|Sawyer, Jason - TEXAS A&M|
|Mathis, Clay - NEW MEXICO STATE UNIV|
|Hawkins, Dean - NEW MEXICO STATE UNIV|
|Donart, Gary - NEW MEXICO STATE UNIV|
|Petersen, Mark - NEW MEXICO STATE UNIV|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 12, 2005
Publication Date: February 20, 2006
Citation: Waterman, R.C., Sawyer, J.E., Mathis, C.P., Hawkins, D.E., Donart, G.B., Petersen, M.K. 2006. Effects of supplements that contain increasing amounts of metabolizable protein with or without ca-propionate salt on postpartum interval and nutrient partitioning in young beef cows. Journal of Animal Science 84:433-446. Interpretive Summary: Cattle grazing dormant New Mexico rangelands show yearly variation in response to supplementation. This reaction maybe partially due to differences in glucose (blood sugar) availability and metabolism, which maybe altered by forage conditions. Unlike people, cows absorb no sugar from their diet and must make all of their sugar in the liver. Nutritional status of young cows with suckling calves varies by year depending upon the onset and magnitude of green forage growth. A study at the Corona Range and Livestock Research Center during two dry years 2000 and 2001 (driest) evaluated range protein supplements differing in source and quantity of ingredients that could be used for glucose production in a cow. Supplements fed to forty-two black baldie 2-year-old post-partum cows at 2 lbs per day and provided 0.7lb crude protein (CP) per day. Three supplements all 36% crude protein were tested and they differed in ingredients that could be used to make glucose by the cows. The first supplement treatment was a traditional good quality cottonseed meal based cube (36 % CP) that has a low glucose potential (logluc). The second contained cottonseed meal and bypass proteins (blood and feather meal) which would have a moderate glucose potential (midgluc) and lastly the midgluc supplement with a propionate salt (NutroCal ' Kemin Industries Inc) added giving it a high glucose potential (higluc). Supplements were individually fed 2 times per week at 11:00 am on Mondays and Fridays for approximately 90 d after calving. Cows rotationally grazed three pastures during the study. Cow and calf body weight change, milk production, days to first estrus, pregnancy rate and glucose tolerance were measured during the study. The effect of year and treatment (supplements) did not interact so the data was pooled for both years Table 1. Young cows fed range supplements with higher glucose potential cycled sooner. Logluc Midgluc Higluc Probability Cow wt change (calving-breed) 46.0 lb 22.5 lb 38.3 lb P > 0.1 Milk production 11.9 lb 14.3 lb 13.2 lb P > 0.1 Calf weaning wt 465 lb 480 lb 469 lb P > 0.1 Days to 1st estrus 119 114 110 P < 0.08 Fall pregnancy % 83 92 83 P > 0.1 Glucose ½ life 100 min 69 min 56 min P < 0.08 Although fall pregnancy rates were similar for cows fed each supplement the cows fed the higluc supplement cycled 9 days earlier than the cows consuming the logluc supplement. The lowered glucose half-life (44 minutes lower) in the higluc supplemented cows compared to the logulc fed cows may partially demonstrate an improvement in glucose condition of these cows.
Technical Abstract: Cattle grazing winter range forages exhibit interannual variation in response to supplementation. This variation may be mediated by circulating concentrations and subsequent metabolism of glucose, which are influenced by forage quality and availability. A study conducted at the Corona Range and Livestock Research Center during two dry yr evaluated responses of young postpartum beef cows (n = 51; initial BW 406 ± 6 kg; BCS 4.6 ± 0.05 in yr 1, while n = 36; initial BW 392 ± 6 kg; BCS 4.5 ± 0.06 in yr 2) to supplements that differed in glucogenic potentials (GP). Supplements were fed at 908 g'cow-1'd-1 and provided 327 g CP, 118 g RUP, 47 g GP; (LOGLUC; n = 29); 327 g CP, 175 g RUP, 63.0 g GP (MIDGLUC; n = 29); or 327 g CP, 180 g RUP + 100 g propionate salt, 144 g GP (HIGLUC; n = 29; NutroCal', Kemin Industries, Inc. Des Moines, IA). Body weights were recorded once every two wk and blood samples collected once per wk in yr 1 and twice per wk in yr 2 for approximately 100 d postpartum. Postpartum anestrous period was evaluated by progesterone (P4) from wk blood samples and pregnancy was confirmed by rectal palpation at weaning. A linear reduction in the postpartum interval (P = 0.05) revealed that cows fed HIGLUC returned to estrus 9-d sooner than the LOGLUC supplemented cows; however, there were no differences in pregnancy percentages. A postpartum glucose tolerance test was conducted near cow BW nadir to evaluate glucose clearance rate. Glucose tolerance tests demonstrated (P = 0.07) that HIGLUC supplemented cows had greater rates of glucose clearance, which may have influenced the observed abbreviation of the postpartum interval. A glucose tolerance test conducted after cessation of supplemental treatments revealed no differences in glucose clearance (P = 0.47) among previously supplemented cows. These data suggest that not only vegetative quality, duration of lactation, season of grazing but also type of supplementation play pivotal roles in the young postpartum beef cows ability to respond and incorporate nutrients into insulin sensitive tissues.