Digestion site of starch from cereals and legumes in lactating dairy cows

Effects of forage and grain legume-based silages supplemented with faba bean meal or rapeseed expeller on lactational performance, nitrogen utilization, and plasma amino acids in dairy cows

The objective of this experiment was to investigate the effect of forage type [red clover (51%)-grass silage, i.e., RCG; vs. faba bean (66%)-grass silage, i.e., FBG] and concentrate type (faba bean, FB; vs. rapeseed expeller, RE) on lactational performance, milk composition and nitrogen (N) utilization in lactating dairy cows. Eight lactating multiparous Nordic Red cows were used in a replicated 4 × 4 Latin Square experiment, with 21-d periods, in a 2 × 2 factorial arrangement of treatments. The experimental treatments were as follows: (1) RCG with RE, (2) RCG with FB, (3) FBG with RE, and (4) FBG with FB. Inclusion rates of RE and FB were isonitrogenous. Crude protein contents of the experimental diets were 16.3, 15.9, 18.1, and 17.9% of dry matter, respectively. All diets included oats and barley and were fed ad libitum as total mixed rations with forage-to-concentrate ratio of 55:45. Dry matter intake and milk yield were recorded daily, and spot samples of urine, feces, and blood were collected at the end of each experimental period. Dry matter intake did not differ across diets, averaging 26.7 kg/d. Milk yield averaged 35.6 kg/d and was 1.1 kg/d greater for RCG versus FBG, and milk urea N concentration was lower for RCG compared with FBG. Milk yield was 2.2 kg/d and milk protein yield 66 g/d lower for FB versus RE. Nitrogen intake, urinary N, and urinary urea N excretions were lower, and milk N excretion tended to be lower for RCG compared with FBG. The proportion of the dietary N excreted as fecal N was larger in cows fed RCG than for those fed FBG, and the opposite was true for urinary N. We detected an interaction for milk N as percentage of N intake: it increased with RE compared with FB for RCG-based diet, but only a marginal increase was observed for FBG-based diet. Plasma concentration of His and Lys were lower for RCG than for FBG, whereas His tended to be greater and Lys lower for FB compared with RE. Further, plasma Met concentration was around 26% lower for FB than for RE. Of milk fatty acids, saturated fatty acids were decreased by RCG and increased by FB compared with FBG and RE, respectively, whereas monounsaturated fatty acids were increased by RCG versus FBG, and were lower for FB than for RE. In particular, 18:1n-9 concentration was lower for FB compared with RE. Polyunsaturated fatty acids, such as 18:2n-6 and 18:3n-3, were greater for RCG than for FBG, and 18:2n-6 was greater and 18:3n-3 was lower for FB versus RE. In addition, cis-9,trans-11 conjugated linoleic acid was lower for FB compared with RE. Faba bean whole-crop silage and faba bean meal have potential to be used as a part of dairy cow rations, but further research is needed to improve their N efficiency. Red clover-grass silage from a mixed sward, without inorganic N fertilizer input, combined with RE, resulted in the greatest N efficiency in the conditions of this experiment.

Substitution of soyabean meal by faba bean improves body weight, sperm production and testosterone concentration in mature Queue Fine de l'Ouest rams

