Pregnancy and Litter Size, But Not Lamb Sex, Affect Feed Intake and Wool Production by Merino-Type Ewes

Two experiments (Australia and Mexico) tested whether feed intake (FI) and wool production (WP) are affected by pregnancy (PRG), litter size (LZ), or lamb sex (LS) in Merino-type ewes. In Experiment-1, ewes were either not pregnant (NPR; n = 6), or carrying 1 (PR1; n = 7) or 3 (PR3; n = 11) fetuses, were studied in individual pens. NPR ewes had lower (p < 0.02) FI throughout PRG and lactation (LAC), except around lambing (p < 0.001). Following lambing, FI increased in PRG ewes (p < 0.001) to double the values in NPR ewes. PRG reduced WP (p < 0.001); in PR3, WP was lower than for both PR1 and NPR (p < 0.001). WP decreased during LAC and was lower in ewes rearing lambs than in NPR ewes (p < 0.001). Experiment-2 used 48 pregnant ewes (28 bearing singles and 20 bearing twins). Dam and lamb live weights (LW) and body condition (BC) were recorded from birth to weaning at 60 d, and dam fleece weight (DFW) was measured at weaning (12 months growth). WP was higher in ewes bearing and rearing single lambs than in ewes bearing twins (p < 0.001). DFW was positively (p < 0.01) related to LZ, dam LW, and BC, but not to changes in dam LW during LAC, or to lamb weight at birth or weaning, or LW gain, or LS. In conclusion, FI was affected during PRG and by LZ during LAC, whereas WP was influenced by LZ, but not LS, only during pregnancy.

Sensitivity of breeding objectives to prices and genetic parameters in Australian Corriedale and Polwarth dual-purpose sheep

10.1071/ea9930259 ◽

1993 ◽

Vol 33 (3) ◽

pp. 259 ◽

Cited By ~ 3

Author(s):

NM Fogarty ◽

AR Gilmour

Keyword(s):

Feed Intake ◽

Selection Index ◽

Genetic Correlations ◽

Fibre Diameter ◽

Dual Purpose ◽

Wool Production ◽

Price Differentials ◽

Breeding Objective ◽

Feed Costs ◽

A profit equation was developed for Australian Corriedale and Polwarth dual-purpose sheep kept for both wool and lamb production. Ten traits contribute to income and costs and were included in the breeding objective. These encompass wool production, fibre diameter, and feed intake of breeding ewes and hogget ewe replacements; sale weight and carcass fat depth of lambs; and reproductive rate and mature weight of ewes. The relative economic value for each trait in the enterprise was calculated from the profit equation using income and costs for 1 year. Overall gain ($A) and gain in each trait in the breeding objective from selection using an index of hogget greasy fleece weight, hogget fibre diameter, dam's number of lambs weaned, lamb weight, and lamb fat depth are reported. The sensitivity of the genetic changes in each trait in the breeding objective and index coefficients were assessed for a range of prices of products and feed costs. Sensitivity to changes in heritabilities and genetic correlations was also assessed. The incorporation of these maternal traits into LAMBPLAN is discussed. For the standard parameters and prices used, gain in leanness accounted for one-third of overall gain ($/ewe. s.d. of selection). Other traits that contributed to overall gain were fibre diameter (28%), reproduction (18%), and growth (14%). There was a small gain through feed intake (8%), and a very small loss in wool weight. Measures of fatness, growth, and fibre diameter were the important traits in the selection index. Inclusion of hogget greasy fleece weight and dam's number of lambs weaned each added <1% to the efficiency of the selection index. Varying the sale price for lamb and the price differentials for fibre diameter and fat depth had the greatest impact on overall gain. High lamb price increased gains in both reproduction and lamb weight, whereas, high price differentials for fibre diameter and fat mainly increased gains in the particular trait. A large range in prices for wool had very little effect on the individual traits or overall. Changing feed costs had little effect on overall gain, although high feed cost reduced gains from reproduction which were compensated by reduced feed intake. Halving the heritability value for each trait reduced overall gain, largely through reduction in the trait. Varying the genetic correlations of wool production with other traits had little effect. However, when genetic correlations of reproduction with weight, fat, and fibre diameter were varied there were changes in overall gain, largely through reproduction.

