Heifer Body Weight Research Articles

Productivity and blood parameters of calves of different age groups when using a feed mixture based on humic acids

The effectiveness of the use of an organic feed mixture based on humic acids on body weight gain, average daily gains and blood parameters of calves of different age groups was analyzed. For 50 days, dairy calves aged 0 to 50 days and heifers of the experimental group aged 3–4 months were fed a feed mixture based on humic acids in the amount of 20 g/100 kg of animal body weight. The drug was added to milk (colostrum) of dairy calves and to water of heifers aged 3–4 months. The effectiveness of the use of humic acids was monitored by monitoring the body weight of animals at the beginning of the study and at the end of the study (after 50 days). Morphological, physical and biochemical blood parameters of animals were determined at the beginning of the study and at its end. Body weight of dairy calves and heifers 3–4 months age of the experimental group at the end of the experiment significantly increased (p˂0.05) and (p˂0.001), respectively, compared with the control group. Average daily gains exceeded the values of dairy calves (p˂0.001) and heifers 3-4 months of age (p˂0.05) of the control group, which indicates the ability to improve the digestibility of the diet, stimulating microbial activity in the intestine and, thus, improving the absorption of nutrients. According to the results of biochemical studies, changes in hemoglobin concentration in the blood of the experimental groups of dairy calves and heifers 3-4 months of age (p˂0.1), but they were not statistically significant. Along with this, at the end of the experiment, the heifers of the experimental group showed a slight increase in erythrocytes from 5.52±0.64 to 7.1 ± 0.60 T/l (p˂0.1) and a slight increase in the respiratory surface of erythrocytes due to an increase in the average volume of erythrocytes (p˂0.1), but these changes were not significant. The study of biochemical parameters of the blood serum of dairy calves of the experimental group indicates an increase in the concentration of total protein at the end of the experiment and total calcium at p˂0.1, but the changes were not statistically significant. In the blood serum of heifers of the experimental group of 3–4 months of age, the amount of total protein increased (p˂0.05), which indicates an improvement in the assimilation of proteins from the consumed feed. Humic acids have a positive effect on the mineral metabolism of 3–4-month-old heifers. age, in particular on the concentration of total calcium in blood serum (p˂0.05), which indicates an improvement in its absorption. Key words: humic acids, total protein, total calcium, inorganic phosphorus, blood serum, dairy calves, heifers.

PSXII-11 Impact of pre-breeding and breeding supplementation in May-born range heifers on growth rates and reproductive performance

Abstract Our objectives were to determine the impact rumen undegradable protein (RUP) supplementation prior to and during the breeding season had on growth rates and reproductive performance in May-born yearling range heifers. This study was conducted over a 3-yr period at the University of Nebraska, Gudmundsen Sandhills Laboratory (GSL) near Whitman, NE and utilized May-born Red Angus x Simmental crossbred heifers [n = 192; weaning body weight (BW) = 200 kg ± 28 kg]. Heifers were randomly assigned by pre-breeding BW to one of two treatments: 1) received 0.908 kg of a dried distillers grain supplement (DDGS; Supp, n = 66) pre-breeding through the breeding season or 2) received no supplement (NoSupp, n = 138). Each year, treatments were initiated in July and ended in August (55 ± 3 d). Using a C-Lock Smart Feeder (Rapid City, SD) heifers had individual access to their allotted DDGS supplementation. On average, NoSupp heifers consumed 0.09 kg/d (yr 1) and 0.02 kg/d (yr 2 and 3); whereas, Supp heifers averaged 0.59, 0.74, and 0.76 kg/d in yr 1, 2, and 3, respectively. Heifer BW was collected pre-trial (May), pre-breeding (July), breeding (August), pregnancy diagnosis (October), and pre-calving (April). Body condition score (BCS) was collected at pregnancy diagnosis (October) and pre-calving (April; Yr 1 and 2). Before each breeding season, two blood samples were collected 10 d apart to determine pubertal status. Heifers were synchronized with a single 5 mL intramuscular injection of prostaglandin F2 alpha (Lutalyse, Zoetis, Parsippany, NJ) 5 d after bull turnout during a 30 d natural service breeding season. Pregnancy diagnosis was determined via rectal ultrasound in October. No differences (P > 0.12) in BW were noted among treatments for all measurement timepoints. Moreover, SUPP heifers had greater (P < 0.02) average daily gain (ADG) from pre- trial to pregnancy diagnosis compared with NoSUPP heifers. However, there was no differences (P = 0.11) in ADG from pregnancy diagnosis to pre- calving. At pregnancy diagnosis (October), a treatment x year interaction (P = 0.02) for BCS was present where Supp heifers had a greater BCS than NoSupp heifers in yr 3. Heifer BCS pre-calving was not affected (P = 0.12) by treatment. There was a greater percentage (P < 0.01) of SUPP heifers cycling compared with NoSUPP heifers. However, there were no differences (P > 0.24) in pregnancy rates, the percentage that calved in the first 21 d, calf birth BW, or subsequent calving date. Ultimately, this study implies that providing a RUP supplement prior to and during the breeding season will increase the percentage of heifers that are cycling before breeding and have a greater ADG through pregnancy diagnosis; however, supplementation will not impact other reproductive parameters or BW gains.

