Effect of intensified feeding of heifer calves on growth, pubertal age, calving age, milk yield, and economics

The objective of this study was to determine if increasing the energy and protein intake of heifer calves would affect growth rates, age at puberty, age at calving, and first lactation milk yield. A second objective was to perform an economic analysis of this feeding program using feed costs, number of nonproductive days, and milk yield data. Holstein heifer calves born at the Michigan State Dairy Cattle Teaching and Research Center were randomly assigned to 1 of 2 dietary treatments (n = 40/treatment) that continued from 2 d of age until weaning at 42 d of age. The conventional diet consisted of a standard milk replacer [21.5% crude protein (CP), 21.5% fat] fed at 1.2% of body weight (BW) on a dry matter basis and starter grain (19.9% CP) to attain 0.45 kg of daily gain. The intensive diet consisted of a high-protein milk replacer (30.6% CP, 16.1% fat) fed at 2.1% of BW on a dry matter basis and starter grain (24.3% CP) to achieve 0.68 kg of daily gain. Calves were gradually weaned from milk replacer by decreasing the amount offered for 5 and 12 d before weaning for the conventional and intensive diets, respectively. All calves were completely weaned at 42 d of age and kept in hutches to monitor individual starter consumption in the early postweaning period. Starting from 8 wk of age, heifers on both treatments were fed and managed similarly for the duration of the study. Body weight and skeletal measurements were taken weekly until 8 wk of age, and once every 4 wk thereafter until calving. Calves consuming the intensive diet were heavier, taller, and wider at weaning. The difference in withers height and hip width was carried over into the early post-weaning period, but a BW difference was no longer evident by 12 wk of age. Calves fed the intensive diet were younger and lighter at the onset of puberty. Heifers fed the high-energy and protein diet were 15 d younger at conception and 14 d younger at calving than heifers fed the conventional diet. Body weight after calving, daily gain during gestation, withers height at calving, body condition score at calving, calving difficulty score, and calf BW were not different. Energy-corrected, age-uncorrected 305-d milk yield was not different, averaging 9,778 kg and 10,069 kg for heifers fed the conventional and intensive diets, respectively. However, removing genetic variation in milk using parent average values as a covariate resulted in a tendency for greater milk from heifers fed the intensive diet. Preweaning costs were higher for heifers fed the intensive diet. However, total costs measured through first lactation were not different. Intensified feeding of calves can be used to decrease age at first calving without negatively affecting milk yield or economics.     

Long-term effects of ad libitum whole milk prior to weaning and prepubertal protein supplementation on skeletal growth rate and first-lactation milk production

Our objectives were to determine the effects of rapid growth rate during the preweaning period and prepubertal protein supplementation on long-term growth pattern and milk production during the first lactation. Forty-six Israeli Holstein heifer calves were fed either milk replacer (MR) or whole milk (WM) from 4 to 60 d age. Calves had free access to WM or MR for 30 min twice daily and free-choice water and starter mix for the entire day. From weaning until 150 d of age, all heifers were fed the same ration. At 150 d of age the heifers were divided into 2 subgroups, with one subgroup supplemented with an additional 2% protein until 320 d of age. Thereafter, all heifers were housed and fed together until calving. Another cluster of 20 heifers was raised on MR and WM treatments and 3 animals from each nursery treatment were slaughtered at 60 d and 10 mo age to determine effects of nursery treatment on organ and adipose tissue mass. Prior to weaning, the MR heifers consumed 0.12 kg/d more DM than the WM heifers, but metabolizable energy intake was not different. Body weight at weaning and average daily gain during the preweaning period were 3.1 kg and 0.074 kg/d higher, respectively, in the WM treatment than in the MR treatment, with no differences in other measurements. Nursery feeding treatment and added protein had no effect on growth rate in the prepubertal period, but the postweaning difference in BW between the WM and MR heifers remained throughout the entire rearing period. The age at first insemination was 23 d earlier and age at pregnancy and first calving was numerically lower for the WM heifers than for the MR heifers. Adipose tissue weights at weaning were doubled in the WM calves. First-lactation milk production and 4% fat-corrected milk were 10.3 and 7.1% higher, respectively, for WM heifers than for MR heifers, whereas prepubertal added protein tended to increase milk yield. In conclusion, preweaning WM at high feeding rates appears to have long-term effects that are beneficial to future milk production. The positive long-term effects of feeding WM on first-lactation milk production were independent of their effects on skeletal growth. Enhanced milk production observed with WM treatment may be related to the milk supply, paracrine or endocrine effects of fat tissues on mammary parenchyma, or a combination of both factors.     