Relative efficiencies of conversion of feed to wool at three levels of nutrition in flocks genetically different in wool production

10.1071/ea9650390 ◽

1965 ◽

Vol 5 (19) ◽

pp. 390 ◽

Cited By ~ 5

Author(s):

AJ Williams ◽

RJ Winston

Keyword(s):

Body Weight ◽

Feed Intake ◽

Differential Response ◽

Intermediate Level ◽

Wool Production ◽

Low Level ◽

Body Weights ◽

Fleece Weight ◽

High Level ◽

Average Body

The efficiency of conversion of feed to wool was measured with adult ewes at three levels of nutrition. During the period at which each level was fed, changes in body weight and feed intake were minimized. These ewes were chosen as representative of the total drops of three flocks, one of which had been selected for high clean fleece weight (Fleece Plus), one for low clean fleece weight (Fleece Minus) and a control flock selected at random (Random). The intermediate and high levels of nutrition were intended to maintain 20 per cent and 44 per cent higher body weights than at the low level of nutrition. The average intakes of lucerne pellets at the low, .intermediate, and high levels of nutrition were approximately 500, 800, and 950 grams a day respectively. The average body weights at these intakes were 30, 36, and 45 kg and the average gains in body weight were -11, +7, and +16 grams a day during the 18 weeks of measurement at each level. There were no differences between the flocks in these measurements. The relative wool production of the Fleece Plus, Random, and Fleece Minus flocks changed between levels of nutrition, being 101 : 100 : 96 at the low level, 120 : 100 : 88 at the intermediate and 121 : 100 : 96 at the high level of nutrition. Part of this differential response could be attributed to different feed intakes between the flocks and part to a smaller decrease in the efficiency of the Fleece Plus flock with increasing level of nutrition. The relative net efficiencies measured at the intermediate level were 116 : 100 : 86.5 for the Fleece Plus, Random, and Fleece Minus flocks respectively.

Reproduction effects on annual fleece production, liveweight and body condition of grazing Merino ewes

10.1071/ea00054 ◽

2000 ◽

Vol 40 (7) ◽

pp. 931 ◽

Cited By ~ 9

Author(s):

C. M. Waters ◽

K. A. Coelli ◽

G. J. Lee ◽

K. D. Atkins

Keyword(s):

Body Condition ◽

Reproductive Cycle ◽

Fibre Diameter ◽

Production Capacity ◽

Major Effect ◽

Wool Production ◽

Merino Wool ◽

Condition Score ◽

Fleece Weight ◽

Reproductive Cycles

This study sought to confirm the long-term consequences of current and previous reproductive cycles on liveweight, body condition and wool growth over the lifetime of Merino ewes (2–6 years of age). Liveweights and body condition scores at 4 stages of the reproductive cycle, and annual fleece weights (greasy and clean), fibre diameter and yield were analysed to determine the effects of the previous and current reproductive performance (birth-type or rearing-type categories) using records from about 3300 Merino ewes collected between 1977 and 1989. The major effect of current reproduction on liveweight and wool production was associated with fertility, although both birth and rearing types also contributed. Ewes that lambed in the current year weighed 5.2 kg less at weaning and grew 0.4 kg less clean wool annually than dry ewes, while ewes that reared a lamb to weaning weighed 4.3 kg less than ewes that lost their lamb(s). The effects on condition score followed those of liveweight. The effects of previous reproduction on liveweights and condition scores were large and, although diminishing with time, lasted for at least 10 months, whereas any effects on annual fleece weight and mean fibre diameter were small. The results suggest that many ewes may enter the next reproductive year before recovering from the reduction in either liveweight or body condition associated with the previous reproductive cycle. Since Merino ewes are required to produce both wool and replacement sheep, the changes in a ewe’s production capacity associated with reproduction are important to Merino wool production enterprises as their profitability may be influenced.

Effects of level of feeding after mating on ‘fat’ and ‘thin’ sows

Proceedings of the British Society of Animal Production (1972) ◽

10.1017/s030822960001624x ◽

1986 ◽

Vol 1986 ◽

pp. 118-118 ◽

Cited By ~ 1

Author(s):

N. Walker

Keyword(s):

Litter Size ◽

Body Fat ◽

Body Condition ◽

Early Pregnancy ◽

Feed Intake ◽

Feed Rate ◽

High Intake ◽

Large White ◽

Fat Reserves ◽

High Feed

Pregnant sows in poor body condition require a high feed intake to restore body fat reserves. However, a high intake in the period following conception may increase embryo losses. The first objective of this experiment was to determine whether a high feed allowance after conception has any effect on litter size compared with a normal allowance. The second objective was to investigate the effects of body condition at conception and feed rate in early pregnancy on the components of maternal gain.Multiparous cross-bred sows of Large White and Landrace lineage were classified subjectively at farrowing according to body condition as either fat (F) or thin (T). A single diet containing 12.5 MJ DE/kg and 150 g CP/kg was fed throughout the experiment. The fat sows were fed more generously than the thin sows during the 28 day lactation with mean intakes of 5.3 and 4.8 kg/day. This was to maintain the differential in body condition between the two groups. After weaning all sows were fed 3 kg per day until mating. Within the fat and thin groups sows were allocated at random to either 4 or 2 kg of feed per day for 30 days after mating.