286 Impact of rate of overwinter gain in March-born yearling range heifers on growth rates and reproductive performance

Abstract Our objective was to determine the impact of rate of overwinter gain in March-born yearling heifers on pre- and post-breeding growth rates and reproductive performance. Red Angus x Simmental crossbred beef heifers [n = 182; weaning body weight (BW) = 242 kg ± 23 kg] were utilized in a 3-yr study conducted at the University of Nebraska, Gudmundsen Sandhills Laboratory (GSL) near Whitman, NE. Using 3-d BW averages collected in January, heifers were stratified by BW and randomly assigned to one of two treatments: 1) to achieve a low overwinter rate of gain at 0.34 kg/d (LO, n = 106), or 2) to achieve a high overwinter rate of gain at 0.68 kg/d (HI, n = 76). To achieve gains, heifers were managed together and had individual access to a dried distillers grain supplement via a C-lock Smart Feeder (Rapid City, SD). Each year, treatments were initiated in January and ended in May (111 ± 4 d). Heifer BW was collected at the start of trial (January), end of the trial (May), pre-breeding (May), pregnancy diagnosis (October), and pre-calving (February). Heifer body condition score (BCS) was collected at pregnancy diagnosis (October) and pre-calving (February; Yr 1 and 2). Before the breeding season, two blood samples were collected 10-d apart via coccygeal venipuncture to determine the percentage of heifers cycling. At breeding, HI-fed heifers had a greater (P < 0.01) BW than LO-fed heifers (813 and 788 kg, respectively; Table 1). However, heifer BW at pregnancy diagnosis and pre-calving were not impacted (P ≥ 0.16) by supplemental treatment. Additionally, there were no differences (P ≥ 0.16) in BCS at pregnancy diagnosis and pre-calving among treatments. Furthermore, rate of gain did not influence (P ≥ 0.38) the percent pubertal prior to the breeding season, pregnancy rates, or the percent that calved in the first 21-d of the calving season. Moreover, rate of gain did not impact (P = 0.89) subsequent calf BW at birth. There was a significant treatment x year interaction (P < 0.01) for subsequent calving date, where HI treatment heifers calved 7-d earlier than LO treatment heifers in Yr 1. This study implies that producers can develop heifers at a less overwinter rate of gain without impacting reproductive performance or subsequent calf birth weight.

227 Moderate body weight loss reduces total antioxidant capacity in pregnant beef heifers and one-carbon metabolite supplementation does not mitigate this response

Abstract In beef heifers, body weight (BW) gain and physiological stress are important considerations for reproductive outcomes and whole herd production efficiencies. The objective of this study was to determine if dietary one-carbon metabolite (OCM) supplementation in moderate BW loss pregnant heifers alters circulating total antioxidant capacity, superoxide dismutase, and glutathione peroxidase activity. In a replicated 2 × 2 factorial, Angus-cross heifers (n = 81) were stratified by BW to gain 0.45 kg/d (CON) or lose 0.23 kg/d (RES) and receive corn carrier with OCM supplements (+OCM) or without (−OCM). The OCM supplements consisted of vitamin B12 (20 mg) and folate (320 mg) injections weekly and dietary rumen-protected methionine (7.4 g/d) and choline (44.4 g/d) from breeding (d 0) to d 63 of gestation. The four treatment groups were: CON−OCM (n = 20), CON+OCM (n = 21), RES−OCM (n = 21), and RES+OCM (n = 19). Heifers underwent estrus synchronization and were bred via artificial insemination using female sexed semen to a single sire. Pregnancy was diagnosed and fetal sex was verified on d 35 of gestation. Blood was collected and assayed for total antioxidant capacity, superoxide dismutase, and glutathione peroxidase activity on d −2 (baseline), 35, and 63 of gestation for all three replicates. Data were analyzed using the MIXED procedure of SAS with repeated measures to determine the effect of gain, supplement, day, and their two-way and three-way interactions. The gain × supplement interaction remained in all models, but other interactions were removed if P > 0.10. Replicate and heifer BW were included in the model as covariates and covariance structure was determined by lowest AIC and BIC. Statistical significance was considered at P ≤ 0.05 and tendencies at 0.05 < P ≤ 0.10. There was no BW gain × supplement interaction, or main effect of OCM supplements in total antioxidants. There was a gain × day effect (P ≤ 0.01), in which total antioxidants were increased on d 35 and further increased on d 63 in CON compared with RES treatments. There was no gain × supplement interaction, or main effect of gain or OCM supplements in superoxide dismutase and glutathione peroxidase. However, both superoxide dismutase and glutathione peroxidase were decreased (P ≤ 0.01) on d 63 compared with d 0 and 35. These data suggest that moderate BW loss reduces total antioxidant capacity in pregnant beef heifers, which could affect redox homeostasis. However, OCM supplements did not affect total antioxidant capacity, superoxide dismutase, or glutathione peroxidase. These findings are somewhat surprising considering oxidative stress has been well characterized in nutrient-restricted pregnancies, and given the interconnection between energy metabolism and one-carbon metabolism. Future research is warranted to fully elucidate the therapeutic effects of one-carbon metabolites.

