An attempt to define the sodium requirements of lactating dairy cows in a tropical environment

BACKGROUND: Lactating dairy cattle in the tropics may require more sodium (Na) owing to the hot and humid climatic conditions. It is unknown whether the current recommendations on Na for lactating cows can be quantitatively used in tropical countries. This study attempted to define the Na requirement of lactating dairy cows under tropical conditions by measuring Na levels in saliva, milk and faeces. RESULTS: The concentrations of Na and potassium (K) in milk, faeces and serum were not affected by dietary treatments. The amount of Na absorbed by cows fed the basal (low-Na) diet containing 0.4 g Na kg-1 dry matter (DM) was equal to the amount of Na lost in the milk, showing that these animals were fed an Na-deficient ration. This observation was corroborated by salivary Na and K levels, with the cows on the low-Na diet having salivary Na concentrations below 120 mmol L-1 in combination with salivary K concentrations above 20 mmol L-1 (P <0.05). CONCLUSION: Consumption of a daily ration formulated to contain the current Na requirement set by the NRC appears to provide too much Na for lactating cows under tropical conditions. A tentative value of 1.2 g kg-1 DM is proposed as the Na requirement for dairy cows under tropical conditions. Copyright © 2011 Society of Chemical Industr

Effect of dry period length on rumen adaptation in dairy cows

The objective of this study was to evaluate the effect of length of dry period on rumen papillae dimensions of dairy cows around parturition. Twelve rumen-cannulated Holstein dairy cows were assigned to a dry period length of 60 (G60), 30 (G30) or 0 (G0) days. The experiment started 60 d before expected calving date and lasted until wk 8 postpartum for each individual cow. Cows received ad libitum forage mixtures of corn silage, grass silage and straw (containing 12% CP, 5.3 MJ NEL/kg DM for dry cows and 15% CP, 6.4 MJ NEL/kg DM for lactating cows). Concentrates were fed individually starting 10 d antepartum with 1.0 kg/d, gradually increasing up to 8.5 kg/d at d17 postpartum. Milk yield and DMI were recorded daily. The rumen contents of each cow were evacuated at wk-9, wk-6, wk-2, d3, d7, d14, d28 and d56 relative to parturition. At each time, biopsies were taken to determine papillae dimensions at 3 locations: the right dorsal sac cranially of the dorsal coronary groove (DS), the right wall of the caudodorsal blind sac (DB) and the ventral wall of the caudoventral blind sac (VB). Treatment effects were tested by mixed model analysis using REML procedure. Data are presented as means ± SE. Mean DMI postpartum was 21.2, 22.2 and 23.7 (±0.6 kg/d) for G60, G0 and G30 respectively (P <0.05). Average daily milk yield postpartum was significantly lower for G0 (P <0.05) compared with G30 or G60 (35.1 vs. 41.4 and 41.8 ± 3.1 kg/d, respectively). For cows with a dry period (G30 and G60), papillae surface area decreased prepartum (P <0.05). More importantly, during the first 2 weeks postpartum the papillae growth was significantly delayed for G60 compared with G30; mean papilla surface was 42.5, 58.6 and 60.6 (±7.1, P <0.05) mm2 for G60, G30 and G0 respectively. Irrespective of treatment, rumen papillae were largest at VB and smallest at DS and papilla surface increased approximately 50% postpartum (P <0.05). In conclusion, a shortened dry period of 30 vs. 60 d increases papillae surface in the first weeks of lactation and herewith may improve absorption capacity of volatile fatty acids, without a negative effect on milk yield as found with 0 d dry

Changes in ruminal volatile fatty acid production and absorption rate during the dry period and early lactation as affected by rate of increase of concentrate allowance

The aim of the present experiment was to study changes in volatile fatty acid (VFA) production using an isotope dilution technique, and changes in VFA fractional absorption rate (k aVFA) using a buffer incubation technique (BIT) during the dry period and early lactation, as affected by the postpartum (pp) rate of increase of concentrate allowance. The current results are complementary to previously reported changes on rumen papillae morphology from the same experiment. From 50 d antepartum to 80 d pp, VFA production rate was measured 5 times and k aVFA was measured 10 times in 12 rumen-cannulated Holstein Friesian cows. Cows had free access to a mixed ration, consisting of grass and corn silage, soybean meal, and (dry period only) chopped straw. Treatment consisted of either a rapid (RAP; 1.0 kg of DM/d; n = 6) or gradual (GRAD; 0.25 kg of DM/d; n = 6) increase of concentrate allowance (up to 10.9 kg of DM/d), starting at 4 d pp, aimed at creating a contrast in rumen-fermentable organic matter intake. For the BIT, rumen contents were evacuated, the rumen washed, and a standardized buffer fluid introduced [120 mM VFA, 60% acetic (Ac), 25% propionic (Pr), and 15% butyric (Bu) acid; pH 5.9 and Co-EDTA as fluid passage marker]. For the isotope dilution technique, a pulse-dose of 13C-labeled Ac, Pr, and Bu and Co-EDTA as fluid passage marker was infused. The rate of total VFA production was similar between treatments and was 2 times higher during the lactation (114 mol/d) than the dry period (53 mol/d). Although papillae surface area at 16, 30, and 44 d pp was greater in RAP than GRAD, Bu and Ac production at these days did not differ between RAP and GRAD, whereas at 16 d pp RAP produced more Pr than GRAD. These results provide little support for the particular proliferative effects of Bu on papillae surface area. Similar to developments in papillae surface area in the dry period and early lactation, the k aVFA (per hour), measured using the BIT, decreased from 0.45 (Ac), 0.53 (Pr) and 0.56 (Bu) at 50 d antepartum to 0.28 (Ac), 0.34 (Pr) and 0.38 (Bu) at 3 d pp. Thereafter, k aVFA (/h) rapidly increased up to 0.67 (Ac), 0.79 (Pr), and 0.79 (Bu) at 80 d pp. Although papillae surface area was greater at 16, 30, and 44 d pp in RAP than GRAD, no differences in k aVFA between RAP and GRAD were observed during these days showing papillae surface area is not the limiting factor for k aVFA during early pp adaptation

Koperdeficiëntie bij schapen (kruising texelaar) behandeld met het voeren van koeienbrok

Six Texel-crossbred sheep, from a flock with a history of a dull appearance and mild diarrhea, were presented to the faculty of veterinary medicine (University of Utrecht). The clinical signs were found to be related to Copper (Cu) deficiency as indicated by low hepatic Cu values. It was decided to treat the animals by feeding them concentrates specifically formulated for dairy cows because such concentrates have a rather high Cu content compared to concentrates designed for sheep. Sheep Cu status was monitored by measuring liver Cu concentrations. Current results indicate the potential of feeding cow concentrate as a practical method to treat Cu deficiency in Texel-crossbred sheep. In contrast to hepatic Cu concentrations, serum Ceruloplasmin concentration (Cp) values did not respond to the treatment thereby indicating that serum Cp is inferior to evaluate Cu status in sheep compared to liver Cu measurements