Effects of energy balance and metabolizable protein level on tissue mobilization and milk performance of dairy cows in early lactation

Concurrent and carryover effects of feeding blends of protein and amino acids in high-protein diets with different concentrations of forage fiber to fresh cows. 2. Protein balance and body composition

Increasing the supply of metabolizable protein (MP) and improving its AA profile may attenuate body protein mobilization in fresh cows and lead to increased milk production. Increasing the concentration of rumen-undegradable protein (RUP) to increase MP supply and replacing RUP sources from forages instead of nonforage fiber sources may further decrease tissue mobilization if it improves dry matter intake (DMI). Our objective was to determine whether increasing MP concentrations and improving the AA profile at the expense of either nonforage or forage fiber (fNDF) would affect MP balance and empty body (EB) composition (measured using the urea dilution method) in early postpartum dairy cows of different parities. In a randomized block design, 40 primigravid [77 ± 1.5 kg of EB crude protein (CP) at 8 ± 0.6 d before calving] and 40 multigravid (92 ± 1.6 kg of EB CP at 5 ± 0.6 d before calving) Holsteins were blocked by calving date and fed a common prepartum diet (11.5% CP). After calving to 25 d in milk (DIM), cows were fed 1 of 4 diets: (1) a diet deficient in MP meeting 87% of MP requirements (DMP, 17% CP, 24% fNDF), (2) 104% of MP requirements using primarily soy protein to make MP adequate (AMP, 20% CP, 24% fNDF), (3) 110% of MP requirements using a blend of proteins and rumen-protected (RP) AA to make MP adequate (Blend, 20% CP, 24% fNDF), or (4) a diet similar to Blend but substituting added RUP for fNDF rather than nonforage NDF (Blend-fNDF, 20% CP, 19% fNDF). Blend was formulated to have a RUP supply with a similar AA profile to that of casein. Cows were fed a common diet (16.3% CP) from 26 to 50 DIM. Calculated MP balance (supply - requirements) was less than zero for DMP and Blend-fNDF from 1 to 4 wk of lactation (WOL), whereas that for AMP was positive from 1 to 4 WOL and that for Blend was close to zero from 3 to 4 WOL. Daily MP balance was greater from 5 to 7 WOL for DMP compared with AMP and Blend (100 vs. 22 g/d). From -7 to 7 d relative to calving, losses of EB CP were greater for DMP than for AMP and Blend (-121 vs. average of 11 g/d). From 7 to 25 DIM, cows fed AMP (-139 g/d) and Blend-fNDF (-147 g/d) lost EB CP but cows fed Blend (-8 g/d) maintained EB CP. Increased DMI for Blend versus AMP led to reduced losses of EB lipid in primiparous cows from 7 to 25 d relative to calving (-1.0 vs. -1.3 kg/d of EB lipid), whereas lipid mobilization was similar in multiparous cows (average -1.1 kg of EB lipid/d). By 50 DIM, EB lipid and CP were similar across treatments and parities (average 60.2 kg of EB lipid and 81.6 kg of EB CP). Overall, feeding fresh cows a high MP diet with a balanced AA profile improved DMI and attenuated EB CP mobilization, which could partly explain positive carryover effects on milk production for multiparous cows and reduced lipid mobilization for primiparous cows.

Concurrent and carryover effects of feeding blends of protein and amino acids in high-protein diets with different concentrations of forage fiber to fresh cows. 1. Production and blood metabolites

Because of low feed intake during the first weeks of lactation, dietary concentration of metabolizable protein (MP) must be elevated. We evaluated effects of providing additional rumen-undegradable protein (RUP) from a single source or a blend of protein and AA sources during the first 3 wk of lactation. We also evaluated whether replacing forage fiber (fNDF) or nonforage fiber with the blend affected responses. In a randomized block design, at approximately 2 wk prepartum, 40 primigravid (664 ± 44 kg of body weight) and 40 multigravid (797 ± 81 kg of body weight) Holsteins were blocked by calving date and fed a common diet (11.5% crude protein, CP). After calving to 25 d in milk (DIM), cows were fed 1 of 4 diets formulated to be (1) 20% deficient in metabolizable protein (MP) based on predicted milk production (17% CP, 24% fNDF), (2) adequate in MP using primarily RUP from soy to increase MP concentration (AMP; 20% CP, 24% fNDF), (3) adequate in MP using a blend of RUP and rumen-protected AA sources to increase MP concentration (Blend; 20% CP, 24% fNDF), or (4) similar to Blend but substituting fNDF with added RUP rather than nonforage neutral detergent fiber (Blend-fNDF; 20% CP, 19% fNDF). The blend was formulated to have a RUP supply with an AA profile similar to that of casein. A common diet (17% CP) was fed from 26 to 92 DIM, and milk production and composition were measured from 26 to 92 DIM, but individual dry matter intake (DMI) was measured only until 50 DIM. During the treatment period for both parities, AMP and Blend increased energy-corrected milk (ECM) yields compared with the diet deficient in MP based on predicted milk production (40.7 vs. 37.8 kg/d) and reduced concentrations of plasma 3-methyl-His (4.1 vs. 5.3 µmol/L) and growth hormone (9.0 vs. 11.9 ng/mL). Blend had greater DMI than AMP (17.4 vs. 16.1 kg/d), but ECM yields were similar. Blend had greater plasma Met (42.0 vs. 26.4 µmol/L) and altered metabolites associated with antioxidant production and methyl donation compared with AMP. Conversely, the concentration of total essential AA in plasma was less in Blend versus AMP (837 vs. 935 µmol/L). In multiparous cows, Blend-fNDF decreased DMI and ECM yield compared with Blend (19.2 vs. 20.1 kg/d of DMI, 45.3 vs. 51.1 kg/d of ECM), whereas primiparous cows showed the opposite response (15.3 vs. 14.6 kg/d of DMI, 32.9 vs. 31.4 kg/d of ECM). Greater DMI for multiparous cows fed Blend carried over from 26 to 50 DIM and was greater compared with AMP (23.1 vs. 21.2 kg /d) and Blend-fNDF (21.3 kg/d). Blend also increased ECM yield compared with AMP (49.2 vs. 43.5 kg/d) and Blend-fNDF (45.4 kg/d) from 26 to 92 DIM. Few carryover effects of fresh cow treatments on production were found in primiparous cows. Overall, feeding blends of RUP and AA may improve the balance of AA for fresh cows fed high MP diets and improve concurrent and longer-term milk production in multiparous cows. However, with high MP diets, multiparous fresh cows require greater concentrations of fNDF than primiparous cows.