182 Converting spring-born heifers into a summer-calving herd increases subsequent cow longevity and productivity

Abstract Developing replacement heifers is one of the most expensive and complex management decisions for a cow-calf producer, which also has long-term implications for profitability. The objective of this study was to determine the impact of converting spring-born heifers into a summer-calving herd on growth, reproductive performance, longevity, and productivity compared with early or late-born May heifers. Over a 3 yr period, Red Angus/Simmental crossbred heifers (n = 273) were utilized to determine the impact of converting March-born heifers (Convert; n = 90) to a May-calving herd compared with May-born heifers on reproductive performance, body weight (BW), and calf performance from a yearling to 5 yr of age. May-born heifers were retrospectively grouped into 2 different groups: heifers born in the first 21 d of calving as a heifer calf (Early; n = 123) or heifers born after the 21 d of calving as a heifer calf (Late; n = 60). Heifers were exposed to bulls for a 45-d breeding season with a bull-to-heifer ratio of 1:20. Heifers were synchronized with a single injection of prostaglandin F2α (5-mL i.m.; Lutalyse, Zoetis, Parsippany, NJ) 5 d after bulls were introduced in the pasture for breeding. Data were analyzed as a randomized design using the MIXED procedure (SAS Inst. Inc., Cary, NC, USA). All binomial data were analyzed using PROC GLIMMIX. Heifer served as the experimental unit with treatment and year developed set as fixed effects. Heifer BW at December, May, July, and pregnancy check (Oct) were greater (P < 0.01) for Convert heifers with no difference between Early and Late born heifers. Heifer BCS at pregnancy check was not different (P = 0.13) among heifer treatment groups. However, pregnancy rate tended (P = 0.08) to increase for Convert heifers with no difference between Early and Late born May heifers. After 5 yr of age, retention rate was increased (P = 0.04) in Convert cows compared with Early and Late May-born cows with no difference (P = 0.84) between the two May-born heifer groups. Total kilograms of calf weaned was greater (P = 0.04) in Convert cows than their counterparts with no differences (P = 0.94) between Early and Late May-born cows. This study implies that selecting replacement heifers from an earlier calving season for replacements in a later calving season increases the longevity and long-term productivity of the cowherd than selecting heifers within the same calving season. This may be even more important in resource-poor breeding environments that create reproductive challenges for heifers and rebreeding young cows.

52 Differences in body composition measurements for developing Angus heifers

Abstract The profitability of beef cow-calf operations relies on the reproductive ability of females to calve at 2 yr of age and provide a calf each subsequent year for her lifetime. The management of replacement heifers could affect her ability to conceive early, calve, and rebreed. Common management practices use heifer body weight (BW) (and body condition score (BCS) as indicators of puberty onset but do not indicate body composition and fat deposition. The objective of this study was to use ultrasound measurements of carcass traits to compare the effect of different diet management practices on muscle development and fat deposition of post-weaning heifers. The heifers placed on a higher energy diet are expected to have greater mean carcass trait measurements than the lower energy diet heifers. A total of 124 purebred Angus heifers from the Iowa State University McNay Memorial Research and Demonstration Farm were used for this study. Two diets were administered in this study. One group of heifers (G1; n = 61) was developed on a low-energy roughage diet to reach a target BW of 55% of mature BW at the time of breeding. The second group (G2; n = 63) was developed on a grain diet to reach the target BW of 65% mature BW at breeding. Body weight and ultrasound measurements for backfat (BFAT), ribeye area (REA), and intramuscular fat (IMF) were collected over three time points (0-d, 55-d, and 123-d) during the study to quantify the development of body composition characteristics. The initial measurements were collected 1 wk post-weaning. Significant mean differences between the two groups were observed for BW, BFAT, and REA at 55-d (P = 0.027, P = 0.008, and P < 0.0001, respectively), and 123-d (P < 0.001). The mean differences for BW, BFAT, and REA at 123-d between G1 and G2 were 30.98 kg, 0.10 cm, and 7.81 cm2, respectively No significant difference was found between the groups for IMF measurements at 55-d (P = 0.927) or 123-d (P = 0.169). This suggests IMF is not significantly influenced by diet during the early, post-weaning heifer developmental stage. Although further research is needed, the results from this study suggest the development of weight, BFAT, and REA in early post-weaning beef heifers is influenced by the energy concentration of the diet.

