Fit of Wood's function to weekly records of milk yield, total digestible nutrient intake and body weight changes in early lactation of multiparous Holstein cows in Japan

The aim of this study was to determine the interrelationships between milk yield, total digestible nutrient (TDN) intake and body weight. A total of 14,900 records of weekly (from the 1st week to 20th week after calving) weights of milk yield and TDN intake and body weight from 745 multiparous Holstein cows in Japan were used. In addition, attempts were made to predict energy requirement in early lactation of dairy cows using metabolizable energy (ME) system. The Wood's function (y_t = at^be^− ct) was fitted to each animal record to derive secondary traits (parameters, weeks at peak or bottom, maximum–minimum values and predicted daily body weight gain). The average goodness of fit, as assessed by the R² value, was highest for TDN intake (0.82) and lowest for body weight (0.59). The weeks at peak milk yield and TDN intake and minimum weight were 6.0, 10.0 and 5.5, respectively. Phenotypic correlations within the same trait were negative between parameters a and b and positive between b and c. Relatively large correlations between traits were obtained for a values and maximum–minimum traits (maximum milk yield and TDN intake and minimum body weight). In addition, the phenotypic correlations between predicted daily gain and a value for milk yield were negative during the first 5 weeks after calving. A comparison of ME intakes estimated from Wood's function and ME intake predicted from energy systems showed that the mean-square prediction error (MSPE) was largest in the first week and smallest in the fourth week. The results suggest that the Wood's function is inadequate in predicting body weight changes in early lactation.     

Incidence of nursing sickness and biochemical observations in lactating mink with and without dietary salt supplementation.

The impact of dietary sodium on the incidence of nursing sickness in mink dams and on the average litter biomass of 28 and 42 day old kits was studied. One group (n = 115 including 12 barren females) was given a standard feed mixture with a natural content of 0.53 g NaCl/MJ and another group (n = 115 including 8 barren females) was given the same feed mixture supplemented with NaCl to a final content of 1.00 g/MJ. The average dam weight at weaning was significantly lower (P < 0.001) and the incidence of nursing sickness during the last part of the lactation period 3 times higher in the nonsupplemented group. The average litter biomass at weaning did not differ between the 2 experimental groups. A number of biochemical markers of preclinical nursing sickness, e.g. plasma aldosterone and osmolality, Na+ and Cl concentrations in plasma and urine, were studied during the last part of the lactation period and at weaning in 20 dams of the nonsupplemented group, in 10 dams of the salt supplemented group and, for comparison, in 5 + 5 barren females on the day corresponding to day 34 after parturition in nursing mink. The nonsupplemented group had significantly lower concentrations of sodium and chloride in plasma and urine and a significantly higher concentration of plasma aldosterone as compared to the salt supplemented group. Distinct signs of relative salt deficiency and preclinical nursing sickness thus characterized the nonsupplemented group throughout this period, while more blurred hints of electrolyte imbalances were noticed in the sodium chloride supplemented group at weaning. A beneficial effect of salt supplementation on the incidence of nursing sickness was shown; however, it remains unclear whether salt deficiency can cause nursing sickness or whether salt acts as an appetite stimulant preventing inanition and the development of the disorder.     

Effect of birth weight,gender and litter characteristics on summer mortality in lambs of Norwegian breeds

Abstract

This study describes how birth weight, gender, litter size, and age of dam affect lamb mortality during the summer period, using data on lambs of the breeds Spælsau (N ≈ 110 000) and Norwegian White Sheep (N ≈ 450 000) during 1994 to 2005. A general mixed linear model was used for the analysis. Birth weight affected summer mortality non-proportionally: an increase in weight from very small towards the breed mean strongly deflated mortality risk; weigh increase above breed means had little effect. Male lambs had a higher mortality than females, and lambs born by 12-months-old dams were in greater risk than those having older dams. Increasing litter size resulted in increased mortality. The results are discussed and recommendations for future research, with focus on breeding and genotype by environment interaction effects are made.     