Effect of feeding level pre- and post-puberty and body weight at first calving on growth, milk production, and fertility in grazing dairy cows

The effect of feeding to achieve differential growth rates in Holstein-Friesian (HF; n = 259) and Jersey (n = 430) heifers on time to puberty and first lactation milk production was investigated in a 3 × 2 factorial design. Holstein-Friesian and Jersey calves were reared to achieve a BW of 100 and 80 kg, respectively, at 100 d. At target weight, all calves were randomly allocated to one of 3 feeding treatments to achieve different growth rates. Holstein-Friesian and Jersey calves were fed fresh pasture to achieve average daily growth rates of 0.77, 0.53, or 0.37 kg of BW/d (HF) and 0.61, 0.48, or 0.30 kg of BW/d (Jersey), respectively. Period 1 (prepubertal) was imposed until HF and Jersey treatment groups averaged 200 and 165 kg of BW, respectively. Following period 1, HF and Jersey calves from each treatment group were randomly allocated to one of 2 feeding treatments to achieve average daily growth rates of 0.69 or 0.49 kg of BW/d (HF) and 0.58 and 0.43 kg of BW/d (Jersey), respectively. Period 2 (postpubertal) was imposed until 22 mo, when heifers were returned to their farms of origin. Body weight, body condition score, height, heart girth circumference (HGC), milk production, and fertility-related data were collected until the end of the third lactation. Time to reach puberty was negatively associated with level of feeding, and heifers attained puberty at the same BW (251 ± 25.4 and 180 ± 24.0 kg for HF and Jersey heifers, respectively). Heifers on high feed allowances during periods 1 and 2 were heavier, taller, and had greater HGC than their slower grown counterparts until 39 mo of age when height and HGC measurements stopped. Body weight differences remained until 51 mo, when measurements ceased. High feed allowance during period 1 (prepubertal) did not affect milk production during the first 2 lactations, but did reduce milk production in lactation 3. It is possible that the expected negative effect of accelerated pre-pubertal growth was masked by greater calving BW, as BW-corrected milk yield declined in both breeds with increasing prepubertal feed allowance. Growth rate during period 2 was positively correlated with first lactation milk production. Milk yield increased 7% in first lactation heifers on the high feed allowance, which resulted in higher growth rate during period 2. Milk production during subsequent lactations was not affected. Results suggest that accelerated prepubertal growth may reduce mammary development in grazing dairy cows, but this does not affect milk production in early lactations because of superior size. Body weight at calving and postpubertal growth rate management are important in first lactation milk production, but do not affect milk production in subsequent lactations.     

Identifying efficient dairy heifer producers using production costs and data envelopment analysis

During November and December 2011, data were collected from 44 dairy operations in 13 Pennsylvania counties. Researchers visited each farm to collect information regarding management practices and feeding, and costs for labor, health, bedding, and reproduction for replacement heifers from birth until first calving. Costs per heifer were broken up into 4 time periods: birth until weaning, weaning until 6 mo of age, 6 mo of age until breeding age, and heifers from breeding to calving. Milk production records for each herd were obtained from Dairy Herd Improvement. The average number of milking cows on farms in this study was 197.8 ± 280.1, with a range from 38 to 1,708. Total cost averaged $1,808.23 ± $338.62 from birth until freshening. Raising calves from birth to weaning cost $217.49 ± 86.21; raising heifers from weaning age through 6 mo of age cost $247.38 ± 78.89; raising heifers from 6 mo of age until breeding cost $607.02 ± 192.28; and total cost for bred heifers was $736.33 ± 162.86. Feed costs were the largest component of the cost to raise heifers from birth to calving, accounting for nearly 73% of the total. Data envelopment analysis determined that 9 of the 44 farms had no inefficiencies in inputs or outputs. These farms best combined feed and labor investments, spending, on average, $1,137.40 and $140.62/heifer for feed and labor. These heifers calved at 23.7 mo of age and produced 88.42% of the milk produced by older cows. In contrast, the 35 inefficient farms spent $227 more on feed and $78 more on labor per heifer for animals that calved 1.6 mo later and produced only 82% of the milk made by their mature herdmates. Efficiency was attained by herds with the lowest input costs, but herds with higher input costs were also able to be efficient if age at calving was low and milk production was high for heifers compared with the rest of the herd.     

