Growth hormone response to growth hormone releasing hormone in calves that differ in genetic merit for milk yield

Holstein heifer, steer, and bull calves from control (CL) and select (SL) lines of cows that differed by more than 4000 kg of milk during a 305-d lactation (SL > CL) were used to determine growth hormone (GH) response to 5 doses of GH releasing hormone (GHRH) and how this response was affected by gender, period (age), and genetic merit for milk yield. Doses (0, 2.5, 5, 10, and 20 microg/100 kg of BW) of a GHRH analog were assigned randomly to each heifer (4 CL, 4 SL), steer (4 CL, 4 SL), and bull (3 CL, 3 SL) calf and administered on consecutive days at approximately 3, 6, and 10 mo of age (periods; P1, P2, and P3). Jugular blood samples (n = 15) collected between -30 and 240 min relative to GHRH administration were used to quantify area under the GH response curve (AUC) after subtracting mean prechallenge GH concentrations. Estimates of maximum response (Rmax) and sensitivity (ED50) to GHRH were obtained from the hyperbolic dose response curves (AUC vs. dose). Data were analyzed for effects of dose, line, period, gender, and their interactions with period as the repeated effect. Prechallenge GH concentrations were not affected by genetic line, gender, or period. The AUC was not affected by line, but decreased with period and increased with GHRH dose. The Rmax did not differ between lines or among genders, but decreased with period. The ED50 did not differ between lines or among periods, but heifers were more sensitive to GHRH than steers or bulls. Although GH response to GHRH has been identified as a potential indicator of genetic merit, it did not differ between these substantially different genetic lines.     

Effects of week of lactation and genetic selection for milk yield on milk fatty acid composition in Holstein cows

Control (CL) and select line (SL) dairy cows (n = 22) managed identically but differing in milk yield (>4100 kg/305 d) were used to determine differences in milk fatty acid profile as lactation progressed. Milk yield was recorded daily and milk samples were collected during wk 1, 4, 8, 12, and 16 postpartum for milk composition analysis. Milk samples from wk 1, 8, and 16 were also analyzed for fatty acid composition. Select-line cows produced more milk (44.4 vs. 31.2 kg/d) and milk components than CL cows during the 16-wk period. There was no difference in rate of milk yield increase, but peak milk yield for SL cows was greater and occurred later in lactation. There were no differences in milk SCC or milk fat, protein, or lactose content. Selection for milk yield did not affect the content of most individual milk fatty acids; however, compared with CL, SL cows had a reduced Delta(9)-desaturase system and tended to produce milk with lower monounsaturated fatty acid content. Selection for milk yield did not affect milk fatty acid origin but the percentage of de novo fatty acids increased and preformed fatty acids decreased as lactation progressed. Milk fat trans-11 18:1 and cis-9,trans-11 conjugated linoleic acid increased with progressing lactation (10.7 vs. 14.1 and 3.1 vs. 5.4 mg/g, or 31 and 76%, respectively) and were correlated strongly among wk 1, 8, and 16 of lactation. Temporal changes in the Delta(9)-desaturase system occurred during lactation but these changes were not correlated with milk fat cis-9,trans-11 conjugated linoleic acid content. Results indicate prolonged genetic selection for milk yield had little effect on milk fatty acid composition, but milk fatty acid profiles varied markedly by week of lactation.     

Effects of genetic selection for milk yield on somatotropin, insulin-like growth factor-I, and placental lactogen in Holstein cows

Cows from static, low-merit control (CL) and contemporary, high-merit select (SL) lines that differed in milk yield by more than 4,000 kg/305-d lactation (SL > CL) were used to determine effects of selection for milk yield on blood serum concentrations of somatotropin (ST), insulin-like growth factor (IGF-I), and placental lactogen (PL). Cows were exposed to the same environment and management conditions and fed the same diets. Serum and milk samples were collected from primiparous (18 CL, 18 SL) and multiparous (12 CL, 18 SL) cows relative to day of lactation (from −28 to 280 d for nonpregnant cows and to subsequent calving for cows that conceived). Data were analyzed as repeated measures using mixed model procedures. Serum ST increased at calving, remained elevated for a longer interval in SL than in CL cows, and was greater in SL than in CL cows. Serum IGF-I decreased at calving, remained low through 14 DIM, and gradually returned to precalving concentrations as lactation progressed. Postpartum concentrations of IGF-I were less in SL than CL through 84 DIM and were similar through the remainder of lactation, resulting in a line by day interaction. Serum IGF-I and PL were not affected by merit during gestation. There was an interaction of merit and postconception interval on IGF-I, with the difference in IGF-I concentration between lines decreasing as gestation progressed. Change in serum IGF-I and PL appeared to be synchronous. Results indicate that selection for milk yield increased serum ST, prolonged the postpartum reduction in serum IGF-I, and did not alter serum PL. Results also indicate a positive relationship between PL and IGF-I and support the concept that PL plays a role in the regulation of serum IGF-I during gestation.     

