J. Anim. Sci. 2005. 83:255-261
© 2005 American Society of Animal Science
Effect of sow parity and weight at service on target maternal weight and energy for gain in gestation1
M. G. Young*,2,
M. D. Tokach*,
F. X. Aherne
,
R. G. Main
,
S. S. Dritz,
R. D. Goodband*,3 and
J. L. Nelssen*
* Department of Animal Sciences and Industry;
and
Alberta Pig Co., British Columbia, Canada V8L 1N2; and
and
Food Animal Health and Management Center, College of Veterinary Medicine, Kansas State University, Manhattan 66506-0201
 |
Abstract
|
|---|
The objective of this study was to evaluate targeted maternal weight gains in sows by parity group during gestation. Weight and backfat gains during gestation by parity, weight, and backfat groups also were analyzed. The data evaluated were a subset (374 sows) of a larger experiment that compared three methods of feeding sows during gestation on weight and backfat gains and subsequent reproductive performance. Feed allowances were based on modeled calculations of energy and nutrient requirements to achieve target sow maternal weight and backfat gains. Actual backfat gain for gilts and sows was regressed on maternal weight gain and estimated energy available for gain. The regression equations were then used to predict maternal weight gains for target backfat gains for three parity groups (gilts, Parity 1 and 2 sows, and Parity 3 and older sows). For gilts and Parity 1 and 2 sows, much greater target maternal weight gains are required to achieve 6 and 9 mm of backfat gain, whereas Parity 3 and older sows require maternal weight gains similar to those targeted to achieve the desired backfat gain. Given similar energy intake levels above maintenance, gilts gained more weight than multiparous sows, as gain was based more on protein and less on fat and thus was more efficient. Gilts required more maternal weight gain than sows to achieve similar backfat gains due to the higher protein and low fat contents of gain in younger, lighter sows compared with older parity sows. Low-backfat sows that needed to gain large amounts of backfat failed to achieve these large gains. We speculate this failure may be due to lower tissue insulation levels with the low backfat levels and higher activity levels of these sows compared with high-backfat sows. It seems that both parity and weight are individually important factors that influence energy and nutrient requirements for gestation in the modern sow.
Key Words: Backfat • Energy • Gestation • Parity • Sows
|
Introduction
|
|---|
The dietary energy requirements of the gestating sow will vary with BW, target BW gain during gestation, and other management and environmental conditions. Aherne and Kirkwood (1985)
and Williams et al. (1985) suggested that sows should be fed and managed so that they gain 25 kg of maternal BW throughout gestation for at least the first three or four parities. The weight of the placenta and other products of conception should be approximately 20 kg, for a total of 45 kg of gestational weight gain by the sow (Verstegen et al., 1987; Noblet et al. 1990). Maternal weight gain represents 15 to 20% of gestating sow’s energy requirement (Aherne et al., 1999).
Models have been developed for sow nutrient requirements in gestation (Noblet and Etienne, 1987; Dourmad et al., 1998; NRC, 1998). These models attempt to partition nutrient requirements into three components: maintenance, products of conception, and maternal weight gain. In a companion paper (Young et al., 2004a), it was concluded that feeding sows in gestation based on modeled calculations of energy and nutrient requirements to achieve target sow maternal weight and backfat gain was a viable alternative to the common method of feeding sows in gestation based on BCS. However, Young et al. (2004a) observed that sows did not necessarily achieve the desired backfat gains with full precision. This was especially true for thin sows that needed to gain 6 to 9 mm of backfat to reach the targeted 19-mm goal. The objectives of the present study were to determine target maternal weight gains required to achieve target backfat gains by parity group. In addition, weight and backfat gains in gestation were analyzed by parity, initial weight, and backfat groups at service.