The effect of feeding dairy heifers diets with and without supplemental phosphorus on growth, reproductive efficiency, health, and lactation performance

The phosphorus requirements for dairy heifers (0.20–0.35%) and endogenous concentrations (0.20–35%) of P in feeds fed to dairy heifers are similar, suggesting that the need for supplemental P in dairy heifer diets may be minimal. Because long-term P feeding studies on dairy heifers are unavailable, 183 Holstein heifers and 182 backcross Holstein × Jersey heifers were offered diets with (SP = 0.40% of dry matter) and without (NP = 0.30% of dry matter) supplemental P from 4 to 22 mo of age in a replicated pen design. Forty-eight pens of 8 heifers each were split evenly by breed and treatment group. Heifers were evaluated for body weight (BW), external bone/frame growth, dystocia, calf BW, reproductive efficiency, and first-lactation performance. Growth phase data were analyzed using pen-based statistical models, and lactation data were analyzed using mixed linear models with effects of season of birth, age of dam, heifer pen, sire, sire birth year, and days in milk. Heifers fed NP had similar average daily gain from 170 to 410 and from 410 to 650 d of age compared with heifers fed SP. At 22 mo of age, heifers fed NP did not differ in BW, hip height, hip width, body length, heart girth, cannon bone circumference, or pelvic area compared with heifers fed SP. Blood P concentrations between heifers fed SP or NP did not differ at 8 or 18 mo of age, and heifers fed SP excreted more P (29.2 vs. 24.2 g/d) than heifers fed NP. As heifers, services per conception and age at pregnancy were not different between heifers fed NP or SP. At parturition, heifers fed NP or SP had similar dystocia scores and calves were similar in BW. Complete first-lactation data (305 d) were available for 333 primiparous cows, and cows fed NP as heifers produced similar milk, fat, and protein compared with cows fed SP as heifers. Days open, days in milk at first breeding, and services per conception also were similar for primiparous cows fed NP or SP as heifers. No growth, reproductive, or lactation benefit was found by feeding dairy heifers diets containing 0.40% P compared with 0.30% P. Furthermore, P supplemented to SP heifers was simply excreted in the feces and not retained.     

The effects of teat bar design and weaning method on behavior, intake, and gain of dairy calves

The aim of the present study was to investigate the effects of teat-feeding method and weaning method on behavior, milk and concentrate intake, and weight gain of group-housed dairy calves. Forty-eight calves were housed in groups of 4 and offered 6 L of whole milk per calf in 2 daily feedings. In 6 of the 12 group pens, the calves were offered the milk in a teat bar with a separate milk compartment for each teat, whereas in the remaining 6 pens, the calves were offered the milk in a teat bar with all teats connecting to 1 shared milk compartment. Calves were gradually weaned off milk by reducing the volume of milk over a 10-d period, starting at an average age of 47 d. In 6 pens (3 pens with each of the 2 milk-feeding treatments), calves were weaned by volume reduction, whereas in the remaining pens, the calves were weaned by diluting the milk with water (WD) and maintaining the same total volume of liquid. Daily concentrate intake per pen was recorded during weaning and 1 wk after weaning. Behavior was recorded around milk feeding, by direct observation on 1 occasion before and on 1 occasion during weaning, and by video on 1 occasion before and 2 occasions during weaning. Furthermore, the behavior was recorded during the 15 h of light on 1 occasion during weaning. Individual milk intake was measured twice by weighing the calves immediately before and after milk feeding. The calves fed via a separate teat bar switched between teats more often than calves fed with a shared teat bar. There was greater variation in the duration of ingesting milk within groups fed via a separate teat bar, but no effect of teat bar design was found on the variation in milk intake within the groups. Calves fed via a separate teat bar took longer to start eating concentrate after milk feeding than calves fed with a shared teat bar. The WD calves had a lower concentrate intake during weaning than weaned by volume reduction calves. The WD calves were lying down less during the 30 min after milk feeding and during the 15 h of light, although they had a shorter latency to lie down after milk feeding. In conclusion, a separate teat bar increased teat switching, increased variation in duration of ingesting milk, and increased the latency to eat concentrates after milk feeding. There was no effect of the teat bar design on feed intake or weight gain. However, weaning the calves by gradually diluting the milk with water reduced lying during weaning and reduced the concentrate intake during and after weaning.     

Pre- and postweaning performance of holstein female calves fed milk through step-down and conventional methods

Milk consumption, dry feed intake, body weight (BW) gain, occurrence of diarrhea, and selected blood metabolites were studied in female Holstein calves fed milk either through conventional or step-down (STEP) methods. In conventional method, the calves (n = 20) were fed colostrum and then milk at the rate of 10% of BW for the entire period of 45 d. In STEP method, the calves (n = 20) were given colostrum and then milk for 25 d at the rate of 20% of BW, which was reduced (between d 26 to 30) to 10% of BW for the remaining 15 d. The calves fed through conventional and STEP methods were weaned gradually by diluting milk with water between d 46 and 50. Feed intake and BW of the calves were monitored until 90 d of age. The STEP calves consumed 92.3, 19.4, and 62.4% more milk than conventionally fed calves during pre-STEP (d 1 to 30), post-STEP (d 31 to 50), and preweaning (d 1 to 50) periods, respectively. Consumption of starter and hay were greater during the pre-STEP period and lesser during the post-STEP and postweaning (d 51 to 90) periods in calves provided milk using conventional method compared with STEP-fed calves. Body weight gain, dry matter intake, and feed efficiency of calves were greater in those on the STEP method than on the conventional method. Lesser blood glucose and greater blood urea nitrogen at weaning (d 50) and postweaning (d 60) possibly indicated a better functioning rumen in calves fed milk through The STEP method than those fed conventionally. Occurrence of diarrhea was higher during wk 3 and 4 of age in calves fed milk through conventional method compared with STEP-fed calves. In conclusion, STEP milk feeding may prevent the problems of depressed solid feed intake associated with ad libitum milk feeding and of poor BW gain with conventional milk feeding in dairy calves.     

