Dietary Nonstructural Carbohydrates Research Articles

Dietary nonstructural carbohydrate affects mare milk production and composition

Recent interest has focused on the advantage of intensely handling young horses, as a good tool for improving emotional reactivity and thence trainability. Its effectiveness remains controversial, suggesting it might depend on the right timeframe to do so. The present study aimed to evaluate the effects of 3-handling sessions in foals, during eventual optimal periods − the day of birth (2-3 h after it) and the day after weaning − to be compared to handling in an unspecific period (at 50 ± 7 days old), or no handling. Lusitano breed foals (n = 50) were divided into five experimental groups with three being submitted to handling (consisting in desensitization, socialization and sensitization): at birth (Imp-H), at weaning (Wean-H), or at 50 ± 7 days old (Ex-H); and two not-handled groups: one not-handled and submitted to a 4-sessions training schedule (Not-H); and another left undisturbed (Control) until the end of the study (that finished when the foals reached 12 ± 1 months old). Training, consisted in four 12-min sessions, where foals were taught to be lead-in-hand finishing with exhibition of trot. Handling effects, regarding skills to face new situations and environments in the presence of and on human demands, were evaluated twice: two months after weaning, just before starting the training; and one month after it ended, when they were submitted to a final performance test. Previous to training, handling effects were not found in the foals’ behavioural responses when facing a motionless person. When approached, differences were shown: animals handled at birth or at weaning displayed less fearfulness, showed less locomotor activity and tolerated a closer approach, when compared to Controls.Moreover, the Wean-H foals were those that learned faster at training and the only group that passed all aims at the final test; the Imp-H foals were the less reactive, but did not learn better than Ex-H foals and were more troublesome when trained. In summary, our data suggest that 3-handling sessions in young horses are enough to act on human-animals’ relationship, learning performance and, and may be improved if performed in the specific period of weaning.

Influence of dietary nonstructural carbohydrate concentration on growth performance and carcass characteristics of Holstein steers.

ObjectiveSince very little information exists about the topic; in this experiment we compare, in a long-term finishing program, the growth-performance responses and carcass characteristics of Holstein steers where non-structural carbohydrate concentration of the diet is reduced from 64% to 51% (dry matter basis).MethodsSixty Holstein steer calves (129±2.2 kg) were blocked by initial weight into five groups and randomly assigned within weight groupings to 10 pens. Calves were fed with a steam-flaked corn-based finishing diets containing 51% higher fiber (HF) or 64% lower fiber (LF) nonstructural carbohydrates. Non-structural carbohydrates concentrations were manipulated substituting dried distiller grain with solubles and alfalfa hay for flaked corn. Cattle were weighed every 112 days and at the end of the experiment (day 308) when the cattle were harvested and carcass characteristics were evaluated.ResultsSteers fed the HF diet showed improvement (8.8%) in average daily gain (ADG) during the initial 112-d period. This effect was followed by a numerical trend for greater ADG throughout the remainder of the study so that overall ADG tended to be greater (4.9%, p = 0.06) for the HF than for LF. There were no treatment effects on dry matter intake. Gain efficiency and estimated dietary net energy (NE) were greater 8.3% and 5.2%, respectively for HF during the initial 112-d period. Overall (308-d) gain efficiency and estimated dietary NE were similar for both dietary treatments. However, due to differences in tabular dietary NE, the ratio of observed:expected dietary NE tended to be greater (4.1%, p = 0.06) for the HF vs LF diet. There were no treatment effects on carcass characteristics except for a tendency toward a slightly greater (0.5%, p = 0.09) estimated carcass yield.ConclusionReducing the non-structural carbohydrate concentration of a conventional steam-flaked corn-based growing finishing diet for Holstein steers can effectively enhance growth performance, particularly during the early growing and late finishing phases.

