Ongoing changes in agricultural policy and the liberalization in trade have increased the world market for pork, making it all the more vital for the U.S. to strive for efficient, low-cost production.

The U.S. now exports approximately 11% of its production. To remain competitive in this global market, efficient, low-cost suppliers must also ensure a high quality, safe product.

A recent survey by the Danish Bacon and Meat Council, citing 2002 data, showed the U.S. has relatively low cost of production, but is less competitive in sow reproductive efficiency (Figures 1, 2, 3). Consequently, U.S. producers market fewer pigs/sow/year than many other countries (Figure 4).

The cost-of-production advantage is likely due to lower feed, building and labor costs, lower interest rates, the economies of unit size, and the adoption of new technologies and management strategies.

The Danish report suggests that one factor contributing to U.S. producers' lower breeding herd efficiency is the widespread use of slaughter animals as breeding stock. This practice lowers the genetic merit of the sows in some herds.

Other factors include poor gilt pool management, larger unit size, earlier weaning, lower labor input/animal and low unemployment rates, which reduces the availability of skilled, knowledgeable employees. Also, high summer temperatures and diseases, such as porcine reproductive and respiratory syndrome (PRRS), certainly affect sow reproductive performance. But it is unlikely that these are more problematic in the U.S. than in other countries.

Parity Distribution Leaves a Mark

High sow wastage levels on many U.S. farms also contribute to poor breeding herd efficiency. Some important indicators of sow wastage are shown in Table 1. It is obvious that far too many sows are being culled in their early parities. The costs of high replacement rates can be very significant.

For an average herd with a 60% replacement rate that is producing 2.25 litters/sow/year, the percentage of gilt litters produced is 26.7 (60 % 2.25). Gilts produce smaller litters and have lower farrowing rates; therefore, more gilt litters produce fewer pigs born/sow/year (Table 2).

The effect of parity distribution on weaned pig cost is shown in Table 3. Weaned pig cost decreases as longevity in the herd increases. R. D. Boyd, with the Hanor Company, based in Spring Green, WI, has calculated that premature turnover of sows costs 25-30¢/weaned pig (US$) for each 1% change in sow turnover. The effects of culling rate on gilt replacement costs for a 1,000-sow herd paying $260/replacement gilt are shown in Table 4.

Obviously, production systems with lower sow replacement rates are more profitable than those with high sow replacement rates.

Major reasons for culling remain:

  • Reproductive problems (failure to show heat, repeat services, small litters);

  • Locomotor problems (osteochondrosis, foot lesions, injuries, conformation problems);

  • Degenerative problems (extremes of body condition (too fat, too lean), disease, abortion.

Although many factors contribute to high replacement rates, improper feeding programs for the gestating and lactating sow play an important role on many farms.

Feeding the Gestating Sow

Currently, most gestating sows are fed on the basis of condition score. However, condition scoring does not reflect the sow's backfat level. Also, because maintenance represents 75% to 80% of the total energy requirement of gestating sows, any feeding system that ignores sow weight cannot be accurate.

In a previous article, we presented a feeding system based on sow weight and backfat (see “Sow Backfat and Weight Watchers,” National Hog Farmer, Aug. 15, 2004, p. 18).

But most farms are not prepared or equipped to spend the time, effort or expense of weighing sows. Therefore, feeding tables based on visual estimates of sow weight or from regression equations using flank-to-flank measurements obtained by using a cloth tape (Figure 5) can be helpful.

The derived equation is: Sow weight, lb. = 26.85 × (flank measurement in inches) - 628.

Backfat is measured using an ultrasound backfat probe such as the Renco Lean Meater (Figure 6; Renco Corp., Minneapolis, MN).

Based on the estimates of sow weight and backfat level at the time of breeding, feeding allowances can be developed (Table 5).

These feeding allowances take into account the sow weight gain needed to attain a backfat level of 0.7-0.8 in. at farrowing. The maintenance requirement is calculated on the predicted mid-gestation sow weight; therefore, these feeding levels can be used from breeding to Day 100 of gestation. All sows should be fed an extra 2 lb./day from Day 100 to farrowing.

For those reluctant to weigh sows or to obtain flank-to-flank measurements, the sows should be assigned to weight classes as shown in Table 5, based on visual appraisal. Farms not using backfat measurement could replace the four backfat classes with condition scores of 1-2, 2-3, 3-4, >4. Thus, Table 5 could be used with visual estimates of sow weight and condition scores.

Adoption of a feeding system based on sow weight and backfat will result in:

  • Lower feed cost/sow/year;

  • A high proportion of sows farrowing with the targeted backfat level of 0.7-0.8 in.; and

  • Vitamin and trace mineral requirements of older, heavier sows being met.

Vitamins Are Vital

When sows are fed on the basis of condition score, all sows with the same score receive the same level of feed, regardless of their weight. As Boyd recently pointed out, when sows are fed only on the basis of condition score, the heavier, older sows do not receive sufficient vitamins and trace minerals to meet their requirements.

Research has shown that when older sows (Parities 6-11) were fed based on condition score, and body weight was not taken into account, pigs weaned/litter decreased in those parities (see “Control” line in Figure 7). However, when sows were given a constant amount of vitamins and trace minerals per unit of body weight, there was no decline in pigs weaned/litter with increasing parity number (see “Test” line in Figure 7).

Feeding sows according to the weight categories in Table 5 will allow equal intake of micronutrients per unit of body weight. Feed and calcium and phosphorus intakes of sows of three of those weight categories are presented in Table 6 using condition scoring (CS), or on the basis of backfat and an estimate of feed intake/day.

Data shown in Tables 6 and 7 confirm that feeding gestating sows on the basis of some estimate of weight will insure that the older, heavier sows in the herd will receive their required levels of trace minerals and vitamins, which may avoid the age-related decline in litter size.

Feed allowances for gestating sows should be based on sow weight and backfat level. Weight-based feed allowances will increase efficiency of feed usage, help reduce variation in sow condition at farrowing, and supply the correct amount of vitamins and trace minerals relative to body weight.

Frank Aherne, Alberta Pig Company, North Saanich, British Columbia, Canada; and Malachy Young, Gowans Feed Consulting, Wainwright, Alberta, Canada.

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