Effect of lactation and rebreeding phase energy intake on primiparous and multiparous sow performance

Fifty-three primiparous sows were used to study the effects of a high-energy, fat-supplemented diet on sow lactation and rebreeding performance. Sows received either a low [Lo, 12.5 Mcal metabolizable energy (ME)/d] or high (Hi, 16.0 Mcal ME/d) energy sorghum-soybean diet during a 28-d lactation. At weaning, sows were randomly allotted, within lactation treatment, to a low (lo, 5.54 Mcal ME/d) or high (hi, 9.61 Mcal ME/d) energy sorghum-soybean diet until the day of first postweaning estrus. Primiparous sows fed Lo weaned larger (P less than .05) litters than sows fed Hi; however, average pig weight was not affected by lactation treatments. Primiparous sows fed Hi had more backfat at weaning (P less than .01) than Lo sows. In contrast, sow weight was not affected by dietary treatments. Neither lactation nor rebreeding treatments influenced days to rebreeding; however, an interaction (P less than .01) was observed. Mean days from weaning to rebreeding for Lolo, Lohi, Hilo and Hihi sows were 10.0, 7.6, 6.9 and 17.1, respectively. Forty sows were maintained on the same dietary treatments during their second parity. Sows receiving Lo during their second parity farrowed and weaned more (P less than .05) pigs than Hi sows. Multiparous sows fed Hi nursed heavier (P less than .05) pigs on d 21 of lactation and at weaning compared with Lo sows. Sows fed Hi were heavier (P less than .05) and had more (P less than .01) backfat at weaning of their second litter compared to Lo sows. Days to postweaning estrus were not affected by lactation or rebreeding diets. Mean length of the second parity rebreeding interval for Lolo, Lohi, Hilo and Hihi sows was 6.2, 10.2, 7.0 and 10.5 d, respectively. These results suggest that feeding levels during lactation of 12.5 Mcal ME/d or higher supported adequate rebreeding performance. Postweaning feeding levels did not influence days to first estrus. Feeding a high energy diet continuously throughout the lactation and rebreeding phases in primiparous sows may lengthen the postweaning interval to estrus.     

Effect of dietary energy intake during lactation on performance of primiparous sows and their litters

A total of 146 primiparous sows was used in four replications of an experiment to investigate the effect of energy intake during a 28-d lactation on sow and litter performance. Dietary treatments consisted of three energy intakes; 10, 12 or 14 Mcal of metabolizable energy (ME) X sow-1 X d-1. All sows were fed equal amounts of crude protein, vitamins and minerals daily, which met or exceeded standard recommendations. The experiment was initiated at parturition. Sow weight and backfat loss during lactation decreased linearly (P less than .001) as energy intake increased. There were no differences in litter size at either 14 d of lactation or weaning. Pig weights on d 14 increased linearly (P less than .05) and litter weights tended to increase linearly (P = .13) as energy intake increased. At weaning, pig weights and litter weights increased (P less than .05) as sow energy intake increased. There were no significant differences in the percentages of sows in estrus by 7, 14, 21 and 70 d postweaning, but sows fed 10 Mcal ME/d had a slightly longer interval from weaning to first estrus than sows fed higher energy intakes. Serum urea concentrations of sows were inversely related to energy intake during lactation. Serum creatinine concentrations were not affected by energy intake. An intake of 10 Mcal ME/d by primiparous sows during a 28-d lactation resulted in reduced sow and litter performance; there was little difference between sows fed 12 and 14 Mcal ME/d.     

Relationship of lactation energy intake and occurrence of postweaning estrus to body and backfat composition in sows

Forty-five crossbred primiparous sows were used to determine the relationship of lactation energy intake and the occurrence of postweaning estrus to (1) body fat (percentage), (2) lean body mass (LBM) and (3) qualitative and quantitative characteristics of adipose tissue. Sows received 8 (Lo) or 16 (Hi) Mcal of metabolizable energy (ME)/d during lactation and 5.4 Mcal of ME/d postweaning. Serum samples were obtained 1 d before weaning (d 0) and analyzed for creatinine and urea-N (indices of muscle and amino acid catabolism, respectively). Subcutaneous adipose tissue samples were obtained and analyzed for total lipid and myristic, palmitic, palmitoleic, stearic, oleic and linoleic acids. Last rib backfat thickness determined at weaning was used to estimate body fat (percentage). Lean body mass was estimated from 48-h creatinine excretion rates determined on d 15 and 16 postweaning. Sows fed the Lo diet that returned (Lo-R) and did not return (Lo-NR) to estrus by d 14 postweaning lost more (P less than .01) weight during lactation, gained more (P less than .01) weight postweaning, had higher (P less than .07) body fat (percentage) and a slight trend toward lower creatinine excretion rate than sows fed the Hi diet that returned to estrus (Hi-R). Adipose tissue from sows in the Lo-R and Lo-NR groups had less (P less than .05) lipid than that from sows in the Hi-R group. Concentrations of oleic and stearic acids were lower and higher (P less than .01), respectively, in adipose tissue from sows in the Lo-R and Lo-NR vs Hi-R groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of exogenous thyroxine on the interval from weaning to estrus of the primiparous sow