The current study aimed at investigating the effects of partial or total substitution of soybean meal with faba bean on reproductive parameters of Queue Fine de l'Ouest rams. Eighteen adult rams (49.8 ± 3.7 kg and 2.4 ± 1.5 years old) were divided into three homogenous groups. Rams received oat hay ad libitum and 3 types of concentrate (33 g/BW^0.75) where soybean meal was the main protein source (SBM diet, n = 6), partially (50%, SBMFB diet, n = 6) or totally (100% FB diet, n = 6) substituted in nitrogen basis by local faba bean. The volume of ejaculate, sperm concentration and sperm mortality rate were measured weekly by collecting semen using an artificial vagina. Serial blood samples were collected 30 days and 120 days after the beginning of the experiment in order to assess plasma testosterone concentrations. The results showed that hay intake was affected (P < 0.05) by the nature of the nitrogen source incorporated (1032.3 ± 12.2; 1026.8 ± 56.6 and 972.8 ± 39.05 g DM/d for SBM, FB and SBMFB respectively. The average live weight of the rams increased from 49.8 ± 0.4 (week 1) to 57.3 ± 0.9 kg (week 17) without effect of the diet. A positive effect of faba bean incorporation in the concentrate was observed on ejaculate volume, concentration and spermatozoa production. All these parameters were significantly higher in SBMFB and FB groups than in SBM group (P < 0.05). The protein source did not affect the percentage of dead spermatozoa and the total abnormalities which were similar for the three diets (38.7; 35.8 and 38.1% for SBM; SBMFB and FB, respectively). The mean testosterone concentration was higher (P < 0.05) in rams fed with faba bean (1.7 ± 0.7 to 1.9 ± 0.7 ng/ml for the SBMFB and the FB groups respectively) than in rams fed SBM diet (1.06 ± 0.5 ng/ml). It was concluded that the substitution of soybean meal by faba bean improved the reproductive performance and did not affect sperm quality in Queue Fine de l'Ouest rams.

Diet Preference, Feed Efficiency and Expression of the Sodium-Dependent Glucose Transporter Isoform 1 and Sweet Taste Receptors in the Jejunum of Lambs Supplemented with Different Flavours

This study investigated the effect of dietary flavour supplements on the preference, feed efficiency and expression of the sweet taste receptor family 1 members 2 and 3 (T1R2 + T1R3), and sodium-glucose linked transporter 1 (SGLT1) genes in the lambs' small intestines. Eight, five-month-old, Israeli crossbred Assaf lambs were offered 16 different non-nutritive commercial flavours in rolled barley and ground corn. Capsicum and sucram were the most preferred non-aroma flavours (p = 0.020), while milky (p < 0.001) was the most preferred powder-aroma flavour. For the metabolic and relative gene expression study, eight lambs were randomly assigned to either sucram, capsicum, a mix containing sucram and capsicum at 1:1 ratio or no flavour for control in a 4 × 2 cross-over design. The total collection of urine (females only), faeces and refusals was carried out, and T1R2, T1R3 and SGLT1 relative gene expression evaluated from the proximal jejunum biopsies. Flavour had no significant effect on the feed intake (p = 0.934), but capsicum increased the average daily weight gain per metabolic body weight (p = 0.049). The T1R3 gene was expressed highest in the mix treatment (1.7; p = 0.005). Collectively, our findings indicate that flavours can be used to motivate feed acceptance and improve the weight gain in lambs.

Processed fava bean as a substitute for rapeseed meal with or without rumen-protected methionine supplement in grass silage-based dairy cow diets

Fava bean offers a sustainable home-grown protein source for dairy cows, but fava bean protein is extensively degraded in the rumen and has low Met concentration. We studied the effects of protein supplementation and source on milk production, rumen fermentation, N use, and mammary AA utilization. The treatments were unsupplemented control diet, and isonitrogenously given rapeseed meal (RSM), processed (dehulled, flaked, and heated) fava bean without (TFB) or with rumen-protected (RP) Met (TFB+). All diets consisted of 50% grass silage and 50% cereal-based concentrate including studied protein supplement. The control diet had 15% of crude protein and protein-supplemented diets 18%. Rumen-protected Met in TFB+ corresponded to 15 g/d of Met absorbed in the small intestine. Experimental design was a replicated 4 × 4 Latin square with 3-wk periods. The experiment was conducted using 12 multiparous mid-lactation Nordic Red cows, of which 4 were rumen cannulated. Protein supplementation increased dry matter intake (DMI), and milk (31.9 vs. 30.7 kg/d) and milk component yields. Substituting RSM with TFB or TFB+ decreased DMI and AA intake but increased starch intake. There were no differences in milk yield or composition between RSM diet and TFB diets. Rumen-protected Met did not affect DMI, or milk or milk component yields but increased milk protein concentration in comparison to TFB. There were no differences in rumen fermentation except for increased ammonium-N concentration with the protein-supplemented diets. Nitrogen-use efficiency for milk production was lower for the supplemented diets versus control diet but tended to be greater for TFB and TFB+ versus RSM. Protein supplementation increased plasma essential AA concentration but there were no differences between TFB diets and RSM. Rumen-protected Met clearly increased plasma Met concentration (30.8 vs. 18.2 µmol/L) but did not affect other AA. Absence of differences between RSM and TFB in milk production together with limited effects of RP Met suggest that TFB is a potential alternative protein source for dairy cattle.

