Responses of body composition, growth and food efficiency to dietary protein in genetically lean and fat broilers up to seven weeks of age

1. Growth, food intake and abdominal fatness were measured at 7 weeks of age in male and female broilers from genetically lean and fat lines fed on isoenergetic diets containing 160, 190, 210, 230 and 260 g crude protein/kg from hatching. 2. The mean proportions of abdominal fat decreased from 39 to 20 g/kg body weight in the fat line and from 26 to 11 g/kg in the lean line over this range of protein concentrations. 3. Protein requirements, for optimum growth as a proportion of the diet did not differ between the lines but the lean line was less tolerant of inadequate dietary protein. 4. In birds fed on the same diet, conversion efficiencies of food (FCE) and dietary protein (PCE) were always superior in the lean line but energetic efficiency (EE) was similar in good growing birds of both lines. 5. When dietary protein was adequate for growth and body compositions were equalised in the two lines (by feeding higher protein diets to the fat line), lean line birds had 10% better FCE, 6% better EE and 33% better PCE. 6. It is concluded that genetic selection is a more effective and economic means of producing leaner broilers than dietary manipulation.     

Plasma oestrogen and triglyceride concentrations and reproductive characteristics of broiler chickens after ten generations of selection at seven weeks of age for high or low plasma very low density lipoprotein concentration.

1. Day old female chicks from two lines of broilers, selected for high or low plasma concentrations of very low density lipoproteins, were fed ad libitum or restricted until point of lay. All birds were fed ad libitum after laying an egg, and aspects of growth and reproduction were measured to 40 weeks of age. 2. Compared with lean line birds the growth rate of fat line females fed ad libitum declined from 16 weeks of age. 3. Mortality from apparently stress-related causes in ad libitum fed fat line females increased from 16 weeks of age and was 71% overall, compared with 26% in ad libitum fed lean line females. Mortality in the corresponding restricted birds was 20% and 7%, respectively. 4. Few fat line females fed ad libitum commenced lay and those which were restricted during rearing stopped laying after the initiation of ad libitum feeding. Egg productions in lean line birds fed ad libitum or restricted were similar. 5. Fat line females fed ad libitum had few yellow follicles and a high rate of atresia at first egg and between 37 and 39 weeks, as did restricted fat line birds between 37 and 39 weeks of age after being fed ad libitum. 6. Plasma concentrations of oestradiol-17 beta were 5-fold higher in fat compared with lean line females at 35 weeks of age. There was a similar large difference in concentrations of plasma triglyceride which reached 59 mg/ml in fat line females fed ad libitum.     

Relationship between body fatness,ovarian structure and reproduction in mature females from lines of genetically lean or fat broilers given different food allowances

1. Reproductive and other characteristics were measured at 34 and 60 weeks of age in broiler breeder hens on 6 different feeding regimes. The hens came from genetically lean and fat lines selected on the basis of low or high 7‐week plasma very low density lipoprotein (VLDL) concentration.

2. Plasma VLDL concentrations were consistently higher at all ages in fat line hens but were not affected by dietary treatment.

3. Mature body weight did not differ between the lines in birds fed ad libitum but with food restriction throughout life, fat line birds were lighter at 34 weeks.

4. There was little difference between the lines in abdominal fatness of birds fed ad libitum up to 60 weeks. Fat line birds were always fatter than lean line counterparts under food restriction.

5. Egg production was higher in lean line birds fed ad libitum but food restriction improved egg production in both lines. Peak egg productions were similar in both lines but there was evidence that the optimal food allowances for egg production was higher in the lean compared with the fat line.

6. Ovarian yellow follicle numbers were highest at 34 weeks in ad libitum fed lean line birds and declined linearly with decreasing body weight caused by food restriction but there was no such relationship in fat line birds.

7. White follicle numbers were higher and follicular atresia was lower in the lean line.

8. It is concluded that poor reproduction in fat line birds was associated with inhibition of follicular development and atresia rather than by high plasma VLDL concentrations promoting excessive yolk formation.     