Preliminary Investigation of the Changes in Fecal Streptococcal Population due to Diet and Time of Day in Horses

A growing number of equine studies examine management factors that influence the microbial populations in regions of the gastrointestinal tract using culture-independent molecular techniques. We used quantitative polymerase chain reaction (qPCR) to evaluate changes in fecal streptococcal populations in horses fed different maturities of teff hay with fecal samples collected at 7 AM, 12 PM, and 7 PM. The objective of this study was to use qPCR and species-specific probes for 16S ribosomal DNA to quantify the percentage of equine hindgut streptococcal species (EHSS) relative to the total bacterial load in the feces. Feces from horses fed the most mature teff hay had the lowest %EHSS, and feces collected at 12:00 had the highest %EHSS (P < .05). Our interest in investigating %EHSS developed out of research that examined associations between changes in EHSS populations and the onset of laminitis. Although we expected almost no risk of laminitis in these forage fed horses, our hypothesis was that the different carbohydrate fractions in the three maturities of hay would result in differences in %EHSS in horses fed these hay maturities. The supply of carbohydrates, nonstructural or structural, influences the microbial species composition through the gastrointestinal tract. This study highlights the occurrence of measurable changes in %EHSS due to subtle changes in dietary nonstructural carbohydrate and also changes in samples taken at different times of day. This information is useful to others considering investigations of dietary influences on gastrointestinal microbial populations, particularly those that plan to use feces as their main sample medium.

Equine hyperinsulinemia: investigation of the enteroinsular axis during insulin dysregulation.

Compared with some other species, insulin dysregulation in equids is poorly understood. However, hyperinsulinemia causes laminitis, a significant and often lethal disease affecting the pedal bone/hoof wall attachment site. Until recently, hyperinsulinemia has been considered a counterregulatory response to insulin resistance (IR), but there is growing evidence to support a gastrointestinal etiology. Incretin hormones released from the proximal intestine, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide, augment insulin secretion in several species but require investigation in horses. This study investigated peripheral and gut-derived factors impacting insulin secretion by comparing the response to intravenous (iv) and oral d-glucose. Oral and iv tests were performed in 22 ponies previously shown to be insulin dysregulated, of which only 15 were classified as IR (iv test). In a more detailed study, nine different ponies received four treatments: d-glucose orally, d-glucose iv, oats, and commercial grain mix. Insulin, glucose, and incretin concentrations were measured before and after each treatment. All nine ponies showed similar iv responses, but five were markedly hyperresponsive to oral d-glucose and four were not. Insulin responsiveness to oral d-glucose was strongly associated with blood glucose concentrations and oral glucose bioavailability, presumably driven by glucose absorption/distribution, as there was no difference in glucose clearance rates. Insulin was also positively associated with the active amide of GLP-1 following d-glucose and grain. This study has confirmed a functional enteroinsular axis in ponies that likely contributes to insulin dysregulation that may predispose them to laminitis. Moreover, iv tests for IR are not reliable predictors of the oral response to dietary nonstructural carbohydrate.

Equine insulin receptor and insulin‐like growth factor‐1 receptor expression in digital lamellar tissue and insulin target tissues

Hyperinsulinaemia is implicated in the pathogenesis of endocrinopathic laminitis. Insulin can bind to different receptors: two insulin receptor isoforms (InsR-A and InsR-B), insulin-like growth factor-1 receptor (IGF-1R) and InsR/IGF-1R hybrid receptor (Hybrid). Currently, mRNA expression of these receptors in equine tissues and the influence of body type and dietary carbohydrate intake on expression of these receptors is not known. The study objectives were to characterise InsR-A, InsR-B, IGF-1R and Hybrid expression in lamellar tissue (LT) and insulin responsive tissues from horses and examine the effect of dietary nonstructural carbohydrate (NSC) on mRNA expression of these receptors in LT, skeletal muscle, liver and two adipose tissue (AT) depots of lean and obese ponies. In vivo experiment. Lamellar tissue samples were evaluated by quantitative reverse transcription polymerase chain reaction (RT-qPCR) for receptor mRNA expression (n=8) and immunoblotting for protein expression (n=3). Archived LT, skeletal muscle, liver and AT from lean and obese mixed-breed ponies fed either a low (~7% NSC as dry matter; 5 lean, 5 obese) or high NSC diet (~42% NSC as dry matter; 6 lean, 6 obese) for 7days were evaluated by RT-qPCR to determine the effect of body condition and diet on expression of the receptors in different tissues. Significance was set at P≤0.05. Lamellar tissue expresses both InsR isoforms, IGF-1R and Hybrid. LT IGF-1R gene expression was greater than either InsR isoform and InsR-A expression was greater than InsR-B (P≤0.05). Obesity significantly lowered IGF-1R, InsR-A and InsR-B mRNA expression in LT and InsR-A in tailhead AT. High NSC diet lowered expression of all three receptor types in liver; IGF-1R and InsR-A in LT and InsR-A in tailhead AT. Lamellar tissue expresses IGF-1R, InsR isoforms and Hybrids. The functional characteristics of these receptors and their role in endocrinopathic laminitis warrants further investigation.

