Qiuling Hou

Effects of graded removal of lysine from an intravenously infused amino acid mixture on lactation performance and mammary amino acid metabolism in lactating goats

To investigate responses of milk protein synthesis and mammary AA metabolism to a graded decrease of postruminal Lys supply, 4 lactating goats fitted with jugular vein, mammary vein, and carotid artery catheters and transonic blood flow detectors on the external pudic artery were used in a 4 × 4 Latin square experiment. Goats were fasted for 24 h and then received a 9-h intravenous infusion of an AA mixture plus glucose. Milk yield was recorded and samples were taken in h 2 to 8 of the infusion period; a mammary biopsy was performed in the last hour. Treatments were graded decrease of lysine content in the infusate to 100 (complete), 60, 30, or 0% as in casein. Lysine-removed infusions linearly decreased milk yield, tended to decrease lactose yield, and tended to increase milk fat to protein ratio. Milk protein content and yield were linearly decreased by graded Lys deficiency. Mammary Lys uptake was concomitantly decreased, but linear regression analysis found no significant relationship between mammary Lys uptake and milk protein yield. Treatments had no effects on phosphorylation levels of the downstream proteins measured in the mammalian target or rapamycin pathway except for a tended quadratic effect on that of eukaryotic initiation factor 2, which was increased and then decreased by graded Lys deficiency. Removal of Lys from the infusate linearly increased circulating glucagon and glucose. Removal of Lys from the infusate linearly decreased arterial and venous concentrations of Lys. Treatments also had a significant quadratic effect on venous Lys, suggesting mechanisms to stabilize circulating Lys at a certain range. The 2 infusions partially removing Lys resulted in a similar 20% decrease, whereas the 0% Lys infusion resulted in an abrupt 70% decrease in mammary Lys uptake compared with that of the full-AA mixture infusion. Consistent with the abrupt decrease, mammary Lys uptake-to-output ratio decreased from 2.2 to 0.92, suggesting catabolism of Lys in the mammary gland could be completely prevented when the animal faced severe Lys deficiency. Mammary blood flow was linearly increased, consistent with the linearly increased circulating nitric oxide by graded Lys deficiency, indicating mechanisms to ensure the priority of the mammary gland in acquiring AA for milk protein synthesis. Infusions with Lys removed increased mammary clearance rate of Lys numerically by 2 to 3 fold. In conclusion, the decreased milk protein yield by graded Lys deficiency was mainly a result of the varied physiological status, as indicated by the elevated circulating glucagon and glucose, rather than a result of the decreased mammary Lys uptake or depressed signals in the mTOR pathway. Mechanisms of Lys deficiency to promote glucagon secretion and mammary blood flow and glucagon to depress milk protein synthesis need to be clarified by future studies.

High-production dairy cattle exhibit different rumen and fecal bacterial community and rumen metabolite profile than low-production cattle

Our aim was to simultaneously investigate the gut bacteria typical characteristic and conduct rumen metabolites profiling of high production dairy cows when compared to low‐production dairy cows. The bacterial differences in rumen fluid and feces were identified by 16S rDNA gene sequencing. The metabolite differences were identified by metabolomics profiling with liquid chromatography mass spectrometry (LC‐MS). The results indicated that the high‐production dairy cows presented a lower rumen bacterial richness and species evenness when compared to low‐production dairy cows. At the phylum level, the high‐production cows increased the abundance of Proteobacteria and decreased the abundance of Bacteroidetes, SR1, Verrucomicrobia, Euryarchaeota, Planctomycetes, Synergistetes, and Chloroflexi significantly (p < 0.05). At the genus level, the rumen fluid of the high‐production group was significantly enriched for Butyrivibrio, Lachnospira, and Dialister (p < 0.05). Meanwhile, rumen fluid of high‐production group was depleted for Prevotella, Succiniclasticum, Ruminococcu, Coprococcus,YRC22, CF231, 02d06, Anaeroplasma, Selenomonas, and Ruminobacter significantly (p < 0.05). A total of 92 discriminant metabolites were identified between high‐production cows and low‐production cows. Compared to rumen fluid of low‐production dairy cows, 10 differential metabolites were found up‐regulated in rumen fluid of high‐production dairy cows, including 6alpha‐Fluoropregn‐4‐ene‐3,20‐dione, 3‐Octaprenyl‐4‐hydroxybenzoate, disopyramide, compound III(S), 1,2‐Dimyristyl‐sn‐glycerol, 7,10,13,16‐Docosatetraenoic acid, ferrous lactate, 6‐Deoxyerythronolide B, vitamin D2, L‐Olivosyl‐oleandolide. The remaining differential metabolites were found down‐regulated obviously in high‐production cows. Metabolic pathway analyses indicated that most increased abundances of rumen fluid metabolites of high‐yield cows were related to metabolic pathways involving biosynthesis of unsaturated fatty acids, steroid biosynthesis, ubiquinone and other terpenoid‐quinone biosynthesis. Most down‐regulated metabolic pathways were relevant to nucleotide metabolism, energy metabolism, lipid metabolism and biosynthesis of some antibiotics.

