Protein Requirements For Maintenance Research Articles

Effects of late gestational nutrient restriction on uterine artery blood flow, placental size, and cotyledonary mRNA expression in primiparous beef females.

Fall-calving primiparous beef females [body weight (BW): 451 ± 28 (SD) kg; body condition score (BCS): 5.4 ± 0.7] were individually-fed either 100% (control; CON; n = 13) or 70% (nutrient restricted; NR; n = 13) of metabolizable energy and metabolizable protein requirements for maintenance, pregnancy, and growth from day 160 of gestation to parturition. Doppler ultrasonography of both uterine arteries was conducted pre-treatment and every 21 d from days 181 to 265 of gestation. Expelled placentas were collected, and ipsilateral cotyledonary tissue was sampled to assess relative messenger ribonucleic acid (mRNA) expression. Placentas were separated into ipsilateral and contralateral sides, dissected (cotyledonary vs. intercotyledonary), and dried. Data were analyzed with nutritional plane, treatment initiation date, and calf sex (when P < 0.25) as fixed effects. Uterine blood flow included day and nutritional plane × day as repeated measures. We previously reported that post-calving, NR dams weighed 64kg less and were 2.0 BCS lower than CON, but calf birth weight was not affected. Maternal heart rate was less (P < 0.001) for NR dams than CON after nutritional planes began. Nutritional plane did not affect (P ≥ 0.20) uterine artery hemodynamics, but all variables were affected (P ≤ 0.04) by day. Contralateral cotyledonary and placental weight were less (P ≤ 0.04) and contralateral intercotyledonary weight and number of cotyledons tended to be less (P ≤ 0.10) for NR dams than CON, but ipsilateral and whole placental weights were not affected (P ≥ 0.13). Ipsilateral placental weight as a percentage of total placental weight was greater (P = 0.03) for NR dams than CON. Whole placental cotyledonary:intercotyledonary weight was less (P = 0.01) for NR dams than CON. Placental efficiency was not affected (P = 0.89) by nutritional plane. Cotyledonary relative mRNA expression of GLUT3 and SNAT2 was greater (P ≤ 0.05) and relative expression of GLUT1, GLUT4, and NOS3 tended to be greater (P ≤ 0.07) for NR dams than CON. Nutritional plane did not affect (P ≥ 0.13) relative mRNA expression of GLUT5, 4F2hc, CAT1, LAT1, LAT2, VEGFA, FLT1, KDR, GUCY1B3, and PAG2. Despite less contralateral placental growth, beef heifers experiencing late gestational nutrient restriction maintained uterine artery blood flow and total placental mass and had 4 nutrient transporters and 1 angiogenic factor upregulated in cotyledons, all which likely contributed to conserving fetal growth.

PSIV-A-4 Effect of late gestational nutrient restriction on locomotor activity of beef heifers

Abstract The objective of this study was to determine the effects of nutrient restriction on locomotor behavior during late gestation. Fall-calving crossbred beef heifers were moved to 3.7 × 15.8 m partially-covered pens and individually-fed 100% (control; n = 13) or 70% (nutrient restricted; n = 13) of NASEM metabolizable energy and metabolizable protein requirements for maintenance, pregnancy, and growth from d 160 of gestation to calving. Diets were based on chopped sorghum sudan hay fed in Calan gates and supplemented to meet targeted nutritional planes. IceQube accelerometers (iceRobotics, Edinburgh, UK) were placed on the left hind fetlock between d 158 and 168 of gestation to determine standing time, lying time, step count, number of lying bouts, and motion index. Daily behavior data were averaged for 5 distinct periods (period 1: IceQube placement to d 180 of gestation; period 2: d 181 to 201 of gestation; period 3: d 202 to 222 of gestation; period 4: d 223 to 243 of gestation; and period 5: 244 to 264 of gestation). Days in which animals were moved from their pens were excluded from the data set, resulting in an average of 17.2 ± 2.35 d per period. Data were analyzed with fixed effects of nutritional plane, period, and their interaction in the model. Maternal sire and day of treatment initiation were included as covariates. The number of lying bouts was affected (P = 0.02) by the nutritional plane × period interaction. Within period, there was no effect (P ≥ 0.20) of nutritional plane on lying bouts. Lying bouts in control heifers decreased (P = 0.008) from period 1 to 2, whereas lying bouts in nutrient restricted heifers decreased (P = 0.002) from period 1 to 2 before increasing (P = 0.02) again from period 2 to 3. Motion index and step count were affected (P ≤ 0.05) by nutritional plane, where both were greater in control heifers. Motion index and step count were affected (P &amp;lt; 0.001) by period, while standing time and lying time tended to be affected (P ≤ 0.09) by period. Motion index and step count decreased (P &amp;lt; 0.001) between periods 1 and 2 and periods 3 and 4 but increased (P ≤ 0.004) between periods 2 and 3 and periods 4 and 5. Standing time decreased (P = 0.02), while lying time increased (P = 0.02), between periods 3 and 4. These data suggest that nutrient restricted heifers may have reduced locomotor behavior in late gestation compared with control heifers. Throughout all periods of gestation, control heifers took more daily steps and had a greater motion index, suggesting that nutrient availability in late gestation may directly impact locomotor behavior of beef heifers.

