Thirty-seven pigs were used to evaluate the effects of age and weaning on the level of protease in the gastric mucosa and trypsin, chymotrypsin, amylase and lipase in the pancreas. There was a positive allometry of the pancreas and gastric mucosa associated with age and with weaning to a solid diet. Increases with age in total activity of chymotrypsin, trypsin, amylase and gastric proteases were due to increases in both tissue weight and enzyme activity per gram of tissue. A general depression in pancreatic enzymatic activities, but not in gastric proteolytic activity, was found during the first week following weaning. Forty pigs were used in a second trial to evaluate the effects of age and weaning diet on the same digestive enzymes. Total activity of all enzymes assayed increased with time postweaning. Increases in total activity of lipase and chymotrypsin were due primarily to increased pancreatic weight postweaning. Amylase, trypsin and gastric protease increases were due both to increased tissue weight and increased activity per gram of tissue. There were no effects of diet on the weight of gastric mucosa or the level of activity of the gastric proteases. Pigs fed a diet containing 20% whey had larger pancreases (P less than .10) at slaughter and a greater, but nonsignificant, mean activity per gram of pancreas for all pancreatic enzymes. It appears that the pig has sufficient pancreatic and gastric enzyme activity so that performance should not be limited, with the possible exception of the period shortly after weaning. However diet digestibility and subsequent pig performance may be more directly related to the extent of release of these enzymes into the intestine and the conditions that exist therein.
We conducted three 28-d experiments involving a total of 915 pigs to assess the relative efficacy of tribasic Cu chloride (Cu2[OH]3Cl) and Cu sulfate pentahydrate (CuSO4.5H20) in diets for weanling pigs. Experiments 1 and 2 were conducted at an experiment station (University of Kentucky), and Exp. 3 was conducted at a commercial feed company's swine research facilities (United Feeds, Inc.). The basal diet was a fortified corn-soybean meal-dried whey diet (1.25% lysine) with no antimicrobials in Exp. 1 or with carbadox (55 mg/kg) in Exp. 2 and 3. In Exp. 1, 135 pigs were weaned at 27 to 31 d and fed the basal diet without or with 100 or 200 ppm Cu from Cu chloride, or 100 or 200 ppm Cu from Cu sulfate from 7.9 to 17.7 kg BW. The 200 ppm level of Cu from Cu sulfate improved ADG (P < .10), and both levels of Cu from Cu chloride tended to improve feed:gain. In Exp. 2, 150 pigs were weaned at 27 to 31 d and fed the basal diet without or with 100, 150, or 200 ppm Cu from Cu chloride, or 200 ppm Cu from Cu sulfate from 8.9 to 20.8 kg BW. Addition of 200 ppm Cu improved ADG (P < .08) and ADFI (P < .01), but not feed:gain. Source of Cu did not affect performance. In Exp. 3, 630 pigs were weaned at 16 to 20 d and fed a common diet for 10 to 12 d until the start of the experimental period. The same experimental diets as used in Exp. 2 were fed from 9.1 to 25.5 kg BW. Both Cu sources improved ADG (P < .01), and sources and levels of Cu did not differ. Liver Cu increased in pigs fed 200 ppm Cu, and Cu sulfate tended to increase liver Cu more than did Cu chloride in one experiment, but not in another experiment. The results indicate that tribasic Cu chloride is as effective as Cu sulfate in improving growth in weanling pigs.
Three experiments were conducted using crossbred weanling pigs (7.2 to 8.6 kg; 25 to 29 d of age) to determine the effect on performance and nutrient digestibility of .75% yeast culture (YC) additions to starter diets containing whey or one of two fiber sources. An 18% CP corn-soybean meal basal diet was used in all experiments. In Exp. 1 (n = 192), the addition of YC did not affect ADG, ADFI, or gain: feed ratios (G:F) of pigs fed diets without or with 15% dried whey in two 5-wk trials. In Exp. 2 (n = 174), ADG and ADFI were not affected by YC addition to diets containing no added fiber, 8% soybean hulls (SH), or 8% peanut hulls (PH) in two 5-wk trials. The addition of SH or PH did not affect ADG or ADFI; however, a YC x SH interaction (P < .05) and a YC x PH interaction (P < .10) for G:F indicated that the addition of SH or PH to the diet in the absence of YC reduced G:F, but in the presence of YC, G:F were maintained. In a 3-wk grower phase of one trial in Exp. 2 (n = 54), SH and PH additions decreased ADG (P < .005), whereas YC additions improved ADG (P < .01), particularly for pigs fed diets that also contained SH (P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)
In this study, the degree of contractile and metabolic development of myofibers in porcine LM, rectus femoris (RF), and dark and light portions of the semitendinosus (STD and STL, respectively) was determined, and their impact on meat quality was compared at the same age but different BW (trial 1) or at a given BW but different age (trial 2) in 48 Swiss Large White barrows from 12 litters after the growing and finishing period. The barrows had ad libitum (A) or restricted (R, 80% of A) feed access. In trial 1, at 113 and 154 d of age, 6 barrows in treatment A (62.1 and 99.5 kg of BW, respectively) and 6 siblings in treatment R (51.0 and 86.6 kg of BW, respectively) were slaughtered. In trial 2, a similar protocol was used except that the barrows were slaughtered at 61.3 (104 or 119 d of age, respectively) or 101.3 kg of BW (145 or 167 d of age, respectively). Muscle fibers were stained and classified as slow oxidative (SO), fast oxidative-glycolytic (FOG), or fast glycolytic (FG), and fiber area and distribution were determined. At 113 and 154 d of age, R barrows had smaller (P < or = 0.04) SO fibers in the LM, STD, and STL, smaller (P < 0.01) FOG fibers in the STL, smaller (P = 0.03) FG fibers in the LM, and smaller (P < or = 0.04) overall mean area in the LM, STD, and STL. In the STL and RF, R barrows had fewer (P < or = 0.06) FG and more (P < or = 0.08) FOG fibers than A barrows at 113 and 154 d of age. Except for smaller FOG fibers in the STD of R compared with A barrows slaughtered at the same BW, the myofiber size did not differ (P > or = 0.11). However, the LM tended to have fewer (P = 0.06) SO and more (P < 0.01) FG fibers, and the STD had more (P < 0.01) FOG fibers in R barrows. Regardless of whether R barrows were slaughtered at the same age or the same BW as the A barrows, shear force values and cooking losses were greater (P < or = 0.08) in the STD and STL of R barrows. These findings revealed that myofiber hypertrophy was impaired by feed restriction in barrows compared at the same age, but differences in myofiber size vanished at the same BW. By contrast, restricted nutrient supply affected myofiber maturation depending on the age and BW, but the impact differed between muscles. The absence of changes in myofiber type distribution among the younger-lighter and older-heavier barrows indicated that myofiber maturation was already completed in the younger-lighter barrows. Although changes in meat quality traits were affected by the feeding regimen, they were not related to myofiber characteristics.
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