Whole-milk feeding duration,calf growth,and profitability of group-fed calves in an organic production system

The objective of this study was to evaluate the effect of early-life feeding duration on growth and economics of group-fed organic dairy calves. Heifer calves born during the spring of 2011 (n = 67) and the spring of 2012 (n = 57) were used to evaluate the effect of weaning age, growth, and profitability of group-fed calves fed once per day in an organic dairy production system. Calves were assigned to replicate feeding groups of 10 in super hutches by birth order, and were born at the University of Minnesota West Central Research and Outreach Center, Morris organic dairy. Breed groups were Holsteins (n = 15) selected for high production, Holsteins (n = 23) maintained at 1964 breed-average level, crossbreds (n = 54) including combinations of Holstein, Montbéliarde, and Swedish Red, and crossbreds (n = 32) including combinations of Holstein, New Zealand Friesian, Jersey, and Swedish Red. Groups of calves were weaned at 30 (EW, early weaning), 60 (MW, mid weaning), or 90 (LW, late weaning) d of age, and groups were fed 1.5% of birth weight of 13% total solids organic whole milk once daily and weaned when the group of 10 calves consumed an average of 0.91 kg of organic calf starter per calf per day for 4 consecutive days. Body measurements were recorded at birth, weekly during the preweaning period, at weaning, and monthly thereafter. Profitability was estimated as a function of the total cost for organic milk and organic calf starter for weaning groups to weaning and to the first 90 d of age. Preweaning group performance was weaning age, EW: 47.6 d, MW: 64.5 d, LW: 93.7 d; weaning weight, EW: 61.8 kg, MW: 79.2 kg, LW: 108.1 kg; and gain per day, EW: 0.51 kg/d, MW: 0.63 kg/d, LW: 0.75 kg/d. Body weight (BW) did not differ among weaning groups at 90 d of age; however, MW calves had lower 120-d BW than did LW calves. The EW calves did not differ from either MW or LW calves for 120-d BW. Total feed costs to weaning for groups were $1,092.97 for EW calves, $1,871.24 for MW calves, and $2,956.64 for LW calves. The cost per kilogram of gain was higher for the EW ($5.54) group of calves than for the MW ($4.60) or LW ($4.14) groups during the preweaning period. Total costs and cost per kilogram of gain for the first 90 d of age were lowest for EW ($1,595.59, $3.02) calves and highest for LW ($2,956.64, $4.13) calves, respectively.     

Effect of nursing management and skeletal size at weaning on puberty, skeletal growth rate, and milk production during first lactation of dairy heifers

Forty Israeli-Holstein 5-d-old calves were used to determine the effect of increasing calf body weight (BW) and skeletal size during the nursing period on age and skeletal size at puberty and on skeletal size and performance during first lactation. The calves were randomly allotted to 2 experimental groups as follows: milk replacer (MR) [calves were given 0.450 kg/d dry matter of milk replacer for the first 50 d of life] and milk-fed (MF) [calves had free access to milk in two 30-min meals/d]. From weaning to 180 d of age, all calves were fed the same diet. At 180 d of age, the MR and MF calves were each divided into 2 equal subgroups: one subgroup from each treatment was given only growing ration, and the other was given the same ration supplemented with fish meal to supply 2% crude protein (CP) (treatments MR + CP and MF + CP, respectively). Finally, at 270 d of age, all calves were housed together and fed a growing heifer's ration until first calving. During the entire nursing period, the MF calves consumed 9.8% more DM, 39.7% more CP, and 52.4% more metabolizable energy than the MR calves. At 60 d of age, BW and all skeletal parameters were higher in the MF calves than in the MR calves. During the entire rearing period (60 to 550 d), the average BW of the MF calves was greater by 16 kg than the BW of the MR calves. Nursing management did not affect differences in skeletal parameters at calving. Average age at puberty onset was 272 +/- 26.8 d; MF calves reached puberty 23 d earlier than MR calves. Yields of milk (kg/305 d) and fat-corrected milk (FCM, kg/d) were greater for the MF + CP heifers than for the MR heifers. It was concluded that nursing by ad libitum milk, as compared with milk replacer, affected BW but not skeletal size of the adult animal, decreased age of puberty onset, and increased FCM yield at first lactation. Supplementing the diet with 2% CP during the prepubertal period increased BW but not skeletal size of the adult animal and 305-d milk and FCM yields during first lactation.     