PSIV-A-7 Effects of late gestational nutrient restriction of beef heifers on small intestinal crypt depth in neonatal calves

Abstract We hypothesized that late gestational nutrient restriction would impair small intestinal development in neonatal calves, including crypt cell depth and proliferation. Fall-calving crossbred beef heifers [body weight (BW) = 466 ± 30 (SD) kg; BCS: 5.4 ± 0.5] bred to a single sire were individually-fed 100% (control; n = 10) or 70% (nutrient restricted; n = 12) of NASEM metabolizable energy and metabolizable protein requirements for maintenance, pregnancy, and growth from d 160 of gestation to calving. Calves were removed from their dams immediately post-calving and fed artificial colostrum and milk replacer relative to body weight until euthanasia at 48.7 ± 0.4 h of age. The gastrointestinal tract was removed, and proximal jejunum samples were dissected from each calf and immersion-fixed in 10% neutral buffered formalin. Tissues were embedded in paraffin blocks and cut into 5-µm sections that were mounted on glass slides. Slides were incubated with Ki-67 (marker of nuclear proliferation) and counterstained with Hematoxylin using an autostainer. Images were taken at 5× magnification using an upright microscope. QuPath software was used to measure crypt depth, starting at the base of the crypt region and ending at the furthest cluster of Ki-67 positive cells, perpendicular to the base of the mucosa. For each calf, 10 crypt depth measurements were taken from 4 images, resulting in 40 crypt depth measurements that were averaged. Nutritional plane was a fixed effect in the model, and maternal sire, date of study initiation, and calf sex (when P &amp;lt; 0.25) were considered covariates. We previously reported that calves born to nutrient restricted dams weighed less (P ≤ 0.05) at birth and 48 h than calves born to control dams. Small intestinal mass tended to be less (P = 0.11) in offspring of nutrient restricted dams but was not affected (P = 0.58) when expressed relative to body weight. Calves born to nutrient restricted dams also tended to have less (P = 0.11) small intestinal mass relative to brain weight. Maternal nutrient restriction did not affect (P = 0.95) jejunal crypt depth. Additionally, crypt depth relative to body weight was not affected (P = 0.20) by nutrient restriction. Although crypt depth was not affected, further analysis of proliferation and morphology will help to understand the relationship between maternal nutrient restriction and small intestine development in neonatal calves.

Supplementation of Acacia dealbata versus Acacia mearnsii leaf-meal has potential to maintain growth performance of lambs grazing low-quality communal rangelands in South Africa

Supplementing livestock grazing communal rangelands with leaf-meals from Acacia trees, which are currently considered as problematic invasive alien plants globally, may be a sustainable way of exploiting their desirable nutritional and anthelmintic properties. The current study evaluated worm burdens and growth performance of lambs grazing low-quality communal rangelands supplemented with leaf-meals prepared from the invasive alien plant species; Acacia mearnsii or A. dealbata. Forty, three-month-old ewe lambs weighing an average of 18.9 ± 0.60 kg were randomly allocated to four supplementary diets: (1) rangeland hay only (control), (2) commercial protein supplement plus rangeland hay, (3) A. mearnsii leaf-meal plus rangeland hay and (4) A. dealbata leaf-meal plus rangeland hay. All the supplementary diets were formulated to meet the lambs’ minimum maintenance requirements for protein. All the lambs were grazed on communal rangelands daily from 0800 to 1400 after which they were penned to allow them access to their respective supplementary diets until 08:00 the following morning. The respective supplementary diets were offered at the rate of 400 g ewe− 1 day− 1 for 60 days. Lambs fed the commercial protein supplement had the highest dry matter intake followed by those fed the Acacia leaf-meals and the control diet, respectively (P ≤ 0.05). Relative to the other supplementary diets, lambs fed the commercial protein supplement and A. dealbata leaf-meal had higher (P ≤ 0.05) final body weight and average daily gains. Dietary supplementation did not affect lamb faecal worm egg counts over the study period (P > 0.05). There was no association between supplementary diets and lamb FAMACHA© scores (P > 0.05). It was concluded that supplementation of Acacia dealbata versus Acacia mearnsii has the potential to emulate commercial protein in maintaining growth performance of lambs grazing communal rangelands in the dry season.

Estimation of Protein and Amino Acid Requirements in Layer Chicks Depending on Dynamic Model.

