Effects of rumen-protected folic acid addition in maternal and post-weaning diets on growth performance, total tract digestibility, ruminal fermentation and blood metabolites in lambs

This study was performed to investigate the influence of maternal and post-weaning rumenprotected folic acid (RPFA) addition on growth performance, total tract digestibility, rumen fermentation parameters and blood metabolites of lambs. Sixty-six Hu lambs (50 +/- 4.3 days of age and 16.4 +/- 3.84 kg of body weight [BW], mean +/- SD) from 120 Hu ewes (24 +/- 4.2 months of age and 44.6 +/- 5.43 kg of BW) were selected based on litter size, sex, BW and maternal diets and then assigned to six groups using a randomized block experimental design in a 3 x 2 factorial arrangement. The first factor was supplementary level of RPFA in the maternal diets and the different treatments included 0 mg (M0F), 16 mg (M16 F) and 32 mg (M32 F) FA per kg dry matter (DM). The second factor was the RPFA addition level in the offspring diets with 0 mg [OC] and 4.0 mg [OF] FA per kg DM. Lambs were fed a total mixed ration with a roughage-to-concentrate ratio of 50:50 on a DM basis. Average daily gain (ADG) of pre-weaning lambs showed a quadratic increase in response to RPFA added in the maternal diets. After weaning, dry matter intake was not affected by treatments. The ADG increased and the feed conversion ratio (FCR) decreased by lamb RPFA addition. Total tract digestibility of DM, organic matter and crude protein was higher for OF than for OC, and total tract digestibility of ether extract and neutral detergent fibre increased with maternal RPFA addition. The ruminal pH decreased, whereas total volatile fatty acid levels increased with maternal RPFA addition. The acetate to propionate ratio was elevated with maternal and/or lamb RPFA addition. Activities of amylase, trypsin, chymotrypsin and lipase in the intestinal chyme also increased with maternal RPFA addition. Concentrations of blood glucose, albumin, total protein, very low-density lipoprotein (VLDL), folate, growth hormone and insulin-like growth factor-1 (IGF-1) were greater for OF than for OC. Similarly, blood glucose, high density lipoprotein cholesterol, VLDL, folate and IGF-1 were elevated with maternal RPFA addition. These results indicate that addition of RPFA to the maternal and/or lamb diets promoted growth performance of the lambs by improving ruminal fermentation, intestinal enzymes activity, total tract digestibility and hormone secretion.