Gradual weaning does not improve performance for calves with low starter intake at the beginning of the weaning process.

The weaning process may cause intense stress for dairy calves, even when low volumes of liquid diet are fed. Management tools that increase the intake of solid feeds, such as gradual weaning, can provide better physiological and metabolic conditions through better ruminal development, leading to better adaptation to ruminant metabolism and aiding in stress mitigation. The objective of this study was to evaluate the effects of 2 weaning protocols and 2 levels of concentrate intake on the performance and physiological and behavioral variables related to stress in dairy calves. Thirty-six newborn male Holstein calves were used in a randomized block design with a 2 × 2 factorial arrangement: 2 weaning strategies, abrupt or gradual, and 2 levels of concentrate intake at 5 wk of age, high (>350 g/d) or low (≤350 g/d). Calves were equally managed until they were 5 wk of age and then grouped according to concentrate intake. Statistical analyzes were performed using the MIXED procedure of SAS software (SAS Institute Inc., Cary, NC), and no significant interaction was observed between studied factors (weaning method and starter intake level); therefore, we considered each factor separately and their interactions with age. The highest dry matter intake and concentration of ß-hydroxybutyrate were recorded for animals with a high level of starter intake independent of the weaning method. Structural growth (cm/wk) and average daily gain were superior for calves with high starter intake, but weaning method had no effect. The gradual weaning protocol increased the time eating starter, regardless of the level of concentrate intake. Even animals with low concentrate intake that were weaned abruptly showed levels of cortisol and acid-soluble glycoprotein within normal physiological levels. Apparently, other factors besides the milk supply affect the starter intake level of calves in a conventional feeding program. The adoption of gradual weaning is not effective in improving performance when a calf has low intake 3 wk before weaning is complete, but it reduced vocalization on d 2 postweaning.

Intensive liquid feeding of dairy calves with a medium crude protein milk replacer: Effects on performance, rumen, and blood parameters.

The objective of this study was to evaluate the effects of different liquid-feeding systems using a medium crude protein milk replacer on performance, rumen, and blood parameters. Thirty newborn Holstein calves were blocked according to birth weight and date of birth, and randomly distributed to different liquid-feeding systems: conventional (4 L/d), intensive (8 L/d), or step-up/step-down (wk 1, 4 L/d; wk 2 to 6, 8 L/d; wk 7 and 8, 4 L/d). The commercial milk replacer (12.5% solids, 20.2% crude protein, 15.6% fat) was fed twice daily (0700 and 1700 h) until calves were weaned, at 8 wk of age. Calves were individually housed in wood hutches, with free access to water and starter concentrate, and to hay only after weaning. They were followed through 10 wk of age. Milk replacer and starter intake were inversely affected by feeding system. After weaning, starter intake and hay intake were similar among feeding systems. Total dry matter intake was higher during the liquid-feeding period for calves on the intensive system compared to calves on the conventional system, but conventional feeding resulted in the highest dry matter intake after weaning. Feed efficiency was similar among feeding systems before and after weaning. Average body weight and daily gain were not affected by feeding system before or after weaning. During liquid feeding, diarrhea occurrence was lower for calves on the conventional system; however, when calves on the step-up/step-down system were fed lower volumes of liquid feed, diarrhea occurrence was similar to that of calves on the conventional system. Plasma concentrations of ß-hydroxybutyrate were higher for calves on the conventional system, reflecting starter intake. Rumen pH, short-chain fatty acids, and N-NH3 were not affected by feeding system. Feeding higher volumes of milk replacer with a medium crude protein content had no beneficial effect on the performance of calves up to 10 wk of age.

Performance and Metabolism of Calves Fed Starter Feed Containing Sugarcane Molasses or Glucose Syrup as a Replacement for Corn.

The aim of this study was to evaluate the effect of replacing corn grain for sugar cane molasses (MO) or glucose syrup (GS) in the starter concentrate on performance and metabolism of dairy calves. Thirty-six individually housed Holstein male calves were blocked according to weight and date of birth and assigned to one of the starter feed treatments, during an 8 week study: i) starter containing 65% corn with no MO or GS (0MO); ii) starter containing 60% corn and 5% MO (5MO); iii) starter containing 55% corn and 10% MO (10MO); and iv) starter containing 60% corn and 5% GS (5GS). Animals received 4 L of milk replacer daily (20 crude protein, 16 ether extract, 12.5% solids), divided in two meals (0700 and 1700 h). Starter and water were provided ad libitum. Starter intake and fecal score were monitored daily until animals were eight weeks old. Body weight and measurements (withers height, hip width and heart girth) were measured weekly before the morning feeding. From the second week of age, blood samples were collected weekly, 2 h after the morning feeding, for glucose, ß-hydroxybutyrate and lactate determination. Ruminal fluid was collected at 4, 6, and 8 weeks of age using an oro-ruminal probe and a suction pump for determination of pH and short-chain fatty acids (SCFA). At the end of the eighth week, animals were harvested to evaluate development of the proximal digestive tract. The composition of the starter did not affect (p>0.05) concentrate intake, weight gain, fecal score, blood parameters, and rumen development. However, treatment 5MO showed higher (p<0.05) total concentration of SCFAs, acetate and propionate than 0MO, and these treatments did not differ from 10MO and 5GS (p>0.05). Thus, it can be concluded that the replacement of corn by 5% or 10% sugar cane molasses or 5% GS on starter concentrate did not impact performance, however it has some positive effects on rumen fermentation which may be beneficial for calves with a developing rumen.

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

UNLABELLED: 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 10th 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 2nd 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 ß-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.