The effects of dietary protein independent of essential amino acids on growth and body composition in genetically lean and fat chickens

1. Growth performance between 28 and 49 d of age and carcase composition at 49 d in genetically lean (LL) and fat (FL) broilers fed on diets varying in non-essential amino acid (NEAA) concentrations were compared in 2 experiments. In experiment 1, 3 crude protein (CP) contents (133, 155, and 178 g/kg) were compared. In experiment 2, 4 CP levels (131, 150, 170 and 189 g/kg) were compared. All diets were supplemented with synthetic amino acids to cover the EAA requirement of the LL birds. 2. Weight gains of FL chickens were not affected by dietary treatments, while those of LL increased when CP level increased. 3. Reducing CP content always increased body lipids, abdominal fat and food conversion ratio in both lines in both experiments; however, the effect on abdominal fat was more pronounced in the FL birds. 4. Reducing CP concentration always decreased breast muscle proportion in both lines in both experiments, even when growth rate was not affected by CP. 5. It is concluded that LL chickens require diets more concentrated in NEAA than fat chickens and that there seems to be an effect of NEAA on breast muscle development.     

Effect of different dietary levels of protein on fat deposition in broilers divergently selected for high or low abdominal adipose tissue.

1. Male broilers selected for high (HF) or low (LF) abdominal fat were fed from 8 to 53 d of age on diets containing different concentrations of protein: according to N.R.C. (1984) recommendations (IP), 14% lower (LP) or 14% higher (HP). 2. The growth of LF birds fed on the LP diet was depressed until 35 d of age, but did not differ from the other groups later on. 3. The HF birds had heavier adipose tissues (AT) (g/kg body weight) than the LF birds. Significant line by diet interactions indicated a difference in magnitude of the response of the lines to dietary protein content. 4. Fat concentration of the AT and skin was higher, and in the tibia lower in the HF than in the LF birds. The fat concentration in liver and in breast muscle was not affected by line or by diet. 5. The ratio of saturated plus monoenoic fatty acids to polyenoic fatty acids, considered as an index of fat synthesis, was higher in the abdominal adipose tissue (AAT) of HF compared with LF birds. In AAT, liver and in breast muscle, this ratio was inversely related to dietary protein content.     

The influence of dietary protein content on the performance of genetically lean or fat growing chickens

Genetically lean or fat male chickens were fed from 3 to 8 weeks of age on four diets of different protein content: 152, 172, 191 or 211 g/kg. The two lower protein contents depressed growth of lean chickens but had no adverse effects on fat chickens. In both lines increasing dietary protein decreased food: gain ratio and abdominal fat desposition relative to live body weight. Protein deposited and the efficiency of utilisation of dietary protein were higher in all instances in lean birds.     

Growth, development, and carcass composition in five genotypes of swine.

An experiment with 127 barrows representing five genotypes, 1) H x HD, 2) SYN, 3) HD x L[YD], 4) L x YD, and 5) Y x L (H = Hampshire, D = Duroc, SYN = synthetic terminal sire line, L = Landrace, and Y = Yorkshire), was conducted to evaluate growth and development of swine from 59 to 127 kg live weight. Animals were allowed ad libitum access to a pelleted finishing diet containing 18.5% CP, .95% lysine, and 10.5% fat, with an energy density of 3,594 kcal of ME/kg. Pigs were serially slaughtered at either 59, 100, 114, or 127 kg live BW. After slaughter, carcasses were chilled and backfat was measured at four locations. The right side of each carcass was fabricated into primal cuts of ham, loin, Boston Butt, picnic, and belly. Composition of each primal cut was determined by physical dissection into lean, fat, bone, and skin. Estimated allometric growth coefficients for carcass length, carcass weight, and longissimus muscle area relative to BW; carcass lean, fat, bone, and skin relative to both BW and carcass weight; and lean in each of the primal cuts relative to total carcass lean did not differ (P greater than .05) among genotypes. Relative to BW, the pooled growth coefficient(s) for carcass weight was (were) greater (P less than .001) than unity, whereas those for carcass length, longissimus muscle area, and backfat at first rib were smaller (P less than .001) than unity. Those for other backfat measurements were close to 1.00. Relative to either BW or carcass weight, the pooled coefficient(s) for fat was (were) greater (P less than .001) than unity, whereas those for lean, bone, and skin were smaller (P less than .001) than unity. Growth of lean, backfat, bone, and skin in the carcass were nearly linearly associated with increases in BW. The increase in fat weight was curvilinear as the pig grew and was accelerated in later growth stages, indicating that carcass fat percentage increased with increased BW.     

