Performance strategies affect mammary gland development in prepubertal heifers

Abstract

In Brazil, the majority of dairy cattle are Holstein × Gyr (H×G). It is unknown whether excessive energy intake negatively affects their mammary development to the same extent as in purebred Holsteins. We hypothesized that mammary development of H×G heifers can be affected by dietary energy supply. We evaluated the effect of different average daily gains (ADG) achieved by feeding different amounts of a standard diet during the growing period on biometric measurements, development of mammary parenchyma (PAR) and mammary fat pad (MFP), and blood hormones. At the outset of this 84-d experiment, H×G heifers (n = 18) weighed 102.2 ± 3.4 kg and were 3 to 4 mo of age. Heifers were randomly assigned to 1 of 3 ADG programs using a completely randomized design. Treatments were high gain (HG; n = 6), where heifers were fed to gain 1 kg/d; low gain (LG; n = 6), where heifers were fed to gain 0.5 kg/d; and maintenance (MA; n = 6), where heifers were fed to gain a minimal amount of weight per day. Heifers were fed varying amounts of a single TMR to support desired BW gains. Over the 84 d, periodic biometric and blood hormone measurements were obtained. On d 84, all heifers were slaughtered and carcass and mammary samples were collected. At the end, HG heifers weighed the most (181 ± 7.5 kg), followed by LG (146 ± 7.5 kg) and MA (107 ± 7.5 kg) heifers. The ADG were near expected values and averaged 0.907, 0.500, and 0.105 ± 0.03 kg/d for HG, LG, and MA, respectively. In addition, body lengths, heart girths, and withers heights were affected by dietary treatment, with MA heifers generally being the smallest and HG heifers generally being the largest. Body condition scores differed by treatment and were highest in HG and lowest in MA heifers; in vivo subcutaneous fat thickness measurement and direct analysis of carcass composition supported this. The HG heifers had the heaviest MFP, followed by LG and then MA heifers. Amount of PAR was highest in LG heifers and was the same for HG and MA heifers. The percentage of udder mass occupied by PAR was lowest in HG heifers, differing from LG and MA heifers. Composition of MFP was not evaluated. Regarding PAR composition, no differences in ash or DM were found. On the other hand, CP concentration of PAR for HG heifers was lower than that for LG heifers, which was lower than that for MA heifers. Regarding the fat content, HG treatment was higher than LG and MA treatment, which did not differ from each other. In PAR, differences in relative abundance of genes related to both stimulation and inhibition of mammary growth were observed to depend on dietary treatment, sampling day, or both. The same can be said for most of the blood hormones that were measured in this experiment. In this experiment, high ADG achieved by feeding different amounts of a standard diet during the growing period negatively affected mammary development.

Feed Intake of Growing Dairy Heifers Raised under Tropical Conditions: A Model Evaluation Using Meta-Analysis

“…Although important studies on the nutrient requirements of crossbred dairy cattle ( Bos taurus × Bos indicus ) have been published [ 96 , 97 , 98 ], data on heifers are still scarce. Since 2016, heifer studies have been performed to better understand the effects of ADG and supply of nutrients on mammary gland development in prepubertal and pubertal crossbred heifers [ 69 , 99 , 100 ]. Moreover, other studies have evaluated the effects of gestation days on the body and conceptus composition and nutrient use by pregnant crossbred cows [ 101 , 102 ].…”

Puberty is a critical window for the impact of diet on mammary gland development in the rabbit

“…Taken together, these data support the evidence that a restricted window of susceptibility, such as puberty, may be sufficient to promote the development of mammary epithelial tissue. Moreover, other authors have produced evidence that overfeeding prepubertal heifers with a high‐energy diet reduced mammary epithelium mass at puberty and negatively affected mammary development by decreasing both MEC proliferation in areas of active ductal expansion and the mass of fat‐free mammary epithelial tissue …”

“…Moreover, other authors have produced evidence that overfeeding prepubertal heifers with a high-energy diet reduced mammary epithelium mass at puberty and negatively affected mammary development by decreasing both MEC proliferation in areas of active ductal expansion and the mass of fat-free mammary epithelial tissue. 47,48 To determine whether the reduction in alveolar epithelial tissue, observed in the present study, was due to either a decreased proliferation or an increased apoptosis of epithelial cells, measurements of Ki67 expression and TUNEL experiments have been used. 34 Although Ki67 is expressed in early pregnancy, we did not observe a significant difference in Ki67 mRNA content between OD and CD-fed rabbit mammary glands.…”

Effect of protein supplement level on the productive and reproductive parameters of replacement heifers managed in intensive grazing systems

“…Considering an ADG between 600 to 700 g/d of the supplemented groups, the absence of effect in the mammary gland development of crossbred animals is different from results observed in other studies. [58] observed that ½ Holstein × Gyr animals with an ADG of 0.9 kg/d showed impaired mammary gland development. This difference may have occurred due to the genetic merit of animals use in both studies.…”