|
Materials and Methods
|
|---|
Data
The data analyzed in this study were a subset (374 sows) of a larger dataset (559 sows) from an experiment by Young et al. (2004a) that compared three methods of feeding sows over one gestation and the subsequent effects on lactation performance. In that study, there were three treatments and control gilts and sows were fed according to BCS based on a scale of 1 to 5 (1 = thin; 5 = fat). Treatments two and three used feeding levels based on backfat thickness (measured between d 0 and 5 after breeding) and weight at weaning for sows or weight at service for gilts to achieve target weight and backfat gains. Only data from sows fed based on backfat and BW were used for this analysis. Control gilts and sows were not included in the analysis as feeding levels were arbitrarily set based on BCS and not based on backfat and/or weight gain in gestation.
Measurements, Feeding Levels, and Housing
Backfat was measured at the P2 position (last rib, 65 mm from the center line of the back) on both sides of the backbone using a Lean-Meater (Renco Corp., Minneapolis, MN). Values from the two measurements were averaged to obtain a single backfat measurement. Backfat thickness was measured between d 0 and 5 after breeding, and sows were weighed at weaning and gilts were weighed at service. Feed allowance was calculated to achieve a target backfat of 19 mm and a range of 19 to 21 mm at farrowing. The target of 19 mm of backfat at farrowing was selected so that sows could lose 3 to 4 mm of backfat during lactation and not fall below 13 mm of backfat at their subsequent service. Data from several studies have shown that low backfat levels at weaning (14 mm) compromise subsequent reproductive performance (Young et al., 1991; Hughes, 1993; Tantasuparuk et al., 2001). Previous research has illustrated a negative relationship between high backfat at farrowing and lactation feed intake (Mullan and Williams, 1989; Dourmand, 1991; Revell et al., 1998). In addition, Yang et al. (1989) observed that sows with backfat thickness of 20 mm at farrowing reared piglets that had higher growth rates than did sows with a backfat thickness of 12 mm when given restricted feed in lactation.
For feeding based on backfat and weight, target maternal weight gains were set at 12.7, 20.0, 27.5, and 35.0 kg for 0, 3, 6, and 9 mm of backfat gain, per Aherne (1999). Feeding levels were determined using the equations of Noblet and Etienne (1987; NEm, MJ = 0.45 x BW0.75, kg); Dourmad et al. (1996, 1997, 1998; energy for maternal gain, MJ = [9.7 x BW gain, kg ( 54 x P2 gain, mm]/0.75); and Noblet et al. (1985; energy uterus gain, MJ = [4.8 x fetus BW gain, kg]/0.5). For these equations, BW represents the average BW of the sow, which was calculated as weight at service plus half the targeted maternal weight gain plus half the products of conceptus and uterine gain in gestation. Backfat gain was the targeted increase in required backfat to achieve a target backfat of 19 mm with a range of 17 to 21 mm at farrowing.
Sows and gilts were weighed again between d 112 and 114 of gestation when they entered the farrowing barn. Backfat measurements were also taken between d 108 and 113 of gestation. Protein and fat mass were estimated using the prediction equations of Dourmad et al. (1997), Everts and Dekker (1995), and Whittemore and Yang (1989). Estimated protein mass at weaning and farrowing using the three equations was very similar, whereas estimated fat mass was numerically higher using the equations of Whittemore and Yang (1989) compared with those of Dourmad et al. (1997) and Everts and Dekker (1995). Nonetheless, the differences among treatments were similar regardless of which prediction equations were used. Energy in weight gain was determined using actual weights and by estimating protein and fat composition of gain, summing estimated protein gain multiplied by 10.6 (ME required for protein synthesis, Mcal/kg; Tess et al., 1984), and estimated fat gain multiplied by 12.5 (ME required for fat synthesis, Mcal/kg; Tess et al., 1984). Maintenance energy requirement as a percentage of ME intake was determined by dividing NEm (MJ = 0.45 x BW0.75, kg; Noblet and Etienne, 1987) by total ME intake. The estimated energy available for gain was determined as the total energy intake less energy required for maintenance and energy in products of conception.