Selection against abdominal fat percentage may increase intramuscular fat content in broilers

Excessive abdominal fat content (AFC) has negative impacts on feed efficiency and carcass quality. Unlike AFC, intramuscular fat content (IMFC) could be a favourable trait, which has a positive impact on meat quality. To meet consumers' needs, a long‐term goal of broiler breeders is to decrease AFC and improve the IMFC simultaneously. The current study was designed to investigate the relationship between AFC and IMFC and to compare IMFC, including the pectoral major muscle fat content (PIMFC) and intramuscular fat content of leg muscle (LIMFC), between two broiler lines divergently selected for abdominal fat percentage over 17 generations. The results showed that there was a significant difference in PIMFC and LIMFC between the two lines in all five generation populations used. The birds in the lean line had significantly lower AFC but higher PIMFC and LIMFC than the birds in the fat line. We also detected differences in the liver fat content (LFC) between the two lines and the results showed that birds in the fat line had significant higher LFC than birds in the lean line. Our results indicated that a desirable broiler line with higher IMFC but lower AFC could be obtained by genetic selection.     

Studies on acid oils and fatty acids for chickens. I. Influence of age,rate of inclusion and degree of saturation on fat digestibility and metabolisable energy of acid oils 1

1. Using a multi‐rate assay, 3 commercial acid oils (sunflower, soya‐bean and tallow) were evaluated for AMEn and added fat digestibility with broiler chicks, at 11, 25, 39, 53 and 60 d of age. The regression equations of AMEn values or ME of available fat on rate of inclusion of fat were calculated.

2. Significance was achieved for linear regression but not for quadratic regression in both variables; neither rate of inclusion nor age of birds (except for tallow acid oil at 25 d) significantly affected the AMEn or ME of fat. Metabolisable energy of fat (on a dry matter basis) calculated from combined linear regression equations was 19–14 MJ/kg for sunflower acid oil, 18–09 MJ/kg for tallow acid oil and 27–94 Mj/ kg for soyabean acid oil. Differences between sunflower and soyabean acid oils were attributed to variations in unsaponifiable and non‐eluted material of both fats.

3. Abdominal fat pad weight and its relationship to carcase weight were also studied with birds slaughtered at 67 d of age. Chicks given tallow acid oil deposited larger amounts of abdominal fat, and this deposition was directly related to the rate of inclusion of acid oil in the diet.     

Effects of winter stocker growth rate and finishing system on: II. Ninth-tenth-eleventh-rib composition, muscle color, and palatability

