Supplementing metabolizable protein to ewes

Published March 31, 2015

Supplementing metabolizable protein to ewes during late gestation: II. Effects on ewe lamb performance and reproductive efficiency1 M. L. Van Emon,*†2 C. S. Schauer,* S. R. Eckerman,*† K. R. Maddock Carlin,† and K. A. Vonnahme†3 *Hettinger Research Extension Center, North Dakota State University, Hettinger 58639; and †Department of Animal Sciences, North Dakota State University, Fargo 58108

ABSTRACT: The objective of the current study was to determine the effects of maternal MP intake in isocaloric diets during late gestation on female offspring growth from birth to breeding and measure reproductive performance of those offspring in their first breeding season. In yr 1, maternal dietary treatments were applied at d 100 of gestation, were similar in total energy, and contained 60MP1, 60% of MP requirements; 80MP1, 80% of MP requirements; and 100MP1, 100% of the MP requirements on a DM basis during late gestation. In yr 2, maternal dietary treatments were similar in total energy and contained 60MP2, 60% of MP requirements; 100MP2, 100% of the MP requirements; and 140MP2, 140% of MP requirements on a DM basis during late gestation. While there was a quadratic effect (P = 0.003) for ewe lamb birth weight with the ewe lambs from 80MP1 ewes having increased birth weights compared with ewe lambs from 60MP1 and 100MP1 ewes in yr 1, there was no effect (P ≥ 0.22) of maternal diet on growth of ewe lamb offspring thereafter. A quadratic

effect (P = 0.02) was observed for the percentage of ewe lambs bred during the first 17 d of the breeding season, with more ewe lambs born to ewes fed 80MP1 bred compared with ewe lambs born to ewes fed 60MP1 and 100MP1. Ewe lambs giving birth within the first 17 d of lambing season increased (P = 0.001) linearly as MP intake increased in the maternal diet. In yr 2, there was no effect (P ≥ 0.07) of maternal MP treatment during late gestation on growth of ewe lambs and reproductive performance except ADG from birth to weaning and lamb birth weight. There was a quadratic effect (P = 0.01) for ADG from birth to weaning of ewe lambs from ewes consuming 100MP2 being increased compared with ewe lambs from ewes fed 60MP2 and 140MP2. There was a linear (P = 0.04) reduction in birth weight of lambs born to ewe lambs as the dam’s maternal dietary MP intake increased. The data from the current study suggest that feeding 80% or 100% of MP requirements during late gestation may have the greatest positive impacts on female offspring reproductive performance.

Key words: ewe lambs, late gestation, metabolizable protein © 2015 American Society of Animal Science. All rights reserved. INTRODUCTION Maternal nutrition during gestation may be crucial to maintaining offspring reproductive success as 1This

project was supported by National Research Initiative Competitive grant No. 2009-35206-05276 from the USDA National Institute of Food and Agriculture to K.A.V., C.S.S., and K.R.M.C. The authors would like to thank Dave Pearson, Don Stecher, and Don Drolc for their help with the projects. 2Current address: Montana State University, Department of Animal and Range Sciences, Bozeman, 59717 3Corresponding author: [email protected] Received January 15, 2014. Accepted January 8, 2015.

J. Anim. Sci. 2015.93:1332–1339 doi:10.2527/jas2014-7609

it directly impacts fetal reproductive organ development (Rhind et al., 2001; Rhind, 2004). Antral follicle count, a predictor of fertility, is decreased in offspring from dams that are nutrient restricted, even though birth weights were unaffected (Evans et al., 2012). In sheep, maternal dietary restriction during gestation decreased ovarian weight of the offspring as well as ovarian and follicular cellular proliferation (Grazul-Bilska et al., 2009). Moreover, reduced maternal nutrient intake resulted in less prolific ewe lamb offspring (Gunn et al., 1995). However, to our knowledge, there is little information determining how protein intake during gestation impacts female offspring reproductive performance of livestock species. In rats, maternal protein restriction throughout gestation resulted in longer estrous

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MP intake in gestation on ewe lamb offspring