Effects of additional milk replacer feeding on calf health, growth, and selected blood metabolites in calves

The objective of the experiment was to evaluate effects of increased milk replacer feeding on growth, intake, feed efficiency, and health parameters in stressed calves. Holstein bull calves (n = 120; approximately 3 to 8 d of age) were purchased from sale barns and dairy farms and housed in fiberglass hutches. In addition, wood shavings contaminated with coronavirus were mixed with clean shavings and added to each hutch before the start of the experiment. Calves were fed either a fixed amount (454 g/d) of a 20% crude protein (CP), 20% fat milk replacer to weaning at 28 d or a variable amount (454, 681, 908, and 454 g/d on d 0 to 7, 8 to 14, 15 to 31, and 32 to 41, respectively) of a milk replacer containing 28% CP and 17% fat without or with added dietary supplement containing bovine serum. Calves were also fed commercial calf starter and water ad libitum. Plasma IgG concentration in most calves on arrival at the facility was < 10 g/L. Intake, change in body weight, feed efficiency, morbidity and mortality, and selected plasma metabolites were determined. Body weight at 28 d, 56 d, daily body weight gain, intake of milk replacer, fecal scores, days with diarrhea, and days treated with antibiotics were increased with feeding variable amount of milk replacer over the 56-d study. Starter intake from d 1 to 56 was reduced from 919 to 717 g/d in calves fed fixed and variable amounts of milk replacer, respectively. Morbidity, measured as the number of days that calves had diarrhea, was increased by 53% when a variable amount of milk replacer was fed. Calves fed variable milk replacer were treated with antibiotics for 3.1 d compared with 1.9 d for calves fed 454 g of milk replacer/d. Concentrations of plasma glucose, urea N, and insulin-like growth factor-I were increased when calves were fed variable amount of milk replacer. Dietary supplement containing bovine serum had no effect on any parameter measured. There was no effect of milk replacer feeding on concentrations of nonesterified fatty acids, total protein, or growth hormone concentrations. Plasma tumor necrosis factor-α was highest in calves with the highest plasma IgG concentrations on the day of arrival and might be related to the calf's ability to identify pathogens in the environment. Under conditions of this study, calves fed variable amount of milk replacer and exposed to immunological challenge before weaning had greater BW gain, but also increased incidence of diarrhea that required added veterinary treatments.     

Genetic effects of heat stress on milk yield of Thai Holstein crossbreds

The threshold for heat stress on milk yield of Holstein crossbreds under climatic conditions in Thailand was investigated, and genetic effects of heat stress on milk yield were estimated. Data included 400,738 test-day milk yield records for the first 3 parities from 25,609 Thai crossbred Holsteins between 1990 and 2008. Mean test-day milk yield ranged from 12.6 kg for cows with <87.5% Holstein genetics to 14.4 kg for cows with ≥93.7% Holstein genetics. Daily temperature and humidity data from 26 provincial weather stations were used to calculate a temperature-humidity index (THI). Test-day milk yield varied little with THI for first parity except above a THI of 82 for cows with ≥93.7% Holstein genetics. For third parity, test-day milk yield started to decline after a THI of 74 for cows with ≥87.5% Holstein genetics and declined more rapidly after a THI of 82. A repeatability test-day model with parities as correlated traits was used to estimate heat stress parameters; fixed effects included herd-test month-test year and breed groups, days in milk, calving age, and parity; random effects included 2 additive genetic effects, regular and heat stress, and 2 permanent environment, regular and heat stress. The threshold for effect of heat stress on test-day milk yield was set to a THI of 80. All variance component estimates increased with parity; the largest increases were found for effects associated with heat stress. In particular, genetic variance associated with heat stress quadrupled from first to third parity, whereas permanent environmental variance only doubled. However, permanent environmental variance for heat stress was at least 10 times larger than genetic variance. Genetic correlations among parities for additive effects without heat stress considered ranged from 0.88 to 0.96. Genetic correlations among parities for additive effects of heat stress ranged from 0.08 to 0.22, and genetic correlations between effects regular and heat stress effects ranged from −0.21 to −0.33 for individual parities. Effect of heat stress on Thai Holstein crossbreds increased greatly with parity and was especially large after a THI of 80 for cows with a high percentage of Holstein genetics (≥93.7%). Individual sensitivity to heat stress was more environmental than genetic for Thai Holstein crossbreds.     