The experiment was conducted from January to July 2002. Gestation barn temperatures averaged 19.8°C for the duration of the trial, with an average of 18.6°C from January to March and 20.9°C from April to June. For the first 35 d of gestation, all sows were housed in the in individual gestation sow stalls (0.61 m x 2.14 m). After pregnancy confirmation, they were moved to a second barn where they were housed in similar individual gestation sow stalls for the remainder of gestation. Both the barns were naturally ventilated and double-curtain sided with fully slatted flooring. In gestation, sows were individually fed from gestation feed boxes (Chore-Time Equipment, Mildford, IN) into an open concrete trough directly in front of the sows. Sows were fed once daily at 0700 with their individually daily feed allowance. For more details on experimental procedures see Young et al. (2004a).
Statistical Analyses
Data were analyzed as a randomized block design using the Mixed procedure of SAS (SAS Inst., Inc., Cary, NC). Sow was the experimental unit of analysis. Parity group (n = 6), backfat group at service (n = 4), and initial weight group (n = 5) were the main effects tested. Using the Proc Reg procedure of SAS, actual backfat gain by the target backfat gain group (0, 3, 6, and 9 mm) was regressed on maternal weight gain. The regression equations were then used to predict maternal weight gain required for 0, 3, 6, and 9 mm of backfat gain for the three parity groups (gilts, Parity 1 and 2 sows, and Parity 3 and older sows). Least squares means, protected by significant F-tests, were compared using least significant difference tests. We considered P < 0.05 significant and P > 0.05 to P < 0.10 to be a trend.
|
Results and Discussion
|
|---|
New Target Maternal Weight Gains
Using the data from the current experiment, maternal weight gains to achieve 0, 3, 6, and 9 mm of backfat gain were determined for gilts, Parity 1 and 2 sows, and Parity 3 and older sows (Table 1). The new proposed target maternal weight gains for the zero backfat gain category are lower for all parity groups than those proposed by Aherne (1999), with the exception of gilts. For the 3- and 6-mm backfat gain categories, the new proposed maternal weight gains for gilts and Parity 1 and 2 sows are greater, whereas for Parity 3 and older sows were lower than the targets proposed by Aherne (1999). For the 9-mm backfat gain category, the new proposed target maternal weight gains for Parity 1 and 2 sows are much greater than those proposed by Aherne (1999), but similar for Parity 3 and older sows.
For the 6- and 9-mm backfat gain categories, the new proposed maternal weight gains for gilts and Parity 1 and 2 sows are greater than those used in our earlier experiment (Young et al., 2004a). One possible reason for the increased energy requirements was that sows with very little backfat have less insulation and tend to lose more energy in the form of heat than do sows with greater backfat thickness. Tissue insulation of thin sows was approximately 28% less than that of standard sows (deh Hovell et al., 1977). In addition, thin sows tend to be more active (stand up more often), thereby expending more energy. In a study by Bergeron and Gonyou (1997), sows that were classified as more active (Category 1) at the beginning of the experiment gained less (P < 0.05) weight (32.0 ± 7.75 kg) during gestation than less active sows (45.7 ± 8.15, 41.4 ± 11.18, and 45.7 ± 7.98 kg for Categories 2, 3, and 4, respectively). Similarly, Cronin (1985) reported that sows with high activity levels produce more heat and consequently retain less energy than sows with lower activity levels in gestation. The mean cost of standing activity determined by Noblet et al. (1993) is 0.07 kcal/(kg BW0.75 • min standing). For 200-kg sows standing for 100 or 200 min/d, the energy requirements increase from 0.5 to 1.0 Mcal/d, respectively, which is equivalent to 9 and 17.8% of maintenance energy requirements. Sows with low backfat tend to deposit less energy as fat and have lower fat depots. Thin sows can also be timid eaters, and more aggressive sows may steal feed from these sows. Thus, the actual energy intake of thin sows may be lower than targeted, contributing to the lower weight and backfat gains in gestation. Energy requirements above maintenance for weight and backfat gains for Parity 3 and older sows are much greater than those required by younger-parity sows (Dourmad et al., 1998). This is explained by the difference in composition of gain, with protein gain constituting a larger proportion of weight gain in younger sows compared with fat gain in older sows, which has a lower energetic deposition cost compared with fat gain (10.6 vs. 12.5 Mcal/kg; Tess et al., 1984). For a given energy supply, higher protein retention was measured in gilts than in multiparous sows (Dourmad et al., 1998). For primiparous sows gaining 30 kg BW throughout gestation, the composition of the BW (carcass) gain is approximately 75% lean and 25% fat (Shields et al., 1985; Whittemore and Yang 1989; Pettigrew and Yang 1997).