Measurements of wool production and its physiological components in a group of South Australian Merino sheep.

Australian Journal of Agricultural Research ◽

10.1071/ar9610696 ◽

1961 ◽

Vol 12 (4) ◽

pp. 696 ◽

Cited By ~ 2

Author(s):

KJ Hutchinson

Keyword(s):

Body Weight ◽

Conversion Efficiency ◽

Feed Intake ◽

Dry Matter ◽

Individual Values ◽

Wool Production ◽

Voluntary Feed Intake ◽

Unit Body Weight ◽

Prime Determinant ◽

Data for wool production, feed intake, and body weight were recorded for a group of 31 rams selected from the South Australian strong-woolled Merino flock at Roseworthy. Measurements were made during (a) grazing, and (b) ad libitum pen feeding. A locally developed faecal nitrogen method was used to estimate intakes at pasture. For the pen diet, which contained 15% crude protein, two measurements of apparent dry matter and nitrogen digestibility were made for each sheep. The repeatability of gross conversion efficiency of feed into wool under grazing versus pen feeding was highly significant, viz. r = +0.79. While the repeatability of wool production was also highly significant, viz. r = +0 77, the repeatability of feed intake was not significant in these data, viz. r = +0 12 In pens, voluntary feed intake was found to vary with body weight to the power of + 1 09, the 99% fiducial limits extending from +0.81 to + 1 37 and thus excluding fractional powers conventionally assigned to basal metabolic nee&, e.g. +0.7. The physiological components of wool production were studied with the use of' the pen data. An identity was used which involved three terms, viz. gross conversion efficiency of feed into wool, gross feed intake per unit body weight, and body weight. Of these, gross conversion efficiency was the prime determinant of wool production. Gross feed intake per unit body weight was significantly associated with wool production (P<0.05), while the relationship between wool production and body weight was not significant in these data. In the pen experiment 'the regression relationship between voluntary feed intake and body weight accounted for approximately one-half of the variation in voluntary feed intake. A negative association between body weight and efficiency was also revealed. However, the general significance of this latter finding is doubtful, particularly in view of the variable relationships recorded between body weight and clean fleece weight for rams in 5 years' data from the general Roseworthy flock. For the experimental group of 31 rams, substantial differences were recorded in individual apparent digestive efficiencies for both dry matter and nitrogen. The ranges of individual values, expressed as four standard deviations, were 9.2 and 12.2% respectively. However, these differences did not contribute to differences in gross conversion efficiency of feed into wool, which suggests that the latter resides in either general or special aspects of metabolism.

Performance of crossbred progeny of Trangie Fertility Merino and Booroola Merino rams and Poll Dorset ewes. 3. Reproduction, liveweight and wool production of adult ewes

10.1071/ea9951083 ◽

1995 ◽

Vol 35 (8) ◽

pp. 1083 ◽

Cited By ~ 5

Author(s):

NM Fogarty ◽

DG Hall

Keyword(s):