Fava beans can substitute soybean meal and rapeseed meal as protein source in diets for lactating dairy cows

The effect of replacing mixtures of wheat and soybean meal and wheat and rapeseed meal by toasted fava beans, and the effect of toasting fava beans on feed intake, milk yield, and composition of milk and feces were investigated using 40 Holstein cows in each of two 4 × 4 Latin square design trials conducted simultaneously. In trial 1, the 4 treatment concentrates were untreated fava beans, toasted fava beans, 42% soybean meal + 58% rolled wheat, and a 21, 29, and 50% mix of soybean meal, rolled wheat, and toasted fava beans, respectively [on dry matter (DM) basis]. In trial 2, the 4 experimental treatments were untreated fava beans, toasted fava beans, 64% rapeseed meal + 36% rolled wheat, and a 32, 18, and 50% mix of rapeseed meal, rolled wheat, and toasted fava beans, respectively (on DM basis). In each trial, 16 primiparous and 24 multiparous cows were fed the treatment concentrates as part of a partial mixed ration, of which the forage consisted of 50% corn silage and 50% grass-clover silage. Substitution of soybean meal and wheat or rapeseed meal and wheat with toasted fava beans did not affect total DM intake, and no linear effects were observed on milk yield or energy-corrected milk (ECM) yield. However, in trial 2, a quadratic effect was observed on milk yield when substituting rapeseed meal and wheat with toasted fava beans. In both trials, substitution of soybean meal and wheat or rapeseed meal and wheat with toasted fava beans increased milk lactose concentration and decreased milk protein yield and concentration of protein in milk. In both trials, fecal concentration of starch increased linearly when substituting soybean meal and wheat or rapeseed meal and wheat with toasted fava beans. In trial 2, fecal concentration of P decreased when substituting rapeseed meal and wheat with toasted fava beans. In situ investigations showed increased rumen undegradable protein concentration and thereby increased estimated metabolizable protein supply when toasting fava beans. However, in both trials, milk protein yield and concentration decreased when cows were fed toasted compared with untreated fava beans. Furthermore, when cows were fed toasted compared with untreated fava beans in trial 1, milk yield, ECM yield, and nitrogen efficiency decreased. We conclude that toasted fava beans could substitute soybean meal and wheat or rapeseed meal and wheat with regard to ECM yield. However, milk protein yield decreased when substituting soybean meal and wheat or rapeseed meal and wheat with toasted fava beans. Compared with untreated fava beans, toasting had no positive effect on milk production and nitrogen efficiency.

