Partial replacement of triticale for corn grain in starter diet and its effects on performance,structural growth and blood metabolites of Holstein calves

The primary objective of this study was to examine the effects of different inclusion rates of dietary triticale replacing corn grain in starter rations of dairy calves on feed intake, average daily gain (ADG), feed efficiency, skeletal growth, fecal score, and selected blood and ruminal parameters. In all, 30 4-day-old Holstein calves (15 female and 15 male) were blocked by gender and birth weight, and then randomly allotted to three treatment groups (n=10 calves/treatment) and received either a corn-based diet without triticale (T0), or a diet containing 16% (T16) or 32% (T32) triticale (25% and 50% corn replaced by triticale, respectively) for 10 weeks. Calves were weaned on day 43 of study and remained on the study until day 70. During post-weaning period, calves fed T32 had the lowest starter intake (1.78 kg/day; P=0.02). In contrast, ADG was not affected in pre-weaning and overall periods, but calves fed T32 had a lower ADG (P=0.04) as compared with calves fed T0 in post-weaning period. No dietary effect was detected for feed efficiency. Dietary treatment did not affect heart girth and body length; however, height at wither and hip at weaning increased in calves fed triticale compared with T0. No detectable effects were observed in serum glucose and β-hydroxybutyrate. No difference was detected in blood urea nitrogen on day 35 either but on day 50 and day 70 the greatest concentration was recorded for calves fed T16. Compared with the control, ruminal ammonia concentration was increased for calves fed T32 (4.34 v. 7.50 mmol/l) and T16 (4.01 v. 8.12 mmol/l) on day 35 and day 50. No difference was detected in ruminal pH on day 35 or day 50; however, calves fed T32 had the lowest pH (6.11) at 70 days. No significant effect was detected in days scoured, respiratory score and general appearance. Under our experimental conditions, it appears that triticale at 16% dry matter (i.e. replacing corn grain up to 25%) in the starter diet does not have adverse effects on the performance and intake of calves. Therefore, substituting corn partially with triticale in calf starter diets may prove beneficial in places where corn is less abundant or its price is prohibitive. The low number of calves per treatment however may have limited the statistical power to detect significant differences among treatments, possibly affecting the results, which should be interpreted with caution.     

Effects of wheat straw particle size as a free-choice provision on growth performance and feeding behaviors of dairy calves

In the dairy calf feeding, supplementation of forage to the starter feed is commonly practiced. However, data are insufficient about how changes in particle size (PS) of forage affect calf performance and behavior in a free-choice forage provision system. This study aimed to assess the effects of supplementing wheat straw varying in PS on performance, skeletal growth characteristics, ruminal pH, nutritional behaviors, and blood metabolites of dairy calves. Forty-eight Holstein calves (43.8 ± 3.2 kg of BW) from d 15 of age were randomly assigned to one of the four treatments (n = 12/treatment; six males and six females): (1) starter without wheat straw supplementation (CON), (2) CON supplemented with wheat straw chopped at 1 mm geometrical mean particle length (GMPL) (fine PS), (3) CON supplemented with wheat straw at 4 mm GMPL (medium PS), and (4) CON supplemented with wheat straw at 7 mm GMPL (long PS). The calves were given ad libitum access to feed and water throughout the study. All calves were weaned on d 56 of age and continued the experiment until d 90. The starter, wheat straw, and total solid feed intakes were not affected by GMPL of wheat straw; however, CON calves had a lower solid feed-, total DM- and NDF-intake than calves offered wheat straw. Further, ADG, weaning, and final BWs as well as feed efficiency were similar between treatments. No difference was observed in growth rate of hip height, hip width, body barrel, wither height, and heart girth among treatments, however, wheat straw supplemented calves tended to have greater body length at weaning. Blood concentration of serum β-hydroxy butyrate was greater in wheat straw supplemented calves compared with CON calves on d 56 and 90. Calves supplemented with wheat straw spent more time eating starter and forage, lying and ruminating and less time for standing and non-nutritional behaviors compared with the CON calves on d 49 and 63 of the study. Moreover, calves offered wheat straw had greater ruminal pH than CON calves at 4 and 8 h after offering starter feed on d 35. In conclusion, supplementing wheat straw as a free-choice increased solid feed intake, rumen pH, and calves' welfare, however, PS of wheat straw had no effect.     

Reciprocal combinations of alfalfa hay and corn silage in the starter diets of Holstein dairy calves: effects on growth performance,nutrient digestibility,rumen fermentation and selected blood metabolites

Adding corn silage (CS) instead of alfalfa hay (AH) to the finely ground starter diet would improve calf performance if feed intake or feed efficiency is increased. We investigated the effects of replacing AH with CS in the starter diet on nutrient intake, digestibility, growth performance, rumen fermentation and selected blood metabolites in Holstein calves. Newborn male calves (n = 30; 3 days of age; 40.2 ± 1.28 kg BW) were assigned randomly to three groups receiving starter diets containing chopped AH (10% dry matter (DM) basis; AH diet), CS (10% DM, CS diet) or their combination (each at 5% level; AHCS diet). The starter diets had the same nutrient composition but differed in DM content (91.2%, 87.5% and 83.8% for AH, AHCS and CS, respectively). The calves were weaned on day 50, and the study continued until day 70. Nutrient intake, BW (at weaning and at the end of the study) and body measurements were not affected by the diet. During the post-weaning period, average daily gain tended to be greater on CS than on AH diet. Feed efficiency was greater in CS than in AH or AHCS calves during the post-weaning period. Digestibility of neutral detergent fiber was greater in AHCS and CS compared with AH during the post-weaning period. Concentration and profile of volatile fatty acids and ruminal fluid pH were not affected by the diet. Replacing AH with CS in the starter diet had no effect on feed intake, growth performance and general health of the calves. These results indicate that AH and CS can be used interchangeably in dairy calf starter diets until 70 days of age, allowing dairy producers more choices in selecting the feed ingredients.     

