Effects Of Dietary Protein Supply Research Articles

Interactions of amino acids and hormones regulate the balance between growth and milk protein synthesis in lactating rats fed diets differing in protein content.

Insulin-like growth factor-I (IGF-I), growth hormone (GH), and prolactin (PRL) play important roles in milk protein synthesis, and their plasma concentrations were reported to be affected by dietary protein intake. To investigate the relationship between circulating amino acid (AA) and concentrations of these hormones, 18 Wistar rats aged 14 wk were assigned to a low (LP; 9% protein), standard (SP; 21% protein), or high-protein (HP; 35% protein) diet from parturition through day 15 of lactation. Plasma, liver, pituitary gland, skeletal muscle, and mammary gland samples were collected at the end of treatment. Circulating and hepatic IGF-I concentrations increased linearly with elevated dietary protein concentrations (P < 0.0001). Rats receiving the HP diet had higher circulating GH (P < 0.01) and pituitary PRL concentrations (P < 0.0001) but lower pituitary GH concentration (P < 0.0001) relative to those in rats receiving the LP and SP diets. Pearson correlation test performed on composed data across treatments showed that several circulating AAs were correlated with circulating and tissue concentrations of IGF-I, GH, and PRL. Multiple linear regression analyses identified Leu, Gln, Ala, Gly, and Arg as the main AAs associated with hormone responses (R2 = 0.37 ~ 0.80; P < 0.05). Rats fed the LP and HP diets had greater Igf1 and Ghr gene expression in skeletal muscle than those fed the SP diets (P < 0.01). However, LP treatment decreased Prlr mRNA abundance in mammary glands as compared with the SP and HP treatments (P < 0.05). The HP diets increased AA transporter expression (P < 0.01) but decreased mammalian target of rapamycin (P < 0.05) and 70 kDa ribosomal protein S6 kinase 1 (P < 0.01) phosphorylation in mammary glands as compared with the LP and SP diets. The results of the present study suggested that several circulating AAs mediated the effects of dietary protein supply on concentrations of IGF-I, GH, and PRL, which in turn altered the metabolism status in peripheral tissues including the lactating mammary glands.

Effect of dietary protein supply originating from soybean meal or casein on the intestinal microbiota of piglets

Dietary composition is a major factor influencing the intestinal microbial ecosystem of pigs. To alleviate weaning-associated disorders, variations in dietary protein supply may beneficially affect microbial composition in the gastrointestinal tract of piglets. A total of 48 piglets, fitted with simple ileal T-cannulas, was used to examine the effect of protein supply of either highly digestible casein or less digestible, fiber-rich soybean meal (SBM) on the composition of the intestinal microbiota. Gene copies of 7 bacteria groups were determined by real-time PCR in ileal digesta and feces. Ileal counts of total eubacteria, the Bacteroides-Prevotella-Porphyromonas group, Enterobacteriaceae and Clostridium Cluster XIVa were higher (P < 0.001) in the casein-based diets. Fecal counts of all analyzed bacterial groups were higher for the SBM-based diets (P < 0.001), apart from Enterobacteriaceae (P < 0.05) which were higher in the casein-based diets. Ileal counts of lactobacilli linearly increased as the crude protein level was increased up to 335 g/kg (P < 0.01). The Bacteroides–Prevotella–Porphyromonas group linearly decreased in ileal samples (P < 0.01) and increased in fecal samples (P < 0.05) as the crude protein level in the SBM-based diet was increased. Both, protein level and protein source may affect intestinal microbial balance. Higher dietary protein levels in combination with diets low in fiber contents might stimulate proliferation of protein fermenting bacteria in piglet's large intestine. Further studies are warranted to clarify, whether this would be associated with intestinal disturbances.

Effects of dietary protein supply, weaning age and experimental enterotoxigenic Escherichia coli infection on newly weaned pigs: performance

An experiment was conducted to investigate the effects of post-weaning dietary protein supply and weaning age on the performance of pigs in the absence of in-feed antimicrobial growth promoters (AGP) when artificially challenged with enterotoxigenic Escherichia coli (ETEC), a pathogen associated with post-weaning colibacillosis (PWC). The experiment consisted of a complete 2 × 2 × 2 factorial combination of two weaning ages (4 v. 6 week), two levels of dietary protein (H, 230 g CP/kg v. L, 130 g CP/kg) and challenge with ETEC (+ v. −). An additional four treatments were added to test for the effects of protein source (DSMP, dried skimmed milk powder v. SOYA, soybean meal) and AGP inclusion (yes v. no) on challenged pigs of both weaning ages. At weaning (day 0), pigs were assigned to one of the experimental treatments for 2 weeks. On day 14 post-weaning, the same standard grower ration was fed to all animals until 10 weeks of age. On day 3 post weaning, challenged pigs were administered per os with 109 cfu ETEC. The ETEC challenge had a detrimental short-term effect on performance, decreasing average daily gain (ADG) (days 3 to 6; P = 0.014) in both 4- and 6-week weaned animals. Compared with their non-infected counterparts, challenged 4-week weaned pigs on the H diet demonstrated a larger decrease in ADG immediately post infection than those on the L diet, −42% and −25%, respectively (P = 0.088). This effect was smaller in the 6-week weaned pigs, −26% and −19% for the H and L diets, respectively. Pigs fed SOYA had lower (P < 0.001) daily intake and ADG (day 0 to 14) than those fed DSMP, with 6-week weaned pigs being affected to a greater extent than 4-week weaned pigs. In the absence of AGP, increasing weaning age and decreasing dietary protein level, especially in earlier weaned pigs, may help to minimise the effects of PWC on performance, particularly in sub-optimal environments.

