Theoretical turnover rate of the rumen liquid fraction in dairy cows and its relationship to feed intake, rumen fermentation, and milk production.

Ruminant animals are able to convert plant materials (grain and the human-indigestible portion of carbohydrates) to milk and meat. In this conversion, most of the plant materials are digested by rumen fermentation and are changed to short-chain fatty acids, microbial cells, and methane, which is released into the atmosphere. The relationships among feed, rumen fermentation, and milk production are poorly understood. Here we report a novel indicator of characteristics of rumen fermentation, theoretical turnover rate (TTOR) of the rumen liquid fraction. The TTOR was calculated from the presumed rumen volume (PRV) which is estimated by dividing the methane yield by the methane concentration of rumen fluid. The formula for the TTOR is: TTOR = PRV/body weight0.75 . Our present analyses confirm that the TTOR as an indicator is capable of connecting feed, rumen fermentation, and milk production, because dry matter intake/TTOR showed a strong correlation with milk yield/TTOR. In addition, the TTOR may be related to ruminal pH, as we observed that the ruminal pH decreased as the TTOR increased. We propose that the TTOR is a factor characterizing rumen fermentation and a good indicator of the productivity of ruminants and dysbiosis of the rumen microbiome.

Effect of nutrient levels during the far-off period on postpartum productivity in dairy cows.

The present study aimed to determine the effects of differing nutrient levels during the far-off period on postpartum metabolism and milk production in lactating cows. Twenty-six multiparous cows were assigned to three dietary treatments in the far-off period: a low-energy diet (L, n = 9, 80% intake of the total digestible nutrients requirement), a moderate-energy diet (M, n = 8, 105%) and a high-energy diet (H, n = 9, 130%). During the close-up period, all cows were provided with 105% intake. After parturition, all cows were fed a lactation diet. The BCS recovery was slow, and low milk yield was found in the H group. In the L group, BCS recovery was favorable after parturition, and lactation persistence was increased. The L group had low rumen endotoxin activity and a high initial ovulation rate after parturition. These findings indicate that a high-energy diet during the far-off period has a deleterious effect on milk production. In contrast, the restricted diet in the far-off period increased adaptability with respect to peri-parturition metabolic changes, improved the post-parturition nutritional state, and increased milk production. Furthermore, it suggests that the nutrient levels in the far-off period affect rumen endotoxin activity and reproductive function after parturition.

Effects of fatty acid-free bovine serum albumin and fetal calf serum supplementing repair cultures on pre- and post-warm viability of biopsied bovine embryos produced in vitro.

The objective of this study was to investigate the influence of fatty acid-free bovine serum albumin (BSA) or fetal calf serum (FCS) on the re-expansion of biopsied blastocysts and post-warm viability of subsequently vitrified embryos. Firstly, blastocysts produced in vitro were biopsied at Day 7 and cultured to allow repair in TCM199 with 0.3% BSA or 5% FCS for 24 h. The re-expansion rates and mean total numbers of cells of the re-expanded embryos after the repair culture with BSA were almost the same as that with FCS. Secondly, after biopsied embryos were similarly cultured for repair with BSA or FCS, re-expanded embryos were selected for vitrification. After warming and exposure to 0.5 M sucrose with 20% FCS in mPBS, the embryos were cultured in TCM199 with 5% FCS for 24 h. The re-expansion rate and mean total number of cells in re-expanded blastocysts in the BSA treatment group (97.4 +/- 2.9% and 106 +/- 42) was significantly higher than that in the FCS treatment group (51.6 +/- 9.1% and 61 +/- 38), respectively (P<0.05 and P<0.01). In conclusion, both FCS and BSA supplementation can be useful for repairing cultures of bovine biopsied blastocysts; but, compared with BSA supplementation, FCS supplementation during repair culture reduces the post-warm viability of biopsied and subsequently vitrified embryos.