Angus-cross steers (n = 198; 270 kg; 8 mo) were used in a 3-yr study to assess the effects of winter stocker growth rate and finishing system on 9-10-11th-rib composition, color, and palatability. During the winter months (December to April), steers were randomly allotted to 3 stocker growth rates: low (0.23 kg/d), medium (0.45 kg/d), or high (0.68 kg/d). At the completion of the stocking phase, steers were allotted randomly within each stocker growth rate to a high concentrate (CONC) or to a pasture (PAST) finishing system. All steers were finished to an equal time endpoint to minimize confounding due to animal age. At the end of the finishing phase, steers were transported to a commercial packing plant for slaughter and a primal rib (NAMP 107) was removed from 1 side of each carcass. The 9-10-11th-rib section was dissected into lean, fat, and bone, and LM samples were analyzed for palatability and collagen content. Hot carcass weight and 9-10-11th-rib section weight were greater (P = 0.01) for high than low or medium. Winter stocker growth rate did not alter 9-10-11th rib composition. The percentage of fat-free lean, including the LM and other lean trim, was greater (P = 0.001) for PAST than CONC. Total fat percentage of the 9-10-11th-rib section was 42% lower (P = 0.001) for PAST than CONC due to lower percentages of s.c., intermuscular, and i.m. fat. The percentage of total bone in the 9-10-11th-rib section was greater (P = 0.001) for PAST than CONC. Finishing beef cattle on PAST increased (P = 0.001) the percentage of lean and bone and reduced (P = 0.001) the percentage of fat in the carcass based on published prediction equations from 9-10-11th rib dissection. Stocker growth rate did not influence the objective color scores of LM or s.c. fat. Longissimus muscle color of PAST was darker (lower L*; P = 0.0001) and less red (lower a*; P = 0.002) than CONC. Juiciness scores were greater (P = 0.02) for CONC than PAST. Initial and overall tenderness scores as well as Warner-Bratzler shear force values did not differ (P > or = 0.28) among finishing systems. Beef flavor intensity was lower (P = 0.0001) and off-flavor intensity greater (P = 0.0001) for PAST than CONC. Total collagen content was greater (P = 0.0005) for PAST than CONC; however, there were no differences in percentage soluble or insoluble collagen. Growth rate during the winter stocker period did not influence rib composition, color, or beef palatability. Finishing steers on forage reduced fat percentages in the rib and LM without altering tenderness of beef steaks.     

Dietary lutein and fat interact to modify macrophage properties in chicks hatched from carotenoid deplete or replete eggs

Two experiments were conducted to study the interaction between dietary lutein and fat levels in broiler chicks hatched from lutein depleted (Experiment I) and repleted (Experiment II) eggs. In both experiments, a 2 x 3 factorial arrangement of treatments resulted in six dietary treatments (fat at 3% and 6% and lutein at 0, 25 and 50 mg/kg feed) that were fed for 23 days to 18 birds per treatment (in three replications). In Experiment I, the anti-dinitrophenyl-keyhole-lympet-hemocyanin (anti-DNP-KLM) serum antibody response at day 22 and macrophage phagocytotic index at day 17 did not differ among treatment groups (p > 0.05). The concavalin A and phytohaemagglutinin-P lymphocyte proliferation index at day 19 was greater in birds fed 50 mg of lutein and 3% fat than in birds fed all other diets (p < 0.05). Independent of the level of dietary fat, dietary lutein increased macrophage (day 23) nitrite production measured 46 h after in vitro stimulation with LPS (p < 0.05). Among the birds fed lutein at 25 or 50 mg/kg feed, birds fed 3% fat had higher LPS-induced nitrite production compared to the birds fed 6% fat after 46 (p = 0.014) or 70 h (p < 0.001). In Experiment II, macrophage nitrite production was measured at 54 h after LPS stimulation on days 11, 15, 19 and 23. An interaction between dietary lutein and fat levels on nitrite production was observed on day 19 (p = 0.012), where macrophages from birds fed 0 mg lutein and 3% fat had the highest nitrite production (p = 0.012). Macrophages from birds fed lutein at 25 and 50 mg/kg diet and 3% fat had higher (p = 0.012) nitrite production than birds fed 6% fat. Thus, in birds hatched from lutein deplete and replete eggs, modulation of macrophage nitrite production by lutein is dependent on the level of dietary fat.     