Parity Group
For gilts and Parity 1 and 2 sows, estimated maternal weight gains were greater, whereas for Parity 3, 4, 5, and older sows, weight gains were lower than predicted. The deviation between predicted (NRC, 1998) and estimated maternal weight gain in gestation decreased with increasing parity number up to Parity 3 and increasing BW range from 215 to 250 kg (Table 2). Similar to the results found by Cooper et al. (2001), the NRC (1998)-predicted maternal weight gains underestimated maternal gain in gestation for younger, lighter sows and overestimated maternal gain for older, heavier sows. There are a number of possible explanations for the difference in actual and predicted maternal weight gain. The first and most obvious reason was the difference in the composition (lean and fat) of gain between younger and older sows. Estimated protein mass gain decreased from 15.6 to 8.2% of estimated maternal gain, whereas estimated fat mass gain increased from 30 to 56.2% of estimated maternal gain as parity increased from gilts to Parity 5 and older sows. The NRC (1998) model underestimates maternal weight gain in smaller, younger sows because gain was based more on protein and less on fat, and was thus more efficient than predicted by the NRC (1998) model. Overestimation of maternal weight gain in older, larger sows may be explained by the less efficient use of gain, suggesting a higher than predicted (NRC, 1998) proportion of fat gain. There may also be genetic factors that might affect the composition of gain (Sauber et al., 1998). Because the model does not adjust for the proportion of protein and fat accretion based on genetics, age, and size of the sow, this may account for the deviation between the estimated and predicted maternal weight gain in gestation.
For all parity groups, actual backfat gains were lower than predicted. The estimated maintenance energy requirement as a percentage of total energy intake was greater (P < 0.05) and energy available for gain was lower (P < 0.05) for Parity 5 and older sows than for younger sows. Estimated maintenance energy requirement as a percentage of total energy intake was greater (P < 0.05) for gilts compared with Parity 1 sows, which was unexpected. Estimated energy in gain was much greater than the estimated energy available for gain in gilts. A possible explanation may be that maintenance energy requirements are lower for gilts than multiparous sows; thus, the current estimate may be overestimating maintenance and underestimating energy available for gain. Beyer et al. (1994) reported that energy requirements for maintenance increase from 389 kJ in the first parity to 435 kJ in second parity and to 473 kJ of ME/kg of BW0.75 in the fourth parity. The estimated energy in gain was determined using energy cost of protein and fat deposition of 10.6 and 12.5 Mcal ME/kg (Tess et al., 1984); these values were determined with growing pigs, but these may be different for sows contributing to the difference in estimated energy in gain vs. energy available for gain.
