Boost your gilt development program

The application of strong management strategies beginning at farrowing can help build a solid foundation for your herd.

by Kate Ayers

As stakeholders throughout the swine industry continue their quest to optimize production and balance sheets, farmers should closely examine their gilt development programs.

“The time from entry at selection to first breeding as a gilt is when a sow accumulates the most non-productive days,” says Dr. Clay Lents. He’s a research physiologist with the U.S. Department of Agriculture’s Meat Animal Research Center in Clay Center, Nebraska.

Proper gilt management helps to ensure this segment of the herd does not negatively affect an operation’s bottom line.

A “gilt needs to reach 2.5 parities before she becomes profitable, meaning that she has produced enough pigs to pay for the cost of her development,” Lents says.

Given the costs and labour involved, producers need strong gilt development programs to help generate productive and profitable herds.

Overall, a good program includes “a series of small advantages at each step of the way that accumulate over time.” Unfortunately, however, these incremental gains “don’t show up until the second or third parity. That aspect makes it really hard to identify phenotypic traits that can predict lifetime productivity,” Lents explains.

“A solid gilt management program ultimately must deliver the right amount of gilts at the right time, at a reasonable cost with high probability of having” large first and subsequent litters, adds Dr. Juan Carlos Pinilla. He’s a director of global technical services for applied reproduction at PIC headquartered in Tennessee.

PIC focuses on genetic improvement, secure delivery of genetics to producers, and on-farm technical services to help farmers optimize production.

Each farmer needs a tailored approach to gilt management that can help him or her achieve breeding targets and production goals.

piglets nursing
    National Pork Board, Des Moines, Iowa photo

Better Pork speaks with a nutritionist, a swine production specialist and other industry experts to learn how producers can structure sound gilt development programs. We also review the logistics of boar exposure and other management decisions farmers should consider to ensure they bring the best replacement gilts into their herds.

Herd efficiency

“Gilts are the foundation of the herd,” Dan Bussières said at the Banff Pork seminar earlier this year. He’s a swine nutritionist and co-owner of Groupe Cérès Inc. in Lévis, Que.

“Good management in gilts’ first cycles is key to optimize herd lifetime performance.”

Groupe Cérès supports Canadian pork producers in such areas as genetics, nutrition and research, the company’s website says.

Gilts account for a notable portion of a breeding herd.

“Gilt litters amount to about 25 per cent of the total litters born each week, so their performance can definitely impact a farm’s performance and financial results,” says Pinilla.

Producers must select the right gilts for their herds or they will experience high sow turnover and increased culling rates.

“We have to ensure we have good-quality gilts available all the time to replace old and unproductive animals,” Dennis Robles adds. He’s the production specialist for Swine Health Professionals Ltd. in Steinbach, Man.

Swine Health Professionals Ltd. helps farmers develop herd health plans, monitor production progress, and maintain biosecurity targets, the company’s website says.

“Typical culling rates are around 50 per cent,” Lents says.

“Higher rates mean that producers have to retain more gilts to meet those replacement needs.” In such cases, farmers need larger gilt development units (GDUs), more boars for gilt stimulation and more personnel to manage those animals. As efficiency decreases, costs add up quickly.

Guide to gilt management

Effective gilt management begins at birth, many experts agree.

“Litter of origin, lactation management and the application of early selection strategies are (initial) indicators of future performance and efficiency,” say Jennifer Patterson and Dr. George Foxcroft in a July 2019 article called “Gilt Management for Fertility and Longevity.”

Patterson is a research associate in the faculty of agricultural, life and environmental sciences at the University of Alberta. Foxcroft is a professor emeritus in the university’s department of agricultural food and nutritional science.

Individual birth weight, litter birth weight and the sex ratio of the birth litter also help predict gilt performance, studies show. Extremes in birth weight – either too low or too high – can negatively affect the reproductive potential of replacement females, Patterson and Foxcroft say.