Effects of dietary neutral detergent fibre to protein ratio on duodenal microbial nitrogen flow and nitrogen losses in lactating cows fed high-concentrate total mixed rations with different forage combinations

SUMMARYThe objective of the present study was to investigate the effect of dietary neutral detergent fibre (NDF) : crude protein (CP) ratio on duodenal microbial crude protein (MCP) flow and nitrogen (N) losses. The study was completed in a 5 × 5 Latin square design with five lactating Holstein dairy cows and 5 high-concentrate total mixed rations (TMR) with different forage combinations, typical for Northern China. The rations with a fixed forage-to-concentrate ratio (39 : 61) resulted in different dietary NDF : CP ratios: TMR1 3·03 : 1 (428·2 g NDF/kg : 141·4 g CP/kg); TMR2 2·74 : 1 (392·7 g NDF/kg : 143·2 g CP/kg); TMR3 2·55 : 1 (368·3 g NDF/kg : 144·4 g CP/kg); TMR4 1·84 : 1 (304·8 g NDF/kg : 165·8 g CP/kg); TMR5 1·60 : 1 (285·0 g NDF/kg : 178·0 g CP/kg). Rumen content, milk, blood, urine and faeces were sampled on the last 3 days of five 18-day periods. Purine derivatives in the urine samples were determined to estimate rumen MCP flow into the small intestine. Milk yield and milk protein yield increased linearly with decreasing dietary NDF : CP ratio although slight differences in dry matter intake were observed due to feed intake restriction. Diurnal ammonia N in the rumen and duodenal MCP flow increased linearly, but blood urea N, urinary N and faecal N linearly decreased with decreasing dietary NDF : CP ratio. The enhanced N utilization in the maize-silage-based TMRs (TMR4–5) in comparison with maize-stover-based TMRs (TMR1–3) increased milk yield and the synthesis of milk protein instead of milk fat in the lactating cows, probably due to high transfer of ammonia N into rumen MCP with a considerable increase of dietary non-fibre carbohydrate content and the decrease of NDF : CP ratio. The present results indicate that not only increasing dietary non-structural carbohydrate content but also adjusting the ratio of structural carbohydrate to CP ratio are important diet formulation strategies for mitigating N losses in lactating cows.

Comparative diet and nutrition of frugivorous and folivorous primates at the Singapore Zoo

Considerable variability in dietary and digestive strategies exists across primate taxa. Differences in wild primate diet are strongly reflected along the frugivory-folivory continuum, whereby the selection of fruits or leaves as primary diet is strongly linked to different digestive systems that optimizes the extraction of nutrients from these different food types to meet nutritional goals. Successful maintenance of wild primates in captivity require appropriate dietary husbandry to meet the different needs of these primate species. We examined the diet of six species of captive primates with primarily frugivorous or folivorous dietary management and how their nutritional intake corresponded to their provided diet of fruits/vegetables and leaves. Folivorous primates obtained major components of their diet (protein and carbohydrate) from their leave diet while frugivores obtained relatively equal proportions of these components from both food types. Folivorous primates obtained higher protein and fiber - Neutral Detergent Fiber (NDF) and Acid Detergent fiber (ADF) intake from their leave diets; and higher Non-Structural Carbohydrate (NSC) intake from their fruit diets. Frugivorous primates obtained higher NSC and lower fiber (ADF and NDF) intake from their fruit/vegetable diets. Higher fiber intake resulted in longer Transit Time (TT) for frugivores and longer Mean Retention Time (MRT) for folivores. Overall dietary NSC levels for folivores were close to the recommended upper limits for foregut fermenters; and dietary fiber levels were relatively high for frugivores. These results suggests that appropriate adjustments to the diet provided to these primates should be considered to reduce general intake of easily digestible carbohydrates by folivorous and evaluate the possible implications of high fiber diets for frugivores. Dietary husbandry for captive primates according to their dietary specializations should be considered whenever possible, within constrains of practical captive management.

Effect of dietary nonstructural carbohydrate content on activation of 5'-adenosine monophosphate-activated protein kinase in liver, skeletal muscle, and digital laminae of lean and obese ponies.

