Dietary inclusion of ruminally protected linseed oil as a means to mitigate heat and slaughter-induced stress in feedlot cattle

CECONI, I.; PIGHÍN, DARÍO GABRIEL; DAVIES, P.; CUNZOLO, S.A.; PAZOS, A.A.; GRIGIONI, G.

JOURNAL OF ANIMAL SCIENCE

AMER SOC ANIMAL SCIENCE

Lugar: Urbana; Año: 2022 vol. 100 p. 1 - 11

0021-8812

There is evidence of a relationship between increased energy intake and the development of metabolic inflammation and insulin resistance (IR),and between the aforementioned metabolic state and impaired tolerance to heat stress. Based on the anti-inflammatory properties and mitigatingeffects on IR and stress of n-3 polyunsaturated fatty acids (n-3 PUFA), an experiment was performed to evaluate the effect of n-3 PUFAsupplementation to feedlot-finished steers during summer on animal performance, physiological and biochemical variables associated withglucose metabolism, heat and preslaughter-induced stress, and meat quality. A total of 48 Angus steers (388 ± 2 kg) were fed one of three cornbasedfinishing diets containing (dry matter basis) 0% added oil (CON; negative control), or 1.90% of sunflower oil-calcium salt (SUN; positivecontrol), or 1.92% of linseed oil-calcium salt (LIN). There was a trend (P = 0.08) for greater dry matter intake (DMI) and greater (P = 0.02) averagedaily gain (ADG) in LIN-fed animals compared with the average between those that received the CON or SUN diets, whereas no differences(P ≥ 0.34) were observed between the latter. No other performance, physiological, or carcass variables were affected (P ≥ 0.12) by treatment.Blood glucose and insulin were similar (P ≥ 0.14), though the homeostatic model assessment (HOMA) which gauges IR tended (P = 0.06) to bereduced for LIN-fed animals compared with the average between those that received the CON or SUN diets. Blood insulin and HOMA increasedlinearly (P ≤ 0.01) with days on feed. An interaction between the study phase (feeding period or slaughter) and treatment was observed (P ≤ 0.05)for glucose and cortisol. While the magnitude of glucose increase (P < 0.01) from the end of the feeding period to slaughter was greater for CONandSUN-fed animals compared with LIN-fed ones, cortisol increased (P < 0.05) only in animals that received CON or SUN diets. Meat qualityattributes were not affected (P ≥ 0.16) by treatment. The concentration of n-3 PUFA was greater (P < 0.01) and n-6:n-3 ratio was lesser (P < 0.01)in meat from LIN-fed animals compared with that resulting from the average between the animals that received the negative (CON) or positive(SUN) control diets. Results suggest that n-3 PUFA supplementation mitigated metabolic alterations associated with IR and preslaughter-relatedstress. It may have also improved tolerance to heat, resulting in greater DMI and ADG of steers fed a high-energy diet during summer. Resultsalso indicate that glucose metabolism and heat stress tolerance worsen with time when feeding concentrate-based diets.