Pig Farming: Feeding Replacement Gilts and Boars: Rations & Timing

Feeding Replacement Gilts and Boars: Rations, Timing, and Nutrient Needs

Feeding replacement gilts and boars is one of the most overlooked but economically decisive practices in pig production, especially in Africa and emerging livestock systems. While much attention is often placed on finishing pigs or lactating sows, the future productivity of a herd is determined long before first mating—during the replacement phase.

At FarmXpert Group, we work closely with farmers across Rwanda and beyond, and one lesson stands out: poorly fed replacements become costly breeders. They suffer from delayed puberty, poor fertility, leg problems, low libido, and early culling. In contrast, well-managed feeding programs produce resilient, fertile, and long-lasting breeding stock.

This comprehensive guide explains how, when, and what to feed replacement gilts and boars, combining global science (FAO, NRC) with local African realities.

Why Feeding Replacement Gilts and Boars Matters

Replacement gilts and boars are not just growing pigs—they are future breeding assets. Feeding mistakes at this stage can permanently damage:

    •Reproductive organ development

    •Skeletal strength and longevity

    •Libido and mating performance

    •Lifetime piglet output

According to FAO (2022), up to 40% of reproductive failure in pigs originates from poor early nutrition, not genetics.

Read more about Improving Pig Productivity in Smallholder Systems – FarmXpert Group

Key principle:

The goal is not fastest growth but balanced development.

Read more on the following links:

FAO. (2022). Pig sector development in emerging economies

NRC. (2012). Nutrient Requirements of Swine

Understanding Replacement Gilts and Boars

What Is a Replacement Gilt?

A replacement gilt is a young female pig selected to become a breeding sow, typically from 70 kg body weight until first mating (120–140 kg).

What Is a Replacement Boar?

A replacement boar is a young male pig raised for breeding, from weaning to sexual maturity (7–8 months).

Unlike fatteners, these animals must:

    •Grow steadily

    •Avoid excess fat

    •Develop strong bones and organs

    •Reach puberty at the right time

Source: Whittemore, C. (2015). The Science and Practice of Pig Production

Feeding Objectives for Replacement Stock

        For Gilts

        •Achieve puberty by 6–7 months

        •Reach 135–150 kg at first mating

        •Develop strong legs and uterus

        •Maintain moderate backfat (14–18 mm)

    For Boars

        •Promote testicular development

        •Maintain lean body condition

        •Avoid obesity that reduces libido

        •Support sperm quality

Source: FAO & ILRI (2021). Breeding pig management guidelines

Growth Phases and Feeding Strategies

    1. Grower Phase (30–60 kg)

    Objectives:

    •Frame development

    •Muscle growth

    •Bone mineralization

Recommended Nutrient Levels:

    •Crude Protein: 17–18%

    •Energy: 13–13.5 MJ ME/kg

    •Calcium: 0.7–0.8%

    •Phosphorus: 0.6–0.7%

Practical African Feed Options:

    •Maize or sorghum

    •Soybean meal or sunflower cake

    •Fish meal (where available)

    •Mineral premix

            Figure2: Growth curve of replacement pigs

2. Developer Phase (60–100 kg)

This is the most critical stage for reproductive development.

Feeding Focus:

    •Controlled energy

    •Adequate amino acids

    •Strong skeleton support

Recommended Nutrients:

    •Crude Protein: 15–16%

    •Energy: 12.5–13 MJ ME/kg

    •Lysine: 0.75–0.85%

    •Vitamin A, D, E supplementation

Avoid overfeeding energy—fat gilts have poor fertility.

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Livestock Feed Formulation Services – FarmXpert Group

    3. Pre-Breeding Phase (100 kg to mating)

    For Gilts:

    •Flushing feeding (10–14 days before mating)

    •Increase feed by 15–20%

    •Boost ovulation rate

    For Boars:

    •Maintain steady intake

    •Avoid sudden diet changes

    •Ensure zinc, selenium, vitamin E

                            Figure3: Boar and gilt feeding comparison chart

Feed Timing and Feeding Frequency

    Best Feeding Schedule

    •2–3 meals per day

    •Consistent timing

    •Fresh, clean water always available

 Why timing matters:

    •Stabilizes hormones

    •Improves feed efficiency

    •Reduces stress

In Rwanda and many African systems, once-daily feeding is common, but upgrading to twice-daily feeding can improve growth by 8–12%.

Key Nutrients and Their Roles

Protein and Amino Acids

    •Lysine: muscle & reproductive organ development

    •Methionine: fertility and immunity

    Energy

    •Too low → delayed puberty

    •Too high → fat deposition

Minerals

    •Calcium & phosphorus: bone strength

    •Zinc: sperm quality

    •Selenium: antioxidant protection

Vitamins

    •Vitamin A: reproductive tract health

    •Vitamin E: fertility & immunity

    •Vitamin D: bone development

Common Feeding Mistakes to Avoid

    ❌ Feeding finisher rations to replacements

    ❌ Overfeeding energy

    ❌ Ignoring mineral supplementation

    ❌ Sudden feed changes

    ❌ Poor water quality

According to FAO, these mistakes account for over 50% of early culling in breeding pigs.

Climate-Smart Feeding for Africa

In tropical climates:

    •Increase feeding during cool hours

    •Use fiber to reduce heat stress

    •Ensure electrolyte balance

FarmXpert Group promotes climate-resilient feeding systems adapted to African conditions.

 FAO Pig Production Manuals (FAO)

Economic Benefits of Proper Feeding

Indicator	Poor Feeding	Proper Feeding
Age at puberty	>8 months	6–7 months
Litter size	7–8 piglets	11–13 piglets
Sow lifespan	2 parities	5–7 parities

Better feeding = higher lifetime returns

    •European Pig Producers Association

Practical Example: Rwanda Smallholder System

    A FarmXpert-supported cooperative in Northern Rwanda:

    •Adjusted gilt protein from 14% → 16%

    •Introduced mineral premix

    •Improved feeding timing

Results after 12 months:

        •+22% litter size

        •−30% gilt mortality

        •+18% farm income

 Nutrient requirement chart

                   Table2:  Replacement pig nutrition guide

 Read more about Livestock Nutrition in Developing Countries

Pig Feeding schedule 

       Figure 4: Optimal feeding timing for breeding pigs

Conclusion: Invest Early, Harvest for Years

Feeding replacement gilts and boars is not an expense—it is a long-term investment. When nutrition is balanced, timely, and adapted to local conditions, farmers unlock higher fertility, stronger animals, and sustainable profits.

At FarmXpert Group, we believe that Africa’s livestock future depends on smarter feeding, not more feeding.

 Are you ready to improve your pig breeding performance?

    •Explore more expert livestock guides on www.farmxpertgroup.com

    •Share this article with fellow farmers

    •Leave a comment with your feeding challenges

    •Contact FarmXpert Group for custom feed formulation and advisory support.