Enteric methane emission and digestion in dairy cows fed wheat or molasses

The aim of this experiment was to measure enteric methane (CH₄) emission and its relation with rumen digestion in dairy cows fed diets rich in 1 of the 2 carbohydrate sources, starch or sugar. The rations were based on late first-cut grass-clover silage supplemented with wheat (Wh), NaOH-treated wheat (Wh+NaOH), sugar beet molasses (Mo), or sugar beet molasses with addition of sodium bicarbonate (Mo+Bic). Wheat and molasses made up 35% of dry matter in the 2 diets with molasses and wheat, respectively. Four cows fitted with ruminal, duodenal, and ileal canulae were used in a 4 × 4 Latin square design. Nutrient digestibility was measured using chromium oxide and titanium oxide as flow markers, and emissions of CH₄ and hydrogen were measured via open-circuit indirect calorimetry on 4 consecutive days. Data were analyzed using PROC MIXED of SAS (version 9.4; SAS Institute Inc., Cary, NC) with treatment and period as fixed effects and cow as random effect. Furthermore, orthogonal contrasts were calculated. The cows produced 32.5, 33.6, 36.2, and 35.1 L of CH₄/kg of dry matter intake (DMI) on diets Wh, Wh+NaOH, Mo, and Mo+Bic, respectively. The emission of CH₄ per day, per kilogram of DMI, and per kilogram of energy-corrected milk as well as daily hydrogen emission were higher on the Mo diet compared with the Wh diet. With the present inclusion of wheat and molasses in the diet, no effects of NaOH treatment of wheat or of sodium bicarbonate supplementation to the Mo diet could be demonstrated on CH₄ emission expressed per kilogram of DMI or per kilogram of energy-corrected milk. The duodenal flow of starch was higher when wheat was treated with NaOH. Under the conditions in the present experiment, ruminal NDF digestibility was not affected by carbohydrate source, NaOH treatment of wheat, or bicarbonate supplementation. Total volatile fatty acid concentration in the rumen and the proportions of acetate and propionate were not affected by carbohydrate source, NaOH treatment of wheat, or bicarbonate supplementation. Likewise, we could not show any influence of diet on microbial protein synthesis or efficiency of microbial protein synthesis expressed as grams of microbial protein synthesis per kilogram of true rumen-digested organic matter. We concluded that CH₄ emission was increased when wheat was replaced by molasses, whereas no effect of manipulating rumen fermentation by NaOH treatment of wheat or addition of bicarbonate to molasses could be found with a level of approximately 25% of dry matter from starch and sugar, respectively.

Short communication: Gelatinization and enzymatic hydrolysis characteristics relevant to digestion and analysis of glycogen granules isolated from ruminal protozoa

Glycogen is an α-glucan produced by rumen microbes from various feed carbohydrates. It may be digested ruminally or intestinally to provide nutrients. The physicochemical and enzymatic hydrolysis characteristics of microbial glycogen have not been described in detail, but do influence its conversion to absorbable nutrients in vivo, its nutritional comparability with plant starch sources, and its accurate analysis in vitro. The objectives of this study were to determine presence or absence of a gelatinization response and to describe enzymatic digestion characteristics of glycogen granules isolated from ruminal protozoa obtained from lactating dairy cows. Protozoal glycogen granules were determined to be 98.3% α-glucan. Granules displayed gelatinization, the breaking of hydrogen bonds between molecules or branches, at 65°C compared with purified wheat and corn starches, which initiated gelatinization at 50 and 65°C, respectively. Digestion of ungelatinized samples with amyloglucosidase for 2 h at 39°C showed approximately 3-fold greater hydrolysis to glucose for protozoal glycogen (25.2% of dry matter; DM) than for wheat (9.9% of DM) or corn (8.2% of DM) starches. Based on enzymatic digestion results, protozoal glycogen may be more readily digested than intact corn or wheat starches and should be gelatinized or the hydrogen bonds otherwise disrupted to allow more complete recovery in enzymatic analysis.

Starch sources and concentration in diet of dairy goats affected ruminal pH and fermentation, and inflammatory response

