ABSTRACT
Two experiments were conducted
at the piggery unit of the Department of Animal Science Farm, University of
Nigeria, Nsukka, from July 2007 to March 2009, to determine the effect of
nutrition and body condition at first mating on the reproductive performance of
gilts. The first experiment evaluated the effects of feeding different
combinations of protein and energy diets on age at onset of first observed
oestrus, growth rate, backfat reserve and body condition score of the gilts
from weaning to puberty. Fifty-four (54), eight week old weaner gilts were used
for this trial. They were randomly assigned to nine experimental treatment
diets having different combinations of protein (16%, 18% and 20% crude protein)
and energy (2800 kcal/kg, 3000kcal/kg and 3200kcal/kg) with six (6) gilts per
treatment. The gilts in each treatment were housed in pairs making up three (3)
replicates per treatment. Estrus detection was carried out twice daily at
0800hr and 1600hrs in the presence of mature boar beginning from the age of
five months. Blood samples were collected from two pigs per treatment by humane
puncture of the ear vein for haematological and biochemical analysis. In
addition, two (2) gilts from each treatment were randomly selected, slaughtered
and their reproductive organs excised and examined. Linear body measurements
(body length, chest girth, height at withers and flank-to-flank) were also
recorded. Data collected were analyzed according to factorial arrangement of
treatments in a completely randomized design (CRD) whereas stepwise multiple
linear regression analysis was used to generate prediction equations between
body weight and linear body measurements. In experiment 2, eighteen (18) gilts with
different body conditions and backfat thickness were selected and assigned to
experimental treatments with six gilts per treatment. All the gilts were
weighed and mated twice at the second observed estrus. Pregnancy was confirmed
by the gilt not returning to heat after 21 days of observation for signs of
heat after breeding. Gilts were fed 2.1 kg of an 18% CP diet daily throughout
gestation. Their feed was increased to 3.0 kg of feed daily during lactation
until weaning. Gilts were monitored and their reproductive indices recorded
throughout gestation and lactation. The pre-weaning performances of their
piglets were also recorded until weaning at day 35. Data collected were
subjected to one way analysis of variance (ANOVA) for a completely randomized
design (CRD). Results of the first experiment indicated that diet containing
3000kcal/kg or 3200kcal/kg metabolizable energy and 18% crude protein was the
optimum required for gilts to grow faster and reach the minimum threshold of
age, body weight, backfat reserve and body condition necessary for early
attainment of first oestrus and future reproductive processes. On the other
hand, the result also showed that when pork of a moderate fatness (lean pork)
is in demand, gilts should be fed diets having 2800kcal/kg of metabolisable
energy and either 16 or 18% crude protein. High coefficient of determination (R2)
values of 0.96, 0.95, 0.93 and 0.45, respectively, were recorded between body
(Y) weight and body length (BL), heart girth (HG), flank-to-flank (FF) and
height-at-withers (HW) measurements. Prediction equations for body weight of
the gilts were, Y = 0.83 x BL – 33.53, Y = 1.07 x HG – 37.86, Y = 1.22 x FF –
37.14 and Y = 0.86 x HW – 14.83. Results of the multiple linear regression
showed that with effective management, farmers, researchers and prospective pig
buyers can use the prediction equations for body length, heart girth and
flank-to-flank measurements to easily estimate the body weight of their pigs
especially, during selection, drug administration and/or determination of
market weight and prices. In the second experiment, results showed that body
condition of gilts at mating affected their gestation weight gain, lactation
body weight losses, litter size at birth and weaning, growth rate of their
piglets, pre-weaning mortality and weaning-to-estrus intervals, etc in favour
of gilts with normal and fat body conditions. It was concluded that in any
commercial pig industry where the management is interested in increasing sow
lifetime productivity, replacement gilts should be scored for body condition both
subjectively and objectively using ultrasonic equipment to determine their
readiness to undergo the stress of growth and reproduction. From an economic
point of view, this is an important factor that should be considered to
determine the total value of pigs produced within a given cycle. Hence, it is
recommended that breeding gilts should have at least between 15mm and 18mm
backfat thickness at first mating for effective and more balanced reproductive
processes.
