Effects of Feeding Levels of Starter on Weaning Age, Performance, Nutrient Digestibility and Health Parameters in Holstein Dairy Calves

Calves could be weaned after they consume a specific amount of starter in a specific period of time, mostly 2 to 3 d continuously (Morrill et al., 1995; Abdelgadir et al., 1996). Coverdale et al. (2004) started their weaning when all calves were consuming 450 g of starter on d 52 of the trial. Franklin et al. (2003) started the weaning process when calves had consumed 680 g of starter/d for 2 d, consecutively. Appleman and Owen (1975) reported that the predetermined dry feed intake (DFI) used to set up the weaning of dairy calves ranged from 454 to 908 g/d. Leaver and Yarrow (1972) weaned calves at three different dry feed intake ranges (DFIR). Those researchers inferred that a DFIR of 400 g/d for 3 consecutive d was adequate for calves and decreased days to weaning compared to a DFIR of 650 and 900 g/d for 3 consecutive d.

Time of weaning is a critical point in dairy calf breeding. Weaning at different times can affect performance and health parameters directly. Greenwood et al. (1997) reported that calves in the 1% treatment group (dry feed intake as a percentage of birth weight as a weaning criterion) met the weaning criterion earlier than did those in the 1.5% and 2% treatment groups. Limited consumption of milk is very useful for calf rearing management and decreases weaning age as it encourages calves to consume more starter before weaning (Davis and Drackley, 1998). Any decrease in weaning age could improve calves’ health, lessen diarrhea and consequently improves performance. Therefore, the aim of this study was to determine the effect of feeding levels of starter on weaning age, performance, digestibility and health parameters in dairy calves receiving ad libitum starter.

Twenty eight male Holstein dairy calves born between Feb and Apr 2010 were allocated to four treatments from birth to d 56. Treatments included: weaning after consuming starter at 350, 500, 650, and 800 g/d for 3 d consecutively. Calves were weighed and assigned to treatments after 3 d of birth and the ration used in this trial was according to NRC requirements for dairy animals (2001). Milk was provided in 2 equal feedings at 8% of birth weight per day prior to weaning and/or the first 3 d, calves received the same percent of colostrum as well. Calves were housed in individual hutches (1.5?2.5 m individual pens) bedded with straw. Water was offered ad libitum after 3 d when calves were assigned to the treatments. Starter was formulated to be iso-nitrogenous at 19.5% CP and 90.5% DM in the form of pellets. The ingredients and composition of the starter are provided in Table 1.

Starter intake was monitored daily, and body weights were obtained at the time of weaning and at d 56. Amounts of starter and milk consumption offered and refused were recorded daily. Fecal scores were subjectively scored once daily using a scale of 1 = normal feces, 2 = soft to loose, 3 = loose to watery, 4 = watery, mucous, slightly bloody, and 5 = watery, mucous, bloody. Respiratory scoring was done once daily using a scale of 1 = normal, 2 = slight cough, 3 = moderate cough, 4 = moderate to severe cough, and 5 = severe and chronic cough. Also, fecal odor scoring was measured on the scale: 1 = normal, 2 = slightly offensive and 3 = highly offensive. Body temperature (using rectal thermometer) was recorded every week (Larson et al., 1977). All calves were monitored every day for the time of starting rumination. Feed and fecal samples were collected for 5 d after weaning (wk 8) for evaluating nutrient digestibility (AOAC, 1990). Feed residues were collected and weighed every day at 8 AM in the morning for each calf separately for 5 d. All feces were collected and weighed at 8:30 AM for each calf separately from individual hutches during these 5 d at the end of the experiment. Then all feed and feces for each calf were mixed together, a sample taken and stored (-20?C) for further analysis.

Data was analyzed using the linear model (PROC GLM) of SAS (1996). Differences were observed at p<0.05 and Duncan comparisons used for means evaluations. Data in the tables collected at weaning and the final data reported at d 56 (wk 8). Initial body weight as a covariate was included in the model when appropriate but was removed from the model when not significant.