Genetic variation in litter size and kit survival of mink (Neovison vison)

The aims of this study are to estimate variance components of litter size and kit survival rate and estimate genetic correlations of litter size and kit survival rate with dam's juvenile body weight and pregnancy length. Variance components for litter size and kit survival were analysed using an AI-REML approach, based on data from 1940 litters of the black colour type mink from 1996 to 2001. The models included (i) additive genetic effect of dam; (ii) dam and sire genetic effects; (iii) additive genetic effect of dam in relation to litter size and dam and sire genetic effects in relation to survival rate; (iv) additive genetic effect of dam to estimate the correlations of litter size or kit survival with dam juvenile body weight and pregnancy length on yearling dams (1357 litters). The dam heritabilities were of litter size (0.02-0.08) and survival rate (0.05-0.10). The permanent effects of dam were important for litter size (0.15-0.19) but not for survival rate. A positive dam genetic correlation between litter size and survival rate was found at 1 week postpartum (0.42), and a positive sire genetic correlation between number of weaned kits and survival rate at the age of 6 month (0.72). Litter size and survival rate were genetically antagonistically related to dam's juvenile body weight (-0.34 to -0.53). These results indicate the following: (i) it is possible to improve litter size and kit survival by selection, (ii) effective improvement of kit survival rate in the suckling period requires selection for maternal effect on kit survival and kit's own capacity to survive and later in the growth period for kit's own ability to survive and (iii) antagonistic genetic correlation of dam juvenile body weight with litter size and survival rate should be taken into consideration in mink breeding programs.     

Direct and maternal genetic differences between lines of mice selected for body weight and litter size: traits of dams

Genetic differences in performance of dams were estimated by linear contrasts using means of two selected lines of mice and reciprocal F1's, F2's and backcrosses. The lines were selected for increased 6-wk body weight (W) or increased litter size (L). Genetic differences estimated were direct average (gD), direct heterosis (hD), maternal average (gM), progeny average (gP), and progeny heterosis (hP). For dam weight and feed consumption from 12 to 21 d postpartum (pp), gD was the largest genetic difference and favored line W. For litter size, litter weight at birth, litter efficiency (litter weight gain/dam feed consumption) from birth to 12 d pp and within litter mortality from 1 to 21 d pp, gD favored L and, except for hD in litter efficiency, was the most important genetic difference for these traits. Direct heterosis was the only significant difference for litter weight at 21 d pp, litter efficiency from 12 to 21 d pp and within litter mortality at parturition. The gM were larger in W than in L for dam weight and feed consumption, and for litter size and weight at birth, but they were usually of smaller magnitude than gD. The gP were significant only in litter traits measured before 12 d pp and favored W. For no trait measured was hP of consequence. Line differences in dam and litter weight accounted for genetic differences in dam feed consumption. Genetic differences in litter size at birth were not due to line differences in dam weight. The lower mortality within litters nursed by crossbred dams was responsible for hD on litter weight and litter efficiency. Within but not among lines, higher mortality rates were associated with larger litters.     

Energy intake and milk production in mink (Mustela vison)--effect of litter size.

Energy intake and milk production were measured in 12 mink dams raising litters of 3, 6 and 9 kits one to four weeks post partum by means of balance experiments and measurements of milk intake of the kits by the water isotope dilution technique. The dams were fed ad libitum on a conventional wet mink diet (DM: 323 g/kg; CP: 173 g/kg; ME: 4.4 MJ/kg). Milk samples collected from dams with corresponding litter sizes and lactation weeks, and body composition of kits nursed by these dams, were analysed for content of DM, ash, N and fat. The ME and drinking water consumption were higher in dams nursing 9 kits than in dams nursing 3 kits. The N and water balances as well as the live weight of dams were not affected by litter size. Daily milk production was higher in dams nursing 9 kits than in dams nursing 3 kits. The DM, N and fat content of the milk increased during lactation, but were not affected by litter size. Individual kit live weight was higher in litters of 3 than in litters of 6 and 9 kits four weeks post partum. The DM and fat content of the kits were lowest in kits from litters of 9 kits, whereas these kits had the highest protein content. Daily ME for maintenance of kits and the efficiency of utilisation of ME in milk for body gain were estimated to 356 kJ/kg0.75, kp approximately 0.53 and kf approximately 0.71, respectively. In conclusion, daily milk production increased with increasing litter size, but not in proportion to the number of kits, indicating that milk production limits the growth rate of the young. In the fourth week of lactation, milk production was not different between dams nursing 6 or 9 kits, indicating a maximum capacity.     