Four trials were conducted to establish a protein and amino acid requirement model for layer chicks over 0-6 weeks by using the analytical factorization method. In trial 1, a total of 90 one-day-old Jing Tint 6 chicks with similar body weight were selected to determine the growth curve, carcass and feather protein deposition, and amino acid patterns of carcass and feather proteins. In trials 2 and 3, 24 seven-day-old and 24 thirty-five-day-old Jing Tint 6 chicks were selected to determine the protein maintenance requirements, amino acid pattern, and net protein utilization rate. In trial 4, 24 ten-day-old and 24 thirty-eight-day-old Jing Tint 6 chicks were selected to determine the standard terminal ileal digestibility of amino acids. The chicks were fed either a corn-soybean basal diet, a low nitrogen diet, or a nitrogen-free diet throughout the different trials. The Gompertz equation showed that there is a functional relationship between body weight and age, described as BWt(g) = 2669.317 × exp(-4.337 × exp(-0.019t)). Integration of the test results gave a comprehensive dynamic model equation that could accurately calculate the weekly protein and amino acid requirements of the layer chicks. By applying the model, it was found that the protein requirements for Jing Tint 6 chicks during the 6-week period were 21.15, 20.54, 18.26, 18.77, 17.79, and 16.51, respectively. The model-predicted amino acid requirements for Jing Tint 6 chicks during the 6-week period were as follows: Aspartic acid (0.992-1.284), Threonine (0.601-0.750), Serine (0.984-1.542), Glutamic acid (1.661-1.925), Glycine (0.992-1.227), Alanine (0.909-0.961), Valine (0.773-1.121), Cystine (0.843-1.347), Methionine (0.210-0.267), Isoleucine (0.590-0.715), Leucine (0.977-1.208), Tyrosine (0.362-0.504), Phenylalanine (0.584-0.786), Histidine (0.169-0.250), Lysine (0.3999-0.500), Arginine (0.824-1.147), Proline (1.114-1.684), and Tryptophan (0.063-0.098). In conclusion, this study constructed a dynamic model for the protein and amino acid requirements of Jing Tint 6 chicks during the brooding period, providing an important insight to improve precise feeding for layer chicks through this dynamic model calculation.

PSIV-14 Effects of Maternal Nutrient Restriction During Late Gestation on Expelled Cotyledonary Mrna Expression in Primiparous Beef Females

Abstract To determine the effects of late gestational nutrient restriction on expelled cotyledonary mRNA expression, fall-calving Hereford × Simmental-Angus heifers [single-sired; BW: 451 ± 28 (SD) kg; BCS: 5.4 ± 0.7] bred to a single sire were allocated by fetal sex and expected calving date to receive either 100% (control; CON; n = 12) or 70% (nutrient restricted; NR; n = 11) of NASEM metabolizable energy and metabolizable protein requirements for maintenance, pregnancy, and growth. Beginning on d 160 of gestation, heifers were individually fed chopped sorghum sudan hay (1.74 Mcal ME/kg, 6.69% CP, 72.0% NDF; DM basis) and based on individual intakes, supplemented to meet targeted nutritional planes. Calving was observed for all females and placentas were collected at natural expulsion. Immediately after collection (average: 4.5 h post-calving; range: 2.3 to 12.1 h post-calving), 2 representative cotyledons on the ipsilateral side were cleaned with phosphate buffered saline, and cotyledonary tissue was flash frozen. Total RNA was extracted, and RT-qPCR was performed for mRNA expression of glucose transporters (SLC2A1, SLC2A3, SLC2A4), a fructose transporter (SLC2A5), amino acid transporters (SLC1A1, SLC3A2, SLC7A1, SLC7A5, SLC7A8, SLC38A2), angiogenic factors/receptors (VEGFA, NOS3, FLT1, KDR, GUCY1B3), and pregnancy-associated glycoprotein 2 (PAG2). Relative mRNA expression was analyzed with nutritional plane, treatment initiation date, time to cotyledon sampling, and calf sex (when P &amp;lt; 0.25) as fixed effects. We have previously reported that total uterine blood flow during late gestation was not affected (P ≥ 0.20) by nutritional plane or the nutritional plane × day of gestation interaction. Post-calving, NR dams were 64 kg BW less (P &amp;lt; 0.001) and 2.0 BCS less (P &amp;lt; 0.001), but calf birth weight was not affected (P = 0.72) by nutritional plane. Contralateral placental dry weight tended to be less (P = 0.07) in NR dams, but total placental weight was not affected (P = 0.86) by late gestational nutritional plane. Cotyledonary relative mRNA expression of SLC2A3 and SLC38A2 was greater (P ≤ 0.05) and relative expression of SLC2A1, SLC2A4, and NOS3 tended to be greater (P ≤ 0.07) in NR dams compared with CON. Late gestational nutritional plane did not affect (P ≥ 0.13) cotyledonary relative mRNA expression of FLT1, GUCY1B3, KDR, PAG2, SLC1A1, SLC2A5, SLC3A2, SLC7A1, SLC7A5, SLC7A8, and VEGFA. In summary, first parity beef females who experienced late gestational nutrient restriction maintained uterine blood flow and placental mass and had 4 nutrient transporters and 1 angiogenic factor upregulated in cotyledons, all which likely contributed to their conservation of fetal growth.

71 Effects of Late Gestational Nutrient Restriction on Calf pre-Weaning Growth, Backgrounding and Feedlot Performance, and Carcass Composition

