Growth Of Dairy Heifers Research Articles

Limit feeding total mixed rations exacerbates intersucking in year-old dairy heifers

Limit feeding is a practice that is used to improve feed efficiency and control growth in dairy heifers, but also has negative consequences due to hunger and restriction of feeding behavior. One such consequence could be intersucking, i.e., the licking or sucking of another animal's teats or udder. This behavior is reported to varying degrees in heifers, and thus our first objective was to evaluate if intersucking increased in response to short-term (48 h) feed restriction. Intersucking interventions, such as nose rings, are often applied to specific animals, and so our second objective was to describe intersucking performance in individual heifers, including those that represent outliers in this population. We studied 42 heifers (9 Jerseys, 33 Holsteins) aged 12.8 ± 1.1 mo (mean ± SD). They were housed in pairs, resulting in n = 21 for our 1st objective. We used a switchback design with 3 periods of 2 d each where heifers were fed ad libitum TMR in the 1st and 3rd periods (Baseline, Return), and limit fed to 50% of ad libitum intake in the 2nd (Restriction). We scored time spent intersucking continuously and eating at 5-min intervals from video recordings from 0800 to 2000 on 4 d (Baseline d 2, Restriction d 2, Return d 1, and Return d 2). Heifer pairs spent less time eating (16 ± 0.4% mean percentage of 12-h observations ± SE), more time intersucking (27 ± 7 s/12 h), and engaged in longer bouts of intersucking (23 ± 5 s/bout) on Restriction d 2 compared with all other days (eating: 34.7 ± 1.1, 44.2 ± 0.9, 35.8 ± 1.1% of 12-h; intersucking time: 7 ± 2, 7 ± 3, 10 ± 5 s/12 h; intersucking bout length: 3 ± 1, 2 ± 1, 3 ± 1 s/bout; Baseline d 2, Return d 1, Return d 2, respectively). There was no difference in the number of bouts of intersucking across days (1.3 ± 0.2 bouts/12 h). The drop in eating during feed restriction was followed by a rebound on Return d 1 before returning to baseline levels. Time spent intersucking did not differ among ad libitum periods. Overall, 90% of the heifers performed intersucking on at least 1 of the 4 d, and did this for 1-127 s/12 h (range) in 1-13 bouts/12 h. Of the heifers that intersucked, 55% did this at extreme levels relative to the rest of the experimental population (outliers). Solid feed restriction exacerbated intersucking in year-old heifers, but this behavior was widespread.

Monitoring dairy heifer growth through control charts

The efficiency of replacement programmes in dairy farms depends largely on the heifers’ growth rate. We provide a case study of control chart application to monitor the weight of dairy replacement heifers. A research dairy farm in Córdoba province, Argentina, provided the monthly samples of BW measurements of 2, 9, and 14.5-month-old heifers born between 2017 and 2019. The data were used to build control charts for the mean and for SD, with moving range control limits in order to consider varying sample sizes. In each age group, control charts for the mean showed at least one out-of-control sample, whereas control charts for SD showed one sample out of control for 9-month-old heifers. Each sample outside the control limits implies that a potentially identifiable cause has occurred. Therefore, the producer could identify the event causing the deviation and make the necessary changes according to the heifer’s age. Control charts provide the producer and consultant with graphical information and quick alerts to support the decision-making process of the replacement programme. These tools are useful at the farm level to monitor heifer weights and support management decisions.

Live Weight and Bone Growth from Birth to 23 Months of Age in Holstein–Friesian, Jersey and Crossbred Heifers

Selection pressure for greater milk solid production, calving ease and early puberty attainment has resulted in the alteration of the growth trajectory of New Zealand dairy heifers. Although previous data have looked at stature growth in terms of height and girth, changes in the growth trajectory as a result of seasonal growth has not been examined. In addition, the relative contributions of the appendicular skeleton and thorax in relation to height have not been considered in previous studies. Therefore, the aim of this study was to examine how the proportional contributions of stature change with increases in live weight in Holstein–Friesian, Jersey and Holstein–Friesian–Jersey crossbred heifers from birth to 23 months of age (just prior to calving). Comparisons of height, length, girth and distal and proximal forelimb length (stature) revealed that at the same live weight, measures of girth, length and height did not differ between breeds (p < 0.05). As live weight increases, the relative contribution of the distal limb to increasing height decreases, which is consistent with the cessation of physeal growth occurring earlier in the bones of the distal limb than in the proximal limb. By understanding the timing of proximal and distal growth in dairy heifers, the effect of seasonal growth on longitudinal bone growth can be identified.