Donkey Feeding During Maintenance,Pregnancy, and Lactation: Effects on Body Weight,Milk Production,and Foal Growth

We evaluated the daily intake in donkeys during maintenance, late pregnancy, and early lactation. The growth curves of the foals in the first eight weeks of life and the milk production in lactating jennies were also investigated. Donkeys were separated into two groups: seven pregnant jennies (group 1: pregnant/lactating) and seven nonpregnant, nonlactating jennies (group 2). The groups were fed two different diets each. The feeding period for group 1 covered eight weeks before parturition and eight weeks postpartum. Group 2 was managed during the same time period (16 weeks). Diet 1 consisted of ad libitum hay, which was fed to group 1 during late pregnancy and to group 2 from weeks 1–8. Diet 2 consisted of the same ad libitum hay supplemented with 2 kg/head/day of concentrate, which was fed to group 1 during lactation and to group 2 from weeks 9–16. The daily dry matter intake (diet 1) was 2.56 kg/100 kg of body weight (BW) for nonpregnant jennies and 31% lower in the pregnant donkeys. In the lactating jennies, the total dry matter intake was similar to the nonpregnant group fed diet 2. The nonpregnant jennies lost 1.9% of their initial BW when fed diet 1, whereas they gained 8.4% of their initial BW when fed with diet 2. A weight loss was also found in the lactating donkeys. The foals more than doubled in their birth weight within two months.     

Reallocation of body resources in lactating mice highly selected for litter size

The present study investigated differences in the allocation patterns of body stores in lactating female mice from a line selected for high litter size at birth (S-line, average litter size of 20) and dams from a nonselected control line (C-line, average litter size of 10). Body weight, litter size, litter weight, and absolute and relative lipid and protein mass were measured at peak lactation (2 wk in lactation) and at weaning (3 wk in lactation). Body size in S-line females has been increased as a correlated effect of selection for high litter size at birth, allowing for larger litters and higher absolute milk production. However, these dams produce larger litters relative to their own body weight. At peak lactation, lipid and protein percentage did not differ between lines. At weaning, S-line females had a higher protein percentage (P < 0.001) and lower lipid percentage (P < 0.05) than C-line females. Apparently, S-line females produce more offspring but at a greater cost to their own metabolism. This process was insufficient to supply the offspring with adequate resources, resulting in reduced (P < 0.0001) pup development and increased (P < 0.0001) preweaning mortality rates.     

Der Einfluß der uterinen Umwelt auf Köorperlangen und Körpergewicht, untersucht an monozygoten Rinderzwillingen nach Embryotransfer auf eine oder zwei Ammen

–The influence of uterine environment on body length and body weight, studied in artificially prepared calf twins transfered as embryos into two foster mothers The following three different types of twins were compared in Ostfrisian cattles: (1) artificially prepared identical twins transfered as embryos into two foster mothers (allouterine, monozygotic twins), (2) identical twins derived from one transfered blastocyst which separates into two parts spontaneously (isouterine, monozygotic twins), (3) groups of sister blastocysts which were trensfered into different foster mothers (allouterine, dizygotic twins). Twelve different traits of body length and the body weight were repeatedly estimated in 105 male and female animals aged between three weeks and more than one year. Their means apee in (l), (2) and (3). By ANOVA Modell II the components s² _w were compared between the three types of twins. s² _w in (1) shows the environmental influences pre– and postnatally with 5–25% of the total variance. s² _w in (2) shows the environmental influence of the postnatal period with < 7% of the total variance. The uterine environment participates with 4–20% in the total variance of traits of body length and weight in calves one year of age. By sister comparisons(2) and (3)heritability was estimated to be (h²=) 0.33 to 0.66. Heritability plus uterine plus postnatale components of variance covers only 50–70% of the total variance. An inexplicable rest variance remains indicating a third cause of variance beside genetic and environmental reasons as described by “intangible variance” or “emergenesis”.     

