D.S. Castagnino

Effects of dietary nitrogen levels and carbohydrate sources on apparent ruminal synthesis of some B vitamins in dairy cows

Effects of nitrogen level and carbohydrate source on apparent ruminal synthesis (ARS) of thiamin, riboflavin, niacin, vitamin B6, folates, and vitamin B12 were evaluated using 4 lactating Holstein cows distributed in a 4 × 4 Latin square design with treatments following a 2 × 2 factorial arrangement. Cows were fitted with cannulas in the rumen and proximal duodenum. The treatments were 2 N levels and 2 carbohydrate sources. The diet with the high N level provided 14% crude protein, calculated to meet 110% of the protein requirements and an adequate supply in rumen-degradable protein, whereas the diet with the low N level contained 11% crude protein, calculated to meet 80% of the protein requirements with a shortage in rumen-degradable protein. Carbohydrate source treatments differed by their nature (i.e., high in starch from barley, corn, and wheat, or high in fiber from soybean hulls and dehydrated beet pulp). All 4 diets were isoenergetic, based on corn silage, and had the same forage-to-concentrate ratio (60:40, dry matter basis). Duodenal flow was determined using YbCl3 as a marker. Each B-vitamin ARS was calculated as duodenal flow minus daily intake. The intake of several B vitamins varied among treatments, but because the animals consumed a similar amount of feed every day (average of 20 kg of dry matter/d) the difference was mostly due to vitamin content of each ingredient and their relative proportion in the diets. Decreasing N concentration in the diet reduced vitamin B6 duodenal flow and increased its apparent ruminal degradation. It also decreased duodenal flow and ARS of folates. The high-starch diets increased duodenal flow and ruminal balance of riboflavin, vitamin B6, and folates, whereas the high-fiber diets increased vitamin B12 ARS and duodenal flow. These effects on apparent synthesis are possibly due to changes in ruminal fermentation.

Effects of forage family on apparent ruminal synthesis of B vitamins in lactating dairy cows.

Effects of forage family (legume vs. grass) on apparent ruminal synthesis (ARS) and postruminal supply of B vitamins were evaluated in 2 experiments. Diets containing either alfalfa (AL) or orchardgrass (OG) silages as the sole forage were offered to ruminally and duodenally cannulated lactating Holstein cows in crossover design experiments. Experiment 1 compared diets containing AL and OG [~23% forage neutral detergent fiber (NDF) and ~27% total NDF] offered to 8 cows in two 15-d treatment periods. Experiment 2 compared diets containing AL and OG (~25% forage NDF and ~30% total NDF) offered to 13 cows in two 18-d treatment periods. Thiamin, riboflavin, niacin, vitamin B6, folates, and vitamin B12 were analyzed in feeds and duodenal digesta. Apparent ruminal synthesis was calculated as the duodenal flow of each vitamin minus its intake. Forage family affected B vitamin intakes, duodenal flow, and ARS. In both experiments, AL diets increased vitamin B6 and decreased folate intakes. In experiment 1, riboflavin and niacin intakes were greater with the OG diet, whereas in experiment 2 thiamin intake was greater but riboflavin intake was smaller with the OG diet. In spite of the low contribution of either silage to the dietary folate content, folate intake was greater with OG diets than AL due to the difference in soybean meal contribution between diets. Niacin and folate ARS were not affected by the forage family. Duodenal microbial nitrogen flow was positively correlated with ARS of riboflavin, niacin, vitamin B6, folates, and vitamin B12, but tended to be negatively correlated with thiamin ARS. Apparent ruminal synthesis of folates and vitamin B12 appear to be related to microbial biomass activity. Changes in nutrient composition of the diets likely affected the microbial population in the rumen and their B vitamin metabolism.

Particle length of silages affects apparent ruminal synthesis of B vitamins in lactating dairy cows