Modelling growth in dairy heifers based on linear body measurements (withers height) using non-linear functions.

This research communication reports a study to model the growth curves for withers height (WH) and body weight (BW) to withers height ratio (BW:WH) using monthly records (from 1 to 24 months of age) for three breeds of dairy heifer (Holstein, Jersey and Brown Swiss). The data sets used were those reported by the Dairy Heifer Evaluation Project of Penn State Extension (USA) between 1991 and 1992. Four growth functions (monomolecular and Michaelis-Menten, both with diminishing returns behaviour, and Schumacher and López, both with asymptotic sigmoidal behaviour) were fitted using the non-linear regression procedure of the SigmaPlot software and the parameters estimated. The models were judged for goodness of fit using adjusted coefficient of determination ($R_{{\rm adj}}^2 $), root mean square error (RMSE), Akaike's information criterion (AIC) and Bayesian information criterion (BIC). Assessing the goodness of fit by $R_{{\rm adj}}^2 $ (>0.99 in all cases) reveals the generally appropriate fit of the models to the data. The non-sigmoidal functions (i.e. Michaelis-Menten and monomolecular) provided the best fits giving the lowest values of RMSE, AIC and BIC. Based on the chosen statistical criteria, the Schumacher and López equations provided acceptable fits to the WH and BW:WH growth curves, but showed points of inflexion at times before birth, indicating that these growth curves are not sigmoidal. In conclusion, evaluation of the different non-linear growth functions used in this study indicated their potential for modelling growth patterns in dairy heifers.

Effect of diet energy level and genomic residual feed intake on bred Holstein dairy heifer growth and feed efficiency

The objective of this study was to determine growth, feed intake, and feed efficiency of postbred dairy heifers with different genomic residual feed intake (RFI) predicted as a lactating cow when offered diets differing in energy density. Postbred Holstein heifers (n = 128, ages 14-20 mo) were blocked by initial weight (high, medium-high, medium-low, and low) with 32 heifers per block. Each weight block was sorted by RFI (high or low) to obtain 2 pens of heifers with high and low genomically predicted RFI within each block (8 heifers per pen). Low RFI heifers were expected to have greater feed efficiency than high RFI heifers. Dietary treatments consisted of a higher energy control diet based on corn silage and alfalfa haylage [HE; 62.7% total digestible nutrients, 11.8% crude protein, and 45.6% neutral detergent fiber; dry matter (DM) basis], and a lower energy diet diluted with straw (LE; 57.0% total digestible nutrients, 11.7% crude protein, and 50.1% neutral detergent fiber; DM basis). Each pen within a block was randomly allocated a diet treatment to obtain a 2 × 2 factorial arrangement (2 RFI levels and 2 dietary energy levels). Diets were offered in a 120-d trial. Dry matter intake by heifers was affected by diet (11.0 vs. 10.0 kg/d for HE and LE, respectively) but not by RFI or the interaction of RFI and diet. Daily gain was affected by the interaction of RFI and diet, with low RFI heifers gaining more than high RFI heifers when fed LE (0.94 vs. 0.85 kg/d for low and high RFI, respectively), but no difference for RFI groups when fed HE (1.16 vs. 1.19 kg/d for low and high RFI, respectively). Respective feed efficiencies were improved for low RFI compared with high RFI heifers when fed LE (10.6 vs. 11.8 kg of feed DM/kg of gain), but no effect of RFI was found when fed HE (9.4 vs. 9.5 kg of DM/kg of gain for high and low RFI, respectively). No effect of RFI or diet on first-lactation performance through 150 DIM was observed. Based on these results, the feed efficiency of heifers having different genomic RFI may be dependent on diet energy level, whereby low RFI heifers utilized the LE diet more efficiently. The higher fiber straw (LE) diet controlled intake and maintained more desirable heifer weight gains. This suggests that selection for improved RFI in lactating cows may improve feed efficiency in growing heifers when fed to meet growth goals of 0.9 to 1.0 kg of gain/d.

