Abstract:
In beef and dairy cattle, using sexed semen improves genetic progress and increases the proportion of desired gender calves following artificial insemination (AI). Oestrus detection is a limiting factor for maximum reproductive efficiency in dairy and beef cows. Many intrinsic and extrinsic factors, however, can hinder oestrous synchronization. Advanced sperm analyses in cattle provide accurate results on sperm quality. The best measure of sperm quality, according to the computer assisted sperm analysis (CASA) system, is the highest sperm motility or velocity. Therefore, the present study aimed to assess the application of timed artificial insemination (TAI) in synchronized dairy and beef cows using sexed semen in emerging farmer’s cattle herds of Gauteng province. A total of two hundred and thirty three cows (dairy; n = 136 and beef; n = 97) were selected from the emerging cattle herds. All cows were selected based on; age (3 to ≥ 7 years), body condition score (BCS) of ≤ 2.5, 3 and ≥ 3.5 (1 to 5 scale), not pregnant (excluding heifers), parity (1 to ≥ 5th), negative to contagious abortion, 90 days postpartum and lactation status (lactating or dry) and assigned to a 9-day Ovsynch + controlled intravaginal drug release (CIDR) and TAI protocol. In brief, on any given day throughout the oestrous cycle (Day 0) the cows received an insertion of CIDR device into the vagina, with intramuscular (i.m.) administration of Estradiol benzoate® (EB). On Day 8, i.m. administration of prostaglandin (PGF2α), with adhesive tail-head heat mount detectors (HMD) and CIDR was removed. On Day 9, i.m. administration of EB. The TAI was performed by the same inseminator 55 hours following CIDR removal using frozen-thawed X-sexed or non-sexed semen from 8 bulls (4 Holstein Friesian and 4 Angus), 2 sexed and 2 non-sexed sperm from each cattle type (dairy and beef) were supplied by American breeders service (ABS) Global, South Africa. At AI, oestrus behaviour was assessed by activation of the HMD colour either as are red (oestrus/activated patch) or white (no oestrus/ not activated patch). The GameteTek Cryo-Mobile laboratory truck was used during thawing of semen straws and sperm quality parameters (sperm motility, velocity, morphology and membrane integrity) were immediately assessed before AI. Pregnancy diagnosis was performed on Days 35, 65 and 95 following TAI with the aid of a transrectal ultrasound scanner and transrectal palpation. The calving date and calf sex were recorded at calving. All data were analyzed by general linear model (GLM) procedure of Statistical Analysis System (SAS, 9.3.3). Analysis of variance (ANOVA) was tested to compare treatment means for semen quality (sexed vs non-sexed semen), bull (n = 8) and treatment × bull as a fixed effect. Chi-square test was used to determine significant differences for equal proportions. Differences between the variables were considered to be statistically significant at P < 0.05. The proportion of oestrus expression was greater in dairy (85.3%) than in beef (65.0%) cows (P < 0.05). The average sperm total motility on dairy (sexed; 66.8% and non-sexed; 70.7%) and beef (sexed; 58.8% and non-sexed; 83.8%) bulls were recorded (P < 0.05). For morphology, high average live sperm percentages were recorded in both dairy (69.3%) and beef (71.2%) non-sexed sperm compared with dairy (57.2%) and beef (58.2%) sexed sperm, respectively (P < 0.05). However, sperm with tail abnormalities were recorded among dairy (sexed; 2.9% and non-sexed; 1.7%) and beef (sexed; 1.7% and non-sexed; 2.3%) bulls, (P > 0.05). The average sperm membrane integrity percentage was recorded among dairy (sexed; 51.0% and non-sexed; 64.1%) and beef (sexed; 52.3% and non-sexed; 71.2%) bulls. The proportion of pregnancy was high in dairy (sexed; 41.4% and non-sexed; 48.5%) compared with beef (sexed; 38.0% and non-sexed; 37.0 %) cows (P < 0.05). In conclusion, the acceptable oestrus synchronization expression and conception rates of dairy and beef cows were achieved. It is recommended that sexed semen can be successfully utilized through advanced reproductive biotechnologies in an organized emerging cattle farming system.
