INFLUENCE OF NUTRITION AND BODY CONDITION AT FIRST MATING ON THE REPRODUCTIVE PERFORMANCE OF GILTS IN THE HUMID TROPICS

ABSTRACT

Two experiments were conducted at the piggery unit of the Department of Animal ScienceFarm, University of Nigeria, Nsukka, from July 2007 to March 2009, to determine the effectof nutrition and body condition at first mating on the reproductive performance of gilts. Thefirst experiment evaluated the effects of feeding different combinations of protein and energydiets on age at onset of first observed oestrus, growth rate, backfat reserve and bodycondition 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 treatmentdiets 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 ineach treatment were housed in pairs making up three (3) replicates per treatment. Estrusdetection was carried out twice daily at 0800hr and 1600hrs in the presence of mature boarbeginning from the age of five months. Blood samples were collected from two pigs pertreatment by humane puncture of the ear vein for haematological and biochemical analysis. Inaddition, two (2) gilts from each treatment were randomly selected, slaughtered and theirreproductive organs excised and examined. Linear body measurements (body length, chestgirth, height at withers and flank-to-flank) were also recorded. Data collected were analyzedaccording to factorial arrangement of treatments in a completely randomized design (CRD)whereas stepwise multiple linear regression analysis was used to generate predictionequations between body weight and linear body measurements. In experiment 2, eighteen(18) gilts with different body conditions and backfat thickness were selected and assigned toexperimental 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 toheat after 21 days of observation for signs of heat after breeding. Gilts were fed 2.1 kg of an18% CP diet daily throughout gestation. Their feed was increased to 3.0 kg of feed dailyduring lactation until weaning. Gilts were monitored and their reproductive indices recordedthroughout gestation and lactation. The pre-weaning performances of their piglets were alsorecorded until weaning at day 35. Data collected were subjected to one way analysis ofvariance (ANOVA) for a completely randomized design (CRD). Results of the firstexperiment indicated that diet containing 3000kcal/kg or 3200kcal/kg metabolizable energyand 18% crude protein was the optimum required for gilts to grow faster and reach theminimum threshold of age, body weight, backfat reserve and body condition necessary forearly attainment of first oestrus and future reproductive processes. On the other hand, theresult also showed that when pork of a moderate fatness (lean pork) is in demand, gilts shouldbe 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, wererecorded 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 thegilts 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 effectivemanagement, farmers, researchers and prospective pig buyers can use the predictionequations for body length, heart girth and flank-to-flank measurements to easily estimate thebody weight of their pigs especially, during selection, drug administration and/ordetermination of market weight and prices. In the second experiment, results showed thatbody condition of gilts at mating affected their gestation weight gain, lactation body weightlosses, litter size at birth and weaning, growth rate of their piglets, pre-weaning mortality andweaning-to-estrus intervals, etc in favour of gilts with normal and fat body conditions. It wasconcluded that in any commercial pig industry where the management is interested in

increasing sow lifetime productivity, replacement gilts should be scored for body condition

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