Nutrition: What effect does dietary fibre have on dry sow diets?

Friday, May 30, 2008

A multi-university experiment concludes that soybean hulls contributed to a reduced bodyweight at farrowing when compared with sows, while psyllium increased bodyweight through the reproductive cycle

by JANICE MURPHY

The profitability of the swine production chain hinges on reproductive efficiency in the sow operation. Discussion is continuing in the research community as to the role that fibre plays in gestation diets, since studies have shown that fibre can increase reproductive efficiency of sows in some instances, but not in others.

A recent review reported on the results of 20 publications where nonstarch polysaccharide (NSP) was added to gestation diets. They concluded that sows fed NSP during gestation gained less weight during gestation, lost less weight and consumed more feed during lactation, had more pigs born alive and weaned, and remained in the herd longer.

One challenge is the difficulty in achieving large numbers of sows and litters to assess properly the effect of dietary fibre on reproductive performance, a factor that contributes to considerable variability in existing research results. In contrast to these findings, other researchers have reported less than impressive results with fibre addition, resulting in little or no improvement in reproductive performance.

One trial did report improved reproductive performance in sows fed 0.3 per cent psyllium, a concentrated natural fibre laxative, for 14 days before farrowing and throughout lactation. This response suggests that concentrated fibre sources fed at low levels may be able to mimic the results seen in sows fed high-fibre diets.

The added benefit of a concentrated source of fibre is that it may eliminate one problem – energy dilution in sows fed high fibre diets. Another potential benefit from feeding high fibre diets to dry sows is the possibility of increased feed intake during the subsequent lactation.  

To address this issue, a regional experiment was conducted to determine the effects of added psyllium or soybean hulls to gestation diets on reproductive performance of sows and preweaning performance of their piglets. The co-operative study was conducted simultaneously at the Universities of Arkansas, Georgia and Tennessee. Overall, data were collected from a total of 194 sows and 381 litters (see Table 1).

Sows and gilts were allotted to treatments at breeding based on ancestry, parity, and weight. The three treatments were: 1) control corn-soybean meal diet; 2) control diet with 0.3 per cent psyllium, and 3) control diet with 20 per cent soybean hulls.

On day five postpartum, the sows were offered a lactation diet on an ad libitum basis. Data were collected from 130, 130 and 121 litters (from 64, 64, and 63 sows) for the control, psyllium and soybean hull treatments, respectively. Sow weights and feed consumption were recorded throughout the experiment, as well as the number and litter weight of piglets.

Fecal samples were collected on day 112 of gestation and day four postpartum for determining moisture percentage and to determine fecal scores on a scale from one to five (1 = dry and hard, 2 = firm, 3 = normal with no evidence of compaction, 4 = loose, and 5 = watery).

Dry sows fed psyllium were heavier on day 110 of gestation, farrowing, weaning and 17 days postpartum and achieved a greater average daily gain (ADG) during gestation compared with sows fed soybean hulls (see Table 2). Sows fed psyllium tended to have a larger bodyweight (BW) at day 110 of gestation and higher gestation ADG than control sows. Compared to the controls, sows fed soybean hulls tended to have a reduced farrowing BW.

Feed consumption data showed that sows fed psyllium had significantly reduced average daily feed intake compared with sows fed soybean hulls from day five to seven postpartum (5.20 versus 5.55 kilograms, respectively) but there were no other significant differences in feed intake throughout the duration of the study.

While not statistically significant, the researchers did note that sows fed soybean hulls showed an increase (0.22 kilograms per day) in feed intake from day four to 17 postpartum. They suggest that this increase is directly related to the bulkiness of soybean hulls as a feed ingredient. As previous studies have suggested, the increased amount of feed consumed in gestation by sows fed diets containing high fibre ingredients may increase the capacity of the sow's digestive tract, allowing for increased intake during lactation.

Fecal scores were higher and dry matter (DM) content decreased in feces of sows fed soybean hulls compared with sows on the psyllium or control diet. The general perception is that a moister or less firm stool would decrease the likelihood of constipation in sows during lactation and encourage them to eat more during this critical phase of production.

Sows fed psyllium tended to wean lighter pigs than sows fed the control diet. However, the lighter BW of weaned pigs can be attributed to these sows nursing slightly larger litters (see Table 3). Although the results showed an average increase of 0.42 pigs weaned, the response was not statistically significant.

The researchers determined that there was an interaction between treatment and farrowing number for total born pig birth weight and born alive pig birth weight. As a result, they re-analyzed the data from sows fed the treatment diets for two subsequent farrowings, separating it from sows fed the treatment diets for only one farrowing.

For total born pig birth weight (1.49, 1.57, and 1.45 kilograms for control, psyllium and soybean hulls, respectively) and born alive pig birth weight (1.51, 1.58, and 1.47 kgs for control, psyllium, and soybean hulls, respectively) sows fed psyllium had greater pig birth weights than sows fed soybean hulls. There were no other significant differences observed in sow reproductive performance.

Based on the results of this experiment, the researchers concluded that soybean hulls contributed to a reduced bodyweight at farrowing when compared with sows fed the control diets, while psyllium increased bodyweight through the reproductive cycle.

Although not statistically significant, sows fed soybean hulls tended to eat more during lactation, which agrees with much of the published literature on feeding high fibre diets to dry sows. It appears that more research is necessary in this area to assess concentrated sources of fibre and their potential benefits in comparison to high fibre feed ingredients for dry sows.BP

Source:  Darroch, C. S., Dove, C. R., Maxwell, C. V., Johnson, Z. B. and Southern, L. L. 2008. A regional evaluation of the effect of fibre type in gestation diets on sow reproductive performance. J. Anim. Sci. Published online March 14, 2008.

Janice Murphy is a former swine nutritionist with the Ontario agriculture ministry who now lives and works in Prince Edward Island.