Backfat Group at Service
Sows were categorized into four backfat groups at the time of service: <12, 12 to 14.9, 15 to 17.9, and >18 mm. Estimated maternal weight gain was lower (P < 0.05) for sows in the high backfat group (>18 mm) at service compared with sows in the three lower backfat groups (Table 3). Although sows in the low backfat group (<12 mm) at service received more (P < 0.05) feed throughout gestation than the sows in the 12 to 14.9 and 15 to 17.9 mm groups, they failed to gain significantly more weight. As daily feed intake increased, backfat gain increased (P < 0.05), but sows predicted to gain large amounts of backfat (8.2 and 5.7 mm) failed to achieve predicted gains. Higher activity levels and greater energy loss in the form of heat due to lower insulation was a likely cause of these sows failing to achieve the predicted backfat gains. Young et al. (2004b) reported a large range in standing duration for gestating sows ranging from less than 150 to greater than 500 min/d, which resulted in activity heat production varying from 60 to 200 kJ/(kg BW0.75 • d). The difference in the lowest and highest activity heat production reported in this experiment was equal to 735 g/d of a corn–soybean meal diet for a 200-kg sow, which equates to 42% of maintenance requirements needed for physical activity. High levels of physical activity may account for sows failing to meet backfat gain targets in gestation.
As backfat group at service increased from <12 mm to >18 mm, the estimated maintenance energy requirement as a percentage of total energy intake increased (P < 0.05), whereas estimated energy available for maternal gain decreased (P < 0.05) as energy intake decreased. For sows in the low-backfat group, estimated energy available for gain was much greater than energy in gain, which was probably due to the greater energy loss in the form of heat and higher activity levels of the low- compared with high-backfat sows. In contrast, the estimated energy in gain for the high-backfat group was greater than the energy available for gain. Also, actual backfat gain was greater than predicted for the high-backfat group at service. Some possible explanations for the higher than expected backfat gains are that sows with higher backfat levels (>18 mm) may have lower maintenance requirements than sows with lower backfat levels (Sundstøl et al., 1979).
Weight Group at Weaning
Sows were also categorized into five weight groups: <150, 150 to 180, 180 to 215, 215 to 250, and >250 kg. For sows in the <150, 150 to 180, and 180 to 215 weight groups, estimated maternal weight gain was greater than predicted, whereas for the highest initial weight group, estimated maternal weight gain was lower than predicted (Table 4). Actual backfat gains were lower than predicted for all weight groups. Estimated energy in gain was much greater than energy available for gain for the two lower initial weight groups. One of the reasons for the difference may be due to the higher protein and lower fat composition of maternal gain in these lighter-weight sows resulting in greater weight gain compared with older, heavier sows. Maintenance energy requirements averaged 82.6% of total energy intake, which was within the range (75 to 85%) reported by Noblet et al. (1990), with sows in the heaviest weight group having the highest maintenance requirements.
|
Implications
|
|---|
At similar energy intake levels above maintenance, gilts gain more weight than multiparous sows due to the difference in the composition of weight gain. Gilts require more maternal weight gain during gestation to achieve backfat gains similar to those of multiparous sows. Sows with low backfat levels are less efficient at utilizing energy for weight and backfat gain than those with high backfat levels. Both parity and weight are each individually important factors that influence energy and nutrient requirements in gestation. These factors should be considered to help to improve the precision in modeling gestation nutrient requirements.
|
Footnotes
|
|---|
1 Contribution No. 04-237-J of Kansas Agric. Exp. Stn., Manhattan 66506. 
2 Current address: 1128 1st Ave., Wainwright, Alberta, Canada T9W 1G9.
3 Correspondence: 242 Weber Hall (phone: 785-532-1228; fax: 785-532-7059; e-mail: Goodband{at}ksu.edu).
Received for publication June 21, 2004.
Accepted for publication September 29, 2004.
|
Literature Cited
|
|---|
Aherne, F. X. 1999. Feeding the gestating sow to achieve backfat targets. Breeding Management Workshop. Pages 33–38 in Proc. Allen D. Leman Conf., St. Paul, MN.
Aherne, F. X., G. R. Foxcroft, and J. E. Pettigrew. 1999. Nutrition of the sow. Pages 1029–1043 in Diseases of Swine. 8th ed. B. E. Straw, S. D’Allaire, W. L. Mengeling, and D. J. Taylor, ed. Iowa State Univ. Press, Ames.