A total of 159 primiparous sows were fed 0 (C) or 675 mg/d of thyroprotein (TP) from d -2 until d 14 postweaning. Sows received 8 (LE) or 14 (HE) Mcal of ME/d during a 28-d lactation period. Plasma levels of 3,5,3'-triiodothyronine (T3) and 3,5,3',5'-tetraidothyronine (T4) were determined for d -4, -2, 0, 1, 2, 3, 5 and 7 postweaning. Sows consuming LE lost more weight and backfat during lactation (P less than .01) than HE sows. Litters of sows consuming LE gained less weight than litters of sows consuming HE (P less than .01). Thyroprotein increased plasma levels of both T3 and T4 (P less than .01), whereas energy intake had no effect (P greater than .10) on either of the two hormones. The response to thyroid hormone was not consistent across days postweaning (TP x day, P less than .01). Feeding TP increased T4 (P less than .01) on all days, and T3 was increased (P less than .05) on d 0, 2 and 3 postweaning. Thyroid hormones rose markedly following weaning regardless of TP level. Percentage of sows in estrus by d 7 postweaning for LE-C, LE-TP, HE-C and HE-TP were 80, 78, 92 and 90, respectively. Energy restriction during lactation resulted in fewer sows returning to estrus by d 7 (P less than .03) than those fed HE. However, feeding TP postweaning had no effect on return to estrus, suggesting that the effect of dietary energy restriction during lactation on the interval from weaning to first estrus is not mediated through postweaning thyroid hormone concentrations.     

Effect of restriction of energy during lactation on body condition, energy metabolism, endocrine changes and reproductive performance in primiparous sows

Seventeen Landrace X Large White primiparous sows that farrowed in August 1982 were fed ad libitum (AL, n = 8) or their intakes were restricted (R, n = 9) during lactation. Litter sizes were equalized after farrowing and pigs were not allowed creep feed. Pigs were weaned 23.8 +/- .4 d postpartum. On d 6, 12 and 20 postpartum, all sows were fasted for 16 h and blood samples were collected prior to feeding for analysis of plasma glucose (GLU), urea nitrogen (UN), free fatty acids (FFA), prolactin (PRL) and serum insulin (INS). On d -2, 2 and 4 from weaning, sows were fasted for 16 h and then blood samples were collected hourly from 0 to 6 postprandial for analysis of GLU, UN, FFA, PRL and INS. Serum for analysis of luteinizing hormone (LH), progesterone and estradiol was collected every 6 h from 1 d before until 12 d after weaning. Samples for LH were also collected at 15-min intervals for 3 h at -18, -6, 6, 18, 78, 102, 126, 150, 240 and 480 h from weaning. After weaning all sows were fed 1.8 kg X d-1, and were checked for estrus twice daily. Daily intakes of metabolizable energy (ME) during lactation were greater in AL (12,194 +/- 465 kcal) than in R sows (8,144 +/- 90 kcal). Compared with AL sows, R sows lost more weight and backfat during lactation and had higher postprandial UN levels 2 d before and 4 d after weaning. Reproductive performance and reproductive hormones were not affected by restriction of energy, but frequency of episodic release of LH prior to weaning was greater in sows that exhibited estrus after weaning (n = 12) than in anestrous sows (n = 5). After weaning, LH and estradiol concentrations were similar between estrous and anestrous sows until onset of the preovulatory increase in estradiol in the sows that exhibited estrus. Energy intake, body condition and productivity were similar between anestrous sows and sows that exhibited estrus. On d 12 and 20 of lactation, preprandial levels of GLU were greater and FFA were lower in anestrous than estrous sows. We conclude that restriction of feed intake during lactation affected body condition and metabolism of primiparous sows, but reproductive performance and productivity were not affected. Aberrations in partitioning of energy during lactation may predispose primiparous sows to postweaning anestrus, but the mechanisms by which this occurs have yet to be defined.     