Evaluation of potential carryover effects associated with limit feeding of gravid Holstein heifers

Ninety-six Holstein heifers (400 ± 6 kg, 15.2 ± 0.1 mo), including 9 with ruminal cannulas, were offered 1 of 3 diets for 180 ± 8 d in a randomized replicated pen design. Dietary treatments included a control diet (C100) and 2 independent limit-fed (LF) diets. The LF diets included one offered at 85% of C100 intake (L85) without an ionophore, and a second containing an ionophore (325 mg/head per day of lasalocid) that was offered at 80% of C100 intake (L80+I). Heifers were evaluated for growth, rumen digesta volume, nutrient excretion, and subsequent lactation performance. Limit-fed heifers consumed less dry matter and neutral detergent fiber, and had greater respective average daily gains (0.96 or 0.89 vs. 0.81 kg/d), and lower feed:gain ratios (9.1 or 9.3 vs. 13.0 kg/kg) compared with heifers offered the C100 diet. No differences in rumen pH, NH₃-N, or volatile fatty acid concentrations were observed between C100 and LF heifers. Rumen digesta volume, density, and weight were unaffected by LF, and feeding L85 or L80+I did not result in carryover effects for rumen digesta volume when these heifers were offered a common high-fiber diet immediately after the 180-d growth trial. At parturition, no differences were observed for dystocia index, calf body weight, or 7-d postpartum body weight between cows offered LF or C100 diets as heifers. Lactation body weight, dry matter intake, and feed efficiency of cows did not differ between treatments at 45 or 90 d in milk. Milk yield and milk components also were not different between cows that were offered C100 or LF diets as gravid heifers. At 45 d in milk, rumen digesta volume was greater (99.1 vs. 66.1 L) for cows offered L85 compared with cows offered L80+I as gravid heifers, but this effect was not observed at 90 d in milk. Limit feeding of gravid Holstein heifers for 180 d did not result in any carryover effects during their first lactation for rumen digesta volume, dry matter intake, or milk yield.     

Influence of dietary fat and protein on body composition of Jersey bull calves

Thirty-nine bull calves between 6 and 9 d of age, were assigned to either baseline slaughter or 1 of 4 diets to determine the influence of dietary fat and protein content, at 2 levels of intake, on growth and body composition changes. Calves were assigned to the following diets a 28.5% protein and 16.4% fat milk replacer [MR; 29/16 (n = 9)], 27.3% protein and 33.4% fat MR [27/33 (n = 8)], 20.6% protein and 20.6% fat MR [20/20 (8)], or whole milk [WM (n = 8)]. Calves fed 27/33, 29/16, and WM received 180 g/d of CP to support 650 g of ADG based on predictions from the 2001 NRC. Calves were fed 3 times daily for 4 wk. Weight, hip height, wither height, heart girth, and body length were measured weekly. Weekly plasma samples were analyzed for plasma urea nitrogen, nonesterified fatty acids, and glucose. A subset of calves from each treatment was killed [29/16 (n = 7), 27/33 (n = 6), 20/20 (n = 6), and WM (n = 5)] at the end of wk 4 of treatment; processed for whole-body analysis of fat, protein, ash, and DM; and compared with baseline slaughter calves to estimate composition of empty BW gain. Calves did not differ in average weekly scour score or medication days. Feed efficiency and ADG were greatest for calves fed WM and least for calves fed 20/20; calves fed 29/16 and 27/33 did not differ. Calves fed 27/33 or WM had the greatest % body fat and gained more grams of fat than calves fed other diets. Calves fed 29/16 or 20/20 had similar % fat in empty body as baseline. Differences in % CP, % ash, or % water in empty body and empty BW gain were not detected. Calves fed 27/33 had a trend toward higher NEFA in wk 1 and 2 than calves fed 29/16 or WM. Growth of calves fed 27/33 and 29/16 were similar except that calves fed 29/16 had lower body fat % than calves fed 27/33. Calves on all diets gained less than predicted by the 2001 NRC.     