Birth Weight ◽

Litter Size ◽

Significant Variation ◽

Ovulation Rate ◽

Average Birth Weight ◽

Wool Production ◽

Component Traits ◽

Lamb Survival ◽

Fleece Weight ◽

Almost All

Reproduction, liveweight and wool production are reported for 4 cohorts of 377 Trangie Fertility x Dorset (TD) and 261 Booroola x Dorset (BD) ewes over 6 years. The BD ewes were 3-4 kg lighter (P<0.001) and had a higher ovulation rate prior to joining in February-March (2.37 � 0.03 v. 1.65 � 0.03) than TD ewes. This resulted in a higher litter size (2.07 � 0.03 v. 1.66 � 0.04) and number of lambs born per ewe joined (1.92 � 0.04 v. 1.56 � 0.04) for the BD ewes. Lamb survival was lower from BD than TD ewes (0.71 � 0.02 v. 0.85 � 0.02), so that the 2 ewe strains weaned the same number of lambs. The growth rate of lambs was lower from the BD ewes and overall they weaned 3.8 kg less (P<0.001) weight of lamb than TD ewes. Chill (index of environmental conditions at lambing), litter size and average birth weight of lambs in the litter (linear and quadratic) affected (P<0.001) lamb survival. At moderate levels of chill there was little difference in survival of single and twin lambs from BD and TD dams when birth weight was 4-5 kg, but survival declined more rapidly for progeny of BD ewes at lower birth weight. Under severe lambing conditions survival was depressed more for lambs born from BD ewes than TD ewes. Almost all ewes expressed oestrus over the 3, 6-week periods, December-January, January-February and March (joining). There was significant variation (P<0.001) in incidence of oestrus due to year and age (linear and non-linear), but not liveweight at joining, and there was little difference between ewe strains. Similarly, for post-lambing oestrus (to fit 8-monthly joining) and post-lambing anoestrous interval, there was little difference between strains, but year and age were highly significant (P<0.001). BD ewes had a lower (P<0.001) greasy fleece weight (3.76 v. 3.86 kg), than TD ewes. BD ewes were classified as either carriers (F+) or non-carriers (++) of the FecB gene, which was significant (P<0.001) for ovulation rate (+1.14 ovulations), litter size (+0.8 lambs), lamb survival (-18%), lambs born per ewe joined (+0.64 lambs) and total weight of lamb born per ewe joined (0.5 kg, P<0.01). The effect of the FecB gene was non-significant for lamb survival when litter size and lamb birth weight (P<0.001) were included in the model. Repeatability estimates based on over 3 records per ewe were about 0.2 for lambs born, weight of lamb born, lambs weaned and weight of lamb weaned per ewe joined. Component traits ranged from 0.27 for litter size to 0.10 for lamb survival, with fertility intermediate (0.15). Greasy fleece weight (0.72) and ovulation rate (0.41) had high repeatabilities with post-lambing anoestrous interval being low (0.11). Repeatability for ovulation rate was reduced to 0.34 when F+ ewes were excluded.

Genetic parameters for reproduction and lamb production and their components and liveweight, fat depth and wool production in Hyfer sheep

Australian Journal of Agricultural Research ◽

10.1071/ar9940443 ◽

1994 ◽

Vol 45 (2) ◽

pp. 443 ◽

Cited By ~ 26

Author(s):

NM Fogarty ◽

LD Brash ◽

AR Gilmour

Keyword(s):

Genetic Correlation ◽

Litter Size ◽

Genetic Parameters ◽

Genetic Correlations ◽

Production Traits ◽

Wool Production ◽

Reproduction Traits ◽

Component Traits ◽

Lamb Survival ◽

Hyfer is a new composite breed suited to specialized lamb production and developed from Dorset (+), Booroola Merino (+)and Trangie Fertility Merino (+) genotypes. Genetic parameters estimated by restricted maximum likelihood methods are reported for liveweight, wool production and a range of reproduction and lamb production traits. Estimates of heritability were 0 44 � 0.10, 0.222 � 0-08 and 0.28 � 0.08 for liveweight, ultrasonic fat depth (C site) and fat depth adjusted for liveweight respectively, for 1454 rams averaging 14 months of age, which were the progeny of 130 sires. The genetic correlation for ram liveweight and fat depth was 0.06 � 0.17 and -0.30 � 0.16 with adjusted fat depth. Estimates of heritability for ewe liveweight at 12-18 months of age and greasy fleece weight at 11-19 months of age were 0.61 � 0.10 and 0.38 � 0.08 respectively, with a genetic correlation of 0.35 � 0.13, based on 1619 ewes, which were the progeny of 135 sires. A maternal effect was significant for ewe liveweight and its inclusion in the model reduced the estimate of heritability to 0.44 � 0.09. Young ewes were joined three times in two years in an accelerated 8-monthly lambing system, and joinings commenced in mid-February, late October and mid-June. The estimates of heritability for overall ewe performance were for lambs born 0.09 � 0.03, lambs weaned 0.04 � 0.02 and weight of lamb weaned 0 -06 � 0.02 (all per ewe joined). Heritabilities for the component traits were: fertility 0 -03 � 0 02, litter size 0.19 � 0.04 and lamb survival 0.07 � 0.03. Estimates of repeatability for the corresponding traits ranged from 0.11 to 0.15, except for litter size (0.26 � 0.02). Estimates of heritability for lambs born, lambs weaned and weight weaned were higher for the first joining than when estimates were based on three joining records. This was associated with higher heritability for fertility from first joining (0.10 � 0.06) than for all three records and the reverse for lamb survival. Estimates of heritability for mean ewe performance were considerably higher and in agreement with the values predicted from the repeatability analyses and number of records, illustrating the value of using repeated ewe records for selection. The genetic correlations between the component traits and overall measures of lamb production were not high enough to consider using component traits as indirect selection criteria. The genetic correlations of liveweight with reproduction traits were positive, but generally not significant, and ranged from 0.01 to 0.63, except for litter size (-0.19 � 0.17). The genetic correlations of greasy fleece weight with reproduction traits were generally smaller than those for liveweight, were not significant and ranged from -0.12 to 0.32. These results, together with others, will be used to compile parameter sets for use in LAMBPLAN to provide meatsheep breeders with comprehensive breeding objectives incorporating growth, leanness, wool and reproduciton.

