Three experiments were conducted to test the hypothesis that vasoactive intestinal polypeptide (VIP) infused into the gastric artery and exposure to a low temperature will increase feed intake, duodenal flow and amino acid supply to the small intestine of sheep, both effects as a result of increased ruminal outflow. A total of eight sheep (55 ± 2.7 kg) with rumen and duodenal cannulae and eight sheep without digestive cannulae were provided with continuous access to a diet of alfalfa pellets. Water and salt licks were accessible 24 h d -1 . Two infusion treatments, VIP (1 nmol min -1 ) solution or a saline control (0.9% NaCl solution) were given through a left gastric-artery catheter for 10 min each hour for the first 3 h after feeding each day for 3 to 4 consecutive days in a crossover arrangement during experimental periods. Sheep were exposed to 1 ± 2°C in exp.1, to a thermoneutral (21 ± 2°C) environment in exp. 3 and to both thermoneutral (21 ± 1.5°C) and cold environments (1 ± 2°C) in exp. 2. These studies demonstrated that a VIP infusion of short duration did not increase dry matter intake (DMI) (P > 0.05) and did not influence duodenal passage of DM, OM, CP, amino acids (AA) or bacterial protein (P > 0.05). The exposure of animals to a cold environment stimulated (P < 0.05) intake of DM, OM and AA and duodenal passage of DM, OM, AA and microbial protein. There was an interaction (P < 0.05) between VIP and environmental temperature such that VIP improved duodenal AA passage in the thermoneutral, but not in the cold, environment. The data suggest that short-term VIP treatment does not induce a change in feed intake when sheep have access to feed for 24 h d -1 . Cold environmental temperature stimulates significant increases in feed intake and passage of protein and AA into the small intestine of sheep fed ad libitum, such that there was enrichment of intestinal supply of AA relative to digestible organic matter. Key words: Sheep, vasoactive intestinal peptide, feed intake, environmental temperature
Differences in in situ dry matter degradabilities occurred at all incubation times when 22 cultivars of barley gram grown at three locations were examined. Rapidly and slowly degradable fractions ranged from 25 to 40% and from 49 to 65%, respectively. Rates of degradation ranged from 23 to 35% h −1 (P = 0.03). Key words: Barley, cultivars, in situ, degradability, location
We tested the hypothesis that dietary components reaching the bovine small intestine influence the expression of genes that encode the gastrointestinal neuropeptides cholecystokinin (CCK) and glucagon-like peptide-1 (GLP-1). The amount of digesta reaching the intestine was manipulated during the experiment by withholding feed from five heifers fitted with ruminal, duodenal, and ileal cannulas for 48 h and then subsequent refeeding. Duodenal and ileal biopsies were collected using a fiber-optic endoscope. A Northern hybridization procedure was used to evaluate changes in gene expression. Blood concentrations of CCK and GLP-1 were determined with RIA. The data indicate that CCK blood concentration and mRNA abundance decreased during the period of feed deprivation, but they returned to predeprivation values within 16 to 24 h of refeeding. The GLP-1 blood concentration also decreased during feed deprivation and returned to predeprivation values within 4 to 8 h of refeeding, despite the fact that proglucagon mRNA abundance did not change significantly during feed deprivation and refeeding. These findings provide evidence that CCK and GLP-1 are released in response to nutrients that reach the small intestine and may be involved in the physiological process of digestion and possibly play a role in regulating feed intake in ruminants.