Determining optimum age of Holstein dairy calves when adding chopped alfalfa hay to meal starter diets based on measures of growth and performance

The present study was conducted to determine the optimum age of Holstein dairy calves for an effective inclusion of alfalfa hay (AH) in starter feed on performance, apparent digestibility and feeding behavior. A total of 40 Holstein dairy calves (20 female and 20 male) were used in a completely randomized design in which calves were randomly assigned to one of four different dietary treatments including control (CON) calves fed starter feed without any forage and three treatments consisting of the same starter feed plus 15% chopped AH fed when calves were at the 2^nd (AH2), 4^th (AH4) or 6^th (AH6) week of age. Calves were individually housed and bedded with sand that was replaced every other day. Feed and water were available ad libitum throughout the experiment. Calves were fed milk at 10% of birth BW twice daily until d 57. The study concluded when calves were 73 days old. Starter intake was recorded daily and BW was measured weekly. Data were analyzed as a complete randomized design by MIXED procedures of SAS. Results demonstrate that calves receiving AH treatments numerically consumed more starter feed (0.62 v. 0.78, 0.71 and 0.65 kg/day for CON, AH2, AH4 and AH6, respectively) and had greater average daily gain (ADG) compared with CON (0.48 v. 0.57, 0.49 and 0.49 kg/day for CON, AH2, AH4 and AH6), although the significant difference was observed only between AH2 and CON. Among AH treatments, calves in AH2 had better performance than AH6 in several cases including starter intake, ADG. No detectable differences were observed, however, in apparent dry matter, organic matter or CP digestibility among treatments. Ruminal pH and NH₃ concentrations, measured on weeks 4, 6, 8 and 10, were lower for calves fed CON compared with other treatments, with ammonia concentrations decreasing over time. Calves in the AH treatments spent more time eating and ruminating compared with CON. Calves fed CON, however, spent more time on laying down compared with other treatments. Overall, results from the present study illustrated that inclusion of alfalfa in starter feed for calves at 2 weeks of age may improve feed intake, ADG and stimulate rumination in young Holstein dairy calves. Results, however, should be viewed with caution as the number of calves per treatment was small and large calf-to-calf variation may have affected the results reported.     

Effect of oat hay provision method on growth performance,rumen fermentation and blood metabolites of dairy calves during preweaning and postweaning periods

The comparison of the effects of all forage offering methods would be particularly useful information in modeling growth performance and rumen fermentation of dairy calves. Therefore, this study attempted to evaluate the effects of methods of oat hay provision on growth performance, rumen fermentation and biochemical blood indices of dairy calves during preweaning and postweaning periods. At birth, 40 female Polish Holstein-Friesian calves (3 days of age; 39.6 ± 0.39 kg BW) were randomly assigned to four treatment groups differing in the access to chopped oat hay: CON (control, starter without oat hay), OH (starter feed containing 10% DM basis oat hay), OH-FC (starter feed containing 10% DM basis oat hay and oat hay fed as free-choice provision in different buckets) and FC (starter feed and oat hay fed as free-choice provision in different buckets). The calves were weaned on day 56, and then the study continued until day 84. Intakes of starter feed and oat hay were recorded daily, whereas BW and hip height (HH) on day 3 and then every 14 days. Samples of blood were collected on the initiation of experiment and then every 14 days, and rumen contents on day 28, 56 and 84. No treatment effects were found for starter, starch, CP, total DM intake, average daily gain, feeding efficiency, change in HH, ruminal fluid pH, concentrations of ruminal propionate and NH₃-N, concentrations of urea nitrogen and non-esterified fatty acids in the blood. There were differences between treatments in terms of ruminal total volatile fatty acids and molar concentrations of acetate, butyrate and acetate to propionate ratio; highest in OH and OH-FC groups, especially during the postweaning period. On the other hand, lower concentrations of iso-valerate were found in OH and OH-FC groups on day 56 and 84. The concentrations of IGF-I throughout the experiment and β-hydroxybutyrate during the postweaning period in the blood were influenced by treatment, with the greatest values observed in OH and OH-FC calves. Results of this study indicate that starter feed containing chopped oat hay improves rumen fermentation parameters, which might allow successful transition from preruminant to mature ruminant state. Also, providing chopped oat hay with pelleted starter feed seems to be a better method than free-choice supplementation.     