Effects of particle length of silages on apparent ruminal synthesis (ARS) and postruminal supply of B vitamins were evaluated in 2 feeding trials. Diets containing alfalfa (trial 1) or orchardgrass (trial 2) silages, chopped to either 19mm (long cut, LC) or 10mm (short cut, SC) theoretical particle length, as the sole forage were offered to ruminally and duodenally cannulated lactating Holstein cows in crossover design experiments. Forages chopped to a theoretical particle length of 19 and 10mm had mean particles sizes of 14.1 and 8.1mm, respectively, in trial 1, and 15.3 and 11.3mm, respectively, in trial 2. Trial 1 was conducted with 13 multiparous cows in two 19-d treatment periods; both diets contained approximately 20% forage neutral detergent fiber (NDF), 25% total NDF, and forage-to-concentrate ratios were approximately 47:53. Trial 2 was conducted with 15 cows in two 18-d treatment periods; both diets contained approximately 23% forage NDF, 28% total NDF, and had a forage-to-concentrate ratio of 50:50. Thiamine, riboflavin, niacin, vitamin B6, folates, and vitamin B12 were measured in feed and duodenal content. Daily ARS was calculated as the duodenal flow minus the intake. In trial 1, daily intake of individual B vitamins was increased with the LC diet, but ARS of thiamine, riboflavin, vitamin B6, and folates was reduced. In trial 2, except for folates, intakes of the other B vitamins were decreased with the LC diets, whereas ARS of riboflavin, niacin, and vitamin B6 was increased. Daily ARS of thiamine, riboflavin, niacin, and vitamin B6 were correlated negatively with their intake, suggesting that ruminal bacteria reduced their synthesis when dietary supply increased. Microbial activity could have also reduced degradation of thiamine, riboflavin, and niacin, which is supported by (1) the negative correlation between ARS of these vitamins and ruminal pH or microbial N duodenal flow; and (2) the positive correlation between ARS and ruminal concentrations of volatile fatty acids. Folate ARS followed the opposite correlation pattern. Nevertheless, in spite of differences in intake and ARS, with both forages, decreasing particle length of silages had limited effects on the amounts of B vitamins reaching the sites of absorption in the small intestine of dairy cows.

Evaluation of indigestible feed fractions as internal markers for predicting digestibility in lambs

The use of indigestible dry matter (iDM) and indigestible neutral detergent fiber (iNDF) as internal markers to estimate digestibility in lambs was evaluated. Data and samples were obtained from six independent digestion trials with lambs housed in metabolism cages given ad libitum different forage and concentrate feedstuffs. Indigestible residues were determined after 144 hours of in situ incubation of feed and faeces samples. Recovery rate varied from 64.8 to 108.5% for iDM, and from 49.5 to 67.9% for iNDF. As the marker ratio between marker concentration in the faeces and the feed was not corrected for fecal recovery, the large part of the estimated apparent organic matter digestibility (AOMD) of the experimental means were lower than the in vivo that obtained. As the marker ratio was corrected for fecal recovery of the marker, the AOMD means estimated using both markers were similar to the in vivo data in all experiments. As individual estimates, corrected for fecal recovery of the marker, were related to in vivo observations through regression analysis, the slope of the regression for iDM was not different from 1 whereas for iNDF, the slope was lower than 1. Individual AOMD values estimates using both markers, however, were poorly related to the in vivo observations (r2 varied from 0.60 to 0.63). Once corrected for fecal recovery, residual DM after 144 hours of in situ incubation is suitable for use as an internal marker to estimate mean diet digestibility consumed for a group of animals. However, individual estimates were not accurate to detect small differences in digestibility imposed by different treatments within an experiment.

Mineral Metabolism in Singleton and Twin-pregnant Dairy Goats

During pregnancy, the maternal body undergoes significant physiological changes. The present study assessed the changes on calcium (Ca), phosphorus (P), magnesium (Mg), sodium (Na) and potassium (K) metabolism in singleton and twin-pregnant dairy goats. The 42 goats used (49.5 kg±7.6 body weight [BW]) were assigned at random to treatments that were factorially arranged to account for 2 breeds (Oberhasli and Saanen), 2 pregnancy types (singleton and twin) and 3 gestation periods (80, 110, and 140 days). Digestibility trials were performed at 80, 110, and 140 days of gestation. Mineral retention during pregnancy was determined in the maternal body, femur, uterus, mammary gland, fetus and fetal fluid. Blood samples were taken during pregnancy before and after a meal, and Ca, P, Mg, Na, K ions and alkaline phosphatase activity determined in serum. Bone mineral density was determined in the right femur. Statistical analyses were performed using the SAS MIXED procedure. Dry matter intake decreased linearly up to 140 days of gestation. Maternal BW gain, and Ca, P, and Mg retention (g/kg) decreased linearly with the advance of gestation days. Macromineral retention in maternal body (g/kg) was greater in Oberhasli than Saanen goats, and their fetuses had higher Ca, P, and Mg deposition (mg/g). Mineral retention (mg/g) increased in fetuses according to pregnancy development, with no differences between singleton and twin pregnancy. In the mammary gland, the retention of all minerals (g) increased with the days of pregnancy. In conclusion, related to Ca, P, and Mg metabolism can be divided into two stages. Up to 80 days of gestation, was characterized by the preparation of the maternal body reserves for future mineral demands. From 80 days of gestation onward, was characterized by the transfer of maternal body reserves for fetal development and colostrum production. Na and K supply was provided by adjustments in endogenous excretion and an increase in intestinal absorption. Finally, mineral metabolism was specific to each genotype and, except for Na, was not affected by the number of fetuses.

