Effect Of Dietary Energy Constitution On Reproduction And Lactation Performance Of Sows

The regulation of dietary compositions and nutritional level of sows increase litter sizes of sows and milk production, and improve quality of milk.These are the important ways to reduce mortality of suckling piglets, increase litter weight and improve the reproduction performance of sows. In the current work, pregnant and lactating sow were used to study the effects of inclusion of fibrous feeds on reproductive performance of sows, and the effect of high-energy diet on reproductive performance of sows during late pregnancy and lactation. Based on the results obtained in the above studies, the low-pregnancy high-lactation dietary structure was designed. The effects were studied on the sow reproduction and growth performance of piglets, and the mechanism involved were discussed in terms of plasma biochemical parameters and endocrine in sows, and blood glucose storage, biochemical parameters and hormone level in serum, and expression of growth hormone receptor (GHR) gene in liver in piglets.Part 1. The experiment was conducted to study the effect of inclusion of fibrous feed on reproduction performance in sowsThirty-two health and uniform-sized Duroc sows with parity of 4-6 and on 25 days after mating were divided into 4 groups (n=8) according parity.Four levels of alfalfa meal (0%,20%,40% and 60%) were designed and their effects were investigated on reproductive performance, apparent digestibility, biochemical index and hormone level in serum, and the nutritional compositions of colostrum in sows. Inclusion of alfalfa meal in diets significant increased the litter size and alive litter size compared to no alfalfa meal diet (P<0.05), and the survival rate of piglets increased by 22.2,11.1 and 24.4%, respectively. The individual weight of firstborns decreased with the increase in alfalfa meal level (P＜0.05). Litter weight was significantly higher in 20% alfalfa meal group, with no significant difference compared to 40 or 60% alfalfa meal group (P>0.05). Survival rate of weaning pigs was higher in 20% alfalfa meal group. Body weight gain of sows in lactation did not decrease when 20 or 40% alfalfa meal was fed, but the marked decline in sow body weight was found in 60% alfalfa meal group (P<0.05). The backfat thickness was decreased with increasing level of alfalfa meal. The weaned litter weight was the highest in 20% alfalfa meal diet,11.3% higher than no alfalfa meal diet. The effects of alfalfa meal level on apparent digestibility coefficients of dry matter, calcium and neutral detergent fiber were not significant (P>0.05), but apparent digestibility of crude protein and crude fat decreased significantly.Level of alfalfa meal did not have significant influence on the blood glucose, total protein, albumin, globulin and urea nitrogen in serum (P>0.05). Inclusion of alfalfa meal at levels of 20,40 or 60% all increased serum IGF-I level significantly (P<0.05). From the above results, it is concluded that inclusion of 20% alfalfa meal in diet may result in optimal effect on reproduction performance in sows.Part 2. Two experiments were conducted to study the effect of high digestible energy diet on the reproductive performance of sowsIn Expt.l, twenty DⅢand DⅢ-1 line Duroc×Zhejiang white sows with similar pregnancy period were divided into two groups randomly based on strain, parity and the identical mating boars. The control diet without fat was formulated according to Chinese Feeding Standard, while the treatment diets were reinforced with protein and amino acids and included with 8% of lard dregs to elevate the energy density. The effect of feeding high-protein-high-energy diets was investigated on reproductive performance of sows. The birth weight and birth litter weight of piglets slightly increased (P>0.05) in the fat-included group compared to the control, respectively. However, the litter weight and individual weight of piglets at 21 or 35 days of age was increased by 22.2 and 32.7% or and 27.0 and 32.7% (P<0.01), respectively compared with control groups. It is indicated feeding high nutrition diet (high energy and high AA) during late pregnancy and early lactation period could increase milk production of sows, and hence improve the development and growth performance of piglets.Primiparous (n=12) and multiparous (n=12) Taiwan Duroc sows (averaged parity 4.67) were used in Expt.2 to study the effect of dietary fat addition on the reproduction performance and lactation performance of sows. Sows were divided into 4 groups randomly based on expeted farrowing time and average parity. The experiment began on the 90th days of pregnancy and lasted to 30 days post farrowing. The effect of parity (Primiparous and multiparous) and fat addition was studied on the production performance of lactating sows. Alive litter size and weaning litter size in primiparous Duroc sows were significantly lower than those of multiparous sows (P<0.05). Piglet survival rate in primiparous