Aherne, F. X., and R. N. Kirkwood. 1985. Nutrition and sow prolificacy. J. Reprod. Fertil. Suppl. 33:169–183.[Medline]
Bergeron, R., and H. W. Gonyou. 1997. Effects of increasing energy intake and foraging behaviours on the development of sterotypies in pregnant sows. Appl. Anim. Behav. Sci. 53:259–270.
Beyer, M., W. Jentsch, L. Hoffmann, R. Schiemann, and M. Klein. 1994. Untersuchungen zum energie- und stickstoffumsatz von graviden und laktierend saun sowie von saugferkeln 4. Mitteilung–Chemische Zusammensetzung und energiegehalt der Knozeptionsprodukte, der reproduktiven Organe und der Lebendmassezunahmen order—abnahmen bei graviden und laktierenden Sauen. Arch. Anim. Nutr. 46:7–35.
Cooper, D. R., J. F. Patience, R. T. Zijlstra, and M. Rademacher. 2001. Effect of energy and lysine intake in gestation on sow performance. J. Anim. Sci. 79:2367–2377.[Abstract/Free Full Text]
Cronin, G. M. 1985. The development and significance of abnormal stereotyped behaviors in tethered sows. Ph.D. Thesis, Agricultural University of Wageningen, The Netherlands.
deh Hovell, F. D. de B., J. G. Gordon, and R. M. MacPherson. 1977. Thin sows. 2. Observations on energy and nitrogen exchanges of thin and normal sows in environmental temperatures of 20 and 5°C. J. Agric. Sci. (Camb.) 89:523–533.
Dourmad, J. Y. 1991. Effect of feeding level in the gilt during pregnancy on voluntary feed intake during lactation and changes in body composition during gestation and lactation. Livest. Prod. Sci. 27:309–319.
Dourmad, J. Y., M. Etienne, and J. Noblet, 1996. Reconstitution of body reserves in multiparous sows during pregnancy: effect of energy intake during pregnancy and mobilization during the previous lactation. J. Anim. Sci. 74:2211–2219.[Abstract]
Dourmad, J. Y., M. Etienne, J. Noblet, and D. Causeur, 1997. Prediction de la composition chimique des truies reproductrices a partir du poids vif et de l’epaisseur de lard dorsal. J. Rech. Porc. France 29:255–262.
Dourmad, J. Y., J. Noblet, M. C. Pere, and M. Etienne, 1998. Mating, pregnancy and prenatal growth. Pages 129–153 in A quantitative Biology of the Pig. I. Kyriazakis, ed. CAB Int., Wallingford, U.K.
Everts, H., and R. A. Dekker. 1995. Effect of protein supply during pregnancy and lactation on body composition of sows during three reproductive cycles. Livest. Prod. Sci. 43:137–147.
Hughes, P. E. 1993. The effects of food level during lactation and early gestation on the reproductive performance of mature sows. Anim. Prod. 57:437–445.
Mullan, B. P., and I. H. Williams. 1989. The effect of body reserves at farrowing on the reproductive performance of first-litter sows. Anim. Prod. 48:449–457.
Noblet, J., W. H. Close, R. P. Heavens, and D. Brown, 1985. Studies on energy metabolism of the pregnant sow. Uterus and mammary tissue development. Br. J. Nutr. 53:251–265.[Medline]
Noblet, J., J. Y. Dourmad, and M. Etienne. 1990. Energy utilization in pregnant and lactating sows: Modeling of energy requirements. J. Anim. Sci. 68:562–572.[Abstract]
Noblet, J., and M. Etienne, 1987. Metabolic utilization of energy and maintenance requirements in pregnant sows. Livest. Prod. Sci. 16:243–257.
Noblet, J., H. Fortune, C. Dupire, and S. Dubois, 1993. Energy cost of standing activity in sows. Livest. Prod. Sci. 34:127–136.