Effect of protein and energy intake by primiparous sows during lactation on sow and litter performance and sow serum thyroxine and urea concentrations

The effects of protein and energy intakes by primiparous sows during a 28-d lactation on thyroxine (T4) and urea concentrations in blood serum of sows, and sow and litter performance were examined in two experiments. Dietary treatments were protein intakes of 380 (LP) and 760 (HP) g of crude protein X sow-1 X d-1 and energy intakes of 8 (LE) and 16 (HE) Mcal of metabolizable energy (ME) X sow-1 X d-1 in a 2 X 2 factorial arrangement. In Exp. 1 (34 sows), neither protein nor energy intake affected serum T4 concentrations. In both experiments, serum urea concentrations during lactation were influenced by both protein (P less than .001) and energy (P less than .001) intakes. In Exp. 2 (221 sows), sows fed LP or LE lost more weight (P less than .001) during lactation than sows fed either HP or HE. Backfat loss was greater (P less than .001) in sows fed diets of LE than HE, whereas sows fed HP lost more backfat (P = .016) than sows fed LP. Pig weights on d 28 were influenced by both protein (P less than .001) and energy (P = .038), with sows that were provided high intakes of either protein or energy having heavier pigs. Litter weight at weaning was heavier (P less than .005) for sows consuming HP. Sows fed LP had larger litters at d 14 (P = .051) and 28 (P = .046) than sows fed HP. Sow energy intake had no effect on litter size or weight. Percentages of sows in estrus by 7, 14 and 35 d postweaning were higher (P less than .004, P less than .030 and P less than .060, respectively) for sows fed HP than LP, whereas sow energy intakes had no effect on the interval from weaning to first estrus.     

Influence of gestation energy level on the production of Large White x Landrace sows

Sixty-four Large White x Landrace primiparous sows were utilized to evaluate the influence of feeding 6 vs 9 Mcal ME/d during gestation on reproductive performance. The sows remained on their respective gestation diets for four parities if they successfully farrowed, rebred and conceived. Sows fed 9 Mcal ME/d gained more weight (P less than .05) through the gestation period during parities 1 and 2 and were heavier (P less than .01) on d 110 of gestation for combined parities. Lactation weight loss was greater (P less than .05) for the sows fed 9 Mcal ME/d, resulting in similar weights at weaning. Ultrasonic backfat measurements were greater (P less than .01) on d 110 of gestation for sows fed 9 Mcal ME/d during parity 1 and remained higher (P less than .01) through the fourth-parity gestation. Although sow weaning weights were similar, sows receiving 6 Mcal ME/d scanned less backfat thickness. Gestation treatment significantly affected consumption of a common lactation diet provided ad libitum. Sows fed 6 Mcal ME/d during gestation consumed an average of 22 kg more feed (P less than .01) during lactation than those sows receiving 9 Mcal ME/d. Litter performance as measured by number and weights of pigs born alive and weaned was not altered (P greater than .10) by gestation energy intake. Days to return to estrus and the number of sows remaining in the study for four parities were similar (P greater than .10) between the two treatment groups. The number of farrowings for the four parities totaled 164, with 83 and 81 farrowings for the sows fed 6 and 9 Mcal ME/d, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dietary medium- or long-chain triglycerides improve body condition of lean-genotype sows and increase suckling pig growth

