While the traditional key performance indicator in sow units is weaned pigs per sow per year, the pork industry is now considering weaning weight with the same level of importance, says Dr. Juan Carlos Pinilla and his colleagues at pig breeding company PIC.  Speaking at the 2008 American Association of Swine Veterinarians, he notes that heavier weaning weights are positively correlated with growth rate, feed efficiency and pounds of saleable pork. Current estimates of milk yield are 22 to 26 lbs (10-12kg) of milk per sow per day, says Dr Pinilla.  Many factors influence this number: health, environment, genetic potential, mammary gland stimu­lation (lactation length, number and weight of the nursing piglets), nutrition, feed intake, body condition, and water intake.  His presentation described strate­gies to wean heavier piglets by maximizing milk pro­duction based on common practices utilized by some successful commercial systems in North America.

Maximizing milk production

Number of functional teats

To maximize litter weaning weight, it is necessary to select replacement gilts for number and quality of their teats.  “The standard is to cull gilts with less than 12 teats, but too many producers do not have this standard in their operations,” believes Dr Pinilla.  “Generally, modern dam lines have more than 12 teats, in fact, more than 85% of gilts selected in our Genetic Nucleus show 14 or more teats at selection.”  Recogniz­ing that the heritability of teat number is low and genetic improvement will take time genetic sup­pliers still have the responsibility to improve this trait, he feels.

Gilt growth rate and weight at breeding

In gilts, there is a significant correlation be­tween the ADG in the period from 65 to 195 lbs (30-88kg) and the weaning weight of their litters.  The current higher milk yield potential, and consequently the potential to wean heavier piglets, could be partially explained by larger body size and more mammary tis­sue in modern genotypes.

Beside the effects on retention rate and litter size, the current recommendation to breed gilts after they achieve 300 lbs (136kg) minimum to get farrowing weight to 400 lbs (181kg), will produce additional benefits.  “Gilts bred in that window will gain less body weight during their first gestation and consequently they lose less body weight during their first lactation and are able to retain weight, or even gain some weight, dur­ing P2 and P3, versus gilts bred at lighter weights,” explains Dr. Pinilla.  “As a practical consequence, weaning weights could be increased due to higher milk yields.”

Controlled weight gain in gestation

It is well documented that excess weight gain in gestation limits the feed intake during lactation and increases the sow’s body weight loss.  Farm management must be aware of that and manage gesta­tion feeding to limit excess body weight gain.  “During their first gestation the female should gain around 80 lbs (36kg) of body weight.  From P1 to P6, an average of 35 lbs (16kg) increase in body weight per gestation is acceptable,” believes Dr. Pinilla.   “A maximum of 12% of lost weight during the first lac­tation and a maximum of 8% average in older parity sows are considered as the limit body weight loss com­patible with high performance.”  

In a project to control annualized sow mortality, the impact of gestational body weight gain control was seen in terms of reduction in production cost per weaned piglet, with no negative effect on the litter weight gain in farrowing.  Annualized sow mortality effectively was reduced from 13% to 5%.  “A rule of thumb was derived from that experience: every lb of reduction in the daily usage of gestation diet from 7.0 lbs per day to 4.5 lbs per day can be translated into 1.0 to 1.1 lbs/day of additional feed intake in farrow­ing and every additional lb of average feed intake in farrowing in turn can be translated into 20-22 extra lbs of piglets weaned per sow per year,” explains Dr. Pinilla.

Number and weight of piglets nursed

Litter size (number and weight of the piglets nursed) is the major individual factor in the determination of milk production. “From a production management point of view, plan to have more than 50% of the sows wean­ing 11 or more piglets, particularly since milk yield is more than 50% greater when litter size increased from 6 to 12 piglets, advises Dr. Pinilla.  “The female is able to react to a higher milk requirement by eating more feed.  Suckled glands will be larger and more productive in subsequent lacta­tions than un-suckled or poorly suckled glands.”   Lower performance in farrowing can be traced to the practice of loading P1 females with just 9 to 10 piglets in order to “prevent extensive catabolism”.   The current recommenda­tion is to load gilts with 12 strong and heavy piglets and support that with proper feeding management, cooler rooms, limited cross fostering, and water availability, he notes.

