D. A. Christensen

Heat-induced protein structure and subfractions in relation to protein degradation kinetics and intestinal availability in dairy cattle

The objectives of this study were to reveal protein structures of feed tissues affected by heat processing at a cellular level, using the synchrotron-based Fourier transform infrared microspectroscopy as a novel approach, and quantify protein structure in relation to protein digestive kinetics and nutritive value in the rumen and intestine in dairy cattle. The parameters assessed included 1) protein structure alpha-helix to beta-sheet ratio; 2) protein subfractions profiles; 3) protein degradation kinetics and effective degradability; 4) predicted nutrient supply using the intestinally absorbed protein supply (DVE)/degraded protein balance (OEB) system for dairy cattle. In this study, Vimy flaxseed protein was used as a model feed protein and was autoclave-heated at 120 degrees C for 20, 40, and 60 min in treatments T1, T2, and T3, respectively. The results showed that using the synchrotron-based Fourier transform infrared microspectroscopy revealed and identified the heat-induced protein structure changes. Heating at 120 degrees C for 40 and 60 min increased the protein structure alpha-helix to beta-sheet ratio. There were linear effects of heating time on the ratio. The heating also changed chemical profiles, which showed soluble CP decreased upon heating with concomitant increases in nonprotein nitrogen, neutral, and acid detergent insoluble nitrogen. The protein subfractions with the greatest changes were PB1, which showed a dramatic reduction, and PB2, which showed a dramatic increase, demonstrating a decrease in overall protein degradability. In situ results showed a reduction in rumen-degradable protein and in rumen-degradable dry matter without differences between the treatments. Intestinal digestibility, determined using a 3-step in vitro procedure, showed no changes to rumen undegradable protein. Modeling results showed that heating increased total intestinally absorbable protein (feed DVE value) and decreased degraded protein balance (feed OEB value), but there were no differences between the treatments. There was a linear effect of heating time on the DVE and a cubic effect on the OEB value. Our results showed that heating changed chemical profiles, protein structure alpha-helix to beta-sheet ratio, and protein subfractions; decreased rumen-degradable protein and rumen-degradable dry matter; and increased potential nutrient supply to dairy cattle. The protein structure alpha-helix to beta-sheet ratio had a significant positive correlation with total intestinally absorbed protein supply and negative correlation with degraded protein balance.

Influence of dry heat treatment of canola meal on site and extent of nutrient disappearance in ruminants

A study was conducted to determine the effects of temperature and duration of heating (125 or 145 °C for 10, 20 or 30 min) on ruminal, intestinal and total tract disappearance of the dry matter (DM) and crude protein (CP) fractions of canola meal. Two steers fitted with rumen and duodenal cannulas were utilized. The effects of heating on ruminal disappearance of DM and CP were determined by incubating samples in the rumen for 2, 4, 6, 8, 12, and 24 h. Partitioning DM and CP disappearance between the rumen, intestines (small and large) and total tract was accomplished using the mobile nylon bag technique. Relative to the unheated control meal, heating at 125 or 145 °C reduced (P < 0.05) ruminal DM and CP disappearance. Relative to the control, no effects of heating to 125 °C were observed on intestinal DM or CP disappearance with the exception that samples heated for 20 or 30 min and incubated in the rumen for 24 h had higher (P < 0.05) intestinal DM disappearance values. Heating to 145 °C reduced (P < 0.05) intestinal DM disappearance relative to the control, particularly for samples heated for 30 min. Heating to 145 °C reduced (P < 0.05) intestinal CP disappearance across all rumen incubation times. No differences between the control and meals heated to 125 °C were found in total tract DM and CP disappearance, indicating no negative effects of heating to 125 °C on nutrient digestion. Heating to 145 °C reduced (P < 0.05) both total tract DM and CP disappearance. Acid detergent insoluble nitrogen content of the treated meal was negatively related to intestinal (r2 = 0.78) and total tract (r2 = 0.82) CP disappearance. It is concluded that heating CM to a temperature of 145 °C will reduce ruminal and total tract availability of the DM and CP fractions. Heating to 125 °C for 10, 20 or 30 min will reduce rumen disappearance of both DM and CP but will not significantly reduce the disappearance of CP over the total tract of the ruminant. These results indicate that short duration heating of canola meal to 125 °C, is an effective method of increasing rumen undegradable protein content without impairing intestinal digestibility.

