Effect of dietary protein on porcine colonic microstructure and function

Twelve feeder pigs were used to determine the effects of dietary protein on colonic microstructure and function. Scanning electron microscopy indicated marked differences in mucosal structure of pigs fed 12% vs 20% crude protein. Quantitative assessment of the morphologic features of the colon, using light microscopy, indicated significant differences in the mucosa of pigs fed 12% vs 20% crude protein and significant differences between the proximal and distal portions of the colon. Morphologic changes were associated with differences in the colonic transport of fluids and electrolytes. Dietary protein principally affected the transport of sodium, bicarbonate, and acetate. The transport of total volatile fatty acids and acetate flux were significantly different between the proximal and distal portions of the colon.     

Bactericidal activity of porcine neutrophil secretions

Antimicrobial proteins in neutrophil granules exert their bactericidal activity both within the neutrophil phagolysosome and as components of neutrophil extracellular traps. This study evaluated the bactericidal activity of porcine neutrophil secretions against four bacterial pathogens of swine. Porcine neutrophils were treated with or without phorbol myristate acetate (PMA), then the resulting supernatants were incubated with Escherichia coli K-12, Streptococcus suis, Actinobacillus suis, or Pasteurella multocida, and the surviving colony forming units were enumerated. Supernatants of PMA-activated neutrophils killed an average of 95% of E. coli K-12 cells, relative to supernatants from untreated neutrophils. Inhibition of elastase activity using chloromethylketone (CMK) prior to PMA stimulation significantly reduced the bactericidal activity of the neutrophil supernatants; 57% of the PMA-induced bactericidal activity against E. coli K-12 was estimated to be elastase-dependent. The same neutrophil supernatants had lower bactericidal activity against S. suis, A. suis, and P. multocida, with 30%, 36% and 13% reduction in bacterial numbers, respectively. The cathelicidin porcine myeloid antimicrobial peptide (PMAP)-36 and lactotransferrin were among the proteins identified in the supernatants of PMA-stimulated neutrophils by mass spectrometry. These findings imply that elastase-activated proteins, such as cathelicidins, are partially responsible for the bactericidal effect of porcine neutrophil secretions, but non-elastase-dependent proteins such as lactoferrin may also contribute. Further, the secretions of activated neutrophils were effective in killing the avirulent E. coli K-12 but were less effective against the other bacteria tested, suggesting that these pathogens may have evolved mechanisms to resist neutrophil-mediated killing.     

Effects of dietary protein/phosphate restriction in normal dogs and dogs with chronic renal failure

The effects of three dietary protein intakes (1–9, 1–3, and 0–6 g protein/kg bodyweight/day) on selected aspects of protein, mineral and electrolyte balance as well as renal functions was studied in normal dogs with moderate chronic renal failure. Dietary phosphate levels varied according to the quantity of phosphate in protein sources. Within the ranges of protein intake examined in this study, protein intake did not have a significant effect on glomerular filtration rates as measured by inulin clearance or 24-hour creatinine clearance. Restricting protein intake to less than 1–9 g protein/kg bodyweight/day further reduced retention of nitrogenous waste products as measured by serum urea nitrogen concentrations, but at the expense of adequate protein nutrition. Diets providing less than 1–9 g protein/kg bodyweight/day promoted protein malnutrition characterised by hypoproteinaemia and hypoalbuminaemia in both normal dogs and dogs with renal failure. Serum protein concentrations were similar in normal and renal failure dogs, suggesting that, under the conditions of this study, normal and renal failure dogs may have similar protein requirements. Progressive dietary protein/phosphate restriction improved but did not normalise phosphate balance in renal failure dogs.     

Effects of dietary crude protein concentration during periods of feed restriction on performance, carcass characteristics, and skeletal muscle protein turnover in feedlot steers.