Physiological Changes in Mink (Mustela vison) Dams Subjected to Weaning at Different Times during Lactation

The influence of time of weaning on weight changes, and on hormone and electrolyte status in domestic mink (Mustela vison) dams raising at least five kits per litter was examined. The kits were weaned at either day 42 (group 1) or day 49 (group 2) after birth. The dams were weighed and urine and blood were sampled from day 29 to day 56 after delivery. A considerable loss of dams' body weight, constituting 6.3% in group 1 and 8.1% in group 2, was noticed on the day after weaning, indicating a greatly reduced food consumption on the day of weaning. No changes in plasma aldosterone and no significant decrease in urinary sodium concentration were seen in dams after removal from their litters, whereas, irrespective of time of weaning, urinary sodium and chloride concentrations were halved a few days after weaning compared with the other group. The plasma cortisol concentration was high before and during weaning and was nearly halved 1 week after weaning, implying less strain on the dams after weaning. It is concluded that the weaning period is a most vulnerable and stressful period to the dams irrespective of the actual time of weaning.     

Correlated responses in maternal performance following divergent selection for heat loss in mice

Divergent selection in mice was applied in 3 independent replicates for high (maintenance high; MH) and low (maintenance low; ML) heat loss for 16 generations. An unselected control (maintenance control; MC) was also maintained in all replicates. Selection ceased for 26 generations; heat-loss measurement and selection resumed at generation 42. Lactation performance, dam weight, dam feed intake, and efficiency of production of pup weight were recorded or calculated for MH and ML dams in all 3 replicates at generation 46 or 47 with the objective of determining whether selection for heat loss has created correlated responses in maternal performance. One-half of the dams reared their own litters, and one-half reared cross-fostered (across lines) litters. Between 10 and 12 litters were used from each replicate-line-rearing class. Litter size was recorded, and litters were standardized to 8 pups within 24 h of birth. For cross fostering, MH litters were matched to ML litters born within 24 h of each other, and MH-ML litter pairs were cross-fostered at 3 d of age. A weigh-suckle-weigh protocol was used to obtain milk production estimates over a 2-h suckling period at 6, 9, 12, and 15 d. Dam (plus litter) feed intake was also recorded at these times and was calculated as the disappearance of feed over 3-d intervals. Dams of the MH selection tended (P < 0.11) to have greater litter size than those of the ML selection; litter size of MC dams was intermediate. Line of dam affected milk production (P = 0.04) and dam feed intake (P < 0.03) as MH dams produced more milk and consumed more feed than ML dams. Average milk production for the 2-h measurement period was 1.70 +/- 0.07 and 1.41 +/- 0.07 g, and average 3-d feed consumption was 50.8 +/- 1.2 and 45.2 +/- 1.2 g for MH and ML dams, respectively. Cross-fostering had no effect (P > 0.86) on milk production. Line of dam tended to affect 21-d litter weight (P = 0.15) with litters reared by MH dams weighing more than those reared by ML dams, but there was no difference (P > 0.86) in 21-d dam weights. Efficiency of producing litter weight (litter 15-d weight: dam plus litter feed intake from d 6 to 15) was greater (0.49 vs. 0.46, SE = 0.009; P = 0.03) for ML than for MH dams. Selection for reduced heat loss (lower maintenance feed intake in the ML line) resulted in reduced milk production and feed intake in dams and greater efficiency of litter weight production.     

Insulin resistance: Relationship between indices during late gestation in dairy cows and effects on newborn metabolism

To investigate the relationship between insulin resistance indices [“Revised quantitative insulin sensitivity check index” (RQUICKI; RQ), “Revised quantitative insulin sensitivity check index ‐ β‐hydroxybutyrate” (RQUICKI_BHB; RQ_BHB), and “Homeostasis model assessment‐insulin resistance” (HOMA‐IR; HR)], and metabolic parameters in dams during late gestation, and their newborn calves. Blood was sampled twice weekly during the experimental period in 30 dry Holstein cows. In calves, blood sampling and body weight measurements were performed immediately after birth, and in 1‐week‐old male calves, liver and muscle biopsy samples were obtained for determining metabolic factor mRNA levels. RQ and RQ_BHB were negatively correlated with insulin, nonesterified fatty acid, BHB, and albumin and were positively correlated with leptin levels in blood during late gestation (p < .05). RQ, rather than RQ_BHB, reflected metabolism of dams, while stronger positive correlations were present between HR and blood insulin concentrations than other parameters, and calves of dams with high HR had low body weight, and high liver and muscle expression of growth hormone and insulin receptor mRNA (p < .05). RQ and HR of dams during late gestation could serve as indicators of dam metabolism and predictors of metabolism in newborn calves respectively.     