高、低脂系肉鸡肌肉品质的比较

本文旨在比较分析高、低脂系肉鸡肌肉品质的差异。以东北农业大学培育的高、低脂系第20世代肉鸡为试验动物,采用常规肉品质检测方法,测定肌肉的物理性状、化学性状、组织学特性以及风味物质,并比较这些性状在两系间的差异。结果表明:1)物理性状方面,高脂系肉鸡胸肌的蒸煮损失和滴水损失显著或极显著高于低脂系肉鸡(P0.05或P0.01),而胸肌的肉色亮度值(45 min)和黄度值(45 min和24 h)、pH_(24 h)、失水率和剪切力显著或极显著低于低脂系肉鸡(P0.05或P0.01);高脂系肉鸡腿肌的pH_(24 h)、滴水损失、蒸煮损失和剪切力极显著高于低脂系肉鸡(P0.01),而腿肌的肉色亮度值(45 min)和黄度值(45 min和24 h)、pH_(45 min)和失水率显著或极显著低于低脂系肉鸡(P0.05或P0.01)。2)化学性状方面,高脂系肉鸡胸肌和腿肌的水分和粗蛋白质含量显著或极显著高于低脂系肉鸡(P0.05或P0.01),而粗脂肪含量极显著低于低脂系肉鸡(P0.01)。3)组织学特性方面,高脂系肉鸡胸肌的肌纤维直径显著高于低脂系肉鸡(P0.05),腿肌的肌纤维密度极显著高于低脂系肉鸡(P0.01)。4)风味物质方面,高脂系肉鸡胸肌的甜鲜味氨基酸、必需氨基酸和总氨基酸含量显著或极显著高于低脂系肉鸡(P0.05或P0.01);高脂系肉鸡胸肌和腿肌的多不饱和脂肪酸和必需脂肪酸含量极显著低于低脂系肉鸡(P0.01)。总体而言,高、低脂系肉鸡肌肉的理化性状、组织学特性和风味物质含量差异显著,说明长期对腹脂性状的双向选择会在一定程度上影响肉鸡的肌肉品质。     

The effect of selection for rapid lean growth on the dietary lysine and energy requirements of pigs fed to scale

A line of pigs (S line) selected for weight of ham lean, a measure of lean growth, was compared with an unselected control line (C line) of common origin on a series of food regimens ranging in average daily intake from 23.7 to 27.2 MJ digestible energy and from 13.3 to 23.4 g total lysine. The comparison was made over a 12-week test period starting at 25 kg liveweight and measurements were made of growth rate, fat depth by ultrasonics and, from these, predicted weight of lean in the ham at the end of test. As energy and lysine in the diet were increased, growth rate and ham lean rose at rates and reached limits which were higher in the S than the C line. As a result of 4.4 standard deviations (SD) of selection differential accumulated over five generations of selection, the superiority of the S over the C line in ham lean ranged from 0.5 (SD) on a low energy-lysine diet to 2.7 SD on a high energy-lysine diet. Maximum growth rate and ham lean were reached in the S line on a diet which provided 1 MJ day⁻¹ more digestible energy and 3 g day⁻¹ more total lysine than the diet at which the maxima were reached in the C line. Increasing dietary energy raised fat depths in the C line and increasing lysine lowered fat depths in the S line. Pigs from both lines were most profitable on diets lower in energy and lysine levels than those which gave maximum growth. Net monetary returns were most responsive to changes in energy in the C line and to changes in lysine in the S line.     

Apparent metabolisable energy and digestibility of shea (Vitellaria paradoxa) fat, cocoa (Theobroma cacao) fat and soybean oil in broiler chicks

1. The objective of this experiment was to determine and compare the apparent lipid digestibility coefficient and apparent metabolisable energy (AME) value of shea nut (Vitellaria paradoxa, Gaertn.) fat in broiler chickens with that of soybean oil and cocoa fat. 2. One hundred and sixty 13-d-old male broiler chicks were used in a randomised complete block design. The fats were added at 30, 60 and 90 g/kg to a basal diet. A tenth dietary treatment was the basal feed with no added fats or oils. The birds were fed on the diets for 8 d and all droppings were collected for the final 4 d. 3. The mean coefficient of apparent lipid digestibility for shea fat (0.58) was similar to that of cocoa fat (0.54) but lower than that of soybean oil (0.95). There was evidence of a lipid x concentration interaction with the 90 g/kg shea fat diet having low lipid digestibility (0.43). 4. There was an interaction between the effects of dietary lipid concentration and test lipid on AME but, at dietary levels of 60 g/kg and below, the AME of shea fat (22.0 MJ/kg DM) and cocoa fat (26.4 MJ/kg DM) was significantly lower than that of soybean oil (39.8 MJ/kg DM).     