Blood research of Simmental breed animals in the Carpathian region

Physiological and biochemical blood parameters in Simmental heifers in postnatal ontogenesis of different types of constitution are presented. The physiological and selection index was calculated on the basis of digital indicators of the intensity of transamination enzymes and body weight of heifers in the corresponding periods of growth. It is shown that at the age of 6 months it is possible to assess the young, in this case heifers, by the type of constitution. The number of erythrocytes in the blood of heifers at 6, 12, 18 months old in the experimental group was higher than that of the control ones by 4.25; 9.91; 9.82 %, respectively. On average, over the entire period of rearing, the animals of the experimental group exceeded the control counterparts by 7.92 %. In terms of hemoglobin content in the blood, the experimental heifers at the ages of 6, 12, 18 months exceeded the control counterparts by 8.20; 10.83; 10.90 %, respectively. On average, over the entire period of rearing, the animals of the experimental group exceeded the control counterparts by 7.64 %. In terms of total protein content in the blood serum, the heifers at the ages of 6, 12, 18 months old in the experimental group exceeded the control counterparts by 7.47; 15.23; 8.64 %. On average, over the entire growing period, the animals of the experimental group outnumbered the control counterparts by 8.09 %. Another important indicator, which also characterizes protein metabolism in the animal body, is the activity of aminotransferases in the blood serum. In terms of AST activity in the blood serum, on average over the entire period of growing animals, the experimental group exceeded the control group by 11.78 %. A similar pattern was found in terms of ALT activity in the blood serum. Thus, the heifers of the experimental group in terms of ALT activity in the blood serum at 6, 12, 18 months old exceeded the control peers by 4.72; 8.13; 8.01; 10.28 %, respectively. In terms of the content of total sulfhydryl groups in the blood of heifers of the experimental group at 6, 12, 18 months, they were superior to the control analogues by 10.85; 27.50; 23.44; 18.01 %, respectively. In terms of the content of residual SH-groups in the blood of animals of the experimental group in postnatal ontogenesis, they were superior to the control analogues by 24.34 %. Experimental heifers in terms of total glutathione content at the age periods of 6, 12, 18 months old exceeded control counterparts by 8.38; 20.25; 7.44; 5.48 %, respectively. A similar pattern was observed in terms of reduced glutathione content in the blood of experimental animals. Thus, in terms of reduced glutathione content in the blood of individuals of the experimental group for the entire period of cultivation, they exceeded control peers by an average of 9.56 %.

89 Evaluation of repeatability of anogenital distance measured with either a caliper or photogrammetry

Abstract The objective was to determine the repeatability of anogenital distance (AGD) measurements over time in growing heifers and evaluate the relationship of photogrammetric and caliper AGD measurements. Reproductive success is one of the most important determinants of profitability in the beef industry. However, fertility traits generally have low heritability, and there are few phenotypic traits that correlate to fertility in beef cattle. The AGD is the distance from the center of the rectum to the base of the clitoris. Recently, researchers in dairy cattle have reported a correlation between shorter AGD and improved fertility. In the published dairy research, AGD has been measured with the use of calipers. Photogrammetric measurement could be a quicker and safer way of taking the measurement and easier to implement on farm. Heifers (n = 153), either Angus or Hereford sired by commercial dams, were used in the analysis. Heifers were early weaned at 82 ± 7 d of age. Following weaning, heifers were managed in partially covered, dry lot pens and fed a moderate roughage growing diet. The heifers rotationally grazed predominantly tall fescue pastures beginning in April of 2023. Heifer AGD was evaluated monthly from June to September. Heifers weighed 210 ± 22 kg and 282 ± 6 d of age at the time of the first AGD measurements. Heifer body weight was collected monthly at time of AGD measurements. The heifers were restrained in a squeeze chute and had their tail held in a relaxed upright position and AGD was measured with a caliper. Immediately following caliper measurements, anogenital photographs were taken with an Iphone 14 plus. A white board with a forensic photomacrographic scale attached and the ear tag number recorded on the right corner was held adjacent to the vulva and was included in the photograph. Photographs were converted from HEIC to JPEG. A software program, Digitizer, was used to set the measurement scale using the forensic photomacrographic scale. The AGD was then digitally measured from the center of the rectum to the base of the clitoris. Repeatability of AGD and relationship of caliper and photogrammetric AGD were evaluated using the CORR procedure of SAS 9.4. Caliper AGD measurements were repeatable as all of the time points were moderately correlated (r ≥ 0.47; P ≤ 0.01) throughout the evaluation period. Photogrammetric AGD measurements were also repeatable as all of the time points were correlated (r ≥ 0.21; P ≤ 0.02) throughout the evaluation period. Photogrammetric AGD had a moderate correlation (r ≥ 0.44; P ≤ 0.01) with the caliper AGD measurements. In conclusion, AGD measurements were repeatable in growing heifers regardless of measurement method. Photogrammetric measurements may be a viable option for estimating AGD as they were strongly correlated to caliper measurements of AGD.

PSII-7 Effect of endophyte-infected tall fescue on body weight, vital signs, and liver function of beef heifers