Postpartum performance in a diallel cross among lines of mice selected for litter size and body weight

Postpartum dam performance was studied in a complete diallel design involving five lines of mice. The selection criterion in each line was: large litter size at birth (L+); large 6-wk body weight (W+); an index for large litter size and small 6-wk body weight (L+W-); the complementary index (L-W+) and random (K). Females from the five lines and 20 reciprocal F1 crosses were mated to sires of a randomly selected control line (CC). Correlated responses in average direct genetic and average maternal genetic effects for dam body weight and litter size at parturition persisted throughout lactation, indicating important pleiotropic effects. Major correlated responses occurred for litter weight, feed intake and litter feed efficiency, primarily due to average direct genetic effects. Using general combining ability and net line effects as criteria for choosing among lines, L+ had a distinct advantage if the objective was to increase litter size in a crossing program. If the objective was to maximize litter weaning weight, then W+ would be favored for net line effects, while L+ and W+ would be about equivalent for general combining ability. None of the lines had an advantage for litter feed efficiency. Direct heterosis for dam weight at 12 and 21 d of lactation averaged 2.7 and 1.9%, while for litter size the respective averages were 7.4 and 7.3%. The W+ X L+W- cross exhibited overdominance for litter size. Direct heterosis was moderate for feed intake and litter weight, but was negligible for litter feed efficiency because of the mathematical relationship among the three traits. Maternal heterosis for preweaning progeny growth was suppressed because of heterosis for litter size in the dam. Grand-maternal effects on growth of the young were small and would not be an important consideration in choosing among these lines in a crossbreeding program.     

Genetic parameters for litter size,piglet growth and sow's early growth and body composition in the Chinese–European line Tai Zumu

Genetics of piglet growth in association with sow's early growth and body composition were estimated in the Tai Zumu line. Piglet and sow's litter growth traits were calculated from individual weights collected at birth and at 3 weeks of age. Sow's litter traits included the number of piglets born alive (NBA), the mean piglet weight (MW) and the standard deviation of weights within the litter (SDW). Sow's early growth was measured by the age at 100 kg (A₁₀₀), and body composition included backfat thickness (BF₁₀₀). A main objective of this study was to estimate separately the direct genetic effect (d) and the maternal genetic effect (m) on piglet weight and daily weight gain during lactation. Variance components were estimated using the restricted maximum likelihood methodology based on animal models. The heritability estimates were 0.19 for NBA, 0.15 and 0.26 for SDW and MW at 3 weeks and 0.42 and 0.70 for A₁₀₀ and BF₁₀₀. The NBA was almost independent from SDW. Conversely, the A₁₀₀ and BF₁₀₀ were correlated unfavourably with SDW (r_g<−0.24, SE<0.12). A stronger selection for litter size should have little effect on litter homogeneity in weights. Selection for lean growth rate tends to favour heterogeneity in weights. The direct effect on piglet weight at birth and daily weight gain accounted for 12% (h² (d) = 0.02) and 50% (h² (d) = 0.11) of the genetic variance, respectively. The association between d and m for piglet weight was not different from zero at birth (r_g = 0.19, SE = 0.27), but a strong antagonism between d and m for daily weight gain from birth to 3 weeks was found (r_g = −0.41, SE = 0.17). Substantial direct and maternal genetic effects influenced piglet growth until weaning in opposite way.     