BackgroundIn EMS‐associated laminitis, laminar failure may occur in response to energy failure related to insulin resistance (IR) or to the effect of hyperinsulinemia on laminar tissue. 5′‐Adenosine‐monophosphate‐activated protein kinase (AMPK) is a marker of tissue energy deprivation, which may occur in IR.Hypothesis/ObjectivesTo characterize tissue AMPK regulation in ponies subjected to a dietary carbohydrate (CHO) challenge.AnimalsTwenty‐two mixed‐breed ponies.MethodsImmunohistochemistry and immunoblotting for total AMPK and phospho(P)‐AMPK and RT‐qPCR for AMPK‐responsive genes were performed on laminar, liver, and skeletal muscle samples collected after a 7‐day feeding protocol in which ponies stratified on body condition score (BCS; obese or lean) were fed either a low‐CHO diet (ESC + starch, approximately 7% DM; n = 5 obese, 5 lean) or a high‐CHO diet (ESC + starch, approximately 42% DM; n = 6 obese, 6 lean).Results5′‐Adenosine‐monophosphate‐activated protein kinase was immunolocalized to laminar keratinocytes, dermal constituents, and hepatocytes. A high‐CHO diet resulted in significantly decreased laminar [P‐AMPK] in lean ponies (P = .03), but no changes in skeletal muscle (lean, P = .33; obese, P = .43) or liver (lean, P = .84; obese, P = .13) [P‐AMPK]. An inverse correlation existed between [blood glucose] and laminar [P‐AMPK] in obese ponies on a high‐CHO diet.Conclusions and Clinical ImportanceLaminar tissue exhibited a normal response to a high‐CHO diet (decreased [P‐AMPK]), whereas this response was not observed in liver and skeletal muscle in both lean (skeletal muscle, P = .33; liver, P = .84) and obese (skeletal muscle, P = .43; liver, P = .13) ponies.

Effects of metformin hydrochloride on blood glucose and insulin responses to oral dextrose in horses

Metformin is a potential therapeutic agent for the treatment of insulin resistance (IR). In laboratory animals, orally administered metformin reduces intestinal glucose absorption and may therefore affect insulinaemic responses to oral carbohydrate ingestion. To determine whether pretreatment with metformin reduces plasma glucose concentration and insulin responses following consumption of dextrose in horses. Therapeutic cross-over study. Seven healthy Standardbred and Thoroughbred geldings were subjected to an oral dextrose challenge test on 4 occasions: with and without metformin, before and after induction of IR with dexamethasone. Metformin was administered by nasogastric tube at 30 mg/kg bwt 1 h before administration of dextrose. Glucose and insulin concentrations in plasma/serum were measured at regular intervals during each test. Linear mixed models were specified for each predetermined outcome variable, and for each model the 'treatment' was included as a fixed effect with 4 categorical levels (none, metformin, dexamethasone and dexamethasone with metformin) and horse accounted for as a random effect. In healthy horses, the administration of metformin resulted in a statistically significant reduction in peak glucose concentration (P = 0.002), area under the glucose curve (P<0.001) and insulin concentration 120 min after dextrose administration (P = 0.011). Following the induction of IR, administration of metformin was associated with significant differences in peak glucose concentration (P<0.001), the percentage increase in glucose concentration (P = 0.010), the area under the glucose curve (P<0.001) and insulin concentration at 120 min (P = 0.034) and 150 min after dextrose administration (P = 0.014). Metformin resulted in reduced glycaemic and insulinaemic responses both in healthy horses and in horses with experimentally induced IR. Metformin may benefit horses with naturally acquired IR by reducing glycaemic and insulinaemic responses to dietary nonstructural carbohydrates. Further investigations into the mechanisms of action of metformin in horses and controlled clinical trials are warranted.