cycles in female offspring as well as a shorter reproductive lifespan (Guzmán et al., 2006). Moreover, maternal protein restriction during gestation negatively impacts follicular ovarian development and steroidogenesis in the prepubertal rat offspring (Guzman et al., 2014). In cattle, maternal protein supplementation during the last third of pregnancy enhanced heifer calf growth and reproductive performance (Martin et al., 2007). We hypothesized that metabolizable protein (MP) supply in the last third of pregnancy will impact the reproductive success in female progeny from proteinsupplemented dams. Moreover, we hypothesized that feeding ewes MP at or above requirements would improve female offspring growth and reproductive performance and that restriction of MP would decrease the offspring’s reproductive capabilities. The objective of the current study was to determine the effects of maternal MP intake in isocaloric diets during late gestation on female offspring growth from birth to breeding and measure the ability to mate, lambing rate, twinning rate, and subsequent birth weight of lambs from offspring in their first breeding season. MATERIALS AND METHODS All procedures were approved by the North Dakota State University Animal Care and Use Committee (#A0921). Maternal nutrition study and design have been previously reported in Van Emon et al. (2014). In yr 1, we investigated the role of two inadequate levels of MP in isocaloric maternal diets in order to assess how much MP restriction could be tolerated without hindering maternal performance (Van Emon et al., 2014) as well as offspring performance (this study). In yr 2 of the study, the levels of dietary MP were chosen to assess if excess MP provided in isocaloric diets would be beneficial to either maternal performance (Van Emon et al., 2014) or the offspring (this study). Animals and Study Design Ewes Year 1. Briefly, on ~ d 50 of gestation, multiparous western-whiteface pregnant ewes (n = 295) were moved to and maintained in a common group pasture at the Hettinger Research Extension Center (Hettinger, ND). On ~ d 90 of gestation, ewes exposed to Rambouillet rams were moved to a total confinement barn and placed into 21 pens (20 pens of 14 ewes/pen; 1 pen of 15 ewes/ pen) and acclimated to low-quality straw (Table 1) and the 100MP1 supplement (100% of the MP requirements, as determined by NRC, 2007; Table 2) for 7 d prior to

Table 1. Nutrient composition of fescue straw and lactation ration in yr 1 and 2 Item Diet, % DM DM, % NEm, Mcal/kg CP, % of DM MP, % of DM NDF, % of DM ADF, % of DM Ash, % of DM

Fescue straw1 Year 1 Year 2 64.51 56.51 83.05 77.61 2.22 2.12 3.04 3.07 1.95 1.97 79.85 81.13 48.97 51.10 9.49 7.78

Lactation ration2 100.00 64.37 ― 11.52 ― 48.05 27.16 8.59

1Ewes were fed fescue straw in each year to limit metabolizable protein

intake. 2Ewes were fed a common ration during lactation across all dietary treatments: 28.5% oats, 28.5% haylage, 43% chopped hay. 3NE = (0.029 × TDN) − 0.29. m

starting dietary treatments. Ewes were weighed on 2 consecutive days (d 99 and 100 of gestation) prior to the initiation of treatments. On d 100 ± 8 (SD) of gestation, using the average of the initial weights (d 99 and 100 of gestation), ewes were stratified by BW, BCS, age, and expected lambing date to 1 of 3 dietary treatments similar in total energy but varying in MP levels (Table 2; n = 7 pens/treatment): 60MP1, 60% of MP requirements; 80MP1, 80% of MP requirements; and 100MP1, 100% of the MP requirements on a DM basis during late gestation of a ewe carrying twins (NRC, 2007). On d 100 ± 8 (SD), treatments were initiated. Daily supplement intake was determined using the average BW of the pen and offered once daily at 0800 h. Daily DMI was determined by the NRC (2007). Ewes were given 1 h to consume the supplement, and the supplement was always consumed within the hour. After supplement consumption, ewes were offered access to the low-quality forage based upon the average ewe BW for each pen so that the predicted MP intake would be achieved. All forage offered was consumed on a daily basis. Body weights were collected every 14 d throughout the dietary treatment period (d 114, 128, and 142), and the amount of supplement offered was adjusted due to changes in average BW per pen. A mineral supplement was provided once per wk to allow for 8.5 g∙ewe-1∙d-1 consumption (Table 2). Once ewes had lambed, the ewes and lambs were moved to grouping pens and were intermingled between dietary treatments where they were maintained on a lactation ration (Table 1), which was formulated to meet or exceed nutritional requirements until weaning. Year 2. On d 34, multiparous western-whiteface ewes were moved to and maintained in a common group pasture at the Hettinger Research Extension Center and exposed to Rambouillet rams. Upon pregnancy confirmation via ultrasonography at d 75, pregnant ewes

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Table 2. Ingredients and nutrient composition of dietary supplements fed to ewes in yr 1 and 2

Table 3. Ingredients and nutrient composition of diets fed to ewe lambs in yr 1 and 2

Year 11 Item 60MP1 80MP1 100MP1 Ingredient, % DM Corn 18.50 15.00 5.00 DDGS3 7.00 20.00 30.00 Soyhulls 9.50 — — Trace mineral4 0.49 0.49 0.49 Nutrient composition DM, % 88.75 89.34 89.68 NEm, Mcal/kg 2.00 2.22 2.14 CP, % of DM 13.16 20.21 25.13 MP, % of DM 8.41 13.01 16.31 NDF, % of DM 31.03 30.73 39.79 ADF, % of DM 15.69 7.45 10.49 Ash, % of DM 3.22 3.48 4.55