Effect of variety and maturity stage on chemical composition, carbohydrate and protein subfractions, in vitro rumen degradability and energy values of timothy and alfalfa

The objective of this study was to investigate the effects of forage variety and stage of maturity on chemical composition, protein and carbohydrate subfractions, in vitro rumen degradability and energy content under the climatic conditions of western Canada. Two varieties of alfalfa (Medicago sativa L. cvs. Pioneer and Beaver) and timothy (Phleum pratense L. cvs. Climax and Joliette), grown at three locations in Saskatchewan (Canada), were cut at three stages [1 = 1 wk before commercial cut (early bud for alfalfa; joint for timothy); 2 = at commercial cut (late bud for alfalfa; pre-bloom head for timothy); and 3 = one week after commercial cut (early bloom for alfalfa; full head for timothy)]. The results showed that: (1) the varieties had minimal effects on nutritional value; however, (2) stage of cutting had a large impact on chemical composition, protein and carbohydrate fractions, in vitro rumen degradability and energy value. As plant maturity advanced from stage 1 to 3, the following changes were n...

Ultrastructural-chemical makeup of yellow-seeded (Brassica rapa) and brown-seeded (Brassica napus) canola within cellular dimensions, explored with synchrotron reflection FTIR microspectroscopy

Synchrotron-based FTIR micro spectroscopy, developed recently as a novel, rapid and non-destructive analytical technique, could reveal chemical information of the intrinsic microstructures of biological tissues at ultra-spatial resolution. The objective of this study was to use synchrotron reflection FTIR microspectroscopy to explore chemical makeup (functional group and bonding characteristics) of ultrastructural tissues within cellular dimensions (10 µm × 10 µm) of yellow-seeded (Brassica rapa ‘Klondike’) and brown-seeded (Brassica napus ‘Bounty’) canola. The results showed that the ratios of total CH2:CH3, CH3-asymmetric:CH3-symmetric, CH2-asymmetric:CH2-symmetric and total CH-asymmetric:CH-symmetric were 1.06 and 1.13, 1.28 and 1.26, 2.90 and 3.08, 1.82 and 1.78, for the yellow-seeded and brown-seeded canola, respectively. There were no differences between the two canola types in the content and ratios of CH groups (CH2 and CH3) of the scanned areas, indicating that lipid chain length and branching ar...

Use of synchrotron FTIR microspectroscopy to identify chemical differences in barley endosperm tissue in relation to rumen degradation characteristics

Valier (feed-type) and Harrington (malting-type) barley differ in rumen degradation characteristics. Harrington, in contrasts to Valier, exhibits a high rate and extent of rumen degradation, which can lead to metabolic problems such as acidosis and bloat in ruminants. Traditional “wet” chemical analysis cannot detect biological differences between barley varieties due to destruction of endosperm structure during processing. Synchrotron Fourier transform infrared microspectroscopy (SR-FTIR) is capable of exploring the chemical makeup of intact plant tissue with high signal to noise ratio at spatial resolutions as fine as 3~10 µm. The objective of this study was to use SR-FTIR microspectroscopy to explore and identify chemical differences in the ultra-structural matrix of the endosperm tissue of the two barley varieties as related to differences in rumen degradation characteristics. The results showed that the infrared absorbance intensity (Log 1/R) of the starch and protein varied considerably between the ...

Effects of micronization of flaxseed on nutrient disappearance in the gastrointestinal tract of steers

Abstract Two steers fitted with ruminal and duodenal cannulas were used in a randomized complete block design to determine the effects of micronization on ruminal and postruminal and total tract digestibility of protein and amino acids of flaxseed. Micronized flaxseed had lower (P

Effects of stage of processing of canola seed on chemical composition and in vitro protein degradability of canola meal and intermediate products

A study was conducted to determine the effects of stage of processing of canola seed on chemical characteristics and in vitro crude protein degradability (IVCPD) of canola products. Processing stage prior to oil extraction had no effect on nutrient composition or IVCPD of canola products. Prepressing of cooked flaked seed reduced IVCPD and increased fiber and crude protein (CP) levels of presscake relative to canola seed (P < 0.05). Heating in the desolvetizer-toaster increased neutral detergent fiber (NDF) content and reduced CP solubility and IVCPD of canola meal relative to solvent-extracted meal (P < 0.05). Acid detergent insoluble CP of canola products was not affected by stage of processing. It was concluded that major changes in protein composition and degradability took place as a result of heating in the desolventizer-toaster stage. Key words: Canola processing, heat treatment, protein degradability