Estimation of the optimal standardized ileal digestible lysine requirement for primiparous lactating sows fed diets supplemented with crystalline amino acids

This experiment was conducted to determine the optimal standardized ileal digestible lysine (SID Lys) level in diets fed to primiparous sows during lactation. A total of 150 (Landrace × Large White) crossbred gilts (weighing 211.1 ± 3.5 kg with a litter size of 11.1 ± 0.2) were fed lactation diets (3325 kcal metabolizable energy (ME)/kg) containing SID Lys levels of 0.76, 0.84, 0.94, 1.04 or 1.14%, through 28 days lactation. Gilts were allocated to treatments based on their body weight and backfat thickness 48 h after farrowing. Gilt body weight loss was significantly (P < 0.05) decreased by increasing dietary SID Lys levels. Fitted broken‐line (P < 0.05) and quadratic plot (P < 0.05) analysis of body weight loss indicated that the optimal SID Lys for primiparous sows was 0.85 and 1.01%, respectively. Average daily feed intake (ADFI), weaning‐to‐estrus interval and subsequent conception rate were not affected by dietary SID Lys levels. Increasing dietary lysine had no effect on litter performances. Protein content in milk was increased by dietary SID Lys (P < 0.05). Dietary SID Lys tended to increase concentrations of serum insulin‐like growth factor I (P = 0.066). These results of this experiment indicate that the optimal dietary SID Lys for lactating gilts was at least 0.85%, which approaches the recommendation of 0.84% that is estimated by the National Research Council (2012).     

Effects of Carbohydrate-free Diets on the Performance of Lactating Mink (Mustela vison) and the Growth Performance of Suckling Kits

The effects of carbohydrate-free diets on body weight changes, feed consumption, and plasma concentrations of nutrients, metabolites, and hormones in lactating mink and on growth performance in kits were investigated in a total of 108 litters during the lactation period of seven weeks. The litters were distributed in three experimental groups fed different ratios of metabolisable energy (ME) derived from protein and fat (61:38; 47:52; 33:66). The females and kits were weighed at parturition and 2, 3, 4, and 7 weeks after parturition. Blood samples were collected from females in the second, fourth, and sixth week of the lactation period. Carbohydrate-free diets fed to lactating mink can in principle support normal performance, health of the females, and growth performance of the kits. However, mink need a sufficient supply of available gluconeogenic precursors in the form of amino acids. In the present experiment, the diet with 33% of ME from protein contained insufficient amounts of gluconeogenic precursors for lactating mink, and three weeks post partum this group was excluded from the experiment. The differences in dietary protein level (61% and 47% of ME) and fat level (38% and 52% of ME) influenced the plasma concentrations of free fatty acids (FFA) and urea, but had minimal influence on plasma concentrations of other nutrients, metabolites, and hormones.     

Effects of prepartum administration of 1,3-butanediol to sows on growth and survival of neonatal pigs

In six trials, 158 late-term gravid sows were fed isocaloric amounts (8,500 kcal metabolizable energy/d) of a corn-soybean meal-based diet in which 20% of their daily metabolizable energy (ME) intake was supplied by either cornstarch or 1,3-butanediol (butanediol) from about d 105 of gestation to parturition. After parturition, all sows were allowed to consume a standard, corn-soybean meal-based lactation diet, ad libitum, during a 28-d lactation. Prepartum administration of butanediol, a stable, nonvolatile liquid that possesses anesthetic, antimicrobial and ketogenic properties, did not alter the voluntary feed intake or body weight changes of sows pre- or post-partum. Number of pigs born per litter, average pig birth weight and incidence of stillbirths were not influenced by the prepartum diet of the sows. However, the addition of butanediol to the prepartum diet increased (P less than .10) the number of pigs weaned per litter at 28 d by .51 pigs (8.17 vs 7.66) and improved (P less than .10) the survival rate of pigs from birth to weaning by 5.7 percentage units (84.1 vs 78.4%) compared with those of sows fed isocaloric additions of starch. Average pig weights at 28 d of age were similar for the two treatment groups (6.18 vs 6.08 kg) even though greater numbers of pigs were nursing sows fed the butanediol diet prepartum. The rate and efficiency of gain and survivability of weanling pigs during a 28-d postweaning period were not influenced by the prepartum diet of their dam.     

