, and 2 pulses. Then the zona-free oocytes were kept for in vitro culture in 4 types of media such as RVCL, EDM, mSOF, andm CR2a for 7 days in 5% CO2 in air at 38.5°C. The cleavage rate andmorulae formation were observed in RVCL 40.95%, 13.95%, in EDM 46.92%, 14.75%, in mCR2a 56.66%, 5.88%, and in mSOF 48.23%, 14.63%, respectively. The cleavage rate and morulae formation were also found 55.9%, 14.63% during chemical activation and 32%, 12.5% in electrical activation. Hence, better result was found in chemical activation than electrical activation. For with zona parthenogenesis, the matured oocytes were chemically activated by 5 μM Ca ionophore for 5 min and 2 mM 6-DMAP for 4 h. Then the oocytes were cultured in RVCL, EDM, and mSOF in 100-μL micro-drops media for 7 days. The cleavage, morulae, and early blastocyst production rate were as follows: cleavage rate 75.68%, 72.03%, and 57.11%; morulae 44.61%, 30.29%, and 40.22%; and early blastocyst 17.49%, 11.88%, and 25.01% in RVCL, EDM, and mSOF, respectively. Hatched blastocyst formation rate was 6.75%, 5.48%, and 1.15% in RVCL, EDM, and mSOF, respectively. It could be concluded that zona-free parthenogenetic embryos were produced better in EDM medium and with chemical activation. With zona parthenogenetic embryo development was significantly (P < 0.05) higher in RVCL and EDM media.


2009 ◽  
Vol 21 (1) ◽  
pp. 156
Author(s):  
E. Dovolou ◽  
M. Clemente ◽  
G. S. Amiridis ◽  
I. Messinis ◽  
A. Kalitsaris ◽  
...  

We have previously shown that follicular and oviductal fluid provide greater total protection against lipid peroxidation than the respective media used for the in vitro embryo production. Reactive oxygen species (ROS) production has been implicated as a major cause for the reduced in vitro bovine embryo production; it is believed that they participate in meiotic arrest of oocytes, embryonic block and cell death. The aim of this study was to determine whether guaiazulene (G), an exogenous antioxidant, added in the post fertilization culture medium would affect the early embryo development and the quality of the produced blastocysts in terms of mRNA expression of several important genes. In a previous study we had shown that media modified with 0.01 mm of G provided the same antioxidant protection as the respective in vivo environments (i.e. the follicular and the oviductal fluid). Bovine cumulus–oocyte complexes (COC) were aspirated from ovaries derived from slaughtered cows and matured in groups of 50 in 500 μL in TCM199 with 10% fetal calf serum and 10 ng mL–1 Epidermal Growth factor at 39°C in an atmosphere of 5% CO2 in air and maximum humidity. Twenty-four hours later matured oocytes were inseminated with frozen/thawed bull semen and co-incubated in the same conditions as maturation. Presumptive zygotes were divided into 4 groups and cultured in groups of 25 in 25 μL of SOF with 5% FCS (Control–, n = 355), supplemented with 0.01 mm of G (n = 344) or 0.1 mm of G (n = 345) or 0.05% DMSO – the G diluent–(Control+, n = 347) at 39°C in an atmosphere of 5% CO2, 5% O2 and maximum humidity. Blastocyst yield was recorded on Days 6, 7, 8 and 9; Day 7 blastocysts from each group were snap frozen and stored at –80°C for mRNA extraction. Quantification of transcripts for aldose reductase mRNA (AKRIBI), prostaglandin G/H synthase-2 (PGHS-2, COX-2), glyceraldehyde 3-phosphate dehydrogenase (GADPH), facilitated glucose/fructose transporter, member 5 (GLUT-5) genes related to metabolism, glutathione peroxidase 1 (GPX1), glucose-6-phosphate dehydrogenase (G6PD) antioxidant enzymes and placenta-specific 8 (PLAC8) related to implantation was carried out by real-time quantitative RT-PCR. Data for embryo development and on transcript abundance were analyzed by chi square and ANOVA, respectively. Cleavage rate tended to be higher in 0.01 mm group than in Control– (77.87% v. 71.41%, P = 0.07). Barring that, no other differences were detected in cleavage rate (Control+: 71.32%; 0.1 mm: 72.75%) or in the overall blastocyst yield on Day 9 (Control–: 25.50%; Control+: 26.71%; 0.1 mm: 25.75%; 0.01 mm: 29.58%). The relative abundance of genes studied varied among groups, but these differences were not significant. We infer that under the current culture conditions, G as an antioxidant has no serious direct effect on early embryo development or on embryo quality at least on the mRNA transcripts studied. Further studies using the same antioxidant in different atmospheric conditions are planed. ED and GSA were sponsored by COST (FAO702) and OECD fellowships, respectively.


2016 ◽  
Vol 28 (2) ◽  
pp. 147
Author(s):  
J. Block ◽  
A. M. Zolini ◽  
E. Carrascal-Triana ◽  
A. Ruiz ◽  
P. J. Hansen ◽  
...  