Effects of vegetable fats versus lard in milk replacers on feed intake, digestibility, and growth in Finnish Ayrshire bull calves

The aim was to study whether vegetable fat mixtures could be used instead of lard [15.2% in dry matter (DM)] in milk replacers without impairing the performance of Finnish Ayrshire bull calves (n = 58). The growth performance of the calves was measured before and after weaning from 14 d to 6 mo of age. The following 3 fat sources in a milk replacer were studied: 1) a mixture of palm, coconut, and rapeseed oil, 2) palm and coconut oil, and 3) lard. The calves were bucket-fed 2 L of milk replacer 3 times per day. The milk replacer contained 116 g of DM/L, resulting in an average DM intake of 4.8 g of DM/kg of body weight^0.75 (BW^0.75) during the 8-wk trial, after which the calves were weaned. All the calves had free access to water, commercial starter, and grass silage before weaning. The weaned calves had free access to water and grass silage and were given 3 kg/d (air-dry basis) of a commercial concentrate mixture. The concentrate was replaced by barley when the bulls were 4.5 mo old. There were no significant differences between the diets in feed intake and apparent diet digestibility. The health and BW of the calves were similar during the study. The feed conversion rate (kg of DM intake/kg of gain) before weaning was significantly greater for the lard diet compared with the 2 vegetable fat mixtures. After weaning, the feed conversion rate was slightly lower for the diet that included the palm, coconut, and rapeseed oil mixture than for the diet that included palm and coconut oil mixture. The study showed that the 2 mixtures consisting solely of vegetable oils were effective dietary components, thus providing 2 alternative fat mixtures of milk replacers, for use instead of lard in formulating commercial calf milk replacers.     

Short- and long-term effects of initial serum total protein,average starter feed intake during the last week of the preweaning period,and rearing body gain on primiparous dairy heifers' performance

The aim of this study was to evaluate the short- and long-term effects of initial serum total protein (STP) concentration, average starter feed intake (SI) during the last week of the preweaning period, and average daily gain (ADG) on the growth, fertility, and performance of Holstein heifers during their first lactation. Eighty-four female Holstein dairy calves were weaned at d 56 of age and then the study continued until the end of the first lactation. Growth performance, including body weight, ADG, withers height, and its change were analyzed monthly from 3 to 450 d of life, and reproduction data and performance in the first lactation of primiparous dairy heifers over a 4-yr period (2015 to 2019) were recorded. In the first 24 h of life, calves received 4 L of colostrum (<2 h and <12 h after birth); on d 2 and 3: 2 feedings/d of 2 L of transition milk; from d 4 to 49: 6 L/d of milk replacer (150 g of powder/L as-fed) in 3 feedings; and from d 50 to 56: 2 L/d of milk replacer in 1 feeding. The calves were fed pelleted starter feed from d 4 to 56, and after that from 8 wk until 3 mo of age, a dry total mixed ration with an 85:15 ratio of weaning pelleted starter to straw. From 3 to 7 mo and from 8 mo of age to calving, the total mixed ration contained 16.9% and ~14.0% crude protein, respectively, on a dry matter basis and ~2.40 Mcal of metabolizable energy/kg on a dry matter basis. The results of the current study showed that the initial STP concentration of primiparous dairy heifers was associated with improved growth performance, especially greater body weight and withers height. In addition, with increasing levels of initial STP concentration, age at first estrus, artificial insemination (AI) service, pregnancy, and calving was decreased by 16, 18, 25, and 25 d, respectively. Initial STP concentration was positively correlated with milk production and increased total milk yield and yield of energy-corrected milk by about 1,558 kg and 1,149 kg during first lactation. Calves with higher average starter feed intake during the last week of the preweaning period had better growth performance, which in turn was positively associated with fertility parameters, accelerated first estrus (by 17 d), and reduced age at AI service (by 13 d). Preweaning ADG was favorably associated with fertility performance of heifers, with faster occurrence of first estrus and a reduction in age at AI service, pregnancy, and calving. Also, increasing preweaning ADG increased milk yield, energy-corrected milk, and 4% fat-corrected milk at 305 DIM by about 829, 754, and 763 kg at first lactation of primiparous heifers. These results indicate that in the rearing period, particular attention should be paid to the initial STP concentration, average SI during the last week of this period, and rearing ADG to increase growth, fertility, and performance in the first lactation of primiparous dairy heifers.     

Starch source evaluation in calf starter: I. Feed consumption, body weight gain, structural growth, and blood metabolites in Holstein calves