Distribution of insulin receptor and insulin‐like growth factor‐1 receptor in the digital laminae of mixed‐breed ponies: An immunohistochemical study

Hyperinsulinaemia has been implicated in the pathogenesis of laminitis; however, laminar cell types responding to insulin remain poorly characterised. To identify laminar cell types expressing insulin receptor (IRc) and/or insulin-like growth factor-1 receptor (IGF-1R); and to evaluate the effect of dietary nonstructural carbohydrate (NSC) on their expression. Mixed-breed ponies (n = 22) received a conditioning hay chop diet (NSC ∼6%); following acclimation, ponies were stratified into lean (n = 11, body condition score [BCS]≤4) or obese (n = 11, BCS ≥7) groups and each group further stratified to remain on the low NSC diet (n = 5 each for obese and lean) or receive a high NSC diet (total diet ∼42% NSC; n = 6 each for obese and lean) for 7 days. Laminar samples were collected at the end of the feeding protocol and stained immunohistochemically for IRc and IGF-1R. The number of IRc(+) cells was quantified; distribution of IGF-1R was qualitatively described. Laminar IRc content was assessed via immunoblotting. The number of IRc(+) cells was greater in the laminae of high NSC ponies than low NSC ponies (P = 0.001); there was a positive correlation between the change in serum insulin concentration and number of IRc(+) cells (r(2) = 0.74; P<0.0001). No epithelial IRc(+) cells were observed; IRc(+) cells were absent from the deep dermis. Analysis of serial sections identified IRc(+) cells as endothelial cells. The distribution of IGF-1R was more extensive than that of IRc, with signal in vascular elements, epithelial cells and fibroblasts. Increased dietary NSC results in increased laminar endothelial IRc expression. Laminar keratinocytes do not express IRc, suggesting that insulin signalling in laminar epithelial cells must be mediated through other receptors (such as IGF-1R). Manipulation of signalling downstream of IRc and IGF-1R may aid in treatment and prevention of laminitis associated with hyperinsulinaemia.

An increase in dietary non-structural carbohydrates alters the structure and metabolism of the rumen epithelium in lambs

Steele, M. A., Greenwood, S. L., Croom, J. and McBride, B. W. 2012. An increase in dietary non-structural carbohydrates alters the structure and metabolism of the rumen epithelium in lambs. Can. J. Anim. Sci. 92: 123–130. This study investigated the effect of a grain challenge on the structure and metabolism of the rumen epithelium in lambs. In a randomized design, lambs (n = 8) received either a control diet [30% dry matter (DM) grain], or a diet of increasing amounts of grain to a maximum inclusion of 79% of DM for 12 d prior to slaughter. Rumen papillae were collected from the ventral sac on day 13 and prepared for histological and gene expression analyses. All lambs fed the high-grain diet were diagnosed with ruminal parakeratosis as the thickness of the corneum was higher (P&lt;0.01) compared with control lambs (51.0±2.3 vs. 17.3±2.5 µm). Plasma beta-hydroxybutyric acid concentrations increased linearly (P&lt;0.05) with increased grain consumption compared with the control. However, the relative mRNA expression of the ketogenic enzyme 3-hydroxy-3-methyl-glutaryl CoA-synthase (HMGCS2) in rumen papillae was not different between treatments. The expression of cholesterolgenic enzyme HMGCS1 was down-regulated by 0.70±0.06 (P&lt;0.05) fold in lambs fed the high-grain diet compared with the control. These results suggest that a short-term grain challenge in lambs is associated with altered rumen epithelium metabolism and structural changes indicative of ruminal parakeratosis.

Differential regulation of components of the apoptotic and ubiquitin-mediated proteolytic pathway in slow- and fast- twitch muscle type in lambs receiving increasing amounts of dietary non-structural carbohydrate

Non-fibre carbohydrate (NFC) rich diets are commonly fed in ruminant production systems. The objective was to determine whether NFC challenge affects proteasome activity, or messenger ribonucleic acid (mRNA) expression of proteasome subunits or apoptotic Bcl-2 proteins, in slow- or fast- twitch muscle of sheep. For 12 d prior to slaughter, lambs (n = 8) received either a control diet (28.4% of dry matter as grain), or a diet of increasing amounts of grain up to 79.1% of dry matter. A decrease in urinary pH (P = 0.01), base excess of blood and extracellular fluid (P = 0.01), bicarbonate (P = 0.03) and total carbon dioxide (P = 0.04), and an increase in anion gap (P = 0.07) in NFC lambs are indicative of metabolic acidosis. NFC lambs had significantly lower mRNA expression of the 20S -β subunit (P = 0.05), and a tendency toward lower mRNA expression of the 20S-α subunit (P = 0.11) and the 19S isoform (P = 0.15) in soleus, but not to the same extent in extensor digitorum longus (EDL) muscle. Downregulation of Bad mRNA expression occurred in both soleus (P = 0.10) and EDL (P = 0.08) muscle as a result of NFC challenge. These results indicate that NFC challenge does affect mRNA expression of genes related to the proteasome and apoptosis in a muscle specific manner. Key words: Ubiquitin-mediated proteolytic pathway, non-fibre carbohydrate, apoptosis, sheep

