Supplementary feeding is a widespread practice in South African livestock farming. Dr Liesel Foster conducted a study on the effect of three lick supplementation levels on the production and profitability of an extensive beef herd run on mixed veld in the Zastron district for her PhD thesis.
The vegetation in the study area is typical of transitional Cymbopogon-Themeda veld and had a grazing capacity of 5ha/ LSU to 7ha/LSU. The study herd of 150 Drakensberger cows was divided into three treatment groups (T1, T2 and T3).
A three-phase supplementation programme was divided into three supplementation periods – summer, early winter and late winter.
The last two included roughly the same nutrients, while the early winter supplementation period featured 20% less lick. The supplement was a commercial pre-mix, supplied ad lib and replenished twice a week, and never exceeding the maximum recommended daily intake.
All three groups received a protein and mineral supplement in winter and late winter. The nutrient composition of each group differed due to different raw material inclusion rates (see Tables 1 and 2).
The groups rotated between camps every fortnight. The cows were mated from mid-December to the end of March, and calves weaned according to age from April to June. Single-bull mating applied throughout, with bulls rotated between groups every two weeks.
Parameters measured were supplement intake (g/ cow/day) and cost (Rand/cow/year); cow weight (in August, March, at weaning, and in July); body condition score (BCS, Scale 1 to 9); calf birthweight; calf 100-day weight; calf weaning weight; intercalving period (days); and conception rate (%).
Table 3 shows the three-year average supplement and nutrient intakes, as well as average cost (prices 2011 to 2014) of the supplement treatments.
The late winter supplementary crude protein (CP) intake of all three treatment groups (234g, 230g and 229g/ animal/ day) was similar. Differences in composition of the supplements, as well as the supplementary protein from non-protein-nitrogen (NPN), showed in differences in supplementary energy in the three treatment groups.
During summer supplementation, the T1 group consumed 299g/ cow/ day, well above the maximum recommended intake of 240g/ cow/day (Table 3). The T2 and T3 groups consumed close to the minimum recommended daily intake of 100g/animal/day. This increased phosphate (P) intake in the T1 group (11,45g/ cow/ day) when compared to the T2 and T3 groups (6,06g/cow/day and 6,24g/ cow/day respectively).
The average winter supplement intake of the T1 group (514g/ cow/ day) was close to the maximum recommended level of 520g/cow/ day. The T2 group consumed 428g/ cow/ day, slightly more than the maximum recommended intake of 400g/cow/day. The T3 treatment group consumed 347g/cow/day, slightly below the maximum recommended intake of 400g/cow/day. Table 4 indicates the mean body weights of the supplementation treatment groups.
In Year 2 (2012 to 2013), T3 group cows weighed 563kg ± 53kg when weaning their calves, more than the cows in the T2 group (540kg ± 58kg). There was no significant difference in the body weight of the groups during Year 3 (2013 to 2014) of the study.
The T3 group gained significantly more weight between August and March in Year 1 and Year 3, with a higher body condition score (BCS) at the end of the breeding season (March) in Year 1 and Year 3 (Tables 4 and 5).
The T1 group gained less weight between August and March in Year 1 and Year 3, with a lower BCS at the end of the breeding season (March). In Year 2, the T1 group gained more weight (48 ± 42kg) between August and March, and T2 the least weight (29 ± 28kg).
Although the T2 group gained the least weight, it had a significantly higher BCS (5,05 ± 0,49) at the end of the breeding season (March).
Table 5 indicates the mean (± SD) BCS (1 = severely emaciated and 9 = very obese) of the supplementation treatment groups, while Table 6 summarises the production and reproduction levels of the three groups.
Conception rate and weaning Weight
Although there was no statistical differences in weaning weights between supplementation treatments, the T1 calves tended to be the heaviest (223kg ± 26kg, 218kg ± 24kg, 230kg ± 26kg) at weaning and the T3 calves the lightest (214kg ± 23kg, 210kg ± 27kg, 223 ± 16kg) in the three years respectively. Conception rates of 90%, 91% and 92% were recorded for T1, 91%, 88% and 92% for T2, and 92%, 94% and 96% for T3.
While 100-day calf weights differed significantly between treatment groups in 2012 to 2013 and likewise the birthweights of the calves in the 2013 to 2014 group, these variables were not used as production parameters.
The three-year average intercalving period (ICP) for the T1 group was 387 days, the T2 group 378 days, and the T3 group 387 days.
The study found no significant relationship between body weight and conception rate, or between body condition score and conception rate, possibly due to the ‘target weight’ concept that many animal scientists propose.
Each cow has the probability to conceive within a specific range of body weight and body condition.
The supplementation level of all three groups probably enabled the cows in each group to operate within their ‘target weight’ range.
Due to the high intake and cost of the ready-mixed mineral supplement that the T1 group received in summer, compared with the mineral supplement received by the T2 and T3 groups, as well as the higher recommended intake (the CP content due to a higher cotton oil cake inclusion rate) of the winter and late winter supplements received by the T1 group, the T1 group would have to considerably outperform the T2 and T3 groups to cover the additional expense.
This was not found in this trial, as the supplementation treatment did not significantly affect the conception rate and ICP. Despite the fact that T1 group cows weaned slightly heavier calves, the difference was not sufficient to make this practice economically justifiable (Table 7).
Conclusion: a word of caution
On well-managed veld in the south-eastern Free Sate, supplementing beef cows with a mineral (60g P/ kg) lick in the wet season (summer) and a protein and mineral supplement in which most protein (96%) is derived from NPN (in this case urea) in winter, achieves the highest economic return.
Foster supports sustainable veld management and does not advocate using supplements as used in this study, as the results cannot be replicated under all conditions.
Phone Dr Liesel Foster on 082 373 2427.