Market Weight Pigs Research Articles

The effect of feeding the beta-adrenergic agonist ractopamine on the behaviour of market-weight pigs

A total of 86 ad libitum fed Lacombe bred barrows and gilts weighing on average 90 kg were used to determine the effect of feeding ractopamine on animal behaviour. Four treatment groups consisted of a control (N = 22) and three levels of ractopamine (10 ppm (N = 15), 15 ppm (N = 24) and 20 ppm (N = 25) in the diet). The pigs received the ractopamine treatments for 5–6 wk prior to behavioural observations. There was little effect of ractopamine on behaviour. The ractopamine-fed pigs were observed to lie down in a group more frequently (P = 0.06) and to walk around their pen less frequently (P = 0.01). No abnormal, stereotyped, agonistic or aggressive behaviour was induced by the ractopamine. The data from the present study suggest that ractopamine, added to the diet of market-weight pigs at levels reported, does not cause marked changes in behaviour. Key words: Pig behaviour, beta-adrenergic agonists, ractopamine

Feedlot performance, carcass composition and pork quality from entire male and female Landrace and Large White market-weight pigs

A total of 80 pigs, representing Large White and Landrace boars and gilts were slaughtered at an average live weight of 92.3 kg (80.5 – 102.5 kg). Boars were housed in groups of five pigs per pen, and were individually fed to appetite twice daily for a period of 45 min. Gilts were housed in groups of 12 pigs per pen. The diet consisted of 21% crude protein with 3300 kcal kg−1 digestible energy. Carcasses were weighed on the slaughter floor and cooled at 1 °C for 24 h prior to dissection of the left side into fat, bone and lean. There were no significant breed-by-gender interactions for growth, carcass and meat quality traits. These pigs had low average backfat, when measured ultrasonically according to Canadian Swine Improvement Program standards on the live pig (gilts 12.3 mm, boars 10.1 mm), high average daily gain (ADG: gilts 880, boars 940 g d−1) and low age adjusted to 90 kg (gilts 148, boars 145 d). Large White boars had a lower feed conversion ratio (2.18 vs. 2.32, P = 0.015) and less feed intake per day (2.05 vs. 2.14 kg d−1P = 0.020) than did Landrace boars. There were no significant differences in dissected lean yield between breeds (P = 0.389) or genders (P = 0.148). However, gilts had greater carcass grade fat and greater lean depth measurements than did boars, such that both genders had a predicted lean yield of 51.8%. Gilts (40.8 cm2) had a larger (P < 0.001) longissimus dorsi area than boars (38.0 cm2). There were no breed effects on the lean content of the four major cuts (P = 0.20), but boars had less fat (P = 0.01) and more bone than gilts (P < 0.01). There were few consistent differences in subjective or objective meat quality traits (i.e. color, drip loss) among breeds or genders. Boars had muscle with greater moisture than gilts (P < 0.001) as well as softer fat (P = 0.016). Thus, it appears possible to produce pork of high quality from lean animals and that lean boars efficiently produce carcasses of equivalent yield and quality to carcasses produced by lean gilts. Key words: Swine, boar, carcass composition, meat quality, Landrace, Large White

A study of operator effects on ultrasonic measures of fat depth and longissimus muscle area in cattle, sheep and pigs.

Use of real-time ultrasonography in meat animal improvement programs has increased largely as a result of the perceived accuracy of such instruments in measuring longissimus muscle area (LMA) and fat depth (BF). The objective of this study was to examine operator effects for ultrasonic determination of BF and LMA in market-weight cattle, sheep and pigs. The day prior to slaughter, five persons scanned 45 pigs, 32 sheep and 18 cattle at the last rib using an A-mode Ithaco Model 731AM101 body composition meter (ABF) and a Johnson and Johnson Ultrasound 210DX B-mode scanner fitted with a 3.0 MHz probe. All operators measured their own B-mode recordings (OBF, OLMA); an independent, experienced technician also obtained measurements from all recordings (TBF, TLMA). Species x machine x operator interaction effects were detected (P less than .001) for ultrasonic BF. Within-species analyses also revealed that the machine x operator interaction was important (P less than .001) for all species. Analyses of ABF, OBF, TBF, OLMA and TLMA detected species x operator interactions (P less than .001) for all traits except TLMA (P less than .20). Assuming a random model with animal, operator and residual effects, variance components were estimated by maximum likelihood for each species. Repeatabilities, calculated as the intraclass correlation among animals for BF and LMA scanned and interpreted by different operators, were .13, .21 and .51 (OBF) and .28, .15 and .29 (OLMA) for cattle, sheep and pigs, respectively, indicating the importance of operator effects. Repeatabilities of TBF were .90, .42 and .68 and of TLMA were .19, .55 and .65 for cattle, sheep and pigs, respectively, indicating the importance of image interpretation in determining operator effects associated with use of the 210DX B-mode scanner. Technical training standards must, therefore, be established for operators of such equipment.