Effects of feeding milk replacer once versus twice daily on glucose metabolism in Holstein and Jersey calves

Eighteen Holstein (experiment 1) and 15 Jersey (experiment 2) heifer calves were fed milk replacer once or twice daily to determine effects of feeding frequency on weight gain, starter intake, and glucose metabolism. Body weights were measured weekly from birth to 8 wk. Blood samples were collected at wk 1 through 6 from all calves before and at 30, 60, 90, 120 and 180 min after the morning feeding. Plasma was analyzed for glucose, insulin, glucagon, and nonesterified fatty acids (NEFA). Urine was collected 90 min postfeeding to measure glucose concentration. Treatment did not affect mean starter intake or body weight. In experiments 1 and 2 mean plasma glucagon, glucose, NEFA, and insulin and urinary glucose concentrations were not affected by treatment. There was an interaction of sampling time and treatment for plasma insulin concentrations but not for glucose concentrations in both experiments. Following feeding, calves fed milk replacer once daily had higher insulin concentrations than those fed twice daily. There was an interaction of sampling time and treatment for plasma NEFA concentrations in Jersey calves only. Jersey calves fed milk replacer once daily had higher plasma NEFA concentrations before the morning milk replacer feeding. At wk 3 and 6, frequently sampled intravenous glucose tolerance tests were performed to assess glucose effectiveness, insulin sensitivity, and acute insulin response. In experiments 1 and 2 glucose effectiveness and insulin sensitivity were similar regardless of milk replacer feeding frequency. In Holstein and Jersey calves fed milk replacer twice daily, acute insulin response was greater than in calves fed once daily. However, insulin sensitivity decreased with age, while acute insulin response increased with age. These data suggest that feeding calves milk replacer once daily did not deleteriously affect performance or glucose metabolism regardless of breed.     

Effects of spray-dried animal plasma in calf milk replacer on health and growth of dairy calves

Male Holstein calves (n = 120) purchased from local dairy farms were fed one of three calf milk replacers for 42 d. Experimental milk replacers were formulated to contain whey protein concentrate (WPC) as the primary protein source or WPC plus 5% spray-dried bovine plasma (SDBP) or spray-dried porcine plasma (SDPP). The SDPP was heated to remove heat-insoluble materials and provide products with similar IgG content. Calves were also fed commercial calf starter and water for ad libitum consumption. Intake, change in body weight (BW), feed efficiency, morbidity and mortality were determined. Mortality was 10, 3, and 2 in calves fed WPC, SDBP, and SDPP treatments, respectively. Morbidity, measured as the number of days that calves had diarrhea was reduced by 30% when SDBP or SDPP were fed. Calves had diarrhea for 6.9, 3.9, and 4.7 d during the 42-d study when fed commercial calf milk replacer containing WPC, SDBP, and SDPP, respectively. Fecal scores tended to be reduced and feed efficiency tended to be improved when SDBP or SDPP were fed. Mean intakes of total dry matter during the 42-d study were greater when calves were fed SDBP or SDPP and were 661, 710, and 684 g/d for calves fed WPC, SDBP, and SDPP, respectively. Mean BW gains from d0 to 42 were 231,261, and 218 g/d, respectively. Calves fed SDPP tended to have lower BW gain during the first 28 d of the study. However, difference in daily BW gain from d 1 to 28 was only 39 g/d. Inclusion of SDBP or SDPP in milk replacer reduced morbidity and mortality of milk-fed dairy calves.     

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.     

Growth and health of Holstein calves fed milk replacers supplemented with antibiotics or Enteroguard

Forty-five Holstein calves were fed milk replacers containing either antibiotics [MRA (oxytetracycline at 138 mg/kg and neomycin at 276 mg/kg), n = 22)] or Enteroguard [MRE, a blend of fructooligosaccharides, allicin, and gut-active microbes at (129 mg/kg, n = 23)] from birth to 5 wk of age to compare effects on average daily gain and on incidence of scours. Performance was evaluated by measuring weight gain, feed efficiency, and fecal scores. The overall body weight gains and severity of scours were not different between treatments, nor were there differences in starter intake or mean body weight gain. During wk 2, the average gain of calves fed MRA was less than that of calves fed MRE (0.07 vs. 0.09 kg/d, P = 0.09), and greater during wk 5 (0.62 vs. 0.51 kg/d, P < 0.01); however, total gain for calves fed MRE was not different from calves fed MRA. Likewise, average feed efficiencies (gain/dry matter intake) were not different. Severity of scours, as measured by fecal scores, and concentrations of serum proteins, an indirect measure of immunoglobulins, were similar for calves fed MRA and MRE. The results suggest that antibiotics in milk replacers can be replaced with compounds such as fructooligosaccharides, probiotics, and allicin to obtain similar calf performance.     

