The use of different anabolic agents in gilts
Loading...
Files
Date
1995-07
Authors
Dias, Geraldo Paulino
Journal Title
Journal ISSN
Volume Title
Publisher
University of the Free State
Abstract
24 Crossbred gilts (Large White x Landrace) purchased as weaners were randomly
allocated to four treatment groups (n = 6) and submitted for an observation period of
three phases: Phase I, in which the animals were treated with anabolic agents
(nandrolone, clenbuterol, zeranol); Phase 2, could be seen as the anabolic agent
clearance period; and Phase 3, in which certain carcass characteristics and meat quality
parameters were measured. The trial was aimed to compare the effect of the different
anabolic agents zeranol (implants of 36 mg/pig, every three weeks, for 9 weeks),
clenbuterol (daily oral dose of 0.5 mg/pig, for 9 weeks) and nandrolone
(intramuscularly injected, 50 rng/pig, every ,3 weeks, for a period of 9 weeks), on
growth rate parameters, carcass and meat characteristics, visceral organ growth and
blood concentrations of urea, glucose, creatinine, oestradiol and the hematocrit. The
gilts were individually housed and fed a pig growth diet (16% crude protein) ad
libitum, with free access to water. Body weight of all animals were recorded every 48
hours to monitor the average daily gain (ADG) and the growth rate up to the target
liveweight of 85 kg. Weekly feed intake was monitored and the feed conversion rate
(FCR) determined for the individual animals and the mean of the groups. Backfat
thickness (P2) and eye muscle diameter were measured weekly with the aid of a sonar
apparatus in all animals, to monitor the deposition of fat and lean muscle. Blood was
sampled weekly from 4 specific animals per group for the determination of hematocrit,
blood urea, blood glucose, blood creatinine and blood oestradiol concentrations. The
clearance rate of the anabolic agents was monitored in the urine sampled every second
day from all anabolic agent treated animals following cessation of treatment. At
slaughter (85 kg liveweight), several carcass measurements were done. Visceral
organ weights were noted and meat quality parameters (water loss, cutting resistance,
pH) were determined.
Zeranol treatment revealed an improved growth rate (ADG of 727 g/d and 147.3 days
to attainment of 85 kg) compared to the control and the other treatment groups.
None of the three anabolic agents improved the FCR significantly, although the control
showed the lowest mean value (2.76 kg feed/kg liveweight gain). A tenclency for an
increase in this parameter was observed over time, in all the groups, the highest mean
value being encountered in the group treated with zeranol (3.32 kg feed/kg liveweight
gain). Overall average daily feed intake was significantly (P<0.05) greatest in the
zeranol treated animals (2.03 kg/cl). Backfat thickness (P2) deposition assessed
through ultrasonic measurements, showed no significant differences between the
treatments and the control. The diameter of the eye muscle, weekly monitored by the
same method, from the P2 site, showed significant (P<0.05) differences - the control
having the highest value (4.43 mm/week). The clearance rate of the anabolic agents
was faster in clenbuterol treated animals than in the zeranol group, while for
nandrolone group this could not be. assessed, because its metabolites in swine are still
unknown. Zeranol treated animals had a significantly (P<0.05) improved cold carcass
weight and dressing percentage (68.8 kg and 79.8% respectively). Mean values for
backfat thickness were generally high in carcasses from zeranol treated animals (PI = 13.5 mm; Pi = 14.8 mm; P3 = 16.6 mm) which leaner carcasses were obtained in the
clenbuterol group (PI = 6.7 m; P2 = 7.4 mm; P3 = 8.6 mm). The eye muscle area
(physically measured) was significantly (P<0.05) higher in the nandrolone group (34.3
cm2) compared to the Zeranol group (30.6 cm2), but not statistically different from the
control and the nandrolone group. Zeranol, clenbuterol and nandrolone treatments
did not significantly alter carcass conformation indicators. However, carcass weight
was recorded to be positively (P< 0.05) correlated to ham circumference (r = 0.52);
chest depth (r = 0.64) and chest diameter (r = 0.56).
With the exception of cutting resistance values, in which the zeranol treatment group
produced more tender meat (3.74 kg shear force) than the control and the other two
treatments, the rest of meat quality parameters measured (muscle pH; cooking loss of
water holding capacity) were not affected by the treatment with anabolic agents. No
significant differences in the weights of digesta, digestive tract and the visceral organs
(liver, kidneys, lungs, heart and spleen) were found following anabolic agent treatment.
Suppressed ovary growth (0.6 g of weight) and over-growth of the reproductive tract
(134 g uterus weight) and increased size of the vulvas were observed following zeranol
implantation of gilts. The reproductive organs from clenbuterol and nandrolone
groups were functional and apparently unaffected.
The determination of blood urea, blood glucose, blood creatinine and blood oestradiol
levels using specific kits to assess the concentrations of the metabolites and hormones
generally did not result in definite trends of increases or decreases over time. These
determinations could thus not be accurately used as possible indicators of the
metabolic status following the use of zeranol, clenbuterol and nandrolone in gilts.
It was concluded that the use of clenbuterol and nandrolone in gilts yielded no
improvements in the growth parameters. In gilts treated with zeranol, overall growth
rate was higher. Ultrasonic measurements of backfat thickness and eye muscle
diameter proved to be an inaccurate and unreliable predictor of fat thickness or
leanness of the carcass. A longer withdrawal period is necessary after an implantation
of pigs with zeranol compared to the rapid clearance realised after an oral dose of
clenbuterol. The faster growth rate obtained following the use of zeranol implants is
counteracted by higher feed costs of lean meat production and the yield of poorer ratio
of lean-to-fat content in the carcass when compared to the clenbuterol and nandrolone
treatments. The growth of the digestive tract, liver, heart, kidneys, spleen and lungs
were not affected by anabolic agent treatment, and thus the anabolic effect of zeranol
concerning growth characteristics is not through an increased gastrointestinal capacity.
The assessment of growth performance and feed utilisation efficiency through blood
levels of glucose and urea appear to be time consuming and not always practical.
Further investigations regarding blood biochemistry, ideal doses of the anabolic agents,
their metabolism and clearance rate in swine, as well as the margin of consumer's
safety, is still of crucial importance for the future legal and safe use of anabolic agents
in the pig industry. From the results obtained, it would seem that the use of these
anabolic agents for the respective treatment periods and doses in gilts are not justified.
Description
Keywords
Swine -- Feeding and feeds, Swine -- Growth, Swine -- Carcasses -- Quality, Anabolic steroids in animal nutrition, Dissertation (M.Sc.Agric. (Animal Science))--University of the Free State, 1995