Corn and wheat grains are two starch sources with considerably different ruminal digestion rates, which may lead to differing lipopolysaccharide (LPS) release in both rumen and hindgut affecting animal production. The objectives of this study were to (1) investigate the effects of different ruminal and faecal LPS concentrations induced by starch source (corn vs wheat) and starch concentrations (low vs high) on DMI, ruminal pH, ruminal fermentation patterns, milk production, and inflammatory responses; and (2) evaluate the possible translocation site of LPS in dairy goats. Eight lactating dairy goats with ruminal cannulas were used in a replicated 4 × 4 Latin square design with 2 × 2 factorial arrangement of treatments. Each experimental period consisted of 24 days long including 21 days for adaption and 3 days for data and sample collection. The four treatment diets were: corn and wheat grain combined with low (LS) and high grain starch (HS). Goats were fed equal amounts of a total mixed ration twice daily at 0700 hours and 1900 hours. Replacing corn with wheat in goat diet led to longer (P &lt; 0.02) duration of ruminal pH &lt;5.6, higher ruminal LPS (P &lt; 0.05), but lower faecal LPS concentration. However, no differences between two grains in ruminal pH (mean, minimum and maximum), volatile fatty acids (VFA) and lactic acid concentration were observed. Goats fed HS diets had lower (P &lt; 0.01) ruminal pH and higher (P &lt; 0.01) ruminal concentrations of VFA and lactic acid, as well as higher (P &lt; 0.01) ruminal and faecal LPS concentrations. Starch source did not affect DMI, milk yield and milk components whereas feeding HS versus LS diet had higher milk yield, lactose yield and improved milk efficiency (P &lt; 0.05). Feeding wheat- versus corn-based diet showed only greater (P &lt; 0.05) concentration of toll-like receptor-4, whereas feeding the HS versus LS diet consistently increased blood concentrations of amyloid A, haptoglobin, LPS binding protein, and LPS (P &lt; 0.05). Analysis of Pearson correlation coefficients illustrated that the ruminal LPS concentration is more important than faecal LPS in inflammatory responses. In conclusion, replacing corn with wheat in lactating goat diet had negative impact on ruminal pH but little effects on fermentation characteristics and milk production. Increasing the dietary concentration of starch decreased ruminal pH status and thus increased risk of acidosis, whereas, feeding HS versus LS diets resulted in an improvement in milk yield, milk efficiency, and immunity response. Moreover, rumen acidosis induced by wheat based diet was accompanied with more severe inflammatory responses.

RNA-seq analysis of bovine adipose tissue in heifers fed diets differing in energy and protein content

Adipose tissue is no longer considered a mere energy reserve, but a metabolically and hormonally active organ strongly associated with the regulation of whole-body metabolism. Knowledge of adipose metabolic regulatory function is of great importance in cattle management, as it affects the efficiency and manner with which an animal converts feedstuff to milk, meat and fat. However, the molecular mechanisms regulating metabolism in bovine adipose tissue are still not fully elucidated. The emergence of next-generation sequencing technologies has facilitated the analysis of metabolic function and regulation at the global gene expression level. The aim of this study was to investigate the effect of diets differing in protein and energy density level on gene expression in adipose tissue of growing replacement dairy heifers using next-generation RNA sequencing (RNAseq). Norwegian Red heifers were fed either a high- or low-protein concentrate (HP/LP) and a high- or low-energy roughage (HE/LE) diet from 3 months of age until confirmed pregnancy to give four treatments (viz, HPHE, HPLE, LPHE, LPLE) with different growth profiles. Subcutaneous adipose tissue sampled at 12 months of age was analyzed for gene expression differences using RNAseq. The largest difference in gene expression was found between LPHE and LPLE heifers, for which 1092 genes were significantly differentially expressed, representing an up-regulation of mitochondrial function, lipid, carbohydrate and amino acid metabolism as well as changes in the antioxidant system in adipose tissue of LPHE heifers. Differences between HPHE and HPLE heifers were much smaller, and dominated by genes representing NAD biosynthesis, as was the significantly differentially expressed genes (DEG) common to both HE-LE contrasts. Differences between HP and LP groups within each energy treatment were minimal. This study emphasizes the importance of transcriptional regulation of adipose tissue energy metabolism, and identifies candidate genes for further studies on early-stage obesity and glucose load in dairy cattle.