Short communication: Effects of dietary nonstructural carbohydrates pre- and postpartum on reproduction of grazing dairy cows

The working hypothesis was that postpartum anovulatory intervals (PPAI) of grazing dairy cows are shortened by inclusion of concentrates that increase the nonstructural carbohydrate content of the transition diet. Dietary treatments were arranged as a 2 × 2 factorial, with 68 multiparous cows assigned to isoenergetic diets (114 MJ of metabolizable energy/cow per day) of pasture and pasture silage (PreP) or pasture and pasture silage supplemented with 3kg of dry matter/cow per day a corn- and barley-based concentrate for 36 d prepartum (PreC). After calving, cows within each prepartum diet group were managed on isoenergetic diets (179 MJ of metabolizable energy/cow per day) of either pasture and pasture silage (PostP) or pasture and pasture silage supplemented with 5kg of dry matter/cow per day a corn- and barley-based concentrate (PostC) for at least 35 d and until reestablishment of ovulatory cycles. Relative to day of calving (d 0), blood samples were collected at least weekly from d −28 to 35 and milk samples were collected twice weekly for progesterone determination to diagnose ovulatory status. The main variable of interest was PPAI, defined as the interval between calving and the first detected increase in milk progesterone (>3ng/mL), followed by a pattern of progesterone concentrations consistent with onset of an ovulatory cycle. Subsequent mating records, pregnancy testing, and recalving data were also examined. Prepartum diet did not affect reproduction. The PPAI was 8 d shorter and the 6-wk pregnancy rate was 17% greater in PostC cows compared with PostP cows. Measured indicators of metabolic state and energy balance were poorly related to PPAI. The results support the existence of nutritional signals associated with nonstructural carbohydrates in the postpartum diet, independent of energy balance; these signals benefit the physiological mechanisms underlying the timing of first ovulation and possibly subsequent breeding performance.

Effects of dietary nonstructural carbohydrates and protein sources on feeding behavior of tethered heifers fed high-concentrate diets1

To describe the feeding behavior of growing heifers fed high-concentrate diets with different sources of protein and nonstructural carbohydrates, and to explain the ruminal fermentation pattern, 4 ruminally fistulated Holstein heifers (BW = 132.3 +/- 1.61 kg) were assigned to a 4 x 4 Latin square design with a 2 x 2 factorial arrangement of treatments. Two non-structural carbohydrate sources (barley and corn) and 2 protein sources [soybean meal (SBM) and sunflower meal (SFM)] that differ in their rate and extent of ruminal degradation were combined, resulting in a synchronized, rapid fermentation diet (barley-SFM), a synchronized, slow fermentation diet (corn-SBM), and 2 unsynchronized diets consisting of a rapidly and a slowly fermenting component (barley-SBM and corn-SFM). The corn-SFM diet resulted in a lower frequency of feeding (P < or = 0.05), longer meal length (P < or = 0.043), and larger meal size (P < or = 0.037) than the other 3 diets. Dietary treatment had no effect (P > or = 0.09) on the daily percentages of posture and behaviors. In general, heifers spent 9.97 +/- 0.83% of the day eating, 2.11 +/- 0.42% drinking, 25.13 +/- 1.36% ruminating, 16.97 +/- 1.42% in other activities such as social behavior and self-grooming, and the rest of the day (45.82 +/- 2.55%) resting or doing no chewing activities. Eating, drinking, and social behaviors were performed while standing (P < or = 0.01), whereas resting and ruminating occurred mainly while lying (P = 0.001). Eating took place mainly in the first 4 h after feeding (P = 0.001), whereas ruminating occurred mainly at night (P = 0.001). When chewing activities (eating and ruminating) were expressed per kilogram of DM or NDF from roughage intake, more time (P = 0.004) was spent chewing per kilogram of DMI for barley-based diets, and per kilogram of NDF from roughage intake for barley- (P = 0.01) and SFM- (P = 0.002) based diets. Tethered heifers fed the more fermentable and rapidly synchronized diet (barley-SFM) reduced intake and increased chewing time. With these high-concentrate diets, time spent chewing was inversely related to roughage intake.

