Improved reproductive performance achieved in tropical dairy cows by dietary beta-carotene supplementation.

Dairy farming in tropical climates is challenging as heat stress can impair reproduction in cows. Previous studies have demonstrated the beneficial effects of beta-carotene supplementation on bovine reproductive performance. This study was performed in Thailand, where the temperature-humidity index (THI) during the experimental periods was measured to range from 78.4 to 86.1. Lactating Holstein cows classified as repeat breeders (previous artificial insemination [AI] failures) were randomly assigned into two treatments, control treatment (T1; received placebo, n = 200) and test treatment (T2; received 400 mg/h/day of beta-carotene, n = 200). All cows were subjected to a protocol for synchronization of ovulation and timed artificial insemination (TAI). The day of the 1st ovulation synchronized protocol was defined as day 0, and the total experimental period was 160 days. Daily placebo or beta-carotene supplements were given orally on day 0 and each subsequent day of the experiment. Diagnosis of pregnancy was performed using ultrasound on day 30 after insemination. Non-pregnant cows were subjected to further ovulation synchronizations (maximum of four) and TAI over a period of 160 days. Milk samples were collected every ten days throughout the experiment. The samples were analyzed for beta-carotene concentration, superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities. The pregnancies per AI of the cows in T2 were significantly greater than that of T1 from the 2nd to 4th TAI. During the entire experimental period, the pregnancies in T2 were significantly greater than that of T1. Cox's proportional hazards regression model data indicated a 44% greater probability of pregnancy for cows receiving beta-carotene. The concentrations of milk beta-carotene in T2 were significantly greater than T1 from the 2nd to 4th TAI. Significantly greater SOD and GPx activities were observed in T2 than T1, suggesting a reduction of oxidative stress in cows treated with beta-carotene. Dietary supplementation with beta-carotene thus improves the reproductive performance of repeat breeders exposed to heat stress, possibly by reducing oxidative stress.

Comparison of the Effects of Microbial Inoculants on Fermentation Quality and Microbiota in Napier Grass (Pennisetum purpureum) and Corn (Zea mays L.) Silage.

Forage preservation for livestock feeding is usually done by drying the plant material and storing it as hay or ensiling it into silage. During the ensiling process, the pH in the system is lowered by the activities of lactic acid-producing bacteria (LAB), inhibiting the growth of spoilage microorganisms and maintaining the quality of the ensiled product. To improve this process, inoculation of LAB could be used as starter cultures to shorten the ensiling time and control the fermentation process. Here, we compared fermentation quality and bacterial dynamics in two plant materials, whole-plant corn (Zea mays L.) and Napier grass (Pennisetum purpureum), with and without starter inoculation. The efficacy of Lactobacillus plantarum, L. brevis, and Pediococcus pentosaceus as starter cultures were also compared in the ensiling system. In whole-plant corn, pH decreased significantly, while lactic acid content increased significantly on Day 3 in both the non-inoculated and LAB-inoculated groups. Prior to ensiling, the predominant LAB bacteria were Weissella, Enterococcus, and Lactococcus, which shifted to Lactobacillus during ensiling of whole-plant corn in both the non-inoculated and LAB inoculated groups. Interestingly, the epiphytic LAB associated with Napier grass were much lower than those of whole-plant corn before ensiling. Consequently, the fermentation quality of Napier grass was improved by the addition of LAB inoculants, especially L. plantarum and a combination of all three selected LAB strains showed better fermentation quality than the non-inoculated control. Therefore, the different abundance and diversity of epiphytic LAB in plant raw materials could be one of the most important factors determining whether LAB starter cultures would be necessary for silage fermentation.