The prediction of percentage of fat in pork carcasses

Forty-seven market-weight pigs were slaughtered in order to determine percentage of chemical fat and in an attempt to determine an easily obtainable and inexpensive method to predict this value. The hams and 8-9-10 rib loin sections were removed from the left side of each carcass and dissected into subcutaneous and seam fat, individual muscles, skin and bone. Weights and chemical analysis were determined for each component. Numerous weights, measurements and specific gravity were determined on the carcass, ham and loin section of each pig. Percentage of chemical fat of each ham, loin section and carcasses was determined and correlated with the various weights and measurements taken. Stepwise regression was used to develop prediction equations using carcass data, specific gravity, ham or loin measurements or various combinations of these as dependent variables. The single best indicator of the decimal fraction of chemical fat in the pork carcass was determined to be specific gravity of the carcass half, the prediction equation using this variable had an R-square of .64. By adding 10th rib fat thickness to this equation, the R-square increased to .72. The best equation using carcass variables included 10th rib fat and marbling (R-square = .67). The loin section proved to be an accurate indicator of composition; ham measures were not as accurate as specific gravity and carcass measurements for predicting percentage of carcass fat. This research suggests that the percentage of chemical fat in the pork carcass can be predicted by an easy and inexpensive means.

The prediction of percentage of protein in pork carcasses

Determination of percentage of protein in a pork carcass is a very costly and lengthy process. Therefore, we attempted to identify an easy and economical means to predict protein content of pork carcasses. Forty-seven market-weight pigs were slaughtered. The right side of each carcass was skinned, deboned and ground for composition analysis. Carcass data were collected on the left side and specific gravity analysis was performed on the side, ham and 8-9-10 rib loin section of each carcass. The hams and loin sections were dissected into skin, bone, subcutaneous fat, seam fat and individual muscles. After these components were weighted, they were analyzed for chemical composition. Percentage of chemical protein of each animal was determined and correlated with each of the weights and measurements taken on the carcass, ham and loin sections. Stepwise regression was used to predict decimal fraction of protein using either the carcass data, specific gravity ham measurements, loin section measurements or various combinations of these. In prediction equation, specific gravity of the carcass accounted for 73.4% of the variation found in percentage of protein. Prediction equations using indicators from the ham and loin section resulted in equations with R-square values as high as .783. These results suggest that specific gravity or indicators from the carcass, ham or loin section can be employed to predict percentage of protein in pork carcasses.

INFRARED THERMOGRAPHY OF PIGS WITH KNOWN GENOTYPES FOR STRESS SUSCEPTIBILITY IN RELATION TO PORK QUALITY

Twenty five market-weight pigs averaging 92.0 kg body weight represented by eight halothane-negative with NN genotype, nine crossbred with Nn genotype and eight halothane-positive with nn genotype animals were thermographed to determine whether temperature differences were related to meat quality. Infrared thermograph analysis demonstrated no differences in mean external medial temperatures among genotypes in the live animal nor in the internal medial carcass surface. However, pigs with cooler mean side temperatures displayed a higher percent drip loss (P ≤ 0.09) and paler colored meat (P ≤ 0.03). This was particularly evident in the H+ pigs where a highly significant negative correlation between expressible juice (−0.87; P ≤ 0.01) as well as percent drip loss (−0.75; P ≤ 0.05) and mean live external medial surface temperature was observed. Furthermore, the halothane-positive pigs displayed small hot spots over the dorsal front shoulder area and over the posterior third of the animals. Key words: Infrared thermography, meat quality, pig genotype

Effect of postnatal nutritional status on subsequent growth and reproductive performance of gilts.