Abstract Tall fescue was first introduced to the United States over 70 years ago. Since then, it has become the most common forage source for beef cattle in the Southeastern region of the US. Most tall fescue establishes a symbiotic relationship with a toxic fungal endophyte (Epichloë coenophiala), which contributes to the improved vigor of the plant due to acquired resistance to grazing, insects, heat, and drought. However, when consumed by cattle, it may cause fescue toxicosis, a condition characterized by reduced feed intake, body weight (BW) loss, vasoconstriction, and impaired reproductive performance in livestock species. Therefore, the aim of this study was to investigate the effect of endophyte-infected tall fescue consumption on growth performance and health-related traits in beef cattle. For this purpose, 24 Simmental x Angus heifers were divided into two dietary treatments, in which 12 heifers received endophyte-free tall fescue seeds (E-) and 12 heifers were fed with endophyte-infected tall fescue seeds (E+, 6,764 ppb of ergovaline) mixed with the diet for 45 d. The E+ heifers received a daily dose of 20 μg of ergovaline per kg of BW. The E- heifers received the same quantity of seeds as the E+ heifers. For each heifer, phenotypes related to growth (BW), vital signs (respiration rate [RR], and body temperature [TEMP]), and liver functions (serum albumin [ALB], alkaline phosphatase [ALP], aspartate aminotransferase [AST], gamma-glutamyltransferase [GGT], cholesterol [COL], bilirubin [BIL], and triglycerides [TRI]) were analyzed at the end of the experiment. Phenotypes were analyzed using a linear model in R with diet included as a fixed effect. For analysis of BW, the BW at the beginning of the trial was included in the model as a covariate. Results showed that COL and ALP were significantly less (P < 0.05) in the E+ heifers compared with the E- (-32.92 ± 11.16 mg/dL and -32.33 ± 13.95 U/L, respectively). Conversely, E+ heifers had greater (P < 0.05) BW, RR, TEMP, and AST when compared with E- heifers (-17.82 ± 5.12 kg, 25.83 ± 5.52 breaths/min, 0.56 ± 0.12 oC, and 5.83 ± 2.18 U/L, respectively). Measurements of ALB, BIL, GGT, and TRI were not different between E+ and E- heifers. Our results suggest that heifers consuming endophyte-infected tall fescue have compromised vital signs and metabolically altered liver, which may impair growth performance. This study increases our understanding of the biological mechanisms affected by the fescue toxin in beef cattle.

Rate of body weight gain during early gestation in F0 beef heifers has effects that extend multigenerationally to the F2 fetuses.

Our aim was to investigate the effects of maternal (F0) body weight (BW) gain during the first 84 d of gestation on body composition, ovarian reserve, and hormonal and metabolic parameters of breeding-age F1 heifers, as well as the BW and morphometry of F2 fetuses. The study also evaluated the effect of maternal BW gain (F0) on the mRNA relative abundance of the small intestine of both F1 heifers and F2 fetuses. Crossbred Angus heifers (F0; n = 100) were managed to gain 0.20kg/d (low gain [LG], n = 50) or 0.75kg/d (moderate gain [MG], n = 50) for the first 84 d of gestation. Subsequently, F0 dams were managed on a common forage-based diet for the rest of gestation until the weaning of the F1 offspring. At 15 mo of age, a subset of F1 heifers was randomly selected for the current experiment (n = 8 LG and n = 8 MG). Heifers were bred via artificial insemination (AI; day 0), then harvested on day 84 of gestation. On days -10, 42, and 84, BW was recorded, and blood was collected and analyzed for concentrations of glucose, non-esterified fatty acids, progesterone, insulin, and insulin-like growth factor-1. The weight of F1 carcasses, organs, gravid uteri, and F2 fetuses and organs were recorded at harvest. Visible follicles were counted on F1 ovaries at harvest, and histology was used to count microscopic follicles. Liver and jejunal samples from F1 heifers were collected to measure tissue oxygen consumption and jejunal samples from F1 heifers and F2 fetuses were collected for mRNA relative abundance analysis. BW of F1 heifers from MG dams tended to be 12kg greater (P = 0.06) than for F1 heifers from LG dams. Concentrations of glucose were greater (P = 0.03) in F1 heifers from the MG group, with no differences in other blood metabolites or follicular populations (P ≥ 0.16). Interestingly, mammary glands were heavier (P = 0.05), and placentas and body depth tended to be heavier and greater, respectively (P ≤ 0.10), for F2 fetuses from F0 LG heifers. Oxygen consumption in the liver and jejunum, as well as mRNA relative abundance in the jejunum of F1 heifers, were not affected by F0 rate of gain (P ≥ 0.16). However, the NDUFC1, SDHA, UQCR1, and PPARG genes were upregulated (P ≤ 0.05) in the jejunum of F2 fetuses from the LG group. In conclusion, BW gain of F0 heifers during early gestation exerts subtle effects on pre-breeding BW and blood metabolites in F1 offspring, with impacts present in F2 placenta, mammary gland, and intestine.

AGE DYNAMICS OF CHANGES IN LINEAR GROWTH PARAMETERS OF REPLACEMENT HEIFERS UNDER DIFFERENT APPROACHES TO THE ORGANIZATION OF THEIR FEEDING TECHNOLOGY