Item Ingredient Oats, % Whole, shelled corn, % Market lamb pellet,1 % Nutrient composition DM, % CP, % of DM NDF, % of DM ADF, % of DM Ash, % of DM

Year 22 60MP2 100MP2 140MP2 30.00 4.00 9.00 0.49

19.00 24.00 — 0.49

— 43.00 — 0.49

88.64 2.05 10.21 6.54 29.64 13.87 3.53

90.19 2.19 18.67 11.96 31.40 8.68 3.80

92.16 2.06 28.68 18.37 45.34 13.34 5.13

1Maternal

diets (DM basis) were balanced for mature ewes carrying twins during late gestation according to NRC (2007). Treatments: 60MP1, 60% of MP requirements; 80MP1, 80% of MP requirements; and 100MP1, 100% of MP requirements. 2Maternal diets (DM basis) were balanced for mature ewes carrying twins during late gestation according to NRC (2007). Treatments: 60MP2, 60% of MP requirements; 100MP2, 100% of MP requirements; and 140MP2, 140% of MP requirements. 3DDGS = dried distillers grains with solubles. 4Mineral supplement: 16.0%–17.0% Ca as CaH P O , CaHPO , and 4 2 8 4 CaCO3; 8.0% P as CaH4P2O8 and CaHPO4; 21.0%–23.0% NaCl; 2.75% Mg; 3 mg/kg Co as CoCO3; 5 mg/kg Cu; 100 mg/kg I as C2H10I2N2; 1,400 mg/kg Mn as MnSO4; 20 mg/kg Se as Na2O3Se; 3,000 mg/kg Zn as ZnSO4; 113,500 IU/kg vitamin A; 11,350 IU/kg vitamin D; and 227 IU/kg vitamin E.

(n = 169) were selected, and on d 90 of gestation, ewes were weighed, stratified by BW, and placed in a total confinement barn (14 ewes/pen), and acclimated to a low-quality straw (Table 1) and the 100MP2 supplement (100% of the MP requirements) for 7 d prior to starting dietary treatments. On d 100 ± 8 (SD) of gestation, using the average of the initial weights (d 99 and 100 of gestation), ewes were stratified to 1 of 3 dietary treatments that were similar in total energy but different in MP levels (Table 2; n = 4 pens/treatment): 60MP2, 60% of MP requirements; 100MP2, 100% of the MP requirements; and 140MP2, 140% of MP requirements on a DM basis of a ewe carrying twins during late gestation (NRC, 2007). Dietary treatment application and lambing procedures were similar to yr 1. Lambs In both yr, lambs were weighed and tagged within 24 h of birth; gender, lambing assistance, and lamb vigor (0 = extremely active and vigorous, 4 = very weak and little movement; Matheson et al., 2011) were recorded. Lambs were moved with the ewes to grouping pens and had ad libitum access to creep pellet (crude fat: 2%, crude fiber: 15%; Ca: 1.5%; P: 0.35%; salt: 1%; Se:

% 60.0 20.0 20.0 91.1 22.3 23.8 10.1 10.5

1Commercial

market lamb pellet contained: 0.22 g/kg chlortetracycline; 38.0% CP; 3.75%–4.75% Ca; 0.6% P; 3.0%–4.0% salt; 1.2 ppm Se; 52,863 IU/kg vitamin A; 5,286 IU/kg vitamin D; and 209 IU/kg vitamin E.

0.2 ppm; vitamin A: 1,134 IU/kg; vitamin D: 114 IU/kg; and vitamin E: 2.3 IU/kg) and water prior to weaning. At 14 d of age, all lambs were vaccinated for tetanus and Clostridium Perfringens types C and D (CD-T; Bar Vac CD-T; Boehringer Ingelhein, Ridgefield, CT), tails were docked, and ram lambs were castrated. Lambs were weaned at 69 ± 5 d (SD) of age in yr 1 and at 61 ± 12 (SD) d of age in yr 2, vaccinated again for tetanus and Clostridium perfringens types C and D (CD-T; Bar Vac CD-T; Boehringer Ingelhein, Ridgefield, CT), and weighed. Once removed from ewes, lambs were moved to feedlot pens and were comingled across maternal dietary treatments. Lamb birth weights and characteristics are published in Van Emon et al. (2014). Ewe Lambs In both yr after weaning, the first generation ewe lambs (i.e., the offspring born from ewes that received the dietary treatments; F1) were separated from wether lambs and placed into a growing pen (yr 1: n = 30 for 60MP1, n = 25 for 80MP1, and n = 36 for 100MP1; yr 2: n = 31 for 60MP2, n = 18 for 100MP2, and n = 23 for 140MP2). In both yr, F1 lambs were fed a mixed diet ad libitum via bulk feeders (Table 3). In yr 1, between 108 ± 10 (SD) and 236 ± 10 (SD) d of age, F1 weights and ADG were measured. Body weights were taken every 14 d throughout the 128-d period. Weight and ADG in yr 2 was measured from 63 ± 13 (SD) d of age to 191 ± 20 (SD) d of age. Body weights were taken at the beginning (d 0) and at the end (d 128) of the 128-d period. In yr 1, the synchronization protocol for F1 ewe lambs began at 259 ± 10 (SD) d of age. All ewe lambs were determined to be cycling by circulating progesterone concentrations of ≥ 0.4 ng/mL prior to the onset of breeding (Wright et al., 2002). First generation ewe