Abstract Fall-calving Hereford-SimAngus heifers [single-sired; BW: 451 ± 28 (SD) kg; BCS: 5.4 ± 0.7] bred to a single sire were individually fed 100% (control; CON; n = 12) or 70% (nutrient restricted; NR; n = 13) of NASEM metabolizable energy and metabolizable protein requirements for maintenance, pregnancy, and growth from day 160 of gestation to calving. Post-calving, all females were fed chopped tall-fescue hay supplemented to meet lactational nutrient requirements in Calan gates to constrain diets of calves to milk only until day 147, then pen-fed in drylots until weaning at day 242 ± 3 (SD). Post-weaning, calves were fed a tall fescue hay-based backgrounding diet in the same large drylots for 53 ± 12 d, then moved to partially covered pens with GrowSafe feeding systems in 2 groups and fed a corn-based feedlot diet (formulated to be 18.3% CP, 1.21 Mcal NEg/kg, DM basis; 89% DM) for 255 ± 3 d (similar days on feed rather than carcass endpoint). Cattle were harvested in a commercial plant, and camera carcass grading was performed. Data were analyzed with maternal treatment, calving date, and calf sex (when P &amp;lt; 0.25) as fixed effects; feedlot group was included for feedlot and carcass measures. We previously reported that birth weight was not affected (P = 0.72), but NR decreased (P &amp;lt; 0.04) milk production by 15%. Calves born to NR dams had reduced ADG from birth to day 147 (P = 0.02), day 147 to weaning (P = 0.08), and birth to weaning (P = 0.003), resulting in NR calves having 13% lighter (P = 0.004) weaning weight. Backgrounding ADG was not affected (P = 0.80) by maternal treatment; thus, feedlot entry BW was 11% less (P = 0.009) in NR calves. On day 28, 56, 84, and 112 on feed, NR calves weighed less (P ≤ 0.09) than control. Final BW was not affected (P = 0.91) by maternal treatment. Feedlot ADG was greater for NR calves from day 168 to slaughter (P = 0.02) and the overall feeding period (P = 0.03), but not before day 168 on feed (P ≥ 0.22). Calves born to NR dams had less (P = 0.02) dressing percentage, but improved (P = 0.02) yield grade and backfat thickness. Hot carcass weight, ribeye area, marbling score, and KPH were not affected (P ≥ 0.26) by maternal treatment. Percent prime, yield grade ≤ 2, and yield grade ≥ 4 were not affected (P ≥ 0.29) by maternal treatment. Overall, late gestational nutrient restriction decreased growth pre-weaning but increased late finishing growth, without affecting backgrounding or early feedlot growth. These cattle had leaner carcasses after similar days on feed, suggesting that late gestational nutrient restriction altered growth patterns or body composition.

70 Nutrient Restriction During Late Gestation Alters Maternal Circulating Amino Acid Concentrations in Primiparous Beef Females

Abstract We hypothesized that maternal circulating AA concentrations would be reduced by late gestational nutrient restriction, indicating less available nutrients for transport by the uteroplacenta to the growing fetus. Fall-calving Hereford-SimAngus heifers [single-sired; BW: 451 ± 28 (SD) kg; BCS: 5.4 ± 0.7] bred to a single sire were allocated by fetal sex and expected calving date to receive either 100% (control; CON; n = 12) or 70% (NR; n = 13) of NASEM metabolizable energy and metabolizable protein requirements for maintenance, pregnancy, and growth from day 160 of gestation to calving. Heifers were individually fed chopped sorghum sudan hay (1.74 Mcal ME, 6.66% CP, 72.0% NDF; DM basis) and based on individual intakes, supplemented to meet targeted nutritional planes. Jugular blood samples were obtained on days 159 (Pre-treatment), 202, and 244 of gestation, and 1 h post-calving to determine serum concentrations of the 20 common AA (except cysteine), 1-methyl histidine, and 3-methyl histidine. Gestational and post-calving AA were analyzed separately with nutritional plane, treatment initiation date, and calf sex (when P &amp;lt; 0.25) as fixed effects. Gestational AA included day and nutritional plane x day using repeated measures. We have previously reported that dam BCS was less (P ≤ 0.04) by day 202 of gestation and dam BW was less (P ≤ 0.01) by day 223 of gestation for NR dams. Post-calving, NR dams were 64 kg BW and 2.0 BCS lless (P &amp;lt; 0.001), but calf birth weight was not affected (P = 0.72) by nutritional plane. Histidine, lysine, and methionine were greater (P ≤ 0.03) in NR dams on day 202 of gestation. Tryptophan and valine were less (P ≤ 0.05) while methionine and total AA tended to be less (P ≤ 0.08) on day 244 of gestation in NR dams. Aspartic acid, glutamic acid, and tyrosine were less (P ≤ 0.03), but 3-methyl histidine was greater (P ≤ 0.01) on days 202 and 244 of gestation in NR dams. 1-methyl histidine was greater (P ≤ 0.05) at all 3 gestational timepoints but leucine was less (P = 0.03) in NR dams during gestation. Post-calving, glutamic acid, leucine, and valine were less (P ≤ 0.04), and methionine, threonine, tryptophan, tyrosine, and total AA tended to be less (P ≤ 0.10) in NR dams. Histidine, 1-methyl histidine, 3-methyl histidine, and serine were greater (P ≤ 0.03) in NR dams post-calving. In summary, late gestational nutrient restriction reduced total maternal circulating AA and altered the maternal serum AA profile, but calf birth weight was not affected. Individual AA that were greater or unaffected in NR dams were likely indicative of body protein catabolism occurring to meet nutrient requirements.

