Correlations between maternal performance and colostrum quality; thus, impacts on offspring performance.
By Garland Dahlke, Devin Jakub and Erika Lundy
Swings in weather patterns, of which have inconsistently altered feed availability to cow-calf producers, and a demand for increased calf performance have unfolded a need to further investigate the negative impacts of inefficient beef cow nutrition. Extensive research in the dairy industry and even in other species such as sheep has shown correlations between maternal performance and colostrum quality, and thus, impacts on offspring performance.
Though beef cows are efficient in utilizing protein and energy, their nutrient requirements are often compromised in late gestation and lactation due to events in which the producers have poorer quality feeds at their disposal. Such instances may have negative effects on colostrum quality as the cow allocates nutrients towards fetal development and eventually lactation.
This plays a crucial role in the initial development and passive immunity of the calf because there is no fetal-placental transfer of antibodies in utero; thus, the calf must acquire those antibodies through colostrum. In addition to immunoglobulins, colostrum also delivers essential vitamins, proteins and fat to the calf.
There is little known permeability of fat-soluble vitamins across the placenta, meaning the calf must acquire important vitamins like A and E through colostrum as well. The calf is able to absorb intact proteins for approximately 24 hours after birth before intestinal closure; thus, quality and quantity of colostrum is key to survival and growth of the neonatal calf.
Materials and methods To investigate the effects of nutrient restriction on cow and subsequent calf performance, multiparous Angus cows (n=48) were blocked by body weight and randomly assigned to one of four treatments. All fall cows were given one A.I. opportunity before being exposed to cleanup bulls for 90 days. No fetal aging was utilized for this study.
Cows were grouped into four groups within each treatment, for a total of 16 groups. Average empty cow weights per pen ranged from 1,040 to over 1,400 pounds.
Treatments consisted of ground hay (HAY), ground hay and whole-shell corn (HC), ground hay and dry distillers grains (HD) or ground hay with dry distillers and whole-shell corn (HCD).
Table 2 includes percentages of metabolizable protein and net energy for each treatment.
Cows were fed at constant levels throughout the trial with the expectation that their caloric intake may not be adequately met from approximately month-8 of gestation (day 0 of trial) until the time they calved. Nutrient analyses of feedstuffs along with manure samples were collected biweekly during the study.
At the end the analysis of these feedstuffs including total tract NDF digestibility along with starch digestibility was performed to calculate the available caloric and metabolizable protein content of the feed. Upon calving, all pairs were returned to normal herd management which involved grazing tall fescue pastures at the McNay Research and Demonstration Farm.
Table 1 outlines the timeline of measurements taken for both the cows and their calves. Twelfth rib backfat (BF) and ribeye area (REA) were measured via ultrasonography at day 0 of the trial and then at day 49 (just prior to calving).
Body condition score (BCS) was calculated as: [(BF/REA*100) + 2.5]. Empty body weight (EBW) was calculated using the following equation: (EBW = shrunk weight x 0.96). The weight of the fetal calf plus fluids was also accounted for using the following equation: [Wt of cow x (.01828 x 2.7/\(.02 x dp-.00000143 x DP x DP)] (DP represents days pregnant).
At calving, a composite colostrum sample of 100mL was collected from the left front and rear quarters of the cow within 24hr of parturition and frozen at the time of collection.
Samples were later analyzed for IgG, milk urea nitrogen (MUN) and total protein (TP) concentrations at the Cornell university Diagnostic laboratory.
Performance variables were analyzed using repeated measures for least square means. These procedures were carried out using the MIXED procedure in SAS 9.4 (SAS Inst. Inc., NC, USA).
Results and discussion As expected, there were no significant differences observed at day zero or day 49 for live and empty body weight, despite a decrease in body weight over all treatments. Table 3 displays cow performance values on and off test, and at calving. HCD cows had the greatest increase in final visual BCS (P = 0.03), but because all cows showed a decrease in body weight, calculated BCS was included to eliminate potential bias of visual BCS.
All cows had less final calculated BCS, with no significance observed between treatments. For BF, all treatment groups exhibited a decrease from initial to final, but no significant differences were observed between groups. HAY, HD, and HCD cows had a decrease in REA from initial to final, with HC cows staying the same; however, no significant differences were observed between groups.
Cow colostrum composition relative to treatment was also analyzed for this study. No significant differences were observed for IgG and total protein concentrations between all treatment groups (Table 4).
For HD cows, MUN concentrations were significantly higher than the other treatment groups (P=0.02). Correlations of cow colostrum content to growth performance are displayed in Table 5.
IgG and TP tended to be positively correlated, while IgG and MUN tended to be negatively correlated (P≤ 0.10). MUN and initial backfat (IBF) tended to be negatively correlated (P ≤ 0.10), while significance for a negative correlation (P ≤ 0.05) was observed for MUN and final backfat (FBF). Significance was observed for a negative correlation (P ≤ 0.05) between TP and final ribeye area (FREA).
Measurements of calf performance relative to maternal treatment were also recorded for this study (Table 6). Though there were slight variations in birth weight and calf vigor scores across all treatments, no significant differences were observed between groups. Similarly, there were no significant differences observed across all treatments in BW at 18 weeks and at weaning. Overall, it was observed that restricting cows of energy during late gestation could potentially lead to a decrease in cow performance.
HC was the only treatment that met energy requirements and had the least decline in BW, BF, REA, and BCS.
All other treatment groups exhibited moderate decreases in BW, BCS, BF, and REA; suggesting a potential negative energy balance in which cows were mobilizing more fatty acids from adipose tissue to compensate for an energy deficit.
A high value of MUN in the HD treatment group was expected because of a large oversupply of metabolizable protein (MP) in that diet. Thus, the negative correlations between MUN and IBF and FBF could point toward a higher energy demand by the cows that were oversupplied protein to excrete that extra protein via the milk and urine.
Consequently, at a certain point, oversupplying protein can be counter- productive as the cow mobilizes more fat to meet the energy demands of excreting excess protein from the urea cycle.
Another takeaway from this study is the importance of BCS. Accounting for fetal weight and fluid can be difficult when visually assigning BCS, as is evidenced by the data.
Thus, measuring BF and REA can be an important tool in determining the actual BCS of a cow, while keeping BW in mind. Looking forward, what this third trimester nutrition means in terms of cow productivity is summarized in Table 7. This table provides information on the subsequent breed-back or the next year’s productivity.
Note that the more energy deficient ration (HAY) resulted in the greatest weight loss but not significantly poorer breed back from the HCD and HD treatments.
The HC ration, which based on cow measurements did not seem to differ much from the others in results, but appeared to have the best balance from feed analysis and calculated requirements performed considerably better at this point with no cows in this group coming back open and the days already bred being a month ahead of the other treatment groups.
In summary, restricting cows of energy during late gestation can negatively effect cow performance, as evidenced by colostrum content, but it is both a function of the extent of the restriction and the type of diet being fed.
Further research is needed as to how maternal nutrition during late gestation may affect passive immunity in calves, and hence, calf performance.