Body weights (BW) were recorded at the beginning, weaning time and the end of trial for all calves. In the pre weaning period, the differences of BW between treatments were significant (p<0.05). The higher body weight found in calves receiving 600 and 800 g/d of starter compared with calves receiving 350 g/d of starter might be explained by the higher dry matter intake (DMI) in these two treatments (Table 3). Difference in BW between calves receiving 350 and 500 g/d of starter was not significant (Table 2). Therefore, DMI in these two treatments was not different (p>0.05). This result is in agreement with the studies of Coverdale et al. (2004), Franklin et al. (2003), and Greenwood et al. (1997) who reported no significant difference in BW until wk 5. However, reduced BW gain after weaning has been reported by some researchers (Huber et al., 1984; Anderson et al., 1987; Luchini et al., 1991). Starter intake and growth rate in the post-weaning period were 5.8 kg and 0.45 kg/d, 4.1 kg and 0.65 kg/d, 4.2 kg and 0.77 kg/d, 3.4 kg and 0.75 kg/d for calves in 350 g/d, 500 g/d, 650 g/d, and 800 g/d groups, respectively. No differences were observed in BW at the end of trial between calves receiving 500, 650 and 850 g/d of starter and in FCR for all treatments as well. Only BW in calves fed 350 g/d of starter at the end of the trail was the lower and was related to their lower BW at weaning age. A poorer feed conversion ratio (p<0.05) in calves receiving 350 g/d of starter might be explained by a low DMI (Table 3) and a poorer health condition (Table 5). Coverdale et al. (2004) found no difference in body weight gain, average daily gain, and feed efficiency, in calves fed with ground starter compared to those fed a commercial coarse starter prior to weaning (consuming 450 g/d of starter). Average daily gains of male calves from birth to 30 d, 30 to 60 d, and 60 to 90 d were 0.38?0.03, 0.93?0.03 and 1.01?0.04, respectively (Arrayet et al., 2002).

DMI at weaning age in calves receiving 350 g/d of starter differed (p<0.05) in comparison with calves receiving 600 and 800 g/d of starter, but no difference (p>0.05) was observed in DMI between calves receiving 350 and 500 g/d of starter (Table 3). This may be due to the time taken to achieve weaning age in calves receiving 350 and 500 g/d of starter. But, it is clear that weaning age in calves receiving 350 g/d of starter was the youngest among all treatments (p<0.05). Calves that weaned earlier had less time to consume starter and milk before weaning compared with the others. Lower DMI and BW in calves receiving 350 g/d of starter also might be explained by lower dry matter, organic matter and crude protein digestibility in this treatment (Table 4). Consequently, more nutrients were available to calves receiving 500 or more g/d of starter (500, 650, and 800 g/d). Hence, these calves gained more BW than calves receiving 350 g/d of starter. Greenwood et al. (1997) reported the same result in regards to reducing weaning age by decreasing starter intake to 1% of initial body weight. Franklin et al. (2003) reported calves fed textured starter consumed more total grain, were weaned earlier, and weighed more at 6 wk of age than calves fed pelleted starter. Coverdale et al. (2004) found no difference in weaning age with respect to their treatments. Milk consumption (kg, DM) was lower in calves receiving 350 g/kg of starter than other treatments (p<0.05). Lower milk consumption in calves receiving 350 g/kg of starter might be explained by lower weaning age compare to other treatments (Table 3). No significant difference was observed between calves receiving 350 and 500 g/d of starter in milk consumption (p>0.05). No differences were observed in the time of starting rumination (p>0.05).

Dry matter (DM), organic matter, (OM), crude protein (CP), acid detergent fiber (ADF) and neutral detergent fiber (NDF) digestibility are shown in Table 4. DM, OM and CP digestibility in calves that received 350 g/d of starter was lower than the other treatments (p<0.05) but no differences were observed between calves receiving 500, 650, and 800 g/d of starter (p>0.05). Lower DM, OM and CP digestibility of starter could be due to the younger weaning age resulting in a lower level of starter intake in calves fed 350 g/d of starter. The calves’ rumens were not sufficiently developed when weaned as early as 25 d of age. No differences (p>0.05) were observed in ADF and NDF digestibility among all treatments (p>0.05).

Feces, respiration, and fecal odor were scored as health parameters. Body temperature, days of drug administration for diarrhea and pneumonia were also noted to determine if treatments had an effect on calves’ health (Table 5). Coverdale et al. (2004) reported that daily scores, electrolyte and antibiotic administration did not differ by treatments (p>0.05). The greatest incidence of fecal scores more than 2 occurred during wk 2 and 3 which is consistent with previous reports (Quigley et al., 1995; Franklin et al., 2003). Days of drug administration for diarrhea in calves receiving 350 g/d of starter was greater (p<0.05) than the other treatments. It can be illustrated by the earlier weaning age at 350 g/d and decreasing starter intake after weaning. Regarding to diarrhea, the fecal odor score of calves fed 350 g/d of starter increased and continued for 3 d even after drug administration. Following diarrhea, calves manure tended to be watery with mucus and their body temperature tended to decrease. There were no differences (p>0.05) between treatments in days of drug administration for pneumonia (Table 5).

We conclude that when calves are weaned only after consuming 500 g/d or more of starter their performance, nutrient digestibility and general health conditions are improved and their weaning age decreased. Therefore, the best time for weaning is when calves are consuming starter at 500 g/d (more than 1 percent of initial body weight) for 3 d consecutively.

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