sows was not affected by dietary fat, but was increased 3.69% in multiparous sows. Feed intake was unchanged by treatment (P>0.05). Milk production of multiparous sows was increased,33.8% higher than that of primiparous sows. Inclusion of fat in diet had little influence on milk production of primiparous sows (P>0.05), but increased milk production of multiparous sows by 11.6%. The piglet daily gain and weaning litter weight were not affected by dietary fat in primiparous sows, but increased in multiparous sows.Part 3. Two experiments were conducted to study the effects of dietary energy structure with low-pregnancy-high-lactation on reproductive performance of sows and growth performance of piglets.In Expt.l,24 multiparous (parity 4-6) pure Duroc sows were divided into 4 groups (2×2 factorial design) according to body weight and parity. The diets in first half of pregnancy were fat-free and two levels of alfalfa meal (0 and 20%) were added in. In late pregnancy and lactation period, each level of alfalfa meal group was divided into two sub-groups and added with 0 or 8% of fat, respectively. All the lactation diets were exclusive of alfalfa meal. Dietary energy level had little effect on feed intake of lactating sows. Body weight gain during pregnancy was higher in 20% alfalfa meal group than control (P＜0.05), with a significant interaction between alfalfa meal and fat (P<0.05). Alive litter size was significantly higher in sows fed with 20% alfalfa meal diets (P＜0.05), but did not affected by dietary fat added in late pregnancy (P>0.05). The weaning survival rate of piglets and weaning litter weight increased in 20% alfalfa meal diet (P＜0.05), and the highest weaning litter weight was obtained in sows fed 20% alfalfa meal plus 8% fat diet. The birth weight of piglets was significantly lower in 20% alfalfa meal group than that in non alfalfa meal and non fat group (P＜0.05). The lower weaning weight of pigs was found in 20% alfalfa meal group but without significant difference.The milk production of sows at the first 15 days of lactation were not significantly different between different groups, but sows fed with 20% alfalfa meal and 8% fat powder showed the highest milk production, with a significant interaction between alfalfa meal and fat (P＜0.05). The effect of alfalfa meal on milk production during the whole period tended to be significant (P=0.09). Fat powder also had the enhancing effect on milk production, though the difference was not significant (P＞0.05). The fat level in colostrum at 24 h postpartum was increased significantly by inclusion of alfalfa meal (P＜0.05), but little difference was found at 48 h colostrum (P>0.05). The fat addition in diet tended to increase the amount of 24 h colostrum, but showed little differences on other parameters (P>0.05). The alfalfa meal and fat powder both improved the milk energy density. At 7 days postpartum, milk fat contents and energy density were affected significant by dietary fat,15.0 and 9.5% higher compared with non fat diet, respectively. The IGF-I level in milk at 24 h postpartum was not affected by alfalfa meal, but was 11.5% (P=0.16) higher compared to non fat group.Inclusion of 20% alfalfa meal in diet increased the serum IGF-I level of pregnant sows (P<0.05). Serum insulin level on 90 days of pregnancy was reduced in sows fed 20% alfalfa meal diet, but increased at 24 h postpartum (P＜0.05). The cholesterol level was significantly increased in pregnancy sows when 20% alfalfa meal diet was fed, but was not affected for lactating sows. Fat powder addition significantly increased the triglyceride level on 21 days postpartum (P<0.05).Experimental design of Expt.2 was similar to that in Expt.1. Six newborn and six weaned piglets were killed for each group (1 head per litter), respectively to study effects of sows'nutritional level on the glycogen storage, blood biochemical indexes, hormone level and GHR gene expression in liver. Glycogen content in liver was independent with dietary fat and alfalfa meal. The growth hormone in blood of newborn and weaned piglets were significant increased by dietary fat powder (P<0.05). However, the GHR mRNA expression abundance in the newborn piglets for 20% alfalfa meal group was higher than non alfalfa meal group (P>0.05). The GHR mRNA abundance in liver of newborn piglets increased (P=0.06) for fat-fed group, and 34.4% higher in weaned pigs compared with non fat group (P＜0.01).In summary, reproduction performance of sows is greatly influenced by the dietary energy level. Inclusion of fibrous feeds may increase birth litter size and improve weaned litter weight of piglets, but overfeeding will have adverse influence on survival rate of weaning piglets. From the results obtained in the current study, it is concluded that the dietary nutritional level may change milk composition of sows and enhance the expression of GHR gene in liver of piglets, resulting in favorable change in the related serum hormones and hence improved survival and growth performance of piglets.