Maternal periconceptional and first trimester protein restriction in beef heifers: effects on maternal performance and early fetal growth

This study evaluated the effect of protein restriction during the periconception (PERI) and first trimester (POST) periods on maternal performance, physiology and early fetal growth. Yearling nulliparous heifers (n = 360) were individually fed a diet high or low in protein (HPeri and LPeri respectively) beginning 60 days before conception. From 24 to 98 days post-conception (dpc), half of each treatment group changed to the alternative post-conception high- or low-protein diet (HPost and LPost respectively), yielding four groups in a 2 × 2 factorial design with a common diet until parturition. Protein restriction was associated with lower bodyweight subsequent to reduced (but positive) average daily weight gain (ADG) during the PERI and POST periods. During the POST period, ADG was greater in LPeri than HPeri heifers and tended to be greater in LPost than HPost heifers during the second and third trimester. Bodyweight was similar at term. The pregnancy rate did not differ, but embryo loss between 23 and 36 dpc tended to be greater in LPeri than HPeri heifers. Overall, a greater proportion of male fetuses was detected (at 60 dpc 63.3% male vs 36.7% female). Protein restriction altered maternal plasma urea, non-esterified fatty acids, progesterone, leptin and insulin-like growth factor 1 at critical stages of fetal development. However, profiles varied depending on the sex of the conceptus.Katrina J. Copping, Andrew Hoare, I. Caroline McMillen, Raymond J. Rodgers, Charles R. Wallace and Viv E.A. Perr

Periconception and first trimester diet modifies appetite, hypothalamic gene expression, and carcass traits in bulls

Nulliparous yearling beef heifers (n=360) were used to evaluate the effects of maternal dietary protein during the periconception and first trimester periods of gestation on postnatal growth, feedlot performance, carcass characteristics, and the expression of genes associated with appetite in the arcuate nucleus of their male progeny. Heifers were individually fed a diet of 1.18g crude protein (CP)/day High protein (HPeri) or 0.62g CP/day Low protein (LPeri) beginning 60days before conception. From 24 to 98days post-conception (dpc), half of each treatment group changed to the alternative post-conception diet and were fed 1.49g CP/day (HPost) or 0.88g CP/day (LPost) yielding four treatment groups in a 2×2 factorial design. From day 98 of gestation, heifers received a common diet until parturition. Calves were weaned at 183days and developed on pasture before feedlot entry. Bulls underwent a 70-day Residual Feed Intake (RFI) feedlot test commencing at 528days of age. Feedlot entry and final body weight (BW), feedlot average daily gain (ADG) and RFI were not different (p>0.05). Progeny of dams that had a change in diet (LPeri/HPost and HPeri/LPost) had 9% higher daily dry matter intake (DMI) during the RFI test (p<0.05) than progeny of dams that received low diet throughout both the peri-conception period and first trimester (LPeri/LPost). Further, mRNA expression of the appetite-stimulating agouti-related protein (AGRP) was increased in the arcuate nucleus of High Peri/LPost bulls (p<0.05). Longissimus dorsi muscle cross sectional area, carcass dressing percentage, and estimated retail beef yield (RBY) were all higher (p<0.05), and rump (P8) fat tended to be lower (p=0.07), for bulls from HPost dams despite no difference in carcass weight (p<0.05). This study is of commercial importance to the livestock industry as specific periods of maternal dietary supplementation may increase feed intake, enhance progeny muscling, and alter fat deposition leading to improvement in efficiency of meat production in beef cattle.Katrina J. Copping, Matthew J. Callaghan, Geert H. Geesink, Jessica R. Gugusheff, I. Caroline McMillen, Raymond J. Rodgers, Beverly S. Muhlhausler, Mini A. Vithayathil and Viv E. A. Perr

Managing the nutrition of twin-bearing ewes during pregnancy using Lifetimewool recommendations increases production of twin lambs