In a field trial conducted on a commercial swine farm, lean-genotype sows (n = 485) were fed diets containing 0 or 10% supplemental fat as either medium-chain triglyceride or choice white grease from d 90 of gestation until weaning (15.5 d). Effects on standard sow and litter production traits were examined together with assessment of sow body condition using live ultrasound. Daily feed intake during lactation was 10% higher in sows consuming diets without added fat (7.2 vs 6.5 kg; P < 0.01); however, lactation ME (23.9 Mcal/d) and digestible lysine (54 g/d) intakes were unaffected (P > 0.10). Sows supplemented with fat were 4 kg heavier on d 109 of gestation (220 vs 224 kg; P < or = 0.01), 1 d after farrowing (210 vs 214 kg; P < or = 0.01), and at weaning (210 vs 214 kg; P < or = 0.01). Expressed as overall gain, this amounted to a 23% increase (0.66 vs 0.86 kg/d; P < or = 0.01) and was accompanied by a 49% increase in backfat (0.82 vs 1.68 mm; P < or = 0.03) from d 90 to farrowing. Changes in sow weight (-0.01 kg/d) and backfat (+4.2 mm) over lactation were minimal and were not affected by fat supplementation (P > or = 0.10). Longissimus muscle area at weaning was slightly greater (44.96 vs 46.2 cm2) in sows consuming fat than in control sows (P < or = 0.05), but changes in longissimus muscle area were not significant from d 90 to weaning (P > or = 0.10). Gestation length, pigs born alive, average birth weight, survival (d 3 to weaning), and days to estrus were not affected by diet (P > 0.10). However, supplemental fat increased pig ADG (192 vs 203 g/d; P < 0.01) and average pig weaning weight (4.3 vs 4.5 kg) at 15.5 d (P < or = 0.02). No differences between the two fat sources were detected. This large-scale study demonstrated that supplemental fat during gestation and lactation effectively improved sow condition and improved suckling pig performance without affecting energy intake during lactation, implying improved efficiency of sow energy utilization.     

Effects of genetic line and supplemental dietary fat on lactation performance of Duroc and Landrace sows.

A total of 124 Duroc and 99 Landrace primiparous and multiparous sows were assigned, within breed and contemporary group, to control (N) or 10% added fat (F) diets on d 105 of gestation based on parity and genetic line (control or selected for improved sow productivity), to determine the effects of genetic line and fat addition to the lactation diet on sow and litter performance. Weekly feed intake was not affected (P greater than .10) by genetic line for Duroc and Landrace sows but feed intake was reduced (P = .08) during wk 1 to 4 for Duroc sows and during wk 1 and 4 for Landrace sows (P less than .05) when they were fed diet F compared with diet N. Select (S)-line Duroc and Landrace sows lost more weight during lactation (P less than .01) than did control (C)-line sows. Select-line Landrace sows lost more backfat during lactation (P less than .05) than did C-line sows. Landrace sows lost less weight during lactation (P less than .05) when fed diet F than when fed diet N. The total number of pigs born, born alive, and alive at 21 d and at weaning were higher (P less than .01) for S-line Duroc sows, and litter size at 21 d and at weaning was higher (P less than .01) for S-line Landrace sows than for C-line litters within each breed. Pig survival from birth to weaning was increased (P = .07) for Duroc sows fed diet F but not for Landrace sows.(ABSTRACT TRUNCATED AT 250 WORDS)     

Traits affecting postweaning weight gain and feed intake of primiparous sows

Seventy-six primiparous Duroc and Landrace sows from two genetic lines with or without selection for improved sow productivity were used to identify sow traits that affect postweaning gain (positive or negative) and feed intake. Sows lost weight (P less than .01) and consumed less feed (P less than .01) during wk 1 postweaning (37 d) compared with wk 2, 3, and 4. Sows gained more weight during wk 2 and 3 (P less than .01) than during wk 4. Weekly feed consumption was similar during wk 2 and 4 and highest during wk 3 (P less than .05). Sow weight gain postweaning was predicted by sow weaning weight (P less than .01) and adjusted 21-d litter weight (P less than .05) during wk 1, wk 1 to 2, and wk 1 to 4 feeding periods. Feed consumption was best predicted by adjusted litter weaning weight (P less than .01), sow weaning weight (P less than .01), average backfat at farrowing (P less than .01), average backfat change (P less than .05), and adjusted 21-d litter weight (P less than .05). Feed intake was positively correlated (P less than .01; r = .77) and sow weight at breeding, farrowing, and weaning was negatively correlated (P less than .05; r = -.23, -.21, and -.26, respectively) with sow weight gain. Average backfat at weaning was negatively correlated (P less than .05) with gain and feed intake during each period. Adjusted 21-d litter weight and adjusted litter weaning weight were positively correlated with postweaning feed intake (P less than .05; r = .22 and .23, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Nutrition for optimizing breeding herd performance.