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lambs were stratified by maternal dietary treatment and body weight into 1 of 5 breeding groups (n = 18/breeding group) and were synchronized utilizing controlled intravaginal drug release (CIDR; Eazi-Breed CIDR; Pharmacia & Upjohn Pty Limited, Rydalmere, Australia) devices. Controlled intravaginal drug release devices were inserted on d 14. Day 0 is denoted by the day CIDR were removed. Rambouillet rams (n = 2/breeding group) were fitted with marking harnesses and were introduced to each breeding group at the first day of CIDR removal. Breeding marks were observed daily to determine the day of breeding. Breeding harness crayons were changed to a different color on d 18 and 35 d post-CIDR removal. On d 35 of the breeding season, F1 lambs were moved into one pen and comingled for the remaining 17 d. If a ewe was remarked, that was noted. Breeding data were confirmed by using lambing date and back calculating to determine if the breeding marks were accurate. If they did not match, the ewe was not included in the data set. In yr 2, F1 breeding began at 256 ± 9 (SD) d of age. All ewe lambs were determined to be cycling as progesterone concentrations were ≥ 0.4 ng/mL (Wright et al., 2002). First-generation ewe lambs were maintained in a single flock during the 51-d breeding period. Day 0 is denoted as the day of ram introduction. Rambouillet rams (n = 10) were fitted with marking harnesses and were introduced to the flock. Breeding marks were observed on d 1, 17, 18, 34, 35, and 51. Breeding harness crayons were changed to a different color on d 18 and 35 d post-CIDR removal. Rams were removed from the pen 51 d after the rams were introduced. In both yr, pregnancy was confirmed via ultrasonography (B – Mode; Aloka SSD-500V; Aloka America, Wallingford, CT) 45 d after the rams were removed. After removal of the rams, F1 ewe lambs were maintained in a single flock until lambing. Approximately 30 d prior to lambing, F1 lambs were moved to a total confinement barn and placed into 6 pens (15 F1 lambs/pen) in yr 1 and 5 pens (14 F1 lambs/pen) in yr 2. During this 30 d period prior to lambing and after lambing, F1 lambs were fed a lactation ration, which was similar to the ration provided to ewes after birth (Table 1). Lambing In both yr, lambs of F1 dams (F2) were weighed and tagged within 24 h of birth; sex, birth type, lambing difficulty, and lamb vigor were also recorded. At 14 d of age, all lambs were vaccinated for tetanus and Clostridium Perfringens types C and D (CD-T; Bar Vac CD-T; Boehringer Ingelhein, Ridgefield, CT), tails were docked, and ram lambs were castrated. From birth through weaning, lambs had ad libitum access to a lamb grower pellet (crude fat: 2%, crude fiber: 15%; Ca: 1.5%;

Table 4. Effects of maternal metabolizable protein supplementation on ewe lamb growth performance in yr 1 Maternal dietary treatment1 Item 60MP1 80MP1 100MP1 SEM2 Birth weight, kg 4.5 5.2 4.9 0.15 Weaning BW, kg 18.2 19.9 19.2 0.98 ADG, kg/d Birth to weaning 0.19 0.22 0.21 0.013 Weaning to final4 0.27 0.27 0.27 0.007 Birth to final4 0.25 0.26 0.25 0.006 Growth period5 Initial BW, kg 31.2 33.1 30.5 1.83 Final BW, kg 63.3 66.6 63.1 1.67 ADG, kg/d 0.25 0.26 0.25 0.008

Orthogonal contrasts3 Linear Quadratic 0.09 0.01 0.41 0.28 0.36 0.55 0.86

0.26 0.74 0.20

0.75 0.93 0.74

0.31 0.08 0.55

1Maternal diets (DM basis) were balanced for mature ewes carrying twins during late gestation according to NRC (2007). Treatments: 60MP1, 60% of MP requirements; 80MP1, 80% of MP requirements; and 100MP1, 100% of MP requirements. 2Greatest

SEM presented (n = 30 for 60MP1, n = 25 for 80MP1, and n = 36 for 100MP1). 3P-value for linear and quadratic effects of increasing metabolizable protein concentrations. 4Weaning to final indicates the ADG from weaning to the final BW measured on d 128 of the 128 d growth period. Birth to final indicates the ADG from birth to the final BW measured on d 128 of the 128-d growth period. 5Growth period that was 128 d in length to measure growth performance of the ewe lambs.