Comparison of feed energy costs of maintenance, lean deposition, and fat deposition in three lines of mice selected for heat loss

Three replications of mouse selection populations for high heat loss (MH), low heat loss (ML), and a nonselected control (MC) were used to estimate the feed energy costs of maintenance and gain and to test whether selection had changed these costs. At 21 and 49 d of age, mice were weighed and subjected to dual x-ray densitometry measurement for prediction of body composition. At 21 d, mice were randomly assigned to an ad libitum, an 80% of ad libitum, or a 60% of ad libitum feeding group for 28-d collection of individual feed intake. Data were analyzed using 3 approaches. The first approach was an attempt to partition energy intake between costs for maintenance, fat deposition, and lean deposition for each replicate, sex, and line by multiple regression of feed intake on the sum of daily metabolic weight (kg(0.75)), fat gain, and lean gain. Approach II was a less restrictive attempt to partition energy intake between costs for maintenance and total gain for each replicate, sex, and line by multiple regression of feed intake on the sum of daily metabolic weight and total gain. Approach III used multiple regression on the entire data set with pooled regressions on fat and lean gains, and subclass regressions for maintenance. Contrasts were conducted to test the effect of selection (MH - ML) and asymmetry of selection [(MH + ML)/2 - MC] for the various energy costs. In approach I, there were no differences between lines for costs of maintenance, fat deposition, or protein deposition, but we question our ability to estimate these accurately. In approach II, selection changed both cost of maintenance (P = 0.03) and gain (P = 0.05); MH mice had greater per unit costs than ML mice for both. Asymmetry of the selection response was found in approach II for the cost of maintenance (P = 0.06). In approach III, the effect of selection (P < 0.01) contributed to differences in the maintenance cost, but asymmetry of selection (P > 0.17) was not evident. Sex effects were found for the cost of fat deposition (P = 0.02) in approach I and the cost of gain (P = 0.001) in approach II; females had a greater cost per unit than males. When costs per unit of fat and per unit of lean gain were assumed to be the same for both sexes (approach III), females had a somewhat greater estimate for maintenance cost (P = 0.10). We conclude that selection for heat loss has changed the costs for maintenance per unit size but probably not the costs for gain.     

Effect of recombinant porcine somatotropin on energy and protein utilization by growing pigs: interaction with capacity for lean tissue growth.

Three litters of four pigs from each of four different groups were used to evaluate the effect of porcine somatotropin (pST) on growth performance, body gain composition, energy and N metabolism, and in vitro cytochrome oxydase (final enzyme of the respiratory chain) activity of tissues. The four groups included boars from a synthetic line (SG1) or the Large White breed (SG2) and barrows from the Large White breed (SG3) or crossbred between Large White and Meishan breeds (SG4). Inherent capacity for daily lean tissue growth (LTG) decreased from SG1 to SG4. Within a litter, one pig was slaughtered and dissected at the beginning of the experiment (55 kg BW) and the three others were fed the same daily supply of protein and amino acids (26 g of lysine/d) but relative daily energy levels were either 113 (without pST: E1/0), 100 (3 mg of pST/d: E2/pST) or 87 (3 mg of pST/d: E3/pST). The 100 energy level corresponded to the ad libitum intake of E2/pST pigs. Two energy and N balances were carried out in respiration chambers during the experimental period. Pigs were slaughtered and dissected at approximately 95 kg BW and composition of gain was estimated using the comparative slaughter technique. In E1/0 pigs, daily BW, lean, and N gain were affected (P less than .01) by group; 566, 471, 374, and 315 g/d of lean tissue gain in SG1, SG2, SG3, and SG4 pigs, respectively. At high ME intake (E2/pST vs E1/0), pST increased daily BW (+14%), lean (+27%), or N (+26%) gain and reduced adipose tissue (-50%) gain, but the pST effect was inversely related to LTG: for N, the improvement was 2.8, 7.1, 7.0, and 11.1 g/d in SG1, SG2, SG3, and SG4 groups, respectively. Energy restriction (E3/pST vs E2/pST) reduced (P less than .001) adipose tissue gain in all groups but did not affect lean tissue or N gains in SG1, SG2, and SG3 pigs. In the pST-treated pigs of the SG4 group, the lean tissue or N gains were reduced (P less than .01) by energy restriction. Energy restriction combined with pST treatment (E3/pST) led to negligible amounts of fat deposited (40 g/d for SG1 + SG2 + SG3 pigs) and a gain:feed ratio higher than 500 g/kg (580 in SG1 pigs). The increased heat production measured in pST-treated pigs was due to its maintenance component: 275 vs 257 kcal of ME.kg BW-.60.d-1 (P less than .01).(ABSTRACT TRUNCATED AT 400 WORDS)     