Grain source and chromium supplementation: effects on feed intake,meal and rumination patterns,and growth performance in Holstein dairy calves

Carbohydrate-rich diets may increase urinary excretion of chromium (Cr) and increase its requirements. This study was conducted to investigate the effect of grain type (barley v. corn) and Cr supplementation on feed intake, feeding behavior and weight gain in dairy calves. Forty-eight neonatal Holstein female calves were assigned randomly to four experimental diets in a 2×2 factorial arrangement. Experimental diets were either barley-based diet (BBD) or corn-based diet (CBD) supplemented with (+Cr) or without (−Cr) Cr as Cr-methionine (0.05 mg/kg of BW^0.75). Chromium was provided in milk (from days 3 to 73 of life) during the pre-weaning period and then in pre-warmed water (from day 74 until day 94 of life) after weaning. Meal length tended to increase in calves fed the BBD v. CBD during the pre-weaning period. During the post-weaning period, meal size, inter-meal interval, and eating rate increased concurrently but meal frequency and eating time decreased in the BBD v. CBD. During the pre-weaning period, feed efficiency, BW at weaning, and heart girth increased and non-nutritive oral behaviors tended to decrease with Cr supplementation. Due to increased meal frequency, the starter feed intake but not eating time increased by Cr supplementation during the post-weaning period. Supplementing Cr increased starter feed intake, final BW, average daily gain and heart girth during the overall period. Rumination time increased in BBD+Cr calves due to increases in the frequency and duration of rumination, or decreased rumination bout interval. Overall, the type of grain had no effect on feed intake and growth performance; however, Cr supplementation decreased non-nutritive oral behaviors and increased starter feed intake via increasing the meal frequency and thereby improved growth performance.     

Effects of physical forms of starter feed on growth,nutrient digestibility,gastrointestinal enzyme activity,and morphology of pre- and post-weaning lambs

The physical form of starter feed may affect the gastrointestinal development and the performance of ruminant. However, little information is available on how changes in the physical forms of starter feed influence the performance of lambs, especially during the pre- and post-weaning periods. The aim of this study was to investigate the effects of different physical forms of starter feeds on growth performance, nutrient digestibility, gastrointestinal enzyme activity, and morphology of pre- and post-weaning lambs. Twenty-four 8-day-old male Hu lamb (5.04 ± 0.75 kg BW) were randomly assigned to one of two dietary treatments: 1) a pelleted starter (PS) feed and 2) a textured starter (TS) feed, which included coarse mashed steam-flaked corn. From eight to thirty-five days of age (pre-weaning), the lambs were bottle-fed milk replacer (MR) at 2% of BW measured on day 8. All lambs were weaned at day 35 when feeding of MR was stopped. Six lambs for each treatment were euthanized at 21 or 42 days of age for sampling. The following results are obtained by variance analysis: TS lambs had a greater (P < 0.05) final BW, higher apparent digestibility of starch and ether extract, activities of α-amylase pre- or post-weaning, and higher (P < 0.05) average dry matter intake and lipase post-weaning in small intestine contents and had a trend of significantly higher average daily gain post-weaning (P = 0.07). Rumen development analysis of TS lambs showed a significantly higher (P < 0.05) relative weight of rumen post-weaning, greater papillae length, increased circular and layered muscle, increased sectional area pre- and post-weaning, and increased rumen papillae width post-weaning. Textured starter treatment increased the villus height and villus width (except jejunum pre-weaning) of the whole small intestine and villus height to crypt depth ratio of jejunum and ileum during the whole period and tended to increase the relative weight of the rumen pre-weaning (P = 0.07). The results indicated that TS feeding is more beneficial to lambs over the weaning transition than PS in promoting gastrointestinal development, intestinal enzyme activities, nutrient digestibility, and growth performance. The findings provide new insights into the selection of physical forms of starter feeds in lamb production. Further research with more animals and female lambs is needed to obtain a more complete conclusion.     

The effects of feeding high or low milk levels in early life on growth performance,fecal microbial count and metabolic and inflammatory status of Holstein female calves

Gut microbial colonization and immune response may be affected by milk feeding method. The objective of this study was to determine the effects of feeding high or low volumes of milk on fecal bacterial count, inflammatory response, blood metabolites and growth performance of Holstein female calves. Colostrum-fed calves (n = 48) were randomly assigned to either high milk (HM; n = 24) or low milk (LM; n = 24) feeding groups. Low milk-fed calves were fed pasteurized whole milk at 10% of BW until weaning. In HM group, milk was offered to calves at 20% of BW for the first 3 weeks of life. Then, milk allowance was decreased gradually to reach 10% of BW on day 26 and remained constant until weaning on day 51. Calves were allowed free access to water and starter throughout the experiment. Body weight was measured weekly, and blood samples were taken on days 14, 28 and 57. Fecal samples were collected on days 7, 14 and 21 of age for the measurement of selected microbial species. By design, HM calves consumed more nutrients from milk during the first 3 weeks and they were heavier than LM calves on days 21, 56 and 98. High milk-fed calves had greater serum glucose and triglyceride levels on day 14 with no significant difference between groups on days 28 and 57. Blood urea nitrogen was higher in LM calves on day 14, but it was lower in HM calves on day 28. Calves in LM group had significantly greater blood tumor necrosis factor-α (TNF-α) than HM calves throughout the experiment. Serum amyloid A (SAA) concentration was higher in LM calves on day 14. However, HM calves showed higher levels of SAA at the time of weaning. Feeding high volumes of milk resulted in lower serum cortisol levels on days 14 and 28 but not at the time of weaning in HM calves compared to LM counterparts. Lactobacillus count was higher in feces sample of HM calves. Conversely, the numbers of Escherichia coli was greater in the feces of LM calves. Calves in HM group showed fewer days with fever and tended to have fewer days treated compared to LM group. In conclusion, feeding higher amounts of milk during the first 3 weeks of life improved gut microbiota, inflammation and health status and growth performance of Holstein dairy calves.     