Effects of preweaning total plane of milk intake and weaning age on intake,growth performance,and blood metabolites of dairy calves

The objective of this study was to evaluate the effects of preweaning total plane of milk intake and weaning age on intake, growth performance, and blood metabolites of dairy calves. A total of 48 Holstein calves (40 ± 1.6 kg of body weight) were used in a 2 × 2 factorial arrangement with the factors of weaning age (d 60 vs. 75) and the total plane of milk intake (medium vs. high) during the preweaning period. Calves were assigned to 1 of 4 treatments: (1) calves fed medium plane of milk (MPM) intake and weaned on d 60 of age (MPM-60d, 4 L/d of milk from d 3 to 10, 6 L/d of milk from d 11 to 55, and 3 L/d of milk from d 56 to 60 of age; total milk intake = 317 L), (2) calves fed MPM intake and weaned on d 75 of age (MPM-75d, 4 L/d of milk from d 3 to 10 and 4.5 L/d of milk from d 11 to 70 of age followed by feeding 2.25 L/d of milk from d 71 to 75 of age; total milk intake = 313 L), (3) calves fed high plane of milk (HPM) intake and weaned on d 60 of age (HPM-60d, 4 L/d of milk from d 3 to 10, 6 L/d of milk from d 11 to 20, and 8.5 L/d of milk from d 21 to 55 followed by feeding 4.25 L/d of milk from d 56 to 60 of age; total milk intake = ～411 L); and (4) calves fed HPM intake and weaned on d 75 (HPM-75d, 4 L/d of milk from d 3 to 10, and 6 L/d of milk from d 11 to 70 of age followed by feeding 3 L/d of milk from d 71 to 75 of age; total milk intake = 407 L) with no milk refusals. All of the calves were monitored up to d 90 of age. Regardless of weaning age, starter feed intake and dry matter intake (% of body weight) were lower in calves fed HPM compared with those receiving MPM. A tendency for the plane of milk intake × weaning age interaction was observed for metabolizable energy intake with the highest value was recorded with the HPM-75d calves. The lowest efficiency of metabolizable energy intake and average feed efficiency was observed in HPM-60d calves throughout the experimental period as compared with the other groups. An interaction was found between the total plane of milk intake and weaning age regarding effects on total average daily gain, average daily gain/metabolizable energy intake, feed efficiency, final body weight, and plasma β-hydroxybutyrate levels with the highest values measured in HPM-75d calves. Weaning on d 75 versus d 60 improved wither height and hip width, which tended to increase body length at the end of the trial. The results suggest that calves fed high amounts of milk during their preweaning period benefit from extending the time of weaning from 60 to 75 d of age based on average daily gain, feed efficiency, and final body weight.     

Short communication: Effects of increasing protein and energy in the milk replacer with or without direct-fed microbial supplementation on growth and performance of preweaned Holstein calves

Forty-four Holstein calves were fed a direct-fed microbial (DFM) and 1 of 2 milk replacers to evaluate calf performance and growth. Treatments were (1) a control milk replacer [22:20; 22% crude protein (CP) and 20% fat], (2) an accelerated milk replacer (27:10; 27% CP and 10% fat), (3) the control milk replacer with added DFM (22:20+D), and (4) the accelerated milk replacer with added DFM (27:10+D). Dry matter intake, rectal temperatures, respiration scores and rates, and fecal scores were collected daily. Body weight, hip and withers height, heart girth, blood, and rumen fluid samples were collected weekly. Effects of treatment, sex, week, and their interactions were analyzed. Calves fed an accelerated milk replacer, regardless of DFM supplementation, consumed more CP and metabolizable energy in the milk replacer. No treatment differences were found for starter intake or intake of neutral detergent fiber or acid detergent fiber in the starter. Calves fed the accelerated milk replacer had greater preweaning and weaning body weight compared with calves fed the control milk replacer. Average daily gain was greater during the preweaning period for calves fed the accelerated milk replacer, but the same pattern did not hold true during the postweaning period. Feed efficiency did not differ among treatments. Hip height tended to be and withers height and heart girth were greater at weaning for calves fed the accelerated milk replacer compared with calves fed the control milk replacer. Fecal scores were greatest in calves fed DFM. Overall acetate, propionate, butyrate, and n-valerate concentrations were lower in calves fed the accelerated milk replacer, but DFM did not have an effect. Rumen pH was not different. Blood metabolites were unaffected by DFM supplementation, but calves fed the accelerated milk replacer had increased partial pressure of CO₂, bicarbonate, and total bicarbonate in the blood. Direct-fed microbial supplementation did not appear to benefit the calf in this trial     