Modern sows are younger and leaner at time of mating and probably have poorer appetites than sows of 10 to 15 years ago. Therefore, feeding strategies should aim to minimize weight loss and maintain a sow's body condition throughout her reproductive life. The efficiency with which gilts are introduced into the breeding herd is as important in economic terms as is the efficiency with which the sow returns to estrus after weaning. Gilts should be selected at 50 to 60 kg, and fed a 16% protein diet ad libitum until mated at their second estrus, when they weigh 115 to 120 kg and have 17 to 20 mm backfat. Flushing gilts before the onset of second or third estrus increases ovulation rate of restricted gilts to the levels achieved by gilts fed ad libitum. During gestation, maintenance represents 75 to 85% of total energy requirements. The aim should be to achieve 20 to 25 mm backfat at farrowing. Increased feed intake from day 2 to 3 after mating will not increase embryo mortality. Feeding an extra 1 kg feed/sow/day for the last 10 days of gestation increases piglet birth weight slightly and prevents a loss of 1.5 to 2.0 mm of sow backfat. Wherever possible, sows should be fed ad libitum from the day after farrowing until weaning. Reduced feed intake by lactating sows, for whatever reason, results in excessive weight and condition loss. Excessive weight loss in lactation causes extended remating intervals, a lower percentage of sows returning to estrus within 10 days of weaning, reduced pregnancy rate, and reduced embryo survival. Ovulation rate is not affected by level of feed intake in lactation. It has been suggested that sows will have minimum weaning-to-service intervals when they weigh 150 kg or more at weaning. It is likely that the sow must be anabolic for about 10 days before she will exhibit postweaning estrus. The decision when to rebreed is made some time prior to weaning and is mediated by a host of substrates, hormones, and neurotransmitters. Sows with a delayed return to estrus also have a lower pregnancy rate and smaller subsequent litters. If sows lose considerable weight or condition during lactation, a high level of feeding in the postweaning period will improve embryo survival.     

Influence of energy and protein intake during lactation on body composition of primiparous sows

The effects of energy and protein intakes by 32 primiparous sows during a 28-d lactation on sow and litter performance and sow body composition and bone properties were examined. Dietary treatments were energy intakes of 8 (LE) and 16 (HE) Mcal of ME/d and protein intakes of 380 (LP) and 760 (HP) g of CP/d in a 2 x 2 factorial arrangement. Sows fed diets that were inadequate in either energy or protein lost more weight than did sows fed the HE-HP diet, but backfat losses were greater when energy intake was deficient than when protein was deficient. Carcass measurements were influenced in a similar manner, with energy intake affecting (P less than .001) backfat thickness and protein intake affecting (P less than .05) longissimus muscle area. Heart, kidneys and liver of sows fed LP diets weighed less (P less than .01) and contained less water and protein (P less than .05) than those of sows fed HP. Sows fed LE had heart, liver and viscera that weighed less (P less than .05) than those of sows fed HE. There was less fat (P less than .05) in the heart, lung, liver and viscera of sows fed LE than in those of sows fed HE. Carcass components of the supraspinatus muscle and standardized sections through the longissimus muscle and right shoulder weighed less (P less than .05) from sows fed LP rather than HP, and these components contained less water and protein. Sows fed the LE diets had less fat in the loin soft tissue section, right shoulder section and supraspinatus muscle than sows fed HE. Bone composition and strength were not influenced by dietary treatment. The composition of weight lost during lactation was diet-dependent. Sows fed diets that were deficient in protein but adequate in energy lost large amounts of protein from muscles and internal organs. Energy deficiency resulted primarily in fat loss.     

The influence of gestation feeding strategy on body composition of gilts at farrowing and response to dietary protein in a modified lactation