Standardized Ileal Digestible Lysine

Impact of feed intake in early gestation on maternal growth and litter size according to body reserves at weaning of young parity sows

Journal of Animal Science ◽

10.1093/jas/skaa075 ◽

2020 ◽

Vol 98 (3) ◽

Author(s):

André L Mallmann ◽

Gabriela S Oliveira ◽

Rafael R Ulguim ◽

Ana Paula G Mellagi ◽

Mari L Bernardi ◽

...

Keyword(s):

Litter Size ◽

Body Condition ◽

Feed Intake ◽

Body Condition Score ◽

Metabolizable Energy ◽

Early Gestation ◽

Unit Class ◽

Condition Score ◽

Farrowing Rate ◽

Abstract The effect of increasing the feed level (1.8, 2.5, and 3.2 kg/d) during early gestation in parity 1 (PO1) and parity 2 (PO2) sows on maternal growth and litter size was evaluated. A total of 361 sows were group-housed and fed a diet based on a corn–soybean meal (3.15 Mcal Metabolizable Energy (ME) per kg and 0.68% standardized ileal digestible lysine) from day 6 of gestation until day 30. Sows were weighed at weaning and on day 30 of gestation. Farrowing rate, number of total piglets born, piglets born alive, stillborn piglets, and mummified fetuses were recorded at farrowing. The effect of feed level on the total number of piglets born was also evaluated according to classes of body weight (BW), body condition score (BCS), backfat (BF), and caliper unit at weaning for each parity order. There was no evidence for significant effect of the interaction between feed level × parity on the variables related to maternal growth and reproductive performance (P ≥ 0.128). Greater feed levels linearly increased the gains in body condition (i.e., BW, BCS, BF, and caliper unit) between weaning and day 30 of gestation (P < 0.001). Farrowing rate was not influenced by the feed level (P ≥ 0.200) and parity (P ≥ 0.209). The number of total piglets born decreased linearly as the feed level increased (P = 0.041), whereas no evidences for differences were observed on piglets born alive among treatments (P ≥ 0.317), neither between parities (P ≥ 0.904). For PO1 sows, the total piglets born on BW classes (≤183 vs. >183 kg) and on classes of BF (≤11.5 vs. > 11.5 mm) were quadratically affected by the feed levels (P ≤ 0.041). In contrast, the number of total piglets born was marginally affected (linear; P ≤ 0.094) by the feed level in the different classes of BW, BCS, and caliper unit in PO2 sows. There was no evidence for differences for the interaction of feed level and classes of body condition (P ≥ 0.199) for PO2 sows. Similarly, no interactions between feed level and classes of BW, BCS, and BF at weaning were observed (P ≥ 0.233) for PO1 sows; however, the total piglets born were affected by an interaction between feed level and caliper unit class (P = 0.042). In conclusion, increased feed intake from day 6 of gestation until day 30 resulted in increased maternal BW gain but reduced the number of total piglets born. Furthermore, lighter and in a poor BCS PO1 sows at weaning produced fewer total born piglets with no benefits from greater amounts of feed.

269 Effects of high phytase supplementation in lactation diets on sow and litter performance

Journal of Animal Science ◽

10.1093/jas/skaa054.175 ◽

2020 ◽

Vol 98 (Supplement_3) ◽

pp. 101-102

Author(s):

Kelsey L Batson ◽

Hilda I Calderon Cartagena ◽

Robert D Goodband ◽

Jason C Woodworth ◽

Mike D Tokach ◽

...

