C. M. C. Jenkinson

Effects of ewe size and nutrition on fetal mammary gland development and lactational performance of offspring at their first lactation

Many environmental factors applied postnatally are known to affect milk production of the dam, but to date, the effects of different fetal environments on subsequent first lactational performance of the offspring have not been reported. Four hundred fifty heavy (H; 60.8 kg +/- 0.18) and 450 light (L; 42.5 kg +/- 0.17) dams were randomly allocated to ad libitum (A) or maintenance (M) nutritional regimens from d 21 until d 140 of pregnancy, under pastoral grazing conditions (HA, n = 151; HM, n = 153; LA, n = 155; LM, n = 153). At d 100 of pregnancy, a sub-group of twin-bearing dams was killed and fetal mammary glands collected. From 1 wk before lambing, all remaining dams were fed ad libitum until weaning. After weaning, female progeny were managed and fed under pastoral conditions as 1 group. At 2 yr of age, 72 twin-rearing ewe offspring were milked once a week for 7 wk. Fetuses from M-dams had heavier mammary glands (P = 0.03) compared with A-fetuses. Fetuses from H-dams had greater (P = 0.0008) mammary duct area compared with L-fetuses. At 2 yr of age, M-offspring had greater milk yields at d 7 (P = 0.02) and d 28 (P = 0.09) of lactation and tended to have greater accumulated milk yields (P = 0.11) compared with A-offspring. Ewes born to M-dams showed greater lactose percentage at d 14 (P = 0.002), d 21 (P = 0.06), and d 28 (P = 0.07) of lactation and greater (P = 0.049) accumulated lactose yields and CP (P = 0.06) yields compared with A-offspring. Ewes born to H-dams displayed greater milk yields at d 14 (P = 0.08) and d 21 (P = 0.02) and had greater accumulated milk yield (P = 0.08) and lactose yield (P = 0.04) compared with L-offspring. Lambs born to M-offspring were heavier at birth (P = 0.02) and grew faster until weaning (P = 0.02), matching the milk yield and composition data, compared with their ad libitum counterparts. Birth weight was not affected (P > 0.10) by grand dam size; however, lambs born to H-offspring grew faster from birth until d 49 of age (P = 0.03). In conclusion, dam nutrition during pregnancy affected the resulting milk production of the offspring and composition and growth of their lambs. In addition, dam size affected the milk production of the offspring, lactose yield, and growth of their lambs. These findings are important for furthering our understanding of how the environment to which the female fetus is exposed can affect her subsequent development and her ability to nourish the next generation.

Dam and granddam feeding during pregnancy in sheep affects milk supply in offspring and reproductive performance in grand-offspring1

In temperate climates, the cost of providing feed is greater in winter than in other seasons, causing ewes to be fed restricted rations during some periods of pregnancy. Epidemiological information indicates that undernutrition of the fetus may affect its health and performance in later life (i.e., fetal programming), and these effects may be passed between generations. The primary focus of the results presented in this paper is to examine the effects of feeding levels during pregnancy on a variety of traits from offspring at the fetal stage to 3.5 yr of age and also traits in the grand-offspring. Two studies are reported in which ewes were fed restricted diets during pregnancy, with a variety of fetal traits, offspring traits up to 3.5 yr of age, or grand-offspring traits up to 8 mo of age being measured. Study 2 also considered differences in dam size (heavy vs. light). In study 1, several fetal mammary gland measures indicated that milking ability may be enhanced in offspring from dams fed ad libitum during pregnancy. However, study 2 showed that mammary mass was greater in fetuses from dams fed at maintenance during pregnancy and that contemporaries of these fetuses produced greater protein and lactose yields in their first lactation. In the second lactation, the advantages in protein and lactose yields did not reoccur and ewes from ad libitum-fed dams produced greater fat yield. In study 2, grand-offspring whose granddams were fed at maintenance levels during pregnancy were lighter at birth in both the first and second parturitions than those whose granddams were fed ad libitum during pregnancy. First-parity grand-offspring whose granddams were fed maintenance levels during pregnancy achieved heavier BW by 40 to 50 d of age in the first lactation, which reflected the greater protein and lactose yields; however, no BW differences were present in second-parity lambs at the same age. A smaller proportion of first-parity ewe grand-offspring from heavy granddams that were fed ad libitum during pregnancy reached puberty at approximately 8 mo of age relative to the other granddam size and feeding groups. These results indicate that dam nutrition can affect the yield and composition of milk in their offspring and the BW and reproductive capability of their grand-offspring. Molecular and physiological mechanisms for these changes are being sought.