Two trials involving 128 gilts were conducted to determine the effect of nutritional status during the first 28 d postnatally on subsequent growth and reproductive performance. Nutritional status was altered by adjusting litter size at birth to either 6 or 12 pigs and maintaining a lactation length of either 13 or 28 d. Pigs weaned at d 13 were fed on an ad libitum basis or at 50% of ad libitum through d 28. After d 28, all pigs were fed the same diets through the first parity. By market weight (d 154) pigs recovered differences in body weight imposed during the early postnatal period. Postnatal nutritional status did not alter age at puberty. Gilts weaned at d 28 from litter size 6 produced 2.4 more (P less than .05) ova than gilts from litter size 12; however, when weaned at d 13, gilts from litter size 6 produced 2.3 fewer ova than gilts from litter size 12. Feed restriction for 15 d postweaning did not depress ovulation rate in gilts. Subsequent litter size was not affected by postnatal litter size, lactation length or feed restriction, even though growth rate and ovulation rate had been altered by treatments imposed during the first 28 d postnatally. Assuming no difference in fertilization, these data suggest that prenatal mortality was altered by the early postnatal treatments and was the limiting factor for litter size. Until factors that influence prenatal losses are characterized and controlled, the alteration of nutritional status by changes in postnatal litter size, lactation length or feeding level will not detrimentally affect subsequent litter size in gilts.

EFFECTS OF FASTING AND WATER RESTRICTION ON CARCASS SHRINK AND PORK QUALITY

One hundred and twenty market weight (90 kg) pigs were allocated at random to one of three treatments: immediate slaughter and 24 h or 48 h without feed or water after arrival at an abattoir. All pigs were removed from feed 17 h before arrival at the abattoir. Weights of body organs and the digestive tract full and emptied of digesta were recorded along with warm carcass weight. After chilling for 24 h a pork chop 25 mm thick was removed along with the commercial ham and belly from the left carcass side and frozen for later quality determinations. Live weight shrink over 48 h amounted to 6.8 kg with 75% (5.1 kg) of this loss being attributed to loss in carcass weight. The 24-h holding period also resulted in a significant loss in carcass weight (3 kg). Approximately 20% of the total shrink over 48 h was due to a reduction in digestive tract contents. Body organs showed little change in weight over the 48-h holding period apart from the liver which was reduced in weight by 14.6%. Final longissimus muscle pH was increased and muscle luminosity (fresh longissimus, cured m. semimembranosus and m. biceps femoris) decreased for both the 24-h and 48-h holding treatments but did not result in any dark, firm and dry meat. Drip loss in pork chops decreased with increased ante-mortem holding time. However, processed yields for hams and bacon were not significantly influenced by the holding period pre-slaughter. It was concluded that the time from last feeding to slaughter should be minimized to avoid losses in carcass weight and slightly darker fresh and processed meat. Key words: Fasting, carcass shrink, carcass quality, processed yield

Accretion of Fat and Muscle in Growing Swine as Assessed by Ultrasonic Methods

Body composition was measured sequentially with ultrasonic methods in growing swine at about 20, 55 and 90 kg body weight. Carcass chemical composition was determined at a body weight of about 96 kg. Growth of subcutaneous adipose tissue was mostly curvilinear over the weights studied, although it was linear at the midbody region. There were major differences in growth at contiguous adipose tissue sites. The amount of adipose tissue assessed by fat depth measurements or muscle assessed by longissimus area at 20 kg body weight (about feeder pig weight) was not highly correlated with similar measurements on the same animals at about 87 kg body weight or with carcass measurements at about 96 kg body weight. Prediction of market weight pig composition from measurements made on feeder pigs does not appear to be a viable option. Carcass chemical composition was predicted to a modest extent by live animal or carcass measurements in these animals with a relatively constant slaughter weight. Ultrasonic measurement in the live animal was as valuable as carcass measurements for these purposes. Furthermore, it was nondestructive and allowed the sequential or longitudinal assessment of the same animal.