NRC. 1998. Nutrient Requirements of Swine. 10th ed. Natl. Acad. Press, Washington, DC.
Pettigrew, J. E., and H. Yang. 1997. Protein nutrition of gestating sows. J. Anim. Sci. 75:2723–2730.[Abstract/Free Full Text]
Revell, D. K., I. H. Williams, B. P. Mullan, J. L. Ranford, and R. J. Smits. 1998. Body composition at farrowing and nutrition during lactation affect the performance of primiparous sows: I. Voluntary feed intake, weight loss, and plasma metabolites. J. Anim. Sci. 76:1729–1737.[Abstract/Free Full Text]
Sauber, T. E., T. S. Stahly, N. H. Williams, and R. C. Ewan. 1998. Effect of lean growth genotype and dietary amino acid regimen on th elactational performance of sows. J. Anim. Sci. 76:1098–1111.[Abstract/Free Full Text]
Shields, R. G., D. C. Mahan, and P. F. Maxon. 1985. Effects of dietary gestation and lactation protein levels on reproductive performance and body composition of first litter female swine. J. Anim. Sci. 60:179–189.
Sundstøl, F., N. Standal, and O. Vangen. 1979. Energy metabolism in lines of pigs selected for thickness of backfat and rate of gain. Acta. Agric. Scand. 29:337–345.
Tess, M. H., G. E. Dickerson, J. A. Nienaber, J. T. Yen, and C. L. Ferrell. 1984. Energy cost of protein and fat deposition in pigs fed ad libitum. J. Anim. Sci. 58:111–122.[Abstract/Free Full Text]
Tantasuparuk, W., N. Lundeheim, A.-M. Dalin, A. Kunavongkrit, and S. Einarsson. 2001. Weaning-to-service interval in primiparous sows and its relationship with longevity and piglet production. Livest. Prod. Sci. 69:155–162.
Verstegen, M. W. A., J. M. F. Verhagen, and L. A. den Hartog. 1987. Energy requirements of pigs during pregnancy: A review. Livest. Prod. Sci. 16:75–89.
Whittemore, C. T., and Yang, H. 1989. Physical and chemical composition of breeding sows with differing body subcutaneous fat depth at parturition, differing nutrition during lactation and differing litter size. Anim. Prod. 48:203–212.
Williams, I. H., W. H. Close, and D. J. A. Cole. 1985. Strategies for sow nutrition: Predicting the response of pregnant animals to protein and energy intake. Pages 133–147 in Recent Advances in Animal Nutrition. W. Haresign and D. J. A. Cole, ed. Butterworths, London, U.K.
Yang, H., A. R. Eastham, A. Phillips, and C. T. Whittemore. 1989. Reproductive performance, body weight and body condition of breeding sows with differing body fatness at parturition, differing nutrition during lactation, differing litter size. Anim. Prod. 48:181–201.
Young, L. G., G. J. King, J. Shaw, M. Quinton, J. S. Walton, and I. McMillan. 1991. Interrelationships among age, body weight, backfat and lactation feed intake with reproductive performance and longevity of sows. Can. J. Anim. Sci. 71:567–575.
Young, M. G., M. D. Tokach, F. X. Aherne, R. G. Main, S. S. Dritz, R. D. Goodband, and J. L. Nelssen. 2004a. Comparison of three methods of feeding sows in gestation and the subsequent effects on lactation performance. J. Anim. Sci. 82:3058–3070.[Abstract/Free Full Text]
Young, M. G., M. D. Tokach, J. Noblet, F. X. Aherne, S. S. Dritz, R. D. Goodband, J. L. Nelssen, J. van Milgen, and J. C. Woodworth. 2004b. Influence of Carnichrome on energy balance of gestating sows. J. Anim. Sci. 82:2013–2022.[Abstract/Free Full Text]
Top
Abstract
Introduction
