Effect of ? carotene supplementation on oestrous synchronisation and milk production of Saanen goats

Abstract

Goats play a major role in the life of rural populations, especially in the Sub-Sahara Africa. The use of nutritional supplements such as ?-carotene and the reproductive management techniques can lead to improved goat productivity. ?-carotene is a carotenoid with an antioxidant activity, it plays beneficial role in getting rid of free oxygen radicals. Due to its antioxidant activity, the hypothesis is that ?-carotene will improve reproductive and milk production parameters of Saanen goats. The present study firstly evaluated the effect of ?- carotene and synchronisation protocol on ovarian activity and fertility of Saanen goats. Secondly, it evaluated the effect of ?-carotene supplementation on milk yield and components. A total of 60 Saanen does aged 1-6 years were used. In the first experiment, the factors in the design were supplementation (?-carotene supplemented versus nonsupplemented) and oestrous synchronisation protocol (equine chorionic gonadotropin (eCG) versus male effect). The supplemented group was dosed with ?-carotene 100 mg/goat/day for 60 days starting from 28 days before oestrous synchronisation. For the oestrous synchronisation protocols, all animals were inserted with controlled internal drug release devices (CIDR) for 11 days and were intramuscularly injected with prostaglandin at CIDR withdrawal. For eCG group, does were injected with 300 IU eCG, while for male effect group, bucks wearing aprons were introduced at CIDR removal. Blood samples were collected for evaluation of progesterone (P4), oestradiol-17? concentration and glutathione peroxidase (GPx) activity. The ultrasonographic scanning was performed to measure the number and size of follicles, corpora lutea (CL) size, and pregnancy diagnosis. The onset and duration of oestrus were monitored using bucks wearing aprons. In the second experiment, the animals were divided into two groups (?-carotene supplemented versus nonsupplemented). The animals were dosed with 50 mg/goat/day from the drying off period until kidding which was approximately a period of two months. The colostrum samples were collected three days postpartum and the ordinary milk samples were collected once a week for a month. The milk collected was analysed for the milk yield, fat, protein, lactose and somatic cells count. All the data were analysed using the GLM procedures and categorical modelling (CATMOD) procedures of SAS (version 9.4; 2014) while the correlation was analysed using Pearson correlation of SPSS (Version 23.0; 2015). ?-carotene supplementation and synchronisation protocol had no significant effect on body weight, response to oestrus, onset and duration of oestrus, oestradiol-17? concentration, number of follicles, size of largest follicle and CL, gestation length, birth weight, and litter size. However, ?-carotene supplementation had increased plasma P4 concentration and GPx activity. There was a significantly positive correlation between the CL size and P4 concentration regardless of ?-carotene supplementation. The synchronisation protocol had a significant effect on conception rate. The male effect group had higher conception rate (97%) than the eCG (72%) group. ?-carotene supplementation had no significant effect on milk yield and components. Milk type had a significant effect on the milk components of Saanen goats. Therefore, it can be concluded that male effect can improve conception rate and may be used to replace eCG on oestrous synchronisation of Saanen goats primed with progesterone. ?-carotene supplementation during the breeding period may play a beneficial role during embryo implantation and development as a result of increased progesterone concentration and glutathione peroxidase activity. Supplementation of Saanen goats with ?- carotene during the drying off period has no beneficial effect on milk yield and components.