Browsing by Author "Jordaan, Marisa"
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- ItemThe effect of milk replacer intake and level of crude protein in starter feed on dairy bull calf pre-weaning growth parameters and the carry-over effect on post-weaning growth and profitability(Stellenbosch : Stellenbosch University, 2022-12) Jordaan, Marisa; Van Zyl, Johan Hendrik Combrink ; Kriel, G. V.; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Sciences.ENGLISH ABSTRACT: Currently worldwide, during the liquid phase, calves are generally fed conventional volumes (4 L/day) of milk replacer (MR) with ad libitum starter feed ranging between 160 g CP/kg DM and 210 g CP/kg DM. Dairy bull calves are unwanted in the dairy industry, therefore they are normally sold to feedlots where they are raised as veal or dairy beef. Calves can however consume higher volumes of MR than the conventional volume which can result in greater weight gains. A positive correlation between dietary crude protein (CP) intake and protein deposition in body tissue is also known. Thus, feeding calves higher volumes of MR combined with high CP starter can potentially increase dairy bull calves more profitable. In practice improved feed efficiency of calves leads to higher profitability. A two part study was therefore conducted with the first phase evolving a pre-weaning MR and CP starter feed phase and a secondary part investigating the effect of pre-weaning treatments on the post-weaning backgrounding phase performance. In the first part of the study, three different volumes of MR (4, 6 & 9 L/day) and two different CP starter feeds (210 g/kg DM & 260 g/kg DM) were fed to Holstein-Friesian bull calves to evaluate pre-weaning growth parameters. The treatments were (1) 4 L/day of MR, 210 g CP/kg DM starter feed (LL); (2) 6 L/day of MR, 210 g CP/kg DM starter feed (LM); (3) 9 L/day of MR, 210 g CP/kg DM starter feed (LH); (4) 4 L/day of MR, 260 g CP/kg DM starter feed (HL); (5) 6 L/day of MR, 260 g CP/kg DM starter feed (HM) and (6) 9 L/day of MR, 260 g CP/kg DM starter feed (HH). All calves were weaned after 60 days of age. The MR volume of calves fed the 6 and 9 L/day were stepped down from day 46 to increase the DMI of the starter feed before weaning. Weekly body weights and allometric growth measurements were taken to evaluate body weight growth and allometric growth differences between treatments. Starter feed dry matter intake of the calves fed 4 and 6 L/day of MR were significant greater (P < 0.05) than for calves fed 9 L/day. No differences in ADG, growth parameters and gain over the period were observed between MR volume treatments. Average daily gain and gain over period however were significantly different (P < 0.05) between the two CP starter feeds. The final weight of the calves did not differ between the starter feeds, but the final weight of calves fed 6 L/day of MR were significantly (P < 0.05) higher than from the calves fed 4 L/day MR while the 9 L/day MR group final weight did not differ from any of the other treatments. None of the allometric growth parameters differed between treatments. The feed conversion ratio of the calves did not differ significantly among all six treatments. During the post-weaning phase of the study, all calves were background for 80 days on ad libitum grazing while daily supplemented with the same concentrate feed at 2 kg per calf per day. The objective of the secondary phase was to evaluate the carry-over effects on the post-weaning growth and profitability of Holstein-Friesian steers. After 80 days of backgrounding, the calves were sold to a commercial feedlot. Based on this income, the related profitability per animal per treatment were calculated. No carry-over effects were observed for calves fed higher volumes of MR nor higher CP starter feed during the pre- weaning phase, since the gain over period during the post-weaning phase were not different amongst the treatment groups, except for treatment LL which did not differ significantly from treatments HM and HH. Treatment LL resulted in numerical slower growth both during the pre- weaning and post-weaning period. The latter treatment differed significantly (P < 0.05) from treatments LM, HL, HM and HH during the pre-weaning period, however only differed significantly (P < 0.05) from treatments LM, LH and HL during the post-weaning period. The total cost of raising the calves differed significantly (P < 0.05) for all treatments and this difference was mostly the result of the feed cost during the pre-weaning phase. Treatment HL was numerically, the most cost effective with the highest profit, while calves fed 9 L of MR resulted in the lowest profit. However, the profit of treatment LL and HH were significantly lower (P < 0.05) than treatment HL but did not differ significantly from the other treatments. The lack of response in treatment LL during the pre-weaning period could be attributed to nutritional insult, therefore the lack of response was carried over in the post-weaning period. Feed costs vary from season to season, therefore the total cost of raising can vary over season and between geographical locations. In this trial, however feeding calves the conventional volume of MR with a high CP starter resulted in the most profitable approach to raising dairy beef.