The effect of ewe size and nutritional regimen beginning in early pregnancy on ewe and lamb performance to weaning

Abstract Ewe size, pregnancy nutrition and pregnancy rank are known to affect the productive performance of ewes and their offspring. The aim of the present study was to compare the effects of two nutritional regimens, from day 21 to day 140 of pregnancy, in singleton‐ and twin‐bearing ewes of two different mean weights, taken from a single flock. The study included Large ewes offered Ad lib (Large‐Ad lib, n= 151), Large ewes offered Maintenance (Large‐Maintenance, n = 153), Small ewes offered Ad lib (Small‐Ad lib, n = 155) and Small ewes offered Maintenance (Small‐Maintenance, n = 153) that were either singleton‐ or twin‐bearing. During the period day 21 to day 140 Maintenance and Ad lib feeding regimens included Large and Small ewes and singleton‐ and twin‐bearing ewes. At days 1 and 140 of pregnancy Large ewes were heavier (P < 0.05) and of greater (P < 0.05) body condition than Small ewes. Similarly, at days 1 and 140 of pregnancy twin‐bearing ewes were heavier (P < 0.05) than single‐bearing ewes. At day 1 of pregnancy there was no difference in ewe liveweight and body condition scores between Maintenance and Ad lib‐fed ewes, but by day 140 ewes in the Ad lib regimen were heavier (P < 0.05) and had greater (P < 0.05) body condition than Maintenance ewes. There was an interaction (P < 0.05) between ewe nutritional regimen and lamb birth rank for lamb birth weight such that twin lambs born to Maintenance regimen ewes were lighter (P < 0.05) than their counterparts born to Ad lib ewes (4.52 ± 0.06 versus 5.23 ± 0.06 kg respectively). This relationship was not observed in singletons. There was also an interaction (P < 0.05) between ewe size and nutritional regimen for lamb birthweight. Birth weights did not differ between lambs born to either Small or Large ewes on the Ad lib feeding regimen. However, lambs born to Small ewes on the Maintenance feeding regimen were lighter (P < 0.05) than their counterparts born to Large ewes (5.09 ± 0.07 versus 5.37 ± 0.07 kg respectively). At day 100 of lactation lambs born to Large ewes were heavier (P < 0.05) than those born to Small ewes (32.65 ± 0.37 versus 31.16 ± 0.35 kg respectively) and those born to Ad lib ewes were heavier (P < 0.05) than those born to Maintenance ewes (32.77 ± 0.37 versus 31.03 ± 0.36 kg respectively). This study shows that level of dam pregnancy nutrition has a greater effect on twin‐born lambs than their singleton‐born counterparts. Furthermore, the data suggests that the heavier liveweights at weaning of lambs born to Large ewes may not have compensated for their dams’ greater nutritional requirements compared to their smaller counterparts.

Seasonal effects on birth weight in sheep are associated with changes in placental development

Abstract Lambs born in the autumn or winter have substantially lower birth weights than those born in the spring, but the physiological basis of this difference is unknown. This study examined the effects of season on foetal growth and placental development in ewes managed under controlled grazing to minimise the confounding effects of maternal liveweight change. Mature Romney ewes pregnant to matings in December (n = 13) or March (n ‐ 13), with similar liveweights at mating, were managed to achieve similar liveweights at Day 140 of gestation. At that time, measures of foetal growth and placental development, adjusted for litter size, were (December‐ versus March‐mated): foetal weight (4.15 ± 0.16 versus 5.07 ± 0.16 kg, P 0.10); placentome number (89.4 ± 4.2 versus 106.9 ± 4.3, P < 0.01); number of placentomes per number of caruncles (0.79 + 0.03 versus 0.88 ± 0.03, P < ...