Influence of spray-dried rumen fluid supplementation on performance,blood metabolites and cytokines in suckling Holstein calves

Rumen fluid from slaughtered animals is one of the wastes of slaughterhouses released to the environment that, due to its high nitrogen and phosphorus contents, can lead to soil and groundwater pollution. Meanwhile, it contains ruminal microbes and some bioactive compounds such as enzymes, minerals, vitamins and organic acids. This study was designed to examine the potential of rumen fluid as a feed additive. Therefore, the effects of spray-dried rumen fluid (SDR) with 1% maltodextrin on the performance, blood metabolites and some cytokines of sucking dairy calves during the pre-weaning phase were investigated. Forty male Holstein calves, with a mean weight of 39.4 ± 3.7 kg and 7 ± 1 days old, were randomly assigned to four groups (n = 10 calves per group) in a completely randomized design. Experimental treatments were: control diet with no additive (CON); control diet with 0.5 g/day of SDR (SDR0.5); control diet with 1 g/day of SDR (SDR1); and control diet with 1.5 g/day of SDR (SDR1.5). Daily feed intake and average daily gain of calves were not affected by feeding SDR as a feed additive. Cholesterol concentration was significantly affected by the 20th and 40th days of the experiment and decreased linearly by increasing SDR feeding level. Levels of liver enzymes, including aspartate aminotransferase and alanine aminotransferase, in the blood decreased by feeding SDR at day 40 of the experiment. Serum concentration of interleukin-6 at day 20 was not affected by dried rumen fluid feeding, whereas at day 40, a significant effect was observed among experimental treatments. The lowest value was recorded for SDR1.5 v. control calves. At day 20, the serum concentration of interferon-γ was influenced by supplementing SDR, and the highest value was recorded for SDR1.5 calves. The inclusion of SDR with 1% maltodextrin in suckling dairy calves had beneficial effects on the stimulation of calves’ immune system.     

Essential oils for dairy calves: effects on performance,scours, rumen fermentation and intestinal fauna

The first cause of death of dairy calves is often diarrhea which is mainly caused by pathogenic bacteria, which can result in excessive use of antibiotics. However, facing the increase concern by the industry and consumers, the use of antibiotics not only to control pathogens, but also to manipulate growth, has become a challenge. Alternative additives, such essential oils, have the potential to decrease antibiotic use, without reducing performance or increasing mortality of dairy calves. The objective of this study was to evaluate the use of a commercial blend of essential oils, incorporated into the calf starter and/or milk replacer to monitor the effect on overall calf performance, fecal scores and rumen fermentation parameters. A total of 30 Holstein calves received 6 l/day of a liquid diet, consisting of a commercial milk replacer containing 20% CP : 15% fat (EE). Calves had free choice access to water and calf starter. Weaning occurred at week 8, and calves were followed until the 10^th week of age. Calves were assigned to one of the three treatment groups in a randomized block design. Treatments: (1) control without essential oils supplementation (C); (2) essential oils blend in the milk replacer at 400 mg/kg (MR) and (3) essential oils blend in the milk replacer (200 mg/kg) and starter feed (200 mg/kg) (MRS). From the 2^nd week, calves were weighed and body measurements were taken, while concentrate intake and fecal scores were monitored daily. Blood samples were drawn weekly for determination of glucose and β-hydroxybutyrate. Fecal samples were collected weekly and analyzed for lactic acid bacteria and Enterobacteria; and ruminal fluid for determination of pH, short chain fatty acids, ammonia-N and counts of amylolytic and cellulolytic bacteria, and protozoa. Performance, fecal scores and intestines microorganisms were not affected by the essential oils supplementation. Ruminal and blood parameters were also not affected, with the exception the rumen ammonia-N concentration, with higher values when essential oils were supplemented in a combination of milk replacer and starter feed. Most of the evaluated parameters were affected by age of calves, mainly as a response to the increase in concentrate intake as animals’ aged. Essential oils are promising substitutes for antibiotics. However, the dose and routes of administration deserve further studies, allowing a better animal performance and health to be achieved.     

