Level of canola source fat in pregnant beef cow diets - effects on cow and calf performance
Term: 4 years, ending April 2025
Status: Completed
Researcher: Bart Lardner, John McKinnon, Kathy Larson, Erika Cornand, Cabri Tanchak (University of Saskatchewan); Carolyn Fitzsimmons (University of Alberta)
SaskCanola Investment: $25,000
Total Project Cost: $421,179
Funding Partners: Saskatchewan Cattlemen's Association, Beef Cattle Research Council
Objectives
Identify the optimal level of canola fat supplementation that will enhance cow performance including pregnancy rates and milk production and quality.
Determine if there are any differences related to dietary treatments in levels of beta-hydroxybutyrate (BHBA) and non-esterified fatty acids (NEFAs) in cow blood profiles.
Identify the optimal level of canola fat supplementation in dam diets that will enhance progeny birth weight, weaning weight, slaughter weight, and carcass characteristics.
Quantify the economic impact of supplementing gestating beef cows through a marginal analysis.
Project Description
A 3-year study was conducted to evaluate the effects of supplementing canola fat to gestating beef cows on dam performance, milk yield, milk quality, post-treatment reproductive success, blood metabolite levels, progeny performance, progeny carcass characteristics and progeny blood metabolites. A supplement pellet was formulated based with canola seed to target an ether extract value of 6-8 percent. Each year, 72 Angus cross, multiparous, pregnant beef cows were allocated based on stage of gestation and body weight (BW) and randomly assigned to 1 of 3 replicated treatments in a randomized complete block design. Treatments fed throughout mid-late gestation included control (CON), low fat (LF) and high fat (HF) diets, supplemented with 0, 150 or 300 g fat/head/day, respectively. Prior to calving, all treatments were switched to CON diets. As fat inclusion increased, pregnancy rate tended to quadratically increase for LF fed cows compared to CON and HF fed cows. As fat inclusion in the dam diets increased, male calf birth weights tended to linearly decrease, however, this effect did not carry over to weaning. As dam diets increased in fat content, heifer progeny blood cholesterol at slaughter increased linearly. Steer progeny cholesterol increased quadratically at weaning, with maximum values in the LF treatment animals, however, this did not carry over to slaughter. Instead, steer insulin-like growth factor (IGF-1) levels at slaughter linearly increased as the level of fat in dam diets increased. Throughout the backgrounding phase, heifer progeny average daily gain (ADG) decreased linearly and steer progeny final background weight tended to decrease quadratically, with steers born to LF fed dams having the lowest weight. However, these effects did not carryover to the finishing phase where the steer progeny gain:feed ratio increased linearly as fat inclusion levels increased in the dam diet. Carcass characteristic of marbling score in heifer progeny linearly increased as fat inclusion levels increased in dam diets. The results of supplementing canola fat in mid to late gestating beef cow diets suggests improved reproductive performance of the dam and increased feedlot performance of steer progeny.
Grower Benefits
Supplementing canola fat to gestating beef cattle had similar effects on prepartum dam performance and milk yield and quality. However, there was a quadratic tendency for pregnancy rate to increase for cows receiving LF diets compared to CON and HF fed cows. Dietary treatments did not affect NEFA or BHBA blood levels of cows. A marginal analysis suggests that LF treatments tended to generate the highest net return per pen, despite a linear increase in ration cost as fat level increased in diets. This is likely attributed to the reduced cost of replacing open cows following the period when cows received LF treatments. A tendency for male calf birth weights to decrease linearly with increased dam dietary fat was observed, however, this effect was not carried over to weaning. Blood cholesterol increased linearly in heifers at slaughter and decreased quadratically for steer progeny at weaning. Blood metabolite IGF-1 increased linearly in steer progeny at slaughter. Post-weaning, heifer progeny weight, DMI and gain:feed ratio were similar, however, it should be noted that ADG decreased linearly in backgrounded heifer progeny as fat levels in dam diets increased. Post-weaning, steer progeny weights, DMI, and ADG were similar. There was a tendency for steer final background weight to increase quadratically, with steers born to cows receiving LF diets being the heaviest. However, this change did not carry over to the end of finishing for steers. Instead, a linear increase in gain:feed ratio was observed for steers during the finishing period. For carcass characteristics, heifer marbling score increased linearly as dam dietary fat supplementation increased, however, no other differences were observed. Overall, the following research findings suggest that pregnant cows receiving fat supplementation during mid to late gestation can improve reproductive efficiency, improve performance of steers born to those cows, both of which may be economically viable for the beef producer. Further research needs to explore the reproductive lifetime of heifer calves born to cows receiving diets supplemented with canola-source fat.