Effects of milk replacer composition on growth, body composition, and nutrient excretion in preweaned Holstein heifers

Twenty-four newborn Holstein heifer calves were fed 1 of 4 milk replacers (MR): control (20% CP, 21% fat; MR fed at 441 g/d); high protein/low fat (HPLF; 28% CP, 20% fat; MR fed at 951 g/d); high protein/high fat (HPHF; 27% CP, 28% fat; MR fed at 951 g/d); and HPHF MR fed at a higher rate (HPHF+; 27% CP, 28% fat; MR fed at 1,431 g/d). Dry calf starter (20% CP, 1.43% fat) composed of ground corn (44.4%), 48% CP soybean meal (44.4%), cottonseed hulls (11.2%), and molasses (1.0%) was offered free choice. Heifers were obtained from a commercial dairy, blocked by groups of 8 in the order acquired, and randomly assigned to treatments within group. Upon arrival at the research farm, heifers were fed the control for 2 feedings. Treatments were imposed when heifers were 4 ± 1 d of age. Heifers were on study for 61 ± 1 d. Body weight and body size measures were taken weekly. Four-day total collection of feed refusals, feces, and urine was initiated at 57 ± 1 d of age. Heifers were slaughtered at the end of the collection period to evaluate body composition. Preplanned contrasts were used to compare control to all, HPLF to HPHF, and HPHF to HPHF+. Heifers fed the control diet consumed more starter than those fed other treatment diets, but their total dry matter intake and apparent dry matter digestibility were lowest. Fecal output was highest in heifers fed the control diet, whereas urine output and urine N excretion were lowest. Nitrogen intake and urine N excretion were greater for heifers fed HPHF+ compared with HPHF but were not affected by MR fat content (HPLF vs. HPHF). Retention (g/d) of N and P was greater in heifers fed all nutrient-dense diets compared with those fed the control diet, but was not improved by increasing fat in the milk replacer (HPLF vs. HPHF) or by increasing the amount fed. Addition of fat to the milk replacer (HPLF vs. HPHF) increased empty body weight fat content without improving average daily gain or frame measures. Increasing the volume fed (HPHF vs. HPHF+) increased growth rate and empty body weight, but HPHF+ heifers were neither taller nor longer and their carcasses contained more fat. Clear improvements in growth and nutrient retention were observed with more nutrient-dense diets, but most of the improvements were seen with the increased protein intake relative to the control MR; adding fat to the high protein MR did not further improve lean tissue gain.     

Effects of feeding unlimited amounts of milk replacer for the first 5 weeks of age on rumen and small intestinal growth and development in dairy calves

The development of the gastrointestinal tract in newborn calves is essential for sufficient nutrient uptake. An intensive milk feeding during the neonatal period may impair the rumen development in calves. The aim of this study was to investigate effects of milk replacer (MR) feeding in unlimited amounts for the first 5 wk of age on the gastrointestinal growth and development in preruminant calves at wk 9 of age. Twenty-eight newborn Holstein and Holstein × Charolais crossbred calves (19 male and 9 female) were fed MR ad libitum (ADLIB) or in restricted amounts (6 L per day; RES) until wk 5 of age. Thereafter, the MR intake of ADLIB was gradually reduced at wk 6 and 7, and all calves received 6 L of MR per day until wk 9 of age. In wk 9, calves were slaughtered and carcass and organ weight as well as rumen papilla size in the atrium, ventral sac, and ventral blind sac, and villus size of the mucosa in the small intestine (duodenum; proximal, mid, and distal jejunum; and ileum) were determined. The expression of mRNA associated with the local insulin-like growth factor (IGF) system was measured in the rumen epithelium. Ad libitum MR feeding increased MR intake and growth in ADLIB without influencing concentrate intake compared with RES. Carcass weight in wk 9 was greater in ADLIB than in RES. The density of the rumen papillae in the atrium and ventral blind sac was greater in RES than in ADLIB calves, but surface area of the epithelium was not different between groups in the investigated regions of the rumen. The mRNA abundance of IGF1 in the atrium tended to be greater and the IGFR1 mRNA abundance in the ventral sac tended to be lower in the ADLIB than in the RES feeding group. The rumen pH and volatile fatty acid concentrations were not affected by MR feeding intensity. In mid-jejunum, villus circumference was greater in ADLIB than in RES calves. In the distal jejunum, villus surface area and the villus height/crypt depth ratio were greater and the villus circumference and height tended to be greater, whereas crypt depth was smaller in ADLIB than in RES calves. The findings from this study indicate that ad libitum MR feeding for 5 wk of age followed by its gradual reduction promotes growth performance without any negative influence on gastrointestinal growth and development in dairy calves at 9 wk of age.     