Holstein calves were fed pelleted iso-starch (25% of starter dry matter) diets containing barley (n = 16), corn (n = 16), oat (n = 16), and wheat (n = 16) starch for 12 wk of age. Feed consumption, nutrient intake, body weight (BW) gain, skeletal growth, and selected blood metabolites in calves during preweaning (d 1 to 49) and postweaning (d 50 to 84) periods were measured. Average daily starter consumption during pre-weaning and postweaning periods was the greatest in calves fed corn died followed by those fed a wheat diet and then in those fed barley and oat diets. During the preweaning period, the calves provided corn and wheat diets consumed greater amount of mixed grass hay than those fed barley and oat diets. During the postweaning period, mixed grass hay intake was the greatest in calves provided corn diet followed by those fed a wheat diet and then in those fed barley and oat diets. Nutrients (dry matter, crude protein, starch, and neutral detergent fiber) intake followed the solid feed consumption pattern in calves. Body weight and body measurements (body length, body barrel, heart girth, wither height, and hip height) at birth and at weaning (d 49) in calves fed different starch sources were similar. Body weight and body measurements at postweaning (d 84) were the greatest in calves fed a corn diet followed by those fed a wheat diet and then in those fed barley and oat diets. Overall average BW gain and total dry matter intake were the greatest in calves fed a corn diet than in those fed wheat, barley, and oat diets. Feed efficiency was greater in calves fed corn and wheat diets than in those fed barley and oat diets. Blood glucose, blood urea N, triglycerides, cholesterol, and creatinine were reduced with the advancing age of calves. Lesser blood glucose and greater blood urea N concentrations at wk 8, 10, and 12 of age were noticed in calves fed corn diet than in those fed barley, oat, and wheat diets. Occurrence of diarrhea was more frequent in calves fed oat diet than in those provided barley, corn, and wheat diets. Starch sources did not influence respiratory score, rectal temperature, and general appearance score. In conclusion, the calves on corn diet consumed more solid feed and gained greater BW than those fed barley, oat, and wheat diets.     

Exposure to long-day photoperiod prepubertally may increase milk yield in first-lactation cows

Exposure to a long-day photoperiod (LDPP) increases mammary and lean growth in heifers relative to a short day (SDPP). Whether these effects influence milk yield, however, is unknown. To test the hypothesis that pre-pubertal long-day exposure would increase milk production, we assigned prepubertal heifers to LDPP (16 h of light:8 h of dark; n = 16) or SDPP (8 h of light:16 h of dark; n = 16) until the onset of puberty. At puberty, heifers were commingled and housed under natural photoperiodic conditions and standard nutritional management for dairy heifers. Heifers were bred according to body weight (BW = 385 kg) and withers height (WH = 132 cm). At parturition, BW, WH, and hip height were evaluated. Analysis of Dairy Herd Improvement Association records was used to evaluate milk yield, milk components, and somatic cell scores. Relative to SDPP (n = 12), heifers on LDPP (n = 10) had greater WH (by 2.4 cm) and BW at calving (by 55 kg). Compared with heifers housed under SDPP, LDPP heifers tended to produce more milk (750 kg of 305-d projected fat-corrected milk) during the first lactation. Relative to SDPP, prepubertal heifers exposed to LDPP during the prepubertal growth phase were taller and heavier at parturition, and tended to produce more milk during their first lactation.     

Analysis of nitrogen utilization and excretion in growing dairy cattle

Literature data on utilization of dietary N were analyzed by using meta-analytic procedures for growing milk-fed dairy calves and weaned dairy heifers. The objective was to statistically assess N utilization and excretion in growing dairy cattle when dietary N was altered in otherwise balanced rations at various stages of growth. Studies meeting the selection criteria included data from 16 published papers encompassing 94 distinct observations made on 217 animals. Of these, 6 studied calves were fed milk or milk protein-based milk replacer [milk-fed; 30 to 81 kg of body weight (BW)] with 37 different dietary treatments, and 10 experiments studied heifers receiving diets based on forage, concentrates, or a combination of forage and concentrates (weaned; 56 to 472 kg of BW) with 57 different dietary treatments. Mixed model and fixed effect regression analyses were used to evaluate responses to additional dietary N. True digestibility of dietary N was 100.4% for milk-fed calves and 96.4% for weaned heifers, with corresponding basal fecal N excretion values of 3.05 and 6.51 g of N/kg of dry matter intake. Urinary N (g of N/kg of BW^0.75) was consistently greater for milk-fed calves, but the response to increasing N intake was parallel to the response for weaned heifers. Whether using a mixed model approach or a fixed effect approach to account for metabolizable energy intake, BW, and dry matter intake, milk-fed calves retained more N per kilogram of BW^0.75 than weaned heifers. However, marginal efficiency of N utilization responded as a continuous function of BW, as opposed to a bimodal response associated with diet type. Gross N efficiency (GNE) responded quadratically to N intake and was greater for milk-fed calves than for weaned heifers. Linear and quadratic coefficients of this function did not differ between diet types, indicating that the response in gross N efficiency to additional N intake was not different between diet groups; rather, the absolute level obtainable differed. Dietary CP concentrations of 18.9% for milk-fed calves and 14.2% for weaned heifers were found to maximize GNE; 22.5% MJ of crude protein/MJ of ME was found to maximize GNE for both groups. Equations are discussed relative to the requirements to replace basal N losses and efficiency of N utilization.     

