مدیریت استرس گرمایی در گاوهای شیری

یکی از چالش های تولیدکنندگان شیر. در خاورمیانه و آمریکای شمالی مقابله با استرس گرمایی در گاوهای شیری است. چرا که در این مناطق. دمای هوا در اواسط روز اغلب بیش از 40 درجه سانتیگراد است. و این تولیدکنندگان مجبورند. مدت زمان زیادی برای خنک نگه داشتن گاوهای خود تلاش نمایند. شواهد فزاینده ای وجود دارد. که حتی دمای نسبتاً پایین تجربه شده. در تابستان می تواند. منجر به مصرف کمتر خوراک. تولید کم...

Name: Calcium salts of polyunsaturated fatty acids deliver more essential fatty acids to the lactating dairy cow

Authors: M.L.Theurer*1E.BlockW.K.Sanchez2M.A.McGuire*

Address: *Department of Animal and Veterinary Science, University of Idaho, Moscow 83844Arm & Hammer Animal Nutrition Group, Church & Dwight Co. Inc., Princeton, NJ 08543

Abstract: Recent research has focused on the importance of supplying essential fatty acids to the lactating dairy cow. The addition of essential fatty acids, specifically linoleic and linolenic acid, to dairy cow diets has been investigated as a method to increase reproductive efficiency. Rumen bacteria, however, biohydrogenate polyunsaturated fatty acids (PUFA) to saturated fatty acids. This is an important issue because it can also lead to milk fat depression when unsaturated fatty acids are fed. The formation of Ca salts has previously been shown to partially protect unsaturated fatty acids from rumenbiohydrogenation. The objective of this experiment was to evaluate feed intake, milk production, and milk composition of cows fed Ca salts of palm fatty acids (CS) compared with those fed Ca salts of palm fatty acids with an increased content of PUFA (CS+PUFA). Nineteen lactating Holstein cows were used in a switchback experiment to determine any differences between CS and CS+PUFA on milk production and composition. This experiment consisted of 3 consecutive periods of 14 d. Treatments were formulated to provide 450 g/d (dry matter basis) of the Ca salt supplement and were mixed with the same basal ration. Milk weights and feed intakes were recorded daily for each cow. Milk samples were collected the last 2 d of each period and analyzed for milk composition and fatty acids. Dry matter intake [28.0 vs. 27.0 kg/d; standard error of the mean (SEM) = 0.4] and milk production (44.4 vs. 44.0 kg/d; SEM = 0.7) were not different between treatments for CS and CS+PUFA, respectively. Milk fat percentage (3.34 vs. 3.22%; SEM = 0.07) and milk protein percentage (2.78 vs. 2.80%; SEM = 0.01) were not different for CS- and CS+PUFA-fed cows. Feeding CS+PUFA reduced the concentration of palmitic acid in milk fat (28.3 vs. 26.8 wt%; SEM = 0.3). Supplementation of CS+PUFA increased the linoleic acid concentration (3.96 vs. 4.61 wt%; SEM = 0.1) of milk fat, indicating that linoleic acid was partially protected from rumen bio hydrogenation. Concentrations of conjugated linoleic acid were also increased (0.44 vs. 0.52 wt%; SEM = 0.02) when cows consumed CS+PUFA, indicating that some bio hydrogenation did occur. Supplementing CS+PUFA did not alter milk production, milk fat percentage, or dry matter intake when compared with CS. The CS+PUFA supplement supplied more linoleic acid to the small intestine for milk fat synthesis.

Key Words: milk; polyunsaturated fatty acid; milk fat; dry matter intake

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Name: Challenges in enriching milk fat with polyunsaturated fatty acids

Authors: Jennifer Stamey Lanier1 and Benjamin A. Corl2*

Address: *Department of Animal and Veterinary Science, University of Idaho, Moscow 83844†Arm & Hammer Animal Nutrition Group, Church & Dwight Co. Inc., Princeton, NJ 08543

Abstract: Milk fatty acid composition is determined by several factors including diet. The milk fatty acid profile of dairy cows is low in polyunsaturated fatty acids, especially those of the n-3 series. Efforts to change and influence fatty acid
profile with longer chain polyunsaturated fatty acids have proven challenging. Several barriers prevent easy transfer of dietary polyunsaturated fatty acids to milk fat including rumen bio hydrogenation and fatty acid esterification. The
potential for cellular uptake and differences in fatty acid incorporation into milk fat might also have an effect, though this has received less research effort. Given physiological impediments to enriching milk fat with polyunsaturated fatty
acids, manipulating the genome of the cow might provide a greater increase than diet alone, but this too may be challenged by the physiology of the cow

Key Words: : Dairy cow, Milk fat, Polyunsaturated fatty acids

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Name: Effect of stearic or oleic acid on milk performance and energy partitioning when fed in diets with low and high rumen-active unsaturated fatty acids in early lactation

Authors: Chen Yanting, Guiling Ma, Joseph H Harrison, Elliot Block

Address:*Department of Animal Science, Washington State University, Pullman, WA 99164, †
Department of Animal Science, Washington State University, Puyallup, WA 98731, and ‡
Church and Dwight Animal Nutrition, Princeton, NJ 08543
1These authors contributed equally to the research.
2 Corresponding author: jhharrison@wsu.edu