Multi-Omic Biogeography of the Gastrointestinal Microbiota of a Pre-Weaned Lamb

The digestive functions of the pre-weaned lamb gastrointestinal tracts (GITs) have been the subject of much research in recent years, but the microbial and host functions underlying these complex processes remain largely unknown. Here, we undertook a proof-of-principle metaproteogenomic investigation on luminal and mucosal samples collected from 10 GITs of a 30-day-old pre-weaned lamb. We demonstrate that the analysis of the diverse ecological niches along the GITs can reveal microbiota composition and metabolic functions, although low amounts of microbial proteins could be identified in the small intestinal and mucosal samples. Our data suggest that a 30-day lamb has already developed mature microbial functions in the forestomachs, while the effect of the milky diet appears to be more evident in the remaining GITs. We also report the distribution and the relative abundance of the host functions, active at the GIT level, with a special focus on those involved in digestive processes. In conclusion, this pilot study supports the suitability of a metaproteogenomic approach to the characterization of microbial and host functions of the lamb GITs, opening the way to further studies aimed at investigating the impact of early dietary interventions on the GIT microbiota of small ruminants.

The Contribution of Mathematical Modeling to Understanding Dynamic Aspects of Rumen Metabolism

All mechanistic rumen models cover the main drivers of variation in rumen function, which are feed intake, the differences between feedstuffs and feeds in their intrinsic rumen degradation characteristics, and fractional outflow rate of fluid and particulate matter. Dynamic modeling approaches are best suited to the prediction of more nuanced responses in rumen metabolism, and represent the dynamics of the interactions between substrates and micro-organisms and inter-microbial interactions. The concepts of dynamics are discussed for the case of rumen starch digestion as influenced by starch intake rate and frequency of feed intake, and for the case of fermentation of fiber in the large intestine. Adding representations of new functional classes of micro-organisms (i.e., with new characteristics from the perspective of whole rumen function) in rumen models only delivers new insights if complemented by the dynamics of their interactions with other functional classes. Rumen fermentation conditions have to be represented due to their profound impact on the dynamics of substrate degradation and microbial metabolism. Although the importance of rumen pH is generally acknowledged, more emphasis is needed on predicting its variation as well as variation in the processes that underlie rumen fluid dynamics. The rumen wall has an important role in adapting to rapid changes in the rumen environment, clearing of volatile fatty acids (VFA), and maintaining rumen pH within limits. Dynamics of rumen wall epithelia and their role in VFA absorption needs to be better represented in models that aim to predict rumen responses across nutritional or physiological states. For a detailed prediction of rumen N balance there is merit in a dynamic modeling approach compared to the static approaches adopted in current protein evaluation systems. Improvement is needed on previous attempts to predict rumen VFA profiles, and this should be pursued by introducing factors that relate more to microbial metabolism. For rumen model construction, data on rumen microbiomes are preferably coupled with knowledge consolidated in rumen models instead of relying on correlations with rather general aspects of treatment or animal. This helps to prevent the disregard of basic principles and underlying mechanisms of whole rumen function.

In situ starch and crude protein degradation in the rumen and in vitro gas production kinetics of wheat genotypes

The objective of this study was to determine the variation of in situ ruminal degradation characteristics of dry matter (DM), crude protein (CP) and starch (ST), and to determine the effective degradation (ED) of wheat genotypes. Further, multivariate associations of these in situ values with their corresponding in vitro gas production (GP) kinetics and laboratory measurements were evaluated using correlation and multiple linear regression analyses. Grains of 20 genotypes of wheat were characterized by proximate constituents, amino acid (AA) composition and physical characteristics. Ruminal degradation kinetics were determined by in situ degradation of DM, CP and ST, and subsequent evaluation of in vitro GP relative to time courses. In situ and GP measurements were fitted to an exponential equation, and ED was calculated using passage rates in the rumen of 5%/h (ED5) and 8%/h (ED8). To predict ED8 of CP (EDCP8) and ST (EDST8), correlations were evaluated and stepwise multiple linear regression analyses were applied. Estimated degradation parameters varied considerably between wheat genotypes irrespective of the nutrient tested. Variance in a, b and c was not reflected in the variation of the ED, due to high degradation rates (c). The assumed passage rate also impacted estimation of the ED minimally. Estimated GP parameters varied only slightly among wheat genotypes. Nevertheless, regression models explained up to 80 and 99% of the variance in EDCP8 and EDST8, respectively, and associations between EDST8 and EDCP8 and chemical and physical characteristics of grains were detected. As ST is the primary nutrient in wheat grains and can comprise substantial portions of dairy rations, the total amount of ST as well as its ED in the rumen should be taken into account when wheat is incorporated into dairy rations. Conversely, variance in wheat grain CP degradation was very low and can largely be neglected in practical ration formulation for ruminants.