Growth rate of growing pigs is weakly correlated genetically with litter size,while the amount of genetic variation for growth rate changes with litter size

Abstract

We reasoned that if we assessed pigs for litter size and growth rate during the grow-out stage of production (25–100 kg body weight) we would find: 1) an unfavourable genetic correlation between litter size and growth rate; and 2) that the amount of additive genetic variation expressed for growth rate varies with litter size. We tested these premises by assessing 2212 litters from the Yorkshire breed for litter size, while 3038 growing pigs from 550 of these litters were assessed for growth rate during the grow-out stage of production. Genetic correlations were estimated using the additive genetic (co)variances obtained from a bivariate linear animal model fitted to litter size and growth rate. The amount of additive genetic variation expressed for growth rate as a function of litter size was estimated by fitting a univariate linear animal model with random regression on litter size. Our findings did not support the first of our premises as we found that the genetic correlation between litter size and growth rate was favourable (0.28±0.27), albeit not significantly different from zero. However, we were able to support our second premise as we found that the relationship between amount of additive genetic variation for growth rate and litter size was quadratic; the amount of additive genetic variation was highest in small and large litters (h²=0.60 and 0.65), and lowest in intermediate litter sizes (h²=0.29). These findings indicate that: 1) breeding for litter size would not reduce the growth rate of growing pigs; and 2) the amount of genetic variation for growth rate changes with litter size.     

Effect of dietary fibre on reproductive performance of sows during the first two parities

The aim of this study was to investigate the effect of dietary fibre on reproductive performance during the first two parities. Gilts were randomly allocated to receive three fibrous diets from days 1-90 of gestation, including low fibre [low fiber (LF), 10.8% neutral detergent fiber (NDF), n=132], middle fibre [middle fiber (MF), 15.8% NDF, n=132] and high fibre diet (HF, 20.8% NDF, n=135), until completion of the second parity. Response criteria included backfat measurements, litter size and pig weight at parturition and day 22 of lactation, weaning-oestrus-interval, oestrus rate, sow farrowing and culling rate, uniformity of newborns and relative organ weights. The results showed sows fed LF diet in parity 1 gained more backfat (p<0.05) during gestation but lost more (p<0.05) during lactation than sows fed HF diet. Furthermore, sows fed LF diet farrowed more pigs (+0.7-1.1 pigs, p<0.05) and pigs born alive (+1.0 pigs, p<0.05) relative to sows fed HF diet. Likewise, sows fed LF and MF diets had greater litter weights at parturition (both p=0.06) and day 22 after lactation (both p<0.05). In parity 2, yet, it was MF diet to increase both total pigs born and pigs born alive (+0.9-1.1 pigs, p<0.05) and litter weight (p=0.05) relative to other diets. After 22 d of lactation, intriguingly, sows fed HF diet had most pigs alive (p<0.01-0.07) and heavier litter weight (p=0.07 or 0.2). Feeding HF diet also increased internal organs weight of newborns (p<0.05). Collectively, feeding LF and MF diets had beneficial effects on litter weight at parturition and day 22 of lactation in parity 1, and feeding MF diet until parity 2 was able to improve litter size and weight at parturition, but this positive effect disappeared after 22 days of lactation, instead feeding HF diet showed the optimal litter performance.     

Free-range system and supplementation of 25-hydroxicholecalciferol increases the performance and serum vitamin levels in mixed-parity sows

Improvements in sow productivity have raised questions regarding dietary vitamin D recommendations. The present study aimed to evaluate the effects of the housing system with access to sunlight exposure and supplementation of 25-hydroxicholecalciferol on performance and serum levels of 25(OH)D₃ in sows during gestation and lactation. Sows were distributed in an experimental design with two housing systems: gestation crates or gestation free-range system with external area for sunlight exposure; and two diets: 0 or 50 μg of 25-hydroxicholecalciferol kg⁻¹. The use of 25-hydroxicholecalciferol tended (P = 0.052) to improve total born and influenced (P = 0.046) on number of born alive. Litter weight at birth was also increased (P = 0.01) by 25-hydroxicholecalciferol supplementation; 25-hydroxicholecalciferol supplementation and housing system (free-range with sunlight exposure) tended to increase weaning weight (P = 0.07) and litter daily gain (P = 0.051) during lactation. Exposure to sunlight and 25-hydroxicholecalciferol supplementation increased 25(OH)D₃ serum levels when compared with control treatment during gestation (136.95 vs. 113.92 ng mL⁻¹; P = 0.035) and lactation (120.29 vs. 88.93 ng mL⁻¹; P = 0.026). In conclusion, the association of 25-hydroxicholecalciferol supplementation with exposure to sunlight during gestation improved significantly 25(OH)D₃ serum levels and consequently performance traits in gestation and lactation.