P: 0.35%; salt: 1%; Se: 0.2 ppm; vitamin A: 1134 IU/kg; vitamin D: 114 IU/kg; and vitamin E: 2.3 IU/kg). Statistical Analyses In both yr, F1 growth and performance from birth to breeding and birth weights of F2 were analyzed using the MIXED procedure of SAS (SAS Inst. Inc., Cary, NC). The model included the main effects of maternal dietary treatment, birth type (singleton or twin), and the interaction. Pen served as the experimental unit, thus the random statement included pen nested within treatment. The GLIMMIX procedure of SAS was used to analyze the percentage of F1 breeding in the first 17 d of the breeding season and the percentage of F1 lambing in each 17-d period of the breeding season. If the interaction was not significant (P > 0.20), the interaction was removed from the model. Preplanned comparisons of linear and quadratic contrasts were utilized to partition treatment effects. Significance was set at P ≤ 0.10. RESULTS Growth Performance In yr 1, there was a quadratic response (P = 0.01) for ewe lamb birth weight, where 80MP1 ewe lambs

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Table 5. Effects of maternal metabolizable protein supplementation on ewe lamb growth performance in yr 2

Item Birth weight, kg Weaning BW, kg Final BW,4 kg ADG, kg/d Birth to weaning Weaning to final5 Birth to final5

Maternal dietary treatment1 60MP2 100MP2 140MP2 SEM2 4.5 4.5 4.7 0.21 14.7 17.0 16.1 0.93 59.5 63.1 57.2 2.16 0.18 0.23 0.22

0.20 0.25 0.23

0.16 0.23 0.21

0.01 0.01 0.01

Orthogonal contrasts3 Linear Quadratic 0.43 0.52 0.27 0.17 0.37 0.07 0.31 0.79 0.55

0.03 0.23 0.07

1Maternal diets (DM basis) were balanced for mature ewes carrying twins during late gestation according to NRC (2007). Treatments: 60MP2: 60MP2, 60% of MP requirements; 100MP2, 100% of MP requirements; and 140MP1, 140% of MP requirements. 2Greatest SEM presented (n = 31 for 60MP2, n = 18 for 100MP2, and n = 23 for 140MP2). 3P-value for linear and quadratic effects of increasing metabolizable protein concentrations. 4Final

BW observed at the end of the 128-d growth period beginning at weaning. 5Weaning to final indicates the ADG from weaning to the final BW measured on d 128 of the 128-d growth period. Birth to final indicates the ADG from birth to the final BW measured on d 128 of the 128-d growth period.

were heavier at birth than 100MP1 and 60MP1 ewe lambs (Table 4). Additionally, there was a quadratic response (P = 0.08) for ewe lamb final BW during the 128-d growth period, where 80MP1 ewe lambs were heavier at the end of the growth period than the 60MP1 and 100MP1 ewe lambs. Otherwise, there was no impact (P ≥ 0.20) of maternal MP on any growth parameter measured (Table 4). Regardless of maternal dietary treatment, singletons were heavier (5.3 ± 0.1 kg vs. 4.4 ± 0.1 kg; P < 0.001) at birth than twins. In yr 2, ewe lambs from the 100MP2 ewes had increased (P = 0.03) ADG from birth to weaning compared with the ewe lambs from the 60MP2 and 140MP2 ewes. There was a quadratic response for final BW of the growth period (P = 0.07), where 100MP2 ewe lambs were heavier at the end of the growth period than the 140MP2 and 60MP2 ewe lambs. There was also a quadratic tendency (P = 0.07) for 100MP2 ewe lambs to have increased ADG from birth to the end of the growth period than the 60MP2 and 140MP2 ewe lambs. There was no effect (P ≥ 0.17; Table 5) of maternal MP intake on ewe lamb birth weight and ADG from weaning to the end of the growth period. Singleton lambs at weaning were heavier (17.1 ± 0.6 vs. 14.6 ± 0.5 kg; P = 0.002) than twin lambs regardless of maternal MP treatment. Average daily gain from birth to weaning, during the growth period, and birth to the end of the growth period was greater (P ≤ 0.05) in singletons than twins (data not shown).

