Abstract: Optimizing Feed for Immunocastrated Male Pigs

Type and Average of Pigs on the Farm

The farm maintains 1,100 sows, 38,500 weaners, and 28,000 grower-finishers at one site and 7,000 at another.

Farming System

Intensive production system.

Description and Evaluation of the Good Practice

In February 2025 this farm switched from surgically castrated to immunocastrated (IC) male pigs, driven by improved animal welfare and higher economic returns. Initially, no significant changes were made to the feeding strategies. As a result, IC males did not meet their nutritional requirements, leading to limited economic gains and an increased incidence of tail biting. Adding soybean meal on the floor significantly reduced unwanted behaviour and prompted a full revision of the feeding programme for pigs from 7–120 kg. At one site, the farmer differentiates diets for females and IC males during the growing-finishing phase using two compound feeds: Diet A (9.2 g digestible lysine per FU, 1.09 FU/kg) until one week after the second vaccination, followed by Diet B (7.1 g lysine per FU, 1.04 FU/kg). The feeding system mixes Diets A and B to produce the female ration (8.2 g digestible lysine per FU, 1.08 FU/kg from 30–120 kg).

Farm Context

• Pigs Final weight: 115–120 kg; slaughter age: 5–6 months.
• Housing and Management Characteristics Floor type: combination of drained and slatted flooring. The farm produces pigs for premium markets with specific constraints on feed ingredients, as animal products are forbidden.
• Management Practices

Two vaccinations: first at 35–40 kg, second around 85 kg; a third is provided for pigs that appear not to have responded. Ages at injection: 14 weeks and around 20 weeks. Safety vaccinator used; procedure carried out while pigs are calm. Boar taint: approximately 1.2%. Implemented by the farm owner in collaboration with a feed advisor.

Economic Analysis

Phase feeding IC males increased gross margin by +17 DKK per pig compared to feeding a constant diet throughout the growing-finishing phase. IC males have a lean meat percentage approximately 2% higher than surgically castrated pigs — on this farm, 59.61% for females versus 60.2% for IC males — yielding an additional 0.20 DKK per kg for each slaughtered IC male pig. Immunocastration costs approximately 25 DKK per pig covering both vaccinations and labour; one person can vaccinate 21 pigs in about 4 minutes.

Environmental Analysis

Optimised feeding reduces the environmental impact of production. Climate savings from IC males versus barrows are estimated at approximately 8.7 kg CO₂e per pig.

Replicable Benefits and Relevance for Other EU Countries

The performance response after the second immunocastration vaccination has been documented across multiple studies regardless of genetics, management system or feeding strategy, indicating that this practice is relevant for other EU countries and could support broader market adoption of immunocastrated male pigs.