Metabolizable protein and energy supply in lambs fed annual ryegrass ( Lolium multiflorum Lam.) supplemented with sources of protein and energy

Ten Polwarth × Texel lambs (26 ± 2·1 kg live weight (LW)), housed in metabolism cages and offered ryegrass (Lolium multiflorum) ad libitum, were used in a 5 x 5 Latin Square experiment to evaluate the effect of supplement type on digestion processes and on amino acid and energy supplies. Five of the 10 lambs were fitted with a rumen catheter and duodenal cannulae. Treatments included no supplement (control); 7 g/kg LW daily of cassava meal (Manihot esculenta, high-starch low-nitrogen (HS-LN)), cassava meal plus corn gluten meal (2:1, high-starch high-undegradable N (HS-UN)), cassava meal plus calcium caseinate (2·8:1, high-starch high-degradable N (HS-DN)) or corn gluten feed (low-starch high-degradable N (LS-DN)). Total intake of dry matter (DM), organic matter (OM) and N, as well as digestible OM intake were increased with HS-UN, HS-DN and LS-DN (P ≤ 0·050). Forage DM intake was reduced by HS-LN (P = 0·030). Apparent digestibility of DM and OM was increased by HS-LN and HS-DN (P ≤ 0·038). Digestibility of neutral detergent fibre (NDF) and OM true digestibility were similar for all treatments. Supplementation with HS-LN decreased duodenal flux of total N, amino acid N, ammonia N and feed residual N (P ≤ 0·023). None of the supplements affected rumen microbial protein entering the small intestine, whereas the efficiency of rumen microbial protein synthesis (EMPS) was reduced by HS-LN and HS-DN (P ≤ 0·036). Ruminal degradability of dietary N (RDN) was increased by HS-LN, HS-DN and LS-DN (P ≤ 0·050). In conclusion, supplementing lambs fed ryegrass with degradable or undegradable high-protein concentrate increased the amino acid supply without affecting the supply of digestible energy, regardless of either the starch content or the degree of ruminal degradability of the protein source. These results indicate that supplementation of ryegrass-based diets should include both starch and protein sources.

High-concentrate diets based on forages harvested at different maturity stages affect ruminal synthesis of B vitamins in lactating dairy cows.

Effects of plant maturity on apparent ruminal synthesis and post-ruminal supply of B vitamins were evaluated in two feeding trials. Diets containing alfalfa (Trial 1) or orchardgrass (Trial 2) silages harvested either (1) early cut, less mature (EC) or (2) late cut, more mature (LC) as the sole forage were offered to ruminally and duodenally cannulated lactating Holstein cows in crossover design experiments. In Trial 1, conducted with 16 cows (569±43 kg of empty BW (ruminal content removed) and 43.7±8.6 kg/day of 3.5% fat-corrected milk yield; mean±SD) in two 17-day treatment periods, both diets provided ~22% forage NDF and 27% total NDF, and the forage-to-concentrate ratios were 53 : 47 and 42 : 58 for EC and LC, respectively. In Trial 2, conducted with 13 cows (588±55 kg of empty BW and 43.7±7.7 kg/day of 3.5% fat-corrected milk yield; mean±SD) in two 18-day treatment periods, both diets provided ~25% forage NDF and 31% total NDF; the forage-to-concentrate ratios were 58 : 42 and 46 : 54 for EC and LC, respectively. Thiamin, riboflavin, niacin, vitamin B6, folates and vitamin B12 were measured in feed and duodenal content. Apparent ruminal synthesis was calculated as the duodenal flow minus the intake. Diets based on EC alfalfa decreased the amounts of thiamin, niacin and folates reaching the duodenum, whereas diets based on EC orchardgrass increased riboflavin duodenal flow. Daily apparent ruminal synthesis of thiamin, riboflavin, niacin and vitamin B6 were correlated negatively with their intake, suggesting a microbial regulation of their concentration in the rumen. Vitamin B12 apparent ruminal synthesis was correlated negatively with total volatile fatty acids concentration, but positively with ruminal pH and microbial N duodenal flow.

Changes in maternal body composition and metabolism of dairy goats during pregnancy