In Exp. 1, 36 individually penned steers (initial BW = 294 +/- 3.8 kg) were used to determine effects of dietary CP percentage and programming gain on performance and carcass characteristics. Steers were fed to achieve a predicted gain of 1.13 kg/d for the first 84 kg of gain and 1.36 kg/d for the next 124 kg of gain and were offered feed for ad libitum consumption for the final 58 kg of gain before slaughter. In these three phases of growth, steers were fed diets, sequentially, with the following CP percentages: HHH (16, 13.5, and 12.5%), LHH (9, 13.5, and 13%), or LLL (9, 9, and 9%). When predicted gain was 1.13 kg/d, ADG was greater (P < 0.01) for steers in the HHH (1.09 kg/d) vs LHH and LLL (0.83 kg/d) systems. When predicted gain was 1.36 kg/d, ADG and gain efficiency were greatest (P < 0.01) for steers in the LHH system. Overall ADG and gain efficiency were greater (P < 0.01) for steers in the HHH (1.46 kg/d, 0.194) and LHH systems (1.38 kg/d, 0.190), compared with steers in the LLL (1.21 kg/d and 0.166) system. Carcass fat thickness was lower for steers in the LHH (0.74 cm) system than for steers in the LLL system (1.09 cm). In Exp. 2, 18 individually penned steers (initial BW = 225 +/- 5.8 kg) were either offered a 13% CP diet for ad libitum intake (AL) throughout the 134-d experiment or fed a high- (16% CP; PI-HH) or low- (10% CP; PI-LH) CP diet and fed to achieve a predicted gain of 1.13 kg/d for the first 85 d of the experiment. Steers in the PI-HH and PI-LH feeding regimens were then offered a 13% CP diet for ad libitum consumption from d 86 to 134. Fractional protein accretion rate was greater (P < 0.01) for steers in the PI-HH and PI-LH feeding regimens than for steers in the AL regimen at d 92, 106, and 120. Fractional breakdown and synthesis rates were not affected (P = 0.63) by feeding regimen. Increased ADG and gain efficiency of steers during compensatory growth periods may in part be due to greater fractional accretion rates of skeletal muscle protein.     

Effects of dietary protein source on Basenjis with immunoproliferative enteropathy.

The effects of 3 experimental diets that varied only in the source of dietary protein (ie, poultry, cereal, red meat) were compared in Basenjis (n = 8) with immunoproliferative enteropathy and healthy Beagles (n = 8). Significant differences in fecal character, serum IgA concentration, and intestinal digestive and absorptive function were not induced by the different sources of dietary protein. The results of this study do not support a causal role for dietary protein source in the pathogenesis of immunoproliferative enteropathy of Basenjis.     

Effect of recombinant porcine somatotropin and dietary protein on pancreatic digestive enzymes in the pig.

This study was conducted to determine the effect of daily recombinant porcine somatotropin (rpST) injection (0 or 120 micrograms/kg BW) and dietary CP level of the feed (14 or 26% CP) on pancreatic characteristics of growing pigs. Daily injection of rpST did not affect pancreatic weight (P = .885) but did decrease pancreatic amylase content (P = .005). The ratios of amylase:protein and amylase:trypsin were also lowered by daily rpST injection (P = .002 and P = .0002, respectively). There were protein x rpST and protein x rpST x sex interactions for the ratio of amylase:chymotrypsin. The CP content of the diet had a greater effect than the injection of rpST on pancreatic characteristics. Pigs consuming the 26% CP diet had significantly higher pancreatic weight (P = .003) and greater total pancreatic chymotrypsin (P = .006) than pigs consuming the 14% CP diet. The ratios of trypsin and chymotrypsin to DNA were also higher in pigs fed the 26% CP diet (P = .007 and P = .005, respectively). These responses were not influenced by sex. Recombinant porcine somatotropin seemed to have a slight effect on porcine pancreatic characteristics; however, dietary protein had a greater effect on pancreatic characteristics in market-weight hogs.     

Effects of dietary protein deficiency on hepatic carbohydrate metabolism in geese.