Estimation of the in situ degradation of the washout fraction of starch by using a modified in situ protocol and in vitro measurements

The in situ degradation of the washout fraction of starch in six feed ingredients (i.e. barley, faba beans, maize, oats, peas and wheat) was studied by using a modified in situ protocol and in vitro measurements. In comparison with the washing machine method, the modified protocol comprises a milder rinsing method to reduce particulate loss during rinsing. The modified method markedly reduced the average washout fraction of starch in these products from 0.333 to 0.042 g/g. Applying the modified rinsing method, the fractional degradation rate (k d ) of starch in barley, oats and wheat decreased from on average 0.327 to 0.144 h-1 whereas for faba beans, peas and maize no differences in k d were observed compared with the traditional washing machine rinsing. For barley, maize and wheat, the difference in non-fermented starch in the residue between both rinsing methods during the first 4 h of incubation increased, which indicates secondary particle loss. The average effective degradation of starch decreased from 0.761 to 0.572 g/g when using the new rinsing method and to 0.494 g/g when applying a correction for particulate matter loss during incubation. The in vitro k d of starch in the non-washout fraction did not differ from that in the total product. The calculated ratio between the k d of starch in the washout and non-washout fraction was on average 1.59 and varied between 0.96 for oats and 2.39 for maize. The fractional rate of gas production was significantly different between the total product and the non-washout fraction. For all products, except oats, this rate of gas production was larger for the total product compared with the non-washout fraction whereas for oats the opposite was observed. The rate of increase in gas production was, especially for grains, strongly correlated with the in vitro k d of starch. The results of the present study do not support the assumption used in several feed evaluation systems that the degradation of the washout fraction of starch in the rumen is much faster than that of the non-washout fraction.

Effects of rumen-escape starch and coarseness of ingredients in pelleted concentrates on performance and rumen wall characteristics of rosé veal calves

The objective was to study the effect of rumen-escape starch and coarseness of ingredients in pelleted concentrates on performance, carcass quality and rumen wall characteristics in rosé veal calf production. Two alternative concentrates (Coarse and Slow) were compared with a traditional (Control) concentrate. Control was based on finely ground ingredients, whereas in Coarse, the same ingredients were coarsely ground resulting in a mean particle size before pelleting of 1.5 in Coarse and 0.6 mm in Control. Slow compared with Control and Coarse contained finely ground sorghum and corn instead of barley and wheat which increased the amount of rumen-escape starch to 59 compared with 22 g/kg in Control and Coarse. All concentrates had the same total starch (362 g/kg), NDF (168 g/kg), CP (154 g/kg) and DE (15.5 MJ/kg DM) content and a pellet diameter of 3.5 to 4 mm. Use of an 'indicator of starch digestibility' method gave a value of 98.6% for Control and Coarse and 91.1% for Slow (P < 0.001). A total of 57 Holstein bull calves (n = 19 per treatment) were offered one of the three concentrates ad libitum from weaning (2½ months of age) to slaughter (<10 months of age). Concentrate intake was recorded individually. Barley straw was available ad libitum but intake was not recorded. Average daily gain (1.43 kg/day), concentrate conversion efficiency (3.7 kg DM concentrate/kg gain), LW at slaughter (386 kg), carcass weight (194 kg) and EUROP conformation (3.9) were not affected by type of concentrate (P > 0.05). Papillae length and shape evaluated in atrium ruminis and the cranial part of the ventral rumen sac at slaughter were not affected by type of concentrate (P > 0.05). Rumen wall characteristics showed degrees of plaque formation (i.e., papillary aggregation), hyperaemia and necrotic areas in all treatment groups, but with no general difference between type of concentrate (P > 0.05). Incidence of liver abscesses (LAs, 16%) was not affected by type of concentrate (P > 0.05). There were no differences in performance or rumen wall characteristics between liver-abscessed and non-abscessed calves. The results show a high level of production performance with the three types of pelleted concentrates and indicates that neither the more coarse ingredients nor the additional rumen-escape starch tested, when fed ad libitum, could improve rumen wall characteristics or reduce LAs of rosé veal calves.