Supplementation of lysolecithin in milk replacer for Holstein dairy calves: Effects on growth performance,health, and metabolites

Lysolecithin is an antiinflammatory emulsifier associated with improved apparent digestibility of total dietary fat and improved feed efficiency in dairy cattle. However, it is unknown if lysolecithin (LYSO) improves performance in calves. Moreover, since many conventional milk replacers use vegetable-sourced fat (e.g., palm oil), nutrient absorption and fecal score may be affected in neonatal calves. Thus, the objective of this study was to evaluate the effects of LYSO supplemented in milk replacer on performance, metabolites, and gut health of preweaned dairy calves. Holstein calves (n = 32) with adequate passive transfer were assigned in pairs (16 blocks) balanced by birth weight, date of birth, and sex at 1 d of age to randomly receive either LYSO (mixed in 2 milk replacer feedings at a rate of 4 g/d Lysoforte, Kemin Industries Inc., Des Moines, IA) or a milk replacer control (nothing added). Both treatments were fed 6 L/d milk replacer [22.5% crude protein, 16.2% crude fat (vegetable oil fat source) on a dry matter basis with 14% solids] by bucket in 2 daily feedings for 56 d. Calves were individually housed in wooden hutches and offered a commercial calf starter (24.6% crude protein and 13.9% neutral detergent fiber) and water by bucket ad libitum. Feed refusals and calf health was assessed daily. Weights and blood metabolites (glucose, total serum protein, albumin, creatinine, triglycerides, and cholesterol) were sampled weekly, and calves completed the study before weaning at 56 d of age. The effects of LYSO on calf average daily gain, feed efficiency, and blood metabolites were evaluated using a linear mixed model with time as a repeated measure, calf as the subject, and block as a random effect in SAS (SAS Institute Inc., Cary, NC). The effect of LYSO to improve the odds of abnormal fecal score was evaluated using a logistic model. Supplementation of LYSO increased average daily gain (control 0.28 ± 0.03 kg; LYSO 0.37 ± 0.03 kg; least squares means ± standard error of the mean) and increased feed efficiency (gain-to-feed; control 0.25 ± 0.03; LYSO 0.32 ± 0.03). Similarly, LYSO calves had a higher final body weight at d 56 (control 52.11 ± 2.33 kg; LYSO 56.73 ± 2.33 kg). Interestingly, total dry matter intake was not associated with LYSO despite improved average daily gain (total dry matter intake control 1,088.7 ± 27.62 g; total dry matter intake LYSO 1,124.8 ± 27.62 g). Blood glucose, albumin, creatinine, triglycerides, and cholesterol were not associated with LYSO. Indeed, only total serum protein had a significant interaction with LYSO and age at wk 5 and 6. Moreover, control calves had a 13.57 (95% confidence interval: 9.25–19.90) times greater odds of having an abnormal fecal score on any given day during the diarrhea risk period from d 1 to 28. The inclusion of LYSO as an additive in milk replacer in a dose of 4 g/d may improve performance, and calf fecal score, preweaning. Further research should investigate the mechanisms behind the effects of LYSO on fat digestibility in calves fed 6 L/d of milk replacer with vegetable-sourced fat.     