Effect of trimethylamine oxide and betaine in swine diets on growth performance, carcass characteristics, nutrient digestibility, and sensory quality of pork.

Two growth experiments and one digestibility experiment were conducted to study the effect of trimethylamine oxide (TMAO) and betaine in swine diets. In Exp. 1, 36 limit-fed pigs averaging 19.1 kg in initial weight were used to study the effect of adding TMAO at 10 g/kg of feed or betaine at an equivalent level of methyl groups (10.5 g/kg feed) to a high-fat (11.3% ether extract) basal diet. Dietary addition of TMAO increased ADG by 61 g/d, reduced number of days to market by 8.3 d (P<.02), and tended (P<.09) to improve gain/feed (G/F) compared with the control diet. Betaine had no effect on growth performance of pigs. Adding TMAO or betaine to diets had no effect on percent carcass fat, percent carcass lean, or dressing percentage. Dietary supplementation of TMAO reduced (P<.05) plasma triacylglycerol level (TAG) compared with the control diet. There was no effect of dietary TMAO or betaine on sensory quality characteristics of pork. In Exp. 2, 48 ad libitum-fed pigs averaging 21.7 kg initial BW and 104.7 kg final BW were used to determine the effect of adding low and intermediate levels of TMAO (1, 2, or 5 g/kg) to diets. Adding 1 g of TMAO increased G/F (P<.01) compared with control pigs. When using orthogonal contrasts, adding 2 g of TMAO reduced (P<.05) P2 backfat thickness and tended to increase (P<.09) lean percentage compared with the control diet. Trimethylamine oxide gave a quadratic effect (P<.05) on plasma TAG levels. Adding 1 and 2 g of TMAO increased plasma TAG, but 5 g of TMAO decreased it compared with the control diet. In Exp. 3, 12 barrows of 42.3 kg average initial BW and 50.0 kg final BW were used to investigate the effect of supplementing diets with 1 g of TMAO and 1.27 g of betaine/kg of feed on apparent total tract nutrient digestibility. The addition of TMAO increased (P<0.03) apparent total tract digestibility of fat (HCl-EE). Betaine had no such effect. Adding TMAO to diets influenced growth performance and carcass quality in a dose-dependent manner.     

Effects of exogenous porcine somatotropin (pST) administration on growth performance, carcass traits, and pork meat quality of Meishan, Pietrain, and crossbred gilts