The Mid-Diaphysis Is a Poor Predictor of Humeral Fracture Risk Indicating That Predisposing Factors Are Recent

The incidence of spontaneous humeral fractures in first-lactation dairy heifers in New Zealand has emphasised the need to understand the thoracic limb bone growth of dairy heifers. Previous research has indicated that a predisposing factor to spontaneous humeral fracture is nutrition. In addition, it has been hypothesised that liver copper concentration affects bone strength and may be a potential factor associated with humeral fracture risk. The aim of this study was to compare bone morphology in the mid-diaphysis of the metacarpus and humerus of heifers affected and unaffected by spontaneous humeral fractures, and determine the effect of copper status at death on bone morphology. The metacarpus and humerus were collected from heifers affected and unaffected by humeral fractures, and scanned using peripheral quantitative computed tomography (pQCT). The mid-diaphysis of the humerus of the affected group had reduced cortical bone mineral density and a trend for reduced cortical content and total bone content, which contributed to a reduced stress–strain index. The trend for reduced bone length in affected humeri provides additional support for the hypothesis of inhibited humeral growth. Heifers with low copper liver concentrations had reduced humerus lengths and reduced cortical bone mineral densities. These data support the hypothesis that the developmental window for humeral fracture is recent, and possibly associated with periods of inadequate nutrition.

Short communication: Development and evaluation of equations to predict growth of Holstein dairy heifers in a tropical climate

The objective of this study was to develop and validate equations for estimating growth of dairy heifers using measures of withers height, body weight (BW), and age. Measures of BW and withers height of 207 Holstein heifers raised in a tropical climate were taken from birth to calving, totaling to 2,047 observations. To be included in the database, the heifer had to have at least 4 measures recorded. After that, 4 models were built and evaluated as follows: (1) a linear model of BW as function of age (BW~A), (2) a linear model of the BW-to-height ratio as function of age (BW:H~A), (3) a quadratic model, adjusted for a defined plateau, to describe height as function of age (H~A), and (4) an exponential growth model of BW as function of height (BW~H). A cross-validation procedure was performed to evaluate accuracy and precision of the models. The linear relationship of BW~A and BW:H~A were estimated, respectively, by the equations: BW = 42.65 + 0.62 × A and BW:H = 0.70 + 0.0041 × A, where BW is in kilograms, BW:H = BW-to-height ratio (kg/cm), and A = age (d). Using the quadratic plateau for the model H~A, a critical "x" value of ~806 d and a height plateau of 138.6 cm were identified. Therefore, the following equations for estimating the height of animals younger and older than 806 d, respectively, were developed: H = 78.15 + 0.150 × A - 0.00009 × A2 and H = 78.15 + 0.150 × cvx - 0.00009 × cvx2, where H = height (cm) and cvx = 806 (critical "x" value; given in days). Additionally, the exponential model of W~H was estimated by the following equation: BW = 4.25 × exp(0.034 ×H), where BW is in kilograms and H = height (cm). A cross validation demonstrated that all equations had very high accuracy and precision. Overall, these models demonstrated that BW and BW-to-height ratio increase linearly as a function of age, while BW follows an exponential growth pattern as a function of height. Additionally, the H~A model predicted that heifers achieve a maximum height of 138.6 cm at 806 d of age.

Effect of forage source and dietary rumen-undegradable protein on nutrient use and growth in dairy heifers

Thirty-two Holstein heifers with mean (± standard error of the mean) age of 6.5 months (±0.12) and live weight (LW) of 166 kg (±1.6) were divided into four groups of eight animals to evaluate the effect of forage source and the concentrations of rumen-undegradable crude protein (RUP) in the diet with a 2 × 2 factorial design. As forage sources cowpea hay (Vigna sinensis L.) or pangola grass hay (Digitaria decumbens Stend) were added to the diet at 250 g/kg dry matter (DM). Also, 350 g/kg DM of chopped fresh King grass (Pennisetum purpureum Schum.) was included in all diets. The RUP proportions were 260 or 360 g/kg of total crude protein (CP). Heifers were housed in metabolism cages. The trial lasted ten weeks, with the first two weeks used for adaptation and the last week for data collection and sampling. Diets had a forage to concentrate ratio of 60:40 (on DM basis), and were offered as total mixed rations ad libitum. Fish meal or urea were used to produce varying concentrations of RUP at similar dietary CP content. Diet ingredients (i.e., hay, grass, and concentrate) and feces were sampled for nutrient analysis. Total collection of feces was performed to estimate apparent total tract nutrient digestibility (ATTD). Urinary purine derivative excretions were determined from urine spot samples to estimate rumen microbial protein synthesis. The effects of forage source, RUP, and its interactions were determined by general linear model analysis. Replacing dietary pangola grass hay with cowpea hay increased daily intakes of DM, organic matter, CP, acid detergent fiber (ADF), and digestible organic matter, and ATTD of DM, organic matter, neutral detergent fiber, and ADF (P < 0.05). Duodenal flow of RUP also increased when substituting cowpea hay for pangola grass hay (P < 0.01). Similarly, inclusion of cowpea hay in the diet improved live weight gain (LWG; P < 0.05), and decreased feed costs per kg of LWG (P < 0.01). The increase in RUP decreased rumen microbial protein synthesis (P < 0.01), but tended to increase LWG, feed conversion and nitrogen use efficiency, and feed costs per unit of LWG (P < 0.10). The use of cowpea hay in the diet of dairy heifers increases nutrient intake and ATTD, leading to improved LWG and lower feed costs per kilogram of LWG. Increasing RUP proportions may reduce rumen microbial protein synthesis, but may enhance LWG, feed conversion efficiency, and nitrogen use efficiency. There were no interactions between forage source and RUP proportion on intake and ATTD, but some synergistic effects were observed for the performance parameters.