Effects of spray-dried animal plasma in milk replacers or additives containing serum and oligosaccharides on growth and health of calves

The effects of spray-dried animal plasma in milk replacer without or with the addition of additives containing fructooligosaccharides and spray-dried serum on health, growth, and intake of Holstein calves was measured in two 56-d experiments. In experiment 1, 120 calves were fed milk replacer containing 0 or 20% of crude protein as spray-dried bovine plasma for 42 d and 30 to 60 g/d of additives containing whey protein concentrate or bovine serum for the first 15 d. Commercial calf starter was available from d 29, and water was available at all times. In experiment 2, 120 calves were fed milk replacer containing 0 or 16% of crude protein as spray-dried bovine plasma with 0 or 30 to 60 g/d of additive containing bovine serum for the first 15 d. Additive containing bovine serum also contained fructooligosaccharides, whey, and vitamin/mineral premix. In experiment 1, calves fed additive containing bovine serum tended to have fewer days with diarrhea, lower use of electrolytes, and improved BW gain from d 29 to 56. The addition of spray-dried bovine plasma to milk replacer did not influence any parameter measured. In experiment 2, calves fed additive containing bovine serum or milk replacer containing spray-dried bovine plasma had lower mortality (4.4 vs. 20%) and tended to have improved fecal scores and fewer days with scours. Antibiotic use was lower when calves were fed the additive. Indices of enteric health (incidence of scours and treatment with antibiotics and electrolytes) were improved when plasma was added to milk replacer throughout the milk feeding period or as an additive during the first 15 d of the milk feeding period, when calves were most susceptible to enteric pathogens. The addition of spray-dried animal plasma to milk replacer or the addition of additive containing spray-dried bovine serum and oligosaccharides may be a useful adjunct to animal management during periods of stress.     

Effect of milk allowance on concentrate intake, ruminal environment, and ruminal development in milk-fed Holstein calves

The aim of the present experiment was to test the hypothesis that a barley-based concentrate would induce an acidic ruminal environment in young calves and that increased milk allowance would alleviate this condition. Eight Holstein calves ruminally cannulated at d 7 ± 1 of age were used to study the effect of variation in barley-based starter concentrate intake induced by 4 different milk allowances (3.10, 4.84, 6.60, and 8.34 kg of milk replacer/d; 123 g of dry matter/kg of milk) on the ruminal environment, blood variables, and fore-stomach development from wk 2 to 5 of age. Twelve ruminal fluid samples were collected during a weekly 24-h sampling in 4 consecutive weeks. Blood samples were collected by venipuncture between 1200 and 1300 h on ruminal sampling days. Rumen papillae development and visceral organ mass were recorded at slaughter. A linear treatment × week effect was observed for concentrate intake, with the calves fed the lowest milk allowance having the fastest increase in concentrate intake whereby these calves reached the same ME intake in wk 5 compared with calves with the highest milk allowance. Effects on ruminal variables were dominated by week of sampling, with minor differences among treatments. Ruminal pH was below 5.5 for 5 to 13 h/d and all calves with concentrate intake above 20 g of dry matter/d were observed to have a daily ruminal pH minimum at pH 5.5 or lower. The ruminal concentration of total volatile fatty acids (VFA) increased from 71 to 133 ± 9 mmol/L in wk 2 to 5 and was characterized by a relatively high molar proportion of propionate, increasing from 34 to 40 mol/100 mol of VFA in wk 2 to 5. In addition, the presence of ethanol and propanol as well as numerous VFA esters points to a ruminal environment with a relatively high hydrogen pressure. Plasma glucose and insulin responded to the highest milk allowance in wk 2 to 4. Plasma VFA and ketone bodies increased with the lowest milk allowance in wk 4 to 5. At slaughter, empty wet weights of the rumen + reticulum and omasum as well as mass of digesta in these compartments were found to decrease linearly and perirenal fat was found to increase linearly with milk allowance, indicating that the milk allowance changed the body composition of the calves. Lengths of ruminal papillae in the atrium and ventral ruminal sac were not affected by treatment. We concluded that the ruminal environment of young calves fed a barley-based starter concentrate was characterized by a low ruminal pH and high VFA concentration regardless of the milk allowance.     

Effects of milk replacer composition on selected blood metabolites and hormones in preweaned Holstein heifers