Seventeen to twenty-three females of lean (Pietrain, PI), fat (Meishan, MS), or intermediate genotype (PI x [3/4 Large White x 1/4 MS]), referred to as crossbred (CR), were injected between 60 and 100 kg live weight with 6 mg/d of porcine somatotropin (pST) and compared to similar numbers of control females receiving the vehicle only. Average daily gain increased similarly in the three genotypes (125 g/d). Feed conversion ratio tended to decrease to a higher extent in MS (-2.0 kg of feed/kg of gain) than in the other two genotypes (-1.1 and -.9 kg of feed/kg of gain for CR and PI, respectively). A significant genotype x treatment interaction was also observed for backfat thickness (BF) and fat, muscle, and bone development. Effects of pST in PI, CR, and MS pigs were, respectively, -6.2, -9.6, and -16.1 mm for BF and 3.0, 6.8, and 11.8% carcass muscle. The influence of pST on physical measurements of meat quality was rather low, although desirable effects (P less than .05) were obtained on the reflectance and water-holding capacity of PI and CR. Intramuscular fat content was reduced by approximately 1% in MS and CR but not in PI. The metatarsals of pST-treated animals had a higher water content (except in PI), a lower mineralization, and a lower breaking strength (except in MS). The existence of breed variations in the response to pST might result in changes of the relative merit of crossbreeding schemes.     

Phenotypic measurements and various indices of lean and fat tissue development in barrows and gilts of two genetic lines from twenty to one hundred twenty-five kilograms of body weight

Two genetic lines with different lean gains were evaluated for various body measurements and indices of lean tissue in barrows and gilts from 20 to 125 kg of BW. One genetic line was identified as the low-lean line [280 g of fat-free lean (FFL)/d], and the second line was the high-lean line (375 FFL gained/d). The experiment was conducted as a completely randomized design using a 2 x 2 x 5 factorial arrangement of treatments in 6 replicates (n = 120 pigs). The 2 genetic lines and sexes were provided ad libitum access to cornsoybean mixtures that met or exceeded their required amino acid requirements for their respective lean gain potentials. Six pigs of each sex and genetic line were slaughtered initially and at 25-kg of BW intervals to 125 kg of BW. Pigs slaughtered were measured for height, width, and length using metal calipers. Backfat and LM area were measured using real-time ultrasound, with backfat depth also measured using A-mode ultrasound technology. Longissimus muscle area and back-fat thickness at the 10th rib were measured on the chilled carcass. Data was analyzed using the MIXED procedure of SAS, with the animal as the experimental unit. Shoulders (P < 0.05) and lumbars (P < 0.05) were wider in the low-lean genetic line and in barrows. Gilts and the high-lean genetic line had less backfat and greater LM areas than the low-lean genetic line. As BW increased, there was a greater increase in FFL tissue and lower backfat depths in the high-lean vs. the low-lean genetic line. This resulted in a greater divergence of measurement values as BW increased. Femur weight, length, and cortical wall thickness were greater in the high-lean genetic line, but the differences were not significant. The high-lean genetic line had a greater (P < 0.01) organic matrix content in the femur and less ash, resulting in a lower percentage of bone ash (P < 0.01). The results indicate that differences occurred phenotypically between pigs having more muscle (wider hams) or more fat (wider shoulder and lumbar). As BW increased, the high-lean pigs had an increase in lean tissue, particularly after 75 kg of BW, and less backfat and less bone mineralization, whereas the low-lean line pigs had increased backfat and greater bone mineralization. Real-time ultrasound measurements using various formulas to estimate lean tissue produced values close to those determined from carcass measurements at 100 and 125 kg of BW.     

High dietary niacinamide and performance of male poults at 16 weeks of age

1. Male poults were fed diets with 50 and 100 mg supplemental niacinamide/kg and grown at stocking densities of 3.2 and 4.3 birds/m2 from 56 to 112 d. 2. At 50 mg/kg niacinamide high stocking density (HSD) depressed 112 d body weight and gain from 56-112d. High dietary niacinamide (100 mg/kg alleviated the growth depression under HSD but decreased body weight gain under low stocking density (LSD). 3. Dressed yield and hock width were not affected by dietary niacinamide or stocking density. 4. Dressed carcase composition was altered by stocking density. The dressed carcase of HSD birds contained 3.7% more protein and 7% less fat. 5. High dietary niacinamide tended to increase carcase protein (+2.4%) and decrease carcase fat (-4.0%).