The effect on ewe and lamb production by differential management of single- and twin-bearing Merino ewes during pregnancy and lactation was examined. The hypothesis that the survival and productivity of single- and twin-born progeny is not affected by differential management of single- and twin-bearing ewes was tested. To test this hypothesis, two ewe flocks were monitored on a commercial property in the south-east of South Australia. The body condition score of one flock of ewes was managed according to Lifetimewool recommendations for southern Australian (Lifetimewool flock; n ≤ 464). Lifetimewool recommendations are that body condition score should be 3.0 at mating and then allowed to decline to an average of 2.7, which is maintained until lambing. Twin- and single-bearing ewes were managed as separate mobs after pregnancy scanning to meet their energy requirements. The second flock was managed similarly to the commercial ewe flock and was representative of ewe management practices in the region (normal-practice flock; n ≤ 464). At lambing, the condition score of the Lifetimewool flock was 0.7 condition scores units greater than the normal-practice flock. Ewe clean fleece weight and fibre diameter were greater in the Lifetimewool flock and their lambs had higher survival rates to weaning. Over three shearings, progeny from Lifetimewool ewe flocks produced more clean wool (P 0.0001) but there was no consistent effect on fibre diameter, staple length or staple strength. Twin-born lambs from ewes managed to Lifetimewool guidelines had a similar liveweight and produced similar quantity and quality of wool to single-born lambs managed to Lifetimewool guidelines, but still suffered higher rates of mortality to weaning. This suggests that it is possible to manage ewes pregnant with twins to ensure that their surviving progeny perform at a level similar to single-born progeny managed under similar targets

The Effects of Developmental Programming upon Neonatal Mortality

KEY POINTS- The maternal environment (nutrition and physiologic status) can influence neonatal mortality and morbidity.- The effects of gestational nutrition on birth weight, dystocia, and calf survival vary with the timing and duration of dietary interventions and the sex of the offspring.- The ability to thermoregulate, stand, suckle, and ingest sufficient quantities of colostrum is critical to neonate survival and may be altered by in utero environment.- The quantity of colostral immunoglobulins ingested by the neonate may be affected by prenatal ambient temperature and gestational diet.- Gestational dietary restriction may alter thyroid function and diminish brown adipose tissue capacity concomitantly effecting lymphoid atrophy and neonatal immune function

Maternal periconceptional and first trimester protein restriction in beef heifers: effects on placental parameters and fetal and neonatal calf development

Few studies have investigated the effects of nutrition during the periconception and early gestation periods on fetal and placental development in cattle. In this study, nulliparous yearling heifers (n = 360) were individually fed a diet high or low in protein (HPeri and LPeri) beginning 60 days before conception. From 24 to 98 days after conception, half of each treatment group was changed to the alternative high- or low-protein diet (HPost and LPost) yielding four groups in a 2 × 2 factorial design. A subset of heifers (n = 46) was necropsied at 98 days after conception and fetoplacental development assessed. Placentome number and volume decreased in response to LPeri and LPost diets respectively. Absolute lung, pancreas, septum and ventricle weights decreased in LPost versus HPost fetuses, whereas the post-conception diet altered absolute and relative liver and brain weights depending on sex. Similarly, changes in fetal hepatic gene expression of factors regulating growth, glucose output and lipid metabolism were induced by protein restriction in a sex-specific manner. At term, neonatal calf and placental measures were not different. Protein restriction of heifers during the periconception and early gestation periods alters fetoplacental development and hepatic gene expression. These changes may contribute to functional consequences for progeny, but this may not be apparent from gross morphometry at birth.K. J. Copping, K. Hummitzsch, I. C. McMillen, J. L. Morrison, R. J. Rodgers and V. E. A. Perry ... et al

Divergent breeding values for fatness or residual feed intake in Angus cattle. 1. Pregnancy rates of heifers differed between fat lines and were affected by weight and fat