Effects of increasing the proportions of dietary barley grain or corn on viscosity of duodenal digesta supernatant and concentrations of cholecystokinin (CCK), glucose and amino acids in portal plasma and concentrations of CCK, insulin and glucose in jugular plasma were determined. Four steers (374 ± 6.4 kg) were surgically fitted with ruminal and duodenal cannulae and indwelling portal vein catheters. The steers were fed diets containing 20, 40, 60, and 80% rolled barley or cracked corn (DM basis) replacing respective silages, in two experiments with 4 × 4 Latin square design. After adjusting the steers to the diets for 14 d, digesta samples from the duodenum and blood samples from the portal and jugular veins were collected twice daily for 5 d. Increasing the proportion of dietary barley or corn increased the viscosity [measured as centipoise (cP)] of duodenal supernatant (from 1.3 to 2.0 and from 1.5 to 2.8 cP, P < 0.05), respectively. Portal plasma CCK concentration increased linearly (2.4 to 4.9 pmol, P < 0.05) as the proportion of dietary barley increased. However, in corn-fed steers, the highest portal CCK concentrations were observed in steers receiving 20% corn and these concentrations were not affected by corn content of the diet. Increasing dietary barley resulted in a linear increase in jugular plasma CCK concentration of steers, but a linear (P < 0.05) decline was noted when corn was fed to steers in increasing proportions. Portal and jugular plasma glucose concentrations were not altered in barley-fed steers, but both portal and jugular glucose increased (P < 0.05) with increasing dietary corn. Jugular insulin concentration was higher in steers fed 80% barley or corn than in those receiving the diets with less grain. Total amino acid concentrations in portal plasma were higher by 30% in steers fed corn than in those fed barley, but were not affected by relative proportion of dietary corn. These data suggest that feeding cattle increasing proportions of barley or corn grain increases duodenal viscosity, which, together with components of digesta, may be involved in affecting the secretion of hormones, such as CCK, and the concentrations of absorbed nutrients in portal plasma, which can be expected to influence animal performance. Key words: Steers, dietary barley, corn, portal and jugular hormones, glucose, amino acids
Beef composite types have combined favourable traits of pure breeds. The energy requirement for Muscle (EM) and Fat (EF) deposition, the ratio of EF:EM and proportions of energy required to produce M and F were different (P < 0.01) for Beef composite types (CT) and harvest ages (HA). EF was dependent on both CT and HA due to interaction (P=0.03). The proportion of energy required to produce Fat (Prop F) increased from 60.2% at 274 d to 76.8% at 456 d (P<0.01) and the proportion of energy required to produce Muscle (Prop M) decreased from 39.8% at 274 d to 23.2% at 456d (P<0.01). Based on EF:EM ratio (3.0 or 75 % as a reference value) and energetic efficiency of producing M and F, M1, M2 and M3 can be harvested at 399d, M4 at 456d and TX can be harvested at or after 456 d to avoid the production of excessively fat carcasses.
Hunerberg, M., McGinn, S. M., Beauchemin, K. A., Okine, E. K., Harstad, O. M. and McAllister, T. A. 2013. Effect of dried distillers’ grains with solubles on enteric methane emissions and nitrogen excretion from finishing beef cattle. Can. J. Anim. Sci. 93: 373–385. The objective of this study was to examine the impact of corn- or wheat-based dried distillers’ grains with solubles (CDDGS, WDDGS) on enteric methane (CH₄) emissions from finishing beef cattle, and to determine if any observed reductions were a result of the fat content of CDDGS. A second objective was to compare the effect of CDDGS or WDDGS on N excretion. The experiment was designed as replicated 4×4 Latin square with 28-d periods using 16 ruminally fistulated crossbred heifers. The control diet contained 87% barley grain, 8% barley silage and 5% supplement (dry matter; DM basis). Treatment diets were formulated by replacing 40% DM of barley grain with CDDGS, WDDGS, or corn oil supplemented WDDGS (WDDGS+oil). For the WDDGS+oil diet 6.5% corn oil was added to WDDGS (3.4% fat DM) to achieve a similar fat level as in CDDGS (9.7% DM). All diets were fed as total mixed rations once daily ad libitum. Total collection of urine and faeces was conducted between days 18 and 21. Methane was measured between days 25 and 28 using four identical open circuit respiratory chambers. Compared with WDDGS, feeding CDDGS and WDDGS+oil reduced (P<0.05) CH₄ emissions as a percentage of gross energy intake (GEI) from 5.5 to 4.0 and 4.2%, respectively. Feeding CDDGS also reduced (P<0.05) CH₄ emissions compared with the control (5.0% of GEI), while WDDGS+oil tended (P=0.08) to elicit a similar response. Methane (% of GEI) between WDDGS and the control did not differ (P=0.29). Excretion of total N was greater (P<0.001) for CDDGS, WDDGS and WDDGS+oil (220, 253, and 265 g d⁻¹) compared with the control (143 g d⁻¹). Although oil appears to be responsible for reducing CH₄ emissions when DDGS is included in the diet, increased N excretion requires that a complete life cycle assessment be conducted to assess the full impact of DDGS on greenhouse gas emissions from finishing cattle.