The dynamics of changes in body weight and parameters of linear growth of replacement heifers of the Ukrainian black-and-white dairy breed under different approaches to the organization of their feeding technology were studied. The research was conducted on replacement heifers of the Ukrainian black-and-white dairy breed with a body weight of 170 kg, since they were 6 months old. For the formation of the experimental groups, different approaches to the organization of their feeding technology were used, namely, heifers of the control group received a diet that included corn silage. In feeding the animals of the second and third (experimental) groups, respectively, 50% and 100% of such silage was replaced by mixture of corn and sorghum. After analyzing the silage used in the experiment, no significant differences in their chemical composition were found. Therefore, the use of silage prepared from the green mass of compatible crops of corn and sorghum as part of the diets of replacement heifers did not have a significant effect on changes in their nutritional value and the content of nutrients in them, as well as the content of crude protein, provided that detailed feeding standards are met. In particular, the increase in the content of crude fiber, based on 1 kg of dry matter of the diets, was 3 and 6 g, respectively, in the animals of the second and third groups. In the course of the experiment, no significant and probable difference was established in terms of the increase in body weight of replacement heifers from the control and experimental groups. However, at the end of the experiment, a statistically significant difference in growth intensity was established between the animals of Group III (experimental) and Group I (control), while the differences between the latter and Group II (experimental) increased to the trend level. In particular, an increase in average daily gains of heifers of experimental groups, compared to animals of the control group, on the fourth and fifth months of the experiment, respectively, by 4.0 and 6.4% and by 5.2 and 11.2% (р≤ 0.05). It was also established that the use of both traditional corn and corn and sorghum silage in the organization of animal feeding technology accelerates the achievement of economic maturity by heifers. It was determined that the body weight of replacement heifers, from the age of eight months, exceeded the requirements of the breed standard. In particular, the body weight of 8-month-old heifers was higher than the standard by 5.0 – 10.2 kg or 2.4 – 4.9%, at the age of 9 months it was higher by 11.0 – 15.7 kg or 4.8 – 6 .9%, at the age of 11 months it was higher by 30.2 – 33.0 kg or 11.4 – 12.4%. The variability and level of body structure indices in the age dynamics of experimental animals of the Ukrainian black-and-white dairy breed proved the positive dynamics of the formation of the exterior in the direction of the dairy type. Thus, the obtained results proved the expediency of using corn and sorghum silage in the technology of rearing replacement heifers.

Efficiency of tissue biostimulant application in growing heifers

The materials of research on the effectiveness of tissue biostimulant application in the technology of breeding replacement heifers are presented. The experiment was conducted in the conditions of the Altai Territory on four groups of heifers of the Priobsky type of the Black-and-White breed with a live weight of 51.3 ± 1.48 kg at the age of 1 month. Each group had ten heads. The experiment lasted for 18 months. Animals of the control group were injected subcutaneously with physiological solution every month: from the 1st to the 5th month – at a dose of 3.0 ml/head, from the 6th to the 11th month – 6 ml/head, from the 12th to the 15th month – 12.0 ml/head and from the 16th to the 18th month – 15.0 ml/head. Injections of tissue biostimulant were given to the heifers of the experimental groups according to the following schemes: in the 1st experimental group – from the 1st to the 5th month – at a dose of 2.0 ml/head, from the 6th to the 11th month – 4 ml/head, from the 12th to the 15th month – 8.0 ml/head and from the 16th to the 18th month – 10.0 ml/head; in the 2nd experimental group – from the 1st to the 5th month – at a dose of 3.0 ml/head, from the 6th to the 11th month – 6 ml/head, from the 12th to the 15th month – 12.0 ml/head and from the 16th to the 18th month – 15.0 ml/head; in the 3rd experimental group – from 1st to 5th month – at a dose of 4.0 ml/head, from the 6th to the 11th month – 8.0 ml/head, from the 12th to the 15th month – 16.0 ml/head, from the 16th to the 18th month – 20.0 ml/head. Biostimulant is made of slaughter house tankage and by-products of the antler deer. The scheme of its application, used in the 2nd experimental group of animals, was the most effective and contributed to the increase in body weight in repair heifers up to 14% (p ˂ 0.001), average daily gain – up to 33% (p < 0.001), absolute gain – up to 23% (p ˂ 0.001) and relative gain – up to 2% (p < 0.05).

Physiological Correlates of Holstein Heifer Body Weight: Implications for Management

The purpose of this study was to predict arid and semi-arid of heifer body characteristics using physiological data. Twenty heifers were weighed on an electronic scale, and heart girth (HG) was recorded. Blood samples were collected from the jugular vein, and serum was harvested. Blood parameters such blood urea nitrogen, BUN; glucose, Glc; and total protein, TP. In addition, blood hematological indices (red blood cells, white blood cells, lymphocytes, and hemoglobin) were measured. The growth of the body has resulted in an increase in weight, which has been steadily climbing over time. The body weight was ranged between 319 and 328 kg. There was no correlation between any of the physiological parameters and the live weight of the animals. While, there was a significant inverse correlation (P<0.001) between total protein and the vast majority of the other parameters. The multiple regression analysis shows a direct relationship between Glc and BUN as independent influencing factors on the characteristic that was being studied, which was body weight. Furthermore, with an average GLc measurement, the body weight rose by approximately 8. Overall, physiology as a predictor may be applied. Though, it is not sufficient for predicting live weight.