Table 6. Effects of maternal metabolizable protein supplementation on ewe lamb reproductive performance in yr 1 Maternal dietary treatment1 60MP1 80MP1 100MP1 SEM2 50 84 67 9.3

Orthogonal contrasts3 Linear Quadratic 0.15 0.02

Item Breeding in first 17 d,4 % Total lambing,5 % 70 68 67 9.5 0.78 0.98 Lambing to first 0 0 32 9.2 0.02 0.16 17 d,6 % Lambing to sec87 62 51 12.6 0.04 0.63 ond 17 d,6 % Lambing to third 13 38 16 11.0 0.83 0.09 17 d,6 % Lambing rate,7 % 73 80 81 12 0.64 0.83 Twin rate,8 % 4.8 17.7 20.8 8.6 0.13 0.63 Lamb birth 4.8 4.8 4.7 0.20 0.64 0.78 weight, kg 1Maternal diets (DM basis) were balanced for mature ewes carrying twins during late gestation according to NRC (2007). Treatments: 60MP1, 60% of MP requirements; 80MP1, 80% of MP requirements; and 100MP1, 100% of MP requirements. 2Greatest SEM presented (n = 30 for 60MP1, n = 25 for 80MP1, and n = 36 for 100MP1). 3P-value for linear and quadratic effects of increasing metabolizable protein concentrations. 4Percentage of ewe lambs per treatment having breeding marks in the first 17 d of the breeding season. 5Total percentage of ewe lambs lambing per ewe lamb exposed per maternal dietary treatment. 6Percentage of ewe lambs lambing that were bred during the first 17 d post-ram turnout, the second 17 d post-ram turnout, or the third 17 d post-ram turnout. 7Lambing rate: number of lambs born per ewe exposed to the rams. 8Twin rate: percentage of twins born in each dietary treatment.

Reproductive Performance In yr 1, the total percentage of F1 lambing, lambing rate, twinning rate, and F2 birth weight were not altered (P ≥ 0.13; Table 6) by ewe MP intake. Ewe lambs from 80MP1 ewes exhibited an increased (P = 0.02) percentage breeding during the first 17-d breeding cycle and had an increased (P = 0.09) percentage lambing to the third 17-d breeding cycle compared with ewe lambs from 60MP1 and 100MP1 ewes. There was a linear increase (P = 0.02) in the percentage of F1 lambing to the first 17-d breeding cycle as ewe MP intake increased and a linear decrease (P = 0.04) in the percentage of F1 lambing to the second 17-d breeding cycle as ewe MP intake increased. Singleton lambs born to F1 were heavier (5.2 ± 0.1 vs. 4.3 ± 0.3; P < 0.001) at birth than twin lambs regardless of grand-dam dietary treatment. However, there was no effect (P = 0.29) of maternal MP intake on the percentage of twins born to F1. In yr 2, the ewe lambs from 100MP2 had an increased (P = 0.09; Table 7) percentage breeding during the first 17-d breeding cycle compared with the ewe


Table 7. Effects of maternal metabolizable protein supplementation on ewe lamb reproductive performance in year 2

Item Breeding in first 17 d,4 % Total lambing,5 % Lambing to first 17 d,6 % Lambing to second 17 d,6 % Lambing rate,7 % Twin rate,8 % Lamb birth weight, kg

Maternal dietary treatment1 60MP2 100MP2 140MP2 SEM2 84 94 70 9.0

Orthogonal contrasts3 Linear Quadratic 0.18 0.09

19 86

28 84

26 79

10.2 18.4

0.57 0.77

0.67 0.96

14

16

21

18.4

0.77

0.96

23 16.7 4.7

33 14.3 4.9

26 0 3.6

12 13.3 0.44

0.80 0.39 0.06

0.52 0.71 0.15

1Maternal diets (DM basis) were balanced for mature ewes carrying twins during late gestation according to NRC (2007). Treatments: 60MP2: 60MP2, 60% of MP requirements; 100MP2, 100% of MP requirements; and 140MP1, 140% of MP requirements. 2Greatest SEM presented (n = 31 for 60MP2, n = 18 for 100MP2, and n = 23 for 140MP2). 3P-value for linear and quadratic effects of increasing metabolizable protein concentrations. 4Percentage of ewe lambs per treatment having breeding marks in the first 17 d of the breeding season. 5Total percentage of ewe lambs lambing per ewe lamb exposed per maternal dietary treatment. 6Percentage of ewe lambs lambing that were bred during the first 17 d post-ram turnout and the second 17 d post-ram turnout. 7Lambing rate: number of lambs born per ewe exposed to rams. 8Twin rate: percentage of twins born in each dietary treatment.

lambs from 60MP2 and 140MP2 ewes. There was a linear decrease (P = 0.06) in F2 birth weight as MP intake increased. There was no effect (P ≥ 0.39) of maternal MP intake on total percentage of F1 lambing, F1 lambing to the first 17-d and second 17-d breeding cycles, the percentage lambing rate, and percentage twinning rate in yr 2. DISCUSSION Growth Performance Our results suggest that restricting MP intake to 60% of requirements to ewes during late gestation may negatively impact F1 offspring growth, beginning with F1 birth weights, while overfeeding MP does not positively affect these traits. Reports on birth weights of lambs from protein supplemented ewes varies, with birth weights of lambs from supplemented ewes either being similar to controls (Annett et al., 2008; Van Emon et al., 2014) or greater (Ocak et al., 2005). Others have reported that feeding a greater CP diet in late-gestation ewes results in heavier lambs at weaning and greater ADG than