We investigated the effects of increasing dietary protein and energy on concentrations of selected blood metabolites and hormones in Holstein heifers. Twenty-four heifers were fed 1 of 4 milk replacer (MR) diets for 9 wk (n = 6/diet): control [20% crude protein (CP), 21% fat MR fed at 441 g of dry matter (DM)/d], HPLF (28% CP, 20% fat MR fed at 951 g of DM/d), HPHF (27% CP, 28% fat MR fed at 951 g of DM/d), and HPHF+ (27% CP, 28% fat MR fed at 1,431 g of DM/d). Heifers were fed twice daily; water and starter (20% CP, 1.43% fat) were offered free choice and starter orts recorded daily. Serum and plasma aliquots from blood samples collected twice weekly after a 12-h fast were analyzed for insulin-like growth factor (IGF)-I, IGF-binding proteins (IGFBP), growth hormone (GH), insulin, glucose, nonesterified fatty acids, triglyceride, and plasma urea nitrogen concentrations. Only plasma glucose, IGFBP-2, and IGFBP-3 were affected by diet. Dietary treatment differences were only noted when the control was compared with the average of the other 3 diets. The addition of fat to the MR (HPLF vs. HPHF) and increased volume of MR (HPHF vs. HPHF+) had no effect on plasma glucose concentration or relative abundance of IGFBP-2 or IGFBP-3. Heifers fed the control diet had less glucose, greater IGFBP-2, and less IGFBP-3 than the average of the other 3 diets. There was a diet by week interaction for IGF-I. Serum IGF-I concentration in control heifers varied in a quadratic manner with a nadir (20 ± 4 ng/mL) at wk 4, whereas IGF-I increased linearly in heifers on other diets. Both insulin and triglyceride changed over time in a complex pattern (significant linear and quadratic contrast effects). The greatest concentrations were measured at wk 0.5 with nadirs at wk 6 for both insulin and triglyceride. Serum GH concentration decreased in a linear manner from wk 0.5 to wk 9 in all heifers. Relative abundance of IGFBP-2 was quadratic over time with the greatest amount of IGFBP-2 observed at wk 5. With the exception of glucose, IGF-I, IGFBP-2, and IGFBP-3, the blood variables measured were not influenced by treatment. The IGF-I -GH-IGFBP axis requires further study in heifers to deduce effects of nutrition on hypothalamic regulation of metabolism. We expected to see more treatment differences in concentrations of metabolites involved with protein and fat metabolism. It is likely that the diets used in this study were not diverse enough in composition to elicit such changes or that the efficiency of use of absorbed protein and fat was not different in these animals.     

Growth hormone response to growth hormone-releasing factor in selected and control Holstein heifer calves

Holstein heifer calves from selected and control lines were treated with growth hormone-releasing factor to determine whether the magnitude of the pituitary growth hormone response is associated with genetic potential for milk yield. Cows in the selected line were bred to highest Predicted Difference milk sires available each year, while control line cows were bred to bulls that were average for 1964 milk production. Eight calves from each line of similar age (206 to 210 days) and weight (205 kg average) were injected intravenously with .1 microgram/kg growth hormone-releasing factor. Dams' first lactation 305-day mature equivalent records were 10,192 +/- 495 kg for selected calves and 6,908 +/- 376 kg for control calves. Before treatment, GH tended to be higher in selected than control calves (mean +/- SE: selected = 7.5 +/- 1.8, control = 4.6 +/- .4 ng/ml). After injection, peak GH were reached within 20 min and were similar in selected and control calves, averaging 66 +/- 16 and 73 +/- 13 ng/ml, respectively. Results indicate that the magnitude of the growth hormone response to growth hormone-releasing factor is not related to future performance of dairy calves.     

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.     

Effects of repeated gram-positive and gram-negative clinical mastitis episodes on milk yield loss in Holstein dairy cows

The objective of this study was to estimate the effects of recurrent episodes of gram-positive and gram-negative cases of clinical mastitis (CM) on milk production in Holstein dairy cows. We were interested in the severity of repeated cases in general, but also in the severity of the host response as judged by milk production loss when a previous case was caused by a similar or different microorganism. The results were based on data from 7,721 primiparous lactations and 13,566 multiparous lactations in 7 large dairy herds in New York State. The distribution of organisms in the CM cases showed 28.5% gram-positive cases, 31.8% gram-negative cases, 15.0% others, and 24.8% with no organism identified. Mixed models, with a random herd effect and an autoregressive covariance structure to account for repeated measurements, were used to quantify the effect of repeated CM and several other control variables (parity, week of lactation, other diseases) on milk yield. Our data indicated that repeated CM cases showed a very similar milk loss compared with the first case. No reduction of severity was present with increasing count of the CM case. Gram-negative cases had more severe milk loss compared with gram-positive and other cases irrespective of the count of the case in lactation. Milk loss in multipara (primipara) due to gram-negative CM was approximately 304 kg (228 kg) in the 50 d following CM. This loss was approximately 128 kg (133 kg) for gram-positive cases and 92 kg (112 kg) for other cases. The severity of a second case of gram-negative CM was not reduced by previous cases of gram-negative CM in multipara and only slightly less severe in a similar scenario in primipara cows. Similarly, a previous gram-positive case did not reduce severity of a second or third gram-positive case. Hence, our data do not support that immunological memory of previous exposure to an organism in the same generic class provides protection for a next case of CM with an organism in the same class.