Uterine environment as a regulator of birth weight and body dimensions of newborn lambs.

Pure-bred embryos were transferred within and reciprocally between large (Suffolk) and small (Cheviot) breeds of sheep to establish 4 treatment groups: SinS (Suffolk embryos in Suffolk dams), SinC (Suffolk embryos in Cheviot dams), CinS (Cheviot embryos in Suffolk dams), and CinC (Cheviot embryos in Cheviot dams). The recipient ewes carried single fetuses to term. The maternal plasma concentrations of ovine placental lactogen (oPL), progesterone, IGF-1, FFA, and glucose were measured on d 50, 90, 120, and 140 of pregnancy. Birth weight, body dimensions, and placental characteristics of lambs were recorded at birth. There was a recipient ewe breed × lamb breed × time interaction for the concentration of oPL (P = 0.03), but no such interaction was observed for progesterone (P = 0.42), IGF-1 (P = 0.57), glucose (P = 0.36), or FFA (P = 0.72). There were no differences in oPL (P = 0.28) and progesterone (P = 0.34) concentrations between SinC and SinS ewes. The concentrations of FFA on d 140 (P = 0.008), and those of glucose on d 50 (P = 0.02) and 120 (P = 0.01), were greater in SinC ewes than in SinS ewes. The ewes in CinS had less FFA concentration (P = 0.002) at all time points than CinC ewes. The concentrations of IGF-1 on d 90 were greater (P = 0.004) in CinS ewes than CinC ewes, but did not differ (P = 0.16) on d 50, 120, and 140. The concentrations of glucose on d 50 (P = 0.001), 90 (P = 0.03), and 140 (P = 0.03) were less in CinS ewes compared with CinC ewes. The birth weight of SinC lambs (5.04 ± 0.20 kg) was lighter (P = 0.001) than SinS lambs (5.94 ± 0.19 kg), and body dimensions of SinC lambs were smaller (P = 0.01) than SinS lambs. Neither birth weight nor the body dimensions of CinS lambs differed (P = 0.24) from CinC lambs. Cotyledon number was reduced (P = 0.04) in the CinS (57.5 ± 6.3) compared with the SinS group (74.2 ± 5.9), whereas mean cotyledon weight in CinS (2.42 ± 0.20 g) was greater (P = 0.02) than SinS (1.74 ± 0.21 g). It was concluded that the large genotype lambs were lighter and smaller when born to small genotype dams; however, the birth weight or body dimensions of small genotype lambs did not differ when born to large genotype dams. This study suggests that plasma oPL, progesterone, IGF-1, FFA, and glucose concentrations at different times throughout pregnancy reflect the regulatory effect of the uterine environment on the development of the fetus.

Effects of twin-bearing ewe nutritional treatments on ewe and lamb performance to weaning

Nutrition of the ewe at various stages of pregnancy is known to affect ewe and offspring performance. However, little is known regarding the potential interactions among differing maternal nutrition regimens in early and mid–late pregnancy. The objective of the present study was to examine the effects and potential interactions of three pastoral nutritional treatments from Day 21 of pregnancy (P21) to P50 (Sub-maintenanceP21–50 (total liveweight change achieved, SMP21-50, –0.15 ± 0.02 kg/day) v. MaintenanceP21–50 (MP21-50,–0.02 ± 0.02 kg/day) v. Ad libitumP21–50 (AdP21-50,0.15 ± 0.02 kg/day) and two pastoral nutritional treatments from P50 to P139 [MaintenanceP50–139 (designed to match change in conceptus mass, total liveweight change achieved, 0.19 ± 0.01 kg/day) v. Ad libitumP50–139 (0.26 ± 0.01 kg/day)] on 382 twin-bearing ewes and their offspring until 91 days after the mid-point of lambing (L91). Ewe liveweight and condition scores in pregnancy and lactation, and lamb liveweights, indices of colostrum uptake and survival were recorded. There were no interactions between nutritional periods for lamb liveweight, apparent colostrum intake and survival, and ewe liveweight, condition score and total weight of lamb per ewe at the end of the study. At L91, ewe nutritional treatment during P21–50 or P50–139 had no effect on either ewe liveweight or body condition score. Ewe nutritional treatment during P21–50 had no effect on lamb birthweight. Lambs born to AdP50–139 ewes were lighter (P 0.05) effect on indices of colostrum uptake in lambs at 24–36 h of age. At L91, ewe nutritional treatment during P21–50 or P50–139 had no effect on lamb liveweight, survival or total weight of lamb per ewe. In conclusion, although considerable differences in ewe liveweight were observed during pregnancy, the nutritional treatments had no effect on the production parameters measured at the end of the study. These results indicate, first, that farmers can use early pregnancy as a period to control ewe nutrition when ewes are offered at least pregnancy maintenance levels of nutrition in the mid–late pregnancy period and, second, that there is no advantage from offering twin-bearing ewes a level of nutrition above their pregnancy maintenance requirements in mid–late pregnancy.