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lambs from control ewes (Hatfield et al., 1995), while others report no difference in weaning weights (Ocak et al., 2005; Van Emon et al., 2014). It should be noted, however, that these studies did not look specifically at female offspring. In beef cattle, Funston et al. (2010) reported that heifer progeny birth weights were not affected when their dams were provided supplemental protein during the last third of gestation. However, these same researchers reported that heifer growth and development postbirth may be improved by maternal CP supplementation during late gestation, as they observed an increase in adjusted 205-d BW, prebreeding BW, and BW at pregnancy diagnosis in heifers born to cows that were supplemented with CP during late gestation (Martin et al., 2007). Although birth weight was not affected, heifer weaning weight was increased in those born to cows supplemented with CP during late gestation (Funston et al., 2010). The closest comparison to the current studies utilizing sheep is by Amanlou et al. (2011), who evaluated MP provided at the requirement and at 2 levels above the requirement for ewes during the last one-third of gestation. Amanlou et al. (2011) reported no differences in weaning weights of F1 ewe lambs when their dams were provided MP above their maintenance requirement. Additionally, McNeill et al. (1997) reported that increasing the dietary CP level fed to ewes in late gestation did not result in a linear increase in lamb birth weight. In the results of McNeill et al. (1997), the “medium” and “high” CP supplemented ewes had offspring of similar weight, with “low” CP supplemented ewes birthing lambs of reduced birth weight. In yr 1 of our study, ewe lambs from ewes fed 80% of MP requirements were heavier at birth and tended to be heavier at the end of our growth period. In yr 2, ewe lambs from 100MP2 ewes tended to have an increased final BW, which may have been due to their greater ADG compared with the other treatments. The lack of differences in weaning weights in yr 1 may have been due to the smaller difference in MP intake in our treatment groups compared with dietary treatments in yr 2. Similar to our results in yr 2, heifers from cows supplemented with CP during late gestation tended to have increased BW upon evaluating feed efficiency, but these heifers did not experience increased growth during the feeding trial (Funston et al., 2010). However, Martin et al. (2007) did not observe any differences during a heifer growth trial due to maternal CP supplementation during late gestation. Unlike Martin et al. (2007), we observed growth to be impacted by maternal protein supplementation. Although weaning weights and ADG from birth to weaning were improved in ewe lambs by feeding 100% of MP requirements to dams, overall performance in the growth period was not positively enhanced. Perhaps the results in yr 2 could be explained by the interpretation of McNeill et al. (1997) where enhanced protein supple-

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mentation may result in a poorer ability of the placenta to transfer excess AA to the fetus, as well as the high energetic cost of detoxifying excess ammonia for gluconeogenesis from the excess AA. Similar to the results in yr 2 in the current study, at 21 and 70 d of age, female rat pups from dams fed a diet that was composed of 20% casein during gestation were heavier than females born from rats fed an isocaloric diet that contained 10% casein (Guzmán et al., 2006). However, by 22 mo of age, female offspring BW was no longer affected by maternal protein levels during gestation (Guzmán et al., 2006). This suggests that despite the fact that protein restriction during gestation reduces female offspring BW early in life, progeny may experience compensatory growth by mechanisms unknown and be similar in BW later in life. Reproductive Performance Much of the research available on the ability of female offspring to achieve pregnancy and deliver healthy offspring has been conducted by restricting energy or total nutrients, and to our knowledge, there has been no research conducted evaluating MP intake during gestation in ruminants. When ewes were restricted to 50% of ME requirements, female offspring ovarian development was altered (Rae et al., 2001). A reduction in mature follicles in the ovaries could lead to reduced reproductive performance in those offspring throughout life. Our diets were isocaloric, so further research is needed to see if protein is an important consideration of ovarian development that may have been responsible for the altered female offspring reproductive efficiency we observed. Protein supplementation in late gestation can provide both a protein and energy source for the dam. When ruminants are provided excess protein in late gestation, blood glucose concentrations have been reported to increase in ewes (Amanlou et al., 2011). Although glucose is the primary source of energy for the uterus and fetus, it is unknown in the current study if providing excess MP altered glucose concentrations in the offspring. However, when maternal energy is restricted during early to midgestation and there is no influence on birth weight or growth performance, there is also no impact on female offspring conception rates, litter size, or litter weight at birth (Muñoz et al., 2009). Perhaps it is the postnatal growth trajectory of the female offspring that programs their reproductive efficiency. Maternal protein nutrition during late gestation can also alter female offspring reproductive performance. Although not measured in the current studies (we only determined that all ewe lambs were cycling at the beginning of the breeding season), Funston et al. (2010) observed that heifers from cows supplemented with CP during late