Ideally, gilts should weigh about 1.7 kilograms (3.7 pounds) at birth, Lents says. And producers should not select pigs under 1.1 kgs (2.4 lbs.) at birth for replacement gilts, Bussières suggests.

Also, gilts must receive “adequate levels of colostrum to support development of the reproductive tract,” Lents adds.

“The reproductive development of gilts that don’t get enough colostrum in that first day of life is delayed. They can still get into the herd, but they produce fewer piglets.”

Pre-weaning growth rate serves as another indicator of lifetime reproductive potential, Lents says.

piglets nursing
    National Pork Board and the Pork Checkoff, Des Moines, Iowa photo

Gilts should gain a minimum of between 0.6 and 0.7 kgs (1.3 to 1.5 lbs.) in weight per day from birth to selection for breeding. “Below that range, the risk is higher for reproductive impairments,” he says.

And the size of the litter that replacement gilts grow up in can affect future performance.

Reducing “litter size from 12 to six pigs has shown to improve gilt performance,” Bussières says. In total, 40 per cent of gilts from smaller litters reach parity six. In contrast, due to pre-weaning competition, only 20 per cent of gilts from larger litters reach this stage, he adds.

“Although we know (the pursuit of a smaller litter size) is not a practice that we would apply commercially, such data support the fact that optimizing performance of future replacement females during their (suckling) period will improve lifetime performance and longevity,” Bussières says.

Young Pigs
    National Pork Board and the Pork Checkoff, Des Moines, Iowa photo

Producers can house gilts during the nursery phase at the same density as commercial pigs. This density is about 0.28 square metres (three square feet) per pig if the producer is raising the animals to 30 kgs (66 lbs.) in the nursery barn, he says.

Overcrowding “can lead to issues with tail and ear biting,” he says.

“Generally, when gilts reach about 30 kgs (66 lbs.), producers transfer these animals into the grow-finish section or a GDU,” Bussières says.

In this section, gilts should have at least 0.74 sq. m (eight sq. ft.) of space until the animals weigh between 100 and 120 kgs (220 and 264 lbs.). Floor quality is very important during this period to help ensure proper leg development and soundness.

Once gilts reach the desired weight, producers either move them into an acclimation barn or the main sow herd, Bussières says.

At this stage, gilts need more space – between 1.11 to 1.3 sq. m (12 to 14 sq. ft.) per animal, he says.

In the breeding animal selection process, farmers should consider such phenotypic traits as the number of functional teats. At maturity, gilts should have a minimum of 14 teats. Gilts should have sound conformation with good anterior and posterior leg quality, and good back lines. The animals should also have well-developed vulvas, Bussières says.

While physical traits are important, internal reproductive characteristics may be even more critical for productivity, Robles says.

“Hormonal development and the environment she was raised in are some key factors in gilt development,” he says.

Pen and stall design and “where the boars are placed in the barn have huge influences on hormonal development,” Robles says.

“Positive human interaction and handling are also very important factors to make sure the animals stay in the herd longer.”

Breeding success

“Early puberty is important for sow lifetime productivity,” Lents says.

Several factors – including housing, climatic environment, season, feeding systems and health status – can affect gilts’ pubertal onset, say Patterson and Foxcroft. For example, puberty may be delayed if animals are in poor body condition.

“A failure to select gilts with the greatest reproductive potential, and inappropriate management of their physiological state and metabolic condition at service, are key risk factors for poor sow lifetime productivity,” they add.

Robles agrees.

Post-weaning, the period between first heat and service is important to ensure gilts develop and cycle properly, he says.

By exposing gilts between 160 and 170 days of age to boars, farmers can select and move the appropriate animals into the next production phase, Bussières says.

Exposing females to high-libido boars can “trigger the onset of puberty” in gilts, Pinilla says.

“If properly done, boar exposure can also synchronize the ovarian activity in a homogenous group of gilts.”

Ideally, gilts should have between 15 and 20 minutes of boar exposure each day, Lents says. But it is “hard for farmers to dedicate that much time, which limits the effectiveness of boar exposure and reduces the number of cycling gilts,” he says.