This paper was aimed at following up the course of glucose in the liver of protein underfed geese. Compared to normally fed geese, liver carbohydrate metabolism in protein underfed animals can be characterised by lowering of free glucose content of in vitro glucose uptake and glycogen synthesis and reduction of carbohydrates in total oxidation. Glycogen content of the liver and rate of glucose oxidation were also lowered, but these differences were not statistically significant. Summing up our results and taking into consideration some literature data, an overall reduction of hepatic carbohydrate metabolism in protein underfed birds may be assumed.     

重组瘦蛋白对猪蛋白质代谢的影响

利用重组瘦蛋白进行动物饲养试验研究。结果表明:重组瘦蛋白对猪蛋白质代谢指标有不同程度的影响。腹腔注射0.5 mg/kg和1.0 mg/kg体重重组瘦蛋白后,血清总蛋白(TP)和球蛋白(GPs)的含量高于对照组,其中0~3周差异显著(P<0.05),而血清白蛋白(ALB)的含量只在注射后第3周有明显提高;血清天门冬氨酸转氨酶(AST)有不同程度的提高,在注射后1~3周和5~7周内明显高于对照组(P<0.05);血清碱性磷酸酶(ALP)和丙氨酸转氨酶(ALT)只有在注射0.5 mg/kg体重重组瘦蛋白后0~3周明显提高(P<0.05);注射0.1 mg/kg体重重组瘦蛋白对猪蛋白质代谢指标无明显影响(P>0.05)。     

Impacts of dietary protein level and feed restriction during prepuberty on mammogenesis in gilts

The possible roles of dietary protein level and feed restriction in regulating mammary development of prepubertal gilts were investigated. Cross-bred gilts were fed a commercial diet until 90 d of age and then divided into four nutritional regimens based on two pelleted diets (as-fed basis): a high-protein diet (HP = 13.8 MJ of ME, 1.0% total lysine, 18.7% CP) and a low-protein diet (LP = 13.8 MJ of ME, 0.7% total lysine, 14.4% CP). Nutritional regimens were as follows: 1) HP ad libitum until slaughter (n = 22, T1); 2) HP ad libitum until 150 d of age followed by LP until slaughter (n = 20, T2); 3) LP ad libitum until slaughter (n = 21, T3); and 4) HP with a 20% feed restriction until slaughter (n = 19, T4). Gilts were weighed, their backfat thickness was measured, and jugular blood samples were obtained on d 90, 150, and at slaughter to determine concentrations of prolactin, IGF-I, leptin, and glucose. Gilts were slaughtered 8+/-1 d after their first or second estrus (202.7+/-14.5 d of age). Mammary glands were excised, parenchymal and extraparenchymal tissues were dissected, and composition of parenchymal tissue (protein, fat, DM, DNA, protein/DNA) was determined. The T4 gilts weighed less (P < 0.01) and had less backfat (P < 0.01) than did gilts on other treatments on d 150 and at slaughter. Treatments had no significant effects on prolactin, IGF-I, or glucose concentrations, but there was a treatment x day interaction (P < 0.01) for leptin, with concentrations being lower at slaughter in restricted-fed (T4) vs. LP (T3) gilts (P < 0.05). There was less extraparenchymal mammary tissue (P < 0.01) in T4 gilts than in gilts from the other groups and a tendency (P = 0.13) for the amount of parenchymal tissue to be lower in T4 gilts. In conclusion, a lower lysine intake during prepuberty did not hinder mammary development of gilts, but a 20% feed restriction decreased mass of parenchymal and extraparenchymal tissues. The effect of feed restriction on extraparenchymal tissue is most likely associated with the lower fat deposition.     

Effects of parasympathominetics on porcine stillbirth.