Effect of prepubertal and postpubertal growth and age at first calving on production and reproduction traits during the first 3 lactations in Holstein dairy cattle

The objective of this study was to evaluate the effect of body condition score (BCS), body weight (BW), average daily weight gain (ADG), and age at first calving (AFC) of Holstein heifers on production and reproduction parameters in the 3 subsequent lactations. The data set consisted of 780 Holstein heifers calved at 2 dairy farms in the Czech Republic from 2007 to 2011. Their BW and BCS were measured at monthly intervals during the rearing period (5 to 18 mo of age), and the milk production and reproduction data of the first 3 lactations were collected over an 8-yr period (2005 to 2012). The highest milk yield in the first lactation was found in the group with medium ADG (5 to 14 mo of age; 0.949 to 0.850 kg of ADG). The highest average milk yield over lifetime performance was detected in heifers with the highest total ADG (≥0.950 kg/d). The difference in milk yield between the evaluated groups of highest ADG (in total and postpubertal growth ≥0.950 kg/d and in prepubertal growth ≥0.970 kg/d) and the lowest ADG (≤0.849 kg/d) was approximately 1,000 kg/305 d per cow. The highest milk yield in the first lactation was found in the group with the highest AFC ≥751 d, for which fat and protein content in the milk was not reduced. Postpubertal growth (11 to 14 mo of age) had the greatest effect on AFC. The group with lowest AFC ≤699 d showed a negative effect on milk yield but only in the first 100 d of the first parity. The highest ADG was detrimental to reproduction parameters in the first lactation. The highest BW at 14 mo (≥420 kg) led to lower AFC. Groups according to BCS at 14 mo showed no differences in AFC or milk yield in the first lactation or lifetime average production per lactation. We concluded that low AFC ≤699 d did not show a negative effect on subsequent production and reproduction parameters. Therefore, a shorter rearing period is recommended for dairy herds with suitable management.     

Effects of rearing diet, age at freshening, and lactation feeding system on performance

This two-phase trial involved 83 Holstein heifers. The rearing phase consisted of two diets (alfalfa silage plus corn grain for ad libitum intake vs. corn silage plus urea for ad libitum intake) and two breeding age groups (13 vs. 16 mo). The lactation phase compared the above treatments plus two lactation feeding systems: concentrate fed individually to production versus a TMR. The heifers were assigned randomly to the rearing phase at 7 wk of age and fed their respective diets until 14 d prepartum. They were placed on preassigned lactation diets 14 d prepartum and remained on the lactation phase for 550 consecutive d. Daily gains and height at the withers were similar between forage groups during the first half of the rearing phase; in the second half, the heifers fed alfalfa silage were taller at the withers. Those fed corn silage consumed less DM and CP throughout the rearing phase and gained more BW than the heifers fed alfalfa in the latter half. There were no differences in daily gain or DMI between the breeding age groups. In the lactation phase, the group fed alfalfa for ad libitum intake consumed more DM and gave more milk during the first 90 d of lactation than heifers fed corn silage. However, after 90 d the difference in cumulative milk production was not significant. There were no differences in milk production. FCM, or DMI between breeding age groups. The cows fed concentrate consumed more DM and gave more milk during the first 90 d of lactation. By 550 d, there were no differences. Feeding high levels of corn silage can cause heifers to have lower DMI in early lactation. These differences tend to disappear during the second lactation.     

Effects of feeding supplemental organic iron to late gestation and early lactation dairy cows

The objectives of this experiment were to determine the Fe status of cows in late gestation and early lactation and determine whether measures of Fe status and milk production were affected by feeding supplemental organic Fe. Starting 60 d before anticipated calving, cows and heifers were fed diets with 0 or 30 mg/kg of supplemental Fe (Availa-Fe, Zinpro Corp., Eden Prairie, MN). All animals changed to prefresh diets at 14 d before anticipated calving and then to lactation diets following calving; the Fe supplementation rates (0 or 30 mg/kg) remained constant. The experiment ended at 63 d in milk. Hematocrit, hemoglobin, serum Fe, unsaturated Fe binding capacity, and percentage Fe binding saturation were measured at the start of the experiment, 7 d before calving, 7 d after calving, and at 60 d in milk. Treatment did not affect any measure of Fe status and values did not change greatly over time. Milk production (averaged 41 kg/d), milk composition, and dry matter intake during early lactation (averaged 20.4 kg/d) were not affected by treatment. The somatic cell count of milk was reduced when cows were fed supplemental Fe (114,000 vs. 94,000 cells/mL). The limited response to supplemental Fe may have been because basal diets were adequate in Fe (ranged from 282 to 336 mg of Fe/kg of DM) even though most of the basal dietary Fe was provided by forages, which are generally considered poor sources of available Fe.