Energy and protein requirements for maintenance and weight gain of Canindé goats supplemented on pasture in the semi-arid region

The purpose of this study was to estimate the carcass composition, and energy and protein requirements for maintenance and weight gain of Canindé goats supplemented on pasture in a semi-arid region. Forty-six castrated animals, with initial body weight (BW) of 15.7 ± 0.96 kg, grazing in Caatinga were used. Six animals were slaughtered at the beginning of the experiment representing the initial carcass composition (reference animals; 16.1 ± 1.15 kg BW), while the other animals were randomly distributed in four treatments (concentrate supplementation at 0%, 0.5%, 1.0%, and 1.5% BW), with ten animals per treatment. When one of the animals of each group reached 25 kg BW, all animals in that group were slaughtered. The whole empty body was weighed, ground, homogenized, and sampled for further chemical analyses. The level of supplementation influenced dry matter intake, retained energy, and body weight gain of Canindé goats. The energy (kcal/kg) and fat (g/kg EBW) contents in the carcass of goats of 15, 20, and 25 kg were 2.29 and 86.11, 2.39 and 113.48, and 2.47 and 140.53, respectively. The minimum nitrogen losses were 188 mg N/EBW0.75. The net and metabolizable energy for maintenance were 72.11 kcal/EBW0.75/day and 2.19 g/kg EBW0.75/day, respectively. The net and metabolizable protein requirements were 2.19 and 1.88 g/kg EBW0.75, respectively. The net energy and protein requirements for weight gain ranged from 2.61 to 2.81 Mcal/kg EBW gain and 194.37–222.55 g protein/kg EBW, respectively, for animals from 15 to 25 kg BW. It is concluded that the energy and protein nutritional requirements of Canindé goats supplemented on pasture in the semi-arid region vary according to body weight.

Protein requirements for pregnant dairy cows

We aimed to estimate the protein requirements of pregnant Holstein × Gyr cows. Sixty-one Holstein × Gyr (HG) cows were used, with an average initial BW of 480 ± 10.1 kg and 5 ± 0.5 yrs of age. Cows were divided into 3 groups: pregnant (n = 43), non-pregnant (n = 12), and baseline (n = 6). Baseline animals were slaughtered before starting the experiment to estimate the initial body composition of the remaining animals. Pregnant and non-pregnant cows received 2 diets: maintenance and ad libitum. Pregnant cows were slaughtered at 139, 199, 241, and 268 gestation days (GD). First, we used data only from non-pregnant cows to determine the requirements for maintenance and growth in adult cows. The requirements of metabolizable protein for maintenance (MPm; g/EBW0.75/d) were estimated using a linear regression between the metabolizable protein intake (MPI, g/d) and average daily gain (g/d), and the MPm was defined as the intercept divided by the average BW0.75. Net protein requirements for gain (NPg; g/d) were estimated by the first derivative of the allometric equation between final crude protein (CP) in the body (kg) and the final EBW (kg). The efficiency of use of metabolizable protein for gain (k) was calculated from the regression between the retained protein (g/EBW0.75/d) and the MPI (g/EBW0.75/d), and k was the slope of this regression. The MPI was estimated by combining microbial protein synthesis (purine derivatives) with the digestible rumen undegradable protein [(total protein intake minus RDP) × intestinal digestibility]. Second, an exponential model was used to fit the protein accumulation in the gestational components in the function of GD. The first derivative of that model was considered the net requirement for gestation (NPgest). The efficiency of protein utilization for gestation (kgest) was calculated by the iterative method using the equation: Δ = MPI - (MPm + NPg/kg + NPgest/kgest). The iteration was performed aiming at a zero deviation between observed MPI and MP estimated by the requirements determined herein. We obtained a value of 3.88 g/EBW0.75/d for MPm. The estimation of NPg can be calculated according to the following equation: NPg = 0.716 × (EBWopen-0.308) × EBGcorrected, where EBWopen is the empty BW (kg) for non-pregnant animals and EBGcorrected is the empty body gain (kg/d) corrected for the gestational component. The k was determined as 0.347. The net protein requirements for gestation (NPgest) were determined as NPgest (g/d) = 0.0008722 × exp(0.01784 ×GD) × (calfweight/35). The efficiency of using metabolizable protein for gestation (kgest) was 0.625. It is important to highlight that different methods of MP estimates should not be mixed and that the proposed method requires the estimate of microbial protein (estimate it via urinary estimates) and might be a limitation for practical application. In conclusion, new studies should be conducted to validate our results and the methodology adopted to determine protein requirements for pregnancy in dairy cows. Due to the pattern of protein accumulation in the gestational components, we suggest that exponential model to describe protein requirements for pregnancy for dairy cows.

Protein requirement for maintenance of growing Boer crossbred doe.

The effect of protein intake on nutrient metabolism and growth performance of female ≥ 50% Boer crossbred goats was investigated, along with protein requirements for their maintenance. Sixteen does were divided into four groups that were fed different levels of crude protein relative to the level recommended for purebred Boer by NRC (2007): 85% (0.85M), 100% (1.00M), 115% (1.15M), and 130% (1.30M). The experiment was conducted with does at 4-9months of age. Feed intake, growth rate, nutrient digestibility, nitrogen balance, and microbial protein synthesis of the does were determined. The relationship between crude protein intake (g/kg0.75 BW) and average daily gain (g/day) was tested using linear regression. It was found that crude protein intake, average daily gain, nitrogen balance, and microbial protein supply increased with dietary crude protein. Nutrient digestibility and nitrogen excreted via urine were not affected by treatments. At 4-6months of age, Boer crossbred does require crude protein for maintenance to be ingested and absorbed at levels of 3.81 and 1.99g/kg0.75 BW, respectively, while at 7-9months of age, does require 4.68g/kg0.75 BW ingested crude protein. Overall, growing does require 4.26g/kg0.75 BW ingested crude protein for maintenance during 4-9months of age, which is 6.78% lower than the recommendation of NRC (2007).