Extended transition milk feeding for 3 weeks improves growth performance and reduces the susceptibility to diarrhea in newborn female Holstein calves

Dairy calves may benefit from extending the duration of feeding transition milk (TM; the subsequent two to six milkings after parturition) to enhance performance and health during early life. The objective of this study was to assess the effect of replacing pasteurized waste milk (non-saleable milk containing antibiotic and/or drug residues) with pasteurized TM for 3 weeks on the growth performance and health of dairy calves. A total of 84 healthy newborn female Holstein calves were blocked by birth order and assigned randomly to 4 treatment groups with partial replacement of pasteurized waste milk by TM (second milkings after parturition) at 0 (0 l/day TM + 6 l/day milk), 0.5 (0.5 l/day TM + 5.5 l/day milk), 1 (1 l/day TM + 5 l/day milk), or 2 l (2 l/day TM + 4 l/day milk) for a 21-day period. From day 22 onward, all calves were fed individually with 6 l/day pasteurized waste milk. Calves were weaned on day 60 and monitored until day 90 of the study. Liquid feed DM intake (DMI) was increased with increasing levels of TM (P = 0.001). Starter feed DMI and total DMI (liquid feed DMI + starter feed DMI) were not affected by the treatment effect. Calves were fed 2 l/day TM gained more BW compared with those in the control group during the postweaning and overall periods. The average daily gain tended (P = 0.06) to be higher in calves fed 2 l/day TM compared with calves fed 0 (+ 65 g/day), 0.5 (+ 53 g/day), or 1 (+ 76 g/day) l/day TM during the preweaning period. Daily weight gain was also higher in calves fed 2 l/day TM compared with calves in the control group during the postweaning (+ 137 g/day; P = 0.04) and overall (+ 89 g/day; P < 0.01) periods, respectively. Calves fed 2 l/day TM had a higher feed efficiency compared with calves in the control group during all studied periods. The calves fed TM2 had a lower chance of having diarrhea compared with other treatment groups. Duration but not the frequency of diarrhea was lower in calves fed TM2 vs TM0 (2.5 vs 4.2 days; P = 0.03). In general, partial replacement of waste milk with TM (2 l/day) may be recommended to feed dairy calves at an early stage of life to support a higher growth rate and health benefits.     

Effects of folic acid on growth performance,ruminal fermentation,nutrient digestibility and urinary excretion of purine derivatives in post-weaned dairy calves

This study evaluated the effects of folic acid (FA) supplementation on growth performance, ruminal fermentation, nutrient digestibility and urinary purine derivatives (PD) excretion in dairy calves. Forty-eight Chinese Holstein male dairy calves at 60 ± 3.2 d of age and 89 ± 5.9 kg body weight (mean ± standard error) were assigned to one of four groups in a randomised block design. Calves in control group were fed basal diet, calves in low FA, medium FA and high FA groups with 3.6, 7.2 and 10.8 mg FA per kg basal diet, respectively. The dietary corn silage to concentrate ratio was 50:50 (dry matter [DM] basis). DM intake and average daily gain (ADG) quadratically increased, and feed conversion ratio quadratically decreased with increasing FA supplementation. Ruminal pH linearly decreased, whereas total volatile fatty acids quadratically increased. The unchanged acetate-to-propionate ratio was due to the similar change in acetate and propionate concentration. Ammonia N content quadratically decreased. Digestibility of DM, organic matter, crude protein, ether extract, neutral detergent fibre and acid detergent fibre linearly increased. Activities of carboxymethyl cellulase, cellobiase, xylanase and pectinase linearly increased, but α-amylase and protease quadratically increased. Abundance of Ruminococcus albus, Ruminococcus flavefaciens and Fibrobacter succinogenes linearly increased, but Butyrivibrio fibrisolvens and Prevotella ruminicola quadratically increased. Urinary total PD excretion quadratically increased. The results indicated that FA supplementation increased ADG, ruminal fermentation and nutrient digestibility with promoted ruminal microbial growth and enzyme activity, and the optimum dose was 7.2 mg FA per kg basal diet for calves.     

Nutrient intake,rumen fermentation and growth performance of dairy calves fed extruded full-fat soybean as a replacement for soybean meal

The objective of this study was to investigate the effects of extruded full-fat soybean (ESB) as a replacement for soybean meal (SBM) on nutrient intake, rumen fermentation, and growth performance of dairy calves. A total of 45 male Holstein dairy calves (42.0±0.5 kg of BW) were randomly assigned to one of three experimental diets: (1) 0% ESB (Control): 35.3% SBM no ESB; (2) 25% ESB: 27.0% SBM+9.0% ESB; and (3) 50% ESB: 19.0% SBM+19.0% ESB. All calves were weaned on day 56 of age and remained in the study until day 70 of age. During the pre-weaning and overall periods, substituting of SBM with ESB had no effect on intake of starter feed, metabolizable energy (ME), CP and non-fiber carbohydrate (NFC). Compared with the control, 50% ESB resulted in a decrease in starter feed intake, and intakes of other nutrients including CP, NFC and ME during the post-weaning period. Substituting SBM with ESB decreased intake of C16 : 0 and increased intakes of n-9 C18 : 1, n-6 C18 : 2 and n-3 C18 : 3 during the pre-weaning, post-weaning and overall periods. Using ESB as a replacement for SBM did not affect average daily gain, feed efficiency, rectal temperature and fecal score over the trial periods. Compared with control, the rumen concentration of NH₃-N decreased for 50% ESB on days 35 and 56 of age but not when compared with 25% ESB. Rumen pH, total volatile fatty acids concentrations, and the molar proportions of ruminal acetate, propionate and butyrate were not different among treatments. Body measurements were not affected by the treatments. In conclusion, substitution of SBM with ESB may improve nitrogen utilization efficiency in dairy calves but slightly reduce post-weaning starter intake with no negative outcomes on growth performance and rumen fermentation.     