The pregnancy rate of heifers affects the efficiency and profitability of beef herds. Heifers extreme in rib fatness (Fat) or post-weaning residual feed intake (RFI) estimated breeding values (EBVs) were evaluated for their pregnancy rates at two locations in the southern agricultural regions of Australia (Struan and Vasse) as part of the Beef Cooperative Research Centre Maternal Productivity Project. Heifers divergent in Fat (High-Fat and Low-Fat) had differences in fat depth pre-joining at the 12/13th rib (4.4 mm vs 3.5 mm) and P8 rump site (6.1 mm vs 4.8 mm). This was associated with significant differences in pregnancy rates over a 9-week joining period (91.5% vs 83.0%) and an even larger difference when calculated over a 6-week joining period (77.3% vs 65.0%). Heifers divergent in RFI (Vasse only) also differed in rib fat (7.6 mm vs 6.4 mm) and P8 fat (11.0 vs 9.2 mm), but not significantly in pregnancy rates between the two RFI (High-RFI and Low-RFI) genotypes following a 9-week (92.4% vs 88.5%) or 6-week (81.2% vs 73.7%) joining period. The phenotypic analysis of the Fat and RFI heifers together indicated that weight and fat depth were the largest contributing factors to variation in pregnancy rates, and age and pre-joining weight gain were not significant. These phenotypic characteristics indicated that producers can manage heifers to particular weight and fat combinations to improve heifer conception rates. Associations of BREEDPLAN EBVs with heifer fertility showed that a shorter days-to-calving EBV had the biggest impact (P < 0.001) on heifer pregnancy rates and rib fat and scrotal size EBVs were close to significant (P < 0.10)

Divergent breeding values for fatness or residual feed intake in Angus cattle. 4. Fat EBVs

The productivity of 500 Angus cows, divergently selected for either rib fat or residual feed intake (RFI) based on BREEDPLAN estimated breeding values (EBVs) and managed under two levels of nutrition (stocking rates), was evaluated. The study examined the effects of genetic line, nutrition and weaning history on profiles for weight, rib fat depth, fatness (rib fat depth adjusted for weight) and supplementary feed requirements from just before the first joining as heifers through to the weaning of their third calf. Cows gained both weight and fat as they grew older. Observed fluctuations in weight and rib fat depth, within each year, were associated with pasture availability and physiological demands. Cows that did not wean a calf in a given year became heavier and fatter than cows that did; and they remained so when they calved the following year. High-fat and High-RFI were always fatter and lighter than Low-fat and Low-RFI cows, respectively. The difference in rib fat and fatness between High- and Low-RFI lines (P 0.05). Supplementary feeding threshold was reached earlier by Low-fat and Low-RFI cows than their counterparts. Calculations based on the data in the present paper estimate that if cows lose condition at a rapid rate (1 condition score/month), then a cow with an extra 1 mm rib fat EBV would take 7.5 days longer to reach the same supplementary feeding threshold. Fat EBVs can, therefore, be a useful tool in assisting beef producers to match genotype to their production system

Divergent genotypes for fatness or residual feed intake in Angus cattle. 2. Body composition but not reproduction was affected in first-parity cows on both low and high levels of nutrition

This paper reports a subset of results from the Beef Cooperative Research Centre-funded Maternal Productivity Project. This research aimed to describe the response of Angus cows of different and divergent genotypes to variable nutritional environments over five breeding seasons. Cows selected for a divergence in either fat depth (HFat vs LFat) or residual feed intake (RFI: HRFI vs LRFI) based on mid-parent estimated breeding values (EBV) for those traits were allocated in replicate groups to either high or low nutritional treatments at two different sites, namely the Vasse Research Centre in Western Australia and the Struan Research Centre in South Australia. The traits reported in this paper include output traits (birth and weaning weight of calves, liveweight change of cows), change traits (change in Rib Fat, P8 fat, eye muscle area and liveweight between specified time points) and reproductive traits [pregnancy rates, percentage calves born alive and days to calving at the days to calving at the second calving opportunity (DC2)]. Having had their first calf, the vulnerability of these young cows to nutritional restriction and how it may adversely affect rebreeding was examined. HFat and HRFI cows were fatter, heavier and had greater eye muscle area than LFat and LRFI, respectively, at all times during the breeding cycle on both levels of nutrition. There was no difference in either days-to-calving or pregnancy rates after the second mating between genotypes. Equally, nutritional treatment had no effect on these traits in this cohort of cows. There was evidence for an implied genetic correlation between Rib Fat EBV, DC2 and pregnancy rates of –0.38 that suggests that selection for leanness may result in reduced fertility of the herd but the effect was not significant herein. As long as producers record the phenotype for both traits and select cows with favourable DC2 as well as low fatness, these problems can be avoided, owing to only 22% of variation in pregnancy rates being explained by DC2 and Rib Fat EBV. Producers can largely be confident that selection for leanness, or increased feed efficiency, has little impact on productivity as long as cows are in adequate body condition to remain healthy and productive