The objective of the present study was to determine the effect of supplementation of maturation media with L-carnitine and trans-10,cis-12 conjugated linoleic acid (CLA) on embryo development and survival following cryopreservation. Immature bovine cumulus-oocyte complexes (n = 1796) were harvested from abattoir-derived ovaries and randomly assigned in a 2 × 2 factorial design to be matured in maturation medium [TCM-199 with Earle salts supplemented with 10% (vol/vol) bovine steer serum, 2 μg mL–1 oestradiol 17-β, 20 μg mL–1 bovine FSH, 22 μg mL–1 sodium pyruvate, 50 μg mL–1 gentamicin sulfate, and 1 mM glutamax®] supplemented with or without 100 mM CLA and with or without 3.03 mM L-carnitine for 22 to 24 h at 38.5°C in a humidified atmosphere of 5% CO2. The proportion of oocytes that cleaved was determined on Day 3 after insemination, and the proportion of oocytes developing to the blastocyst and advanced blastocysts stages (expanded, hatching, and hatched) was assessed on Day 7. Blastocyst and expanded blastocyst stage embryos (n = 270) were harvested on Day 7 and subjected to controlled-rate freezing following equilibration in 1.5 M ethylene glycol. Embryos were thawed and then cultured for 72 h in SOF-BE1 (Fields et al. 2011) supplemented with 10% (vol/vol) fetal bovine serum and 50 μM dithiothreitol. Post-thaw re-expansion and hatching rates were determined at 24, 48, and 72 h. The experiment was replicated 5 times. There was no effect of supplementation of maturation medium with either CLA or L-carnitine on the proportion of oocytes that cleaved at Day 3 or that developed to the blastocyst and advanced blastocyst stages at Day 7 after insemination. There was no interaction between CLA and L-carnitine affecting cleavage rate or embryo development. Supplementation of maturation medium with L-carnitine did not affect post-thaw re-expansion or hatching rates. In contrast, treatment with CLA during maturation reduced (P < 0.05) post-thaw re-expansion (24 h: 75.2 ± 3.8% v. 60.3 ± 4.1%; 48 h: 82.0 ± 3.4% v. 64.9 ± 4.0%; 72 h: 78.9 ± 3.6% v. 65.9 ± 4.0%, respectively) and hatching (24 h: 33.7 ± 4.2% v. 23.5 ± 3.6%; 48 h: 61.1 ± 4.3% v. 44.0 ± 4.2%; 72 h: 62.6 ± 4.3% v. 50.2 ± 4.2%, respectively) rates at all time points. There was no interaction between CLA and L-carnitine affecting post-thaw viability. In conclusion, supplementation of maturation medium with L-carnitine did not affect embryo development or post-thaw viability. Although addition of CLA during maturation did not affect embryo development, post-thaw cryotolerance was reduced following CLA supplementation. There was no beneficial effect of supplementing maturation medium with both CLA and L-carnitine on embryo development or post-thaw cryosurvival.


1999 ◽  
Vol 1999 ◽  
pp. 2-2 ◽  
Author(s):  
M. Kuran ◽  
M.E. Staines ◽  
G.J. McCallum ◽  
A.G. Onal ◽  
T.G. McEvoy

Ovine embryos produced in synthetic oviduct fluid (SOF) medium or in coculture with granulosa cell monolayers supplemented with low (A; 120 μmol/l) and high (B; 190 μmol/l) ammonia-producing steer sera caused different degrees of fetal oversize (Carolan et al., 1998). The objective of the present study was to determine whether the effects on fetal growth induced by these sera were associated with alterations in early embryo development.A total of 911 bovine oocytes, used in 8 replicates to test the effect of three culture treatments on embryo development, were matured and fertilized in vitro (IVF= Day 0). Presumptive zygotes were allocated on Day 1 to culture in SOF supplemented with 10% v/v steer serum (SOF+A, n=308; SOF+B, n=302) or with amino acids plus 0.4% w/v crystalline BSA (SOFaaBSA, n=301). All cultures were in 20 μl droplets under oil (38.5°C; 5% CO2, 5% O2; 4 zygotes per drop) and droplets were renewed every 48 h. Cleavage rate was recorded on Day 3. On Days 7 and 8, blastocyst yields, grade 1 and 2 blastocysts, their cell numbers (by staining with Hoechst 33342) and their stage and diameter were determined.


Author(s):  
B. C. Naha ◽  
A. K. Chakravarty ◽  
M. A. Mir ◽  
M. Bhakat ◽  
A. P. Singh ◽  
...  

In the present investigation, bull fertility of Sahiwal breeding bulls has been studied. The study was conducted on records of 43 Sahiwal bulls maintained under 8 sets of Sahiwal breeding project at ICAR- National Dairy Research Institute, Karnal (India). The data on bull fertility of Sahiwal breeding bulls during 27 years (1987-2013) were analysed. The presented study revealed that the average conception rate based on first AI and overall conception rate of Sahiwal breeding bulls were estimated as 45.95% and 46.38 %. Average sire conception rate of Sahiwal breeding bulls range from – 2% to + 3% and – 2% to + 4 % for conception rate based on first AI and overall conception rate. It has been observed that the average conception rate based on first AI was lower as compare to overall conception rate and higher conception rate of Sahiwal breeding bulls is having higher sire conception rate.


Author(s):  
Mohsin Ayoub Mir ◽  
A. K. Chakravarty ◽  
B. C. Naha ◽  
V. Jamuna ◽  
Dinesh M. Maher

In present investigation, the effect of non-genetic factors on age at first freezing and age at first use in Murrah breeding bulls has been studied. The data on reproduction traits of 57 Murrah bulls under NDRI (National Dairy Research Institute) centre belonging to 14 sets of Network Project on Buffalo Improvement at ICAR-NDRI, Karnal (Haryana), India during 20 years (1993-2013) were analysed using fixed linear model. The data were classified into various sub-classes for season of freezing and use, period of freezing and use, parity, stages of lactation and age groups of buffalo for age at first freezing and age at first use of Murrah breeding bulls. The average age at first freezing and use of Murrah bulls was estimated as 3.46 ± 0.08 years and 4.05 ± 0.13 years with the coefficient of variation of 14.43 % and 12.27%. The overall least-squares means for age at first freezing of Murrah bulls was estimated as 3.38 ± 0.01 years. Period and season of freezing had significant effect (P


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