REPRODUCTIVE PERFORMANCE AND MEAT PRODUCTION OF GILTS BRED AT PUBERTY AND RESTRICTED IN FEED INTAKE

Sixty-one gilts, bred at puberty, were fed 1.2 kg of diet daily until day 84 of pregnancy, 1.4 kg to day 99 then 1.6 kg to farrowing. Thirty of their litters were weaned at 21 days (21 W), the others within 12 h of birth (0 W); 28 of the gilts were marketed 12 ± 3 days postweaning, the others were re-bred. Twenty-two unbred gilts were treated similarly to the bred gilts and 13 additional gilts selected at 91 kg body weight were used as conventional, market weight pigs. Age at puberty averaged 164 days; bred gilts were heavier than unbred at 85 and 100 days gestation. Number of piglets born averaged 9.1 total and 8.5 alive. Carcasses of the weaned gilts were lighter in weight than those of the unbred controls and had less backfat thickness than the lighter market weight pigs; total percentage yield of trimmed, deboned meat was not affected significantly. There were no significant differences in flavor, juiciness and tenderness of loin (m. longissimus) and ham (m. semimembranosus) meat between the market weight carcasses and those of the other four groups. Weaning to breeding interval for the 21 W and 0 W gilts bred for a second time averaged 23 and 38 days and embryo mortality was 15 and 21%, respectively, at 30 ± 3 days gestation. Key words: Puberty, gilts, feed restriction, once-bred, meat quality

Aflatoxicol and Aflatoxins B1 and M1 in the Tissues of Pigs Receiving Aflatoxin

Aflatoxicol (AFL) and aflatoxins B1 and M1 were found in tissues (kidney, liver, and muscle) of feeder pigs given an estimated LD50 oral dose of B1 (1.0 mg/kg body weight) provided as a rice culture of Aspergillus flavus and of market-weight pigs fed a naturally contaminated feed, containing aflatoxin B1 at a level of 400 ng/g from corn, for 14 days. The residues in all tissues decreased with time after treatment in both groups, with no detectable residues (approximate detection limits, ng/g, B1 0.03, M1 0.05, AFL 0.01) in pig tissues from the feeding experiment 24 h after withdrawal of aflatoxin-contaminated feed. B1 and M1, when found in the feeding experiment, were at about the same levels in all tissues except the kidney, in which M1 was the dominant aflatoxin. The level of AFL, when detected, was about 10% of the B1 level.

Serum alkaline and acid phosphatase values in market weight pigs reared in a tropical environment.

SummarySerum alkaline and acid phosphatase values were studied in 47 boars and non‐pregnant gilts of six breeds; eight pure Large Whites (LW): seven pure Durocs (DR): eight pure Indigenous pigs (IND): eight three‐way cross breeds (Large White × Duroc × Hampshire) and eight two‐way cross breeds (LW × DR) raised to market weight of 60–80 kg. The breeds and sexes of pigs significantly (P < 0.01) influenced the serum alkaline phosphatase values, while the serum acid phosphatase values were significantly (P < 0.05) influenced by breed but not by sex. The interaction between breed and sex did not significantly (P > 0.05) affect the values of either enzyme.ZusammenfassungAlkalische und saure Serumphosphatase‐Konzentrationen bei Jungschweinen unter tropischen VerhältnissenAlkalische und saure Serumphosphatase wurden bei 47 Ebern und nichtgraviden Sauen 6 verschiedener Rassen bestimmt. Rasse und Geschlecht der Schweine hatten einen signifikanten Einfluß auf die alkalische Serumphosphatase (P < 0,01), während die saure Phosphatase nur durch die Rasse (P < 0,05), nicht aber durch das Geschlecht beeinflußt wurde.RésuméConcentrations des phosphatases sériques alcalines et acides chez de jeunes porcs dans des conditions tropicalesOn a déterminé la phosphatase sérique alcaline et acide chez 47 verrats et truies non gestantes de 6 races différentes. La race et le sexe des porcs ont eu une influence significative sur la phosphatase sérique alcaline (P < 0,01), alors que la phosphatase acide n'a été influencée que par la race (P < 0,05) et non par le sexe.ResumenConcentraciones de las fosfatasas séricas alcalina y ácida en los cerdos jóvenes bajo condiciones tropicalesSe valoraron las fosfatasas séricas alcalina y ácida en 47 verracos y cerdas no grávidas de 6 razas diferentes. La raza y el sexo tenían una influencia significativa sobre la fosfatasa sérica alcalina (P < 0,01), mientras que la fosfatasa ácida se hallaba solo bajo el influjo de la raza (P < 0,05) y no bajo el del sexo.