Previous experiments have indicated that reproductive function in lean, modern genotypes may be more dependent on body protein mass than, as previously believed, on body lipid reserves. This was investigated in a 3 x 2 factorial arrangement of treatments, involving 60 first-parity sows, comparing three pregnancy feeding strategies and two lactation diets. During pregnancy, sows were fed either a basal diet (5 g lysine/kg, 13 MJ of DE/kg [C]) or the same quantity of basal diet + energy source [E], or additional basal diet supplying both protein and energy [A]. The level of supplement for E and A was adjusted weekly to achieve a backfat thickness measurement (P2 position) of 28 mm at farrowing. Isoenergetic lactation diets were fed to appetite and provided either high (180 g CP/kg, 9 g lysine/kg [H]) or low lysine (120 g CP/kg, 6 g lysine/kg [L]). From d 21 of lactation, sows were separated from their litters and housed next to a boar for 8 h each day; final weaning occurred on d 31. Pregnancy treatment differences in backfat and weight were achieved, with C sows having less backfat on d 1 of lactation than E and A sows (E = 28.1, A = 28.0, C = 22.7 kg, P < 0.001). Sows fed additional basal diet were heavier than E sows, which were heavier than C sows (E = 190, A = 201, C = 178 kg, P < 0.001). Average feed intake over lactation showed a pregnancy feeding effect, with E sows eating less than A or C sows (E = 4.9, A = 5.2, C = 5.4 kg/d, P < 0.005). Total lactation weight loss was affected by pregnancy feeding (E = 18.0, A = 19.0, C = 8.4 kg, P < 0.05) and by lactation diet (L = 19.0, H = 11.3 kg, P < 0.05), whereas total lactation backfat loss was affected only by pregnancy treatment (E = 6.9, A = 6.5, C = 4.6 mm, P < 0.05). No pregnancy treatment or lactation diet effects were observed for litter performance. Lactation diet affected weaning-to-estrus interval, with more sows on the H diet coming into estrus within 6 d of partial weaning (P < 0.05), but there was no pregnancy treatment effect. Therefore, voluntary feed intake during lactation was suppressed by increased fat reserves at a limited body protein mass but not when body protein mass was also increased. Partial weaning-to-estrus interval was increased by reduced dietary protein.     

Efficacy of sucrose and milk chocolate product or dried porcine solubles to increase feed intake and improve performance of lactating sows

Two experiments were conducted to determine the voluntary feed intake and performance of lactating sows fed diets containing a sucrose/milk chocolate product (MCP) blend (Exp. 1) or dried porcine solubles (DPS; Exp. 2). Dried porcine solubles is a coproduct of heparin extraction from porcine small intestines. In Exp. 1, mixed-parity sows (n = 108) at two research centers were assigned to a corn-soybean-meal-based diet formulated to contain 0.9% total lysine or a similar diet that contained 4% sucrose and 2% MCP on an as-fed basis. Sows were allowed ad libitum access to dietary treatments from the day of farrowing until pigs were weaned at approximately 21 d postpartum. Diet had no significant effect on voluntary feed intake of sows during lactation, backfat depth, or postweaning interval to estrus, but it had variable effects on body weight changes. Inclusion of the sucrose/MCP blend in diets elicited a 2% improvement in litter weaning weight at one research center and a 6% depression in litter weaning weight at the other center (diet x research center, P < 0.05). Litter size throughout lactation was unaffected by dietary treatment. In Exp. 2, mixed-parity sows (n = 119) at two research centers were assigned to corn-soybean meal-based diets formulated to contain 0.9% total lysine with 0, 1.5, or 3.0% added DPS. Sows were assigned to dietary treatments within research center, farrowing group, and parity at parturition. Dried porcine solubles tended to increase (P < 0.10) total feed consumed in the first 9 d of lactation and average daily feed intake over the entire lactation (6.03, 6.53, and 6.30 kg) for sows fed 0, 1.5, and 3.0% DPS, respectively. Litter size and weight on d 18 of lactation were not affected by concentration of DPS in the diet. Days from weaning to estrus and percentage of sows displaying estrus were not influenced by diet. We conclude that inclusion of the sucrose/MCP blend in the diet for lactating sows had no consistent effect on voluntary feed intake of sows and weight gain of nursing pigs. Inclusion of DPS at 1.5 or 3.0% tended to improve feed intake of lactating sows but had no significant influence on litter performance.     

Quantitative influence of lysine and energy intake on yield of milk components in the primiparous sow.

A regression approach was used to assess quantitatively the influence of lysine and ME intake during lactation on yield of milk components and to determine whether this influence was mediated through precursor metabolite concentrations in the blood. The influence of lysine and energy intake on sow weight and backfat loss also was analyzed by linear regression. Twenty-three primiparous Landrace x Yorkshire sows were fed one of nine corn-soybean meal diets to achieve a matrix of lysine (15, 30, or 45 g/d) and ME (6.5, 11.5, or 16.5 Mcal/d) intakes. Sow BW and backfat losses were found to be predominantly controlled by ME intake (P less than .02), with no response to lysine intake (P greater than .92). Lysine and ME intake explained a smaller portion of the variability in milk component yield on d 8 (R2 less than .34) than on d 22 (R2 = .64 to .78), evidence that dietary effects of milk production increased as lactation progressed. Lysine and ME intake had an interactive influence (P less than .05) on yield of all milk components except lactose, demonstrating that the amount of lysine required to maximize milk production increased as ME intake increased. Strong relationships between diet and most blood precursor metabolite concentrations (R2 = .5 to .7) were detected on d 22. No obvious relationships between precursor metabolite concentrations and milk component yield (R2 = .05 to .2) were observed. These results describe quantitatively the prominent interactive effects of lysine and ME intake on yield of milk components and demonstrate that these effects are not directly associated with changes in precursor pool concentrations.     