Metabolic and performance responses to the replacement of lactose by fat in milk replacer formulations for dairy calves

The recent trend in the dairy industry towards elevated planes of milk feeding of young calves requires reconsideration of calf milk replacer (CMR) formulations. The fat:lactose ratio in CMR is typically lower than that of whole milk and effects of increasing fat inclusion at the expense of lactose in CMR on nutrient metabolism and gut function of rearing calves are not sufficiently understood. Therefore, the current study aimed to determine the effect of increasing replacement of lactose by fat on growth performance, nutrient digestibility and metabolism, and glucose/insulin sensitivity. A total of 40 male calves (1.7 ± 0.10 days of age, 46.7 ± 0.76 kg BW) were blocked based on arrival date and randomly assigned to one of four treatments containing differing levels of fat and lactose (18F: 18.8% and 47.6%; 22F: 22.3% and 42.8%; 26F: 26.0% and 38.6%; 30F: 30.1% and 33.8%, fat and lactose DM, respectively). Calves were individually housed for the duration of the 11 week study and received their CMR (150 g/L) twice a day (0700 and 1600 h) from a teat bucket. The CMR feeding schedule consisted of 6 L/d from d 2 to 14, 7 L/d from d 15 to 56, and then 4 L/d during gradual weaning from 56 to 63 days. Pelleted starter, chopped straw, and water were available ad libitum throughout the study. Measurements included feed intake, growth, nutrient digestibility, fecal composition, and blood parameters. A glucose tolerance test (GTT) was performed between 28 and 32 days of age. By design, metabolizable energy intake from CMR increased linearly with fat level, but this did not result in a difference in BW, ADG, or concentrate intake. Fecal composition remained unaffected by treatment except for higher fat content in 22F compared to 26F. Also, plasma non-esterified fatty acids and total bilirubin differences were limited to 22F having the highest values whereas 26F had the lowest values. Regarding the GTT, total area under the curve (AUC) for glucose was highest in 22F and 26F and lowest in 18F whereas the AUC between 30 and 60 min for glucose was highest in 26F and lowest in 18F and 22F. Overall, altering the lactose:fat ratio in CMR did not affect growth performance while having minor effects on nutrient metabolism, but future investigation should focus on physiological consequences and effects in adult life to understand biological impact of fat and lactose levels in CMR for rearing calves.     

Rubber seed oil and flaxseed oil supplementation alter digestion,ruminal fermentation and rumen fatty acid profile of dairy cows

Rubber seed oil (RO) that is rich in polyunsaturated fatty acids (FA) can improve milk production and milk FA profiles of dairy cows; however, the responses of digestion and ruminal fermentation to RO supplementation in vivo are still unknown. This experiment was conducted to investigate the effect of RO and flaxseed oil (FO) supplementation on nutrients digestibility, rumen fermentation parameters and rumen FA profile of dairy cows. Forty-eight mid-lactation Holstein dairy cows were randomly assigned to one of four treatments for 8 weeks, including basal diet (CON) or the basal dietary supplemented with 4% RO, 4% FO or 2% RO plus 2% FO on a DM basis. Compared with CON, dietary oil supplementation improved the total tract apparent digestibility of DM, neutral detergent fibre and ether extracts ( P < 0.05). Oil treatment groups had no effects on ruminal digesta pH value, ammonia N and microbial crude protein ( P > 0.05), whereas oil groups significantly changed the volatile fatty acid (VFA) profile by increasing the proportion of propionate whilst decreasing total VFA concentration, the proportion of acetate and the ratio of acetate to propionate ( P < 0.05). However, there were no differences in VFA proportions between the three oil groups (P > 0.05). In addition, dietary oil supplementation increased the total unsaturated FA proportion in the rumen by enhancing the proportion of trans-11 C18:1 vaccenic acid (VA), cis-9, trans-11 conjugated linoleic acid (CLA) and α-linolenic acid (ALA) ( P < 0.05). These results indicate that dietary supplementation with RO and FO could improve nutrients digestibility, ruminal fermentation and ruminal FA profile by enhancing the VA, cis-9, trans-11 CLA and ALA composition of lactating dairy cows. These findings provide a theoretical basis for the application of RO in livestock production.     