Comparison of feeding diets diluted with sorghum-sudangrass silage or low-quality grass on nutrient intake and digestibility and growth performance of Holstein dairy heifers

This study was carried out to evaluate the nutrient intakes and growth of dairy heifers offered an alfalfa silage-corn silage diet (CON; 14.3% crude protein, 61.1% total digestible nutrients, 47.9% neutral detergent fiber) compared with diets containing 1 of 2 types of sorghum-sudangrass (SS) silages: conventional or photoperiod sensitive. The objective of the study was to determine the potential to use SS to control dry matter (DM) and nutrient intakes and weight gain. Both diets were similar in nutrient composition, with approximately 13% crude protein, 60 to 61% total digestible nutrients, and 55% neutral detergent fiber. Seventy-two Holstein heifers (16-18 mo at study initiation) were blocked by initial body weight (light = 422 ± 12.8 kg; medium = 455 ± 14.8 kg; heavy = 489 ± 16.7 kg) with 3 pens assigned to each weight block (8 heifers/pen; 24 heifers/block). The 3 diets were randomly allocated to the pens within each block and offered for 12 wk. Heifers offered the CON diet had greater DM, protein, and energy intakes compared with those offered the SS silage-based diets due to the greater neutral detergent fiber concentration of the SS diets. With lower DM and nutrient intakes, average daily gain was in the recommended range (0.8-1 kg/d for Holstein heifers) for heifers offered the SS silage-based diets (mean of 0.92 kg/d for both SS diets vs. 1.11 kg/d for CON). Sorting behaviors for heifers offered both SS diets were more aggressive against long, medium, and short particles compared with those of heifers offered the CON diet; however, heifers sorted large particles from photoperiod-sensitive silage more aggressively than those from conventional silage. Based on this study, SS silage-based diets can control the DM and energy intakes for heifers and maintain optimum growth rates, with harvesting at a shorter chop length likely helping to alleviate sorting issues.

Linear versus seasonal growth of dairy heifers decreased age at puberty but did not affect first lactation milk production

ABSTRACT The aim of this study was to compare conformation, age at puberty and subsequent milk production of Holstein–Friesian–Jersey crossbred heifers grown in a linear trajectory (Target; n = 55) between 6- and 15-month target liveweights (LWT), with heifers grown in a seasonal manner (Seasonal; n = 55) of slow over first winter and fast over spring. Heifers that grew to Target attained puberty 38 days earlier than heifers that grew in a seasonal manner; however, no difference between treatments in the date of first calving occurred. Heifers in the seasonal treatment were 1 cm (P = .032) taller than those in the target treatment, but similar in girth and length. There was no effect of treatment on first lactation milk production. These results suggest that provided heifers reached their pre-mating target LWT, the growth trajectory between target LWT at 6 and 15 months of age did not negatively impact frame size or first lactation milk production.