Divergent genotypes for fatness or residual feed intake in Angus cattle. 7. Low-fat and low-RFI cows produce more liveweight and better gross margins than do high-fat and high-RFI cows when managed under the same conditions

The present paper focuses on the economic evaluation of the observed differences in maternal productivity of different genetic lines in Angus cattle that were managed under contrasting nutritional regimes typical of southern Australia. Five hundred Angus cows were managed concurrently at two locations in southern Australia. On each site, the cows were managed under the following two different nutritional treatments: High and Low, to simulate different stocking rates. Cows selected for a divergence in either carcass rib-fat depth or residual feed intake based on mid-parent estimated breeding values for those traits, were allocated in replicate groups to either High- or Low-nutrition treatments. By design, the supplementary feeding regime was the same for the High and Low genetic lines to ensure genetic differences were not confounded with management differences. Animal productivity results from the experiment were used as input data to evaluate the economic performance of the four genetic lines under the two nutritional treatments. Two methods were used; the first was a gross-margin calculation of income minus variable costs as AU$ per breeding cow for a 1000-cow herd; the second was a whole-farm linear programming model maximising the gross margin. Stocking rates were optimised by matching the energy requirements for the whole herd with the energy available from pasture and supplementary feed on a representative 700-ha farm. Using the two methods of calculating gross margin (per cow and optimised per hectare), including examination of sensitivity to changes in prices of cattle and supplementary feed, the present study demonstrated that genetically leaner cows due to selection of low fat or low residual feed intake, had gross margins superior to those of genetically fatter cows. They generated more income by selling more liveweight due to heavier weights and higher stocking rates. The results are affected by the management system utilised and some confounding with growth (leaner genetic lines had higher growth estimated breeding values), but will assist producers to make more informed decisions about how to manage animal breeding and nutritional interactions

Divergent genotypes for fatness or residual feed intake in Angus cattle. 3. Performance of mature cows

This experiment evaluated the productivity of 500 Angus cows that differed in genetic merit for either subcutaneous rib fat depth (Fat) or residual feed intake (RFI) based on estimated breeding values (EBVs) and managed under two levels of nutrition. Reproductive rate over four calving opportunities in mature cows and growth performance of progeny to weaning was assessed. Level of nutrition significantly affected all body composition traits for both Fat and RFI line cows. Cows on High-Nutrition were 14–16% heavier (P < 0.001) than those on Low-Nutrition. Differences in EBVs for fatness were reflected in phenotypic fatness at maturity. High-RFI line cows were fatter for both scanned rump (P8) and rib (RIB) fat depth relative to their Low-RFI contemporaries. Of those cows that were lactating, there was no significant effect of line or nutrition on pregnancy rate or days to calving (DC). There was, however, a trend (P < 0.1) in the Low-Fat line cows towards longer DC compared with the High-Fat line cows. There was no significant effect of either line or nutrition on calf birthweight. Calves with mothers on High-Nutrition were 8% heavier at weaning (P < 0.001) than those on Low-Nutrition. Lower EBVs for RFI was associated with higher 200-day growth EBV and heavier calves at weaning. Current carcass BREEDPLAN EBVs can be used to select for changes in cow body composition if desired. In this experiment, Angus cows selected for lower RFI or with below-average fatness EBV and had raised a calf at every previous opportunity were not compromised in pregnancy rate or DC at maturity under varying nutrition such as can be experienced during normal seasonal conditions in southern Australia. However, selection for lower RFI was associated with lower weaning rate (P < 0.05), which warrants further investigation to confidently predict the implications for commercial cattle production