Analysis of milk traits in relation to feeding level and organization in a herd of high-yielding cows

The aim of the study was to determine factors influencing the balance of energy and protein in high-yielding cows. Daily milk yield, lactation number and month of lactation were analysed. The study was carried out in a herd with yield of 11,000 kg milk/year, on 517 lactating cows. The cows were divided into four feeding groups. They were fed TMR calculated for levels of milk production, as follows: group 1 – for 45 kg, group 2 – for 35 kg, group 3 – for 26 kg and group 4 – for 20 kg. The actual mean milk yield for these groups was 49.1 kg, 38.1 kg, 26.3 kg and 17.5 kg per day. Each group consisted of cows in their first to sixth lactation and in their first to tenth month of lactation. No significant differences were noted in daily milk yield between lactation numbers or months of lactation. As milk yield increased in the groups, the content of fat and protein decreased. The estimated balance of energy, based on the protein percentage in the milk, was negative for nearly the entire lactation in group 1, for the first four months of lactation in group 2, for the first two months in group 3, and in the second month of lactation for group 4. Group 1 was divided into three subgroups according to yield: up to 45 kg, 45-50 kg and 50 kg or more. Energy was estimated to be wellbalanced only in the first subgroup. The balance of energy in the cows was strongly determined by daily milk yield, and to a lesser degree by the month of lactation. Protein, based on the concentration of urea in the milk, was well-balanced in groups 1 and 2. In groups 3 and 4, the recommended level of protein in the rations was exceeded by 10-20%.

Feeding protein supplements in alfalfa hay-based lactation diets improves nutrient utilization, lactational performance, and feed efficiency of dairy cows

Due to the increasing cost of soybean meal and concerns of excess N being excreted into the environment, new protein supplements have been developed. Two products that have shown potential in increasing N utilization efficiency are slow-release urea (SRU; Optigen; Alltech Inc., Nicholasville, KY) and ruminal-escape protein derived from yeast (YMP; DEMP; Alltech Inc.). The objective of this study was to assess the effects of feeding these 2 supplements in alfalfa hay-based [45.7% of forage dietary dry matter (DM)] dairy diets on nutrient utilization, feed efficiency, and lactational performance of dairy cows. Twelve multiparous dairy cows were used in a triple 4 × 4 Latin square design with one square consisting of ruminally cannulated cows. Treatments included (1) control, (2) SRU-supplemented total mixed ration (SRUT), (3) YMP-supplemented total mixed ration (YMPT), and (4) SRU- and YMP-supplemented total mixed ration (SYT). The control consisted only of a mixture of soybean meal and canola meal in a 50:50 ratio. The SRU and the YMP were supplemented at 0.49 and 1.15% DM, respectively. The experiment consisted of 4 periods lasting 28 d each (21 d of adaptation and 7 d of sampling). Cows fed YMPT and SYT had decreased intake of DM, and all supplemented treatments had lower crude protein intake compared with those fed the control. Milk yield tended to have the greatest increase in YMPT compared with the control (41.1 vs. 39.7 kg/d) as well as a tendency for increased milk fat and protein yields. Feed efficiencies based on yields of milk, 3.5% fat-corrected milk, and energy-corrected milk increased at 10 to 16% due to protein supplementation. Cows fed protein supplements partitioned less energy toward body weight gain, but tended to partition more energy toward milk production. Efficiency of use of feed N to milk N increased by feeding SRUT and YMPT, and milk N-to-manure N ratio increased with YMPT. Overall results from this experiment indicate that replacing the mixture of soybean meal and canola meal with SRU and YMP in alfalfa hay-based dairy diets can be a good approach to improve nutrient utilization efficiencies in lactating dairy cows.

