Effect of weaning age on growth performance, feed efficiency, nutrient digestibility and blood-biochemical parameters in Droughtmaster crossbred beef calves.

OBJECTIVE: The objective of this study was to determine the effect of weaning age on intake, performance, nutrition metabolism and serum parameters of beef calves. METHODS: Sixty Droughtmaster crossbred calves were assigned to 5 groups with 12 calves in each group. The calves in control group remained with the dams till the 22-week age, while the calves weaned at 28 d (4 wk), 42 d (6 wk), 56 d (8 wk), and 70 d (10 wk) of age were sent to group 4 wk, group 6 wk, group 8 wk, and group 10 wk, respectively, and then were fed on milk replacer till the 22-week age. Feed intake and body weight and size were record and blood metabolites were measured. And 24 calves of them (6 in each group) were picked randomly for digestion and metabolism trail. Feed, feces and urine sample were taken and measured. RESULTS: Dry matter intake of calves in group 4 wk was significantly lower than those in the remaining groups from wk 17 to 22 (p<0.05). Feed efficiency of the calves was higher in groups 4 wk and 6 wk than those in groups 8 wk and 10 wk from 11 to 13 wk (p<0.05), and calves had higher feed efficiency in group 4 wk, group 6 wk, and group 8 wk than those in group 10 wk from wk 14 to wk 22. Calves in group 4 wk and 6 wk had lower body weight than group 8 wk and group 10 wk and control group at 10-week age (p<0.05) and 13-week age (p<0.05), and calves in group 6 wk had no significant difference in body weight with control group, group 8 wk and 10 wk (p>0.05) but was higher than that of group 4 wk (p<0.05). Calves in group 6 wk had higher final body weight and total gain than group 4 wk, but no difference of total gain with that of groups 8 wk, 10 wk, and control group. And weaning calves at 6-week age brought higher feed efficiency and average daily gain from wk 14 to wk 22, and higher dry matter and organic matter digestibility at 21 wk. CONCLUSION: It is concluded that the weaning of calves at 6 weeks of age gave positive results.

Dietary supplementation with mulberry leaf flavonoids inhibits methanogenesis in sheep.

The effects of flavonoids on methanogenesis and microbial flora in Dorper × thin-tailed Han crossbred ewes were evaluated in two experiments. To investigate the effects of flavonoids on nutrient digestibility and nitrogen balance, 18 ewes (60.0 ± 1.73 kg body weight (BW)) were allotted to two dietary treatments in experiment one, a control diet and the control diet supplemented with flavonoids (2 g/head/day). In experiment two, the effects of supplementary flavonoids on ruminal fermentation and microbial flora were investigated using quantitative polymerase chain reaction with six ewes (67.2 ± 0.79 kg BW) with ruminal cannula assigned to the identical dietary treatments used in experiment one. Supplementary flavonoids improved the apparent digestibility of nitrogen (N, P < 0.001) and neutral detergent fibre (NDF, P = 0.024) and decreased daily CH4 output (P < 0.001). The ruminal pH (P = 0.638) and ammonia (P = 0.690) were not affected by supplementary flavonoids, whereas the total volatile fatty acid (VFA) content increased (P = 0.037). Supplementary flavonoids decreased ruminal populations of protozoans (P = 0.002) and methanogens (P < 0.001) and increased the populations of Fibrobacter succinogenes (P = 0.016). In conclusion, flavonoids improved the digestibility of organic matter and reduced CH4 output by inhibiting the populations of microbes involved in methanogenesis.

Effect of Dietary Concentrate:forage Ratios and Undegraded Dietary Protein on Nitrogen Balance and Urinary Excretion of Purine Derivatives in Dorper×thin-tailed Han Crossbred Lambs.

THIS STUDY AIMED TO INVESTIGATE DIETARY CONCENTRATE: forage ratios (C:F) and undegraded dietary protein (UDP) on nitrogen balance and urinary excretion of purine derivatives (PD) in lambs. Four Dorper×thin-tailed Han crossbred castrated lambs with 62.3±1.9 kg body weight at 10 months of age were randomly assigned to four dietary treatments in a 2×2 factorial arrangement of two levels of C:F (40:60 and 60:40) and two levels of UDP (35% and 50% of CP), according to a complete 4×4 Latin-square design. Each experimental period lasted for 19 d. After a 7-d adaptation period, lambs were moved into individual metabolism crates for 12 d including 7 d of adaption and 5 d of metabolism trial. During the metabolism trial, total urine was collected for 24 h and spot urine samples were also collected at different times. Urinary PD was measured using a colorimetric method and creatinine was measured using an automated analyzer. Intake of dry matter (DM) (p<0.01) and organic matter (OM) (p<0.01) increased as the level of UDP decreased. Fecal N was not affected by dietary treatment (p>0.05) while urinary N increased as the level of UDP decreased (p<0.05), but decreased as dietary C:F increased (p<0.05). Nitrogen retention increased as dietary C:F increased (p<0.05). As dietary C:F increased, urinary excretion of PD increased (p<0.05), but was not affected by dietary UDP (p>0.05) or interaction between dietary treatments (p>0.05). Daily excretion of creatinine was not affected by dietary treatments (p<0.05), with an average value of 0.334±0.005 mmol/kg BW(0.75). A linear correlation was found between total PD excretion and PDC index (R(2) = 0.93). Concentrations of creatinine and PDC index in spot urine were unaffected by sampling time (p>0.05) and a good correlation was found between the PDC index (average value of three times) of spot urine and daily excretion of PD (R(2) = 0.88). These results suggest that for animals fed ad libitum, the PDC index in spot urine is effective to predict daily excretion of PD. In order to improve the accuracy of the spot sampling technique, an appropriate lag phase between the time of feeding and sampling should be determined so that the sampling time can coincide with the peak concentration of PD in the urine.