Effects of dietary protein supply, weaning age and experimental enterotoxigenic Escherichia coli infection on newly weaned pigs: health

Weaning is often associated with post-weaning colibacillosis (PWC), caused by enterotoxigenic Escherichia coli (ETEC). The objective was to investigate the effects of manipulating dietary protein supply and increasing weaning age on enteric health and ETEC shedding of newly weaned pigs exposed to an experimental ETEC challenge. The experiment consisted of a complete 2 × 2 × 2 factorial combination of weaning age (4 v. 6 weeks), dietary protein content (H, 230 g crude protein (CP)/kg v. L, 130 g CP/kg) and experimental ETEC challenge (+ v. −); all foods were free from in-feed antimicrobial growth promoters (AGP). An additional four treatments were added to allow the effect of protein source (DSMP, dried skimmed milk powder v. SOYA, soybean meal) and AGP inclusion (yes v. no) to be investigated in challenged pigs of both weaning ages. On day 3 post-weaning challenged pigs were administered per os with 109 cfu ETEC O149. A subset of pigs was euthanased on days 0 and 6 post weaning to assess enteric health and small intestine morphology. Both weaning age and dietary protein content affected the consequences of ETEC challenge. ETEC excretion persisted longer in the 4-week-weaned pigs than those weaned at 6 weeks. Although not significant, the numbers of ETEC shed in the faeces post infection (days 4 to 14) were higher on the H than L diet, especially in the 4-week-weaned pigs (P = 0.093). Lowering CP level led to significantly firmer faeces post challenge (days 3 to 6) and decreased colonic digesta pH. Protein level had no effect on small intestine villous heights or crypt depths. There was no significant effect of protein source on ETEC excretion or enteric health. Results suggest that increasing weaning age and decreasing the level of dietary protein, especially in earlier weaned pigs, may help to maintain enteric health and minimise the effects of PWC.

The effect of dietary protein supply on carcass composition, size of organs, muscle properties and meat quality of pigs

Abstract This study investigated the effect of dietary protein supply on growth performance, carcass composition and size of organs in pigs slaughtered at the age of 165 ± 2 d. In addition, we analysed muscle fibre properties and glycolytic potential of light muscles longissimus lumborum (LD), semimembranosus (SM), and gluteus superficialis (GS), and dark muscles infraspinatus (IS) and masseter (M) of 20 gilts and 20 barrows. Of these pigs, 16 were Finnish Landrace, 16 were Finnish Yorkshire, and 8 were crosses of these breeds. The pigs were fed low-or high-protein diets formulated to contain 6.0 and 9.5 g of apparent ileal digestible lysine/feed unit (1 fu = 9.3 MJ NE), respectively. The pigs were fed according to a restricted weight-based feeding scale (13–30 MJ NE/d). Lean meat, fat, bones, and skin of the carcasses as well as organs were dissected and weighed. The pH value was measured 45 min post mortem from LD, and 24 h post mortem from LD, SM and GS. Drip loss, lightness (L⁎) and redness (a⁎) were measured from LD, SM and GS. Pigs with a low-protein supply showed a lower growth rate (P 0.05). We found no such differences in the dark muscles studied. We also took into account the effect of both the breed and sex on the studied properties. The low-protein diet increased glycolytic potential in porcine LD and SM, and decreased the pH value measured 45 min post mortem from LD. The dietary protein supply affected no other meat quality traits studied. A more rapid drop in pH in LD resulted in a lighter and less red meat with higher drip loss.