The most recent and promising tool to produce heavier litters is to let the sows farrow naturally and/or limit the use of farrowing induction to risky sows (fat, lame or older than P5).  Data collected from a commercial farm suggests that every additional day of gestation results in piglets weighing 0.15 extra lbs (70g) per day, in the range from 113 to 118 days. Consequently those heavier piglets at birth have greater opportunity to vigorously suckle the teats, survive and gain weight and be weaned at a heavier weight.

Dr Pinilla also advises drying off piglets after birth to prevent chilling, measures to control the incidence of diarrhoea and split suckling, especially where litter size is high.  “Farms where split-suckling has been fully implemented have seen increased survivability and weaning weight, and less variation in weaning weights,” he says.

Lactation length

It is well-known that increasing lacta­tion length increases weaning weight.   “PIC research has shown that for every addi­tional day in farrowing with their mother, weaning weight increases an average of 0.56 lbs/day/piglet (250g), which is in turn related to a reduction in the age to market, Dr. Pinilla explains.  He recommends a minimum of 20 days at weaning, recognizing that this may require additional farrowing places to be constructed in some cases.  “A reduction in the breeding target, and consequently the average sow inventory, is not as cost effective as adding more farrowing spaces,” he stresses.

Maximize lactation feed intake

It is critical to prevent and/or to control situations lead­ing to off-feed sows, stresses Dr. Pinilla.  “Proper hygiene measures associ­ated around farrowing, such as room sanitation, a clean sleeving process, and individual treatment of fever and lameness are a must.  Also, check the availability of fresh, cool and clean water is a daily duty in farrowing, mak­ing sure the sows have a minimum water flow rate of 0.5 gal (2 litres) per minute.”

Data from a commercial system suggests that a mild restriction for 3 days followed by full feed­ing from day 4 through the end of lactation results in increased feed intake and reduced body weight loss, Dr Pinilla explains.  “Based on these data, the recommendation for feeding PIC sows is to scale feed at 4.0, 4.0, and 6.0 lbs per day for days 0, 1, and 2 of lactation followed by ad-libitum access to feed.  This pattern ensures the maximum aver­age daily feed intake, milk yield, litter weight gain, and minimum body weight loss.”

Alternatives to the traditional hand feeding systems include the use of self feeders, which are able increase the average daily feed intake by about 7% compared with hand feeding systems and are less de­manding in labour.  However, no feeding protocol or feeder design will work unless qualified staff gets the sows up two or three times a day to stimulate them to eat, believes Dr. Pinilla.  “Other key duties are clean­ing the feeders to prevent mould, adjusting the heat lamps height or simply turning them off when needed and checking room ventilation and temperature,” he says. “Caretakers must be able to ‘read’ the sow and piglet behaviour and make adjustments to ensure the sows eating enough feed to wean healthy and heavy piglets.”

Cross fostering

Cross-fostering is a common and preferred manage­ment tool.  While it provides opportunities to the smaller piglets in a room to get enough milk to grow, in too many situations the staff tends to use the fostering too much and/or too often, Dr Pinilla believes.  “Create the light litters as soon as possible after all pigs have received colostrum and before the social order is established, sometime during the first 12-16 hours of life,”, he advises.  “When the equalization by size is made after day 1, the benefits are limited because it is a disruption of the normal process of nursing, sows get nervous and mastitis can become a problem.”  Nurse sows to raise the fall-behinds can be created from day 4 to 7, moving a fresh sow from the next younger room, he says.  “It is important to limit the fostering to a maximum of 10-15% of the litters disrupted after day 4-7 of age.”