Effects of urea, isolated soybean protein and blood meal on growing steers fed a corn-based diet

A short term feeding trial was conducted to assess effects of nitrogen (N) supplementation on growing cattle and the ability of the Cornell Net Carbohydrate and Protein System (CNCPS) to predict responses. Four corn-based diets were used: (1) a 30% ruminal N-deficient control diet; (2) a urea supplemented diet; (3) a urea+isolated soy protein (ISP) diet; and (4) a urea+ISP+blood meal (BM) diet. Four Holstein steers (average initial body weight of 251 kg) were randomly assigned in a 4×4 Latin Square treatment design. Steers were fed 95% of ad libitum intake on an hourly basis, and 500 μg of oestradiol-17β were administered twice daily. Average daily gain (ADG) increased ( P<0.05) when urea was added to the diet, but including urea+ISP was not better than the control or urea alone ( P>0.05). The urea+ISP+BM diet was better than the control or urea+ISP diets ( P<0.05), but it was not better than urea alone ( P>0.05). Addition of ISP or ISP+BM to the urea diet did not increase whole tract true digestibility of neutral detergent fibre, acid detergent fibre, or apparent digestibility of the dietary non-structural carbohydrate fraction ( P>0.05). The addition of urea, ISP or ISP+BM to the control diet caused an increase in N intake ( P<0.05), but faecal N did not increase ( P>0.05). Urinary N excretion increased 2.8-fold compared to the control diet when urea, ISP or ISP+BM were added ( P<0.05), but there was no difference between these latter three treatments ( P>0.05). Urea, ISP and ISP+BM increased N retention ( P<0.05), and ISP+BM was higher than urea and ISP ( P<0.05). The numerical difference in N retention between urea and urea+ISP was not significant ( P>0.05). When urea, ISP or ISP+BM were added, plasma urea N increased ( P<0.05), but these three treatments had no effect on glucose, non-esterified fatty acids or insulin ( P>0.05). Results show that a ruminal N-deficiency can have a negative impact on ADG, and this effect was consistent with predictions made by the CNCPS. Substitution of urea by ISP did not cause an increase in ADG, indicating that ISP may not be as ruminally degradable as urea. Blood meal increased ADG, consistent with CNCPS predictions. Because ISP could have been a source of ruminally undegradable protein rather than ruminal peptides and amino acids, the peptide stimulation predictions of the CNCPS could not be evaluated.

Ruminal peptide concentration required to optimize microbial growth and efficiency.

Experimentation, with a single-phase continuous culture system operated at fractional dilution rates of 0.03 and 0.09 per hour and four cannulated crossbred steers (260 +/- 20 kg) used in a 4 x 4 Latin square design, was conducted to determine the level of ruminally degradable protein (RDP) that maximized microbial efficiency (MOEFF), microbial nitrogen flow, and nutrient digestibility in the rumen. Treatments consisted of increasing diet RDP levels (from 3.5 to 17.5% RDP on a DM basis). The basal diet was corn with casein or soybean meal used as the source of RDP in the continuous culture experiment and animal study, respectively. Dietary nonstructural carbohydrate (NSC) ranged from 52 to 75% on a dry matter basis. Urea was added to ensure an adequate ammonia nitrogen source for microbial growth. The RDP levels did not affect true digestibility of dry matter and organic matter, ruminal pH, particulate passage rate, or liquid passage rate in the animal study. As RDP increased, bacterial nitrogen production increased linearly (P < 0.05) only for the 0.09/h dilution rate. Microbial efficiency was not influenced by RDP level. Ruminal peptide and NH3 N concentration increased linearly (P < 0.05) as RDP increased. Based on this experimentation, 1.8 mM peptide maximized MOEFF when ammonia nitrogen was not limiting (> 2 mg/dL). We concluded from this research that the RDP requirement of NSC-fermenting bacteria was lower than that currently fed in many diets.