Maternal nutrient restriction during late gestation reduces vigor and alters blood chemistry and hematology in neonatal beef calves.

Fall-calving primiparous beef females [body weight: 451 ± 28 (SD) kg; body condition score: 5.4 ± 0.7] were individually-fed either 100% (control; CON; n = 13) or 70% (nutrient restricted; NR; n = 13) of metabolizable energy and metabolizable protein requirements for maintenance, pregnancy, and growth from day 160 of gestation to parturition. Calves were reared naturally by their dams and monitored for latency times from birth to first sternal recumbency, attempt to stand, and stand; vigor scores were assigned at 2, 5, 10, and 20min of age. Rectal temperatures and jugular blood were obtained at 0 (pre-suckling), 6, 12, 24, and 48h of age, and blood chemistry, hematology, cortisol, and insulin were determined. Data were analyzed with fixed effects of late gestational nutritional plane (single data point) or nutritional plane, hour, and their interaction (data over time, repeated measures). Calving date was a fixed effect; calf sex was included when P < 0.25. We previously reported that late gestational nutritional plane did not affect gestation length or calf size at birth, but calving assistance and fetal malpresentations occurred more often in NR. Nutritional plane did not affect (P = 0.65) duration of parturition, but calves born to NR dams had slower times to attempt to stand (P = 0.09), slower times to stand (P = 0.02), and had poorer 20min vigor scores (P = 0.05). Serum immunoglobulin G and A concentrations at 48h were greater (P ≤ 0.03) for NR calves. Rectal temperature of NR calves was less (P = 0.02) at 0h, but greater (P = 0.04) at 24h compared with CON. Circulating glucose, non-esterified fatty acids, triglycerides, cortisol, and insulin were not affected by nutritional plane (P ≥ 0.18). Total protein and globulin from 6 to 48h were greater (P ≤ 0.02) in NR calves. Calves from NR dams had greater (P < 0.08) gamma-glutamyl transferase at 6, 12, and 48h. Serum aspartate aminotransferase was greater (P ≤ 0.07) from 0 to 24h and creatine kinase was greater (P ≤ 0.04) from 6 to 24h in NR calves. At 0h, potassium was greater (P = 0.03) in NR calves. Calves born to CON had greater chloride (P = 0.08; main effect), sodium (P ≤ 0.09) from 0 to 48h, and anion gap (P = 0.02) at 6h. Hematocrit from 6 to 24h and red blood cells and hemoglobin at 6 and 12h were greater (P ≤ 0.09) in CON calves. These data indicate that nutrient restriction during late gestation resulted in less vigorous calves with more indicators of trauma in early life.

Late gestational nutrient restriction in primiparous beef females: nutrient partitioning among the dam, fetus, and colostrum during gestation.

Fall-calving primiparous crossbred beef females [body weight (BW): 451 ± 28 (SD) kg; body condition score (BCS): 5.4 ± 0.7] were allocated by fetal sex and expected calving date to receive either 100% (control; CON; n = 13) or 70% (nutrient restricted; NR; n = 13) of metabolizable energy and metabolizable protein requirements for maintenance, pregnancy, and growth from day 160 of gestation to calving. Heifers were individually-fed chopped poor quality hay and supplemented to meet targeted nutritional planes based on estimated hay intakes. Dam BW, BCS, backfat, and metabolic status were determined pre-treatment, every 21 d (BW and metabolic status) or 42 d (BCS and backfat) during gestation, and post-calving. At birth, calf BW and size were measured, and total colostrum from the most full rear quarter was collected pre-suckling. Data were analyzed with nutritional plane, treatment initiation date, and calf sex (when P < 0.25) as fixed effects. Gestational metabolites included day and nutritional plane × day as repeated measures. During late gestation, CON dams gained (P < 0.01) maternal (non-gravid) BW and maintained (P ≥ 0.17) BCS and backfat, while NR dams lost (P < 0.01) maternal BW, BCS, and backfat. Circulating glucose, urea N, and triglycerides were less (P ≤ 0.05) in NR dams than CON at most late gestational timepoints after treatment initiation. Circulating non-esterified fatty acids were greater (P < 0.01) in NR dams than CON. Post-calving, NR dams weighed 63.6 kg less (P < 0.01) and were 2.0 BCS less (P < 0.01) than CON. At 1 h post-calving, NR dams had less (P = 0.01) plasma glucose and tended to have less (P = 0.08) plasma triglycerides than CON. Nutrient restriction did not affect (P ≥ 0.27) gestation length, calf birth weight, or calf size at birth. Colostrum yield was 40% less (P = 0.04) in NR dams than CON. Protein and immunoglobulin concentrations were greater (P ≤ 0.04), but free glucose and urea N concentrations were less (P ≤ 0.03), in colostrum of NR dams than CON. Colostrum total lactose, free glucose, and urea N were less (P ≤ 0.03) in NR dams than CON, but total protein, triglycerides, and immunoglobulins were not affected (P ≥ 0.55). In summary, beef heifers experiencing late gestational nutrient restriction prioritized partitioning nutrients to fetal growth and colostrum production over maternal growth. During undernutrition, fetal and colostral nutrient demands were largely compensated for by catabolism of maternal tissue stores.