Improving sow productivity through management during gestation, lactation and after weaning

Number of pigs produced per sow per year is dependent upon the number of pigs born live, the number that survive to weaning and the interval between consecutive farrowings for the sow. Feeding and management of the sow during late gestation affects birth weight and amount of energy stored as glycogen and lipid in the piglet. Piglets that are heavier and that have more energy stores have a higher survival rate. Adding fat to the sow's diet during the last month of gestation or altering the sow's metabolism to direct more nutrients to the fetus are methods for increasing piglet birthweight and energy stores. Feeding the sow properly during lactation is important for maximum yield of milk and milk energy, which affects survival of pigs to weaning, and for rebreeding performance of the sow after weaning. Energy intake during lactation can be increased by adding fat to diets, and this is beneficial in situations where feed intake is insufficient to meet the sow's requirements. For example, fat supplementation during lactation is beneficial for primiparous sows and for sows lactating during hot weather. The minimum practical lactation length is about 2 wk for normal rebreeding performance of the sow. Split weaning or separation of the litter from the sow for 6 to 12 h/d will shorten the rebreeding interval or induce estrus during lactation. Administration of pregnant mare's serum gonadotropin, with or without human chorionic gonadotropin, will induce estrus during lactation, and the response is better after the second week of lactation. Similar treatments at weaning will shorten the rebreeding interval.(ABSTRACT TRUNCATED AT 250 WORDS)     

The importance of a high feed intake during lactation of primiparous sows nursing large litters

The objective of this study was to investigate whether nursing a large number of piglets has negative effects on lactation and postweaning performance of primiparous sows and whether a greater lactation feed intake can prevent possible negative effects. Data were recorded on 268 ad libitum-fed sows of three genotypes (G1, G2, and G3) in an experiment where litter size was standardized to 8, 11, or 14 piglets during a 4-wk lactation. Compared to G1 and G2, G3 sows were heavier (P < 0.05) and leaner (P < 0.05) at weaning of their litters, lost similar amounts of BW and backfat, and their piglets grew faster (P < 0.05). Compared to G1, feed intake during lactation was higher for G3 sows (P < 0.05), and their risk of a prolonged weaning-to-estrus interval was lower (P < 0.01). Daily feed intake by sows was not affected by litter size in G1 and G3, but it was quadratically affected in G2 (P < 0.05), with a maximum at 10.8 piglets. Backfat loss of the sows increased linearly with litter size (P < 0.05) in G1 and G3. In G2, backfat loss increased only at litter sizes > 9.8 piglets (P < 0.01). Body weight loss of the sow and litter weight gain increased linearly with litter size (P < 0.001). Per extra piglet nursed, sows had a 23% (P < 0.01) higher probability of a prolonged weaning-to-estrus interval. A higher daily feed intake during lactation reduced tissue loss of the sow, increased litter weight gain (P < 0.01), and reduced the probability of a prolonged weaning-to-estrus interval (by 42% per extra kilogram; P < 0.01). Sows with a lower daily body weight loss during first lactation had a larger second litter (1.28 piglets/kg; P < 0.01), and their probability of a prolonged weaning-to-estrus interval was reduced by 61% per kilogram (P < 0.001). With increasing litter size, it is therefore recommended to reduce body weight loss during lactation by stimulating daily feed intake and by genetic selection.     

Effect of roasted or raw peanut kernels on lactation performance and milk composition of swine