Crude glycerol as glycogenic precursor in feed; effects on milk coagulation properties and metabolic profiles of dairy cows

As grain prices rise, the search for alternative glycogenic precursors in animal feed becomes increasingly important, and this study was conducted to determine if the replacement of starch with glycerol, as an alternative glycogenic precursor, affects the milk metabolic profile and milk coagulation ability, and therefore the quality of the milk. Eight primiparous mid-lactation Holstein cows were fed during a replicated 4 × 4 Latin square trial with four different isoenergetic rations: (1) control (T0) fed a total mixed ration (TMR) with barley meal; (2) group T1, decreased barley content, replaced isoenergetically with 1 kg crude glycerol; (3) group T2, the barley meal was replaced with 2 kg of crude glycerol; and (4) group T3 the barley meal was replaced with 3 kg of crude glycerol. Rumen, blood and milk samples were collected at the end of every 21-d treatment period. Rumen samples were analysed for proportion of total volatile fatty acid (VFA), blood samples for insulin and glucose, and milk for metabolites (e.g. citric-acid cycle compounds). The change in glycogenic precursors had a positive effect on rumen VFA proportions; the proportion of propionic acid increased (P < 0·001). Milk protein (P < 0·001) and curd firmness (P < 0·001) both increased. The increase in milk protein concentration may have been due to an increase in microbial protein. Regarding the milk metabolic profiles, different signals were positively associated with coagulation ability and change in the diet. Based on this study, changing the glycogenic precursor in animal diet in this way is possible, and may have no immediate deleterious consequences on milk quality or cow health. Indeed, there is evidence for benefits from this substitution.

Gluconeogenesis in dairy cows: the secret of making sweet milk from sour dough

Gluconeogenesis is a crucial process to support glucose homeostasis when nutritional supply with glucose is insufficient. Because ingested carbohydrates are efficiently fermented to short-chain fatty acids in the rumen, ruminants are required to meet the largest part of their glucose demand by de novo genesis after weaning. The qualitative difference to nonruminant species is that propionate originating from ruminal metabolism is the major substrate for gluconeogenesis. Disposal of propionate into gluconeogenesis via propionyl-CoA carboxylase, methylmalonyl-CoA mutase, and the cytosolic form of phosphoenolpyruvate carboxykinase (PEPCK) has a high metabolic priority and continues even if glucose is exogenously supplied. Gluconeogenesis is regulated at the transcriptional and several posttranscriptional levels and is under hormonal control (primarily insulin, glucagon, and growth hormone). Transcriptional regulation is relevant for regulating precursor entry into gluconeogenesis (propionate, alanine and other amino acids, lactate, and glycerol). Promoters of the bovine pyruvate carboxylase (PC) and PEPCK genes are directly controlled by metabolic products. The final steps decisive for glucose release (fructose 1,6-bisphosphatase and glucose 6-phosphatase) appear to be highly dependent on posttranscriptional regulation according to actual glucose status. Glucogenic precursor entry, together with hepatic glycogen dynamics, is mostly sufficient to meet the needs for hepatic glucose output except in high-producing dairy cows during the transition from the dry period to peak lactation. Lactating cows adapt to the increased glucose requirement for lactose production by mobilization of endogenous glucogenic substrates and increased hepatic PC expression. If these adaptations fail, lipid metabolism may be altered leading to fatty liver and ketosis. Increasing feed intake and provision of glucogenic precursors from the diet are important to ameliorate these disturbances. An improved understanding of the complex mechanisms underlying gluconeogenesis may further improve our options to enhance the postpartum health status of dairy cows.