A new protein requirement system for dairy cows

Accurate prediction of protein requirements for maintenance and lactation is needed to develop more profitable diets and reduce N loss and its environmental impact. A new factorial approach for accounting for net protein requirement for maintenance (NPM) and metabolizable protein (MP) efficiency for lactation (EMPL) was developed from a meta-analysis of 223 N balance trials. We defined NPM as the sum of the endogenous protein fecal and urinary excretion and estimated it from the intercept of a nonlinear equation between N intake and combined total N fecal and urinary excretion. Our model had a strong goodness-of-fit to estimate NPM (6.32 ± 0.15 g protein/kg metabolic body weight; n = 807 treatment means; r = 0.91). We calculated the EMPL as a proportion of the N intake, minus N excreted in feces and urine, that was secreted in milk. A fixed-EMPL value of 0.705 ± 0.020 was proposed. In a second independent data set, nonammonia-nonmicrobial-N and microbial-N ruminal outflows were measured, and the adequacy of the MP prediction (51 studies; n = 192 means treatments) was assessed. Our system based on the fixed-EMPL model predicted the MP requirement for lactation and maintenance with higher accuracy than several North American and European dairy cattle nutrition models, including the INRA (2018) and NASEM (2021). Only the NRC (2001), CNCPS 6.5, and Feed into Milk (2004) models had similar accuracy to predict MP requirement. Our system may contribute to improve the prediction for MP requirements of maintenance and lactation. However, most refined predictive models of intestinal digestibility for rumen undegradable protein and microbial protein are still needed to reduce the evaluation biases in our model and external models for predicting the MP requirements of dairy cows.

PSII-A-5 Effects of Time Postpartum and Late Gestational Nutrient Restriction on Beef Heifer Colostrum

Abstract Our objectives were to determine changes in colostrum yield and composition across the 36 hours post-calving and effects of late gestational nutrient restriction (NR) on these changes. Fall-calving, crossbred beef heifers (BW: 472 ± 33 [SD] kg; BCS: 5.4 ± 0.5) were individually fed 100% (control; CON; n = 13) or 70% (NR; n = 13) of NASEM metabolizable energy and metabolizable protein requirements for maintenance, growth, and pregnancy from d 160 of gestation to parturition. Calves were removed from dams immediately post-calving and pre-suckling. Colostrum was hand-milked from all quarters at 1, 12, 24, and 36 h to determine total colostrum volume and weight. Colostrum protein, triglycerides, and milk urea nitrogen (MUN) concentration were analyzed using colorimetric assays on a UV-visible light microplate reader. Data were analyzed using fixed effects of treatment, hour, treatment × hour (repeated measures); calf sex, maternal sire, and treatment initiation date were covariates. Colostrum yield was affected (P &amp;lt; 0.02) by the treatment × hour interaction. Colostrum volume and weight were 28% less (P ≤ 0.03) for NR than CON at 1 h. For both treatments, colostrum volume and weight decreased (P ≤ 0.04) from 1 to 12 h, before increasing (P ≤ 0.02) from 12 to 36 h. Triglyceride concentration was greater (P = 0.03) in NR than CON. Both triglyceride concentration and total protein decreased (P ≤ 0.01) from 1 to 24 h. Protein concentration decreased (P &amp;lt; 0.001) from 1 to 36 h. Total triglycerides and MUN decreased (P &amp;lt; 0.001) from 1 to 12 h, before total MUN increased (P &amp;lt; 0.001) from 12 to 36 h and total triglycerides increased (P = 0.004) from 24 to 36 h. In conclusion, nutrient restriction may only affect colostrum yield at 1 h, and colostrum nutrient content decreases dramatically after the first milking.

298 Late Gestational Nutrient Restriction of Primiparous Beef Heifers Decreases Neonatal Calf Body Weight and Organ Mass

Abstract We hypothesized that late gestational nutrient restriction (NR) would decrease organ mass in neonatal calves. Fall-calving crossbred beef heifers (BW: 466 ± 30 [SD] kg; BCS: 5.4 ± 0.5) bred to a single sire were individually fed 100% (control; n = 10) or 70% (nutrient restricted; NR; n = 12) of NASEM metabolizable energy and metabolizable protein requirements for maintenance, pregnancy, and growth from d 160 of gestation to calving. Diets were based on chopped sorghum sudan hay and supplemented to meet targeted nutritional planes. Calves were removed immediately post-calving and fed colostrum and milk replacer relative to BW until euthanasia (48.7 ± 0.4 h of age) for organ mass determination. Nutritional plane was a fixed effect, and maternal sire, calf sex (when P &amp;lt; 0.25), and date of study initiation were covariates. Post-calving, NR dams were 62 kg BW and 2.1 BCS less (P &amp;lt; 0.001) than controls. Calf BW, liver, large intestine, omental/mesenteric fat, kidney, and heart weights were less (P ≤ 0.05) and carcass, rumen/reticulum/omasum, stomach complex, and total gastrointestinal tract weights tended to be less (P ≤ 0.09) in offspring from NR dams. Maternal nutrient restriction did not affect (P ≥ 0.11) weights of the small intestine, pancreas, abomasum, spleen, perirenal fat, adrenals, lungs, femur, and brain. Expressed per BW, lung weight was greater (P = 0.05), and brain and femur weight tended to be greater (P ≤ 0.10) in calves from NR dams, but other organ masses were unaffected (P ≥ 0.15). Expressed relative to brain weight, liver and large intestine weights were less (P ≤ 0.04) and carcass, total gastrointestinal tract, omental/mesenteric fat, and kidney weights tended to be less (P ≤ 0.08) in NR. In summary, late gestational NR decreased some organ masses in neonatal calves while sparing other tissues via asymmetric growth.

