Land o lakes lamb milk replacer mixing instructions

DISCUSSION

Feeding a higher PON positively affected calf performance including final BW, ADG, and the feed-to-gain ratio. However, the improved ADG was more moderate than reported in other studies where a comparable MR was fed (Bartlett et al., 2006; Ballou, 2012). Studies using calves with FPT reported reduced ADG compared with calves with appropriate passive transfer (Pithua and Aly, 2013). Calves fed HPN had greater ADG in every period, with the exception of 50 to 68 d. At this time, calves were undergoing weaning. A probable contributor to the reduced ADG among HPN calves was likely due to the lower calf starter intake as well as digestibility of that calf starter at that time. Calves fed a HPN ate less starter throughout the study. Similarly, Huber et al. (1984) reported calves fed greater MR amounts consumed less calf starter. However, once weaned, previous studies observed that the HPN rapidly increase calf starter intake and can exceed LPN calves a few weeks after weaning (Ballou, 2012; Obeidat et al., 2013; Ballou et al., 2015).

In agreement with previous studies, HPN calves had greater fecal scores throughout the study (Nonnecke et al., 2003; Bascom et al., 2007; Liang et al., 2016). Greater fecal scores in calves fed a HPN are routinely considered a consequence of greater milk solids consumed. More importantly, the HPN calves had a greater incidence of scouring than LPN calves. Scours were considered if a calf had 2 consecutive fecal scores of 4. Previously, Ballou (2011) reported that anything greater than or equal to a fecal score of 3 was considered scours. However, Liang et al. (2016) reported the DM of feces from calves with a fecal score 3 and concluded it would be unlikely for most calves to become dehydrated with a fecal score of 3 or less. The moderate increase in fecal scores reported by others when feeding HPN would not increase the risk for dehydration. In contrast, when a calf has a fecal score of 4, the calf is at an increased risk to become dehydrated or develop metabolic acidosis. Scours can be infectious or noninfectious; however, the consequences are similar. A study completed by Quigley et al. (2006) reported findings that high-risk calves force fed a variable HPN program had greater incidence of scours and were treated with more antimicrobials than calves fed a restricted quantity of milk solids when raised on bedding contaminated with coronavirus. Force feeding high-risk calves has been reported to increase scours and is not a recommended nutrition strategy for sick calves and, therefore, was not included in this study design.

Liang et al. (2016) reported that healthy 1-wk-old calves fed either a low or high PON had no differences in the DE or ME efficiencies, concluding healthy neonatal calves are capable of digesting greater MR concentrations during the first week of life. In fact, healthy neonatal calves fed a high PON may be more capable of absorbing and utilizing those additional nutrients than calves fed a low PON. Further, Liang et al. (2016) reported increased digestible CP and nitrogen retention as a percentage of intake when fed the high PON. They concluded that healthy calves are able to digest and use the extra nutrients very efficiently during the first week of life; however, they constrained the inferences to healthy calves.

Healthy calves may be more capable of absorbing nutrients than high-risk calves; therefore, a HPN may not be as advantageous among high-risk calves as it is in healthier low-risk calves. Calves failing to receive colostrum were reported to have reduced gastrointestinal integrity, as reflected in decreased mucosal thickness, as well as decreased villus length and width compared with calves that received colostrum (Yang et al., 2015). Further, increased colostrum intake improved intestinal epithelial cell proliferation and maturation as well as enzymatic activity (Blättler et al., 2001). Colostrum not only influences gut integrity but also contains immune components and nutrients that are considered a major factor in preweaning health. Failure of passive transfer is associated with poorer preweaning performance and health (Naylor et al., 1977; Donovan et al., 1998; Pithua and Aly, 2013). These high-risk calves receiving the HPN may have had reduced gut integrity and local immune protection and, as a result, were less tolerant to the additional milk solids, which increased the risk for scours.

Calves fed the HPN also had a tendency for increased incidence of abomasal bloat. Although the incidence of bloat is often sporadic and the etiology not completely understood, a reduced abomasal emptying rate and increased fermentable substrates in the abomasum are risk factors (Burgstaller et al., 2017). Increasing the solids content or osmolality of MR fed can delay abomasal emptying, and feeding a high PON also may increase the nutrients available for rapid fermentation by Clostridium perfringens, a microorganism often suspected in abomasal bloat. More research is needed to understand how PON influences abomasal dynamics and health.

The expression of nonnutritive oral behaviors early in life may be important to establish mature feeding behaviors and reduce the incidences of unwanted behaviors (e.g., cross sucking) after calves are weaned and transitioned from individual housing to group housing (Veissier et al., 2002; Horvath and Miller-Cushon, 2017). Before weaning, PON did not influence dummy-nipple use, except at 15 d, when LPN calves tended to use the nipple more than HPN calves. The day before this (14 d), daily standing duration was increased among all calves, which was likely caused by research personnel spending most of the day setting up video recording equipment. Nonetheless, after weaning was completed, the HPN calves increased dummy-nipple use to over 3 times their preweaning frequencies until 64 d of age. This is an indicator that the stress of weaning was likely greater among HPN calves. The HPN calves had MR as the main component of that diet, and the HPN calves were only motivated to use the dummy nipple when that source of satiety was removed. The HPN calves returned to their preweaning dummy-nipple use by 64 d, and by this age the calves may have been consuming enough starter to become satiated. This is in contrast to data reported by Bortoluzzi (2019), where step-down weaning calves fed a HPN at 50 d did not increase their use of the dummy nipple, whereas HPN calves either step-down weaned at 39 d or gradually weaned by decreasing the quantity of milk offered from 43 to 57 d had relatively greater use of the dummy nipple. The authors concluded it may have been less stressful to wean those calves from HPN at the older age, 50 d in that study, because they were consuming more starter. Even though the calves in the present study were weaned at approximately the same age and in the same manner as the calves in the study by Bortoluzzi (2019), the high-risk nature of the calves resulted in reduced calf starter intake and, therefore, required either a later or possibly an even more gradual weaning.

Benefits of feeding programs that increase preweaning ADG are established. Improvements in calf performance were reported in stressed calves fed 3 times per day versus 2 times a day (Schingoethe et al., 1986). Starter intake was improved with increased feeding frequency (Kmicikewycz et al., 2010). Further, it is possible the issues observed with HPN in high-risk calves could be reduced with increased feeding frequencies and should be considered in future research. No difference in either serum glucose or urea nitrogen was observed between treatments. Similarly, Obeidat et al. (2013) and Smith et al. (2002) reported no difference in these metabolites in calves fed varying levels of MR. Conversely, calves fed greater levels of MR had greater plasma glucose concentrations in previous studies (Smith et al., 2002; Quigley et al., 2006; Ballou et al., 2015). Others have reported lower urea nitrogen concentrations in calves fed greater MR levels (Ballou et al., 2015). Calves in the present study did not appear to have any differences in protein or glucose metabolism.

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