The effect of dietary protein supply on the performance and risk of post-weaning enteric disorders in newly weaned pigs

AbstractThe effect of dietary protein supply, as manipulated by both crude protein content and/or substitution of existing ingredients, mainly soya (SOYA), with the more digestible dried skimmed milk powder (DSMP), and the consequences of removing in-food antimicrobial growth promoters (AGPs) on the performance and risk of post-weaning enteric disorders (PWED) in newly weaned pigs was investigated. Pigs weaned at 28·7±3·45 days of age (no. =49) were individually housed in an environmentally controlled room and assigned to one of seven dietary treatments; a 3×2 factorial combination of dietary protein content (130, 180 and 230 g crude protein (CP) per kg) and main protein source (DSMP and SOYA), plus an additional control containing 230 g CP per kg, DSMP and in-food AGPs (ZnO, CuSO4and avilamycin). Individual food intake, faecal score (FS), cleanliness score (CS) and health score (HS) were taken daily, and live weight and faecal samples were taken on days 0, 4, 7, 11, 12, 13 and 14. All animals were slaughtered on day 14 to examine variables describing aspects of gastro-intestinal health. Increasing CP content and the removal of AGPs both led to a significant increase in faecal fluidity and contamination although there was no effect on HS. There was no effect of DSMP inclusion on FS, CS or HS. Increasing CP content led to an increase (P&lt;0·05) in the number of coliforms in faecal and proximal colon (PC) samples taken at slaughter and a decrease (P&lt;0·01) in the lactobacilli to coliform ratio (L:C) in the PC. Increasing CP content had no effect on average daily food intake (ADFI) but led to improvements in average daily gain (ADG) (P&lt;0·001) and food conversion ratio (FCR) (P&lt;0·001) over the whole trial period. The inclusion of DSMP had no effect on performance during the 1st week, but animals on the DSMP diets had improved ADG (P&lt;0·05) and FCR (P&lt;0·01) compared with those on the SOYA diets in the 2nd week. The inclusion of AGPs increased ADFI (P&lt;0·05) and ADG (P&lt;0·05) but had no effect on FCR over the whole trial period. The results indicate that in the absence of AGPs both growth performance and the risk of PWED increased as protein supply was increased. The increased risk of PWED was associated with an increased fluidity of faeces, a reduction in the L:C ratio and an increase in intestinal pH. Consequently, it is important to balance the trade-off between maximizing performance and minimising the risk of PWED through manipulating protein supply, particularly in an environment where AGPs are no longer permitted.

Response of broilers selected on carcass quality to dietary protein supply: live performance, muscle development, and circulating insulin-like growth factors (IGF-I and -II)

The effect of dietary protein supply on muscle development and circulating concentrations of insulin-like growth factors (IGF)-I and -II was examined in chickens selected for increased breast yield and decreased fatness (quality, QL) and in its control line (CL). CL and QL chickens were fed isoenergetic diets containing 121.5 or 215.8 g CP/kg during a 12-d period; comparisons were performed at 33 d of age. Birds given the high protein diet grew faster, ate less feed, had lower feed conversion ratio (FCR), and higher muscle weights than their counterparts given the low protein diet. The muscle weight response to protein supply differed between muscles in both lines, with pectoralis major appearing more sensitive than sartorius. The response of the gastrocnemius muscle depended on the line. Selection for carcass quality increased (P < 0.01) body weight, growth rate, feed intake, pectoralis major and sartorius muscle weights, and pectoralis major muscle proportion. There was, however, no line difference in FCR or in sartorius muscle proportion. The weight and proportion of the gastrocnemius muscle were higher (P < 0.05) in the QL than the CL chickens on the high protein diet, but there was no line difference for the low protein diet. Plasma levels of IGF-I, and to a lesser extent IGF-II, were lower (P < 0.01) in protein-restricted chickens. No difference in circulating IGF-II was observed between the lines. Concentrations of IGF-I were higher (P < 0.05) in QL than CL chickens, which may contribute to improved body composition for this genotype.

Effects of dietary protein supply on caseins, whey proteins, proteolysis and renneting properties in milk from cows grazing clover or N fertilized grass.

The objective of this work was to examine whether variation in the amino acid supply to cows could be a reason for the reduced casein content and poorer renneting properties of milk that often occur in late summer, or whether these effects are related to proteolysis in the raw milk. In a 2 x 2 x 2 factorial design, we investigated the effects of sward (clover v. rye-grass) and supplementary feed with a high or low level of rumen-soluble N or of rumen undegradable protein on milk protein composition during the grazing season. A total of 32 Danish Holstein cows were included in the experiment. Milk protein and casein contents and the ratios casein N:total N and casein:true protein were at a minimum in late summer, whereas the contents of urea, non-protein N and whey protein were higher during this period. These seasonal effects were unrelated to either the type of supplementary feed or the type of sward; neither were they clearly related to proteolysis, although casein: true protein was related to the proteose peptone content. The results indicated that whey proteins other than alpha-lactalbumin or beta-lactoglobulin accounted for the higher proportion or concentration of whey protein in late summer. Based on a principal component analysis including variables such as citric acid, lactose and non-protein N, we suggest that the cows' energy supply during this period may be a critical factor in determining the milk protein composition, although our results were not conclusive. There was an interaction between the supplement of rumen undegradable protein and type of sward. When clover was grazed, a high supplement increased the concentrations of protein and casein in milk and the kappa-casein: total casein ratio. When rye-grass was grazed, the opposite response was found, and overall milk protein yield was not affected. The very low N content of clover in early summer reduced milk protein and casein protein during this period.