Integration of physiological mechanisms that influence fertility in dairy cows

Fertility in dairy cows has been declining for the past three decades. Genetic selection for increased milk production has been associated with changes in key metabolic hormones (growth hormone, insulin, IGF and leptin) that regulate metabolism by homoeostasis and homeorhesis. These metabolic hormones, particularly insulin, provide signals to the reproductive system so that regulation of ovarian function is coordinated with changes in metabolic status. Studies have shown, for example, that increasing circulating insulin concentrations during the early post partum period can advance the resumption of oestrous cycles by enhancing follicular growth. However, high concentrations of insulin can be detrimental to the developmental competence of oocytes, which is also influenced by the supply of fatty acids at the systemic level and at the ovarian level. Insulin status is also associated with the incidence and characteristics of abnormal ovarian cycles. These changes can occur without significant variation in circulating gonadotrophin concentrations. This suggests that additional factors, such as peripheral metabolites, metabolic hormones and locally produced growth factors, may have a modulating role. Recent evidence has demonstrated that ovarian responses to metabolic signals and nutrient profile vary according to the stage of the reproductive cycle. Improved understanding of this multifactorial process enables nutrition to be matched to genotype and milk production, with a positive impact on pregnancy rate.

Prospects for using nonconventional feeds in diets for Awassi dairy sheep in Syria

High feed costs are major obstacles for resource-poor dairy sheep farmers in West Asia, along with large fluctuation in grain and straw prices. Farmers need low-cost diets using locally available feeds that can provide sufficient milk of good quality. Two experimental trials were conducted on Awassi milking ewes to evaluate nonconventional and balanced low-cost diets against the traditional unbalanced diet used by farmers (control) on the total yields (milk, fat, protein, and total solids) and milk composition (fat, protein, total solids, and lactose), an important indicator of milk quality. The first trial was conducted at the research station of the International Center for Agricultural Research in the Dry Areas (ICARDA, Aleppo, Syria) to test 6 low-cost balanced diets using locally available feeds and agro byproducts against the control diet. Each diet was tested on 8 ewes that were kept on pasture as a basal diet, but received different supplements, including barley, wheat bran and nonconventional feeds (urea-treated wheat straw, molasses, sugar beet pulp, and cotton seed cake). Five balanced diets enhanced the total yields of milk, fat, protein, and total solids, in 2 cases, significantly. These diets increased total milk yield by 17.7 to 50.2% and decreased supplement feeding costs by 43% compared with the control. However, milk composition remained unaffected. The second trial was conducted on 3 different farms in northern Syria to assess in each farm a low-cost balanced diet on milking ewes (n=15) in comparison to the farmer's control (n=15). The balanced diet was a modification requested by farmers of the best performing diet in the on-station trial. Confirming the first trial's research results, the balanced diet outperformed the control in total yields; for instance, it increased total milk yield by 28 to 40% and raised net income by 30%, without affecting milk composition. Both trials showed that using locally available nonconventional feedstuffs, such as molasses, integrated into balanced dairy sheep diets can decrease feed costs of resource-poor farmers, while enhancing total yields of milk and milk constituents without compromising milk quality components. This will greatly improve the profitability of dairy sheep production in dry areas.

Effects of Management and Genetics on Udder Health and Milk Composition in Dairy Cows

Milk production per cow has increased significantly as a result of breeding, feeding, and other management factors. This study aims to address concerns about udder health risks for low- and high-producing dairy cows. In a 2 x 2 x 2 factorial design, Holstein-Friesian heifers (n = 100) of low or high genetic merit for milk production, milked 2 or 3 times a day, and fed a mixed ration with low or high energy content, were compared during the first 14 wk of lactation. Milk composition and cell counts were determined weekly; quarter milk samples for bacteriology were taken in wk 2, 8, and 14; and teat condition was scored in wk 2, 6, 10, and 14 during the experiment. The experimental factors resulted in substantial differences in milk production between treatment groups (24.1 for low vs. 25.6 kg/d for high genetic merit; 23.3 for 2 times vs. 26.5 kg/d for 3 times daily milking; and 20.9 for low-energy ration vs. 29.0 kg/d for high-energy ration). Ration composition was the most important determining factor for milk production, but did not affect cell counts or intramammary bacterial infections, although cows that received low-energy rations had rougher teat ends than cows receiving high-energy rations. This indicates that high production itself is not a major risk factor for udder health in the first lactation. A higher milking frequency impaired teat condition and improved cell counts in general, but did not clearly influence bacteriological status. High genetic merit was related to higher cell count, more Staphylococcus, and less Bacillus and other environmental pathogens in cultures and did not affect teat condition. The effects of milking frequency and feeding on udder health were similar for cows with high and low genetic merit. Genetic selection on milk production, without taking udder health into account, reduces udder health. As a result, maintaining udder health will require increasing the skills and time of dairy farmers who have to divide their attention to more cows when farm sizes increase, or selection should put more emphasis on udder health traits.