This study was conducted to determine the influence of factors on the efficiency of protein
utilization and the rate of lipid deposition and withdrawal in growing pigs. Two
experiments were conducted in total.
The first experiment involved fifty-two crossbred entire Large White x Landrace male
pigs, individually penned, which were used to test the proposition that the efficiency of
protein utilisation is influenced by the body composition of the pig at the start of the trial.
The experiment was divided into two phases: in the first period, starting at 20kg
liveweight, when 3 pigs were slaughtered to determine the initial body composition of the
pigs on the trial, the remaining 48 pigs were divided into three groups, two of which were
fed ad libitum, with 11 pigs being offered a feed high in crude protein (HP, 1979 CP/kg)
and 19 pigs being offered a low CP (LP, 166g/kg) feed. The remaining 19 pigs were fed
HP on a restricted basis; the daily allowance being 0.7 of the mean intake of those pigs fed
HP ad libitum. The objective of this initial period was to create three groups of pigs
differing in body lipid content. As each pig achieved a protein weight of approximately
5.9kg, predicted to occur when the pigs on the three treatments reached live weights of 35,
39 and 34kg respectively, the pig entered phase 2 of the trial. At this stage three pigs from
each treatment (a total of 9 pigs) were slaughtered for carcass analysis, the protein contents
being approximately 5.9kg, and lipid contents being 85,98 and 87g/kg for the 3 treatments
respectively. During phase 2, the 8 pigs fed HP in phase 1 continued to be fed HP in phase
2; 8 pigs were chosen at random from those fed LP in phase 1 and were allocated the high
CP basal feed, while the remaining 8 were given LP; and 8 of the pigs feed-restricted in
phase 1 were randomly chosen and fed HP, while the remaining 8 were given LP. All pigs
were fed ad libitum during phase 2. Four pigs from each treatment in phase 2 were
slaughtered after 1 week and the remaining 4 a week later for analysis of body
composition In the first week of the second phase of the trial protein gain was highest
(264g/d) on the pigs previously restricted and then fed HP, followed by those previously
fed LP and then HP (242g/d), with pigs previously restricted and then fed LP depositing
the least amount of protein (192g/d). Pigs fed LP or HP throughout, had protein gains of
217 and 210g/d, respectively. Efficiencies of utilization of dietary protein did not differ
significantly between treatments, however, the highest being measured in pigs fed LP
throughout (461g/kg), followed in order by those fed LP and then HP (457g/kg), those fed
HP throughout (404g/kg), those previously restricted and then fed LP (394g/kg), with those
previously restricted and then fed HP being the least efficient (372g/kg).
The second experiment involved twenty-six male and twenty-six female crossbred Large
White x Landrace pigs, individually penned, which were used to determine the maximum
rate at which growing pigs can gain lipid. The experiment was divided into three phases: In
the first, starting at 20kg live weight (56 days old), when two males and 2 females were
slaughtered to determine the initial body composition of the pigs on the trial, the remaining
24 males and 24 females were randomly allocated to their various treatments. The
treatments consisted of a feed high in crude protein (H, 197g/kg), a feed low in CP (L,
166g/kg) and three blends, namely 5OH/5OL (180g/kg) (male diet), 30H/70L (167g/kg)
(both male and female diets) and 20H/80L (162g/kg) (female diet). Six pigs from each sex
were allocated to each treatment. The EFG Pig Growth Model was used to determine the
fat contents (lipid index) on the two feeds available and the three blends, to estimate the
best times to sample pigs. It was estimated that phase 1 would terminate at 63 d, phase 2 at
70 d and phase 3 at 77 d of age. At the end of each phase two pigs from each sex and
treatment were slaughtered. The lipid contents differed significantly between treatments at
the end of phase 2 for the male pigs, with the highest being measured in pigs fed L
(108g/kg), followed in order by those fed 70L/30H (86g/kg), those fed 5OL/5OH (74g/kg),
and those fed H (68g/kg) with the least lipid content. The lipid contents of the female pigs
were highly significantly different at the end of phase 3, with the highest being measured
in pigs fed L (147g/kg), followed in order by those fed 80L/20H (124g/kg), those fed
70L/3OH (116g/kg) and the least lipid content from those fed H (115g/kg). As estimated by
the EFG Pig Growth Model, the male and female pigs fed L treatment had the highest lipid
content and those fed H treatment, achieving their target rate of lipid deposition, with the
lowest lipid content.
This study indicates that the response in protein gain and in efficiency of utilization of
protein of pigs to a given feed is dependent on the amount and quality of the feed given to
the animals previously. Also, the maximum rate of lipid deposition can be achieved by
monitoring the changes in lipid deposition over a period of time, which enables an
enhanced understanding of the theory of food intake regulation in a growing pig. As a
result, accurate changes can be made when designing a phase-feeding program for growing
pigs. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/5474 |
| Date | January 2005 |
| Creators | Sewjee, Rowena. |
| Contributors | Gous, Rob Mervyn. |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
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