The objective of this study was to evaluate the mobilization of nutrients in goats of different gestation types and pregnancy stages. Forty-four Saanen and Oberhasli goats were studied. The goats of each breed and gestation type (single or twin) were slaughtered at different gestational ages (80, 110, and 140 days of pregnancy), forming a completely randomized design in a 2 × 3 × 2 factorial arrangement (two breeds, three gestational ages, and two types of pregnancy). The slaughter procedure involved separating the empty body, mammary glands, uterus with membranes and fetal fluid, and fetus(es). For the females slaughtered at 140 days of pregnancy, blood was collected to analyze metabolites and hormones every 15 days during gestation. The dry matter (DM) intake was lower in goats with twin pregnancies. The relative daily retention rate of the nutrients in the body was positive at 100 days of pregnancy but became negative at 140 days (-0.18±0.25 g DM kg-1 of maternal body d-1) and did not differ with breed or number of fetuses. Fetal growth in twin pregnancies was 66% higher than in single pregnancies. The highest levels of s-hydroxybutyrate and non-esterified fatty acids were observed beginning at 100 days of gestation. Serum total protein and albumin levels decreased after 125 days of gestation. Serum urea levels were reduced after 80 days of gestation. Plasma 17s-estradiol levels increased with the advance of pregnancy, and IGF-1 was highest between 60 and 80 days of gestation. The maternal metabolism throughout pregnancy does not vary with the type of pregnancy, and pregnant goats need greater nutritional intake during the final third of the gestational period regardless of the breed or type of pregnancy.

Apparent ruminal synthesis of B vitamins in lactating dairy cows fed diets with different forage-to-concentrate ratios

Effects of the forage-to-concentrate ratio on apparent ruminal synthesis of thiamine, riboflavin, niacin, vitamin B6, folates, and vitamin B12 were evaluated in an experiment using 14 ruminally and duodenally cannulated Holstein cows. The experiment was a crossover design with two 15-d treatment periods and a 14-d preliminary period in which cows were fed a diet intermediate in composition between the treatment diets. Treatments were diets containing low-forage (44.8% forage, 32.8% starch, 24.4% neutral detergent fiber) or high-forage (61.4% forage, 22.5% starch, 30.7% neutral detergent fiber) concentrations. Both diets were formulated with different proportions of the same ingredients. Concentrations of B vitamins were analyzed in feed and duodenal digesta. Apparent ruminal synthesis of each B vitamin was calculated as the duodenal flow minus the intake. The high-forage diet had the highest concentrations of riboflavin, niacin, vitamin B6, and folates, whereas the low-forage diet had the highest thiamine concentration. Vitamin B12 in the diets was under the level of detection. Consequently, despite a reduction in dry matter intake when the cows were fed the high-forage diet, increasing dietary forage concentration increased or tended to increase intakes of riboflavin, niacin, and vitamin B6 but reduced thiamine and folate intakes. Increasing dietary forage concentration reduced apparent ruminal degradation of thiamine and apparent ruminal synthesis of riboflavin, niacin, and folates and increased ruminal degradation of vitamin B6, but had no effect on ruminal synthesis of vitamin B12. As a consequence, increasing the forage-to-concentrate ratio had no effect on the amounts of thiamine, riboflavin, and vitamin B12 reaching the small intestine but decreased the amounts of niacin, vitamin B6, and folates available for absorption. Apparent ruminal syntheses of riboflavin, niacin, folates, and vitamin B12 were correlated positively with the amount of starch digested in the rumen and duodenal flow of microbial N, whereas these correlations were negative for thiamine. Apparent ruminal syntheses of thiamine and vitamin B6 were negatively correlated with their respective intakes, whereas folate intake was positively correlated with its synthesis in the rumen.

Ultrasonographic measurements of kidney fat thickness and Longissimus muscle area in predicting body composition of pregnant goats

Non-invasive methods for estimating body composition to monitor nutritional status in goats have been less studied. Therefore, this study estimated the body composition and fat depots of pregnant goats by using indirect measurements, such as bodyweight (BW) and ultrasound measurements of the Longissimus muscle area (LMA) and kidney fat thickness (KFT). Forty-three pregnant goats were slaughtered at 50, 80, 110 and 140 days of gestation to determine the gross energy and fat content in the body, as well as to obtain the mass of renal fat, omental fat and non-carcass fat. After the slaughter, the mass of fat depots was recorded and the whole body of the each animal was ground to take samples for determining gross energy (using a bomb calorimeter) and fat (Soxhlet extraction with ether). Animals were weighed, and ultrasonographic measurements were taken at the time of slaughter. The LMA and KFT measurements were taken between the 12th and 13th rib and after the 13th rib space, respectively, and these measurements were used to estimate total gross energy, body fat content and the renal fat, omental fat and non-carcass fat mass. Multiple regressions were performed using Proc mixed of SAS. No significant correlation was observed between gross energy and body fat composition, the number of fetuses or the days of gestation. LMA and BW were positively related to body fat and gross energy contents. KFT and BW showed a positive correlation with renal fat depots, omental fat content and non-carcass fat mass. The estimated models revealed that the total body fat increased from 15.6% to 20.8% of bodyweight from 50 to 140 days of gestation. This report is the first study using kidney fat thickness as a tool to predict fat depots in goats. LMA, BW and KFT measurements will enable the development of models to aid in the monitoring of the nutritional status of goats during pregnancy.