Effect of hay supplementation timing on rumen microbiota in suckling calves

An animal feeding trial was conducted on 18 seven‐day‐old Holstein dairy bull calves weighing 42 ± 3 kg each. Calves were randomly assigned into three groups (n = 6 each). The dietary treatments were as follows: (1) milk and starter for the control group (MS), (2) supplementation of oat hay from week 2 on the basis of milk and starter (MSO2), and (3) supplementation of oat hay from week 6 on the basis of milk and starter (MSO6). All animals were fed starter and oat hay ad libitum. The major phyla in the different groups of rumen fluid included Firmicutes, Actinobacteria, Bacteroidetes, Proteobacteria, and Euryarchaeota. The major genera were identified, and major genera proportions in the three groups were as follows: Methanobrevibacter (Euryarchaeota), 2.1%, 1.7%, and 2.1%; Olsenella (Actinobacteria), 23.9%, 17.7%, and 12.8%; Prevotella (Bacteroidetes), 10.5%, 16.5%, and 19.2%; Dialister (Firmicutes), 3.3%, 4.1%, and 2.8%; Succiniclasticum (Firmicutes), 3.8%, 4.7%, and 9.2%; and Sharpea (Firmicutes), 0.4%, 2.5%, and 0.2%, respectively. There were no significant differences in the various phyla among the three groups (p > .05). The results showed that calves hay supplementation time did not affect the diversity of the rumen microbiota in the suckling calves. However, the hay supplementation altered the proportion of the various microbial populations, supplementation of oat hay from week 2 on the basis of milk and starter could improve calves rumen pH.

Gastrointestinal Tract Development in Unweaned Calves Feeding Different Amounts of Milk and Different Starters

This study was conducted to determine the effect of different starter diets and different amounts of milk on growth performance and gastrointestinal tract development in unweaned calves. 16 calves were assigned to 4 groups, 4 calves in each group. These four groups received the following treatments respectively: 1) high milk (6 L) + low starch (21%), high NDF (28%), high molasses (10%) starter (HMLS group); 2) high milk (6L) + high starch (40%), low NDF (14%), low molasses (5%) starter (HMHS group); 3) low milk (3 L) + low starch (21%), high NDF (28%), high molasses (10%) starter (LMLS group); 4) low milk (3 L) + high starch (40%), low NDF (14%), low molasses (5%) starter (LMHS group). The trial was of 2 × 2 factorial design. All calves had free access to hay and water. Results showed that the low milk allowance increased calf concentrate dry matter intake (DMI) and total DMI, reduced body height at 4 weeks of age, reduced heart girth at 6 weeks of age (P < 0.05). The low milk allowance increased complex stomach full weight, reticulorumen full weight, and the percentages of stomach full weight and reticulorumen full weight over body weight (P < 0.05). The low starch, high fiber, high molasses starters reduced the complex stomach full weight, the proportion of the complex stomach empty weight over body weight, reticulorumen empty weight, abomasum full weight, the proportion of abomasum empty weight over body weight and reticulorumen volume (P < 0.05). The low milk allowance increased calf intestine length, small intestine full weight, the proportion of small intestine full weight over body weight, but reduced the jejunum villus width (P < 0.05), increased ruminal pH (P < 0.05). The low milk allowance reduced papilla length in rumen anterior ventral blind sac, but increased papilla length in the posterior ventral sac (P < 0.05).

Effect of initial time of forage supply on growth and rumen development in preweaning calves

To determine the effects of the initial timing of forage supply on growth, ruminal fermentation parameters and rumen development in preweaning calves, 18 7-day-old Holstein calves of 42 ± 3 kg were randomly divided into three treatment groups. The dietary treatments were (1) milk and commercial starter diet (MS) control, (2) milk and starter diet supplemented with oat hay at 2 weeks (MSO2), and (3) milk and starter diet supplemented with oat hay at 6 weeks (MSO6). Starter feed and oat hay were provided ad libitum, and 2 L of milk was provided twice daily. Samples were collected at 64 days of age. Supplementing with hay increased the dry-matter intake; P 0.05). The concentrations of serum glucose (P = 0.07) and β-hydroxybutyric acid; P < 0.05) were lower in the MSO6 group than in the MS and MSO2 groups. Rumination time was longer, and time spent on non-nutritive oral behaviour (such as e.g. licking surfaces, tongue rolling, wood-shaving consumption) was lower for hay-supplemented calves than for the control (P < 0.05). Although ruminal pH of hay-supplemented calves was significantly higher than that of the control, total rumen fluid volatile fatty acid concentrations were not significantly different among treatments. Calves in the MSO2 group had a smaller ratio of empty weight to slaughter weight (P < 0.05) and a larger total digestive tract weight (P < 0.05); the empty gastrointestinal tract weights were similar among the three treatments, suggesting that MSO2 calf weight gain may have resulted from intestinal chyme accumulation. Compared with the control, hay-supplemented calves had reduced rumen papilla width and epithelium thickness (P < 0.05), and no discernable plaque formation. Hay supplementation in the diet of preweaning calves improved the overall dry-matter intake, improved rumination, reduced non-nutritive oral behaviours, improved rumen pH, and ensured healthy rumen development; furthermore, productivity and rumen development were better in calves supplemented with hay from the second week.