A lactation trial involving 105 sows was conducted to determine the effect of 12% roasted or raw, ground, whole, shelled peanuts on sow weight change during lactation, feed intake, piglet and litter weight gain, milk composition, and days to return to postweaning estrus. The trial was conducted using three sow groups during two farrowing seasons, summer (July to September) and winter (December to February). Diets were based on corn plus soybean meal. Diets contained either 5% animal fat or equivalent added fat from 12% roasted or raw, ground, shelled peanuts. The replacement of animal fat by roasted or raw peanuts had no effect (P greater than .20) on sow weight change, average daily feed intake during lactation or days to estrus postweaning, or on piglet weight gain or survival. Milk composition (percentage fat and protein) was not altered (P greater than .20) by source of fat in the summer; however, in the winter, sows fed roasted peanuts had higher (P less than .05) milk fat and protein percentage at 3 d postfarrowing than other treatment groups. At d 7, sows fed 12% roasted or raw peanuts had higher (P less than .05) milk protein than sows fed 5% animal fat. Sows farrowing in the summer had greater (P less than .01) weight loss and consumed less (P less than .05) feed during lactation than sows farrowing in the winter. Sows farrowed in the summer had larger (P less than .05) litters at birth and 14 d postfarrowing and greater (P less than .10) piglet and litter weight gain postfarrowing than those farrowed in the winter.(ABSTRACT TRUNCATED AT 250 WORDS)     

Impact of amino acid nutrition during lactation on luteinizing hormone secretion and return to estrus in primiparous sows.

The impact of the dietary amino acid regimen of primiparous sows on LH secretion and weaning-to-estrus interval was evaluated. Thirty-six sows, nursing litters of 13 pigs, were allocated daily 6 kg of a corn-soybean meal diet containing a high (HP, 1.20% lysine) or low (LP, .34% lysine) protein content during a 23-d lactation. Dietary lysine concentration was achieved by altering the ratio of corn and soybean meal in the diet. Plasma LH, ACTH, and estradiol-17beta were evaluated at 15 min, hourly, and at 6-h intervals, respectively, during 6-h periods on d 0, 5, 10, 15, and 20 of lactation. Sows were checked daily for estrus from weaning to 45 d postweaning. Sows fed the LP and HP diets consumed 4.41 and 4.98 kg of feed daily during lactation. The LP sows weighed less (P < .05), had lighter (P < .05) litters at weaning, and had (P < .05) extended weaning-to-estrus intervals. Mean and baseline LH concentrations and LH pulses/6 h were lower (P < .01) in LP sows, and the differences between LP and HP sows were established by d 10 of lactation. Plasma estradiol and ACTH concentrations were not altered by diet. Mean LH concentrations on d 5 and 10 of lactation were correlated (r = -.54 and -.56, respectively, P < .01) with weaning-to-estrus interval. Also, mean LH concentrations on d 10 were correlated (P < .05) with the magnitude of dietary lysine deficiencies relative to demand for milk synthesis on d 0 to 5 and d 5 to 10 (r = -.39 and -.49, respectively). Inadequate dietary amino acid intake in sows during early lactation results in lower LH secretion by d 10 postpartum and is associated with increased weaning-to-estrus interval.     

Effects of a novel carbohydrate and protein source on sow performance during lactation

Ninety-one primiparous and multiparous sows and their pigs were used to evaluate the effects of a novel carbohydrate- and protein-based feed ingredient (Nutri-Pal, NP) on sow and litter performance during lactation. Nutri-Pal is a feed supplement for sows that consists of a blend of milk chocolate, brewer's yeast, whey products, and glucooligosaccharides. The dietary treatments consisted of a corn-soybean meal control and a corn-soybean meal plus 5% NP fed from d 110 of gestation to weaning. The diets were formulated to be equal in total Lys and ME. Sows were allotted to treatment based on parity, body weight, and the date of d 110 of gestation. There were 46 and 45 sows per treatment over four farrowing groups. Litters were standardized to 10 pigs and weighed within 1 d of farrowing, and all sows weaned at least 8 pigs at an average age of 21 d. Sows were weighed on d 110 of gestation, d 1 postfarrowing, and at weaning. Sows were fed three times daily during lactation. Sows were checked twice daily after weaning for signs of estrus. The weaning weight of sows fed NP was increased (P < 0.10) compared with those fed the control diet. Sows fed the control diet tended (P = 0.11) to lose more weight per day from d 110 of gestation to weaning than the sows fed NP. Otherwise, sow response variables (sow weight on d 110 of gestation and d 1 postfarrowing, d 110 of gestation to d 1 postfarrowing and lactation weight change per day, d 110 of gestation to d 1 postfarrowing, lactation, and total feed intake, days to estrus, pigs born alive or dead, and litter and average pig birth weight) were not affected (P > 0.10) by diet. There were no effects (P > 0.10) of diet on litter performance response variables (pigs weaned, litter and average pig weaning weight and gain, and survival percent). The NP feed ingredient had minor effects on sow productivity, but it did not affect litter productivity indices.