The relevance of methane emissions from beef production and the challenges of the Argentinean beef production platform.

The livestock sector faces the challenge to respond to the growing demand for animal protein from an expanding population while reducing environmental impact through GHG emissions. Globally about 2.836 million tons of CO2-eq were emitted by the beef production sector equivalent to 46,2 kg CO2-eq per kg carcass weight (CW). From the 1.485 million cattle head spread out over the world, 82% are on extensive grazing systems while only 18% are on high productive intensive systems. Among the top ten beef exporter countries, five are located in Latin America accounting a quarter of the global stock and two of them, Argentina and Uruguay, produce on temperate pastures under grazing systems. In Argentina, the livestock area was reduced in favor of increasing the grain cropping area, which took place in the last two decades. Production systems were intensified to maintain cattle stock. Cattle programs changed from 100% pasture to pasture supplemented with cereal grains and conserved forages, and confinement on grain feeding for fattening was incorporated. Due to land sharing competition with cash crops, no increment of cattle stock is expected therefore improving production efficiency appears as the only way to increase beef production while reducing methane emissions intensity. Beef produced on intensive grazing systems on supplemented pastures maintained organoleptic, nutritional and lipid profile than that of beef produced on pure grazing systems.

Silage chop length and hay supplementation on milk yield, chewing activity, and ruminal digestion by dairy cows.

The effects of whole-plant corn silage (CS) particle size and long unprocessed grass hay (LH) supplementation on milk yield, chewing activity, and ruminal digestion in dairy cows were evaluated in 2 experiments. In Experiment 1, corn silage harvested at fine (6 mm; FCS) or coarse (23 mm; CCS) theoretical cut length were fed to 22 lactating Holstein cows. Treatments were 2 total mixed rations containing 58% of dry matter (DM) as FCS or CCS. Diet DM intake tended to be higher in cows fed FCS than those fed CCS (23.4 vs. 22.1 kg/d). However, milk yield and composition, body condition score, and plasma metabolite concentrations were not affected by the dietary treatments. In the second experiment, 5 cannulated Holstein cows were used in a 5 x 5 Latin square design to evaluate the effects of the addition of LH to the diets evaluated in Experiment 1 on chewing activity and ruminal digestion. Treatments were 5 total mixed rations: FCS-based diet plus the addition of 0, 5, or 10% LH (DM basis) and CCS-based diet plus 0 or 5% LH. Long hay addition linearly decreased DM intake in cows fed FCS-based diets (25.0 to 21.7 kg/d), but increased DM intake in those fed CCS-based diets (22.7 to 27.1 kg/d). The intake of neutral detergent fiber (NDF) increased with LH addition in CCS-based diets (7.6 vs. 9.4 kg/d). Rumination time increased (16.8 to 21.0 min/kg of DM intake) when LH was added to FCS-based diets, but it decreased when included in CCS-based diets (18.8 vs. 12.9 min/kg of DM intake). Ruminal pH was higher (5.9 vs. 5.7) and lag-time for in situ NDF disappearance was shorter (3.5 vs. 8.7 h) for cows fed CCS compared with cows fed FCS. The rate of NDF disappearance tended to be higher for the CCS-based diet with 5% LH than for the diet with 0% LH (2.0 vs. 4.4 %/h), but solids passage rate was not affected by the treatments. These results suggest that addition of LH to FCS-based diets does not affect ruminal environment or digestion, but depressed DM intake. In contrast, addition of LH to CCS-based diets may improve ruminal NDF digestion, increasing DM intake by reducing filling effect and time needed for rumination.

Ruminal digestion by dairy cows grazing winter oats pasture supplemented with different levels and sources of protein.

Six Holstein cows fitted with ruminal cannulae were used in two simultaneous 3 x 3 Latin squares to study the effects of protein supplements on ruminal fermentation and in situ crude protein degradability. Cows rotationally grazed a winter oats (Avena sativa L.) pasture and were supplemented with one of three concentrate supplements: 1) low protein sunflower meal (L-SM); 2) high protein sunflower meal (H-SM); or 3) high protein feather meal (H-FM). Concentrates (6.5 kg/d) were offered in equal portions twice daily during milking. Ruminal pH and total volatile fatty acids concentration were unaffected by treatments. Supplementation with L-SM and H-FM decreased ruminal NH3-N concentration compared with H-SM. The concentrate with feather meal had lower effective rumen degradability of crude protein than concentrates containing sunflower meal. Effective rumen degradability of crude protein of pasture averaged 82.7%. Thirty-six multiparous Holstein cows (71 d in milk) were used in a complementary experiment to study the effect of treatments on intake, milk yield, and milk composition. Pasture (13.2 kg/d) and total (19.6 kg/d) dry matter intake (estimated using Cr2O3 as fecal marker) and milk yield (20.5 kg/d) were unaffected by level or source of protein supplemented. Intake of rumen undegradable protein in grazing dairy cows was higher when the amount of sunflower meal was increased or when feather meal was used in the supplement. However, higher rumen undegradable protein intake did not increase milk production, suggesting that rumen undegradable protein was not limiting for cows on pasture producing less than 22 kg of milk.