To study the effect of 2 parasympathomimetic drugs in reduction of incidence of stillborn pigs, 84 sows and gilts were randomly allotted to 3 treatment groups. Single 1-ml injections of isotonic saline solution, carbachol (2 mg/ml), or neostigmine bromide (5 mg/ml) were subcutaneously administered to pigs of groups A, B, and C, respectively. Injections were given midway through parturition in an attempt to hasten the delivery of the last pigs in the litter, where the corresponding incidence of stillbirth is greatest. The mean time of injection was after the birth of 3.5 pigs. Total stillbirths/litter for carbachol-treated (0.23) and neostigmine-treated (0.21) pies were significantly different (P greater than 0.0001) from those for control pigs (0.88). Before injection, stillbirths/litter for control pigs (0.23) were not significantly different from those for carbachol-treated (0.18) or neostigmine-treated (0.12) pigs. After treatment, stillbirths/litter for carbachol-treated (0.06) and neostigmine-treated (0.09) pigs were both significantly different (P greater than 0.0001) from those for saline solution-treated control pigs (0.65). When injected midway through parturition, carbachol and neostigmine reduced stillbirth rate by reducing stillbirths which occur late in farrowing.     

Effects of dietary protein concentration on the response of growing chicks to methionine.

1. Experiments were conducted independently at two stations to measure the requirement for methionine in chick diets with crude protein (CP) varying in 8 steps from 140 to 280 g/kg diet (experiment 1) or from 90 to 300 g/kg (experiment 2). 2. Protein composition was the same at all protein concentrations within a trial. The diet was designed to be first-limiting in methionine and DL-methionine was added to provide 5 ratios of methionine to CP at each protein concentration. 3. Methionine required for maximum growth rate or maximum efficiency of food utilisation was estimated at each protein concentration by fitting a quadratic regression equation to the relevant data. The requirement was also estimated by fitting the Reading model to data for growth rate and methionine intake. 4. In both trials and by all three methods of estimation, the methionine requirement (g/kg diet) for maximum performance increased as a linear function of dietary CP concentration and nearly in direct proportion to CP. 5. It is concluded that diets which contain surplus protein, beyond that needed to maximise growth rate or food efficiency, need supplementation with methionine beyond that required when dietary protein is just adequate. A suitable rule for practical formulation is that methionine concentration in chick diets should be not less than 0.025 times the dietary CP concentration.     

Effects of dietary protein on whole-body protein turnover and endocrine function in young-adult and aging dogs.

Thirty-six adult female Beagles averaging 2 (young-adult) or 8 (geriatric) yr of age were used to assess the effects of graded levels of dietary protein (16, 24, or 32%) on endocrine-controlled regulation of whole-body protein turnover. Rates of whole-body protein synthesis (WBPS) and whole-body protein degradation (WBPD) were estimated using orally administered 15N-glycine and total excreta collection. Although N balance was similar for all dogs, N flux through the metabolic pool increased linearly (P < 0.05) as protein intake increased. Rates of WBPS, WBPD, or the difference between them were not influenced by age (P > 0.10). A quadratic increase (P < 0.05) in WBPS and WBPD was observed in response to dietary protein. Serum insulin-like growth factor-I (IGF-I), IGF-I-binding protein 3, and total IGF-I-binding proteins were higher (P < 0.05) in geriatric dogs than in young-adult dogs regardless of protein intake. These results indicate that dietary protein in excess of 16% may not be required to maintain N balance in young-adult and aging dogs despite the linear increase in N flux through the metabolic pool. Furthermore, age-induced changes in endocrine functionality may differ between dogs and other species.     

Effect of dietary energy restriction on retention of protein,fat and energy in broiler chickens

1. Broiler chickens were fed 60–100% of recommended energy intakes to study the effects of energy restriction on protein and fat retention.

2. At an energy retention of 179 kJ/kg W ^0·75 d, only protein was retained. At higher energy intakes, each increment in retention had a rather constant composition: about 85% energy in fat and 15% in protein. At lower energy intakes body fat was mobilised whereas protein was deposited.

3. The efficiencies of energy retention in protein and fat were estimated to be 0·66 and 0·86 respectively.

4. The rather constant composition of additional retained energy after additional energy supply provides an explanation for a linear relationship between energy intake and energy retention.