318 The Effect of Developing Heifers to a Lower Percentage of Mature Body Weight at Breeding on Pregnancy Rates and Longevity Within the Herd

Abstract Traditional recommendations suggest that a heifer should be at 65% of her mature body weight (BW) at the time of breeding to obtain optimal production efficiency and achieve the greatest pregnancy rates. The objective of this study was to determine how developing heifers at a decreased percentage of mature BW at breeding impacts heifer performance, stayability, and calf production. Data were collected from cows and heifers (n = 1,434) from the March- and May-calving herds at the University of Nebraska Gudmundsen Sandhills Laboratory (GSL) located near Whitman, NE from 2005 through 2019. Body weights were collected from heifers and cows, percentage of mature BW of heifers was calculated using heifer breeding weight and the average MBW of cows at 5, 6, and 7 years of age. A regression analysis was conducted on percentage of estimated mature BW at breeding in heifers from 50 to 70 % of mature BW. Heifers that were 60% of mature BW at the time of breeding or greater had increased (P &amp;lt; 0.01) pregnancy rates compared with lighter heifers. In contrast, a greater percentage (P = 0.05) of heifers at a mature BW of 60% or less at breeding calved during the first 21 d of the calving season. Calf BW at birth was influenced (P &amp;lt; 0.001) by percent of mature BW at breeding with calves from greater BW heifers being heavier. Subsequent pregnancy rate as a 2-yr old was influenced (P &amp;lt; 0.001) by percentage of mature BW at breeding as a heifer with greater percent mature BW at breeding having greater pregnancy rates than heifers with decreased percent mature BW. However, pregnancy rate as a 3-, 4-, and 5-yr-old were not influenced (P&amp;gt; 0.15) by percentage of mature BW at breeding as a heifer. Overall, greater percentage of mature BW at the time of breeding increased overall pregnancy rate; however, heifers at a decreased percentage of mature BW calved at a greater percentage during the first 21-d of the subsequent calving season. In addition, longevity in the cowherd was not influenced by heifer BW at the time of breeding.

95 Predicting Live Body Weight of Beef Heifers Using 3D Imaging

Abstract Accurately measuring body weight (BW) is of great importance for cow-calf producers in the United States, which can lead to better marketing and nutrient management decisions. Traditionally, BW has been recorded using a walk-over scale or approximated by visual observation. Recently, technology has come out that allows BW prediction using three-dimensional (3D) images. The objective of this study was to determine the efficacy of 3D imaging technology as a method to predict BW of beef heifers. Dorsal 3D images were collected on 69 Red Angus/Simmental yearling heifers. Heifers were approximately 12 mo of age that ranged from 282.1 to 440.0 kg of BW. For image collection, a depth camera (Kinect Azure, Microsoft) was placed above the animals, approximately 3 to 4 meters above the floor surface within the alley of a working facility. The image collection software was written in Python (version 3.8) programming language. For a high-quality image to be recorded, heifers needed to be handled in small groups and kept separate. Heifers also needed to have all four feet on the ground and no interference from other animals in the image. Corresponding scale-measured BW were also recorded for each animal concurrent with depth images collection. Heifers were limit fed and weighed in the morning before feeding for both scale measured BW and image collection. The depth images were analyzed using a customized program written in MATLAB (R2022a). Heifer dorsal projected volume was estimated by adding height pixel values that formed the heifer’s dorsal area, excluding the head region. Body weights were regressed from projected heifer body volumes extracted from the depth images, and then metabolic BW (MBW) was calculated using the 0.75 power adjustment of BW. Performance of the prediction model was analyzed using the coefficient of determination (R2) obtained from the regression of projected volume and actual scale BW and the standard error of the mean (SEM) of the predicted BW. Data were analyzed using the PROC REG and PROC CORR procedures in SAS (v9.4). Prediction of BW using image-extracted dorsal projected volume produced an R 2 = 0.89 and SEM = 3.3 kg. When analyzing the correlation of volume to BW, the Pearson correlation coefficient of r = 0.94 (P &amp;lt; 0.0001) was obtained. Regression of projected volume to MBW produced an R 2 = 0.89 and SEM = 0.57 kg. Results show that this model demonstrates the ability to accurately predict BW using depth images projected dorsal volumes on yearling heifers. These results illustrate that 3D images can be used to accurately measure BW of growing heifers that may enhance the ability of cow-calf producers to pro-actively manage grazing livestock.

267 Efficacy of Using the Elastic net Regularized Regression Method to Predict Body Weight of Beef Heifers Using Body Measurements and Calculated Frame Score

Abstract Several methods to estimate the body weight (BW) of cattle have been proposed. Body measurements have proved to be useful in estimating the BW of cattle. However, there are multicollinearities between body measurements which could affect the accuracy of prediction models. Least absolute shrinkage and selection operator (LASSO regression), ridge regression, and more recently elastic net (EN) regularization has been suggested to handle multicollinearity better than simple regression. Elastic net is a regularization technique that combines LASSO and ridge regression. In this study, we modelled BW against some body measurements [calculated: volume (VL) 218 to 503 liters; frame score (FS) 2.1 to 7.5; surface area (SA) 4.02 to 7.1 m2], and direct body measurements [body length (BL) 89 to 136 cm; hip height (HH) 96 to 136 cm; hip width (HW) 33 to 52 cm; heart girth (HG) 149 to 191 cm; mid girth (MG) 177 to 234 cm; flank girth (FG) 156 to 239 cm] to examine which variable(s) predicts BW more accurately. Data from 300 heifers (9 breeds) collected over 4 years were used with year as a random effect to account for differences between years. We ran the EN model using the glmnet function of the R caret package. Ten-fold cross validation was used with 5 repeats. The EN model was trained using 206 observations and validated with 94 observations. The best model was selected based on the minimum root mean square error and median R-square (R2) values. Including FS in the prediction model resulted in the highest R2 (0.5754) and was a better predictor for BW compared with other models: VL (0.4271), SA (0.4130) and direct body measurements (0.4861). This suggests that calculated FS could be a better estimate for BW than direct body measurements and indicates that FS still accurately predicts size of heifers.