Body dimension comparisons between slick and wild type-haired Puerto Rican Holsteins

A previous study from our group evaluating growth in dairy heifers suggests that Puerto Rican Holstein slick-haired heifers (SLICK) could reach maturity earlier and at smaller body size than their wild type-haired (WT) counterparts. Thus, the present study aimed to determine if such differences exist in mature cows by comparing several body dimensions (i.e., body weight, withers height, hip height, thoracic perimeter, barrel, and shoulder to pin bone distance) of 24 SLICK and 54 WT lactating Holstein cows at the Agricultural Experiment Station in Lajas, Puerto Rico. Also, body weight was divided by each dimension to obtain the respective ratios. Data were analyzed by the GLIMMIX procedure of SAS. The SLICK cows presented larger barrels (236.54±2.68 vs. 231.06±2.29 cm; P=0.0363) and body weight / shoulder to pin bone distance (3.51±0.09 vs. 3.32±0.08 kg/cm; P=0.0218) than their WT counterparts. However, the shoulder to pin bone distance was smaller in SLICK than in WT cows (180.07±1.82 vs. 185.20±1.56 cm; P=0.0059). No significant differences between hair coat groups were observed in any other evaluated variable. The SLICK cows had shorter and deeper bodies than WT cows. Future studies should evaluate if such differences could impact their productive efficiencies.

Comparison of the effects of high and low milk-replacer feeding regimens on health and growth of crossbred dairy heifers

Context Pre-weaning growth in dairy heifers is highly dependent on the amount of milk fed. Both milk replacer (MR) and associated labour are costly, encouraging restricted milk rations and once-a-day feeding. Aims This study compared performance relating to the growth and health of calves receiving one of two commercial feeding regimens: High or Low. Methods All heifers born during the Spring (January–March) calving block on a commercial UK farm with mixed-breed genetics were recruited at birth, randomly assigned to the High (n = 104, receiving MR-A) or Low (n = 88, receiving MR-B) feed group and reared indoors on straw bedding, with free access to concentrate. Both groups initially received MR twice daily. The High group continued to receive MR twice daily throughout the experiment, whereas the Low group calves were reduced to a single MR feed daily during Weeks 4–8. Blood samples were taken in Weeks 1 and 6 to assess passive transfer and measure circulating insulin-like growth factor 1 (IGF1). The Wisconsin calf-scoring system was used to assess health of calves in Weeks 1, 2, 4, 6 and 8 and at 6 months and size was also measured at these times. Data were analysed by univariate and multivariate models. Key results Passive transfer was good in both groups (serum total protein (mean ± s.d.) 60.9 ± 9.1 mg/mL) with no differences in pre-weaning disease incidence; diarrhoea occurred in 64.5% and bovine respiratory disease in 26.3% of calves. High group calves were significantly heavier, taller and longer at all pre-weaning examinations except recruitment owing to more growth in the first month, and remained significantly larger at 6 months: weight 157 ± 8 vs 149 ± 7 kg, height 103 ± 5 vs 100 ± 5 cm, length 90 ± 4 vs 88 ± 5 cm. Plasma IGF1 concentrations at around Week 6 were doubled in the High group (101 ± 38.6 vs 55 ± 34.1 ng/mL). Bovine respiratory disease was associated with reduced weight gain. Heifers with diarrhoea were leaner at weaning. High feed group, weight at recruitment and good passive transfer were positively associated with weight at 6 months. Conclusions Higher feeding levels pre-weaning increased growth rates and IGF1, although the disease incidence was unaffected. Implications Previous studies have shown that more growth and higher IGF1 pre-weaning are associated with a lower age at first calving and an increased chance of reaching the end of first lactation. These in turn improve long-term performance.

Live weight and growth of Holstein-Friesian, Jersey and crossbred dairy heifers in New Zealand

ABSTRACTThe objective of this study was to model the growth of dairy heifers to estimate the effects of breed and heterosis on live weight (LWT) and growth from three to 22 months of age. Data comprised of 1,653,214 LWT records obtained from 189,936 dairy heifers in 1547 herds. At all ages Holstein-Friesian (F) heifers were heavier than Holstein-Friesian–Jersey crossbred (F × J) which were heavier than Jersey (J) heifers. Heterosis effects for LWT were greatest at nine months of age (3.6%) and least at 22 months of age (2.0%). The growth pattern differed, as evidenced by the regression coefficients of the Legendre polynomial. Growth was non-linear and heterosis effects were different throughout the growth period. Friesian, J and F × J heifers exhibited different growth patterns. These differences in growth pattern should be considered when formulating target LWTs and growth rates for a pasture-based system.