Feeding behaviour and activity as early indicators of disease in pre-weaned dairy calves

Across the industry, there is large variation in health status of dairy calves and as a result, disease incidence and antibiotic use is high. This has significant implications for animal welfare, productivity and profitability of dairy and dairy-beef production systems. Technology-based early detection systems could alleviate these issues; however, methods of early detection of disease in dairy calves have not been widely explored. This study aimed to determine whether changes in activity and feeding behaviour can be used as early warning indicators of respiratory disease in calves. In total, 100 pre-weaned male Holstein calves (age: ~ 8−42 days) were used. Calves were group-housed and provided with starter diet, straw bedding and ad libitum water. Calves were fed milk replacer ad libitum through an automatic calf feeder, and each calf was fitted with a leg-mounted activity monitor. Daily activity and feeding behaviour variables were calculated for each calf. Each calf was assessed daily using a modified version of the Wisconsin Scoring System to assess respiratory disease status. Calves were classed as ‘Diseased’, ‘Intermediate’ or ‘Healthy’ based on their cumulative health score. The peak day of the most extreme illness event was identified for each calf. Data from Diseased and Healthy calves were paired for analysis based on age and BW. Data were compared for the day of peak illness, and for the 3 days previous and post. Compared to healthy calves, diseased calves lay for longer and tended to have longer lying bouts (daily lying: 17.6 ± 0.3 vs 16.7 ± 0.2 h, P < 0.01; bout length: 74.8 ± 10.6 vs 56.0 ± 3.7 min, P = 0.09 for diseased and healthy calves, respectively). Diseased calves fed for a shorter time and had fewer feeder visits (with intake) each day compared to healthy calves (feeding time (min): 19.3 ± 1.4 vs 22.8 ± 1.5; P < 0.05; visits: 2.1 ± 0.2 vs 3.2 ± 0.4; P < 0.05). Importantly, differences between diseased and healthy calves were evident in both activity and feeding behaviour on the days prior to the peak day of disease. Lying bout length was greater in diseased calves for the 2 days prior to the peak day (P < 0.05), lying time was longer on day − 1 (P < 0.05) and feeder visits with milk intake were less frequent on day − 3 (P < 0.05). Thus, measurement of feeding and activity using precision technology within early detection systems could facilitate early intervention and optimized treatment.     

Effect of alfalfa hay and starter feed supplementation on caecal microbiota and fermentation,growth, and health of yak calves

The caecum is the primary site where microbial fermentation and acidosis occurred. The supplementation of starter feed and alfalfa hay has the potential to influence caecal microbiota and then affect caecal fermentation. This study aims to investigate the effect of starter feed and alfalfa hay supplementation on caecal microbiota, immune homeostasis, and growth of preweaning yaks. Twenty 30-day-old male yak calves were randomly assigned to four groups, which separately fed with milk replacer (CON group), milk replacer with alfalfa hay (A group), milk replacer with starter feed (S group), and milk replacer with starter feed plus alfalfa hay (SA group) throughout the trial. Growth performance and plasma physiological and biochemical indicators were measured every 30 days. Calves were sacrificed at 120 days of age. The caecal contents were collected for measuring pH and contents of volatile fatty acids (VFAs) and lipopolysaccharide (LPS) and for characterizing caecal microbiota. The results indicated that individual or simultaneous supplementation with alfalfa hay and starter feed all significantly increased the BW, body height, body length, and chest girth of yak calves. However, supplementation with starter feed significantly increased plasma cortisol, nitric oxide, tumor necrosis factor-α, and interferon-γ concentrations and the ratio of aspartate aminotransferase to alanine aminotransferase of yak calves when compared with the control and alfalfa hay feeding groups, while the co-supplementation of starter feed and alfalfa hay could significantly decrease these inflammation-related indices when compared with the starter feeding group. Sequencing of the 16S rRNA gene showed that starter feed and alfalfa hay separately stimulated the proliferation of starch-decomposing and cellulose- or hemicellulose-decomposing bacteria. This also significantly increased the levels of acetate, propionate, butyrate, valerate, isobutyrate, and isovalerate in the caecal contents. Furthermore, compared with the S and CON groups, the significantly increased genera of Desulfobulbus, Olsenella, Pseudoflavonifractor, and Stomatobaculum in the SA and A groups were beneficial to the immune homeostasis, and the significantly decreased Blautia, Clostridium IV, Bacteroides, Eubacterium, Clostridium XVIII, and Mogibacterium in the SA and A groups were related to the reduced caecal lactate and LPS contents, the decreased inflammatory reaction, and the improved healthy hepatic condition of yak calves. In conclusion, milk replacer supplemented with alfalfa hay and starter feed is recommended during preweaning to improve yak calf health and growth because this regimen promotes the growth and maintains the immune homeostasis of yak calves.     

Effects of isovalerate supplements on morphology and functional gene expression of rumen mucosa in pre- and post-weaning dairy calves

Isovalerate supplements could stimulate rumen development by improving morphology and function of rumen mucosa, and then promote the growth of calves. This study was done to evaluate the effects of isovalerate supplements on morphology and functional gene expression of rumen mucosa in dairy calves. In total, 48 Chinese Holstein male calves with 15 days of age and 45.1±0.36 kg of BW were randomly assigned to four groups. The treatments were: control, low-isovalerate, moderate-isovalerate and high-isovalerate with 0, 3, 6 and 9 g isovalerate per calf per day, respectively. Supplementary isovalerate was hand-mixed into milk in pre-weaning calves and into concentrate portion in post-weaning calves. The study consisted of a 15-day-adaptation period and a 60-day-sampling period. Calves were weaned at 60 days of age. Three calves were slaughtered from each of the four treatments at 30, 60 and 90 days of age. The weight of body and stomach were measured, samples of ruminal tissues and blood were analyzed. Total stomach weight, total stomach to BW ratio, rumen wall and keratinized layer thickness, serum growth hormone and IGF-1 for both pre- and post-weaning calves increased linearly with increasing isovalerate supplements. Rumen to total stomach weight ratio, the length and width of rumen papillae, and serum β-hydroxybutyrate increased linearly for post-weaning calves. However, abomasum weight to total stomach weight ratio decreased linearly for both pre- and post-weaning calves. The relative messenger RNA expression for growth hormone receptor, IGF-1 receptor and 3-hydroxy-3-methylglutaryl-CoA synthase 1 in rumen mucosa increased linearly for post-weaning calves. Our results suggested that isovalerate supplements promoted rumen development in a dose-dependent manner. The optimum dose was 6.0 g isovalerate per calf per day.     

