Milk Production and Energetic Metabolism of Heat-Stressed Dairy Goats Supplemented with Propylene Glycol

Abstract

Heat-stressed dairy animals increase their reliance on glucose. This elevated glucose demand is partially met by increasing the conversion of glucogenic amino acids (AA) in the liver. Propylene glycol (PG) is a glucogenic precursor and was not tested in dairy goats under thermoneutral (TN) and heat stress (HS) conditions simultaneously. We hypothesize that if HS-goats are fed with PG, they would get more glucose and consequently spare more glucogenic AA for milk protein synthesis rather than gluconeogenesis. Eight multiparous dairy goats (40.8 ± 1.1 kg body weight; 84 ± 1 days in milk) were used in a replicated 4 × 4 Latin square design of 4 periods; 21 d each (14 d adaptation, 5 d for measurements, and 2 d of transition). Goats were allocated to one of 4 treatments in a 2 × 2 factorial arrangement. Factors were control (CO) without PG or 5% of PG, and thermoneutral (TN; 15 to 20 °C) or heat stress (HS; 12 h/d at 37 °C and 12 h/d at 30 °C) conditions. Feed intake, rectal temperature, respiratory rate, milk yield, milk composition, and blood metabolites were measured. Compared to TN, HS goats had lower (p < 0.01) feed intake (–34%), fat-corrected milk (–15%), and milk fat (–15%). Heat-stressed goats also tended (p < 0.10) to produce milk with lower protein (–11%) and lactose (–4%) contents. Propylene glycol increased blood glucose (+7%; p < 0.05), blood insulin (+37%; p < 0.10), and body weight gain (+68%; p < 0.05), but decreased feed intake (–9%; p < 0.10) and milk fat content (–23%; p < 0.01). Furthermore, blood non-esterified fatty acids (–49%) and β-hydroxybutyrate (–32%) decreased (p < 0.05) by PG. In conclusion, supplementation of heat-stressed dairy goats with propylene glycol caused milk fat depression syndrome, but reduced body weight loss that is typically observed under HS conditions. Supplementation with lower doses of PG would avoid the reduced feed intake and milk fat depression, but this should be tested.

Effects of management strategies on animal welfare and productivity under heat stress: A synthesis

“…Nevertheless, these strategies have lower efficacy in case of severe HS variations. This is in line with Gonzalez-Rivas et al (75), Gao et al (76), Mehaba et al (65), and Hamzaoui et al (77). The likelihood of worst performances is 387.9% higher.…”

Influence of goat management systems on hematological, oxidative stress profiles, and parasitic gastrointestinal infection

“…The goats lost weight gradually in the BARN group, harming the appetite center of the hypothalamus, causing a decrease in feed intake, and entering a stage of negative energy balance. Consequently, the body decreases in weight [20,22]. Hematological parameters are one of the indicators that can evaluate health status and assess responses to stressful conditions.…”

“…The goats lost weight gradually in the BARN group, harming the appetite center of the hypothalamus, causing a decrease in feed intake, and entering a stage of negative energy balance. Consequently, the body decreases in weight [ 20 , 22 ].…”

Optimizing Feed Formulation Strategies for Attaining Optimal Nutritional Balance in High-Performing Dairy Goats in Intensive Farming Production Systems

“…Scientific investigations have delineated how heat stress perturbations can engender alterations in the thermophysiological parameters and lactational performances of dairy goats, thereby exerting discernible ramifications on their energy equilibrium and overarching metabolic milieu [11,12]. Additionally, inquiries into the effects of propylene glycol supplementation amidst heat-stressed dairy goats have elucidated its impact on milk productivity and energetic metabolism across divergent environmental milieus, underscoring its potential significance [13]. Furthermore, the evaluation of multinutrient blocks, integrating constituents like avocado pulp and peels, has shed light on alternative nutritional paradigms aimed at bolstering energy requisites, thereby enriching our understanding of dietary strategies in dairy goat management [14].…”