Abstract
This study was aimed at investigating the effects of breed, age, body condition score, and nutritional status on follicular dynamics, quality, and oocyte yield in Cameroonian zebus cattleBos indicus(Gudali and Red and White Fulani). A total of 95 cows were investigated for breed, age, body condition score, and nutritional status. Blood samples and ovaries of these cows were collected during slaughtering. Follicles on each ovary were counted and measured using electronic digital calipers and then classified into three categories: small (<3 mm), medium (3 – 8 mm), and large (> 8 mm) diameter. The oocytes were retrieved by slicing each ovary into a Petri dish containing collected medium. The oocytes recovered were examined under a stereoscope (x 10) and classified into four groups based on the morphology of cumulus oophorus cells and cytoplasmic changes. From these ovaries, 3888 follicles were counted with an average population of 27.81 ± 6.88 follicles per cow. The average numbers of small, medium, and large follicles per cow were 17.26 ± 1.36 (62.06%), 9.64 ± 1.00 (34.66%), and 0.52 ± 0.32 (1.86%), respectively. A total of 1822 oocytes were harvested with an average of 19.11 ± 0.89 oocytes per cow. Oocytes graded I, II, III, and IV were 7.03 ± 2.30 (36.65%), 4.53± 2.01 (23.61%), 3.19 ± 0.85 (16.63%), and 4.43 ±1.62 (23.09%), respectively. This study also showed that ovarian weight, number of follicles, and oocytes’ yield of right ovary were higher than left ones (P < 0.05). Younger and normal cows (BCS = 3) presented higher (P < 0.05) number of follicles and oocytes. Urea and cholesterol levels were higher in Gudali and White Fulani cows (P < 0.05). This study indicated that ovaries of zebus harvested in slaughterhouse are an important source of follicular population, oocytes yield, and quality. Right ovaries are heavy and offer more numbers of follicles and oocytes than the left ones. BCS is the best indicator of nutritional status of cows. Important follicle populations are obtained from cows aging 6-9 years with BCS = 3.
Highlights
The livestock sector is a major component of the agricultural economy of Cameroon and contributes to about 1.643 billion USD to the national investment budget [1]
The total bovine productivity remains low in the country and is not enough to satisfy the demand of the population as recommended by Food and Agriculture Organization (FAO) [4]
In Cameroon, artificial insemination (AI) is used on local breeds with exotic semen (Holstein and Brahman), which contributes to the improvement of cattle genetic potential [8]
Summary
The livestock sector is a major component of the agricultural economy of Cameroon and contributes to about 1.643 billion USD to the national investment budget [1]. Several factors like poor genetic make-up and nutritional and reproductive pathologies have been identified as responsible items for these limitations in cattle productivity [5]. To solve these problems, assisted reproductive technologies (ARTs) such as artificial insemination (AI), in vitro embryo production (IVEP), multiple ovulation, and embryo transfer (MOET) have been developed to overcome reproductive inefficiency and accelerate genetic gain [6] and thereby reduce the generation intervals in farm animals. In Cameroon, AI is used on local breeds with exotic semen (Holstein and Brahman), which contributes to the improvement of cattle genetic potential [8]. IVEP permits the preservation of genetic potential of subfertile or dead animals [11] by the creation of a gene bank with oocytes recovered from slaughterhouses [12] for the improvement of livestock productivity [13]
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