Lactational performance,feeding behavior,ruminal fermentation and nutrient digestibility in dairy cows fed whole-plant faba bean silage-based diet with fibrolytic enzyme

Whole-plant faba bean silage has a high content in indigestible fiber. Improvement of fiber digestibility of faba bean silage would benefit animal production. However, there is no study on pretreating fibrolytic enzyme in whole-plant faba bean silage-based diet for dairy cows on animal performance. The objectives of this study were to evaluate the effects of pretreating whole-plant faba bean silage-baseddiet with fibrolytic enzyme (a mixture of xylanase and cellulase; AB Vista, UK) derived from Trichoderma reesei (FETR) on lactational performance, digestibility, ruminal fermentation characteristics, and feeding behavior of dairy cows. The animal trial was conducted using eight lactating Holstein cows (BW = 710 ± 44 kg and Days in Milk (DIM) = 121 ± 17 days) with four levels of FETR (0, 0.5, 0.75, and 1.0 mL of FETR/kg DM of silage) in a replicated Latin square design. These enzyme treatments were selected based on the previous in situ and in vitro findings that showed positive responses to the whole-plant faba bean silage. The enzyme treatments were directly applied on the silage prior to mixing process. The total mixed rations contained 31% of faba bean silage, 14% of grass hay, 3.5% of straw, 30% of barley and corn grain and 21.5% of concentrate. There was no significant difference of applying FETR on nutrient intake (P > 0.05) except for CP intake, which was reduced in FETR group compared to control (P < 0.01, 4.4 vs 4.54 kg/d). There was a linear effect found in NDF digestibility when treated with FETR, where maximum improvement was achieved with 0.5 mL of FETR application. The milk fat yield, percentage of milk fat and fat-corrected milk were linearly affected by the increasing level of enzyme. The cows fed a diet supplemented with enzymes tended to have a lower milk fat. Feed efficiency linearly responded to incremental levels of FETR. There was no enzyme effect on feeding behavior and nitrogen balance and utilization. Results from this study indicated that supplementing fibrolytic enzyme on whole-plant faba bean silage diets for dairy cows improved lactational performance, intake and digestibility with 0.5 mL of FETR application. However, adding higher enzyme level resulted in negative effects on animal performance.     

Effects of soybean oil supplementation on performance,digestion and metabolism of early lactation dairy cows fed sugarcane-based diets

Sugarcane is an important forage source for dairy cows in tropical countries. However, it provides limited digestible fiber and energy intake, and fat supplementation can be a way to increase energy density and decrease dietary, non-fiber carbohydrates concentrations. We aimed to evaluate the performance, digestion and metabolism of dairy cows in early lactation fed different concentrations of soybean oil (SBO) in sugarcane-based diets. Fourteen primiparous (545±17.2 kg of BW) and eight multiparous (629±26.7 kg BW) Holstein dairy cows were used according to a randomized block design. After calving, diets were randomly assigned to cows within the two parity groups. Diets were formulated with increasing concentrations of SBO (g/kg dry matter (DM)): control (0), low (LSBO; 15.7), medium (MSBO; 44.3) and high (HSBO; 73.4). The study was performed from calving until 84 days in milk, divided into three periods of 28 days each. Dry matter intake (DMI) was affected quadratically in response to SBO addition with the greatest and lowest values of 19.0 and 16.0 kg/day for LSBO and HSBO diets, respectively. The digestibility of potentially digestible NDF was quadratically affected by SBO with the greatest value of 623 g/kg for LSBO diet. Both milk and energy-corrected milk (ECM) production were quadratically affected by SBO inclusion, with greatest ECM values of 27.9 and 27.3 for LSBO and MSBO, respectively. Soybean oil inclusion linearly decreased milk fat concentration by 13.2% from control to HSBO. The CLA t10,c12-18:2 was observed in milk fat only for MSBO and HSBO diets. Soybean oil inclusion did not affect plasma glucose or serum concentrations of total proteins, globulins, albumin, urea nitrogen, beta-hydroxybutyrate, non-esterified fatty acids or insulin. Serum concentrations of total cholesterol, triglycerides and low-density lipoprotein increased with SBO supplementation. Soybean oil inclusion in sugarcane-based diets for early lactation dairy cows from 15.7 to 44.3 g/kg DM can improve energy intake and performance; however, at 44.3 g/kg DM milk fat concentration and ECM decreased. Soybean oil inclusion at 73.4 g/kg DM adversely affected energy intake, fiber digestion and performance of early lactation dairy cows and is not recommended.