CHAPTER ONE
1.1 Introduction
Recent
report (Spore, 2007) showed that pork is the world most widely consumed meat
making up about 40 per cent of the total meat consumed worldwide. The high pork
consumption has been attributed to the high cost of beef and the fear of avian
influenza for poultry (Spore, 2007). In Africa, however, it barely accounts for
10% of meat consumed. From 1990 to 2005, its production has risen from 500,000
to 800,600 tonnes, probably as a result of rapid urbanization which
interestingly has boosted production (Spore, 2007). In Nigeria, FAO (2005)
reported a 4 per cent increase in the annual growth rate for pig production
from 1990 to 2000 and this was adjudged to be the highest among other livestock
species.
These
reports are an indication that swine production has the potential for bridging
the protein deficiency gap in this country. This is because pigs are endowed
with natural genetic potentials that support rapid growth and high reproductive
performance. For instance, pigs have a rapid growth rate and demonstrate
excellent capacity for reproduction being litter-bearing in nature (Holness,
2005). They are characterized also by the best efficiency of nutrient
transformation into high quality animal protein (Spore, 2007). These attributes
have not been completely harnessed in this country thus leading to the slow
increase in the supply of pork.
The
performance of the breeding herd is fundamental to the financial success of any
pig enterprise. According to White (1996) and Whittemore (1998), pig production
is often assessed based on the number of litters produced per sow per year, the
number of piglets produced per litter, and the viability of those piglets.
Also, the lifetime productivity of the female within the herd is taken into
account. Thus, the young gilt represents the future of any pig enterprise and
if not fed properly, is unlikely to achieve her reproductive potential of
rearing 60 to 70 pigs over 6 to 7 parities (Scharlach, 1998). It is therefore
necessary to provide gilts with adequate nutrition in order to maximize litter
growth rate, and minimize empty sow-days thus increasing the size of subsequent
litters. Good nutritional preparation of the gilt from selection to first
farrowing is essential in achieving this goal. Soede et al.
(2007) reported that good nutritional management of gilts makes them to be
mature, well grown and in good body condition at service, resulting in better
conception rate and litter numbers. They emphasized that far too many gilts are
weaned in poor condition and do not conceive or have poor second litters
leading to an inexcusable waste of breeding potential.
The types of
feedstuff, environment, feeding system for pigs differ around the world, and
the nature of these differences is reflected in the growth and reproductive
efficiency of pigs around the world. Thus, there is variation within and
between temperate and tropical breeds of pigs in age of puberty, maturity,
gestation length, age and weight of pigs at weaning which are major
determinants of performance (Dritz, 2004; Pluske, 2006). As a result, most pigs
in the tropics hardly reach the live weight of those exposed to temperate
feeding system. Therefore, it is necessary to categorize pigs in the tropics
according to weight ranges obtainable in the zone.
Research
reports indicate that nutrition during the rearing of the gilt may influence
the length of her reproductive life (Scharlach, 2000; Close, 2003). Scharlach
(2000) reported that feeding programs for gilts should be aimed at the female
possessing targeted amounts of body fat, bone, and lean at critical points in
time such as selection, first breeding or conception, gestation, farrowing, and
at weaning. The author noted that maximum longevity is obtained by incorporating
the best combination of nutritional regimes during the periods preceding each
one of these events (Scharlach, 2000). Therefore, an accurate estimate of fat
reserve using both subjective and objective body condition score (BCS)
techniques several times during rearing provides targets at which nutritional
program can be aimed (Close, 2003).
In modern
pig production, nutrition and management play an important role in enhancing
reproductive performance of the sow. According to Close (2003), there is need
to ensure that the correct target body condition at first mating is achieved
and that nutritional needs are met during gestation and lactation. The overall
objective is to ensure that, as far as is possible, the sows achieve a good
level of performance on all farms.
Condition
scoring of pigs allows farmers to determine if their pigs are thriving in the
system of management they are kept. Condition scoring is necessary in every
type of pig production system as an important management practice. This also
applies to other farm animals like sheep, goat, and cattle (Cobb, 2005;
Singh-Knights and Knights, 2005; Taiwo et
al., 2005). Body condition scoring (BCS) is an estimate of the
muscle and fat development of an
animal. It can be assigned to an animal either by visual appraisal, by
palpation or by combining sight and touch. Animals are given a score from 1
(Emaciated) to 5 (Obese) based on the level of muscling and fat deposition
around the loin. It is expected that healthy, well nourished animals should not
be too fat or thin.
The body
condition of the gilt at first mating has a significant effect on sow lifetime
performance. Available records (Gueblez et al.,
1985; Gaughan et al., 1995; Challinor et al.,
1996) have suggested that animals that do not have sufficient body condition
when first....
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