The effects of intragastric arterial infusions (1 mL min −1 ) of physiological saline, vasoactive intestinal polypeptide (VIP) or VIP-antagonist [4Cl-D-Phe 6 , Leu 17 ] VIP (1 nmol mL −1 ) on electromyographic (EMG) activities of the reticulum and reticulo-omasal orifice (ROO) in conscious, solid, meal-fed ewes kept in either warm (18 °C) or cold (1 °C) environments were studied. Infusions were of 15 min duration before, during and after feeding in both environments. In each ruminoreticular cycle the ROO showed long bursts of EMG activity coincidental with reticular EMG activity. Quiescence of the ROO was never fully observed until the reticulum relaxed. The frequencies of reticular bursts in both environments were higher during the period of active eating than during the post- and prefeeding periods. Infusion of VIP in the warm but not in the cold environment reduced frequency of reticular EMG. Compared with saline and antagonist, VIP increased the mean duration of the ROO quiescence to 13 s in the cold environment and to a significantly lower mean of 9 s in the warm environment. We conclude that 1) VIP mediates relaxation of the ROO in solid, meal-fed sheep, 2) ROO EMG activity is influenced by different environments and by phases of the feeding cycle, and 3) the inactivity of the ROO (relaxation) is not coincidental with the reticular EMG bursts in solid-meal-fed sheep. Key words: Sheep, VIP, reticulo-omasal orifice, EMG activity, warm and cold environments
Hünerberg, M., McGinn, S. M., Beauchemin, K. A., Okine, E. K., Harstad, O. M. and McAllister, T. A. 2013. Effect of dried distillers’ grains with solubles on enteric methane emissions and nitrogen excretion from finishing beef cattle. Can. J. Anim. Sci. 93: 373–385. The objective of this study was to examine the impact of corn- or wheat-based dried distillers’ grains with solubles (CDDGS, WDDGS) on enteric methane (CH 4 ) emissions from finishing beef cattle, and to determine if any observed reductions were a result of the fat content of CDDGS. A second objective was to compare the effect of CDDGS or WDDGS on N excretion. The experiment was designed as replicated 4×4 Latin square with 28-d periods using 16 ruminally fistulated crossbred heifers. The control diet contained 87% barley grain, 8% barley silage and 5% supplement (dry matter; DM basis). Treatment diets were formulated by replacing 40% DM of barley grain with CDDGS, WDDGS, or corn oil supplemented WDDGS (WDDGS+oil). For the WDDGS+oil diet 6.5% corn oil was added to WDDGS (3.4% fat DM) to achieve a similar fat level as in CDDGS (9.7% DM). All diets were fed as total mixed rations once daily ad libitum. Total collection of urine and faeces was conducted between days 18 and 21. Methane was measured between days 25 and 28 using four identical open circuit respiratory chambers. Compared with WDDGS, feeding CDDGS and WDDGS+oil reduced (P<0.05) CH 4 emissions as a percentage of gross energy intake (GEI) from 5.5 to 4.0 and 4.2%, respectively. Feeding CDDGS also reduced (P<0.05) CH 4 emissions compared with the control (5.0% of GEI), while WDDGS+oil tended (P=0.08) to elicit a similar response. Methane (% of GEI) between WDDGS and the control did not differ (P=0.29). Excretion of total N was greater (P<0.001) for CDDGS, WDDGS and WDDGS+oil (220, 253, and 265 g d −1 ) compared with the control (143 g d −1 ). Although oil appears to be responsible for reducing CH 4 emissions when DDGS is included in the diet, increased N excretion requires that a complete life cycle assessment be conducted to assess the full impact of DDGS on greenhouse gas emissions from finishing cattle.