69. Modelling lysine requirement depending on protein deposition, maintenance requirement and dietary efficiency of utilisation for Japanese quail breeder

69. Modelling lysine requirement depending on protein deposition, maintenance requirement and dietary efficiency of utilisation for Japanese quail breeder

Correction to: Maintenance requirement and utilisation efficiency of energy and protein for ongrowing pikeperch (Sander lucioperca (L.))

Correction to: Maintenance requirement and utilisation efficiency of energy and protein for ongrowing pikeperch (Sander lucioperca (L.))

PSIII-6 Pre- and Postpartum Locomotor Activity in Nutrient Restricted Primiparous Beef Females

Abstract To determine the effects of late gestational nutrient restriction (NR) on pre- and postpartum locomotion, fall-calving Hereford-SimAngus heifers were individually fed 100% (control; CON; n = 11) or 70% (NR; n = 13) of energy and protein requirements for maintenance, pregnancy, and growth from d 160 of gestation to calving. Heifers were housed in 3.7 x 15.8 m pens, and IceQube accelerometers were placed on a hind fetlock on d 265 of gestation to record motion index (MI), standing time (ST), lying time (LT), step count, and lying bout number (LB). Prepartum data were analyzed by day (72 h prepartum), 6-h periods (24 h prepartum), and hour (6 h prepartum). Post-calving data were analyzed by day (7 d postpartum). All analyses had fixed effects of nutritional plane, time period, their interaction, and calving date. In both 72- and 24-h analyses, ST was greater (P ≤ 0.02) in NR compared with CON. Nutritional plane x day affected (P = 0.008) LB within 72 h prepartum, where NR females had an altered pattern across days. In the 6 h prepartum, MI was affected (P = 0.005) by nutritional plane x hour where NR were more variable than CON. Post-calving, standing time tended to be greater (P = 0.06) in NR compared with CON. In the 72-h prepartum analysis, ST increased (P = 0.005) on the final day pre-calving. Step count, MI, and LB increased (P ≤ 0.008) during the last 6 h prepartum. Standing time decreased (P = 0.04) at -1 h prepartum, while LB increased (P &amp;lt; 0.001) at -2 h and again at -1 h prepartum. Step count and MI decreased (P &amp;lt; 0.001) for the first 4 d postpartum, and LB were greatest on d 1 postpartum (P &amp;lt; 0.001). These data suggest late gestational nutrient restriction increases peripartum standing time in beef females.

208 Nutrient Restriction During Late Gestation Alters Beef Heifer Colostrum Composition

Abstract We hypothesized that late gestational nutrient restriction of beef heifers would decrease nutrient partitioning to the mammary gland, resulting in less colostrum nutrient availability for neonatal calves. Fall-calving Hereford-SimAngus heifers (single-sired; BW: 451 ± 28 [SD] kg; BCS: 5.4 ± 0.7) bred to a single sire were individually fed 100% (control; n = 12) or 70% (nutrient restricted; NR; n = 13) of NASEM net energy and metabolizable protein requirements for maintenance, pregnancy, and growth from d 160 of gestation to calving. Diets were based on chopped sorghum sudan hay (1.74 Mcal ME, 6.66% CP, 72.0% NDF; DM basis) supplemented to meet targeted nutritional planes. Calving was observed for all females, and total colostrum from one rear quarter was collected pre-suckling (50.5 ± 17 min [SD] postpartum). Colostrum nutrient composition was determined by colorimetric assays run on a UV-visible light microplate reader. Data were analyzed with treatment, calving date, and calf sex (when P &amp;lt; 0.25) as fixed effects. We have previously reported that single-quarter colostrum weight and volume were 40% less (P = 0.04) in NR compared with control heifers. Colostrum lactose concentration was not affected (P = 0.32) by treatment, but yield differences resulted in 46% less (P = 0.03) total single-quarter colostrum lactose in NR than control. Colostrum from NR heifers had 36% greater (P = 0.004) protein concentration than control, but greater colostrum yield of control heifers allowed for total protein to be unaffected (P = 0.57) by treatment. Nutrient restricted heifers had 23% less (P = 0.04) colostrum urea N concentration and 60% less (P = 0.01) total colostrum urea N than control. Late gestational nutrient restriction (P ≥ 0.59) did not affect colostrum triglyceride concentration or total. In summary, energy and protein restriction had disparate effects on nutrient partitioning to colostrum in primiparous beef females.