Abstract: This experiment was conducted to determine the effects of stearic acid (SA; C18:0) or rumen-protected oleic acid (OA; C18:1 cis-9) on milk performance and energy partitioning of early lactation cows when supplemented in diets with low and high level of rumen unsaturated fatty acids (RUFA). In low RUFA experiment (LRUFA), FA supplement rich in either SA or calcium salts OA was added to a basal diet with a low concentration of RUFA (0.75% vs. 1.4%, LRUFA-SA vs. LRUFA-OA). In high RUFA experiment (HRUFA), 2% soybean oil was added to the diet fed in the LRUFA experiment. In each experiment, 30 multiparous cows were blocked by parity and predicted transmitting ability for milk yield and were randomly fed 1 of 2 treatment diets from 2 to 13 wk postpartum. In the LRUFA experiment, LRUFA-SA had 2.4 kg/d more dry matter intake (DMI) (P < 0.01), 3.8 kg/d more energy-corrected milk (P < 0.01), and 0.3% units more milk fat percentage (P < 0.01) and 0.2 kg/d more milk fat yield (P < 0.01). Dietary treatments did not affect body weight, energy balance, and energy intake partitioning into milk, maintenance, and body tissues (P > 0.1). In the HRUFA experiment, HRUFA-SA had 1.4 kg/d more DMI (P = 0.03) but similar milk and milk components yields (P > 0.1). HRUFA-SA had a tendency to gain more body weight (P = 0.07) and had more positive energy balance (P = 0.01) and decreased gross feed efficiency (milk yield/DMI) (P = 0.01). Consistently, HRUFA-SA increased intake energy partitioning into body tissues (P = 0.02) and decreased energy partitioning into milk (P = 0.01). In summary, SA supplementation had more DMI relative to OA, but the effects on milk and milk fat production were different and affected by the level of RUFA in the basal diet. In application, SA supplementation was more effective to improve milk production when included in the basal diet with the low RUFA.

Key Words: dairy cows, fatty acids, milk fat, ruminal bio hydrogenation

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Name: Fat source and dietary forage-to-concentrate ratio influences milk fatty-acid composition in lactating cows

Authors: M Vazirigohar 1M Dehghan-Banadaky 1K Rezayazdi 1S J Krizsan 2A Nejati-Javaremi 1K J Shingfield 3

Address:

  • 1 Department of Animal Science, Campus of Agriculture and Natural Resources, University of Tehran, 31587-77871 Karaj, Iran.
  • 2 Department of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences, S-90183 Umeå, Sweden.
  • 3 MTT Agrifood Research Finland, Animal Production Research, FI-31600 Jokioinen, Finland.

Abstract: On the basis of the potential benefits to human health there is an increased interest in producing milk containing lower-saturated fatty acid (SFA) and higher unsaturated fatty acid (FA) concentrations, including cis-9 18:1 and cis-9, trans-11-conjugated linoleic acid (CLA). Twenty-four multiparous Holstein cows were used in two experiments according to a completely randomized block design, with 21-day periods to examine the effects of incremental replacement of prilled palm fat (PALM) with sunflower oil (SFO) in high-concentrate diets containing 30 g/kg dry matter (DM) of supplemental fat (Experiment 1) or increases in the forage-to-concentrate (F : C) ratio from 39 : 61 to 48 : 52 of diets containing 30 g/kg DM of SFO (Experiment 2) on milk production, digestibility and milk FA composition. Replacing PALM with SFO had no effect on DM intake, but tended to increase organic matter digestibility, yields of milk, protein and lactose, and decreased linearly milk fat content. Substituting SFO for PALM decreased linearly milk fat 8:0 to 16:0 and cis-9 16:1, and increased linearly 18:0, cis-9 18:1, trans-18:1 (Δ4 to 16), 18:2 and CLA concentrations. Increases in the F : C ratio of diets containing SFO had no effect on intake, yields of milk, milk protein or milk lactose, lowered milk protein content in a quadratic manner, and increased linearly NDF digestion and milk fat secretion. Replacing concentrates with forages in diets containing SFO increased milk fat 4:0 to 10:0 concentrations in a linear or quadratic manner, decreased linearly cis-9 16:1, trans-6 to -10 18:1, 18:2n-6, trans-7, cis-9 CLA, trans-9, cis-11 CLA and trans-10, cis-12 CLA, without altering milk fat 14:0 to 16:0, trans-11 18:1, cis-9, trans-11 CLA or 18:3n-3 concentrations. In conclusion, replacing prilled palm fat on with SFO in high-concentrate diets had no adverse effects on intake or milk production, other than decreasing milk fat content, but lowered milk fat medium-chain SFA and increased trans FA and polyunsaturated FA concentrations. Increases in the proportion of forage in diets containing SFO increased milk fat synthesis, elevated short-chain SFA and lowered trans FA concentrations, without altering milk polyunsaturated FA content. Changes in fat yield on high-concentrate diets containing SFO varied between experiments and individual animals, with decreases in milk fat secretion being associated with increases in milk fat trans-10 18:1, trans-10, cis-12 CLA and trans-9, cis-11 CLA concentrations.

Key Words: conjugated linoleic acid, , milk fat, saturated fatty acid, trans fatty acid

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