LACTATION BIOLOGY SYMPOSIUM: Maternal nutrition during early and mid-to-late pregnancy: Comparative effects on milk production of twin-born ewe progeny during their first lactation1,2

Studies using sheep models indicate that the fetal mammary gland is sensitive to maternal nutrition during gestation; however, results have been inconsistent and do not identify critical feeding periods. This study aimed to clarify previous findings by partitioning the period of maternal nutritional manipulation into 2 stages: early and mid-to-late pregnancy. Sixty-six twin-born, twin-bearing ewes, born to dams that were fed either submaintenance, maintenance, or ad libitum during early pregnancy (d 21 to 50 of pregnancy; SmP21-50, MP21-50, or AdP21-50, respectively) and then either maintenance or ad libitum during mid-to-late pregnancy (d 50 to 140 of pregnancy; MP50-140 or AdP50-140, respectively) were milked once a week, starting from d 7 ± 1 postpartum, for 7 subsequent weeks to enable estimation of daily milk yield and composition. Their lambs were weighed weekly. Ewes born to dams fed MP21-50 tended to have greater accumulated milk (P = 0.10), fat (P = 0.07), and NE (P = 0.06) yields over 50 d compared with ewes born to dams fed SmP21-50 and AdP21-50. In contrast, ewes born to dams fed AdP50-140 tended to have greater accumulated milk (P = 0.10) and lactose (P = 0.09) yields compared with ewes born to dams fed MP50-140. Grandoffspring birth weights were unaffected by granddam nutrition during pregnancy. Ewes born to dams fed AdP21-50 weaned lighter lambs (P = 0.05) than ewes born to dams fed AmP21-50 and tended to wean lighter lambs (P = 0.07) than ewes born to dams fed MP21-50 whereas there were no differences between the weaning weights of lambs (P = 0.43) from ewes born to dams fed AdP50-140 and MP50-140. Maintenance nutrition of dams during early pregnancy appears to be associated with an improved lactation performance of ewe offspring. Higher levels of nutrition during mid-to-late pregnancy also appears to improve the first-lactation performance of ewe offspring. Interestingly, although grandoffspring birth weights were unaffected, weaning weight appears to be influenced by granddam early pregnancy nutrition in a manner discordant with the lactational performance of their dam. Results from this study indicate that dam nutrition during early pregnancy can influence the lactational performance of ewe offspring and the BW at weaning of their grandoffspring, which may ultimately affect farmer profits. This highlights the importance of nutritional management of breeding ewes during this period.

