Supplementing Trace Minerals to Pregnant Beef Cows

Our research group compared the effects of organic and inorganic copper, manganese, zinc and cobalt supplementation to late-gestating beef cows on productive responses of the offspring. This area of research – nutritional interventions to promote fetal programing in beef cattle – has been a topic of interest to our and many other research groups.

After evaluating the existing literature, we assessed that little was known about the impacts of maternal trace mineral status on offspring productivity, including elements essential for fetal development such as copper, manganese, zinc and cobalt.

Pregnant Angus-influenced cows were assigned to a forage-based diet containing: 1) sulfate sources of copper, manganese, zinc and cobalt – INR, 2) organic complexed source of copper, manganese, zinc and cobalt – AAC, (Availa®4; Zinpro Corporation, Eden Prairie, MN), and 3) no copper, manganese, zinc and cobalt supplementation – CON. The INR and AAC diets were formulated to provide the same daily amount of copper, cobalt, manganese and zinc based on 7 gallons/cow daily of Availa®4.

After calving, cow-calf pairs were managed as a single group with inorganic trace mineral supplementation. Calves were weaned at 7 months of age and preconditioned on pasture as a single group for 45 days, with free-choice access to an inorganic mineral supplement. After preconditioning, calves were transferred to a commercial feedlot where they were managed as a single group until slaughter.

Results

Prior to calving, liver concentrations of cobalt, copper and zinc were increased in INR and AAC compared with CON cows, whereas INR had reduced liver cobalt, but greater liver copper compared with AAC cows (Table 1), suggesting that both INR and AAC diets successfully increased liver content of cobalt, copper and zinc.

After calving, we also collected liver samples from the newborn calf, as well as samples from the placenta for trace mineral analysis (Table 1). In cotyledons – calf portion of the “placental buttons” – cobalt concentrations were greater in AAC and INR compared with CON cows, and copper concentrations were only increased in AAC compared with CON cows.

Calves from INR and AAC cows had greater liver cobalt concentrations compared with calves from CON cows, but liver copper and zinc concentrations were only increased in calves from AAC cows compared with cohorts from CON cows.

Hence, supplementing inorganic and organic cobalt, copper, manganese and zinc sources to beef cows during late gestation increased the concentration of cobalt in the placenta and newborn calf liver, indicating increased passage of this trace mineral through the placenta to the fetus.

Similar outcomes were detected for calf liver copper and zinc only when comparing AAC and CON cows, suggesting enhanced transfer of these elements from maternal to fetal tissues when the organic source was offered.

Weaning body weight – actual or 205-day adjusted – were greater for calves from AAC cows compared with calves from CON cows, and similar between calves from INR cows compared with the other treatments (Table 2).

Hence, supplementing pregnant beef cows during late gestation with cobalt, copper, zinc and manganese increased weaned calf weight by more than 40 pounds when the AAC diet was fed. During the initial month in the commercial feedlot, when bovine respiratory disease, BRD, incidence is elevated in feeder cattle, the proportion of calves treated for BRD symptoms was reduced in calves from AAC cows compared with calves from INR and CON cohorts (Table 2).

During gestation, zinc, copper, manganese and cobalt are also essential for development of the fetal immune system, suggesting that feeding the AAC diet to late-gestating cows also resulted in programming effects on postnatal offspring health.

Final calf body weight and hot carcass weight upon slaughter remained greater for calves from AAC cows compared with calves from CON cows, and similar among calves from INR cows compared with AAC and CON (Table 2).

Implications

Results from this experiment are suggestive of programming effects on postnatal offspring growth and health resultant from the AAC treatment. Supplementing late-gestating beef cows with an organic cobalt, copper, zinc and manganese appears to be an alternative to optimize offspring productivity in beef production systems. The complete publication can be found at https://academic.oup.com/jas/article-abstract/94/3/1215/4702748. 

Table 1. Concentrations of cobalt, Co; copper, Cu; manganese, Mn; and zinc, Zn, in beef cows prior to calving, placental cotyledon, and newborn calf. Within rows, means with different superscripts are statistically different.

Item	CON	INR	AAC	P =
Cows
Co, ppm	0.21a	0.40b	0.44c	< 0.01
Cu, ppm	69a	155b	129c	< 0.01
Mn, ppm	8.7	9.0	8.7	0.67
Zn, ppm	211a	230b	235b	0.05
Cotyledon
Co, ppm	0.13a	0.20b	0.24b	0.02
Cu, ppm	3.88a	4.75ab	5.12b	0.09
Mn, ppm	22.0	18.2	22.9	0.73
Zn, ppm	65	66	68	0.87
Newborn calf
Co, ppm	0.09a	0.12b	0.13b	< 0.01
Cu, ppm	362a	428ab	450b	0.10
Mn, ppm	5.82	5.22	5.83	0.43
Zn, ppm	456a	562ab	660b	0.01

Table 2. Calf performance and carcass parameters. Within rows, means with different superscripts are statistically different.

Item	CON	INR	AAC	P =
Weaning and preconditioning results
Calf weaning weight, lbs	466a	491ab	519b	0.04
Calf value, $	660a	692ab	730b	0.04
Calf 205-d adjusted weaning weight, lbs	537a	554ab	579b	0.05
Calf value,$	757a	781ab	815b	0.09
Preconditioned calf weight, lbs	539a	561ab	583b	0.05
Calf value,$	756a	793ab	822b	0.05
Feedlot performance
Treated for BRD symptoms, %	42.3	59.1	20.0	0.02
Calf weight at the end of feedlot, lbs	1428a	1459ab	1496b	0.10
Feedlot daily gain, lbs/d	3.51	3.54	3.60	0.53
Carcass characteristics
HCW, kg	900a	920ab	942b	0.10
Backfat, in	0.87	0.89	0.89	0.97
Ribeye area, in2	14.9	14.8	15.2	0.53
KPH, %	2.71	2.94	2.73	0.46
Marbling	513	509	508	0.99
Yield grade	3.89	4.06	3.94	0.81
Retail product, %	47.7	47.3	47.5	0.80
Choice, %	87.7	97.1	92.1	0.46

– by Reinaldo F. Cooke, Professor, Department of Animal Science