Effects of Starch Source and Level of Forage Neutral Detergent Fiber on Performance by Dairy Cows

The effectiveness of neutral detergent fiber (NDF) from soyhulls and whole cottonseed for replacing NDF from forage was evaluated in a lactation trial during wk 10 to 25 of lactation. Forty-eight cows were blocked and randomly assigned within a block to one of four diets: 1) 21% forage NDF with corn 2) 16% forage NDF with corn, 3) 16% forage NDF with corn and wheat (1:1) and, 4) 11% forage NDF with cottonseed and corn. Soybean hulls were added at approximately 23.0% of dry matter (DM) for the 16 and 11% forage NDF diets to replace forage and formulate diets with 35% nonfiber carbohydrates. Actual forage NDF concentration were 17.8, 14.0, 13.9, and 9.4%, respectively. Dry matter intake and milk yield were highest for cows fed 11% forage NDF with cottonseed. Milk fat percentage was higher for cows consuming 21% forage NDF and 16% forage NDF with corn than for cows fed the two other diets. Cows fed 16% forage NDF with corn and wheat experienced milk fat-protein inversion, but ruminal acetate: propionate was lower for cows fed 11% forage NDF than cows fed 16% forage NDF. Body weight (BW) and BW change were not different among treatments. Time spent chewing was similar among all diets. For cows in midlactation, forage NDF may be reduced to 9 to 11% when cottonseed is at 11% of DM and dietary non-structural carbohydrates are at 30% of DM. Forage NDF may be reduced to 14 to 16% without cottonseed when nonstructural carbohydrates are at 30% of DM.

The effects of nonstructural carbohydrate and dietary protein on feed intake, ruminal fermentation and cows performance

Providing high levels of nonstructural carbohydrate (NSC) in ruminant diets tends to change fermentation lowering rumen pH and reduce milk fat content. Balancing readily available N and energy-yielding carbohydrate may enhance microbial growth rate, alter fermentation and fibre digestion in the rumen, which subsequently may have an impact on nutrient supply to host animal. Therefore, the objective of this study was to measure the effects of dietary nonstructural carbohydrate and protein level on intake, ruminal fermentation and performance of dairy cows using cassava as main energy source.Forty-two crossbred cows (60.9% Holstein Friesian, 26.8% Danish Red, 10.2% Red Sindi) at a mean of 71.0 ± 28.5 days in milk (DIM) with a pre-treatment milk yield of 13.2 ± 2.2 kg/d and a BW 373.1 ± 33.4 kg. Cows were tethered in stalls and randomly allocated to receive one of six total mixed ration (TMR) on ad-lib basis. Isocaloric diets (ME 11.2 MJ/kg) were formulated to contain Ruzi grass silage and a concentrate mix (20:80 ratio) containing NSC (30, 35, 40%) in combination with 2 levels of crude protein (15.7, 18.4%).

Effects of Varying Forage and Concentrate Carbohydrates on Nutrient Digestibilities and Milk Production by Dairy Cows1,2

Five Holstein cows with ruminal cannulas were used in a 5 × 5 Latin square design to determine the effect of replacing forage NDF with soyhull NDF and varying concentrations of nonstructural carbohydrates on nutrient digestion and milk production. Diets in which NDF percentage from forage (corn silage: alfalfa hay, 1:1) was 80 (control), 70, or 60 were formulated by substituting soyhulls for forage; total forage was 43.2, 36.7, and 31.1% of the diets, respectively, but total NDF was 31%. Nonstructural carbohydrates were formulated to be 47 (control), 35, or 25% by substituting soyhulls, roasted soybeans, and Ca soaps for concentrate. Ruminal acetate: propionate ratio decreased linearly when diets lower in forage NDF were fed, but it increased quadratically when dietary nonstructural carbohydrates were reduced. Apparent digestibility of OM increased quadratically, but NDF digestibility and lactation performance were unaffected when diets lower in forage NDF were fed. Digestibility of NDF increased linearly when nonstructural carbohydrates were reduced, perhaps because of greater digestibility of soyhull NDF and smaller negative associative effects. Fat from soybeans and Ca soaps was increased as nonstructural carbohydrates decreased. Added fat probably increased fatty acid digestibility and decreased milk protein percentage. Greater FCM production without correspondingly greater feed intake or BW loss increased feed efficiency as nonstructural carbohydrates decreased. In dairy rations containing soyhulls, 60% of dietary NDF from forage should maintain lactation performance, and decreasing nonstructural carbohydrates to 25 to 35% of feed DM, coupled with adding dietary fat, may decrease negative associative effects and improve efficiency of milk production.