“Exposing boars along a fence line works but exposing gilts to vasectomized boars in the pen is the most effective way to stimulate puberty in gilts.”

Producers should introduce a boar to a pen with a maximum of 17 gilts to avoid overworking the male, Lents says.

Farmers should also “rotate boars so gilts are exposed to different boars on consecutive days” and the boars can rest, he says.

Farmers should select gilts that had their first heat before 210 days of age, Bussières says.

farm of Leon Sheets, barn at sunset
    National Pork Board and the Pork Checkoff, Des Moines, Iowa photo

Following their first estrus but before their introduction to the breeding herd, gilts should be acclimatized for at least 14 days, Lents says. Gilts that are not properly acclimatized could lose back fat. Declines in body condition before breeding are not ideal, he says.

Acclimatization can also help gilts build immunity.

Farmers can integrate a cull sow with the gilts, so “they can be exposed to diseases before entering the sow barn,” says Robles.

Producers should consider time of breeding as well, as this decision can significantly influence lifetime productivity.

Typically, farmers should not breed gilts based on chronological age “because pubertal age can range pretty widely. Instead, we ought to breed based on body weight,” Lents says. The optimal weight range to breed gilts is between 135 and 160 kgs (297 and 352 lbs.).

“Gilts should be eligible for breeding at their second or third estrus,” he says. At this stage, “they should have enough body size to sustain reproductive performance and have adequate litter sizes at farrowing.”

Indeed, “first- and second-parity litter sizes (are) predictive of later lifetime performance and the appropriate management of a gilt at first service is, therefore, important to improve first-parity litter size and these lasting effects on lifetime production,” Patterson and Foxcroft say.

“The cumulative effective of poor management of the gilt prior to service limits the ability of the sow to produce pigs in subsequent parities.”


A well-balanced ration and adequate energy intake throughout the gilt development phase are important to maximize gilts’ reproductive potential, Patterson and Foxcroft say.

Poor nutrient availability “limits growth rate and, if restriction is severe, ovarian development could be limited as well. Both situations could damage or hinder reproductive results and longevity,” Pinilla adds.

Ad libitum feeding is a good option for developing gilts.

“The objective during the period when gilts are between 25 and 30 kgs (55 and 66 lbs.) and 100 and 120 kgs (220 and 264 lbs.) is to ensure proper growth and structural development, while trying not to achieve very high average daily gain,” Bussières says.

“Feeding lower-energy diets and dry feed are ways to help control growth. Restricted feeding isn’t a preferred way to limit growth, especially after gilts reach 50 kgs (110 lbs.). This approach can compromise mammary gland development.”

Farmers should also ensure rations contain sufficient vitamins and minerals for developing gilts.

Gilt feed should have between 0.1 and 0.2 per cent higher calcium amounts and 0.1 per cent higher digestible phosphorus compared to standard finisher diets, Bussières says.

“Also, we would normally recommend using a gilt VTM (vitamin and trace mineral) or a sow VTM in gilt-developer diets,” Bussières says.

The inclusion of organic trace minerals, including copper, zinc and manganese, could support good leg and hoof quality, he adds.

Once gilts reach their breeding weights, “a late-gilt-developer diet could be used or we would normally use what we call a gilt-maturation diet,” Bussières says.

“This diet is lower in protein and amino acids, but higher in energy to promote fat deposition before breeding.”

Ad libitum feeding during the first wean to estrus period could boost weaned gilts’ performance.

“Data from a large trial done at HyLife shows a significant improvement in performance when weaned gilts were fed between 0.68 and 0.91 kgs (1.5 and 2.0 lbs.) of feed during the wean-to-service interval,” Bussières says.

The “number of days before breeding improved by 3.5 to four days, conception rates increased by 13 per cent and the next litter had an average of an extra 0.6 pig per litter.”

Given the complexity of factors involved in ensuring a strong gilt development program, set your operation up for success through careful staff oversight of the herd and timely consultations with your vet and swine nutritionist. BP

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