Keyword(s):

Body Weight ◽

Litter Size ◽

Feed Intake ◽

Control Diet ◽

Small Scale ◽

Body Weight Change ◽

Weaning Weight ◽

Commercial Trial ◽

Quadratic Response ◽

Dietary Treatments

Abstract A total of 109 sows (Line 241; DNA, Columbus, NE) were used in a study to evaluate the effect of increasing phytase concentration in lactation diets on sow and litter performance. On d 107 of gestation, sows were blocked by body weight and parity and allotted to 1 of 3 dietary treatments of increasing phytase concentration (0, 1,000, or 3,000 FYT/kg; Ronozyme HiPhos 2700; DSM Nutritional Products, Inc., Parsippany, NJ). The control diet contained no phytase and was formulated to contain 0.50% standardized total tract digestible phosphorus (STTD P; 0.45% available P) and 0.62% STTD calcium (0.90% total Ca). The same STTD P and Ca concentrations were formulated for the phytase diets considering a release of 0.132 STTD P and 0.094 STTD Ca in both diets. Diets were fed from d 107 of gestation until weaning (d 18 ± 2). Litters were cross-fostered within treatment until 48 h post-farrowing to equalize litter size. Linear and quadratic response to phytase concentration was evaluated using the lmer function in R. There was no evidence for difference in sow body weight change, farrowing performance, wean-to-estrus interval, or litter size among dietary treatments. Sow average daily feed intake from farrowing to weaning tended to increase (linear, P=0.093) as phytase increased. Although not significant (linear, P =0.226), farrowing duration decreased as phytase increased. Litter weaning weight increased (quadratic, P=0.039) and overall litter gain increased (quadratic, P=0.047) with 1,000 FYT of phytase. In summary, sow feed intake tended to increase linearly with increasing phytase; however, feeding 1,000 FYT/kg maximized overall litter gain and weaning weight. This small-scale study suggests sow and litter performance benefits due to high inclusions of dietary phytase; however, a commercial trial with more sows is warranted to confirm these results.

27 Defining a robust sow: swine nutrition perspective on reproduction and lactation

Journal of Animal Science ◽

10.1093/jas/skz122.023 ◽

2019 ◽

Vol 97 (Supplement_2) ◽

pp. 13-13

Author(s):

Joel M DeRouchey ◽

Mike D Tokach ◽

Robert D Goodband ◽

Jason C Woodworth ◽

Steve S Dritz ◽

...

Keyword(s):

Birth Weight ◽

Milk Production ◽

Body Condition ◽

Fetal Growth ◽

Feed Intake ◽

Energy Requirement ◽

Meta Analysis ◽

Mammary Development ◽

Late Gestation ◽

Embryo Survival

Abstract Improvements in modern sow prolificacy have markedly increased the number of pigs weaned, thus the ability of sows to provide nutrients to support fetal growth and milk production has been enhanced. The goals of the gestation nutrition program consist of meeting the nutrient requirements for maintenance and growth and for adequate conceptus development, while managing body condition. Early gestation represents the best opportunity for replenishing body reserves, whereas in late gestation, both estimated protein deposition and energy requirement are exponentially increased and directed towards fetal growth and mammary development. Increased feed intake after breeding has been presumed to be detrimental to embryo survival; however, data with modern line sows demonstrates to feed thin sows to recover body condition as quickly as possible while avoiding feed deprivation immediately after breeding. Importance of body condition scoring remains unchanged: feed thin sows to bring back to adequate body condition and prevent over-conditioned sows at farrowing. A recent meta-analysis showed increasing late gestation feed intake seems to modestly improve piglet birth weight by 28 g per piglet in gilts and sows. Also, recent findings in gestating sows suggest modern genotypes have improved feed efficiency and propensity for growth. Therefore, increasing energy intake during late gestation has a modest effect on piglet birth weight and a negative effect on stillborn rate. Historically, lactation catabolism impacted subsequent reproductive performance of sows, particularly in first-parity. However, contemporary sows appear to be increasingly resistant to the negative effects of lactational catabolism. Even so, continued emphasis on maximizing lactation feed intake is critical to support milk production and prevent excessive lean tissue mobilization. Research data suggests that ad libitum feeding and offering lactation diets during the wean-to-estrus interval is not needed. Modern genetic sow lines appear to be more robust from a nutritional perspective than in the past.