The bone-muscle ratio of fetal lambs is affected more by maternal nutrition during pregnancy than by maternal size

Bone formation and loss are related to the strain imposed on bone by muscle forces. Bone mineral content (BMC) and lean mass (LM) of fetal lambs was determined at day 140 of pregnancy in 8 groups of ewes, which were of either large or small body size, on either high (ad libitum) or maintenance pasture intake from day 21 of pregnancy, or carrying either singletons or twins. BMC and LM (using DXA scanning) of fetal hindquarters/spine were corrected to leg length. BMC and LM were less in twin than singleton groups (P < 0.001). Large ewes on high intake produced single fetuses with a (group mean) BMC/LM ratio that was higher (P < 0.002) than that in fetuses of large ewes with singletons on maintenance intake or twins on either high or maintenance intakes, the ratios of which were not different. In single fetuses from small ewes on high intake, the BMC/LM ratio was higher than those from small ewes with singletons on maintenance intake or twins on either high or maintenance intakes, the ratios of which were not different. The ratio was not different in singleton fetuses of ewes on high intake, whether they were large or small. Different fetal environments resulted in a given amount of muscle being associated with a higher or lower bone mass. Dietary intake during pregnancy was more important than maternal size in affecting the ratio. We conclude that intrauterine environmental factors may be important in determining bone mass postnatally, and possibly later in life.

Effects of ewe size and nutrition during pregnancy on performance of 2-year-old female offspring

The current study investigated the effects of dam weight and nutrition during gestation on the reproductive performance of female primiparous offspring at 2 years of age. Four hundred and fifty heavy (H) (mean± s.e.m .: 60·8 kg±0·18) and 450 light (L) (42·5 kg±0·17) dams were randomly allocated to ad libitum (A) or maintenance (M) nutritional regimens from day 21 until day 140 of pregnancy, under pastoral grazing conditions. One week prior to lambing, all dams and their lambs were provided with ad libitum feeding through to weaning. After weaning, female progeny were managed and fed to requirements as one group. At 2 years of age, the oestrous cycles of the female offspring ( n =207) were synchronized and the offspring were naturally mated. Ewes were scanned for pregnancy by ultrasound at day 70 of pregnancy. Within 24 h of birth, lambs were weighed and body dimensions were measured. Lambs were also weighed at day 24 (L24) and weaning. No effects of dam nutrition or dam weight were found ( P >0·10) on the reproductive performance of the ewe offspring. Lambs of M-grand-dams were heavier at birth ( P =0·024) and weaning ( P =0·031) than lambs of A-grand-dams. Twin lambs of H-grand-dams were heavier at birth ( P =0·014) than twin lambs of L-grand-dams; however, grand-dam weight had no effect ( P >0·10) on lamb weaning weight. In summary, dam weight had no effect on reproductive performance of the female offspring, with only a minor effect on the weight of grand-offspring. Thus, being born to a larger dam has no advantages over being born to a smaller dam, in terms of number of lambs born and weight of lambs at birth and weaning. Grand-dam maintenance nutrition had no effect on reproductive performance although it increased lamb birth and weaning weight and lamb growth rates of the grand-offspring. Therefore, this indicates that ewes born to dams fed at maintenance during pregnancy have an advantage over A-ewes in physiological stressful situations including pregnancy or lactation.

Ewe nutrition in early and mid- to late pregnancy has few effects on fetal development

Maternal nutrition affects fetal development, with potential lifelong consequences. The study reported here compared the anatomical development (dimensions and organs) of twin fetuses at Day 140 of gestation, from 58 twin-bearing ewes fed at one of three different nutritional treatments in early pregnancy [Day 21–50, Low (LD21–50) versus Medium (MD21–50) versus High (HD21–50)] and one of two different nutritional treatments in mid- to late pregnancy (Day 50–140, Medium (MD50–140) versus High (HD50–140)]. There were no effects (P > 0.05) of either early or mid- to late pregnancy nutrition on placental weight and fetal bodyweight or size measurements at Day 140. Semitendinosus muscles from LD21–50-HD50–140 fetuses were heavier (P < 0.05) than those from LD21–50-MD50–140 and HD21–50-HD50–140 fetuses, and fetuses from LD21–50 dams had lighter (P < 0.05) mammary glands compared with those from MD21–50 and HD21–50 dams, even after adjustment for fetal weight. Maternal nutrition also affected (P < 0.05) the weights of the fetal thyroid and brain. These results suggest that farmers can limit ewe nutrition in early pregnancy with only minor effects on the fetus. To investigate potential lifetime effects, a larger cohort of these animals is currently being monitored.