Effect of delayed timing of artificial insemination with sex-sorted semen on pregnancy per artificial insemination in synchronized dairy heifers managed in a seasonal-calving pasture-based system

The objective of this study was to evaluate the timing of artificial insemination (AI) with frozen-thawed sex-sorted semen on pregnancy per AI (P/AI) in dairy heifers. A 6-d progesterone Co-Synch protocol was used for ovulation synchronization of dairy heifers, with timed AI (TAI) coincident with (TAI-0) or 8 h (TAI-8) after the second injection of GnRH, corresponding to either 48 h or 56 h after removal of the progesterone-releasing intravaginal device. Pregnancy diagnosis was conducted by transrectal ultrasound scanning of the uterus 34 d after TAI (n = 816 records available for analysis). Generalized linear mixed models were used to examine the effects of treatment on P/AI. Treatment (n = 2), herd (n = 11), and treatment × herd were included as categorical fixed effects. Heifer body weight and Economic Breeding Index values for milk production, fertility, calving performance, beef carcass, cow maintenance, cow management, and health were included as continuous fixed effects. Heifer ID was included as a random effect. Pregnancy per AI was greater for TAI-8 heifers (59%) compared with TAI-0 heifers (50%). Pregnancy per AI ranged from 38% to 75% between herds but there was no treatment × herd interaction. The fertility subindex (positive) and the cow management subindex (negative) were the only continuous animal variables associated with P/AI. Delaying the timing of AI with frozen-thawed sex-sorted semen by 8 h in dairy heifers enrolled on a 6-d progesterone Co-Synch protocol improved P/AI.

The effects of feeding hempseed cake on pancreatic and jejunal digestive enzymatic activity in finishing heifers

To evaluate the effects of feeding hempseed cake on digestive enzymes, crossbred heifers ( n = 32; 494 ± 10 kg body weight) were fed diets containing 20% (dry matter basis) dried corn distillers grains plus solubles or hempseed cake for 111 days. There was greater ( P = 0.05) pancreatic mass relative to body weight in heifers fed hempseed cake. No differences ( P ≥ 0.19) in digestive enzyme activity in the pancreas (α-amylase, trypsin, and lipase) and jejunum (maltase, glucoamylase, and isomaltase) were observed between treatments. Our results suggest that feeding hempseed cake did not influence digestive enzyme activity.

Does the mycotoxin ingestion by beef heifers on feedlot change the productive parameters?

In intensive beef cattle production systems, silage, corn, soy bean, and their coproducts are commonly used as feed. However, these ingredients are highly susceptible to contamination by fungi and mycotoxins, which may lead to immunological challenges and reduce animal production. The aim of the present study was to evaluate the effects of mycotoxin contamination of diet on intake, digestibility, and performance of heifers. Twenty non-pregnant (Nellore) heifers (age, &gt;18 months; initial body weight, 348±30 kg) were used and randomly distributed in two treatments: (1) control (non-contaminated diet) and (2) zearalenone-contaminated diet (300 ppb). The diet comprised 70% corn silage and 30% concentrate. Individual dry matter intake and digestibility were estimated using external and internal markers. Heifer body weight was evaluated every week without fasting to calculate performance. The experimental design was completely randomized. Each animal was considered one experimental unit. Assumptions were tested for variance analyses (error normality, independence of errors, and homogeneity of variances) (p&lt;0.05). There were no differences in dry matter intake (p=0.96) and digestibility (p=0.62). Performance (kg/day) did not vary as a function of zearalenone ingestion (p=0.68). Therefore, contamination of diet with 300 ppb zearalenone did not affect the intake, digestibility, and performance of feedlot-finished heifers.

ВЫРАЩИВАНИЕ ТЕЛОК МОЛОЧНОГО НАПРАВЛЕНИЯ

This article shows the results of scientific research on raising the Holstein-Friesian heifers from birth to 12 months of age, with the introduction to their feeding regimen of "Neomilk" whole milk replacer, as well as the "Gavryusha" commercial prestarter and starter during the preweaning period and the extruded feed called "NFT KATU," produced by S. Seifullin Kazakh Agrotechnical Research University during the preweaning and postweaning periods. Three groups of calves were formed using a pair-matching method for the main research. Studies on body weight dynamics were conducted at the Aina Dairy Farm LLP with the calculation of daily average, relative, and absolute weight gains. At three months of age, the body weight of heifers in the second test group exceeded that of the control and the first test group by 7.8 kg (8.8%) and 6.8 kg (7.7%), respectively. At six months of age, the difference increased to 34.4 kg (30.7%) and 23.4 kg (19.2%). By 12 months of age, the gap widened to 106 kg (47.3%) and 77 kg (33.4%). Outline characteristics were also analyzed by taking measurements and calculating body condition indexes of the heifers. An analysis of the feeds used in animal feeding was conducted. The chemical composition analysis of the feeds revealed that the extruded feed had the highest protein content reaching 12.9%, which was 2.8% and 1.5% more than bran and "Gavryusha" prestarter, respectively.