gestation tended to reach puberty at a younger age than those born to unsupplemented cows. Improved pubertal status could lead to improved reproduction performance during the breeding season, mainly through decreased time to first estrus and increase in conception rates during the first estrous cycle. Further evidence that protein levels during gestation may be important for offspring reproductive performance was observed by Guzmán et al. (2006). Female rat pups from dams that were CP restricted during both gestation and lactation, or just lactation, were lighter and older at puberty, than female rat pups from adequately fed dams. These data indicated that providing adequate protein during gestation and lactation is crucial to maintaining ovarian growth, which could potentially impact female offspring reproductive efficiency. However, as the female offspring aged from birth to 22 mo, the impacts of their maternal diet on BW and uterine weights became negligible (Guzmán et al., 2006). From the results of the current study, it appears that supplementation increases reproductive performance of female offspring, as F1 progeny reproductive performance was affected. While our results report an increase in breeding activity, as denoted by breeding marks in 80 and 100MP1 progeny during the first 17 d of exposure to rams, the ewe lamb progeny in both studies did not have differing pregnancy rates or lambing rates following the third and second thirds of pregnancy for yr 1 and 2, respectively, indicating that overall reproductive performance was not altered. However, it does appear that while the progeny were cycling at the first exposure to rams, embryonic death loss following the first 17 d of breeding may have played a role in minimizing potential positive effects of maternal MP supply on early pregnancy in F1 offspring (yr 1 had an increase in breeding in the first 17 d of pregnancy for 80MP1 F1 offspring). The largest effect on reproduction in our study occurred in yr 1where the 100MP1 offspring had more F1 progeny lambing early in their lambing season. These results indicated that feeding 100% of the MP requirements in late pregnancy will benefit subsequent F1 ewe lamb reproductive performance. In yr 2, lambing rates of the F1 progeny were drastically low, which was due to early term abortions caused by vibriosis. After necropsy verification of the virbiosis, all ewe lambs were treated via veterinary recommendations. As indicated in the results from yr 2, feeding MP above requirements for ewes in late pregnancy appears to have no beneficial effect on subsequent ewe lamb reproductive performance. Alterations in puberty and reproductive organ weights may also impact female offspring breeding and conception rates. Heifers born to cows supplemented with CP during late gestation had increased pregnancy rates and percentage of heifers calving in the first 21 d compared with heifers born to cows that were not sup-


plemented during late gestation (Martin et al., 2007). In our study, F1 ewe lambs from ewes fed 80MP1 had increased percentage of lambs breeding in the first 17 d; however, this did not increase lambing during the first 17 d, possibly due to fetal death loss. The majority of F1 ewe lambs from 80MP1 lambed during the second 17-d post-ram turnout, indicating that although more F1 had breeding marks, pregnancy was not maintained in all of them. Although breeding was reduced in the F1 from 100MP1 ewes in the first 17-d post-ram turnout, providing 100% of MP requirements may have programmed female offspring to have increased embryonic survival. Implications To our knowledge, there has been no research conducted on the effects of MP intake during gestation on female offspring growth and reproductive efficiency. The data from the current study suggest that feeding 80% to 100% of MP requirements during late gestation may have the greatest positive impacts on female reproductive performance through conceiving in the first 17 d of breeding. However, feeding MP to ewes in late gestation above requirements did not result in growth or reproductive performance gains, indicating supplying excess protein had no beneficial effect on ewe lamb birth weight or postnatal growth and ability to become pregnant. LITERATURE CITED Amanlou, H., A. Karimi, E. Mahjoubi, and C. Milis. 2011. Effects of supplementation with digestible undegradable protein in late pregnancy on ewe colostrums production and lamb output to weaning. J. Anim. Physiol. Anim. Nutr. 95:616–622. Annett, R. W., A. F. Carson, and L. E. R. Dawson. 2008. Effects of digestible undegradable protein (DUP) supply and fish oil supplementation of ewes during late pregnancy on colostrum production and lamb output. Anim. Feed Sci. Technol. 146:270–288. Evans, A. C. O., F. Mossa, S. W. Walsh, D. Scheetz, F. JimenezKrassel, J. L. H. Ireland, G.W. Smith, and J. J. Ireland. 2012. Effects of maternal environment during gestation on ovarian folliculogenesis and consequences for fertility in bovine offspring. Reprod. Domest. Anim. 47:31–37. Funston, R. N., J. L. Martin, D. C. Adams, and D. M. Larson. 2010. Winter grazing system and supplementation of beef cows during late gestation influence heifer progeny. J. Anim. Sci. 88:4094–4101. Grazul-Bilska, A. T., J. S. Caton, W. Arndt, K. Burchill, C. Thorson, E. Boroczyk, J. J. Bilski, D. A. Redmer, L. P. Reynolds, and K. A. Vonnahme. 2009. Cellular proliferation and vascularization in ovine fetal ovaries: effects of undernutrition and selenium in maternal diet. Reproduction 137:699–707.

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