Post-weaning feeding levels on feeding behavior, growth and development in Holstein dairy heifers

ABSTRACT: To study the effect of post-weaning feeding levels on the growth of dairy heifers, 40 animals with 77.7 ± 8.1 days of age and 77.5 ± 9.2kg of body weight were grouped in 10 pens, and each pen was randomly assigned to one of the following treatments for 120 days: feeding level to achieve a body weight gain of 600 (TMEDIUM) or 800 (THIGH) g/day based on a total mixed ration. After this period all heifers were managed as a single group for 150 days. Nutrient intake, behavior, body weight and other morphological measures were recorded in each animal. As a result of the experimental design THIGH heifers had a higher nutrient intake than TMEDIUM heifers, which was reflected in a higher daily weight gain, withers height, heart girth and hip width. However, treatments had no effect on these traits during the residual period.

Growth performance and total-tract nutrient digestion for Holstein heifers limit fed diets high in distillers grains with different forage particle sizes

ABSTRACT This study evaluated dairy heifer growth performance and total-tract nutrient digestion when fed diets high in distillers dried grains with solubles with different forage particle sizes. An 8-wk randomized complete block design study was conducted using 22 Holstein heifers (123 ± 32 d of age; BW 140 ± 23.5 kg). Treatments were 15% chopped (CHOP) or 15% pelleted (PELL) alfalfa hay on a DM basis. Both diets also contained 30% distillers dried grains with solubles, 53.8% corn silage, and 1.25% mineral mix and were limit fed for DMI at 2.3% of BW. Growth measurements were taken every 2 wk, and jugular blood samples were taken every 4 wk. During wk 8, rumen samples were taken on 2 d via esophageal tubing to evaluate fermentation, and fecal grab samples were collected at 8 times over 3 d and composited by heifer to determine total-tract nutrient digestion. Heifer DMI increased with CHOP, and BW and ADG were similar between treatments. Feed efficiency was less in the CHOP-fed heifers. Frame measurements were similar, with the exceptions of paunch girth, heart girth, and hip width, which were greater for CHOP. The CHOP-fed heifers had less BCS than PELL. Rumen fermentation characteristics were similar; however, rumen pH was greater for PELL. Serum glucose and plasma cholesterol were similar between treatments, but plasma urea nitrogen tended to be greater in heifers fed CHOP. Total-tract digestibility of nutrients was similar between treatments. Results indicate that forage particle size minimally affects utilization of distillers dried grains with solubles by heifers.

744 Sire performance and reproductive breeding values are associated with feed efficiency and growth in dairy heifers

744 Sire performance and reproductive breeding values are associated with feed efficiency and growth in dairy heifers

043 Relationships Between Prolactin Genotypes and Dairy Heifer Growth and Development

043 Relationships Between Prolactin Genotypes and Dairy Heifer Growth and Development

Growth targets and rearing strategies for replacement heifers in pasture-based systems: a review

Dairy heifer growth and liveweight at first calving are regarded as important management variables affecting profitability and animal welfare. However, the appropriateness of heifer growth rate targets for different farming systems is not clear. Retrospective assessments of the association between heifer liveweight and subsequent productivity indicate significant benefits in milk production and, even, reproduction from increasing liveweight at breeding and first calving. However, prospective interventionist experiments do not concur, with very variable effects of liveweight at breeding on milk production and with only limited evidence of a positive effect of first-calving liveweight on first-lactation milk yield. In addition, any benefit in the first lactation is not evident in subsequent lactations in the limited number of long-term studies reported. Pre-weaning nutrition and average daily weight gain are areas of increasing interest, with lifelong increases in milk production resulting from accelerated growth rates during the first 8 weeks of life, indicating a possible significant return from a short-term investment. This could be one reason for the inconsistent effects of heifer liveweight at breeding and first lactation on milk production. Although the effect of pre-weaning average daily gain on heifer liveweight is short-lived, a recent meta-analysis indicated that pre-weaning average daily gain explains 22% of the variation in first-lactation milk production. Whether these differences in animal physiology have relevance in grazing systems, wherein heifers and cows do not consume sufficient nutrients to reach their potential, requires investigation. Despite considerable extension efforts over successive decades, current evidence indicates that failure to provide the new-born calf with sufficient high-quality colostrum is common. To understand the reasons for suboptimal colostrum feeding requires social research, with appropriate extension strategies developed to elicit practice change. Although there can be little doubt regarding the importance of heifer rearing to the profitability and sustainability of the farming business, the collective literature points to a failure of retrospective analyses in determining the cause of poor heifer performance. In reality, it is likely to be a combination of factors. The objective of this review is to investigate the effect of liveweight gain at various stages of the growth cycle of the heifer on the milk-production capacity of the lactating animal.