EFFECTS OF ENVIRONMENT ON PHYSIOLOGICAL AND BIOCHEMICAL PROPERTIES OF PIGS WITH FAST AND SLOW GLYCOLYZING MUSCLE

Ten Chester White (slow glycolyzing muscle) and 10 Poland China (fast glycolyzing muscle) market weight pigs were consecutively exposed for 2 days to each of four environments (25 C, 6 C, 6–43 C fluctuating six times daily, and 37 C) in the University of Wisconsin Biotron. Postmortem muscle levels of adenosine triphosphate (ATP) and glycogen were significantly lower in the Poland China animals. Initial level of phosphocreatine (PC) was lower in the Poland China animals. Lactic acid accumulation and pH decline were significantly more rapid in the Poland China animals. The 24-h color scores were, however, normal in muscles from both kinds of animals. Daily heart rate and respiration changes indicated more rapid adaptation to environmental changes in the Chester White animals. Partial pressures of blood O2 and CO2 were not significantly different between the two groups of animals and varied with environmental changes as expected.

Live and Carcass Measurements as Indicators of Lean Cut Yield in Swine

Data included a uniform group of 476 Hampshire market-weight pigs slaughtered over a 5-year period. The pooled within year, season and sex phenotypic correlations among the traits evaluated were calculated and stepwise regression was used to predict lean cut yields. Probe backfat thickness tended to be more closely associated with most traits than was carcass backfat thickness. Shoulder probe correlations were of lower magnitude than either loin or rump probes. Probe backfat thickness and carcass backfat were more closely correlated with percent lean cuts of carcass weight (−.54 and −.52, respectively) than percent lean cuts of live weight (−.43 and −.36, respectively) or weight of lean cuts (−.26 and −.23, respectively). Correlations of 0.43, 0.52 and 0.57 were obtained for loin eye area with percent lean cuts of carcass weight, percent lean cuts of live weight and weight of lean cuts, respectively.

Value of Subcutaneous Fat and Backfat Measurements on the live Animal and the Carcass as Predictors of External, Internal and Total Carcass fat in Market Weight Pigs

On a group of 36 market weight pigs, correlations between live animal backfat probes, carcass backfat measurements, weight of chemical fat in the backfat trim of the shoulder and loin, total chemical fat in the loin, shoulder and in the half carcass were studied. Correlations between external fat measurements and total fat in the carcass and cuts were significant but low. In general, these relationships were much higher in barrows than in gilts. The correlations between external fat measurements and the fat in the trimmed carcass, the internal fat in the loin and the kidney fat were not significant. In the sample of pigs under study, backfat measurements on the live animal and on the carcass were useful in predicting the chemical fat in the backfat trim, but, because of the magnitude of the correlations, were of limited value as indicators of total chemical fat in the carcass and cuts and of little use in predicting internal fat. As in most studies with pigs the carcasses from gilts were leaner than those from barrows. This was evident not only in the live animal backfat measurements, but this tendency was also reflected in the chemical composition of the carcass, the shoulder and the loin.

THE EVALUATION OF BLOOD VOLUME AND TOTAL RED CELL MASS AS PREDICTORS OF GROSS BODY COMPOSITION IN THE PIG

In a study of growth and development patterns in the pig, data were obtained on body weight, total body protein, blood volume, and red cell mass for a total of 88 pigs, ranging in live weight from 9 to 103 kg. The relationships of total body protein to the other variables were analyzed by multiple regression techniques on both an overall and stratified basis. Over the entire weight range, body weight itself explained 98% of the variability in total protein. When the analysis was restricted to pigs in the weight range of 81–103 kg the contribution of body weight in predicting total protein decreased considerably (50%), with concomitant increase in predictive value of blood volume (8%). It was concluded that blood volume and similar physiological measurements could be of major importance in predicting body composition in market weight pigs.

Body Composition of Market Weight Pigs

Body Composition of Market Weight Pigs