Abstract:
An experiment was conducted to investigate the effects of dietary betaine supplementation on milk production, milk compositions and relevant other parameters to milk synthesis in late lactating crossbred Saanen goats. The mechanisms by which betaine supplementation on mammary function including intramammary factors and extramammary factors were carried out. Ten, multiparous, non pregnant crossbred Saanen goats in late lactation approximately 11 weeks postpartum were divided into two groups of five animals each. The experimental animals were received diet supplemented with 4 g betaine per kg of the concentrate diet for four weeks, while the control animals were received the similar concentrate diet without betaine as placebo for concurrent control. The results showed that animals receiving betaine supplementation decreased significantly (P < 0.05) roughage DMI during treatment and post-treatment periods. Milk yield showed the trend to increase in both treatment and post-treatment period by averaged 1.11 kg/d and 1.12 kg/d as compared with pretreated value 0.94 kg/d, respectively. The 4% fat corrected milk (FCM) was greater (P < 0.05) for the betaine supplemented animals (1.23 kg/d) than those of the controls (0.98 kg/d). The concentration of milk fat and lactose of betaine supplemented animals in treatment period were significantly (P < 0.05) higher than those of pretreatment and post-treatment periods. After betaine supplementation, the plasma K+ concentration decreased significantly (P < 0.05) during treatment and post-treatment periods. No statistically different were apparent for plasma and milk electrolytes concentrations, body fluid compartments for plasma volume, blood volume, extracellular fluid, intracellular fluid and total body water in both control and betaine supplemented animals. The arterial plasma concentration for acetate showed no significant increase by approximately 45% after betaine supplementation. The arterio-venous concentration difference of plasma acetate and the extraction ratio of acetate across the mammary gland in betaine supplemented animals were higher than those of the control animals. The present result suggested that the regulation of an increase in milk yield during betaine supplementation in late lactating crossbred Saanen goats is influenced more by the intramammary factors than by extramammary factors in association with the utilization of substrate for milk synthesis.