Intake and growth of prepubertal dairy heifers fed reduced-fat dried distillers grains

<h2>ABSTRACT</h2> Recent growth in the ethanol industry has led to increased availability of distillers grains that have undergone various processing methods resulting in differing nutrient composition. A modified dried distillers grains product with reduced fat due to removing oil through a solvent extraction process provides a new feed option for dairy heifers. The objective of this study was to evaluate intake, feed efficiency, and growth of dairy heifers fed diets containing reduced-fat dried distillers grains with solubles (RFDGS). Holstein heifers (n = 27), averaging 161 ± 9 d of age and 157.5 ± 11.4kg at the start of the study, were blocked according to BW and fed 1 of 3 dietary treatments. Dietary treatments included control, dried distillers grains fed at 20% of the diet DM, and RFDGS fed at 20% of the diet DM for 12 wk. Heifers were weighed every 2 wk to determine ADG. Hip and withers heights were measured on d 0, 42, and 84 of the study, and BCS were determined on d 0 and 84. Blood samples were collected via coccygeal venipuncture at the end of the study for determination of plasma urea nitrogen. In situ DM disappearance and intestinal CP disappearance were determined for feed and diet samples using lactating cows. Dry matter intake, BW gain, and feed efficiency were similar among treatments. In summary, inclusion of either DDGS or RFDGS at 20% of the diet resulted in similar intake, feed efficiency, and gains, and they are viable options for replacement dairy heifers.

Short term dietary propylene glycol supplementation affects circulating metabolic hormones, progesterone concentrations and follicular growth in dairy heifers

This study was designed to determine the effects of dietary propylene glycol (PG; Propypact®, DIFAGRI, France) on blood metabolites, metabolic and reproductive hormones and follicular growth in 10 dairy heifers. Treatments consisted of (1) 1.1kg of sugar beet pulp (Control), (2) 150g PG (PG150) and (3) 300g PG (PG300). Each heifer received the three treatments in different randomized orders. A standard hay/concentrate diet, formulated to allow a daily liveweight gain of 900g/day, was given at 8:00 and the dietary treatments were given at 16:00 from Days 1 to 13 of the oestrous cycle following induced oestrus (Day 0). Oestrus induction treatment consisted of a subcutaneous 3mg norgestomet implant inserted for 9 days combined with GnRH treatment (i.m.) at implant insertion. Two days before implant removal, 500µg cloprostenol was administered i.m. Blood samples were collected by jugular venipuncture every 2h for 24h on Days 0 and 13 to measure plasma insulin, glucose, β-hydroxybutyrate (BHB) and urea concentrations. Blood samples were also collected to measure insulin-like growth factor-1 (IGF-1), oestradiol, progesterone concentrations on Days 2, 6, 9 and 12 and AMH (Anti-Müllerian hormone) on Days 0, 2, 6, 9 and 12. On Days 2, 6, 9 and 12 ovarian follicular growth was evaluated; the total number of follicles and their diameters were recorded and classed (2–3mm, 4–7mm, and >8mm). Results were analysed by repeated-measures ANOVA. There were no treatment, day and interaction effects on average urea concentrations while there were some differences between Days 0 and 13 for insulin, glucose and BHB. Insulin and glucose concentrations were higher on Day 13 compared to Day 0 and the opposite was observed for BHB. There were treatment, time and interaction effects on glucose and BHB concentrations measured over 24h on Day 13; glucose concentrations were higher (P<0.05) at 4:00, 8:00, 12:00, 16:00 and 20:00h, whereas BHB concentrations were lower (P<0.05) at 20:00 and 22:00h in the PG300 group compared to the control and PG150 groups. There were treatment, day and interaction effects on IGF-1 and progesterone concentrations, and the number of small follicles. PG150 resulted in higher progesterone concentrations on Days 9 and 12, and more small follicles on Day 2 compared to Control. AMH concentrations were unaffected by day of oestrous cycle and dietary treatment. However a negative correlation was observed between pre-PG distribution insulin and AMH (r=−0.47, P<0.05). These results indicate that short-term dietary PG supplementation affects circulating concentrations of metabolites and metabolic hormones, increases progesterone concentrations and the number of small follicles. Propylene glycol supplementation may be effective in improving oocyte production when combined with hormonal treatments to stimulate follicular growth for superovulation or ovum-pick up.