Synchronization of oestrus with cloprostenol and subsequent calving rates in artificially inseminated Zebu heifers

Oocyte structure in dominant and subordinate follicles in zebu cattle (Bos indicus)

The objective of the study was to investigate the light and ultrastructural morphology of dominant and subordinate oocytes from zebu (Bos indicus) cattle. Healthy cycling animals, which had a well-developed corpus luteum as judged by rectal palpation, were administered cloprostenol to induce luteolysis and therefore ovulation. The animals were slaughtered at days 3-11 post-ovulation, but those slaughtered at days 8-11 received a second injection of cloprostenol at day 7. Cumulus-oocyte complexes were aspirated from the largest (dominant) and the second largest (subordinate) follicles, and processed for transmission electron microscopy. Up to day 7, the dominant oocyte presented a peripherally located spherical oocyte nucleus with a compact dense fibrillar nucleolus. After day 7, the nuclear envelope became undulated and the nucleolus vacuolated. The nuclei contained an average of four nucleoli. In addition to vesicles, mitochondria, smooth endoplasmic reticulum, Golgi complexes and cortical granules, the ooplasm contained annulate lamellae and microtubules. Moreover, mitochondrial granules and pleomorphic forms of mitochondria were commonly observed. Some subordinate oocytes exhibited advanced stages of meiotic maturation. It is concluded that (1) the dominant oocyte undergoes certain prematurational changes, including nucleolus vacuolation, in the period from luteolysis up to the presumptive occurrence of the LH peak and (2) subordinate oocytes may undergo meiotic maturation.

Use of plasma progesterone profiles for the assessment of reproductive functions in indigenous Nigerian Zebu cattle

The reproductive performance of Zebu cattle is generally low. However, blood concentrations of progesterone may be of practical value in assessing the reproductive status of the Zebu female. This paper reviews recent findings regarding plasma progesterone profiles during different phases of the reproductive cycle of some Nigerian Zebu cattle. The reproductive phases examined include the estrous cycle, early pregnancy and the postpartum periods. Our findings describe variations in plasma progesterone profiles observed under field conditions. The practical implications of these findings in assessing reproductive functions in indigenous Nigerian Zebu cattle are examined.

Synchronization of estrus in beef cows and heifers with fenprostalene, cloprostenol sodium, and prostaglandin F2 alpha

The effects of fenprostalene, cloprostenol sodium and prostaglandin F2 alpha (PGF2alpha) on estrus, conception rate, pregnancy rate, and the interval from Day 1 of the breeding season to calving were studied on 135 purebred Angus cows and heifers. The cows and heifers were randomly allotted within age to the three estrus synchronization treatments and a control group. The calving percentages (for cows and heifers combined) that resulted from artificial insemination (AI) were 32.3, 31.4, 43.6, and 51.1% for the control, fenprostalene, cloprostenol sodium, and PGF2alpha groups, respectively. The calving percentage during the AI period by ages of dam at breeding were 54.2% for yearling heifers, 30.5% for two-year-olds, 47.6% for three-year-olds, and 26.1% for four-year-old or older cows. The percentage of cows and heifers detected in estrus and the percentage that conceived after the first injection for control, fenprostalene, cloprostenol sodium, and PGF2alpha groups were 51.6 and 22.3%, 59.3 and 32.1%, 76.8 and 44.1%, and 66.6 and 50.2%, respectively. The intervals from Day 1 of the breeding season to calving and from Day 1 of the calving season within each treatment to the birth of each calf were control, 285.9 and 23.8 d; fenprostalene, 283.6 and 13.4 d; cloprostenol sodium, 285.5 and 6.5 d; and PGF2alpha, 284.0 and 11.1 d.

Estrus response of indigenous Nigerian Zebu cows after prostaglandin F2 alpha analogue treatment under continuous observations for two seasons

The study was undertaken to determine the estrus response pattern of Zebu cows indigenous to Nigeria following treatment with prostaglandin F2alpha analogue and to determine the effect of season on the estrus parameters. Eighty cyclic Zebu cows were used in both the dry and wet seasons. Two single intramuscular injections of 25 mg of PGF2alpha analogue were given per cow 11 days apart regardless of the stage of the estrous cycle. The cows were then observed continuously for 168 h following each injection. The proportion of treated cows responding to PGF2alpha treatment in the wet season (90%) was significantly higher (P<0.005) than in the dry season (70.0%). The mean post-injection interval to onset of non-standing estrus (mucus discharge) was 30.6 h and 28.5 h in the dry and wet seasons, respectively. Similarly, the intervals to standing estrus were 69.7 h and 63.9 h in the two seasons, respectively. Seasonal effects were not significant. The duration of non-standing estrus was similar for the two seasons (164.2 h and 162.0 h) while the duration of standing estrus was significantly (P<0.01) longer in the wet season (19.2 h) than in the dry season (12.6 h). Also there was seasonal influence on the body condition score of cows, the palpability of corpora lutea (CL) and the intensity of estrus as determined by the number of mounts (17.9+/-2.0 and 51.2+/-3.4 mounts per cow per estrus period in the dry and wet seasons, respectively).