The nutritive value of hemp meal for ruminants

Hemp meal (HM) is derived from the processing of hemp (Cannabis Sativa L.) seeds. The objective of this study was to determine the nutritive value of HM for ruminants. Two ruminally fistulated cows were used in a randomized complete-block design to estimate in situ ruminal dry matter (DM) and crude protein (CP) degradability of HM relative to canola meal (CM), heated canola meal (HCM) and borage meal (BM) meal. Intestinal availability of rumen undegraded CP was estimated using a pepsin–pancreatin in vitro assay. Twenty growing lambs were utilized in a completely randomized design to determine total–tract nutrient digestibility coefficients of diets in which HM replaced CM at 0, 25, 50, 75 and 100% as a protein source. Results of the in situ study showed that the soluble-CP fraction of HM was similar to that of HCM and lower (P < 0.05) than those of CM and BM. Rate of degradation of the potentially degradable CP fraction and effective CP degradability of HM was higher (P < 0.05) than HCM and lower (P < 0.0...

Role of thiamine status in sulphur induced polioencephalomalacia in sheep

The effects of excess dietary sulphur were studied in sheep supplemented and unsupplemented with thiamine. The diets contained either 0.19 per cent sulphur (LS) or 0.63 per cent sulphur (HS) in combinations with 14 mg kg-1 thiamine (LB1) or 243 mg kg-1 thiamine (HB1). A total of 56 two-month-old lambs were used. Groups consisting of nine, nine, 22 and 16 lambs were fed LS-LB1, LS-HB1, HS-LB1 and HS-HB1 diets, respectively for 14 weeks. Out of 22 lambs fed the HS-LB1 diet, seven lambs developed neurological signs between the third and eighth week of the trial. Two of these lambs died, three that were in extremis were euthanased, and two recovered completely. All clinically affected animals had extensive malacic lesions in the cerebral cortex, midbrain and brainstem. None of the lambs from the LS groups or HS-HB1 group developed clinical signs. Several clinically normal lambs from the HS-LB1 group had necrotic lesions in their brains at gross and microscopic examination. Supplementation with dietary thiamine prevented development of clinical signs, but did not totally prevent development of microscopic brain lesions. Brain thiamine concentration, transketolase activity and thiamine pyrophosphate (TPP) effect were not different (P greater than 0.05) among groups. There was a strong effect (P less than 0.0001) of dietary thiamine supplementation on blood thiamine concentration and TPP effect. Blood thiamine concentration was higher whereas TPP effect was lower in the thiamine supplemented sheep. Blood and tissue thiamine concentrations in sheep exposed to high dietary sulphur did not indicate either systemic or local thiamine deficiency per se. Increased TPP effect in sheep fed the HS-LB1 diet indicated mild to moderate metabolic thiamine deficiency. Thiamine inadequacy may be an effect of an increased requirement for thiamine in animals exposed to excess dietary sulphur.

IN SITU RUMEN DEGRADATION KINETICS OF TIMOTHY AND ALFALFA AS AFFECTED BY CULTIVAR AND STAGE OF MATURITY

The objective of this study was to investigate the effects of cultivar and stage of maturity at cutting on rumen degradation characteristics of some feed components in alfalfa (Medicago sativa L.) and timothy (Phleum pratense L.). Two adapted cultivars of alfalfa (Pioneer and Beaver) and timothy (Climax and Joliette), grown in Saskatchewan (Canada), were cut at three stages: 1 = 1 wk before commercial cut (early bud for alfalfa; joint for timothy); 2 = at commercial cut (late bud for alfalfa; pre-bloom head for timothy); 3 = 1 wk after commercial cut (early bloom for alfalfa; full head for timothy). Rumen degradation characteristics, including rapidly degradable fraction (A), potentially degradable fraction (B), undegradable fraction (C), degradation rate (Kd), lag time (T0), and effective degradability (ED) of each component, were determined using in situ technique and analyzed by first order kinetic equation described by Orskov and McDonald with lag time. The results showed that, in alfalfa, the cultiva...