Modulating vaginal PH to influence sex ratio of offspring in naturally breed cows: Afield study in Iraqi cattle

Abstract

Sex selection in cattle carries considerable economic significance, particularly in optimizing herd composition for milk or meat production. The present study investigated the effect of altering vaginal pH at the time of Natural breeding on the sex of resulting offspring in local Iraqi cows. The hypothesis underlying this approach is that the vaginal microenvironment's acidity or alkalinity differentially affects the viability and motility of X-chromosome-bearing (female-determining) and Y-chromosome-bearing (male-determining) spermatozoa. Twenty-four (24) clinically healthy cows of reproductive age were included in the study and divided into three equal groups (n = 8 per group). Group I (Control) received natural service without any vaginal pH modification. Group II (Acidic group) received a pre-natural service intravaginal wash with a mildly acidic buffer solution (pH 4.5-5.0) using dilute lactic acid, intended to favour X-bearing sperm survival. Group III (Alkaline group), all groups Additionally, a progesterone-based synchronization protocol (CIDR Controlled Internal Drug Release with GnRH and PGF2?) was applied to improve synchronisation of ovulation across the treatment groups and to ensure that all inseminations were performed at a comparable and optimal time relative to ovulation. The CIDR insert was placed intravaginally for 7 days, with GnRH (100 mcg i.m.) administered at CIDR insertion, PGF2? (500 mcg i.m.) at CIDR removal, and a second GnRH dose 48 hours after CIDR removal. AI was performed 12-16 hours following the second GnRH injection and consider the animal come to estrus if Standing estrus was confirmed by the presence of a clear vaginal discharge, mounting behaviour, and elevated vulvar reddening and swelling. received a pre-natural service intravaginal wash with a mildly alkaline buffer solution (pH 7.5-8.0) using sodium bicarbonate solution, intended to favour Y-bearing sperm survival. Vaginal pH was confirmed using calibrated digital pH strips immediately before natural breed. All cows received by Three bulls of excellent reproductive efficiency were used in this study, with one bull assigned to each group. The bulls were verified to be free from reproductive diseases and had demonstrated proven fertility in previous trials to ensure high conception rates and avoid sexual exhaustion the same batch of frozen-thawed bovine semen from a single high-fertility bull. Pregnancy was confirmed by transrectal ultrasonography at day 28-35 post-AI. Fetal sex was determined ultrasonographically between days 55 and 75 of gestation by identifying the genital tubercle location relative to the umbilicus and tail. Results indicated that the alkaline-treated group (Group III) produced a significantly higher proportion of male calves (75.0%; 6/8) compared to the control group (50.0%; 4/8) and the acidic group (25.0%; 2/8). Conversely, the acidic group produced the highest proportion of female calves (75.0%). Overall pregnancy rates were comparable across groups (87.5%, 75.0%, and 87.5% for Groups I, II, and III, respectively), suggesting that pH modification at the evaluated concentrations did not substantially compromise conception rates. These preliminary findings suggest that pre-insemination vaginal pH modification is a simple, low-cost method that may be capable of sewing the sex ratio of bovine offspring. Larger-scale controlled trials are recommended to confirm these results and to establish optimum pH ranges, timing, and safety thresholds for routine application in cattle reproductive management.